0001708055-21-000094 | 10-Q | XBRL Viewer | Ribbon Communications INC

Print Document View Excel Document

Cover - shares	9 Months Ended
Cover - shares	Sep. 30, 2021	Oct. 21, 2021
Cover [Abstract]
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Sep. 30, 2021
Document Transition Report	false
Entity File Number	001-38267
Entity Registrant Name	RIBBON COMMUNICATIONS INC.
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	82-1669692
Entity Address, Address Line One	6500 Chase Oaks Boulevard, Suite 100,
Entity Address, City or Town	Plano
Entity Address, State or Province	TX
Entity Address, Postal Zip Code	75023
City Area Code	978
Local Phone Number	614-8100
Title of 12(b) Security	Common Stock, par value $0.0001
Trading Symbol	RBBN
Security Exchange Name	NASDAQ
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Common Stock, Shares Outstanding		148,624,895
Entity Central Index Key	0001708055
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2021
Document Fiscal Period Focus	Q3
Amendment Flag	false

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Current assets:
Cash and cash equivalents	$ 101,212	$ 128,428
Restricted cash	2,543	7,269
Accounts receivable, net	235,710	237,738
Inventory	44,789	45,750
Other current assets	34,399	28,461
Total current assets	418,653	447,646
Property and equipment, net	48,557	48,888
Intangible assets, net	367,131	417,356
Goodwill	416,892	416,892
Investments	50,439	115,183
Deferred income taxes	10,673	10,651
Operating lease right-of-use assets	54,446	69,757
Other assets	19,834	20,892
Total assets	1,386,625	1,547,265
Current liabilities:
Current portion of term debt	20,058	15,531
Accounts payable	63,253	63,387
Accrued expenses and other	94,021	134,865
Operating lease liabilities	17,848	17,023
Deferred revenue	89,553	96,824
Total current liabilities	284,733	327,630
Long-term debt, net of current	354,778	369,035
Operating lease liabilities, net of current	58,609	72,614
Deferred revenue, net of current	21,618	26,010
Deferred income taxes	13,477	16,842
Other long-term liabilities	39,862	48,281
Total liabilities	773,077	860,412
Commitments and contingencies
Stockholders' equity:
Preferred stock, $0.01 par value per share; 10,000,000 shares authorized, none issued and outstanding	0	0
Common stock, $0.0001 par value per share; 240,000,000 shares authorized; 148,613,829 shares issued and outstanding at September 30, 2021; 145,425,248 shares issued and outstanding at December 31, 2020	15	15
Additional paid-in capital	1,870,711	1,870,256
Accumulated deficit	(1,259,353)	(1,178,476)
Accumulated other comprehensive income (loss)	2,175	(4,942)
Total stockholders' equity	613,548	686,853
Total liabilities and stockholders' equity	$ 1,386,625	$ 1,547,265

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Sep. 30, 2021	Dec. 31, 2020
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	240,000,000	240,000,000
Common stock, shares issued (in shares)	148,613,829	145,425,248
Common stock, shares outstanding (in shares)	148,613,829	145,425,248

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Revenue:
Total revenue	$ 210,398	$ 231,118	$ 614,380	$ 599,593
Cost of revenue:
Total cost of revenue	90,070	96,164	255,078	250,848
Gross profit	120,328	134,954	359,302	348,745
Operating expenses:
Research and development	49,132	49,113	143,339	143,204
Sales and marketing	36,113	36,898	108,212	101,767
General and administrative	12,148	16,021	40,435	48,320
Amortization of acquired intangible assets	17,221	16,349	50,225	45,352
Acquisition-, disposal- and integration-related	1,955	1,366	4,204	14,607
Restructuring and related	1,767	3,290	10,547	10,726
Total operating expenses	118,336	123,037	356,962	363,976
Income (loss) from operations	1,992	11,917	2,340	(15,231)
Interest expense, net	(2,969)	(6,854)	(11,836)	(15,649)
Other (expense) income, net	(57,702)	407	(65,970)	(2,844)
(Loss) income before income taxes	(58,679)	5,470	(75,466)	(33,724)
Income tax (provision) benefit	(752)	782	(5,411)	(1,445)
Net (loss) income	$ (59,431)	$ 6,252	$ (80,877)	$ (35,169)
(Loss) earnings per share
Basic (in dollars per share)	$ (0.40)	$ 0.04	$ (0.55)	$ (0.26)
Diluted (in dollars per share)	$ (0.40)	$ 0.04	$ (0.55)	$ (0.26)
Weighted average shares used to compute (loss) earnings per share:
Basic (in shares)	148,184	144,948	147,204	136,837
Diluted (in shares)	148,184	151,680	147,204	136,837
Product
Revenue:
Total revenue	$ 111,726	$ 128,926	$ 322,744	$ 325,687
Cost of revenue:
Total cost of revenue	53,494	58,545	144,580	145,103
Service
Revenue:
Total revenue	98,672	102,192	291,636	273,906
Cost of revenue:
Total cost of revenue	$ 36,576	$ 37,619	$ 110,498	$ 105,745

Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Statement of Comprehensive Income [Abstract]
Net (loss) income	$ (59,431)	$ 6,252	$ (80,877)	$ (35,169)
Other comprehensive income (loss), net of tax:
Unrealized gain (loss) on interest rate swap	860	640	7,324	(12,857)
Foreign currency translation adjustments	193	184	(207)	1,031
Other comprehensive income (loss), net of tax	1,053	824	7,117	(11,826)
Comprehensive (loss) income, net of tax	$ (58,378)	$ 7,076	$ (73,760)	$ (46,995)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04(22))
-URI http://asc.fasb.org/extlink&oid=120399700&loc=SL114874048-224260

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 4
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22595-107794

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 220
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04(18))
-URI http://asc.fasb.org/extlink&oid=120400993&loc=SL114874131-224263

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 65
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123482062&loc=SL123482106-238011

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=124431353&loc=SL124452729-227067

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 8: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(20))
-URI http://asc.fasb.org/extlink&oid=123367319&loc=SL114868664-224227

Reference 9: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-URI http://asc.fasb.org/extlink&oid=123570139&loc=d3e3602-108585

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22499-107794

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(iii)(A))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(i))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(i))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 15: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22663-107794

Reference 16: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iv))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 17: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(4)(ii))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 18: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 28
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123596393&loc=d3e14064-108612

Reference 19: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22583-107794

Reference 20: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(g)(1)(ii))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 21: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 260
-SubTopic 10
-Section 45
-Paragraph 60B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=125511455&loc=SL5780133-109256

Reference 22: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

Reference 23: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22658-107794

Reference 24: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669619-108580

Reference 25: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

Reference 26: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 27: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 11
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124431687&loc=d3e22694-107794

Reference 28: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 20
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=109222650&loc=SL51721683-107760

Reference 29: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 1B
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=124509347&loc=SL7669625-108580

Reference 30: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 31: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1A
-Subparagraph (SX 210.13-01(a)(5))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442526-122756

Reference 32: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(B))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 33: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section S99
-Paragraph 1B
-Subparagraph (SX 210.13-02(a)(4)(iii)(A))
-URI http://asc.fasb.org/extlink&oid=124359900&loc=SL124442552-122756

Reference 34: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8906-108599

Reference 35: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

+ Details

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive (loss) income	ECI Telecom Group Ltd.	ECI Telecom Group Ltd. Common stock	ECI Telecom Group Ltd. Additional paid-in capital	Anova Data, Inc.	Anova Data, Inc. Common stock	Anova Data, Inc. Additional paid-in capital
Beginning balance (in shares) at Dec. 31, 2019		110,471,995
Beginning balance at Dec. 31, 2019	$ 483,255	$ 11	$ 1,747,784	$ (1,267,067)	$ 2,527
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)		16,128
Exercise of stock options	29		29
Vesting of restricted stock awards and units (in shares)		1,971,730
Vesting of restricted stock awards and units	1	$ 1
Vesting of performance-based stock awards (in shares)		323,752
Shares of restricted stock returned to the Company under net share settlements to satisfy tax withholding obligations (in shares)		(373,272)
Shares of restricted stock returned to the Company under net share settlements to satisfy tax withholding obligations	(1,196)		(1,196)
Shares issued as consideration in connection with acquisition (in shares)							32,500,000			316,551
Shares issued as consideration in connection with acquisition						$ 108,550	$ 3	$ 108,547	$ 1,630		$ 1,630
Stock-based compensation expense	10,167		10,167
Other comprehensive income (loss)	(11,826)				(11,826)
Net (loss) income	(35,169)			(35,169)
Ending balance (in shares) at Sep. 30, 2020		145,226,884
Ending balance at Sep. 30, 2020	555,441	$ 15	1,866,961	(1,302,236)	(9,299)
Beginning balance (in shares) at Jun. 30, 2020		144,856,764
Beginning balance at Jun. 30, 2020	544,777	$ 14	1,863,374	(1,308,488)	(10,123)
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)		2,926
Exercise of stock options	6		6
Vesting of restricted stock awards and units (in shares)		454,178
Vesting of restricted stock awards and units	1	$ 1
Vesting of performance-based stock awards (in shares)		7,886
Shares of restricted stock returned to the Company under net share settlements to satisfy tax withholding obligations (in shares)		(94,870)
Shares of restricted stock returned to the Company under net share settlements to satisfy tax withholding obligations	(388)		(388)
Stock-based compensation expense	3,969		3,969
Other comprehensive income (loss)	824				824
Net (loss) income	6,252			6,252
Ending balance (in shares) at Sep. 30, 2020		145,226,884
Ending balance at Sep. 30, 2020	$ 555,441	$ 15	1,866,961	(1,302,236)	(9,299)
Beginning balance (in shares) at Dec. 31, 2020	145,425,248	145,425,248
Beginning balance at Dec. 31, 2020	$ 686,853	$ 15	1,870,256	(1,178,476)	(4,942)
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)	13,815	13,815
Exercise of stock options	$ 24		24
Vesting of restricted stock awards and units (in shares)		3,320,644
Vesting of performance-based stock awards (in shares)		1,525,681
Shares of restricted stock returned to the Company under net share settlements to satisfy tax withholding obligations (in shares)		(1,671,559)
Shares of restricted stock returned to the Company under net share settlements to satisfy tax withholding obligations	(13,980)		(13,980)
Stock-based compensation expense	14,411		14,411
Other comprehensive income (loss)	7,117				7,117
Net (loss) income	$ (80,877)			(80,877)
Ending balance (in shares) at Sep. 30, 2021	148,613,829	148,613,829
Ending balance at Sep. 30, 2021	$ 613,548	$ 15	1,870,711	(1,259,353)	2,175
Beginning balance (in shares) at Jun. 30, 2021		148,057,301
Beginning balance at Jun. 30, 2021	669,281	$ 15	1,868,066	(1,199,922)	1,122
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)		213
Vesting of restricted stock awards and units (in shares)		855,440
Shares of restricted stock returned to the Company under net share settlements to satisfy tax withholding obligations (in shares)		(299,125)
Shares of restricted stock returned to the Company under net share settlements to satisfy tax withholding obligations	(1,916)		(1,916)
Stock-based compensation expense	4,561		4,561
Other comprehensive income (loss)	1,053				1,053
Net (loss) income	$ (59,431)			(59,431)
Ending balance (in shares) at Sep. 30, 2021	148,613,829	148,613,829
Ending balance at Sep. 30, 2021	$ 613,548	$ 15	$ 1,870,711	$ (1,259,353)	$ 2,175

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash flows from operating activities:
Net loss	$ (59,431)	$ 6,252	$ (80,877)	$ (35,169)
Adjustments to reconcile net loss to cash flows provided by operating activities:
Depreciation and amortization of property and equipment			12,684	12,754
Amortization of intangible assets	17,221	16,349	50,225	45,352
Amortization of debt issuance costs			4,227	4,915
Stock-based compensation			14,411	10,167
Deferred income taxes			(3,295)	(2,455)
Gain on sale of business			(2,772)	0
Decrease in fair value of investments			64,745	0
Reduction in deferred purchase consideration			0	(69)
Foreign currency exchange losses			3,235	3,162
Changes in operating assets and liabilities:
Accounts receivable			1,892	42,489
Inventory			253	6,285
Other operating assets			11,303	36,416
Accounts payable			2,194	(54,489)
Accrued expenses and other long-term liabilities			(58,661)	10,143
Deferred revenue			(11,665)	(14,253)
Net cash provided by operating activities			7,899	65,248
Cash flows from investing activities:
Purchases of property and equipment			(14,279)	(18,685)
Business acquisitions, net of cash acquired			0	(346,852)
Proceeds from sale of business			2,944	0
Proceeds from the sale of fixed assets			0	43,500
Net cash used in investing activities			(11,335)	(322,037)
Cash flows from financing activities:
Borrowings under revolving line of credit			0	615
Principal payments on revolving line of credit			0	(8,615)
Proceeds from issuance of term debt			74,625	478,500
Principal payments of term debt			(87,161)	(131,279)
Principal payments of finance leases			(736)	(971)
Payment of debt issuance costs			(789)	(14,065)
Proceeds from the exercise of stock options			24	29
Payment of tax withholding obligations related to net share settlements of restricted stock awards			(13,980)	(1,196)
Net cash (used in) provided by financing activities			(28,017)	323,018
Effect of exchange rate changes on cash, cash equivalents and restricted cash			(489)	24
Net (decrease) increase in cash, cash equivalents and restricted cash			(31,942)	66,253
Cash, cash equivalents and restricted cash, beginning of year			135,697	44,643	$ 44,643
Cash, cash equivalents and restricted cash, end of period	103,755	110,896	103,755	110,896	$ 135,697
Supplemental disclosure of cash flow information:
Interest paid			11,410	10,845
Income taxes paid			11,944	6,652
Income tax refunds received			983	196
Supplemental disclosure of non-cash investing activities:
Capital expenditures incurred, but not yet paid			1,807	4,111
Acquisition purchase consideration - deferred payments	$ 0	$ 1,630	0	1,630
Common stock issued as purchase consideration			0	108,550
Supplemental disclosure of non-cash financing activities:
Total fair value of restricted stock awards, restricted stock units and performance-based stock units on date vested			$ 38,879	$ 5,551

BASIS OF PRESENTATION

9 Months Ended

Sep. 30, 2021

Accounting Policies [Abstract]

BASIS OF PRESENTATION

Business

Ribbon Communications Inc. ("Ribbon" or the "Company") is a leading global provider of communications technology to service providers and enterprises. The Company provides a broad range of software and high-performance hardware products, solutions and services that enable the secure delivery of data and voice communications for residential consumers and for small, medium, and large enterprises and industry verticals such as finance, education, government, utilities and transportation. Ribbon's mission is to create a recognized global technology leader providing cloud-centric solutions that enable the secure exchange of information, with unparalleled scale, performance and elasticity. The Company is headquartered in Plano, Texas, and has a global presence with research and development, or sales and support locations in over thirty-five countries around the world.

Basis of Presentation

In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting only of normal recurring items, necessary for their fair presentation with accounting principles generally accepted in the United States of America ("GAAP") and with the rules and regulations of the U.S. Securities and Exchange Commission ("SEC").

On December 1, 2020 (the "Kandy Sale Date"), the Company completed the sale of its cloud-based enterprise service business (the "Kandy Communications Business") to AVCT and, accordingly, the revenue and expenses of the Kandy Communications Business are excluded from the Company's condensed consolidated financial statements for the three and nine months ended September 30, 2021.

On March 3, 2020 (the "ECI Acquisition Date"), a subsidiary of the Company merged (the "ECI Acquisition") with ECI Telecom Group Ltd ("ECI"). The financial results of ECI are included in the Company's condensed consolidated financial statements for the period subsequent to the ECI Acquisition Date.

Interim results are not necessarily indicative of results for a full year or any future interim period. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Company's Annual Report on Form 10-K for the year ended December 31, 2020 (the "Annual Report"), which was filed with the SEC on February 26, 2021.

Operating Segments

The Company's chief operating decision maker (the "CODM") is its President and Chief Executive Officer. Effective in the fourth quarter of 2020 and in connection with the ECI Acquisition, the CODM began to assess the Company's performance based on the performance of two separate organizations within Ribbon: the Cloud and Edge segment ("Cloud and Edge") and the IP Optical Networks segment ("IP Optical Networks"). Financial information for the IP Optical Networks segment included in the Company's financial results for the nine months ended September 30, 2020 is for the period subsequent to the ECI Acquisition Date through September 30, 2020.

Reclassifications

In the fourth quarter of 2020, the Company reclassified amounts recorded for amortization of acquired intangible assets in prior presentations from Cost of revenue - product and Sales and marketing to a separate line included in operating expenses in the condensed consolidated statements of operations, as management believes this presentation enhances the comparability of the Company's financial statements with industry peers. These reclassifications also did not impact the condensed consolidated balance sheets or statements of cash flows for any historical periods. The Company did not reclassify depreciation of property and equipment related to production activities from cost of revenue to other accounts.

These reclassifications for the three and nine months ended September 30, 2020 were as follows (in thousands):


	Three months ended September 30, 2020			Nine months ended September 30, 2020
		Prior presentation		Amounts reclassified		Revised presentation		Prior presentation		Amounts reclassified		Revised presentation
Product revenue		$	128,926			$	128,926	$	325,687			$	325,687
Service revenue		102,192				102,192		273,906				273,906
Total revenue		231,118		—		231,118		599,593		—		599,593
Cost of revenue - product		70,188		(11,643)		58,545		176,650		(31,547)		145,103
Cost of revenue - service		37,619				37,619		105,745				105,745
Total cost of revenue		107,807		(11,643)		96,164		282,395		(31,547)		250,848
Total gross profit		123,311		11,643		134,954		317,198		31,547		348,745
Research and development		49,113				49,113		143,204				143,204
Sales and marketing		41,604		(4,706)		36,898		115,572		(13,805)		101,767
General and administrative		16,021				16,021		48,320				48,320
Amortization of acquired intangible assets		—		16,349		16,349		—		45,352		45,352

Acquisition-, disposal- and integration-related		1,366				1,366		14,607				14,607
Restructuring and related		3,290				3,290		10,726				10,726
Total operating expenses		111,394		11,643		123,037		332,429		31,547		363,976
Income (loss) from operations		$	11,917	$	—	$	11,917	$	(15,231)	$	—	$	(15,231)

Certain reclassifications, not affecting previously reported net income (loss), have been made to the previously issued financial statements to conform to the current period presentation.

Significant Accounting Policies

The Company's significant accounting policies are disclosed in Note 2 to the Consolidated Financial Statements included in the Annual Report. There were no material changes to the significant accounting policies during the three months ended September 30, 2021 with the exception of the Company's election to account for its equity investment in AVCT using the fair value option in connection with the September 8, 2021 conversion of the debentures received by the Company as consideration for the sale of its Kandy Communications Business (the "Debentures Conversion") (see Note 3).

Principles of Consolidation

The condensed consolidated financial statements include the accounts of Ribbon and its wholly-owned subsidiaries. Intercompany transactions and balances have been eliminated in consolidation.

Use of Estimates and Judgments

The preparation of financial statements in conformity with GAAP requires Ribbon to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and judgments relied upon in preparing these condensed consolidated financial statements include accounting for business combinations, revenue recognition for multiple element arrangements, inventory valuations, assumptions used to determine the fair value of stock-based compensation, intangible asset and goodwill valuations, including impairments, legal contingencies and recoverability of Ribbon's net deferred tax assets and the related valuation allowances. Ribbon regularly assesses these estimates and records changes in estimates in the period in which they become known. Ribbon bases its estimates on historical experience and various other assumptions that it believes to be reasonable under the circumstances. Actual results could differ from those estimates.

Restricted Cash

The Company classifies as restricted cash all cash pledged as collateral to secure long-term obligations and all cash whose use is otherwise limited by contractual provisions.

At September 30, 2021, the Company had $2.5 million of restricted cash, representing restricted short-term bank deposits pledged to secure certain performance and financial bonds as security for the Company's obligations under tenders, contracts and to one of its main subcontractors.

At December 31, 2020, the Company had $7.3 million of restricted cash, comprised of $4.6 million restricted in connection with a tax payment on certain fixed assets formerly held by ECI that were sold in connection with the ECI Acquisition, and $2.7 million of restricted short-term bank deposits pledged to secure certain performance and financial bonds as security for the Company's obligations under tenders, contracts and to one of its main subcontractors.

Transfers of Financial Assets

The Company maintains customer receivables factoring agreements with a number of financial institutions primarily for IP Optical Networks sales outside of the United States. Under the terms of these agreements, the Company may transfer receivables to the financial institutions, on a non-recourse basis, provided that the financial institutions approve the receivables in advance. The Company maintains credit insurance policies from major insurance providers or obtains letters of credit from the customers for a majority of its factored trade receivables. The Company accounts for the factoring of its financial assets as a sale of the assets and records the factoring fees, when incurred, as a component of interest expense in the condensed consolidated statements of operations, and the proceeds from the sales of receivables are included in cash from operating activities in the condensed consolidated statements of cash flows. During the three and nine months ended September 30, 2021, the Company received $24.8 million and $88.0 million, respectively, of cash from the sale of certain accounts receivable and recorded $0.2 million and $0.6 million, respectively, of interest expense in connection with these transactions. During the three and nine months ended September 30, 2020, the Company received $35.3 million and $81.1 million, respectively, of cash from the sale of certain accounts receivable and recorded $0.3 million and $0.7 million, respectively, of interest expense in connection with these transactions.

Fair Value of Financial Instruments and Fair Value Hierarchy

The carrying amounts of the Company's financial instruments approximate their fair values and include cash equivalents, accounts receivable, borrowings under a revolving credit facility, accounts payable and long-term debt.

Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. The three-tier fair value hierarchy is based on the level of independent, objective evidence surrounding the inputs used to measure fair value. A financial instrument's categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The fair value hierarchy is as follows:

Level 1. Level 1 applies to assets or liabilities for which there are quoted prices in active markets for identical assets or liabilities.

Level 2. Level 2 applies to assets or liabilities for which there are inputs that are directly or indirectly observable in the marketplace, such as quoted prices for similar assets or liabilities in active markets or quoted prices for identical assets or liabilities in markets with insufficient volume or infrequent transactions (less active markets).

Level 3. Level 3 applies to assets or liabilities for which there are unobservable inputs to the valuation methodology that are significant to the measurement of the fair value of the assets or liabilities.

Fair Value Option - Investment in AVCT

In connection with the Debentures Conversion, the Company elected to use the fair value option to account for its equity investment in AVCT as permitted under Accounting Standards Codification ("ASC") 825, Financial Instruments ("ASC 825"). ASC 820, Fair Value Measurement ("ASC 820") provides the fair value framework for valuing such investments. In accordance with ASC 820, the Company is recording the investment in AVCT at fair value, with changes in fair value recorded as a component of Other (expense) income, net, in the condensed consolidated statements of operations.

Recent Accounting Pronouncements

The Financial Accounting Standards Board ("FASB") issued the following accounting pronouncement which became effective for the Company in 2021, and which did not have a material impact on its condensed consolidated financial statements:

In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes ("ASU 2019-12"), which modifies ASC 740 to simplify the accounting for income taxes. ASU 2019-12 addresses the accounting for hybrid tax regimes, tax basis step-up in goodwill obtained in a transaction that is not a business combination, separate financial statements of legal entities not subject to tax, intraperiod tax allocation exception to incremental approach, ownership changes in investments - changes from a subsidiary to an equity method investment, ownership changes in investments - changes from an equity method investment to a subsidiary, interim period accounting for enacted changes in tax law and year-to-date loss limitation in interim period tax accounting.

The FASB issued the following accounting pronouncement, which the Company does not believe will have a material impact on its condensed consolidated financial statements upon adoption:

In January 2021, the FASB issued ASU 2021-01, Reference Rate Reform (Topic 848): Scope ("ASU 2021-01"), which refines the scope of Accounting Standards Codification 848, Reference Rate Reform ("ASC 848") and clarifies some of its guidance as part of the FASB's monitoring of global reference rate reform activities. ASU 2021-01 permits entities to elect certain optional expedients and exceptions when accounting for derivative contracts and certain hedging relationships affected by changes in the interest rates used for discounting cash flows, for computing variation margin settlements, and for calculating price alignment interest in connection with reference rate reform activities under way in global financial markets (the "discounting transition"). ASU 2021-01 is effective for the Company prospectively in any period through December 31, 2022 that a modification is made to the terms of the derivatives affected by the discounting transition.

BUSINESS ACQUISITION

9 Months Ended

Sep. 30, 2021

Business Combination and Asset Acquisition [Abstract]

BUSINESS ACQUISITION

On the ECI Acquisition Date, Ribbon completed its previously announced merger transaction with ECI in accordance with the terms of the Agreement and Plan of Merger, dated as of November 14, 2019, by and among Ribbon, ECI, an indirect wholly-owned subsidiary of Ribbon ("Merger Sub"), Ribbon Communications Israel Ltd. and ECI Holding (Hungary) kft, pursuant to which Merger Sub merged with and into ECI, with ECI surviving such merger as a wholly-owned subsidiary of Ribbon. Prior to the ECI Acquisition Date, ECI was a privately-held global provider of end-to-end packet-optical transport and software-defined networking ("SDN") and network function virtualization ("NFV") solutions for service providers, enterprises and data center operators.

As consideration for the ECI Acquisition, Ribbon issued the ECI shareholders and certain others 32.5 million shares of Ribbon common stock with a fair value of $108.6 million (the "Stock Consideration") and paid $322.5 million of cash (the "Cash Consideration"), comprised of $183.3 million to repay ECI's outstanding debt, including both principal and interest, and $139.2 million paid to ECI's selling shareholders. In addition, ECI shareholders received $33.4 million from the sale of certain of ECI's real estate assets. Cash Consideration was financed through cash on hand and committed debt financing consisting of a new $400 million term loan facility and new $100 million revolving credit facility, which was undrawn at the ECI Acquisition Date.

The ECI Acquisition has been accounted for as a business combination and the financial results of ECI have been included

in the Company's condensed consolidated financial statements for the periods subsequent to the ECI Acquisition. The Company's financial results for the three months ended September 30, 2020 included $77.6 million of revenue and $11.2 million of net loss attributable to ECI. The Company's financial results for the nine months ended September 30, 2020 included $171.1 million of revenue and $31.9 million of net loss attributable to ECI for the period subsequent to the ECI Acquisition.

The Company finalized the valuation of acquired assets, identifiable intangible assets and certain assumed liabilities in the fourth quarter of 2020. A summary of the allocation of the purchase consideration for ECI is as follows (in thousands):


Fair value of consideration transferred:
Cash consideration:
Repayment of ECI outstanding debt obligations	$	183,266


Cash paid to selling shareholders	139,244
Payment to selling shareholders from sale of ECI real estate assets	33,400
Less cash and restricted cash acquired	(9,058)
Net cash consideration	346,852

Fair value of Ribbon stock issued	108,550

Fair value of total consideration	$	455,402

Fair value of assets acquired and liabilities assumed:
Current assets, net of cash and restricted cash acquired	$	120,203
Property and equipment	54,913
Intangible assets:
In-process research and development	34,000
Developed technology	111,900
Customer relationships	116,000
Trade names	3,000
Goodwill	191,996


Other noncurrent assets	37,528

Deferred revenue	(4,369)
Other current liabilities	(146,618)

Deferred revenue, net of current	(3,726)
Deferred tax liability	(13,308)
Other long-term liabilities	(46,117)
	$	455,402

The valuation of the acquired intangible assets is inherently subjective and relies on significant unobservable inputs. The Company used an income approach to value the acquired in-process research and development, developed technology, customer relationships and trade name intangible assets. The valuation for each of these intangible assets was based on estimated projections of expected cash flows to be generated by the assets, discounted to the present value at discount rates commensurate with perceived risk. The valuation assumptions take into consideration the Company's estimates of customer attrition, technology obsolescence and revenue growth projections. The Company is amortizing the identifiable intangible assets arising from the ECI Acquisition in relation to the expected cash flows from the individual intangible assets over their respective useful lives, which have a weighted average life of 12.38 years (see Note 6). Goodwill results from assets that are not separately identifiable as part of the transaction and is not deductible for tax purposes.

Pro Forma Results

The following unaudited pro forma information presents the condensed combined results of operations of Ribbon and ECI for the three and nine months ended September 30, 2020 as if the ECI Acquisition had been completed on January 1, 2019, with adjustments to give effect to pro forma events that are directly attributable to the ECI Acquisition. These pro forma adjustments include an increase in research and development expense related to the conformance of ECI's cost capitalization policy to

Ribbon's, additional amortization expense for the acquired identifiable intangible assets, a decrease in historical ECI interest expense reflecting the extinguishment of certain of ECI's debt as a result of the ECI Acquisition, and an increase in interest expense reflecting the new debt entered into by the Company in connection with the ECI Acquisition. Pro forma adjustments also include the elimination of acquisition-, disposal- and integration-related expenses directly attributable to the acquisition from the three and nine months ended September 30, 2020 and inclusion of such costs in the comparable prior year periods.

The unaudited pro forma results do not reflect any operating efficiencies or potential cost savings that may result from the consolidation of the operations of Ribbon and ECI. Accordingly, these unaudited pro forma results are presented for illustrative purposes and are not intended to represent or be indicative of the actual results of operations of the combined company that would have been achieved had the ECI Acquisition occurred at January 1, 2019, nor are they intended to represent or be indicative of future results of operations (in thousands, except per share amounts):


			4
	Three months ended			Nine months ended
	September 30, 2020			September 30, 2020
Revenue	$	231,118		$	624,800
Net income (loss)	$	7,036		$	(41,345)
Diluted earnings (loss) per share	$	0.05		$	(0.29)

Acquisition-, Disposal- and Integration-Related Expenses

Acquisition-related expenses include those expenses related to acquisitions that would otherwise not have been incurred by the Company, including professional and services fees, such as legal, audit, consulting, paying agent and other fees. Disposal-related expenses are professional and services fees related to disposals of subsidiaries or portions of the business. Integration-related expenses represent incremental costs related to combining the Company and its business acquisitions, such as third-party consulting and other third-party services related to merging the previously separate companies' systems and processes. The acquisition-related expenses in the three and nine months ended September 30, 2020 primarily related to the ECI Acquisition. The disposal-related expenses in the nine months ended September 30, 2021 relate to the Kandy Sale (as defined below).

The Company's acquisition-, disposal- and integration-related expenses for the three and nine months ended September 30, 2021 and 2020 were as follows (in thousands):



	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Professional and services fees (acquisition-related)	$	13	$	1,003	$	156	$	14,017

Professional and services fees (disposal-related)	—		—		241		—
Integration-related expenses	1,942		363		3,807		590
	$	1,955	$	1,366	$	4,204	$	14,607

SALE OF KANDY COMMUNICATIONS BUSINESS AND INVESTMENT IN AVCT	9 Months Ended
	Sep. 30, 2021
Discontinued Operations and Disposal Groups [Abstract]
SALE OF KANDY COMMUNICATIONS BUSINESS AND INVESTMENT IN AVCT	SALE OF KANDY COMMUNICATIONS BUSINESS AND INVESTMENT IN AVCT On August 5, 2020, the Company announced that it had entered into a definitive agreement (as amended, the "Kandy Purchase Agreement") with AVCT to sell the Kandy Communications Business. Under the Kandy Purchase Agreement, AVCT agreed to purchase the assets and assume certain liabilities associated with the Kandy Communications Business, as well as all of the outstanding interests in Kandy Communications LLC, a subsidiary of the Company (the "Kandy Sale"). On December 1, 2020, the Company completed the Kandy Sale. The assets acquired and liabilities assumed by AVCT in connection with the Kandy Sale were primarily comprised of accounts receivable, property and equipment, trade accounts payable and employee-related accruals. As consideration, AVCT paid Ribbon $45.0 million, subject to certain adjustments, in the form of units of AVCT's securities (the "AVCT Units"), with each AVCT Unit consisting of: $1,000 in principal amount of AVCT’s Series A-1 convertible debentures (the “Debentures”); and (ii) one warrant to purchase 100 shares of AVCT common stock, $0.0001 par value (the “Warrants”), as consideration for the Kandy Sale. The Company received 43,778 AVCT Units as consideration on the Kandy Sale Date. The Debentures bore interest at a rate of 10% per annum, which was added to the principal amount of the Debentures. The entire principal amount of each Debenture, together with accrued and unpaid interest thereon, was due and payable on the earlier of the May 1, 2023 maturity date or the occurrence of a Change in Control as defined in the Kandy Purchase Agreement. Each Debenture was convertible, in whole or in part, at any time at the Company's option into that number of shares of AVCT common stock, calculated by dividing the principal amount being converted, together with all accrued and unpaid interest thereon, by the applicable conversion price, which initially was $3.45 per share. The Debentures were subject to mandatory conversion if the AVCT stock price was at or above $6.00 per share for 40 trading days in any 60 consecutive trading day period, subject to the satisfaction of certain other conditions. The conversion price was subject to customary adjustments including, but not limited to, stock dividends, stock splits and reclassifications. As of February 19, 2021, the stock price had traded above $6.00 for 40 days within a 60 consecutive trading day period, and accordingly, on September 8, 2021 (the "Debenture Conversion Date"), upon the completion of customary regulatory filings by AVCT, the Debentures were converted into 13,700,421 shares of AVCT common stock (the "Debenture Shares"). The Warrants were independent of the Debentures and entitle the Company to purchase 4,377,800 shares of AVCT common stock at an exercise price of $0.01 per share. The Warrants expire on December 1, 2025, and were immediately exercisable on the Kandy Sale Date. The Company had not exercised any of the Warrants as of September 30, 2021. The Company was also subject to a lock-up provision which limited the Company's ability to sell any shares of the AVCT common stock underlying the Debentures and the Warrants prior to June 1, 2021 (the "Lock-Up Period"), except in certain transactions. The Company determined that the AVCT Units had a fair value of $84.9 million at the Kandy Sale Date, comprised of the Debentures with a fair value of $66.3 million and the Warrants with a fair value of $18.6 million. The value of the net assets sold to AVCT totaled $1.3 million, resulting in a gain on the sale of $83.6 million. The Company calculated the fair value of the Debentures using a Lattice-based valuation approach, which utilizes a binomial tree to model the different paths the price of AVCT's common stock might take over the Debentures' life by using assumptions regarding the stock price volatility and risk-free interest rate. These results were then used to calculate the fair value of the Debentures at each measurement date prior to the Debenture Conversion Date. The Company used the Black-Scholes valuation model for estimating the fair value of the Warrants at each measurement date. The fair value of the Warrants was affected by AVCT's stock price as well as valuation assumptions, including the volatility of AVCT's stock price, expected term of the option, risk-free interest rate and expected dividends. Both the Lattice and Black-Scholes valuation models are based on available market data, giving consideration to all of the rights and obligations of each instrument and precluding the use of "blockage" discounts or premiums in determining the fair value of a large block of financial instruments. After the expiration of the Lock-Up Period and prior to the Debenture Conversion Date, the Company valued the AVCT Units at each measurement date by multiplying the closing stock price of AVCT common stock by the number of shares upon conversion of the Debentures and Warrants. At September 30, 2021, the Company valued the Debenture Shares and Warrants by multiplying the closing stock price of AVCT common stock by the number of Debenture Shares and Warrants (collectively, the "AVCT Investment") it held. At September 30, 2021, the aggregate fair value of the AVCT Investment was $50.4 million, comprised of $38.2 million for the Debenture Shares and $12.2 million for the Warrants. At December 31, 2020, the aggregate fair value of the AVCT Units was $115.2 million. The Company recorded losses of $56.5 million and $68.3 million in the three and nine months ended September 30, 2021, respectively, arising from the change in the aggregate fair value of the AVCT Investment. These amounts are included as components of Other income (expense), net, in the Company's condensed consolidated statements of operations. The Company recorded $0.9 million and $3.6 million of interest income in the three and nine months ended September 30, 2021, respectively, which was added to the principal amount of the Debentures prior to the Debenture Conversion Date, and which is included in Interest expense, net, in the condensed consolidated statements of operations. The fair value of the AVCT Investment at September 30, 2021 and the fair values of the Debentures and Warrants at December 31, 2021 are reported as Investments in the Company's condensed consolidated balance sheets. The AVCT Investment is classified as a Level 1 fair value measurement at September 30, 2021 and the Debentures and Warrants are classified as Level 2 fair value measurements within the fair value hierarchy at December 31, 2020 (see Note 1). The Company evaluated the nature of its investment in AVCT for the period from the Debenture Conversion Date to September 30, 2021 and determined that it represented an approximate 25% equity interest in AVCT. The Company determined that it is not the primary beneficiary of AVCT as it does not have the power to direct the activities that most significantly impact the AVCT Investment's economic performance and therefore concluded that, although it did have significant influence arising from the AVCT Investment, it did not have a controlling financial interest that would require consolidation as of September 30, 2021.

EARNINGS (LOSS) PER SHARE

9 Months Ended

Sep. 30, 2021

Earnings Per Share [Abstract]

EARNINGS (LOSS) PER SHARE

Basic earnings (loss) per share is computed by dividing net income (loss) by the weighted average number of shares outstanding during the period. For periods in which the Company reports net income, diluted net earnings per share is determined by using the weighted average number of common and dilutive common equivalent shares outstanding during the period, unless the effect is antidilutive.

The calculations of shares used to compute earnings (loss) per share were as follows (in thousands):


	Three months ended		Nine months ended
	September 30, 2021	September 30, 2020	September 30, 2021	September 30, 2020
Weighted average shares outstanding - basic	148,184	144,948	147,204	136,837
Potential dilutive common shares	—	6,732	—	—
Weighted average shares outstanding - diluted	148,184	151,680	147,204	136,837

Options to purchase the Company's common stock and unvested restricted and performance-based stock units aggregating 10.9 million shares have not been included in the computation of diluted earnings per share for the three and nine months ended September 30, 2021 because their effect would have been antidilutive. Options to purchase the Company's common stock aggregating 0.2 million shares have not been included in the computation of diluted earnings per share for the three months ended September 30, 2020 because their effect would have been antidilutive. Options to purchase the Company's common stock and unvested shares of restricted and performance-based stock and stock units aggregating 13.5 million shares have not been included in the computation of diluted loss per share have not been included in the computation of diluted loss per share for the nine months ended September 30, 2020 because their effective would have been antidilutive.

INVENTORY

9 Months Ended

Sep. 30, 2021

Inventory Disclosure [Abstract]

INVENTORY

Inventory at September 30, 2021 and December 31, 2020 consisted of the following (in thousands):


	September 30, 2021		December 31, 2020

On-hand final assemblies and finished goods inventories	$	48,176	$	46,921
Deferred cost of goods sold	1,467		1,165
	49,643		48,086
Less noncurrent portion (included in other assets)	(4,854)		(2,336)
Current portion	$	44,789	$	45,750

INTANGIBLE ASSETS AND GOODWILL

9 Months Ended

Sep. 30, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

INTANGIBLE ASSETS AND GOODWILL

The Company's intangible assets at September 30, 2021 and December 31, 2020 consisted of the following (in thousands):


September 30, 2021	Weighted average amortization period (years)	Cost		Accumulated amortization		Net carrying value
In-process research and development	*	$	34,000	$	—	$	34,000

Developed technology	7.93	306,380		172,485		133,895
Customer relationships	11.86	268,140		70,464		197,676
Trade names	3.88	5,000		3,440		1,560

Internal use software	3.00	730		730		—
	9.17	$	614,250	$	247,119	$	367,131


December 31, 2020	Weighted average amortization period (years)	Cost		Accumulated amortization		Net carrying value
In-process research and development	*	$	34,000	$	—	$	34,000

Developed technology	7.93	306,380		143,050		163,330
Customer relationships	11.86	268,140		50,627		217,513
Trade names	3.88	5,000		2,487		2,513

Internal use software	3.00	730		730		—
	9.17	$	614,250	$	196,894	$	417,356

* An in-process research and development intangible asset has an indefinite life until the product is generally available, at which time such asset is typically reclassified to developed technology.

Estimated future amortization expense for the Company's intangible assets at September 30, 2021 was as follows (in thousands):


Years ending December 31,
Remainder of 2021	$	16,401
2022	60,449
2023	53,966
2024	46,899
2025	40,338
2026	36,489
Thereafter	112,589
	$	367,131

There were no changes to the carrying value of the Company's goodwill in the nine months ended September 30, 2021. The changes in the carrying value of the Company's goodwill in the nine months ended September 30, 2020 were as follows (in thousands):


	Cloud and Edge		IP Optical Networks		Total




Balance at January 1, 2020*	$	224,896	$	—	$	224,896
Acquisition of ECI	—		191,996		191,996
Balance at September 30, 2020	$	224,896	$	191,996	$	416,892

* Balance is presented net of accumulated impairment losses of $167.4 million for the Cloud and Edge segment.

The components of goodwill at September 30, 2021 and 2020 were as follows (in thousands):


	Cloud and Edge		IP Optical Networks		Total
Balance at September 30, 2021
Goodwill	$	392,302	$	191,996	$	584,298
Accumulated impairment losses	(167,406)		—		(167,406)
	$	224,896	$	191,996	$	416,892
Balance at September 30, 2020
Goodwill	$	392,302	$	191,996	$	584,298
Accumulated impairment losses	(167,406)		—		(167,406)
	$	224,896	$	191,996	$	416,892

ACCRUED EXPENSES AND OTHER

9 Months Ended

Sep. 30, 2021

Payables and Accruals [Abstract]

ACCRUED EXPENSES AND OTHER

Accrued expenses at September 30, 2021 and December 31, 2020 consisted of the following (in thousands):


	September 30, 2021		December 31, 2020
Employee compensation and related costs	$	38,730	$	66,039



Other	55,291		68,826
	$	94,021	$	134,865

WARRANTY ACCRUALS

9 Months Ended

Sep. 30, 2021

Guarantees and Product Warranties [Abstract]

WARRANTY ACCRUALS

The changes in the Company's accrual balance in the nine months ended September 30, 2021 were as follows (in thousands):






Balance at January 1, 2021	$	14,855

Current period provisions	1,925
Settlements	(4,095)
Balance at September 30, 2021	$	12,685

Of the amounts recorded at September 30, 2021 and December 31, 2020, $5.8 million and $6.5 million, respectively, were current and included as components of Accrued expenses and other, and $6.9 million and $8.4 million, respectively, were long-term and included as components of Other long-term liabilities in the Company's condensed consolidated balance sheets.

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVES

9 Months Ended

Sep. 30, 2021

Restructuring and Related Activities [Abstract]

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVES

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVESRestructuring and related expense includes both restructuring expense for severance and related costs and facilities-related costs, primarily comprised estimated future variable lease costs for vacated properties with no intent or ability of sublease, and

accelerated rent amortization expense.

For restructuring events that involve lease assets and liabilities, the Company applies lease reassessment and modification guidance and evaluates the right-of-use assets for potential impairment. If the Company plans to exit all or distinct portions of a facility and does not have the ability or intent to sublease, the Company will accelerate the amortization of each of those lease components through the vacate date. The accelerated amortization is recorded as a component of Restructuring and related expense in the Company's condensed consolidated statements of operations. Related variable lease expenses will continue to be expensed as incurred through the vacate date, at which time the Company will reassess the liability balance to ensure it appropriately reflects the remaining liability associated with the premises and record a liability for the estimated future variable lease costs.

Restructuring and related expense for the three and nine months ended September 30, 2021 and 2020 was comprised of the following (in thousands):



	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Severance and related costs	$	481	$	1,789	$	3,076	$	8,276
Variable and other facilities-related costs	1,286		$	1,501	4,103		2,380
Accelerated amortization of lease assets due to cease-use	—		$	—	3,368		70
	$	1,767	$	3,290	$	10,547	$	10,726

Accelerated Rent Amortization

Accelerated rent amortization is recognized from the date that the Company commences the plan to fully or partially vacate a facility, for which there is no intent or ability to enter into a sublease, through the final vacate date. The accelerated rent amortization recorded in connection with the Facilities Initiative reduced the value of the Company's Operating lease right-of-use assets recorded in the Company's condensed consolidated balance sheets at September 30, 2021 and December 31, 2020, respectively. The liability for the total lease payments for each respective facility is included as a component of Operating lease liabilities in the Company's condensed consolidated balance sheets, both current and noncurrent (see Note 17). The Company may incur additional future expense if it is unable to sublease other locations included in its restructuring initiatives.

2020 Restructuring Initiative

In 2020, the Company implemented a restructuring plan to eliminate certain positions and redundant facilities, primarily in connection with the ECI Acquisition, to further streamline the Company's global footprint and improve its operations (the "2020 Restructuring Initiative"). In connection with this initiative, the Company expects to eliminate duplicate functions arising from the ECI Acquisition and support its efforts to integrate the two companies.

The Company recorded restructuring and related expense of $0.6 million and $2.9 million in connection with the 2020 Restructuring Initiative in the three months ended September 30, 2021 and 2020, respectively, and $2.9 million and $8.7 million in the nine months ended September 30, 2021 and 2020, respectively.

The amount recorded in the three months ended September 30, 2021 was comprised of $0.5 million for severance and related costs for approximately 10 employees and $0.1 million for costs related to restructured facilities. The amount recorded in the nine months ended September 30, 2021 was comprised of $3.1 million for severance and related costs for approximately 30 employees and $0.5 million of expense for variable and other costs related to restructured facilities, offset by a credit of $0.7 million for changes in estimate to previously recorded facilities-related amounts. The amount recorded in the nine months ended September 30, 2020 represents severance and related costs for approximately 125 employees.

The Company expects the amount accrued for severance at September 30, 2021 will be paid in 2021. The Company expects that it will record additional restructuring and related expense approximating $1 million under the 2020 Restructuring Initiative in the aggregate for severance and planned facility consolidations. A summary of the 2020 Restructuring Initiative accrual activity for severance and related costs for the nine months ended September 30, 2021 is as follows (in thousands):


	Balance at January 1, 2021		Initiatives charged to expense		Adjustments for changes in estimate		Cash payments		Balance at September 30, 2021
Severance	$	5,237	$	3,076	$	—	$	(5,921)	$	2,392
Facilities	1,256		473		(670)		(1,059)		—
	$	6,493	$	3,549	$	(670)	$	(6,980)	$	2,392

2019 Restructuring and Facilities Consolidation Initiative

In June 2019, the Company implemented a restructuring plan to further streamline the Company's global footprint, improve its operations and enhance its customer delivery (the "2019 Restructuring Initiative"). The 2019 Restructuring Initiative includes facility consolidations, refinement of the Company's research and development activities, and a reduction in workforce. The facility consolidations under the 2019 Restructuring Initiative (the "Facilities Initiative") include a consolidation of the Company's North Texas sites into a single campus, housing engineering, customer training and support, and administrative functions, as well as a reduction or elimination of certain excess and duplicative facilities worldwide. In addition, the Company is substantially consolidating its global software laboratories and server farms into two lower cost North American sites. The Company continues to evaluate its properties included in the Facilities Initiative for accelerated amortization and/or right-of-use asset impairment. The Company expects that the actions under the Facilities Initiative will be completed in 2021.

In connection with the 2019 Restructuring Initiative, the Company recorded restructuring and related expense of $1.2 million and $0.4 million in the three months ended September 30, 2021 and 2020, respectively, and $7.7 million and $2.1 million in the nine months ended September 30, 2021 and 2020, respectively.

The amount recorded in the three months ended September 30, 2021 was for facilities-related costs. Of the amount recorded in the nine months ended September 30, 2021, $3.4 million was for accelerated amortization of lease assets and $4.3 million related to variable and other facilities-related costs in connection with facility consolidations. The amount recorded in the three months ended September 30, 2020 primarily related to facility consolidations. The amount recorded in the nine months ended September 30, 2020 was comprised of $0.6 million for severance and related costs for five employees and $1.5 million related to facility consolidations. These amounts include nominal credits to restructuring and related expense in the three and nine months ended September 30, 2020, representing changes in estimate for both severance and related expenses and facilities-related expenses. The Company estimates that it will record nominal, if any, additional restructuring and related expense in connection with this initiative.

A summary of the 2019 Restructuring Initiative accrual activity for the nine months ended September 30, 2021 is as follows (in thousands):


	Balance at January 1, 2021		Initiatives charged to expense		Reclassify accelerated amortization to operating lease liabilities		Cash payments		Balance at September 30, 2021
Severance	$	173	$	—	$	—	$	(173)	$	—
Facilities	766		7,668		(3,368)		(3,301)		1,765
	$	939	$	7,668	$	(3,368)	$	(3,474)	$	1,765

Balance Sheet Classification

The current portions of accrued restructuring are included as a component of Accrued expenses and the long-term portions of accrued restructuring are included as a component of Other long-term liabilities in the condensed consolidated balance sheets. The long-term portions of accrued restructuring relate to facilities and totaled $1.8 million at September 30, 2021 and $0.8 million at December 31, 2020.

DEBT	9 Months Ended
DEBT	Sep. 30, 2021
Debt Disclosure [Abstract]
DEBT	DEBT 2020 Credit Facility On March 3, 2020, the Company entered into a Senior Secured Credit Facilities Credit Agreement (as amended, the "2020 Credit Facility"), by and among the Company, as a guarantor, Ribbon Communications Operating Company, Inc., as the borrower ("Borrower"), Citizens Bank, N.A. ("Citizens"), as administrative agent, a lender, issuing lender, swingline lender, joint lead arranger and bookrunner, Santander Bank, N.A., as a lender, joint lead arranger and bookrunner, and the other lenders party thereto (each, together with Citizens Bank, N.A. and Santander Bank, N.A., referred to individually as a "Lender", and collectively, the "Lenders"). The proceeds of the 2020 Credit Facility were used, in part, to pay off in full all obligations of the Company under its prior credit facility (the "2019 Credit Facility"). The 2020 Credit Facility provides for $500 million of commitments from the lenders to the Borrower, comprised of $400 million in term loans (the "2020 Term Loan Facility") and a $100 million facility available for revolving loans (the "2020 Revolving Credit Facility"). Under the 2020 Revolving Credit Facility, a $30 million sublimit is available for letters of credit and a $20 million sublimit is available for swingline loans. Under the 2020 Credit Facility, the Company was originally required to make quarterly principal payments aggregating approximately $10 million in the first year, $20 million per year for the following three years, and $30 million in the last year, with the remaining balance due on the maturity date. The 2020 Credit Facility also requires periodic interest payments until maturity. The indebtedness and other obligations under the 2020 Credit Facility are unconditionally guaranteed on a senior secured basis by the Company, Edgewater Networks, Inc., a wholly-owned subsidiary of the Company, and GENBAND Inc., a wholly-owned subsidiary of the Company (together, the "Guarantors"). The facilities under the 2020 Credit Facility are secured by first-priority liens on substantially all of the assets of the Borrower and the Guarantors, including substantially all of the assets of the Company. The 2020 Credit Facility requires compliance with certain financial covenants, including a minimum Consolidated Fixed Charge Coverage Ratio and a maximum Consolidated Net Leverage Ratio (each as defined in the 2020 Credit Facility, and each tested on a quarterly basis). In addition, the 2020 Credit Facility contains various covenants that, among other restrictions, limit the Company’s and its subsidiaries’ ability to incur or assume indebtedness; grant or assume liens; make acquisitions or engage in mergers; sell, transfer, assign or convey assets; repurchase equity and make dividend and certain other restricted payments; make investments; engage in transactions with affiliates; enter into sale and leaseback transactions; enter into burdensome agreements; change the nature of its business; modify their organizational documents; and amend or make prepayments on certain junior debt. The 2020 Credit Facility contains events of default that are customary for a secured credit facility. If an event of default relating to bankruptcy or other insolvency events with respect to the Company or any of its subsidiaries occurs, all obligations under the 2020 Credit Facility will immediately become due and payable. If any other event of default occurs under the 2020 Credit Facility, the lenders may accelerate the maturity of the obligations outstanding under the Credit Facility and exercise other rights and remedies, including charging a default rate of interest equal to 2.00% per year above the rate that would otherwise be applicable. In addition, if any event of default exists under the 2020 Credit Facility, the lenders can commence foreclosure or other actions against the collateral. On August 18, 2020 (the "First Amendment Effective Date"), the Borrower entered into a First Amendment to the 2020 Credit Facility (the "First Amendment"). Pursuant to an assignment and assumption agreement entered into by Citizens and certain affiliates of Whitehorse Capital on the First Amendment Effective Date (collectively, "HIG Whitehorse"), and consented to by Citizens and the Borrower, $75 million of the 2020 Term Loan Facility, designated as the Term B Loan (the "Term B Loan"), was assigned from Citizens to HIG Whitehorse. The remaining $325 million of the 2020 Term Loan Facility that was not assigned to HIG Whitehorse was deemed the Term A Loan (the "Term A Loan" and, together with the Term B Loan, the "Amended 2020 Term Loan Facility"). The Term A Loan and the 2020 Revolving Credit Facility mature in March 2025. The Term A Loan and 2020 Revolving Credit Facility bear interest at the Borrower's option at either the LIBOR rate plus a margin ranging from 1.50% to 3.50% per year, or the base rate (the highest of the Federal Funds Effective Rate (as defined in the 2020 Credit Facility) plus 0.50%, or the prime rate announced from time to time in The Wall Street Journal) plus a margin ranging from 0.50% to 2.50% per year (the "Applicable Margin"). The Applicable Margin varies depending on the Company's Consolidated Net Leverage Ratio (as defined in the 2020 Credit Agreement). The base rate and the LIBOR rate are each subject to a zero percent floor. The Company was required to make quarterly principal payments on the Term A Loan aggregating approximately $10 million in the first year, $16 million per year in each of the next two years, $20 million in the fourth year and $16 million in the last year, with the final payment approximating $244 million due on the maturity date. The Borrower could prepay all amounts under the Term A Loan and the 2020 Revolving Credit Facility at any time without premium or penalty (other than customary LIBOR breakage costs), subject to certain notice requirements. The Term B Loan was scheduled to mature in March 2026 and bore interest, at the Borrower's option, at either the LIBOR rate plus a margin of 7.50% per year, or the base rate (the highest of the Federal Funds Effective Rate (as defined in the First Amendment) plus 0.50%, or the prime rate announced from time to time in The Wall Street Journal, plus a margin of 6.50% per year. The Term B Loan had a lower rate of amortization than the Term A Loan and was subject to a 1.0% premium if voluntarily repaid in connection with a repricing transaction (as defined in the 2020 Credit Facility) occurring prior to the six month anniversary of the First Amendment Effective Date. The Company was required to make quarterly principal payments totaling approximately $1 million in the first year and $8 million in the aggregate over the next four and a half years, with the final payment approximating $66 million. The First Amendment reduced the Borrower's ability to incur new tranches of term loans, or increases in commitments under the Amended 2020 Term Loan Facility or the 2020 Revolving Credit Facility. Specifically, such indebtedness could be incurred up to an aggregate dollar amount equal to 75% of the Company's Consolidated Adjusted EBITDA (as defined in the 2020 Credit Facility), reduced from 100% prior to the First Amendment, as of the most recently ended fiscal quarter for which financial statements had been delivered to the lenders, plus additional amounts, so long as the Borrower's Consolidated Net Leverage Ratio (as defined in the 2020 Credit Agreement) did not exceed 2.25:1.00, reduced from 2.75:1.00 under the 2020 Credit Agreement. The First Amendment also reduced the amount of Unrestricted Cash (as defined in the 2020 Credit Agreement) used in calculating the Borrower's Consolidated Net Leverage Ratio from $25 million to $10 million. On December 1, 2020, the Borrower entered into a Second Amendment to the 2020 Credit Facility to obtain consent for an equity exchange with AVCT in connection with the Kandy Sale, as well as to amend certain other provisions of the 2020 Credit Facility. At December 31, 2020, the Company had an outstanding Term A Loan balance of $318.5 million at an average interest rate of 3.4%, and an outstanding Term B Loan balance of $74.6 million at an average interest rate of 8.4%. The 2020 Revolving Credit Facility did not have an outstanding balance but had $5.6 million of letters of credit outstanding with an interest rate of 2.5%. On March 3, 2021 (the "Third Amendment Effective Date"), the Company, the Borrower and certain of its subsidiaries entered into a Third Amendment to Credit Agreement (the "Third Amendment"), which further amended the 2020 Credit Facility. The Third Amendment provided for an incremental term loan facility to the Borrower in the original principal amount of $74.6 million, the proceeds of which were used on the Third Amendment Effective Date to consummate an open market purchase of all outstanding amounts under the Term B Loan. Upon the consummation of the open market purchase, the Term B Loans were assigned to the Borrower and immediately cancelled, such that the outstanding amount under the Term A Loan and incremental term loan facility were combined and held by the Lenders (the "2020 Term Loan") with the same terms as the Term A Loan. The Company wrote off $2.5 million of capitalized debt issuance costs in connection with the Third Amendment, which is included in Interest expense, net, in the Company's condensed consolidated statement of operations for the nine months ended September 30, 2021. The Company is required to make quarterly principal payments on the 2020 Term Loan aggregating approximately $20 million per year in the first three years and $30 million in the fourth year, with the final payment approximating $300 million due on the maturity date. The Third Amendment increased the Borrower's ability to incur new incremental revolving commitments or term loans. Such indebtedness can be incurred up to an aggregate dollar limit equal to 100% of the Company's Consolidated Adjusted EBITDA (as defined in the 2020 Credit Facility) as of the most recently ended fiscal quarter for which financial statements have been delivered to the Lenders, plus additional amounts, so long as the Borrower's Consolidated Net Leverage Ratio (as defined in the Credit Agreement) does not exceed 2.75:1.00, increased from 2.25:1.00 under the First Amendment. The Third Amendment also increased the amount of Unrestricted Cash (as defined in the 2020 Credit Facility) used in calculating the Borrower's Consolidated Net Leverage Ratio from $10.0 million to $25.0 million. At September 30, 2021, the Company had an outstanding 2020 Term Loan balance of $380.5 million at an average interest rate of 2.90% and $5.9 million of letters of credit outstanding with an interest rate of 2.00%. The Company was in compliance with all covenants of the 2020 Credit Facility at both September 30, 2021 and December 31, 2020. Short-Term Loans From time to time, the Company enters into uncommitted and unsecured short-term loans to finance exports in China. The Company did not have any such short-term loans outstanding at September 30, 2021 and December 31, 2020. Letters of Credit and Performance and Bid Bonds The Company uses letters of credit, performance and bid bonds in the course of its business. At September 30, 2021, the Company had bank guarantees, performance and bid bonds under various uncommitted facilities (collectively, the "Guarantees") aggregating $24.8 million, and $5.9 million of letters of credit under the 2020 Credit Facility (the "Letters of Credit"). At December 31, 2020, the Company had Guarantees aggregating $27.0 million and $5.6 million of Letters of Credit. At September 30, 2021 and December 31, 2020, the Company had cash collateral of $2.5 million and $2.7 million, respectively, supporting the Guarantees, which are included in Restricted cash in the condensed consolidated balance sheets.

- Definition

The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-URI http://asc.fasb.org/topic&trid=2208564

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (h)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(c))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1C
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495334-112611

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1E
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495348-112611

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1I
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495371-112611

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (i)
-URI http://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

+ Details

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES

9 Months Ended

Sep. 30, 2021

Derivative Instruments and Hedging Activities Disclosure [Abstract]

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES

The Company is exposed to financial market risk related to foreign currency fluctuations and changes in interest rates. These exposures are actively monitored by management. To manage the volatility related to the exposure to changes in interest rates, the Company has entered into a derivative financial instrument. Management's objective is to reduce, where it is deemed appropriate to do so, fluctuations in earnings and cash flows associated with changes in interest rates. Ribbon's policies and practices are to use derivative financial instruments only to the extent necessary to manage exposures. Ribbon does not hold or issue derivative financial instruments for trading or speculative purposes.

The Company records derivatives on the balance sheet at fair value. The accounting for changes in the fair value of derivatives depends on the intended use of the derivative, whether the Company has elected to designate a derivative in a hedging relationship and apply hedge accounting and whether the hedging relationship has satisfied the criteria necessary to apply hedge accounting. Derivatives designated and qualifying as a hedge of the exposure to changes in the fair value of an asset, liability, or firm commitment attributable to a specific risk, such as interest rate risk, are considered fair value hedges. Derivatives designated and qualifying as a hedge of the exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. Derivatives may also be designated as hedges of the foreign currency exposure of a net investment in a foreign operation. Hedge accounting generally provides for the matching of the timing of gain or loss recognition on the hedging instrument with the recognition of the changes in the fair value of the hedged asset or liability that are attributable to the hedged risk in a fair value hedge, or the earnings effect of the hedged forecasted transactions in a cash flow hedge. The Company may enter into derivative contracts that are intended to economically hedge certain of its risk even though hedge accounting does not apply or the Company elects not to apply hedge accounting.

Cash Flow Hedge of Interest Rate Risk

The 2020 Term Loan Facility had outstanding balances of $380.5 million and $393.1 million at September 30, 2021 and December 31, 2020, respectively. The 2020 Revolving Credit Facility was undrawn at both September 30, 2021 and December 31, 2020. Borrowings under the 2020 Credit Facility have variable interest rates based on LIBOR (see Note 10). As a result of

exposure to interest rate movements, during March 2020, the Company entered into an interest rate swap arrangement, which effectively converted its $400 million term loan with its variable interest rate based upon one-month LIBOR to an aggregate fixed rate of 0.904%, plus a leverage-based margin as defined in the 2020 Credit Facility. The notional amount of this swap at September 30, 2021 was $400 million, and the swap matures on March 3, 2025, the same date the 2020 Credit Facility matures.

The Company’s objectives in using interest rate derivatives are to add stability to interest expense and to manage its exposure to interest rate movements. To accomplish this objective, the Company is using an interest rate swap as part of its interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable amounts from a counterparty in exchange for the Company making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount.

The effective portion of changes in the fair value of designated derivatives that qualify as cash flow hedges is recorded in accumulated other comprehensive income (loss) in the condensed consolidated balance sheet and is subsequently reclassified into earnings in the period that the hedged forecasted transactions affect earnings. During the three and nine months ended September 30, 2021 and 2020, such a derivative was used to hedge the variable cash flows associated with the outstanding borrowings under the 2020 Credit Facility and the Company has accounted for this derivative as an effective hedge. Any ineffective portion of the change in the fair value of the derivative would be recognized directly in earnings.

Amounts reported in accumulated other comprehensive income (loss) related to the Company's derivative are reclassified to interest expense as interest is accrued on the Company’s variable-rate debt. Based upon projected forward rates, the Company estimates as of September 30, 2021 that $3.2 million may be reclassified as an increase to interest expense over the next twelve months.

The impact of the Company’s derivative financial instrument on its condensed consolidated statement of comprehensive income (loss) for the three and nine months ended September 30, 2021 and 2020 was as follows (in thousands):



	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Gain (loss) recognized in other comprehensive income (loss) on derivative (effective portion)	$	30	$	(121)	$	4,905	$	(13,778)
Amount reclassified from accumulated other comprehensive income (loss) to interest expense (effective portion)	830		761		2,419		921
	$	860	$	640	$	7,324	(12,857)

The fair values and locations in the condensed consolidated balance sheets at September 30, 2021 and December 31, 2020 of the Company's derivative liability designated as a hedging instrument were as follows (in thousands):


	Balance sheet location	September 30, 2021		December 31, 2020
Interest rate derivative - liability derivative	Accrued expenses and other	$	3,225	$	3,157
Interest rate derivative - liability derivative	Other long-term liabilities	$	399	$	7,791

The Company has classified the interest rate derivative aggregating $3.6 million and $10.9 million at September 30, 2021 and December 31, 2020, respectively, as Level 2 fair value measurements within the fair value hierarchy (see Note 1).

REVENUE RECOGNITION

9 Months Ended

Sep. 30, 2021

Revenue from Contract with Customer [Abstract]

REVENUE RECOGNITION

REVENUE RECOGNITIONThe Company derives revenue from two primary sources: products and services. Product revenue includes the Company's hardware and software that function together to deliver the products' essential functionality. Software and hardware are also

sold on a standalone basis. Services include customer support (software updates, upgrades and technical support), consulting, design services, installation services and training. Generally, contracts with customers contain multiple performance obligations, consisting of products and services. For these contracts, the Company accounts for individual performance obligations separately if they are considered distinct.

When an arrangement contains more than one performance obligation, the Company will allocate the transaction price to each performance obligation on a relative standalone selling price basis. The Company utilizes the observable price of goods and services when they are sold separately to similar customers in order to estimate standalone selling price.

The Company's software licenses typically provide a perpetual right to use the Company's software. The Company also sells term-based software licenses that expire and Software-as-a-Service ("SaaS")-based software which are referred to as subscription arrangements. The Company does not customize its software nor are installation services required, as the customer has a right to utilize internal resources or a third-party service company. The software and hardware are delivered before related services are provided and are functional without professional services or customer support. The Company has concluded that its software licenses are functional intellectual property that are distinct, as the user can benefit from the software on its own. Product revenue is typically recognized upon transfer of control or when the software is made available for download, as this is the point the user of the software can direct the use of, and obtain substantially all of the remaining benefits from, the functional intellectual property. The Company begins to recognize software revenue related to the renewal of subscription software licenses at the start of the subscription period.

The Company offers warranties on its products. Certain of the Company's warranties are considered to be assurance-type in nature, ensuring the product is functioning as intended. Assurance-type warranties do not represent separate performance obligations. The Company also sells separately-priced maintenance service contracts which qualify as service-type warranties and represent separate performance obligations. The Company does not allow and has no history of accepting product returns.

Services revenue includes revenue from customer support and other professional services. Customer support includes software updates on a when-and-if-available basis, telephone support, integrated web-based support and bug fixes or patches. The Company sells its customer support contracts at a percentage of list or net product price. Customer support revenue is recognized ratably over the term of the customer support agreement, which is typically one year.

The Company's professional services include consulting, technical support, resident engineer services, design services and installation services. Because control transfers over time, revenue is recognized based on progress toward completion of the performance obligation. The method to measure progress toward completion requires judgment and is based on the nature of the products or services to be provided. The Company generally uses the input method to measure progress for its contracts because it believes such method best depicts the transfer of assets to the customer, which occurs as the Company incurs costs for the contracts. However, in some instances, the Company uses the output method because it best depicts the transfer of asset to the customer. Under the cost-to-cost measure of progress, the progress toward completion is measured based on the ratio of costs incurred to date to the total estimated costs at completion of the performance obligation. When the measure of progress is based upon expended labor, progress toward completion is measured as the ratio of labor time expended to date versus the total estimated labor time required to complete the performance obligation. Revenue is recorded proportionally as costs are incurred or as labor is expended. Costs to fulfill these obligations include internal labor as well as subcontractor costs.

Customer training includes courses offered by the Company. The related revenue is typically recognized as the training services are performed.

The Company's typical performance obligations include the following:

Performance Obligation

When Performance Obligation is Typically Satisfied

When Payment is Typically Due

Software and Product Revenue

Software licenses (perpetual or term)

Upon transfer of control; typically, when made available for download (point in time)

Generally, within 30 days of invoicing except for term licenses, which may be paid for over time

Software licenses (subscription)

Upon activation of hosted site (over time)

Generally, within 30 days of invoicing

Hardware

When control of the hardware passes to the customer; typically, upon delivery (point in time)

Generally, within 30 days of invoicing

Software upgrades

Upon transfer of control; typically, when made available for download (point in time)

Generally, within 30 days of invoicing

Customer Support Revenue

Customer support

Ratably over the course of the support contract (over time)

Generally, within 30 days of invoicing

Professional Services

Other professional services (excluding training services)

As work is performed (over time)

Generally, within 30 days of invoicing (upon completion of services)

Training

When the class is taught (point in time)

Generally, within 30 days of services being performed

Significant Judgments

The Company's contracts with customers often include promises to transfer multiple products and services to the customer. Determining whether products and services are considered distinct performance obligations that should be accounted for separately versus together may require significant judgment.

Judgment is required to determine the standalone selling price ("SSP") for each distinct performance obligation. The Company typically has more than one SSP for individual products and services due to the stratification of those products and services by customers and circumstances. In these instances, the Company may use information such as the size of the customer and geographic region in determining the SSP.

Deferred Revenue

Deferred revenue is a contract liability representing amounts collected from or invoiced to customers in excess of revenue recognized. This results primarily from the billing of annual customer support agreements where the revenue is recognized over the term of the agreement. The value of deferred revenue will increase or decrease based on the timing of recognition of revenue.

Disaggregation of Revenue

The Company disaggregates its revenue from contracts with customers based on the nature of the products and services and the geographic regions in which each customer is domiciled. The Company's revenue for the three and nine months ended September 30, 2021 and 2020 was disaggregated as follows:



Three months ended September 30, 2021	Product revenue		Service revenue (maintenance)		Service revenue (professional services)		Total revenue
United States	$	47,134	$	33,391	$	12,764	$	93,289


Europe, Middle East and Africa	32,234		19,290		7,971		59,495

Asia Pacific	26,087		10,618		4,215		40,920
Other	6,271		8,371		2,052		16,694
	$	111,726	$	71,670	$	27,002	$	210,398



Three months ended September 30, 2020	Product revenue		Service revenue (maintenance)		Service revenue (professional services)		Total revenue
United States	$	57,503	$	33,275	$	14,072	$	104,850


Europe, Middle East and Africa	41,265		19,720		7,133		68,118

Asia Pacific	22,233		12,208		5,183		39,624
Other	7,925		8,439		2,162		18,526
	$	128,926	$	73,642	$	28,550	$	231,118


Nine months ended September 30, 2021	Product revenue		Service revenue (maintenance)		Service revenue (professional services)		Total revenue
United States	$	140,074	$	97,813	$	35,516	$	273,403


Europe, Middle East and Africa	91,751		59,684		22,622		174,057

Asia Pacific	70,714		31,203		13,886		115,803
Other	20,205		24,112		6,800		51,117
	$	322,744	$	212,812	$	78,824	$	614,380


Nine months ended September 30, 2020	Product revenue		Service revenue (maintenance)		Service revenue (professional services)		Total revenue
United States	$	150,980	$	98,392	$	35,482	$	284,854


Europe, Middle East and Africa	97,431		54,042		15,920		167,393

Asia Pacific	59,030		26,742		14,017		99,789
Other	18,246		24,157		5,154		47,557
	$	325,687	$	203,333	$	70,573	$	599,593

The Company's product revenue from indirect sales through its channel partner program and from its direct sales program for the three and nine months ended September 30, 2021 and 2020 was as follows (in thousands):


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Indirect sales through channel partner program	$	25,214	$	36,586	$	72,491	$	97,839
Direct sales	86,512		92,340		250,253		227,848
	$	111,726	$	128,926	$	322,744	$	325,687

The Company's product revenue from sales to enterprise customers and from sales to service provider customers for the three and nine months ended September 30, 2021 and 2020 was as follows (in thousands):


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Sales to enterprise customers	$	20,034	$	36,937	$	67,225	$	100,168
Sales to service provider customers	91,692		91,989		255,519		225,519
	$	111,726	$	128,926	$	322,744	$	325,687

The Company's product revenue and service revenue components by segment for the three and nine months ended September 30, 2021 and 2020 was as follows (in thousands):


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Product revenue
Cloud and Edge	$	65,587	$	74,860	$	180,100	$	201,380
IP Optical Networks	46,139		54,066		142,644		124,307
Total product revenue	$	111,726	$	128,926	$	322,744	$	325,687

Service revenue
Maintenance
Cloud and Edge	$	56,786	$	57,623	$	169,445	$	171,032
IP Optical Networks	14,884		16,019		43,367		32,301
Total maintenance revenue	71,670		73,642		212,812		203,333
Professional services
Cloud and Edge	20,064		21,047		59,735		56,056
IP Optical Networks	6,938		7,503		19,089		14,517
Total professional services revenue	27,002		28,550		78,824		70,573
Total service revenue	$	98,672	$	102,192	$	291,636	$	273,906

Revenue Contract Balances

The timing of revenue recognition, billings and cash collections results in billed accounts receivable; unbilled receivables, which are contract assets; and customer advances and deposits, which are contract liabilities, in the Company's condensed consolidated balance sheets. Amounts are billed as work progresses in accordance with agreed-upon contractual terms, either at periodic intervals or upon achievement of contractual milestones. Completion of services and billing may occur subsequent to revenue recognition, resulting in contract assets. The Company may receive advances or deposits from its customers before revenue is recognized, resulting in contract liabilities that are classified as deferred revenue. These assets and liabilities are reported in the Company's condensed consolidated balance sheets on a contract-by-contract basis as of the end of each reporting period. Changes in the contract asset and liability balances during the nine months ended September 30, 2021 were not materially impacted by any factors other than billing and revenue recognition. Nearly all of the Company's deferred revenue balance is related to services revenue, primarily customer support contracts. Unbilled receivables stem primarily from engagements where services have been performed; however, billing cannot occur until services are completed.

In some arrangements, the Company allows customers to pay for term-based software licenses and products over the term of the software license. The Company also sells SaaS-based software under subscription arrangements, with payment terms over the term of the SaaS agreement. Amounts recognized as revenue in excess of amounts billed are recorded as unbilled receivables. Unbilled receivables that are anticipated to be invoiced in the next twelve months are included in Accounts receivable on the Company's condensed consolidated balance sheets. The changes in the Company's accounts receivable, unbilled receivables and deferred revenue balances for the nine months ended September 30, 2021 were as follows (in thousands):


	Accounts receivable		Unbilled accounts receivable		Deferred revenue (current)		Deferred revenue (long-term)
Balance at January 1, 2021	$	179,331	$	58,407	$	96,824	$	26,010
Increase (decrease), net	(17,507)		15,479		(7,271)		(4,392)
Balance at September 30, 2021	$	161,824	$	73,886	$	89,553	$	21,618

The Company recognized approximately $81 million of revenue in the nine months ended September 30, 2021 that was recorded as deferred revenue at December 31, 2020 and approximately $86 million of revenue in the nine months ended September 30, 2020 that was recorded as deferred revenue at December 31, 2019. Of the Company's deferred revenue reported as long-term in its condensed consolidated balance sheet at September 30, 2021, the Company expects that approximately $4 million will be recognized as revenue in 2022, approximately $10 million will be recognized as revenue in 2023 and approximately $8 million will be recognized as revenue in 2024 and beyond.

All freight-related customer invoicing is recorded as revenue, while the shipping and handling costs that occur after control of the promised goods or services transfer to the customer are reported as fulfillment costs, a component of Cost of revenue - product in the Company's condensed consolidated statements of operations.

Deferred Commissions Cost

Sales commissions earned by the Company's employees are considered incremental and recoverable costs of obtaining a contract with a customer. Expense related to commission payments has been deferred on our condensed consolidated balance sheet and is being amortized over the expected life of the customer contract, which averages five years. The current and long-term portions of deferred commission expense are included as components of Other current assets and Other assets, respectively. At both September 30, 2021 and December 31, 2020, the Company had $4.1 million of deferred sales commissions capitalized.

- Definition

The entire disclosure of revenue from contract with customer to transfer good or service and to transfer nonfinancial asset. Includes, but is not limited to, disaggregation of revenue, credit loss recognized from contract with customer, judgment and change in judgment related to contract with customer, and asset recognized from cost incurred to obtain or fulfill contract with customer. Excludes insurance and lease contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-URI http://asc.fasb.org/topic&trid=49130388

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130551-203045

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 13
-Subparagraph (b)(2)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130556-203045

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130550-203045

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130558-203045

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=123351226&loc=SL49130554-203045

+ Details

OPERATING SEGMENT INFORMATION

9 Months Ended

Sep. 30, 2021

Segment Reporting [Abstract]

OPERATING SEGMENT INFORMATION

The Company has two reportable segments, which are intended to align with the manner in which the business is managed: Cloud and Edge, and IP Optical Networks.

The Cloud and Edge segment provides secure and reliable software and hardware products, solutions and services for enabling Voice over Internet Protocol ("VoIP") communications, Voice over Long-Term Evolution ("VoLTE") and Voice Over 5G ("VoNR") communications and Unified Communications and Collaboration ("UC&C") within service provider and enterprise networks and from the cloud. The Cloud and Edge products are increasingly software-centric and cloud-native for deployment on private, public or hybrid cloud infrastructures, in data centers, on enterprise premises and within service provider networks. Ribbon's Cloud and Edge product portfolio consists of our Session Border Controller ("SBC") products and our Network Transformation ("NTR") products.

The IP Optical Networks segment provides high-performance, secure and reliable hardware and software products solutions for IP networking, switching, routing and optical transport designed to support and enable technologies like 5G, distributed cloud computing and corresponding applications by delivering ultra-low cost-per-bit transport and multi-service flexibility. The IP Optical Networks portfolio offers multiple solutions, including 5G-native solutions for mobile backhaul, metro and edge aggregation, core networking, data center interconnect, legacy NTR and transport solutions for wholesale carriers. This portfolio is offered to service provider, enterprise and industry verticals with critical transport network infrastructures including utilities, government, defense, transportation, and education and research. Information for the IP Optical Networks segment for the nine months ended September 30, 2020 includes the financial results of this segment for the period subsequent to the ECI Acquisition Date.

The Company has not provided segment asset information as such information is not provided to the CODM and accordingly, asset information is not used in assessing segment performance. Please see Note 6 for information regarding the

allocation of goodwill between segments. Segment revenue and expenses included in the tables below represent direct revenue and expenses attributable to each segment for revenue, adjusted gross profit, and the research and development expense component of adjusted EBITDA. The Company's sales, marketing, and general and administrative functions support both segments and accordingly, these costs are allocated to both segments.

The CODM utilizes revenue, adjusted gross profit and adjusted EBITDA (earnings before interest, taxes, depreciation and amortization) to measure and assess each segment's performance. The Company calculates adjusted EBITDA by excluding from income (loss) from operations: depreciation; amortization of acquired intangible assets; stock-based compensation; certain litigation costs; acquisition-, disposal- and integration-related expense; and restructuring and related expense. These adjusted measures may also exclude other items in future periods that the Company believes are not part of the Company's core business. Adjusted gross profit and adjusted EBITDA are not financial measures determined in accordance with U.S. GAAP and may not be comparable to similarly titled measures used by other companies and should not be considered a substitute for income (loss) from operations or gross profit or other results reported in accordance with U.S. GAAP. See below for a reconciliation of adjusted gross profit to gross profit and adjusted EBITDA to income (loss) from operations, as those are the most directly comparable U.S. GAAP measures.

The tables below provide information regarding revenue, adjusted gross profit, adjusted EBITDA and depreciation expense by reportable segment for the three and nine months ended September 30, 2021 and 2020 (in thousands):


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Segment revenue:
Cloud and Edge	$	142,437	$	153,530	$	409,280	$	428,468
IP Optical Networks	67,961		77,588		205,100		171,125
Revenue	$	210,398	$	231,118	$	614,380	$	599,593



	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Segment adjusted gross profit:
Cloud and Edge	$	95,998	$	101,910	$	276,170	$	279,624
IP Optical Networks	24,918		35,305		84,544		71,737
Total segment adjusted gross profit	120,916		137,215		360,714		351,361
Stock-based compensation expense	(588)		(261)		(1,412)		(616)
Acquisition-related inventory and facilities adjustments	—		(2,000)		—		(2,000)
Gross profit	$	120,328	$	134,954	$	359,302	$	348,745


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Segment adjusted EBITDA:
Cloud and Edge	$	44,945	$	41,921	$	116,811	$	89,157
IP Optical Networks	(13,240)		1,464		(22,400)		(6,681)
Total segment adjusted EBITDA	31,705		43,385		94,411		82,476
Depreciation	(4,209)		(4,494)		(12,684)		(12,754)
Amortization of intangible assets	(17,221)		(16,349)		(50,225)		(45,352)
Stock-based compensation	(4,561)		(3,969)		(14,411)		(10,167)
Acquisition-related inventory and facilities adjustments	—		(2,000)		—		(2,000)
Litigation costs	—		—		—		(2,101)



Acquisition-, disposal- and integration-related expense	(1,955)		(1,366)		(4,204)		(14,607)
Restructuring and related expense	(1,767)		(3,290)		(10,547)		(10,726)
Income (loss) from operations	1,992		11,917		$	2,340	$	(15,231)

Segment depreciation expense:
Cloud and Edge	$	3,018	$	2,990	$	9,297	$	8,967
IP Optical Networks	1,191		1,504		3,387		3,787
Depreciation expense	$	4,209	$	4,494	$	12,684	$	12,754

- Definition

The entire disclosure for reporting segments including data and tables. Reportable segments include those that meet any of the following quantitative thresholds a) it's reported revenue, including sales to external customers and intersegment sales or transfers is 10 percent or more of the combined revenue, internal and external, of all operating segments b) the absolute amount of its reported profit or loss is 10 percent or more of the greater, in absolute amount of 1) the combined reported profit of all operating segments that did not report a loss or 2) the combined reported loss of all operating segments that did report a loss c) its assets are 10 percent or more of the combined assets of all operating segments.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 31
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8924-108599

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8981-108599

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8721-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 40
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9031-108599

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 26
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8844-108599

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 41
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9038-108599

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8933-108599

Reference 10: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8736-108599

Reference 11: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 42
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e9054-108599

Reference 12: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8657-108599

Reference 13: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 21
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123359005&loc=d3e8721-108599

Reference 14: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-URI http://asc.fasb.org/topic&trid=2134510

+ Details

MAJOR CUSTOMERS

9 Months Ended

Sep. 30, 2021

Risks and Uncertainties [Abstract]

MAJOR CUSTOMERS

The following customer contributed 10% or more of the Company's revenue in the three and nine months ended September 30, 2021 and 2020:

Three months ended

Nine months ended

September 30,
2021

September 30,
2020

September 30,
2021

September 30,
2020

Verizon Communications Inc.

18%

16%

17%

15%

At September 30, 2021, one customer accounted for 10% or more of the Company's accounts receivable balance, representing approximately 16% of total accounts receivable. At December 31, 2020, one customer accounted for 10% or more of the Company's accounts receivable balance, representing approximately 12% of total accounts receivable. The Company performs ongoing credit evaluations of its customers and generally does not require collateral on accounts receivable, although in some instances the Company may require letters of credit to support customer outstanding accounts receivable balances. The Company maintains an allowance for doubtful accounts and such losses have been within management's expectations.

COMMON STOCK REPURCHASES	9 Months Ended
COMMON STOCK REPURCHASES	Sep. 30, 2021
Equity [Abstract]
COMMON STOCK REPURCHASES	COMMON STOCK REPURCHASESIn the second quarter of 2019, the Company's Board of Directors (the "Board") approved a stock repurchase program (the "Repurchase Program") pursuant to which the Company could repurchase up to $75 million of its common stock prior to April 18, 2021. The Company did not repurchase any common stock in the year ended December 31, 2020 or in the period from January 1, 2021 though the expiration of the Repurchase Program on April 18, 2021, and had $70.5 million remaining for future repurchases upon the expiration of the Repurchase Program.

STOCK-BASED COMPENSATION PLANS

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

STOCK-BASED COMPENSATION PLANS

2019 Stock Incentive Plan

The Company's Amended and Restated 2019 Incentive Award Plan (the "2019 Plan") provides for the award of options to purchase the Company's common stock ("stock options"), stock appreciation rights ("SARs"), restricted stock awards ("RSAs"), performance-based stock awards ("PSAs"), restricted stock units ("RSUs"), performance-based stock units ("PSUs") and other stock- or cash-based awards. Awards can be granted under the 2019 Plan to the Company's employees, officers and non-employee directors, as well as consultants and advisors of the Company and its subsidiaries.

2007 Plan

The Company's 2007 Plan provided for the award of stock options, SARs, RSAs, PSAs, RSUs, PSUs and other stock-based awards to employees, officers, non-employee directors, consultants and advisors of the Company and its subsidiaries. On and following June 5, 2019, with the exception of shares underlying awards outstanding as of that date, no additional shares may be granted under the 2007 Plan.

Assumed Stock Plans

In connection with the acquisition of Edgewater Networks, Inc. in August 2018, the Company assumed Edgewater's Amended and Restated 2002 Stock Option Plan (the "Edgewater Plan") to the extent of the shares underlying the options outstanding under the Edgewater Plan as of the Edgewater Acquisition Date (the "Edgewater Options"). The Edgewater Options were converted to Ribbon stock options (the "Ribbon Replacement Options") which are vesting under the same schedules as the respective Edgewater Options.

In connection with the Company's acquisitions of Performance Technologies Inc. ("PT") in 2014, and Network Equipment Technologies, Inc. ("NET") in 2012, the Company assumed their stock plans (collectively, the "Assumed Plans"). Any outstanding awards under the Assumed Plans that in the future expire, terminate, are cancelled or surrendered, or are repurchased by the Company will be returned to the 2019 Plan. Accordingly, no additional shares may be granted under the Assumed Plans.

Executive Equity Arrangements

Inducement Awards

In connection with his appointment as President and Chief Executive Office of Ribbon, and as an inducement for Bruce McClelland's ("Mr. McClelland") commencement of employment, the Company awarded Mr. McClelland sign-on equity grants, comprised of 462,963 RSUs and a PSU grant with both market and service conditions (the "Inducement PSUs") on March 16, 2020. The RSUs vested and were released to Mr. McClelland on March 16, 2021. Subject to Mr. McClelland's continued employment, the Inducement PSUs are eligible to vest and be settled in up to 4,750,000 shares of Ribbon common stock upon the achievement of specified share price thresholds on or prior to September 1, 2024. The first share price threshold for Mr. McClelland’s Inducement PSUs was achieved on February 26, 2021, and accordingly 1,333,333 shares were released to him. These releases are included in the applicable tables below.

Performance-Based Stock Grants

In addition to granting RSUs to its executives and certain of its employees, the Company also grants PSUs to certain of its executives, including the Inducement PSUs granted to Mr. McClelland as described above.

In 2021, 2020 and 2019, the Company granted certain of its executives (the "2021 PSUs", "2020 PSUs" and "2019 PSUs", respectively), of which 60% of each executive's PSU grant had both performance and service conditions (the "Performance PSUs") and 40% had both market and service conditions (the "Market PSUs").

Each executive's Performance PSU grant is comprised of three consecutive fiscal year performance periods beginning in

the year of grant (each, a "Fiscal Year Performance Period"), with one-third of the Performance PSUs attributable to each Fiscal Year Performance Period. The number of shares that will be vest for each Fiscal Year Performance Period, if any, will be based on the achievement of certain metrics related to the Company's financial performance for the applicable year on a standalone basis (each, a "Fiscal Year Performance Condition"). The Company's achievement of the goals for each Fiscal Year Performance Condition (and the number of shares of Company common stock to vest as a result thereof) are being measured on a linear sliding scale in relation to specific threshold, target and stretch performance conditions, with any shares earned vesting in the first quarter of the fiscal year following the third Performance Period of the grant, pending each executive's continued employment with the Company through that date. The number of shares of common stock underlying the Performance PSUs that can be earned will in no event exceed 200% of the Performance PSUs. Shares subject to the Performance PSUs that fail to be earned will be forfeited.

The Market PSUs have one three-year performance period, beginning January 1 in the year of grant and ending on December 31, three years thereafter (the "Market Performance Period"). The number of shares subject to the Market PSUs that will vest, if any, will be dependent upon the Company's total shareholder return ("TSR") compared with the TSR of the companies included in a custom index for the applicable Market Performance Period, measured by the Compensation Committee after the Market Performance Period ends, with any shares earned vesting in the first quarter of the fiscal year following the respective Market Performance Period, pending each executive's continued employment with the Company through that date. The number of shares of common stock underlying the Market PSUs that can be earned will in no event exceed 200% of the Market PSUs. Shares subject to the Market PSUs that fail to be earned will be forfeited.

In addition, in connection with his appointment as Executive Vice President and General Manager, Packet Optical Networking, the Company granted Sam Bucci 133,333 PSUs (the "Bucci Stock Price PSUs") with both market and service conditions. Subject to Mr. Bucci's continued employment, the Bucci Stock Price PSUs were eligible to vest and be settled in shares of Ribbon's common stock upon the achievement of a specific share price threshold on or prior to January 31, 2022. The share price threshold for Mr. Bucci’s Stock Price PSUs was achieved on February 12, 2021, and the shares were released to him. This release is included in the applicable table below.

Accounting for Performance PSUs. Once the grant date criteria have been met for a Fiscal Year Performance Period, the Company records stock-based compensation expense for the respective underlying Performance PSUs based on its assessment of the probability that each performance condition will be achieved and the level, if any, of such achievement. The Compensation Committee determines the number of shares earned, if any, after the Company's financial results for each Fiscal Year Performance Period are finalized. Upon the determination by the Compensation Committee of the number of shares that will be received upon vesting of the Performance PSUs, such number of shares becomes fixed and the unamortized expense is recorded through the remainder of the service period, generally three years from the date of grant, at which time the total Performance PSUs earned, if any, will vest, pending each executive's continued employment with the Company through that date.

Accounting for Market PSUs. PSUs that include a market condition require the use of a Monte Carlo simulation approach to model future stock price movements based upon the risk-free rate of return, the date of return, the volatility of each entity and the pair-wise covariance between each entity. These results are then used to calculate the grant date fair values of the respective PSUs. The Company is required to record expense for the PSUs with market conditions through their respective final vesting dates, regardless of the number of shares that are ultimately earned.

At March 31, 2021, the calculation of the grant date fair value of the Market PSUs granted on March 15, 2021 had not been completed. The Company used a grant date fair value of $8.65, the closing stock price on the date of grant, to calculate expense attributable to the three months ended March 31, 2021 for these Market PSUs. During the three months ended June 30, 2021, the Company completed the Monte Carlo valuation of these Market PSUs and calculated that the grant date fair value of each Market PSU was $13.67. The Company recorded a cumulative adjustment to expense to account for the change in grant date fair value in the second quarter of 2021. The change in grant date fair value and related cumulative adjustment did not have a material impact on its consolidated financial statements.

Employee Bonus Program

Effective in 2021, the Company added an equity component to its cash bonus program for eligible employees, under which

RSUs with a grant date fair value equal to 50% of each employee's target cash bonus were granted to each such employee (the "Bonus RSUs"). Correspondingly, cash target bonuses for eligible employees were reduced by 50%. The Company implemented this program to expand the opportunities for stock ownership more broadly throughout the Company. The Bonus RSU grants are included in the applicable table below.

Stock Options

The activity related to the Company's outstanding stock options for the nine months ended September 30, 2021 was as follows:


	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2021	207,710	$	12.69



Exercised	(13,815)	$	1.76

Expired	(3,686)	$	17.13
Outstanding at September 30, 2021	190,209	$	13.40	2.79	$	171
Vested or expected to vest at September 30, 2021	190,206	$	13.40	2.79	$	171
Exercisable at September 30, 2021	190,121	$	13.41	2.79	$	171

The total intrinsic value of options exercised was nominal in the three months ended September 30, 2021 and $0.1 million in the nine months ended September 30, 2021. The Company received nominal cash from option exercises in the three months ended September 30, 2021 and approximately $24,000 in the nine months ended September 30, 2021.

Restricted Stock Awards and Units

The activity related to the Company's RSAs for the nine months ended September 30, 2021 was as follows:


	Shares	Weighted Average Grant Date Fair Value
Unvested balance at January 1, 2021	86,983	$	7.04


Vested	(86,983)	$	7.04

Unvested balance at September 30, 2021	—	$	—

The activity related to the Company's RSUs for the nine months ended September 30, 2021 was as follows:


	Shares	Weighted Average Grant Date Fair Value
Unvested balance at January 1, 2021	6,531,110	$	3.32
Granted	3,109,797	$	8.55

Vested	(3,233,661)	$	3.23
Forfeited	(692,672)	$	4.53
Unvested balance at September 30, 2021	5,714,574	$	6.07

The total grant date fair value of shares of restricted stock granted under RSAs and RSUs that vested during the nine months ended September 30, 2021 was $11.1 million.

Performance-Based Stock Units

The activity related to the Company's PSUs for the nine months ended September 30, 2021 was as follows:


	Shares	Weighted Average Grant Date Fair Value
Unvested balance at January 1, 2021	6,035,931	$	1.56
Granted	672,121	$	10.22
Vested	(1,525,681)	$	0.98
Forfeited	(193,318)	$	5.89
Unvested balance at September 30, 2021	4,989,053	$	2.90

The total grant date fair value of shares of restricted stock granted under PSUs that vested during the nine months ended September 30, 2021 was $1.5 million.

Stock-Based Compensation

The condensed consolidated statements of operations include stock-based compensation for the three and nine months ended September 30, 2021 and 2020 as follows (in thousands):


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Product cost of revenue	$	96	$	57	$	216	$	123
Service cost of revenue	492		204		1,196		493
Research and development	1,223		868		3,010		2,164
Sales and marketing	1,581		1,189		5,207		2,952
General and administrative	1,169		1,651		4,782		4,435
	$	4,561	$	3,969	$	14,411	$	10,167

At September 30, 2021, there was $29.3 million, net of expected forfeitures, of unrecognized stock-based compensation expense related to unvested stock options, stock awards and stock units. This expense is expected to be recognized over a weighted average period of approximately two years.

LEASES

9 Months Ended

Sep. 30, 2021

Leases [Abstract]

LEASES

The Company has operating and finance leases for corporate offices, research and development facilities, and certain equipment. Operating leases are reported separately in the Company's condensed consolidated balance sheets. Assets acquired under finance leases are included in Property and equipment, net, in the condensed consolidated balance sheets.

The Company determines if an arrangement is a lease at inception. A contract is determined to contain a lease component if the arrangement provides the Company with a right to control the use of an identified asset. Lease agreements may include lease and non-lease components. In such instances for all classes of underlying assets, the Company does not separate lease and non-lease components but rather, accounts for the entire arrangement under leasing guidance. Leases with an initial term of 12 months or less are not recorded on the balance sheet and lease expense for these leases is recognized on a straight-line basis over the lease term.

Right-of-use assets and lease liabilities are initially measured based on the present value of the future minimum fixed lease payments (i.e., fixed payments in the lease contract) over the lease term at the commencement date. As the Company's existing

leases do not have a readily determinable implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date in determining the present value of future minimum fixed lease payments. The Company calculates its incremental borrowing rate to reflect the interest rate that it would have to pay to borrow on a collateralized basis an amount equal to the lease payments in a similar economic environment over a similar term and considers its historical borrowing activities and market data from entities with comparable credit ratings in this determination. The measurement of the right-of-use asset also includes any lease payments made prior to the commencement date (excluding any lease incentives) and initial direct costs incurred. The Company assessed its right-of-use assets for impairment as of September 30, 2021 and December 31, 2020 and determined no impairment has occurred.

Lease terms may include options to extend or terminate the lease and the Company incorporates such options in the lease term when it has the unilateral right to make such an election and it is reasonably certain that the Company will exercise that option. In making this determination, the Company considers its prior renewal and termination history and planned usage of the assets under lease, incorporating expected market conditions.

For operating leases, lease expense for minimum fixed lease payments is recognized on a straight-line basis over the lease term. The expense for finance leases includes both interest and amortization expense components, with the interest component calculated based on the effective interest method and the amortization component calculated based on straight-line amortization of the right-of-use asset over the lease term. Lease contracts may contain variable lease costs, such as common area maintenance, utilities and tax reimbursements that vary over the term of the contract. Variable lease costs are not included in minimum fixed lease payments and as a result, are excluded from the measurement of the right-of-use assets and lease liabilities. The Company expenses all variable lease costs as incurred.

In connection with the 2020 Restructuring Initiative, the Company accelerated amortization totaling $0.2 million and $0.6 million in the three and nine months ended September 30, 2021, respectively, for leased facilities that were vacated in 2021 as part of the consolidation of certain sites following the ECI Acquisition. The Company did not record estimated future variable lease costs in the three or nine months ended September 30, 2021 related to the 2020 Restructuring Initiative.

In connection with the 2019 Restructuring Initiative, certain lease assets related to facilities are being partially or fully vacated as the Company consolidates its facilities. The Company has no plans to enter into sublease agreements for certain facilities. The Company ceased use of these facilities in the first quarter of 2021, the first and fourth quarters of 2020 and the third quarter of 2019. Accordingly, the Company accelerated the amortization of the associated lease assets through the planned cease-use date of each facility, resulting in additional amortization expense of $3.4 million and $0.1 million in the nine months ended September 30, 2021 and 2020, respectively. The Company also recorded expense of $1.4 million in the aggregate in the nine months ended September 30, 2021 for all estimated future variable lease costs related to these facilities. The Company did not record additional amortization expense or estimated future variable lease costs in the three months ended September 30, 2021 or 2020 related to the 2019 Restructuring Initiative.

All accelerated amortization and accrual of future variable costs are recorded as Restructuring and related expense in the Company's condensed consolidated statements of operations. At September 30, 2021 and December 31, 2020, the Company had accruals of $1.8 million and $0.8 million, respectively, for all future anticipated variable lease costs related to these facilities. The Company may incur additional future expense if it is unable to sublease other locations included in the Facilities Initiative.

The Company leases its corporate offices and other facilities under operating leases, which expire at various times through 2032. In December 2020, the Company began relocating from its former leased Plano, Texas facility to its recently completed leased facility, also located in Plano, Texas, which became the Company's corporate headquarters. The Company's relocation to the new corporate headquarters was completed in the first quarter of 2021.

The Company's right-of-use lease assets and lease liabilities at September 30, 2021 and December 31, 2020 were as follows (in thousands):


	Classification	September 30, 2021		December 31, 2020
Assets:
Operating lease assets	Operating lease right-of-use assets	$	54,446	$	69,757
Finance lease assets*	Property and equipment, net	416		983
Total leased assets		$	54,862	$	70,740

Liabilities:
Current:
Operating	Operating lease liabilities	$	17,848	$	17,023
Finance	Accrued expenses and other	574		902
Noncurrent:
Operating	Operating lease liabilities, net of current	58,609		72,614
Finance	Other long-term liabilities	159		568
Total lease liabilities		$	77,190	$	91,107

* Finance lease assets were recorded net of accumulated depreciation of $1.6 million and $1.9 million at September 30, 2021 and December 31, 2020, respectively.

The components of lease expense for the three and nine months ended September 30, 2021 and 2020 were as follows (in thousands):


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020

Operating lease cost*	$	4,996	$	5,350	$	19,027	$	13,911
Finance lease cost:
Amortization of leased assets	158		291		567		929
Interest on lease liabilities	12		39		58		141
Short-term lease cost	3,327		4,821		9,889		15,945
Variable lease costs (costs excluded from minimum fixed lease payments)**	589		697		3,247		1,969
Sublease income	(510)		(307)		(985)		(871)
Net lease cost	$	8,572	$	10,891	$	31,803	$	32,024

* Operating lease costs for the three and nine months ended September 30, 2021 included $0.6 million and $4.0 million, respectively, of accelerated amortization for certain assets partially or fully vacated in 2021 with no intent or ability to sublease. Operating lease costs for the nine months ended September 30, 2020 included $0.1 million of accelerated amortization for certain assets partially or fully vacated in 2020 with no ability to sublease. The Company did not record accelerated amortization in the three months ended September 30, 2020.

** Variable lease costs for the nine months ended September 30, 2021 included accruals of $1.4 million for all future estimated variable expenses related to certain assets partially or fully vacated in 2021 with no intent or ability to sublease. No such variable costs were accrued in the three months ended September 30, 2021 or in the three and nine months ended September 30, 2020.

Cash flow information related to the Company's leases for the nine months ended September 30, 2021 and 2020 was as follows (in thousands):


	Nine months ended
		September 30, 2021		September 30, 2020
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases		$	16,509	$	13,933
Operating cash flows for finance leases		$	58	$	141
Financing cash flows for finance leases		$	736	$	971

Other information related to the Company's leases as of September 30, 2021 and December 31, 2020 was as follows:


	September 30, 2021		December 31, 2020
Weighted average remaining lease term (years):
Operating leases	6.44		6.59
Finance leases	1.21		1.70
Weighted average discount rate:
Operating leases	5.64	%	5.67	%
Finance leases	4.36	%	6.15	%

Future minimum fixed lease payments under noncancelable leases at September 30, 2021 were as follows (in thousands):


	September 30, 2021
	Operating		Finance
	leases		leases
Remainder of 2021	$	5,877	$	178
2022	20,496		514
2023	17,712		63
2024	9,741		—
2025	7,733		—
2026 and beyond	31,225		—
Total lease payments	92,784		755
Less: interest	(16,327)		(22)
Present value of lease liabilities	$	76,457	$	733

LEASES

The Company's right-of-use lease assets and lease liabilities at September 30, 2021 and December 31, 2020 were as follows (in thousands):


	Classification	September 30, 2021		December 31, 2020
Assets:
Operating lease assets	Operating lease right-of-use assets	$	54,446	$	69,757
Finance lease assets*	Property and equipment, net	416		983
Total leased assets		$	54,862	$	70,740

Liabilities:
Current:
Operating	Operating lease liabilities	$	17,848	$	17,023
Finance	Accrued expenses and other	574		902
Noncurrent:
Operating	Operating lease liabilities, net of current	58,609		72,614
Finance	Other long-term liabilities	159		568
Total lease liabilities		$	77,190	$	91,107

* Finance lease assets were recorded net of accumulated depreciation of $1.6 million and $1.9 million at September 30, 2021 and December 31, 2020, respectively.

The components of lease expense for the three and nine months ended September 30, 2021 and 2020 were as follows (in thousands):


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020

Operating lease cost*	$	4,996	$	5,350	$	19,027	$	13,911
Finance lease cost:
Amortization of leased assets	158		291		567		929
Interest on lease liabilities	12		39		58		141
Short-term lease cost	3,327		4,821		9,889		15,945
Variable lease costs (costs excluded from minimum fixed lease payments)**	589		697		3,247		1,969
Sublease income	(510)		(307)		(985)		(871)
Net lease cost	$	8,572	$	10,891	$	31,803	$	32,024

Cash flow information related to the Company's leases for the nine months ended September 30, 2021 and 2020 was as follows (in thousands):


	Nine months ended
		September 30, 2021		September 30, 2020
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases		$	16,509	$	13,933
Operating cash flows for finance leases		$	58	$	141
Financing cash flows for finance leases		$	736	$	971

Other information related to the Company's leases as of September 30, 2021 and December 31, 2020 was as follows:


	September 30, 2021		December 31, 2020
Weighted average remaining lease term (years):
Operating leases	6.44		6.59
Finance leases	1.21		1.70
Weighted average discount rate:
Operating leases	5.64	%	5.67	%
Finance leases	4.36	%	6.15	%

Future minimum fixed lease payments under noncancelable leases at September 30, 2021 were as follows (in thousands):


	September 30, 2021
	Operating		Finance
	leases		leases
Remainder of 2021	$	5,877	$	178
2022	20,496		514
2023	17,712		63
2024	9,741		—
2025	7,733		—
2026 and beyond	31,225		—
Total lease payments	92,784		755
Less: interest	(16,327)		(22)
Present value of lease liabilities	$	76,457	$	733

INCOME TAXES	9 Months Ended
INCOME TAXES	Sep. 30, 2021
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company's income tax provisions for the nine months ended September 30, 2021 and 2020 reflect the Company's estimates of the effective rates expected to be applicable for the respective full years, adjusted for any discrete events, which are recorded in the period that they occur. These estimates are reevaluated each quarter based on the Company's estimated tax expense for the full year. The estimated effective tax rate includes the impact of valuation allowances in various jurisdictions. The Company intends to continue to maintain a full valuation allowance on its deferred tax assets until there is sufficient evidence to support the reversal of all or some portion of the allowance. However, given its current earnings and anticipated future earnings, the Company believes there is a reasonable possibility that within the next 12 months, sufficient positive evidence may become available to reach a conclusion that a significant portion of the U.S. valuation allowance will no longer be needed. Release of the valuation allowance would result in the recognition of certain deferred tax assets and a decrease in income tax expense for the period in which the release is recorded. However, the exact timing and amount, of the valuation allowance release, if any, are subject to change on the basis of the level of profitability that the Company is able to actually achieve.

- Definition

The entire disclosure for income taxes. Disclosures may include net deferred tax liability or asset recognized in an enterprise's statement of financial position, net change during the year in the total valuation allowance, approximate tax effect of each type of temporary difference and carryforward that gives rise to a significant portion of deferred tax liabilities and deferred tax assets, utilization of a tax carryback, and tax uncertainties information.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 21
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32857-109319

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 11.C)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330215-122817

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 17
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32809-109319

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 6.I.5.Q1)
-URI http://asc.fasb.org/extlink&oid=122134291&loc=d3e330036-122817

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=121826272&loc=d3e32705-109319

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 270
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6424409&loc=d3e44925-109338

Reference 7: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-URI http://asc.fasb.org/topic&trid=2144680

Reference 8: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6424122&loc=d3e41874-109331

Reference 9: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(h)(2))
-URI http://asc.fasb.org/extlink&oid=120395691&loc=d3e23780-122690

+ Details

COMMITMENTS AND CONTINGENCIES	9 Months Ended
COMMITMENTS AND CONTINGENCIES	Sep. 30, 2021
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Liabilities for Royalty Payments to the IIA. Prior to the ECI Acquisition, ECI had received research and development grants from the Office of the Innovation Authority of the Israeli Ministry of Economics (the "IIA"). The Company assumed ECI's contract with the IIA, which requires the Company to pay royalties to the IIA on proceeds from the sale of products which the Israeli government has supported by way of research and development grants. The royalties for grants prior to 2017 were calculated at the rates of 1.3% to 5.0% of the aggregated proceeds from the sale of such products developed at certain of the Company's R&D centers, up to an amount not exceeding 100% of such grants plus interest at LIBOR. Effective for grants approved in 2017 and subsequently, interest was calculated at the higher of LIBOR plus 1.5% to 2.75%. At September 30, 2021, the Company's maximum possible future royalties commitment, including $4.3 million of unpaid royalties accrued, was $35.9 million, including interest of $1.9 million, based on estimates of future product sales, grants received from the IIA not yet repaid, and management's estimation of products still to be sold. Research and Development Grants. The Company records grants received from the IIA as a reduction to research and development expense. Royalties payable to the IIA are recognized pursuant to sales of related products and are classified as Cost of revenue. The Company does not anticipate receiving material grants from the IIA in the foreseeable future. Litigation. On November 8, 2018, Ron Miller, a purported stockholder of the Company, filed a Class Action Complaint (the "Miller Complaint") in the United States District Court for the District of Massachusetts (the "Massachusetts District Court") against the Company and three of its former officers (collectively, the "Defendants"), claiming to represent a class of purchasers of Sonus common stock during the period from January 8, 2015 through March 24, 2015 and alleging violations of the federal securities laws. Similar to a previous complaint entitled Sousa et al. vs. Sonus Networks, Inc. et al., which was dismissed with prejudice by an order dated June 6, 2017, the Miller Complaint claims that the Defendants made misleading forward-looking statements concerning Sonus' expected fiscal first quarter of 2015 financial performance, which statements were also the subject of an August 7, 2018 Securities and Exchange Commission Cease and Desist Order, whose findings the Company neither admitted nor denied. The Miller plaintiffs are seeking monetary damages. After the Miller Complaint was filed, several parties filed and briefed motions seeking to be selected by the Massachusetts District Court to serve as a Lead Plaintiff in the action. On June 21, 2019, the Massachusetts District Court appointed a group as Lead Plaintiffs and the Lead Plaintiffs filed an amended complaint on July 19, 2019. On August 30, 2019, the Defendants filed a motion to dismiss the Miller Complaint and, on October 4, 2019, the Lead Plaintiffs filed an opposition to the motion to dismiss. There was an oral argument on the motion to dismiss on February 12, 2020. In addition, the Company is often a party to disputes and legal proceedings that it considers routine and incidental to its business. Management does not expect the results of any of these actions to have a material effect on the Company's business or condensed consolidated financial statements.

BASIS OF PRESENTATION (Policies)	9 Months Ended
BASIS OF PRESENTATION (Policies)	Sep. 30, 2021
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting only of normal recurring items, necessary for their fair presentation with accounting principles generally accepted in the United States of America ("GAAP") and with the rules and regulations of the U.S. Securities and Exchange Commission ("SEC"). On December 1, 2020 (the "Kandy Sale Date"), the Company completed the sale of its cloud-based enterprise service business (the "Kandy Communications Business") to AVCT and, accordingly, the revenue and expenses of the Kandy Communications Business are excluded from the Company's condensed consolidated financial statements for the three and nine months ended September 30, 2021. On March 3, 2020 (the "ECI Acquisition Date"), a subsidiary of the Company merged (the "ECI Acquisition") with ECI Telecom Group Ltd ("ECI"). The financial results of ECI are included in the Company's condensed consolidated financial statements for the period subsequent to the ECI Acquisition Date. Interim results are not necessarily indicative of results for a full year or any future interim period. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Company's Annual Report on Form 10-K for the year ended December 31, 2020 (the "Annual Report"), which was filed with the SEC on February 26, 2021.
Operating Segments	Operating Segments The Company's chief operating decision maker (the "CODM") is its President and Chief Executive Officer. Effective in the fourth quarter of 2020 and in connection with the ECI Acquisition, the CODM began to assess the Company's performance based on the performance of two separate organizations within Ribbon: the Cloud and Edge segment ("Cloud and Edge") and the IP Optical Networks segment ("IP Optical Networks"). Financial information for the IP Optical Networks segment included in the Company's financial results for the nine months ended September 30, 2020 is for the period subsequent to the ECI Acquisition Date through September 30, 2020.
Reclassifications	Reclassifications In the fourth quarter of 2020, the Company reclassified amounts recorded for amortization of acquired intangible assets in prior presentations from Cost of revenue - product and Sales and marketing to a separate line included in operating expenses in the condensed consolidated statements of operations, as management believes this presentation enhances the comparability of the Company's financial statements with industry peers. These reclassifications also did not impact the condensed consolidated balance sheets or statements of cash flows for any historical periods. The Company did not reclassify depreciation of property and equipment related to production activities from cost of revenue to other accounts. Certain reclassifications, not affecting previously reported net income (loss), have been made to the previously issued financial statements to conform to the current period presentation.
Principles of Consolidation	Principles of Consolidation The condensed consolidated financial statements include the accounts of Ribbon and its wholly-owned subsidiaries. Intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates and Judgments	Use of Estimates and Judgments The preparation of financial statements in conformity with GAAP requires Ribbon to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and judgments relied upon in preparing these condensed consolidated financial statements include accounting for business combinations, revenue recognition for multiple element arrangements, inventory valuations, assumptions used to determine the fair value of stock-based compensation, intangible asset and goodwill valuations, including impairments, legal contingencies and recoverability of Ribbon's net deferred tax assets and the related valuation allowances. Ribbon regularly assesses these estimates and records changes in estimates in the period in which they become known. Ribbon bases its estimates on historical experience and various other assumptions that it believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Restricted Cash	Restricted Cash The Company classifies as restricted cash all cash pledged as collateral to secure long-term obligations and all cash whose use is otherwise limited by contractual provisions.
Transfers of Financial Assets	Transfers of Financial AssetsThe Company maintains customer receivables factoring agreements with a number of financial institutions primarily for IP Optical Networks sales outside of the United States. Under the terms of these agreements, the Company may transfer receivables to the financial institutions, on a non-recourse basis, provided that the financial institutions approve the receivables in advance. The Company maintains credit insurance policies from major insurance providers or obtains letters of credit from the customers for a majority of its factored trade receivables. The Company accounts for the factoring of its financial assets as a sale of the assets and records the factoring fees, when incurred, as a component of interest expense in the condensed consolidated statements of operations, and the proceeds from the sales of receivables are included in cash from operating activities in the condensed consolidated statements of cash flows.
Fair Value of Financial Instruments and Fair Value Hierarchy	Fair Value of Financial Instruments and Fair Value Hierarchy The carrying amounts of the Company's financial instruments approximate their fair values and include cash equivalents, accounts receivable, borrowings under a revolving credit facility, accounts payable and long-term debt. Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. The three-tier fair value hierarchy is based on the level of independent, objective evidence surrounding the inputs used to measure fair value. A financial instrument's categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The fair value hierarchy is as follows: Level 1. Level 1 applies to assets or liabilities for which there are quoted prices in active markets for identical assets or liabilities. Level 2. Level 2 applies to assets or liabilities for which there are inputs that are directly or indirectly observable in the marketplace, such as quoted prices for similar assets or liabilities in active markets or quoted prices for identical assets or liabilities in markets with insufficient volume or infrequent transactions (less active markets). Level 3. Level 3 applies to assets or liabilities for which there are unobservable inputs to the valuation methodology that are significant to the measurement of the fair value of the assets or liabilities.
Fair Value Option - Investment in AVCI	Fair Value Option - Investment in AVCT In connection with the Debentures Conversion, the Company elected to use the fair value option to account for its equity investment in AVCT as permitted under Accounting Standards Codification ("ASC") 825, Financial Instruments ("ASC 825"). ASC 820, Fair Value Measurement ("ASC 820") provides the fair value framework for valuing such investments. In accordance with ASC 820, the Company is recording the investment in AVCT at fair value, with changes in fair value recorded as a component of Other (expense) income, net, in the condensed consolidated statements of operations.
Recent Accounting Pronouncements	Recent Accounting Pronouncements The Financial Accounting Standards Board ("FASB") issued the following accounting pronouncement which became effective for the Company in 2021, and which did not have a material impact on its condensed consolidated financial statements: In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes ("ASU 2019-12"), which modifies ASC 740 to simplify the accounting for income taxes. ASU 2019-12 addresses the accounting for hybrid tax regimes, tax basis step-up in goodwill obtained in a transaction that is not a business combination, separate financial statements of legal entities not subject to tax, intraperiod tax allocation exception to incremental approach, ownership changes in investments - changes from a subsidiary to an equity method investment, ownership changes in investments - changes from an equity method investment to a subsidiary, interim period accounting for enacted changes in tax law and year-to-date loss limitation in interim period tax accounting. The FASB issued the following accounting pronouncement, which the Company does not believe will have a material impact on its condensed consolidated financial statements upon adoption: In January 2021, the FASB issued ASU 2021-01, Reference Rate Reform (Topic 848): Scope ("ASU 2021-01"), which refines the scope of Accounting Standards Codification 848, Reference Rate Reform ("ASC 848") and clarifies some of its guidance as part of the FASB's monitoring of global reference rate reform activities. ASU 2021-01 permits entities to elect certain optional expedients and exceptions when accounting for derivative contracts and certain hedging relationships affected by changes in the interest rates used for discounting cash flows, for computing variation margin settlements, and for calculating price alignment interest in connection with reference rate reform activities under way in global financial markets (the "discounting transition"). ASU 2021-01 is effective for the Company prospectively in any period through December 31, 2022 that a modification is made to the terms of the derivatives affected by the discounting transition.

BASIS OF PRESENTATION (Tables)

9 Months Ended

Sep. 30, 2021

Accounting Policies [Abstract]

Schedule of Error Corrections and Prior Period Adjustments

These reclassifications for the three and nine months ended September 30, 2020 were as follows (in thousands):


	Three months ended September 30, 2020			Nine months ended September 30, 2020
		Prior presentation		Amounts reclassified		Revised presentation		Prior presentation		Amounts reclassified		Revised presentation
Product revenue		$	128,926			$	128,926	$	325,687			$	325,687
Service revenue		102,192				102,192		273,906				273,906
Total revenue		231,118		—		231,118		599,593		—		599,593
Cost of revenue - product		70,188		(11,643)		58,545		176,650		(31,547)		145,103
Cost of revenue - service		37,619				37,619		105,745				105,745
Total cost of revenue		107,807		(11,643)		96,164		282,395		(31,547)		250,848
Total gross profit		123,311		11,643		134,954		317,198		31,547		348,745
Research and development		49,113				49,113		143,204				143,204
Sales and marketing		41,604		(4,706)		36,898		115,572		(13,805)		101,767
General and administrative		16,021				16,021		48,320				48,320
Amortization of acquired intangible assets		—		16,349		16,349		—		45,352		45,352

Acquisition-, disposal- and integration-related		1,366				1,366		14,607				14,607
Restructuring and related		3,290				3,290		10,726				10,726
Total operating expenses		111,394		11,643		123,037		332,429		31,547		363,976
Income (loss) from operations		$	11,917	$	—	$	11,917	$	(15,231)	$	—	$	(15,231)

BUSINESS ACQUISITION (Tables)

9 Months Ended

Sep. 30, 2021

Business Combination and Asset Acquisition [Abstract]

Summary of Allocation of Purchase Consideration

A summary of the allocation of the purchase consideration for ECI is as follows (in thousands):


Fair value of consideration transferred:
Cash consideration:
Repayment of ECI outstanding debt obligations	$	183,266


Cash paid to selling shareholders	139,244
Payment to selling shareholders from sale of ECI real estate assets	33,400
Less cash and restricted cash acquired	(9,058)
Net cash consideration	346,852

Fair value of Ribbon stock issued	108,550

Fair value of total consideration	$	455,402

Fair value of assets acquired and liabilities assumed:
Current assets, net of cash and restricted cash acquired	$	120,203
Property and equipment	54,913
Intangible assets:
In-process research and development	34,000
Developed technology	111,900
Customer relationships	116,000
Trade names	3,000
Goodwill	191,996


Other noncurrent assets	37,528

Deferred revenue	(4,369)
Other current liabilities	(146,618)

Deferred revenue, net of current	(3,726)
Deferred tax liability	(13,308)
Other long-term liabilities	(46,117)
	$	455,402

Unaudited Pro Forma Results


			4
	Three months ended			Nine months ended
	September 30, 2020			September 30, 2020
Revenue	$	231,118		$	624,800
Net income (loss)	$	7,036		$	(41,345)
Diluted earnings (loss) per share	$	0.05		$	(0.29)

Schedule of Components of Acquisition Related Costs

The Company's acquisition-, disposal- and integration-related expenses for the three and nine months ended September 30, 2021 and 2020 were as follows (in thousands):



	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Professional and services fees (acquisition-related)	$	13	$	1,003	$	156	$	14,017

Professional and services fees (disposal-related)	—		—		241		—
Integration-related expenses	1,942		363		3,807		590
	$	1,955	$	1,366	$	4,204	$	14,607

EARNINGS (LOSS) PER SHARE (Tables)

9 Months Ended

Sep. 30, 2021

Earnings Per Share [Abstract]

Schedule of Calculations of Shares Used to Compute Basic and Diluted Earnings (Loss) Per Share

The calculations of shares used to compute earnings (loss) per share were as follows (in thousands):


	Three months ended		Nine months ended
	September 30, 2021	September 30, 2020	September 30, 2021	September 30, 2020
Weighted average shares outstanding - basic	148,184	144,948	147,204	136,837
Potential dilutive common shares	—	6,732	—	—
Weighted average shares outstanding - diluted	148,184	151,680	147,204	136,837

INVENTORY (Tables)

9 Months Ended

Sep. 30, 2021

Inventory Disclosure [Abstract]

Schedule of Inventory

Inventory at September 30, 2021 and December 31, 2020 consisted of the following (in thousands):


	September 30, 2021		December 31, 2020

On-hand final assemblies and finished goods inventories	$	48,176	$	46,921
Deferred cost of goods sold	1,467		1,165
	49,643		48,086
Less noncurrent portion (included in other assets)	(4,854)		(2,336)
Current portion	$	44,789	$	45,750

INTANGIBLE ASSETS AND GOODWILL (Tables)

9 Months Ended

Sep. 30, 2021

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of Intangible Assets

The Company's intangible assets at September 30, 2021 and December 31, 2020 consisted of the following (in thousands):


September 30, 2021	Weighted average amortization period (years)	Cost		Accumulated amortization		Net carrying value
In-process research and development	*	$	34,000	$	—	$	34,000

Developed technology	7.93	306,380		172,485		133,895
Customer relationships	11.86	268,140		70,464		197,676
Trade names	3.88	5,000		3,440		1,560

Internal use software	3.00	730		730		—
	9.17	$	614,250	$	247,119	$	367,131


December 31, 2020	Weighted average amortization period (years)	Cost		Accumulated amortization		Net carrying value
In-process research and development	*	$	34,000	$	—	$	34,000

Developed technology	7.93	306,380		143,050		163,330
Customer relationships	11.86	268,140		50,627		217,513
Trade names	3.88	5,000		2,487		2,513

Internal use software	3.00	730		730		—
	9.17	$	614,250	$	196,894	$	417,356

* An in-process research and development intangible asset has an indefinite life until the product is generally available, at which time such asset is typically reclassified to developed technology.

Schedule of Estimated Future Amortization Expense for Intangible Assets

Estimated future amortization expense for the Company's intangible assets at September 30, 2021 was as follows (in thousands):


Years ending December 31,
Remainder of 2021	$	16,401
2022	60,449
2023	53,966
2024	46,899
2025	40,338
2026	36,489
Thereafter	112,589
	$	367,131

Schedule of Goodwill

The changes in the carrying value of the Company's goodwill in the nine months ended September 30, 2020 were as follows (in thousands):


	Cloud and Edge		IP Optical Networks		Total




Balance at January 1, 2020*	$	224,896	$	—	$	224,896
Acquisition of ECI	—		191,996		191,996
Balance at September 30, 2020	$	224,896	$	191,996	$	416,892

* Balance is presented net of accumulated impairment losses of $167.4 million for the Cloud and Edge segment.

The components of goodwill at September 30, 2021 and 2020 were as follows (in thousands):


	Cloud and Edge		IP Optical Networks		Total
Balance at September 30, 2021
Goodwill	$	392,302	$	191,996	$	584,298
Accumulated impairment losses	(167,406)		—		(167,406)
	$	224,896	$	191,996	$	416,892
Balance at September 30, 2020
Goodwill	$	392,302	$	191,996	$	584,298
Accumulated impairment losses	(167,406)		—		(167,406)
	$	224,896	$	191,996	$	416,892

ACCRUED EXPENSES AND OTHER (Tables)

9 Months Ended

Sep. 30, 2021

Payables and Accruals [Abstract]

Schedule of Accrued Expenses

Accrued expenses at September 30, 2021 and December 31, 2020 consisted of the following (in thousands):


	September 30, 2021		December 31, 2020
Employee compensation and related costs	$	38,730	$	66,039



Other	55,291		68,826
	$	94,021	$	134,865

WARRANTY ACCRUALS (Tables)

9 Months Ended

Sep. 30, 2021

Guarantees and Product Warranties [Abstract]

Changes in Accrual Balance

The changes in the Company's accrual balance in the nine months ended September 30, 2021 were as follows (in thousands):






Balance at January 1, 2021	$	14,855

Current period provisions	1,925
Settlements	(4,095)
Balance at September 30, 2021	$	12,685

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVES (Tables)

9 Months Ended

Sep. 30, 2021

Restructuring and Related Activities [Abstract]

Summary of Restructuring Accrual Activity

Restructuring and related expense for the three and nine months ended September 30, 2021 and 2020 was comprised of the following (in thousands):



	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Severance and related costs	$	481	$	1,789	$	3,076	$	8,276
Variable and other facilities-related costs	1,286		$	1,501	4,103		2,380
Accelerated amortization of lease assets due to cease-use	—		$	—	3,368		70
	$	1,767	$	3,290	$	10,547	$	10,726

A summary of the 2020 Restructuring Initiative accrual activity for severance and related costs for the nine months ended September 30, 2021 is as follows (in thousands):


	Balance at January 1, 2021		Initiatives charged to expense		Adjustments for changes in estimate		Cash payments		Balance at September 30, 2021
Severance	$	5,237	$	3,076	$	—	$	(5,921)	$	2,392
Facilities	1,256		473		(670)		(1,059)		—
	$	6,493	$	3,549	$	(670)	$	(6,980)	$	2,392

A summary of the 2019 Restructuring Initiative accrual activity for the nine months ended September 30, 2021 is as follows (in thousands):


	Balance at January 1, 2021		Initiatives charged to expense		Reclassify accelerated amortization to operating lease liabilities		Cash payments		Balance at September 30, 2021
Severance	$	173	$	—	$	—	$	(173)	$	—
Facilities	766		7,668		(3,368)		(3,301)		1,765
	$	939	$	7,668	$	(3,368)	$	(3,474)	$	1,765

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Tables)

9 Months Ended

Sep. 30, 2021

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Impact of Derivative Financial Instrument on Condensed Consolidated Statement of Operations



	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Gain (loss) recognized in other comprehensive income (loss) on derivative (effective portion)	$	30	$	(121)	$	4,905	$	(13,778)
Amount reclassified from accumulated other comprehensive income (loss) to interest expense (effective portion)	830		761		2,419		921
	$	860	$	640	$	7,324	(12,857)

Derivative Liability Designed as a Hedging Instrument


	Balance sheet location	September 30, 2021		December 31, 2020
Interest rate derivative - liability derivative	Accrued expenses and other	$	3,225	$	3,157
Interest rate derivative - liability derivative	Other long-term liabilities	$	399	$	7,791

REVENUE RECOGNITION (Tables)

9 Months Ended

Sep. 30, 2021

Revenue from Contract with Customer [Abstract]

Schedule of Timing of Performance Obligation

The Company's typical performance obligations include the following:

Performance Obligation

When Performance Obligation is Typically Satisfied

When Payment is Typically Due

Software and Product Revenue

Software licenses (perpetual or term)

Upon transfer of control; typically, when made available for download (point in time)

Generally, within 30 days of invoicing except for term licenses, which may be paid for over time

Software licenses (subscription)

Upon activation of hosted site (over time)

Generally, within 30 days of invoicing

Hardware

When control of the hardware passes to the customer; typically, upon delivery (point in time)

Generally, within 30 days of invoicing

Software upgrades

Upon transfer of control; typically, when made available for download (point in time)

Generally, within 30 days of invoicing

Customer Support Revenue

Customer support

Ratably over the course of the support contract (over time)

Generally, within 30 days of invoicing

Professional Services

Other professional services (excluding training services)

As work is performed (over time)

Generally, within 30 days of invoicing (upon completion of services)

Training

When the class is taught (point in time)

Generally, within 30 days of services being performed

Disaggregation of Revenue

The Company's revenue for the three and nine months ended September 30, 2021 and 2020 was disaggregated as follows:



Three months ended September 30, 2021	Product revenue		Service revenue (maintenance)		Service revenue (professional services)		Total revenue
United States	$	47,134	$	33,391	$	12,764	$	93,289


Europe, Middle East and Africa	32,234		19,290		7,971		59,495

Asia Pacific	26,087		10,618		4,215		40,920
Other	6,271		8,371		2,052		16,694
	$	111,726	$	71,670	$	27,002	$	210,398



Three months ended September 30, 2020	Product revenue		Service revenue (maintenance)		Service revenue (professional services)		Total revenue
United States	$	57,503	$	33,275	$	14,072	$	104,850


Europe, Middle East and Africa	41,265		19,720		7,133		68,118

Asia Pacific	22,233		12,208		5,183		39,624
Other	7,925		8,439		2,162		18,526
	$	128,926	$	73,642	$	28,550	$	231,118


Nine months ended September 30, 2021	Product revenue		Service revenue (maintenance)		Service revenue (professional services)		Total revenue
United States	$	140,074	$	97,813	$	35,516	$	273,403


Europe, Middle East and Africa	91,751		59,684		22,622		174,057

Asia Pacific	70,714		31,203		13,886		115,803
Other	20,205		24,112		6,800		51,117
	$	322,744	$	212,812	$	78,824	$	614,380


Nine months ended September 30, 2020	Product revenue		Service revenue (maintenance)		Service revenue (professional services)		Total revenue
United States	$	150,980	$	98,392	$	35,482	$	284,854


Europe, Middle East and Africa	97,431		54,042		15,920		167,393

Asia Pacific	59,030		26,742		14,017		99,789
Other	18,246		24,157		5,154		47,557
	$	325,687	$	203,333	$	70,573	$	599,593


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Indirect sales through channel partner program	$	25,214	$	36,586	$	72,491	$	97,839
Direct sales	86,512		92,340		250,253		227,848
	$	111,726	$	128,926	$	322,744	$	325,687


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Sales to enterprise customers	$	20,034	$	36,937	$	67,225	$	100,168
Sales to service provider customers	91,692		91,989		255,519		225,519
	$	111,726	$	128,926	$	322,744	$	325,687

The Company's product revenue and service revenue components by segment for the three and nine months ended September 30, 2021 and 2020 was as follows (in thousands):


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Product revenue
Cloud and Edge	$	65,587	$	74,860	$	180,100	$	201,380
IP Optical Networks	46,139		54,066		142,644		124,307
Total product revenue	$	111,726	$	128,926	$	322,744	$	325,687

Service revenue
Maintenance
Cloud and Edge	$	56,786	$	57,623	$	169,445	$	171,032
IP Optical Networks	14,884		16,019		43,367		32,301
Total maintenance revenue	71,670		73,642		212,812		203,333
Professional services
Cloud and Edge	20,064		21,047		59,735		56,056
IP Optical Networks	6,938		7,503		19,089		14,517
Total professional services revenue	27,002		28,550		78,824		70,573
Total service revenue	$	98,672	$	102,192	$	291,636	$	273,906

Schedule of Customer Assets and Liabilities

The changes in the Company's accounts receivable, unbilled receivables and deferred revenue balances for the nine months ended September 30, 2021 were as follows (in thousands):


	Accounts receivable		Unbilled accounts receivable		Deferred revenue (current)		Deferred revenue (long-term)
Balance at January 1, 2021	$	179,331	$	58,407	$	96,824	$	26,010
Increase (decrease), net	(17,507)		15,479		(7,271)		(4,392)
Balance at September 30, 2021	$	161,824	$	73,886	$	89,553	$	21,618

OPERATING SEGMENT INFORMATION (Tables)

9 Months Ended

Sep. 30, 2021

Segment Reporting [Abstract]

Schedule of Segment Reporting Information


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Segment revenue:
Cloud and Edge	$	142,437	$	153,530	$	409,280	$	428,468
IP Optical Networks	67,961		77,588		205,100		171,125
Revenue	$	210,398	$	231,118	$	614,380	$	599,593



	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Segment adjusted gross profit:
Cloud and Edge	$	95,998	$	101,910	$	276,170	$	279,624
IP Optical Networks	24,918		35,305		84,544		71,737
Total segment adjusted gross profit	120,916		137,215		360,714		351,361
Stock-based compensation expense	(588)		(261)		(1,412)		(616)
Acquisition-related inventory and facilities adjustments	—		(2,000)		—		(2,000)
Gross profit	$	120,328	$	134,954	$	359,302	$	348,745


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Segment adjusted EBITDA:
Cloud and Edge	$	44,945	$	41,921	$	116,811	$	89,157
IP Optical Networks	(13,240)		1,464		(22,400)		(6,681)
Total segment adjusted EBITDA	31,705		43,385		94,411		82,476
Depreciation	(4,209)		(4,494)		(12,684)		(12,754)
Amortization of intangible assets	(17,221)		(16,349)		(50,225)		(45,352)
Stock-based compensation	(4,561)		(3,969)		(14,411)		(10,167)
Acquisition-related inventory and facilities adjustments	—		(2,000)		—		(2,000)
Litigation costs	—		—		—		(2,101)



Acquisition-, disposal- and integration-related expense	(1,955)		(1,366)		(4,204)		(14,607)
Restructuring and related expense	(1,767)		(3,290)		(10,547)		(10,726)
Income (loss) from operations	1,992		11,917		$	2,340	$	(15,231)

Segment depreciation expense:
Cloud and Edge	$	3,018	$	2,990	$	9,297	$	8,967
IP Optical Networks	1,191		1,504		3,387		3,787
Depreciation expense	$	4,209	$	4,494	$	12,684	$	12,754

MAJOR CUSTOMERS (Tables)

9 Months Ended

Sep. 30, 2021

Risks and Uncertainties [Abstract]

Schedule of Customer Contributing 10% or More of the Revenue

The following customer contributed 10% or more of the Company's revenue in the three and nine months ended September 30, 2021 and 2020:

Three months ended

Nine months ended

September 30,
2021

September 30,
2020

September 30,
2021

September 30,
2020

Verizon Communications Inc.

18%

16%

17%

15%

STOCK-BASED COMPENSATION PLANS (Tables)

9 Months Ended

Sep. 30, 2021

Share-based Payment Arrangement [Abstract]

Schedule of Activity Related to Outstanding Stock Options

The activity related to the Company's outstanding stock options for the nine months ended September 30, 2021 was as follows:


	Number of Shares	Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2021	207,710	$	12.69



Exercised	(13,815)	$	1.76

Expired	(3,686)	$	17.13
Outstanding at September 30, 2021	190,209	$	13.40	2.79	$	171
Vested or expected to vest at September 30, 2021	190,206	$	13.40	2.79	$	171
Exercisable at September 30, 2021	190,121	$	13.41	2.79	$	171

Schedule of Activity Related to Unvested Restricted Stock Grants

The activity related to the Company's RSAs for the nine months ended September 30, 2021 was as follows:


	Shares	Weighted Average Grant Date Fair Value
Unvested balance at January 1, 2021	86,983	$	7.04


Vested	(86,983)	$	7.04

Unvested balance at September 30, 2021	—	$	—

The activity related to the Company's RSUs for the nine months ended September 30, 2021 was as follows:


	Shares	Weighted Average Grant Date Fair Value
Unvested balance at January 1, 2021	6,531,110	$	3.32
Granted	3,109,797	$	8.55

Vested	(3,233,661)	$	3.23
Forfeited	(692,672)	$	4.53
Unvested balance at September 30, 2021	5,714,574	$	6.07

Schedule of Activity Related to Performance Stock Awards

The activity related to the Company's PSUs for the nine months ended September 30, 2021 was as follows:


	Shares	Weighted Average Grant Date Fair Value
Unvested balance at January 1, 2021	6,035,931	$	1.56
Granted	672,121	$	10.22
Vested	(1,525,681)	$	0.98
Forfeited	(193,318)	$	5.89
Unvested balance at September 30, 2021	4,989,053	$	2.90

Schedule of Stock-based Compensation Expenses Which Are Included in Condensed Consolidated Statement of Operations

The condensed consolidated statements of operations include stock-based compensation for the three and nine months ended September 30, 2021 and 2020 as follows (in thousands):


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020
Product cost of revenue	$	96	$	57	$	216	$	123
Service cost of revenue	492		204		1,196		493
Research and development	1,223		868		3,010		2,164
Sales and marketing	1,581		1,189		5,207		2,952
General and administrative	1,169		1,651		4,782		4,435
	$	4,561	$	3,969	$	14,411	$	10,167

LEASES (Tables)

9 Months Ended

Sep. 30, 2021

Leases [Abstract]

Schedule of Right-of-use Lease Assets and Lease Liabilities

The Company's right-of-use lease assets and lease liabilities at September 30, 2021 and December 31, 2020 were as follows (in thousands):


	Classification	September 30, 2021		December 31, 2020
Assets:
Operating lease assets	Operating lease right-of-use assets	$	54,446	$	69,757
Finance lease assets*	Property and equipment, net	416		983
Total leased assets		$	54,862	$	70,740

Liabilities:
Current:
Operating	Operating lease liabilities	$	17,848	$	17,023
Finance	Accrued expenses and other	574		902
Noncurrent:
Operating	Operating lease liabilities, net of current	58,609		72,614
Finance	Other long-term liabilities	159		568
Total lease liabilities		$	77,190	$	91,107

* Finance lease assets were recorded net of accumulated depreciation of $1.6 million and $1.9 million at September 30, 2021 and December 31, 2020, respectively.

Schedule of Components of Lease Expense

The components of lease expense for the three and nine months ended September 30, 2021 and 2020 were as follows (in thousands):


	Three months ended				Nine months ended
	September 30, 2021		September 30, 2020		September 30, 2021		September 30, 2020

Operating lease cost*	$	4,996	$	5,350	$	19,027	$	13,911
Finance lease cost:
Amortization of leased assets	158		291		567		929
Interest on lease liabilities	12		39		58		141
Short-term lease cost	3,327		4,821		9,889		15,945
Variable lease costs (costs excluded from minimum fixed lease payments)**	589		697		3,247		1,969
Sublease income	(510)		(307)		(985)		(871)
Net lease cost	$	8,572	$	10,891	$	31,803	$	32,024

Cash flow information related to the Company's leases for the nine months ended September 30, 2021 and 2020 was as follows (in thousands):


	Nine months ended
		September 30, 2021		September 30, 2020
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases		$	16,509	$	13,933
Operating cash flows for finance leases		$	58	$	141
Financing cash flows for finance leases		$	736	$	971

Other information related to the Company's leases as of September 30, 2021 and December 31, 2020 was as follows:


	September 30, 2021		December 31, 2020
Weighted average remaining lease term (years):
Operating leases	6.44		6.59
Finance leases	1.21		1.70
Weighted average discount rate:
Operating leases	5.64	%	5.67	%
Finance leases	4.36	%	6.15	%

Schedule of Future Minimum Fixed Lease Payments Under Noncancelable Operating Leases

Future minimum fixed lease payments under noncancelable leases at September 30, 2021 were as follows (in thousands):


	September 30, 2021
	Operating		Finance
	leases		leases
Remainder of 2021	$	5,877	$	178
2022	20,496		514
2023	17,712		63
2024	9,741		—
2025	7,733		—
2026 and beyond	31,225		—
Total lease payments	92,784		755
Less: interest	(16,327)		(22)
Present value of lease liabilities	$	76,457	$	733

Schedule of Future Minimum Fixed Lease Payments Under Noncancelable Finance Leases

Future minimum fixed lease payments under noncancelable leases at September 30, 2021 were as follows (in thousands):


	September 30, 2021
	Operating		Finance
	leases		leases
Remainder of 2021	$	5,877	$	178
2022	20,496		514
2023	17,712		63
2024	9,741		—
2025	7,733		—
2026 and beyond	31,225		—
Total lease payments	92,784		755
Less: interest	(16,327)		(22)
Present value of lease liabilities	$	76,457	$	733

BASIS OF PRESENTATION - Narrative (Details) $ in Thousands	3 Months Ended			9 Months Ended
BASIS OF PRESENTATION - Narrative (Details) $ in Thousands	Sep. 30, 2021 USD ($) country	Dec. 31, 2020 USD ($) segment	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) country	Sep. 30, 2020 USD ($)
Product Warranty Liability [Line Items]
Number of countries \| country	35			35
Restricted cash, current	$ 2,543	$ 7,269		$ 2,543
Cash received from the sale of certain accounts receivable	24,800		$ 35,300	88,000	$ 81,100
Interest expense	200		$ 300	600	$ 700
Restricted Short-term Bank Deposits
Product Warranty Liability [Line Items]
Restricted cash, current	$ 2,500			$ 2,500
Restricted cash		2,700
Tax Payment on Certain Fixed Assets
Product Warranty Liability [Line Items]
Restricted cash		$ 4,600
Operating Segments
Product Warranty Liability [Line Items]
Number of operating segments \| segment		2

BASIS OF PRESENTATION - Reclassifications (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue	$ 210,398	$ 231,118	$ 614,380	$ 599,593
Total cost of revenue	90,070	96,164	255,078	250,848
Total gross profit	120,328	134,954	359,302	348,745
Research and development	49,132	49,113	143,339	143,204
Sales and marketing	36,113	36,898	108,212	101,767
General and administrative	12,148	16,021	40,435	48,320
Amortization of acquired intangible assets		16,349		45,352
Acquisition-, disposal- and integration-related	1,955	1,366	4,204	14,607
Restructuring and related	1,767	3,290	10,547	10,726
Total operating expenses	118,336	123,037	356,962	363,976
Income (loss) from operations	1,992	11,917	2,340	(15,231)
Prior presentation
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue		231,118		599,593
Total cost of revenue		107,807		282,395
Total gross profit		123,311		317,198
Research and development		49,113		143,204
Sales and marketing		41,604		115,572
General and administrative		16,021		48,320
Amortization of acquired intangible assets		0		0
Acquisition-, disposal- and integration-related		1,366		14,607
Restructuring and related		3,290		10,726
Total operating expenses		111,394		332,429
Income (loss) from operations		11,917		(15,231)
Amounts reclassified
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue		0		0
Total cost of revenue		(11,643)		(31,547)
Total gross profit		11,643		31,547
Sales and marketing		(4,706)		(13,805)
Amortization of acquired intangible assets		16,349		45,352
Total operating expenses		11,643		31,547
Income (loss) from operations		0		0
Product
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue	111,726	128,926	322,744	325,687
Total cost of revenue	53,494	58,545	144,580	145,103
Product \| Prior presentation
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue		128,926		325,687
Total cost of revenue		70,188		176,650
Product \| Amounts reclassified
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total cost of revenue		(11,643)		(31,547)
Service
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue	98,672	102,192	291,636	273,906
Total cost of revenue	$ 36,576	37,619	$ 110,498	105,745
Service \| Prior presentation
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Total revenue		102,192		273,906
Total cost of revenue		$ 37,619		$ 105,745

BUSINESS ACQUISITION - Narrative (Details) - USD ($) shares in Millions		3 Months Ended	9 Months Ended		12 Months Ended
	Nov. 14, 2019	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Business Acquisition [Line Items]
Net cash consideration			$ 0	$ 346,852,000
Term Loan Facility
Business Acquisition [Line Items]
Commitments from lender	$ 400,000,000
Revolving Credit Facility
Business Acquisition [Line Items]
Commitments from lender	100,000,000
ECI
Business Acquisition [Line Items]
Proceeds from sale of real estate assets	$ 33,400,000
Revenue		$ 77,600,000		171,100,000
Net loss		$ 11,200,000		$ 31,900,000
ECI
Business Acquisition [Line Items]
Common stock to be issued (in shares)	32.5
Fair value of stock issued	$ 108,600,000				$ 108,550,000
Net cash consideration	322,500,000				346,852,000
Repayment of ECI outstanding debt obligations	183,300,000				183,266,000
Payment to selling shareholders	$ 139,200,000				$ 139,244,000
Weighted average useful life of intangible assets (in years)				12 years 4 months 17 days

BUSINESS ACQUISITION - Summary of Preliminary Allocation of Purchase Consideration (Details) - USD ($) $ in Thousands		9 Months Ended		12 Months Ended
	Nov. 14, 2019	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020	Dec. 31, 2019
Cash consideration:
Net cash consideration		$ 0	$ 346,852
Fair value of assets acquired and liabilities assumed:
Goodwill		$ 416,892	$ 416,892	$ 416,892	$ 224,896
ECI
Cash consideration:
Repayment of ECI outstanding debt obligations	$ 183,300			183,266
Cash paid to selling shareholders	139,200			139,244
Payment to selling shareholders from sale of ECI real estate assets				33,400
Less cash and restricted cash acquired				(9,058)
Net cash consideration	322,500			346,852
Fair value of Ribbon stock issued	$ 108,600			108,550
Fair value of total consideration				455,402
Fair value of assets acquired and liabilities assumed:
Current assets, net of cash and restricted cash acquired				120,203
Property and equipment				54,913
Goodwill				191,996
Other noncurrent assets				37,528
Deferred revenue				(4,369)
Other current liabilities				(146,618)
Deferred revenue, net of current				(3,726)
Deferred tax liability				(13,308)
Other long-term liabilities				(46,117)
Fair value of assets acquired and liabilities assumed				455,402
ECI \| In-process research and development
Fair value of assets acquired and liabilities assumed:
Intangible assets				34,000
ECI \| Developed technology
Fair value of assets acquired and liabilities assumed:
Intangible assets				111,900
ECI \| Customer relationships
Fair value of assets acquired and liabilities assumed:
Intangible assets				116,000
ECI \| Trade names
Fair value of assets acquired and liabilities assumed:
Intangible assets				$ 3,000

BUSINESS ACQUISITION - Unaudited Pro Forma Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2020
Business Combination and Asset Acquisition [Abstract]
Revenue	$ 231,118	$ 624,800
Net income (loss)	$ 7,036	$ (41,345)
Diluted earnings (loss) per share (in dollars per share)	$ 0.05	$ (0.29)

BUSINESS ACQUISITION - Summary of Acquisition Related Costs (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Business Combination and Asset Acquisition [Abstract]
Professional and services fees (acquisition-related)	$ 13	$ 1,003	$ 156	$ 14,017
Professional and services fees (disposal-related)	0	0	241	0
Integration-related expenses	1,942	363	3,807	590
Total	$ 1,955	$ 1,366	$ 4,204	$ 14,607

SALE OF KANDY COMMUNICATIONS BUSINESS AND INVESTMENT IN AVCT (Details) $ / shares in Units, $ in Thousands				3 Months Ended	9 Months Ended
	Sep. 08, 2021 shares	Feb. 19, 2021 day $ / shares	Dec. 01, 2020 USD ($) day $ / shares shares	Sep. 30, 2021 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Increase in fair value of investments					$ (64,745)	$ 0
AVCT Investment \| Variable Interest Entity, Not Primary Beneficiary
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Equity interest				25.00%
Disposal Group, Disposed of by Sale, Not Discontinued Operations \| Kandy Communications Business
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Consideration from sale			$ 45,000
Principal amount of debentures			$ 1
Number of warrants acquired (in shares) \| shares			1
Number of shares entitled from warrant (in shares) \| shares			100
Par value of common stock (in dollars per share) \| $ / shares			$ 0.0001
Number of AVCT Units acquired (in shares) \| shares			43,778
Interest rate			10.00%
Debenture, conversion price (in dollars per share) \| $ / shares			$ 3.45
Debenture, stock price trigger (in dollars per share) \| $ / shares		$ 6.00	$ 6.00
Debenture, number of trading days \| day		40	40
Debenture, number of consecutive trading days \| day		60	60
Debt conversion, converted instrument, shares issued (in shares) \| shares	13,700,421
Number of shares of common stock entitled from warrants (in shares) \| shares			4,377,800
Exercise price of warrants (in dollars per share) \| $ / shares			$ 0.01
Fair value of AVCT units			$ 84,900	$ 50,400	50,400		$ 115,200
Fair value of debentures			66,300	38,200	38,200
Fair value of warrants			18,600	12,200	12,200
Net assets sold			$ 1,300
Gain on sale					83,600
Increase in fair value of investments				56,500	68,300
Loss partially offset principal of the debentures				$ 900	$ 3,600

EARNINGS (LOSS) PER SHARE (Details) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Reconciliation of weighted average shares outstanding from basic to diluted
Weighted average shares outstanding—basic (in shares)	148,184	144,948	147,204	136,837
Potential dilutive common shares (in shares)	0	6,732	0	0
Weighted average shares outstanding—diluted (in shares)	148,184	151,680	147,204	136,837
Options
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities not included in computation of diluted loss per share (in shares)	10,900
Options, Restricted and Performance-based Stock and Stock Units
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities not included in computation of diluted loss per share (in shares)		200		13,500

INVENTORY (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Inventory Disclosure [Abstract]
On-hand final assemblies and finished goods inventories	$ 48,176	$ 46,921
Deferred cost of goods sold	1,467	1,165
Gross inventory	49,643	48,086
Less noncurrent portion (included in other assets)	(4,854)	(2,336)
Current portion	$ 44,789	$ 45,750

INTANGIBLE ASSETS AND GOODWILL - Schedule of Intangible Assets and Amortization (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
Intangible Assets And Goodwill
Weighted average amortization period (years)	9 years 2 months 1 day	9 years 2 months 1 day
Cost	$ 614,250	$ 614,250
Accumulated amortization	247,119	196,894
Net carrying value	367,131	417,356
Estimated future amortization expense for intangible assets
Remainder of 2021	16,401
2022	60,449
2023	53,966
2024	46,899
2025	40,338
2026	36,489
Thereafter	112,589
Total	367,131
In-process research and development
Intangible Assets And Goodwill
Cost	34,000	34,000
Accumulated amortization	0	0
Net carrying value	$ 34,000	$ 34,000
Developed technology
Intangible Assets And Goodwill
Weighted average amortization period (years)	7 years 11 months 4 days	7 years 11 months 4 days
Cost	$ 306,380	$ 306,380
Accumulated amortization	172,485	143,050
Net carrying value	$ 133,895	$ 163,330
Customer relationships
Intangible Assets And Goodwill
Weighted average amortization period (years)	11 years 10 months 9 days	11 years 10 months 9 days
Cost	$ 268,140	$ 268,140
Accumulated amortization	70,464	50,627
Net carrying value	$ 197,676	$ 217,513
Trade names
Intangible Assets And Goodwill
Weighted average amortization period (years)	3 years 10 months 17 days	3 years 10 months 17 days
Cost	$ 5,000	$ 5,000
Accumulated amortization	3,440	2,487
Net carrying value	$ 1,560	$ 2,513
Internal use software
Intangible Assets And Goodwill
Weighted average amortization period (years)	3 years	3 years
Cost	$ 730	$ 730
Accumulated amortization	730	730
Net carrying value	$ 0	$ 0

INTANGIBLE ASSETS AND GOODWILL - Schedule of Changes in Carrying Value of Goodwill (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2021
Goodwill [Roll Forward]
Goodwill. beginning of period	$ 224,896
Goodwill, end of period	416,892
Accumulated impairment losses	167,406	$ 167,406
ECI
Goodwill [Roll Forward]
Acquisition	191,996
Cloud and Edge
Goodwill [Roll Forward]
Goodwill. beginning of period	224,896
Goodwill, end of period	224,896
Accumulated impairment losses	167,406	167,406
Cloud and Edge \| ECI
Goodwill [Roll Forward]
Acquisition	0
IP Optical Networks
Goodwill [Roll Forward]
Goodwill. beginning of period	0
Goodwill, end of period	191,996
Accumulated impairment losses	0	$ 0
IP Optical Networks \| ECI
Goodwill [Roll Forward]
Acquisition	$ 191,996

INTANGIBLE ASSETS AND GOODWILL - Schedule of Components of Goodwill (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Goodwill [Line Items]
Goodwill, gross	$ 584,298		$ 584,298
Accumulated impairment losses	(167,406)		(167,406)
Goodwill	416,892	$ 416,892	416,892	$ 224,896
Cloud and Edge
Goodwill [Line Items]
Goodwill, gross	392,302		392,302
Accumulated impairment losses	(167,406)		(167,406)
Goodwill	224,896		224,896	224,896
IP Optical Networks
Goodwill [Line Items]
Goodwill, gross	191,996		191,996
Accumulated impairment losses	0		0
Goodwill	$ 191,996		$ 191,996	$ 0

ACCRUED EXPENSES AND OTHER (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Payables and Accruals [Abstract]
Employee compensation and related costs	$ 38,730	$ 66,039
Other	55,291	68,826
Total accrued expenses	$ 94,021	$ 134,865

WARRANTY ACCRUALS - Changes in Accrual Balance (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at January 1, 2021	$ 14,855
Current period provisions	1,925
Settlements	(4,095)
Balance at September 30, 2021	$ 12,685

WARRANTY ACCRUALS - Narrative (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Guarantees and Product Warranties [Abstract]
Accrued expenses and other	$ 5.8	$ 6.5
Other long-term liabilities	$ 6.9	$ 8.4

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVES - Components of Restructuring Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring and Related Activities [Abstract]
Severance and related costs	$ 481	$ 1,789	$ 3,076	$ 8,276
Variable and other facilities-related costs	1,286	1,501	4,103	2,380
Accelerated amortization of lease assets due to cease-use	0	0	3,368	70
Restructuring and related expense	$ 1,767	$ 3,290	$ 10,547	$ 10,726

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVES - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($) employee	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) employee	Sep. 30, 2020 USD ($) segment employee	Dec. 31, 2020 USD ($)
Restructuring Cost and Reserve [Line Items]
Accelerated amortization of lease assets due to cease-use	$ 0	$ 0	$ 3,368	$ 70
Long-term portion of accrued restructuring	1,800		1,800		$ 800
2020 Restructuring Initiative
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net of adjustments	$ 600	2,900	$ 2,900	$ 8,700
Number of positions eliminated \| employee	10		30	125
Credit offset			$ 670
Restructuring and related cost, expected cost	$ 1,000		1,000
2020 Restructuring Initiative \| Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net of adjustments	500		3,100
Credit offset			0
2020 Restructuring Initiative \| Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net of adjustments	100		500
Credit offset			670
Accelerated amortization of lease assets due to cease-use	200		600
2019 Restructuring Initiative
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net of adjustments	$ 1,200	$ 400	7,700	$ 2,100
Number of positions eliminated \| segment				5
Accelerated amortization of lease assets due to cease-use			3,400
2019 Restructuring Initiative \| Severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net of adjustments				$ 600
2019 Restructuring Initiative \| Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring charges, net of adjustments			4,300	1,500
Accelerated amortization of lease assets due to cease-use			$ 3,400	$ 100

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVES - Restructuring Accrual Activity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Restructuring Reserve [Roll Forward]
Initiatives charged to expense	$ 1,767	$ 3,290	$ 10,547	$ 10,726
Facilities
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			800
Balance at the end of the period	1,800		1,800
2020 Restructuring Initiative
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			6,493
Initiatives charged to expense			3,549
Adjustments for changes in estimate			(670)
Cash payments			(6,980)
Balance at the end of the period	2,392		2,392
2020 Restructuring Initiative \| Severance
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			5,237
Initiatives charged to expense			3,076
Adjustments for changes in estimate			0
Cash payments			(5,921)
Balance at the end of the period	2,392		2,392
2020 Restructuring Initiative \| Facilities
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			1,256
Initiatives charged to expense			473
Adjustments for changes in estimate			(670)
Cash payments			(1,059)
Balance at the end of the period	0		0
2019 Restructuring Initiative
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			939
Initiatives charged to expense			7,668
Reclassify accelerated amortization to operating lease liabilities			(3,368)
Cash payments			(3,474)
Balance at the end of the period	1,765		1,765
2019 Restructuring Initiative \| Severance
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			173
Initiatives charged to expense			0
Reclassify accelerated amortization to operating lease liabilities			0
Cash payments			(173)
Balance at the end of the period	0		0
2019 Restructuring Initiative \| Facilities
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period			766
Initiatives charged to expense			7,668
Reclassify accelerated amortization to operating lease liabilities			(3,368)
Cash payments			(3,301)
Balance at the end of the period	$ 1,765		$ 1,765

DEBT - Credit Facilities (Details)				9 Months Ended
DEBT - Credit Facilities (Details)	Mar. 03, 2021 USD ($)	Aug. 18, 2020 USD ($)	Mar. 03, 2020 USD ($)	Sep. 30, 2021 USD ($)	Dec. 31, 2020 USD ($)	Nov. 14, 2019 USD ($)
2020 Credit Facility
Debt Instrument [Line Items]
Commitments from lender			$ 500,000,000
Repayments of principal in first year			10,000,000
Repayments of principal in year two			20,000,000
Repayments of principal in last year			$ 30,000,000
Default rate percentage			2.00%
Repayments of principal in year three			$ 20,000,000
Repayments of principal in year four			$ 20,000,000
Percentage of consolidated adjusted EBITDA	100.00%	75.00%	100.00%
2020 Credit Facility \| Minimum
Debt Instrument [Line Items]
Consolidated net leverage ratio	2.75	2.25
Borrower's consolidated net leverage ratio	$ 10,000,000	$ 25,000,000
2020 Credit Facility \| Maximum
Debt Instrument [Line Items]
Consolidated net leverage ratio	2.25	2.75
Borrower's consolidated net leverage ratio	$ 25,000,000	$ 10,000,000
Term Loan Facility
Debt Instrument [Line Items]
Commitments from lender						$ 400,000,000
Term Loan Facility \| 2020 Credit Facility
Debt Instrument [Line Items]
Commitments from lender			$ 400,000,000
Outstanding balance				$ 380,500,000	$ 393,100,000
Revolving Credit Facility
Debt Instrument [Line Items]
Commitments from lender						$ 100,000,000
Revolving Credit Facility \| 2020 Credit Facility
Debt Instrument [Line Items]
Commitments from lender			100,000,000
Revolving Credit Facility \| 2020 Credit Facility \| Line of Credit \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		0.00%
Letter of Credit
Debt Instrument [Line Items]
Letters of credit outstanding					$ 5,600,000
Letter of Credit \| 2020 Credit Facility
Debt Instrument [Line Items]
Commitments from lender			30,000,000
Debt interest rate				2.00%	2.50%
Letters of credit outstanding				$ 5,900,000	$ 5,600,000
Swingline Loan \| 2020 Credit Facility
Debt Instrument [Line Items]
Commitments from lender			$ 20,000,000
Term Loan Facility, Term B Loan \| Additional Applicable Margin
Debt Instrument [Line Items]
Basis spread on variable rate		6.50%
Term Loan Facility, Term B Loan \| 2020 Credit Facility
Debt Instrument [Line Items]
Commitments from lender		$ 75,000,000
Repayments of principal in first year		1,000,000
Repayments of principal in year two		8,000,000
Repayments of principal in last year		8,000,000
Repayments of principal in year three		8,000,000
Repayments of principal in year four		8,000,000
Repayments of principal on the maturity date		$ 66,000,000
Premium percentage from voluntary repayment		1.00%
Outstanding balance					$ 74,600,000
Debt interest rate					8.40%
Term Loan Facility, Term B Loan \| 2020 Credit Facility \| LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate		7.50%
Term Loan Facility, Term B Loan \| 2020 Credit Facility \| Prime Rate \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate		0.50%
Term Loan Facility, Term A Loan \| 2020 Credit Facility
Debt Instrument [Line Items]
Commitments from lender		$ 325,000,000
Repayments of principal in first year		10,000,000
Repayments of principal in year two		16,000,000
Repayments of principal in last year		16,000,000
Repayments of principal in year three		16,000,000
Repayments of principal in year four		20,000,000
Repayments of principal on the maturity date		$ 244,000,000
Outstanding balance				$ 380,500,000	$ 318,500,000
Debt interest rate				2.90%	3.40%
Term Loan Facility, Term A Loan \| 2020 Credit Facility \| LIBOR \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		1.50%
Term Loan Facility, Term A Loan \| 2020 Credit Facility \| LIBOR \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate		3.50%
Term Loan Facility, Term A Loan \| 2020 Credit Facility \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate		0.50%
Term Loan Facility, Term A Loan \| 2020 Credit Facility \| Additional Applicable Margin \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate		0.50%
Term Loan Facility, Term A Loan \| 2020 Credit Facility \| Additional Applicable Margin \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate		2.50%
2020 Term Loan
Debt Instrument [Line Items]
Repayments of principal in first year	20,000,000
Repayments of principal in year two	20,000,000
Repayments of principal in last year	300,000,000
Repayments of principal in year three	20,000,000
Repayments of principal in year four	30,000,000
Quarterly principal payment amount	$ 74,600,000
Write off of capitalized debt issuance costs				$ 2,500,000

DEBT - Letters of Credit and Performance and Bid Bonds (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Line of Credit Facility [Line Items]
Cash collateral	$ 2.5	$ 2.7
Various Uncommitted Facilities
Line of Credit Facility [Line Items]
Letters of credit outstanding	24.8	27.0
Letter of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding		5.6
2020 Credit Facility \| Letter of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding	$ 5.9	$ 5.6

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Narrative (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020	Mar. 31, 2020
Derivative [Line Items]
Reclassified as an increase to interest expense over the next twelve months	$ 3,200,000
Interest Rate Swap
Derivative [Line Items]
Notional amount	400,000,000
Interest Rate Swap \| Level Two
Derivative [Line Items]
Interest rate derivative - liability derivative	3,600,000	$ 10,900,000
2020 Credit Facility \| Term Loan Facility
Derivative [Line Items]
Outstanding balance	$ 380,500,000	$ 393,100,000
Principal amount			$ 400,000,000
Fixed rate	0.904%

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Impact of Derivative Financial Instrument on Condensed Consolidated Statement of Operations (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Gain (loss) recognized in other comprehensive income (loss) on derivative (effective portion)	$ 30	$ (121)	$ 4,905	$ (13,778)
Amount reclassified from accumulated other comprehensive income (loss) to interest expense (effective portion)	830	761	2,419	921
Other comprehensive income (loss), cash flow hedge, gain (loss), after reclassification, before tax, parent	$ 860	$ 640	$ 7,324	$ (12,857)

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Fair Values and Locations in the Condensed Consolidated Balance Sheet (Details) - Interest Rate Swap - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Accrued expenses and other
Derivative [Line Items]
Interest rate derivative - liability derivative	$ 3,225	$ 3,157
Other long-term liabilities
Derivative [Line Items]
Interest rate derivative - liability derivative	$ 399	$ 7,791

REVENUE RECOGNITION - Narrative (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Disaggregation of Revenue [Line Items]
Revenue agreement term	1 year
Revenue recognized	$ 81.0	$ 86.0
Customer contract expected life (in years)	5 years
Deferred sales commissions capitalized	$ 4.1		$ 4.1
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Disaggregation of Revenue [Line Items]
Revenue to be recognized	$ 4.0
Revenue, remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Disaggregation of Revenue [Line Items]
Revenue to be recognized	$ 10.0
Revenue, remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Disaggregation of Revenue [Line Items]
Revenue to be recognized	$ 8.0
Revenue, remaining performance obligation, period

REVENUE RECOGNITION - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Disaggregation of Revenue [Line Items]
Total revenue	$ 210,398	$ 231,118	$ 614,380	$ 599,593
Cloud and Edge
Disaggregation of Revenue [Line Items]
Total revenue	142,437	153,530	409,280	428,468
IP Optical Networks
Disaggregation of Revenue [Line Items]
Total revenue	67,961	77,588	205,100	171,125
Product revenue
Disaggregation of Revenue [Line Items]
Total revenue	111,726	128,926	322,744	325,687
Product revenue \| Cloud and Edge
Disaggregation of Revenue [Line Items]
Total revenue	65,587	74,860	180,100	201,380
Product revenue \| IP Optical Networks
Disaggregation of Revenue [Line Items]
Total revenue	46,139	54,066	142,644	124,307
Product revenue \| Sales to enterprise customers
Disaggregation of Revenue [Line Items]
Total revenue	20,034	36,937	67,225	100,168
Product revenue \| Sales to service provider customers
Disaggregation of Revenue [Line Items]
Total revenue	91,692	91,989	255,519	225,519
Product revenue \| Indirect sales through channel partner program
Disaggregation of Revenue [Line Items]
Total revenue	25,214	36,586	72,491	97,839
Product revenue \| Direct sales
Disaggregation of Revenue [Line Items]
Total revenue	86,512	92,340	250,253	227,848
Service
Disaggregation of Revenue [Line Items]
Total revenue	98,672	102,192	291,636	273,906
Service revenue (maintenance)
Disaggregation of Revenue [Line Items]
Total revenue	71,670	73,642	212,812	203,333
Service revenue (maintenance) \| Cloud and Edge
Disaggregation of Revenue [Line Items]
Total revenue	56,786	57,623	169,445	171,032
Service revenue (maintenance) \| IP Optical Networks
Disaggregation of Revenue [Line Items]
Total revenue	14,884	16,019	43,367	32,301
Service revenue (professional services)
Disaggregation of Revenue [Line Items]
Total revenue	27,002	28,550	78,824	70,573
Service revenue (professional services) \| Cloud and Edge
Disaggregation of Revenue [Line Items]
Total revenue	20,064	21,047	59,735	56,056
Service revenue (professional services) \| IP Optical Networks
Disaggregation of Revenue [Line Items]
Total revenue	6,938	7,503	19,089	14,517
United States
Disaggregation of Revenue [Line Items]
Total revenue	93,289	104,850	273,403	284,854
United States \| Product revenue
Disaggregation of Revenue [Line Items]
Total revenue	47,134	57,503	140,074	150,980
United States \| Service revenue (maintenance)
Disaggregation of Revenue [Line Items]
Total revenue	33,391	33,275	97,813	98,392
United States \| Service revenue (professional services)
Disaggregation of Revenue [Line Items]
Total revenue	12,764	14,072	35,516	35,482
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenue	59,495	68,118	174,057	167,393
Europe, Middle East and Africa \| Product revenue
Disaggregation of Revenue [Line Items]
Total revenue	32,234	41,265	91,751	97,431
Europe, Middle East and Africa \| Service revenue (maintenance)
Disaggregation of Revenue [Line Items]
Total revenue	19,290	19,720	59,684	54,042
Europe, Middle East and Africa \| Service revenue (professional services)
Disaggregation of Revenue [Line Items]
Total revenue	7,971	7,133	22,622	15,920
Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenue	40,920	39,624	115,803	99,789
Asia Pacific \| Product revenue
Disaggregation of Revenue [Line Items]
Total revenue	26,087	22,233	70,714	59,030
Asia Pacific \| Service revenue (maintenance)
Disaggregation of Revenue [Line Items]
Total revenue	10,618	12,208	31,203	26,742
Asia Pacific \| Service revenue (professional services)
Disaggregation of Revenue [Line Items]
Total revenue	4,215	5,183	13,886	14,017
Other
Disaggregation of Revenue [Line Items]
Total revenue	16,694	18,526	51,117	47,557
Other \| Product revenue
Disaggregation of Revenue [Line Items]
Total revenue	6,271	7,925	20,205	18,246
Other \| Service revenue (maintenance)
Disaggregation of Revenue [Line Items]
Total revenue	8,371	8,439	24,112	24,157
Other \| Service revenue (professional services)
Disaggregation of Revenue [Line Items]
Total revenue	$ 2,052	$ 2,162	$ 6,800	$ 5,154

REVENUE RECOGNITION - Schedule of Customer Assets & Liabilities (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($)
Accounts receivable
Beginning balance	$ 179,331
Increase (decrease), net	(17,507)
Ending balance	161,824
Unbilled accounts receivable
Beginning balance	58,407
Increase (decrease), net	15,479
Ending balance	73,886
Deferred revenue (current)
Beginning balance	96,824
Increase (decrease), net	(7,271)
Ending balance	89,553
Deferred revenue (long-term)
Beginning balance	26,010
Increase (decrease), net	(4,392)
Ending balance	$ 21,618

OPERATING SEGMENT INFORMATION (Details) $ in Thousands	3 Months Ended		9 Months Ended
OPERATING SEGMENT INFORMATION (Details) $ in Thousands	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($)
Segment Reporting [Abstract]
Number of reportable operating segments \| segment			2
Segment Reporting Information [Line Items]
Total revenue	$ 210,398	$ 231,118	$ 614,380	$ 599,593
Total segment adjusted gross profit	120,916	137,215	360,714	351,361
Stock-based compensation expense	(588)	(261)	(1,412)	(616)
Acquisition-related inventory and facilities adjustments	0	(2,000)	0	(2,000)
Gross profit	120,328	134,954	359,302	348,745
Adjusted EBITDA	31,705	43,385	94,411	82,476
Depreciation	(4,209)	(4,494)	(12,684)	(12,754)
Amortization of intangible assets	(17,221)	(16,349)	(50,225)	(45,352)
Stock-based compensation	(4,561)	(3,969)	(14,411)	(10,167)
Acquisition-related inventory and facilities adjustments	0	(2,000)	0	(2,000)
Litigation costs	0	0	0	(2,101)
Acquisition-, disposal- and integration-related expense	(1,955)	(1,366)	(4,204)	(14,607)
Restructuring and related expense	(1,767)	(3,290)	(10,547)	(10,726)
Income (loss) from operations	1,992	11,917	2,340	(15,231)
Segment depreciation expense:
Depreciation expense	4,209	4,494	12,684	12,754
Cloud and Edge
Segment Reporting Information [Line Items]
Total revenue	142,437	153,530	409,280	428,468
Total segment adjusted gross profit	95,998	101,910	276,170	279,624
Adjusted EBITDA	44,945	41,921	116,811	89,157
Depreciation	(3,018)	(2,990)	(9,297)	(8,967)
Segment depreciation expense:
Depreciation expense	3,018	2,990	9,297	8,967
IP Optical Networks
Segment Reporting Information [Line Items]
Total revenue	67,961	77,588	205,100	171,125
Total segment adjusted gross profit	24,918	35,305	84,544	71,737
Adjusted EBITDA	(13,240)	1,464	(22,400)	(6,681)
Depreciation	(1,191)	(1,504)	(3,387)	(3,787)
Segment depreciation expense:
Depreciation expense	$ 1,191	$ 1,504	$ 3,387	$ 3,787

MAJOR CUSTOMERS (Details) - Customer	3 Months Ended		9 Months Ended		12 Months Ended
MAJOR CUSTOMERS (Details) - Customer	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Revenue \| Verizon Communications Inc.
MAJOR CUSTOMERS
Concentration risk, percentage	18.00%	16.00%	17.00%	15.00%
Accounts Receivable Balance \| One Customer
MAJOR CUSTOMERS
Concentration risk, percentage			16.00%		12.00%

COMMON STOCK REPURCHASES (Details) - USD ($)	4 Months Ended	12 Months Ended
COMMON STOCK REPURCHASES (Details) - USD ($)	Apr. 18, 2021	Dec. 31, 2020	Jun. 30, 2019
Class of Stock [Line Items]
Amount repurchased	$ 0	$ 0
Repurchase Program
Class of Stock [Line Items]
Repurchase amount authorized (up to)			$ 75,000,000
Remaining authorized repurchase amount	$ 70,500,000

STOCK-BASED COMPENSATION PLANS - Narrative (Details) $ / shares in Units, $ in Thousands			3 Months Ended	9 Months Ended		12 Months Ended
	Feb. 26, 2021 shares	Mar. 16, 2020 shares	Sep. 30, 2021 USD ($) $ / shares shares	Sep. 30, 2021 USD ($) performance_period $ / shares shares	Sep. 30, 2020 USD ($)	Dec. 31, 2020 $ / shares shares	Dec. 31, 2019	Jun. 30, 2021 $ / shares	Mar. 31, 2021 $ / shares
Stock-based compensation
Total intrinsic values of stock options exercised (in dollars per share) \| $			$ 0	$ 100
Cash received from the exercise of stock options (in dollars per share) \| $			0	24
Total fair value of restricted stock awards, restricted stock units and performance-based stock units on date vested \| $				38,879	$ 5,551
Fair value of the assumed awards attributable to future stock-based compensation expense \| $			$ 29,300	$ 29,300
Expected period for unrecognized expense				2 years
RSUs
Stock-based compensation
Eligible to vest (in shares)			5,714,574	5,714,574		6,531,110
Granted (in shares)				3,109,797
Grant date fair value (in dollars per share) \| $ / shares			$ 6.07	$ 6.07		$ 3.32
RSUs \| Employee Bonus Program
Stock-based compensation
Percent of target cash bonus of employee				50.00%
Percent reduction of cash target bonus				50.00%
PSUs
Stock-based compensation
Eligible to vest (in shares)			4,989,053	4,989,053		6,035,931
Granted (in shares)				672,121
Grant date fair value (in dollars per share) \| $ / shares			$ 2.90	$ 2.90		$ 1.56
Total fair value of restricted stock awards, restricted stock units and performance-based stock units on date vested \| $				$ 1,500
PSUs \| Bucci Stock Price PSUs
Stock-based compensation
Granted (in shares)				133,333
Performance Shares, Performance Based
Stock-based compensation
Granted percentage				60.00%		60.00%	60.00%
Number of performance periods \| performance_period				3
Percent of performance metrics achieved				200.00%
Vesting percentage				33.33%
Service period				3 years
Performance Shares, Market Based
Stock-based compensation
Granted percentage				40.00%		40.00%	40.00%
Number of performance periods \| performance_period				1
Percent of performance metrics achieved				200.00%
Performance period (in years)				3 years
Grant date fair value (in dollars per share) \| $ / shares									$ 8.65
Performance Shares, Market Based \| Market PSUs
Stock-based compensation
Grant date fair value (in dollars per share) \| $ / shares								$ 13.67
RSAs and RSUs
Stock-based compensation
Total fair value of restricted stock awards, restricted stock units and performance-based stock units on date vested \| $				$ 11,100
Chief Executive Officer \| RSUs
Stock-based compensation
Eligible to vest (in shares)		462,963
Chief Executive Officer \| PSUs
Stock-based compensation
Maximum number of shares to be settled (in shares)		4,750,000
Granted (in shares)	1,333,333

STOCK-BASED COMPENSATION PLANS - Stock Options (Details) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2021 USD ($) $ / shares shares	Dec. 31, 2020 $ / shares
Number of Shares
Outstanding at the beginning of the period (in shares)	207,710
Exercised (in shares)	(13,815)
Expired (in shares)	(3,686)
Outstanding at the end of the period (in shares)	190,209
Vested or expected to vest (in shares)	190,206
Exercisable (in shares)	190,121
Weighted Average Exercise Price
Outstanding (in dollars per share) \| $ / shares	$ 13.40	$ 12.69
Exercised (in dollars per share) \| $ / shares	1.76
Expired (in dollars per share) \| $ / shares	17.13
Vested or expected to vest (in dollars per share) \| $ / shares	13.40
Exercisable (in dollars per share) \| $ / shares	$ 13.41
Weighted Average Remaining Contractual Term (years)
Outstanding	2 years 9 months 14 days
Vested or expected to vest	2 years 9 months 14 days
Exercisable	2 years 9 months 14 days
Aggregate Intrinsic Value (in thousands)
Outstanding (in dollars per share) \| $	$ 171
Vested or expected to vest (in dollars per share) \| $	171
Exercisable (in dollars per share) \| $	$ 171

STOCK-BASED COMPENSATION PLANS - Restricted Stock Awards and Units and Performance-Based Stock Units (Details) - $ / shares	9 Months Ended
	Sep. 30, 2021	Dec. 31, 2020
RSAs
Shares
Unvested balance at the beginning of the period (in shares)	86,983
Vested (in shares)	(86,983)
Unvested balance at the end of the period (in shares)	0
Weighted Average Grant Date Fair Value
Unvested balance (in dollars per share)	$ 0	$ 7.04
Vested (in dollars per share)	$ 7.04
RSUs
Shares
Unvested balance at the beginning of the period (in shares)	6,531,110
Granted (in shares)	3,109,797
Vested (in shares)	(3,233,661)
Forfeited (in shares)	(692,672)
Unvested balance at the end of the period (in shares)	5,714,574
Weighted Average Grant Date Fair Value
Unvested balance (in dollars per share)	$ 6.07	3.32
Granted (in dollars per share)	8.55
Vested (in dollars per share)	3.23
Forfeited (in dollars per share)	$ 4.53
PSUs
Shares
Unvested balance at the beginning of the period (in shares)	6,035,931
Granted (in shares)	672,121
Vested (in shares)	(1,525,681)
Forfeited (in shares)	(193,318)
Unvested balance at the end of the period (in shares)	4,989,053
Weighted Average Grant Date Fair Value
Unvested balance (in dollars per share)	$ 2.90	$ 1.56
Granted (in dollars per share)	10.22
Vested (in dollars per share)	0.98
Forfeited (in dollars per share)	$ 5.89

STOCK-BASED COMPENSATION PLANS - Stock-Based Compensation (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Stock-based compensation
Stock-based compensation	$ 4,561	$ 3,969	$ 14,411	$ 10,167
Product cost of revenue
Stock-based compensation
Stock-based compensation	96	57	216	123
Service cost of revenue
Stock-based compensation
Stock-based compensation	492	204	1,196	493
Research and development
Stock-based compensation
Stock-based compensation	1,223	868	3,010	2,164
Sales and marketing
Stock-based compensation
Stock-based compensation	1,581	1,189	5,207	2,952
General and administrative
Stock-based compensation
Stock-based compensation	$ 1,169	$ 1,651	$ 4,782	$ 4,435

LEASES - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
LEASES - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Lessee, Lease, Description [Line Items]
Additional amortization expense	$ 0	$ 0	$ 3,368	$ 70
Facilities
Lessee, Lease, Description [Line Items]
Accrual for future anticipated variable lease costs	1,800		1,800		$ 800
2020 Restructuring Initiative
Lessee, Lease, Description [Line Items]
Accrual for future anticipated variable lease costs	2,392		2,392		6,493
2020 Restructuring Initiative \| Facilities
Lessee, Lease, Description [Line Items]
Additional amortization expense	200		600
Accrual for future anticipated variable lease costs	0		0		1,256
2019 Restructuring Initiative
Lessee, Lease, Description [Line Items]
Additional amortization expense			3,400
Accrual for future anticipated variable lease costs	1,765		1,765		939
2019 Restructuring Initiative \| Facilities
Lessee, Lease, Description [Line Items]
Additional amortization expense			3,400	$ 100
Expense recorded for estimated future variable lease costs			1,400
Accrual for future anticipated variable lease costs	$ 1,765		$ 1,765		$ 766

LEASES - Assets and Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Assets:
Operating lease assets	$ 54,446	$ 69,757
Finance Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	Property and equipment, net	Property and equipment, net
Finance lease assets	$ 416	$ 983
Total leased assets	54,862	70,740
Current:
Operating	$ 17,848	$ 17,023
Finance Lease, Liability, Current, Statement of Financial Position [Extensible List]	Accrued expenses and other	Accrued expenses and other
Finance	$ 574	$ 902
Noncurrent:
Operating	$ 58,609	$ 72,614
Finance Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	Other long-term liabilities	Other long-term liabilities
Finance	$ 159	$ 568
Total lease liabilities	77,190	91,107
Finance lease, accumulated deprecation	$ 1,600	$ 1,900

LEASES - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Leases [Abstract]
Operating lease, cost	$ 4,996	$ 5,350	$ 19,027	$ 13,911
Finance lease cost:
Amortization of leased assets	158	291	567	929
Interest on lease liabilities	12	39	58	141
Short-term lease cost	3,327	4,821	9,889	15,945
Variable lease costs (costs excluded from minimum fixed lease payments)	589	697	3,247	1,969
Sublease income	(510)	(307)	(985)	(871)
Net lease cost	8,572	10,891	31,803	32,024
Accelerated amortization	600		4,000	100
Variable lease cost accrued	$ 0	$ 0	$ 1,400	$ 0

LEASES - Other Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows for operating leases	$ 16,509	$ 13,933
Operating cash flows for finance leases	58	141
Financing cash flows for finance leases	$ 736	$ 971
Weighted average remaining lease term (years):
Operating leases	6 years 5 months 8 days		6 years 7 months 2 days
Finance leases	1 year 2 months 15 days		1 year 8 months 12 days
Weighted average discount rate:
Operating leases	5.64%		5.67%
Finance leases	4.36%		6.15%

LEASES - Future Minimum Lease Payments (Details) $ in Thousands	Sep. 30, 2021 USD ($)
Operating leases
Remainder of 2021	$ 5,877
2022	20,496
2023	17,712
2024	9,741
2025	7,733
2026 and beyond	31,225
Total lease payments	92,784
Less: interest	(16,327)
Present value of lease liabilities	76,457
Finance leases
Remainder of 2021	178
2022	514
2023	63
2024	0
2025	0
2026 and beyond	0
Total lease payments	755
Less: interest	(22)
Present value of lease liabilities	$ 733

COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	9 Months Ended
COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	Sep. 30, 2021 USD ($)	Nov. 08, 2018 executive	Dec. 31, 2016
Loss Contingencies [Line Items]
Sale of stock grant interest			100.00%
Maximum future royalty commitment	$ 4.3
Maximum future royalty commitment	35.9
Maximum future royalty commitment, interest	$ 1.9
Number of former officers \| executive		3
Minimum
Loss Contingencies [Line Items]
Royalties rates			1.30%
Minimum \| LIBOR
Loss Contingencies [Line Items]
Basis spread on variable rate	1.50%
Maximum
Loss Contingencies [Line Items]
Royalties rates			5.00%
Maximum \| LIBOR
Loss Contingencies [Line Items]
Basis spread on variable rate	2.75%