Filed by Sonus Networks, Inc.

Pursuant to Rule 425 under the Securities Act of 1933,

as amended, and deemed filed pursuant to Rule 14a-12

under the Securities Exchange Act of 1934, as amended

Subject Company: Sonus Networks, Inc.

Commission File No.: 001-34115

IMPORTANT ADDITIONAL INFORMATION ABOUT THE TRANSACTION WILL BE FILED WITH THE SEC

In connection with a proposed strategic combination with GENBAND Holdings Company (“GENBAND”) resulting in a new combined company (the “Transaction”), Solstice Sapphire Investments, Inc. (“NewCo”), a wholly-owned subsidiary of Sonus Networks, Inc. (“Sonus”), has filed with the Securities and Exchange Commission (“SEC”) a Registration Statement on Form S-4 that includes a preliminary joint proxy statement of Sonus and GENBAND and certain of its affiliates (the “GENBAND Parties”) and a preliminary prospectus of NewCo, and Sonus and NewCo will file with the SEC other relevant documents concerning the proposed Transaction.  Sonus will mail the definitive joint proxy statement/prospectus to Sonus stockholders and the GENBAND Party equity holders.  SONUS STOCKHOLDERS AND GENBAND PARTY EQUITY HOLDERS ARE URGED TO READ THE REGISTRATION STATEMENT AND JOINT PROXY STATEMENT/PROSPECTUS REGARDING THE PROPOSED TRANSACTION AND ANY OTHER RELEVANT DOCUMENTS FILED WITH THE SEC, AS WELL AS ANY AMENDMENTS OR SUPPLEMENTS TO THOSE DOCUMENTS, BECAUSE THEY CONTAIN IMPORTANT INFORMATION.  Investors and security holders may obtain a free copy of the joint proxy statement/prospectus and other filings containing information about Sonus at the SEC’s website at www.sec.gov.  The joint proxy statement/prospectus and the other filings may also be obtained free of charge from Sonus’ Investor Relations website (http://investors.sonusnet.com/) or by requesting them from Sonus’ corporate secretary at Sonus Networks, Inc., 4 Technology Park Drive, Westford, Massachusetts 01886, Attention: Corporate Secretary.

Sonus, NewCo, the GENBAND Parties and certain of their respective directors and executive officers, under the SEC’s rules, may be deemed to be participants in the solicitation of proxies of Sonus stockholders in connection with the proposed Transaction.  Information about the directors and executive officers of (i) Sonus and their ownership of Sonus common stock and (ii) the GENBAND Parties and their ownership of equity in the applicable GENBAND Party is set forth in the joint proxy statement/prospectus, which is available free of charge as described in the preceding paragraph.

NO OFFERS OR SOLICITATIONS

The attached communications shall not constitute an offer to sell or the solicitation of an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or

qualification of such securities under the securities laws of any such jurisdiction.  No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended.

On August 3, 2017, the following press release was issued by Sonus:

Sonus Networks Reports 2017 Second Quarter Results

August 3, 2017

WESTFORD, Mass. — Sonus Networks, Inc. (Nasdaq: SONS), a global leader in secure and intelligent cloud communications, today announced results for the second quarter ended June 30, 2017.

“We posted a solid second quarter of operating results and finished the first half of 2017 with momentum in several critical areas.  We saw greater contribution from software-based revenue in the second quarter, which led to higher gross margins and stronger financial performance than we expected,” said Raymond Dolan, Sonus president and chief executive officer.  “We had solid bookings and good linearity in the second quarter, and we are off to a strong start in the third quarter.  The large project to cutover a Tier 1 VoLTE network in North America is now carrying live traffic, and we expect it will convert to revenue in the third quarter.  This is another pure software deployment and should contribute to even stronger margins in the second half of the year.”

Financial Highlights

The following table summarizes the consolidated second quarter financial results (in millions, except per share amounts):

Cash and investments were $125.9 million at the end of the second quarter of 2017, compared to $128.8 million at the end of the first quarter of 2017.

(1) Please see the reconciliation of non-GAAP and GAAP financial measures in the press release appendix.

Technology Highlights

·                  Continued to build on our strategy of combining the capabilities of Sonus Session Border Controllers (SBCs) and industry-leading next-generation firewalls (NGFWs) to provide a unified security perimeter for enterprises.

·                  Partnered with Fortinet, Inc. (“Fortinet”) to validate and integrate end-to-end security solutions that protect against real-time data and communication threats, broadening Sonus’ security coalition ecosystem to now include Fortinet and Palo Alto Networks, Inc.

·                  Delivered a release for Sonus’ Policy and Management solutions, providing a consolidated framework for management, session control billing mediation and analytics functions across legacy and next-generation communications networks.  Sonus offers a fully bundled solution to simplify and accelerate customer deployments.

·                  Introduced advanced Network-to-Network Interface (NNI) features for the APAC market and innovative migration capabilities for Microsoft Skype for Business customers.

·                  Continued expanding Sonus’ mobility and signaling solutions with an enhanced user interface for Sonus’ android-based VoWiFi (voice over wifi) client, in addition to new cloud deployment features on Sonus’ Diameter solution.

·                  Announced a new service, Incident Management-as-a-Service (IMaaS).  Working with Sonus partner maintenance and support offerings, this managed service provides expert oversight of Sonus network elements and speeds up the resolution of network anomalies.

·                  The Sonus SBC SWe completed the testing and validation process of the Wind River® Titanium CloudTM ecosystem program.  Sonus and Wind River®, a subsidiary of Intel® Corporation, are collaborating to offer service providers a verified solution for SBC virtualized network function (VNF), delivering carrier-grade performance, availability and reliability.

Industry Recognition

·                  Sonus received Frost & Sullivan’s “2017 North American Enterprise Session Border Controller of the Year” award.

·                  The Sonus SBC portfolio was named a “2016 Network Security Excellence Award” winner by INTERNET TELEPHONY.

Management Comments and Outlook

“We’ve been investing in virtualization for many years, and those investments are now starting to pay off in several strategic engagements.  Our large competitive displacement of the incumbent in a North American Tier 1 has already led to a recent win in Mexico to replace an incumbent SBC supplier with our SBC 7000, which we expect to generate revenue in the fourth quarter.  We are increasingly viewed as a trusted partner as global service providers continue their move to the cloud,” said Dolan.  “On the security front, we announced Fortinet as a second technology partner as we build an ecosystem to define a common network perimeter for securing all flows for the enterprise.  This will contribute to a managed service offering that can be provided by these service providers going forward, with the first one expected to launch commercially in the third quarter.  This progress has been a significant driver in our selection by multiple customers to provide our software-based SBC as a core element of their cloud-based edge architectures.  Additionally, in July we received JITC certification for our software-based SBC (SWe), making Sonus the only SW-based vendor-agnostic SBC on the approved list for government purchasing that provides carrier grade resiliency, scale and functionality.  Taken together these are significant proof points that our R&D investments are driving opportunities to lead in the new software-based architectures in the years ahead.”

Susan Villare, Sonus interim chief financial officer, commented, “Our third quarter outlook is solid.  We anticipate revenue will be between $70 million and $72 million, with GAAP diluted earnings per share between $0.05 and $0.08 and non-GAAP diluted earnings per share between $0.17(1) and $0.20(1).  For the full year, our visibility is less certain as a result of the ongoing trend in customer consolidation.  For example, we now anticipate that the consummation of the merger of two large Tier 1 service providers could result in a reduction in revenue on a year-over-year basis.  Accordingly, our full year revenue outlook no longer supports year-over-year growth and we are now revising our outlook for full year revenue to be flat to a low single-digit percentage decline compared to 2016.  We expect our GAAP loss per share will approximate $0.46(2) and our non-GAAP diluted earnings per share will be $0.26(1),(2).”

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(1) Please see the reconciliation of non-GAAP and GAAP financial measures in the press release appendix.

(2) GAAP loss per share assumes a basic share count of 49.5 million; non-GAAP diluted earnings per share assumes a share count of 50.0 million.

Q317 Guidance

The Company’s guidance is based on current indications for its business, which are subject to change.  Gross margin, operating expenses and diluted earnings per share are presented on both a GAAP and non-GAAP basis.  A reconciliation of the non-GAAP to GAAP guidance and a statement on the use of non-GAAP financial measures are included at the end of this press release.  Please note that the guidance for Q317 and FY17 included in this press release does not include the potential impact of the proposed merger with GENBAND, with the exception of forecasted acquisition-related expenses.

(1) Please see the reconciliation of non-GAAP and GAAP financial measures in the press release appendix.

Conference Call Details

Date: Thursday, August 3, 2017

Time: 8:30 a.m. (ET)

Dial-in number: 800-707-9445

International Callers: +1-303-223-2698

The Company will offer a live, listen-only webcast of the conference call via Sonus’ Investor Relations page at http://investors.sonusnet.com/events.cfm in which supporting materials, including a presentation and supplemental financial and operational data, will be posted.

Replay Information

An archived version of the broadcast will be available on Sonus’ Investor Relations page shortly after the conclusion of the live event.  A telephone playback will be available following the conference call until August 17, 2017 and can be accessed by calling 800-633-8284 or +1-402-977-9140 for international callers. The reservation number for the replay is 21854546.

Upcoming Third Quarter 2017 Investor Conferences and Meetings

·                  August 8, 2017 — The Oppenheimer 20th Annual Technology, Internet & Communications Conference, Four Seasons Hotel, Boston

·                  August 15, 2017 — DA Davidson 9th Annual Technology Forum, Roosevelt Hotel, New York City

·                  August 29, 2017 — Jefferies 2017 Semiconductor, Hardware and Communications Infrastructure Summit, Ritz Carlton, Chicago

·                  September 6, 2017 — Drexel Telecom, Media & Technology Conference, W Hotel, New York City

Sonus/GENBAND Merger Highlights

·                  On May 23, 2017, Sonus and GENBAND Holdings Company (“GENBAND”) announced a merger to create a global leader in next-generation communications networking, with increased scale and market reach across products, customers and geographies.  GENBAND is a leading provider of carrier and enterprise network transformation and real-time communications solutions.

·                  Sonus and GENBAND shareholders will each own approximately 50% of the combined company.

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·                  The two companies’ combined 2016 revenue was approximately $680 million and EBITDA was approximately $50 million.

·                  Enhanced scale and geographic reach and highly complementary product portfolios are expected to enable expanded market opportunities to accelerate growth.

·                  The Chief Executive Officer and Chief Financial Officer of the combined company will be Ray Dolan (from Sonus) and Daryl Raiford (from GENBAND), respectively.

·                  Sonus expects that the special meeting of stockholders to vote on the merger and the consummation of the merger, if approved, will occur in the second half of 2017.

Additional Resources

·                  Read more about the proposed Sonus Networks/GENBAND merger at https://www.rtcleaders.com/

·                  Access S-4 filing at http://investors.sonusnet.com/sec.cfm

About Sonus Networks

Sonus brings intelligence and security to real-time communications.  By helping the world embrace the next generation of cloud-based SIP and 4G/LTE solutions, Sonus enables and secures latency-sensitive, mission critical traffic for VoIP, video, instant messaging and online collaboration.  With Sonus, enterprises can give priority to real-time communications based on smart business rules while service providers can offer reliable, comprehensive and secure on-demand network services to their customers.  With solutions deployed in more than 100 countries and nearly two decades of experience, Sonus offers a complete portfolio of hardware-based and virtualized session border controllers (SBCs), diameter signaling controllers (DSCs), policy/routing servers, network intelligence applications, media and signaling gateways and network analytics tools.  For more information, visit www.sonus.net or call 1-855-GO-SONUS.

Important Information Regarding Forward-Looking Statements

This press release contains “forward-looking statements” within the meaning of the U.S. Private Securities Litigation Reform Act of 1995, which are subject to a number of risks and uncertainties.  All statements other than statements of historical facts contained in this release, including statements made by our executive officers in the introductory paragraph and the section “Management Comments and Outlook,” statements in the sections “Q317 Guidance” and “Sonus/GENBAND Merger Highlights,” statements regarding our future results of operations and financial position, business strategy, strategic position, statements about the completion, timing and impact of the transactions described herein, plans and objectives of management for future operations, plans for future cost reductions and plans for future product development and manufacturing are forward-looking statements.  Without limiting the foregoing, the words “anticipates”, “believes”, “could”, “estimates”, “expects”, “expectations”, “intends”, “may”, “plans”, “seeks”, “projects” and other similar language, whether in the negative or affirmative, are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words.

Forward-looking statements are based on our current expectations and assumptions regarding our business, the economy and other future conditions.  Because forward-looking statements relate to the future, they are subject to inherent uncertainties, risks and changes in circumstances that are difficult to predict.  Our actual results could differ materially from those anticipated in these forward-looking statements as a result of various factors, including, but not limited to, the timing of customer purchasing decisions and our recognition of revenues; economic conditions; our ability to recruit and retain key personnel; difficulties supporting our strategic focus on channel sales; difficulties retaining and expanding our customer base; difficulties leveraging market opportunities; the impact of restructuring and cost-containment activities; the timing and impact of our proposed transaction with GENBAND; our ability to realize benefits from the acquisitions that we have completed; the effects of disruption from the acquisitions that we have completed, making it more difficult to maintain relationships with employees, customers, business partners or government entities; the success implementing the integration strategies with respect to acquisitions; litigation; actions taken by significant stockholders; difficulties providing solutions that meet the needs of customers; market acceptance of our products and services; rapid technological and market change; our ability to protect our intellectual property rights; our ability to

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maintain partner, reseller, distribution and vendor support and supply relationships; higher risks in international operations and markets; the impact of increased competition; currency fluctuations; changes in the market price of our common stock; and/or failure or circumvention of our controls and procedures.  These statements involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements.

This release also contains statements about our agreement to effect a strategic combination with GENBAND resulting in a new combined company (“NewCo”) (collectively, the “Transaction”).  Many risks and uncertainties could cause actual results to differ materially from these forward-looking statements with respect to the Transaction, and these risks, as well as other risks associated with the proposed merger, are more fully disclosed in the joint proxy statement/prospectus that is included in the initial registration statement on Form S-4 (File No. 333-219008) that was filed with the U.S. Securities and Exchange Commission (the “SEC”) in connection with the proposed merger.

We caution you against relying on any of these forward-looking statements.  Important factors that could cause actual results to differ materially from those in these forward-looking statements are discussed in Part II, Item 1A. “Risk Factors”, Part I, Item 2. “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and Part I, Item 3 “Quantitative and Qualitative Disclosures About Market Risk” in the Company’s most recent Quarterly Report on Form 10-Q.  Any forward-looking statement made by us in this release speaks only as of the date of this release.  Factors or events that could cause our actual results to differ may emerge from time to time, and it is not possible for us to predict all of them.  We undertake no obligation to publicly update any forward-looking statement, whether as a result of new information, future developments or otherwise, except as may be required by law.

Sonus is a registered trademark of Sonus Networks, Inc.  All other Company and product names may be trademarks of the respective companies with which they are associated.

IMPORTANT ADDITIONAL INFORMATION ABOUT THE TRANSACTION WILL BE FILED WITH THE SEC

In connection with the proposed transaction, NewCo has filed with the SEC a Registration Statement on Form S-4 that includes a preliminary joint proxy statement of Sonus and GENBAND and certain of its affiliates (the “GENBAND Parties”) and a preliminary prospectus of NewCo, and Sonus and the parties will file with the SEC other relevant documents concerning the proposed transaction.  Sonus will mail the definitive joint proxy statement/prospectus to Sonus stockholders and the GENBAND Party equity holders.  SONUS STOCKHOLDERS AND GENBAND PARTY EQUITY HOLDERS ARE URGED TO READ THE REGISTRATION STATEMENT AND JOINT PROXY STATEMENT/PROSPECTUS REGARDING THE PROPOSED TRANSACTION AND ANY OTHER RELEVANT DOCUMENTS FILED WITH THE SEC, AS WELL AS ANY AMENDMENTS OR SUPPLEMENTS TO THOSE DOCUMENTS, BECAUSE THEY CONTAIN IMPORTANT INFORMATION.  Investors and security holders may obtain a free copy of the joint proxy statement/prospectus and other filings containing information about Sonus at the SEC’s website at www.sec.gov.  The joint proxy statement/prospectus and the other filings may also be obtained free of charge from Sonus’ Investor Relations website (http://investors.sonusnet.com/) or by requesting them from Sonus’ corporate secretary at Sonus Networks, Inc., 4 Technology Park Drive, Westford, Massachusetts 01886, Attention: Corporate Secretary.

Sonus, NewCo, the GENBAND Parties and certain of their respective directors and executive officers, under the SEC’s rules, may be deemed to be participants in the solicitation of proxies of Sonus stockholders in connection with the proposed transaction.  Information about the directors and executive officers of (i) Sonus and their ownership of Sonus common stock and (ii) the GENBAND Parties and their ownership of equity in the applicable GENBAND Party is set forth in the joint proxy statement/prospectus.

Free copies of this document may be obtained as described in the preceding paragraphs.

NO OFFERS OR SOLICITATIONS

This communication shall not constitute an offer to sell or the solicitation of an offer to sell or the solicitation of an offer to buy any securities, nor shall there be any sale of securities in any jurisdiction in

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which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction.  No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended.

Discussion of Non-GAAP Financial Measures

Sonus management uses several different financial measures, both GAAP and non-GAAP, in analyzing and assessing the overall performance of the business, making operating decisions, planning and forecasting future periods, and determining payments under compensation programs.  Our annual financial plan is prepared both on a GAAP and non-GAAP basis, and the non-GAAP annual financial plan is approved by our board of directors.  Continuous budgeting and forecasting for revenue and expenses are conducted on a non-GAAP basis (in addition to GAAP) and actual results on a non-GAAP basis are assessed against the annual financial plan.  We consider the use of non-GAAP financial measures helpful in assessing the core performance of our continuing operations and liquidity, and when planning and forecasting future periods.  By continuing operations, we mean the ongoing results of the business excluding certain expenses and credits, including, but not limited to: stock-based compensation, amortization of intangible assets, patent litigation settlement expense, acquisition-related expense, restructuring, certain gains and losses included in other income (expense) and deferred income tax adjustments.  We consider the use of non-GAAP earnings (loss) per share helpful in assessing the performance of the continuing operations of our business.  While our management uses non-GAAP financial measures as a tool to enhance their understanding of certain aspects of our financial performance, our management does not consider these measures to be a substitute for, or superior to, GAAP measures.  In addition, our presentations of these measures may not be comparable to similarly titled measures used by other companies.  These non-GAAP financial measures should not be considered alternatives for, or in isolation from, the financial information prepared and presented in accordance with GAAP.

Investors are cautioned that there are material limitations associated with the use of non-GAAP financial measures as an analytical tool.  In particular, many of the adjustments to Sonus’ financial measures reflect the exclusion of items that are recurring and will be reflected in our financial results for the foreseeable future.

Stock-based compensation is different from other forms of compensation, as it is a non-cash expense.  For example, a cash salary generally has a fixed and unvarying cash cost.  In contrast, the expense associated with an equity-based award is generally unrelated to the amount of cash ultimately received by the employee, and the cost to us is based on a stock-based compensation valuation methodology and underlying assumptions that may vary over time.  We believe that excluding non-cash stock-based compensation expense from our operating results facilitates the comparison of our financial statements to our historical operating results and to other companies in our industry.

We exclude the amortization of acquired intangible assets from non-GAAP expense and income measures.  These amortization amounts are inconsistent in frequency and amount and are significantly impacted by the timing and size of acquisitions.  Although we exclude amortization of acquired intangible assets from our non-GAAP expenses, we believe that it is important for investors to understand that intangible assets contribute to revenue generation.  We believe that excluding the non-cash amortization of intangible assets facilitates the comparison of our financial results to our historical operating results and to other companies in our industry as if the acquired intangible assets had been developed internally rather than acquired.

In June 2016, we recorded $0.6 million of patent litigation settlement costs.  This amount is included as a component of General and administrative expense; however, we believe that such patent litigation settlement costs are not part of our core business or ongoing operations.  Accordingly, we believe that excluding this patent litigation settlement expense facilitates the comparison of our financial results to our historical operating results and to other companies in our industry.

We consider certain transition, integration and other acquisition-related costs to be unpredictable and dependent on a significant number of factors that may be outside of our control.  We do not consider these acquisition-related costs to be related to the continuing operations of the acquired business or the Company.  In addition, the size, complexity and/or volume of an acquisition, which often drives the

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magnitude of acquisition-related costs, may not be indicative of such future costs.  We believe that excluding acquisition-related costs facilitates the comparison of our financial results to our historical operating results and to other companies in our industry.

We have recorded restructuring expense to streamline operations and reduce operating costs by closing and consolidating certain facilities and reducing our worldwide workforce.  We review our restructuring accruals regularly and record adjustments (both expense and credits) to these estimates as required.  We believe that excluding restructuring expense and credits facilitates the comparison of our financial results to our historical operating results and to other companies in our industry, as there are no future revenue streams or other benefits associated with these costs.

In May 2017, we sold a block of IP addresses that we had acquired in connection with our acquisition of Network Equipment Technologies, Inc. and recognized a gain, net of commission and fees, of $0.6 million.  This amount is included as a component of Other income, net, in the three and six months ended June 30, 2017.  We believe that such gains are not part of our core business or ongoing operations.  Accordingly, we believe that excluding the other income arising from this sale facilitates the comparison of our financial results to our historical results and to other companies in our industry.

We anticipate that we will reverse $0.7 million of deferred tax assets related to net operating loss carryforwards for our subsidiary in Canada based on positive earnings evidence in the subsidiary over a consecutive three-year period.  This adjustment will result in an income tax credit and reduce our provision in the reversal period.  We believe that such adjustments are not part of our core business or ongoing operations.  Accordingly, we believe that excluding the income tax credit arising from the reversal of the deferred tax assets facilitates the comparison of our financial results to our historical results and to other companies in our industry.

We believe that providing non-GAAP information to investors, in addition to the GAAP presentation, will allow investors to view the financial results in the way management views the operating results.  We further believe that providing this information helps investors to better understand our financial performance and evaluate the efficacy of the methodology and information used by our management to evaluate and measure such performance.

For More Information

Sara Leggat

(978) 614-8841

sleggat@sonusnet.com

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SONUS NETWORKS, INC.

Condensed Consolidated Statements of Operations

(in thousands, except percentages and per share amounts)

(unaudited)

SONUS NETWORKS, INC.

Condensed Consolidated Statements of Operations

(in thousands, except percentages and per share amounts)

(unaudited)

SONUS NETWORKS, INC.

Condensed Consolidated Balance Sheets

(in thousands)

(unaudited)

SONUS NETWORKS, INC.

Condensed Consolidated Statements of Cash Flows

(in thousands)

(unaudited)

SONUS NETWORKS, INC.

Supplemental Information

(In thousands)

(unaudited)

The following tables provide the details of stock-based compensation, amortization of intangible assets, a patent litigation settlement and the gain on the sale of IP address blocks included in the Company’s Statements of Operations and the line items in which these amounts are reported.

SONUS NETWORKS, INC.

Supplemental Information

(In thousands)

(unaudited)

The following tables provide the details of stock-based compensation, amortization of intangible assets, a patent litigation settlement and the gain on the sale of IP address blocks included in the Company’s Statements of Operations and the line items in which these amounts are reported.

SONUS NETWORKS, INC.

Reconciliation of Non-GAAP and GAAP Financial Measures - Historical

(in thousands, except percentages and per share amounts)

(unaudited)