IMS Plugfest Showcases Sonus' Ability to Deliver IMS-Ready Services

WESTFORD, Mass., February 1, 2007 - Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider Voice over IP (VoIP) infrastructure solutions, announced today that the first IMS Forum Plugfest™, hosted by the IMS Forum (www.IMSForum.org) and held last week at the University of New Hampshire InterOperability Lab in Durham, N.H., demonstrated the strength of Sonus' IP Multimedia Subsystem (IMS)-ready solutions. Sonus Networks participated in all of the Plugfest's rigorous tests, which validated the interoperability capabilities of Sonus' IMS-ready core trunking solution. Sonus' leadership in IMS is a critical advantage as network operators globally deploy IP-Voice solutions that comply with emerging IMS standards to deliver next-generation services.

“Sonus IMS solution moves the industry beyond the hype to actual deployments that reduce costs and provide a platform for the rollout of advanced services,” said Steve Edwards, Chief Marketing Officer, Sonus Networks. “Plugfest is one of the industry's first forums that depicts the real value of IMS. Sonus showcased the value of IMS during this groundbreaking testing session and is very pleased to have demonstrated the breadth and strength of the Sonus IMS solution in an open testing environment.”

The IMS Plugfest included tests of multi-vendor 3GPP environments, multi-domain VoIP calls, and integrated SIP Application Servers with multiple IMS cores. The tests accessed the Sonus IMS-ready core trunking solution, which is comprised of Sonus' GSX™ Open Services Switch for Media Gateway Control Function/Media Gateway (MGCF/MGW), the SGX™ Signaling Gateway, and the PSX™ Breakout Gateway Control Function (BGCF). The Sonus HSX Home Subscriber Server (HSS) and the SRX Call Session Control Function (S-CSCF) forming the IMS SIP core were used in all test cases. Sonus was the only vendor to demonstrate complete Public Switch Telecom Network (PSTN) inter-working capabilities and was the only vendor to supply a commercially-available HSS based on open standards.

The Sonus IMS-based solution tested at the Plugfest is the same platform currently available for deployment in customer networks today. The solution provides multiple real-world benefits in the immediate-term, such as its sophisticated traffic management and routing policies, while providing the foundation needed to support the development of future IMS-enabled services and applications.

“The exciting promise of IMS is the ability for network operators to deliver innovative, revenue-generating, next generation services such as presence-enabled and location-based services, video on demand, and fixed-mobile convergence. To get to that point, though, we first must have a core reference architecture that embraces the principles of IMS to create a seamless multi-vendor environment,” said Michael Khalilian, IMS Forum President & Chairman and Pervasip Corp. CTO. “The IMS Plugfest was a breakthrough event in terms of putting IMS products to the test and accelerating the adoption of IMS-based solutions industry-wide.”

Additional Plugfest events are scheduled for Q2 2007, and will focus on multimedia services in an IMS environment. More information is available at www.IMSForum.org.

About Sonus Networks

Sonus Networks, Inc. is a leading provider of voice over IP (VoIP) infrastructure solutions for wireline and wireless service providers. With its comprehensive IP Multimedia Subsystem (IMS) solution, Sonus addresses the full range of carrier applications, including residential and business voice services, wireless voice and multimedia, trunking and tandem switching, carrier interconnection and enhanced services. Sonus' voice infrastructure solutions are deployed in service provider networks worldwide. Founded in 1997, Sonus is headquartered in Westford, Massachusetts. Additional information on Sonus is available at http://www.sonusnet.com.

This release may contain forward-looking statements regarding future events that involve risks and uncertainties. Readers are cautioned that these forward-looking statements are only predictions and may differ materially from actual future events or results. Readers are referred to Item 1A “Risk Factors” of Sonus' Quarterly Report on Form 10-Q dated May 8, 2006, filed with the SEC, which identifies important risk factors that could cause actual results to differ from those contained in the forward-looking statements. Risk factors include among others: the impact of material weaknesses in our disclosure controls and procedures and our internal control over financial reporting on our ability to report our financial results timely and accurately; the unpredictability of our quarterly financial results; risks and uncertainties associated with the Company's announced review of its historical stock option grants and accounting, including any potential impact on the Company's financial statements or results, any tax liabilities or penalties, the Company's inability to timely report with the Securities and Exchange Commission, the Company's potential inability to meet NASDAQ requirements for continued listing, potential investigations, regulatory actions or litigation arising out of the review or any restatement; risks associated with our international expansion and growth; consolidation in the telecommunications industry; and potential costs resulting from pending securities litigation against the company. Any forward-looking statements represent Sonus' views only as of today and should not be relied upon as representing Sonus' views as of any subsequent date. While Sonus may elect to update forward-looking statements at some point, Sonus specifically disclaims any obligation to do so.

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