WESTFORD, Mass., May 23, 2007 – Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider Voice over IP (VoIP) infrastructure solutions, announced today that the Company is helping to drive the adoption of applications and services in an IP Multimedia Subsystem (IMS) environment through its participation at the IMS Forum's "IMS Plugfest II", an industry-wide forum designed to foster the interoperability of IMS applications and services for wireless, wireline and cable broadband networks. The IMS Plugfest is sponsored by the IMS Forum (www.imsforum.org), of which Sonus Networks is a founding member. The event will be held June 4-8, 2007 at the University of New Hampshire's Interoperability Lab (IOL).

IMS Plugfest II is designed to enable network operators to capitalize on the promise of IP convergence by helping the IMS Forum develop an industry-recognized "stamp of approval" for IMS applications and services. Sonus Networks, an IMS Plugfest sponsor, will be participating at the event by providing its IMS core network solutions as the reference architecture, and will participate in a series of tests with application vendors. "The first IMS Plugfest held in January went a long way to helping network operators make the distinction between IMS hype and reality," said Vikram Saksena, chief technology officer, Sonus Networks. "This June, we hope to take that a step further by focusing on the application layer of IMS and solidifying the real value associated with migrating legacy solutions to a next generation architecture as robust as IMS."

"Sonus performed exceptionally well in the first IMS Plugfest tests, and we are looking forward to another productive session where the industry’s pioneers come together to advance interoperability of IMS solutions," said Michael Khalilian, IMS Forum President & Chairman and Pervasip Corp. CTO.

Results of IMS Plugfest II will be announced at this year's NXTComm, one of North America's largest premier information and communications trade show events, held in Chicago, IL, June 19-21, 2007. Sonus will be exhibiting at NXTComm in booth #4215. NXTcomm, presented jointly by TIA and USTelecom, is the new industry event uniting the premier information and communications technology suppliers with the world's leading communications and entertainment companies.

About the IMS Forum

The IMS Forum® is a global, non-profit industry association devoted to interoperable IP Multimedia Subsystems services and solutions. IMS Forum’s mission is to accelerate the interoperability of IMS applications and services, enabling enterprise and residential consumers to quickly benefit from the delivery of quadruple play voice, video, internet and mobile services over broadband via cable, wireless and fixed networks. The IMS Forum is the creator and organizer of the IMS Plugfest™, the industry’s only event focused on IMS services interoperability verification and certification.

Through its organized Plugfests, working group interaction, and other activities, forum members are able to develop cost-effective technical frameworks for converged IP services over wireline, cable, 3G, WiFi and WiMAX networks. Plugfest II will be held June 4-8, 2007 at the IMS Forum UNH Interoperability Lab. Plugfest II results will be released at NXTcomm, June 18-21, 2007 at the IMS Forum's booth #3669. For additional information or to join the IMS Forum and the IMS Plugfests, please visit 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 the 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, whether the Company will file its required SEC reports by June 26, 2007 and remain listed on the NASDAQ Global Select Market, 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.

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.