Sonus' Industry Leading Interoperability Alliance Testing Center Relocates to Larger Facility to Meet Increased Demand for the Delivery of Multimedia Services Worldwide

CHELMSFORD, Mass. and RICHARDSON, TX, December 6, 2005 – Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider voice over IP (VoIP) infrastructure solutions, today announced the opening of a Richardson operations center, a customer integration and testing facility for Sonus' Open Services Partner Alliance (OSPA), the industry's largest interoperability testing program. The Company has relocated its existing Richardson-based operations center to a larger facility in Richardson's Telecom Corridor® in order to support the growing demand for next generation services, which are increasingly sought after by service providers looking to differentiate themselves with enterprise and consumer customers. The increased capacity will enhance Sonus' ability to extend its industry leadership in the creation, testing, delivery and servicing of today's most innovative end user services, as well as future support of new IMS and wireless applications.

"One of the primary value propositions of today's IP-based voice networks is the ability to rapidly integrate and deploy a wide variety of enhanced services onto the network. The OSPA offers an invaluable service to network operators by streamlining the process of building a next-generation voice network," said Bert Notini, president and COO, Sonus Networks. "The new testing facility offers state-of the art technology to help ensure that Sonus remains the industry frontrunner in innovation and execution."

"Next generation networks are attractive as they bring about an open, standards-based model that allows service providers to build networks that include a multitude of innovative applications, and because of this openness, interoperability is one of the key purchasing criteria today's service providers are using when they make decisions about their network," said Jeff Heynen, Directing Analyst with Infonetics. "Sonus' OSPA program provides a valuable service to the industry by taking the guesswork out of the integration process, and delivering customers total solutions instead of disparate network components."

Today's IP-based networks leverage Session Initiation Protocol (SIP) to integrate enhanced services into the network. Sonus has been deploying networks using SIP for over four years to provide the industry's most extensive IMS-ready portfolio of applications. The OSPA, which tests the SIP capabilities of its members, has been integral in the Company's successful role in some of the industry's most exciting and dynamic networks. Founded in 1999, the OSPA has successfully tested and certified products, applications and services from over 150 partners. The new operations center, which is approximately 30,000 square feet, further extends Sonus' ability to incorporate new offerings into its solutions portfolio.

“Sonus Networks has been a well respected member of our business community for over five years, and we're pleased that they have made the decision to expand their presence in Richardson, a community that is known for the richness of its engineering talent pool,” said Gary Slagel, Mayor, City of Richardson.

“Richardson's Telecom Corridor® attracts highly skilled and accomplished talent in the industry. We're excited to expand our presence in an area recognized as one of the nation's leading technology communities,” said Mike Eastep, vice president of operations, Sonus Networks.

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 Chelmsford, 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 the “Risk Factors” section of Sonus' Annual Report on Form 10-K, dated March 15, 2005, and the “Cautionary Statements” section of Sonus' Quarterly Report on Form 10-Q, dated November 8, 2005, both filed with the SEC, which identify 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 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.