Largest Japanese PHS Network Operator taps Sonus Solutions for Cost-Effective Converged Services

CHELMSFORD, Mass., January 10, 2006 - Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider voice over IP (VoIP) infrastructure solutions, announced today that WILLCOM, Inc., a major Japanese provider of wireless data and voice services and the largest operator employing Personal Handyphone System (PHS) technology in Japan, has selected Sonus Networks as the foundation for its new nationwide long-distance network to support WILLCOM's PHS system.

This agreement marks the development of Japan's largest VoIP network for PHS subscribers. WILLCOM will utilize key components of the Sonus solution including the GSX9000 Open Services Switch, the PSX™ Call Routing Server, and the Sonus Insight™ Management System, which includes the Element Management System (EMS).

"We chose the Sonus solution because the company has established a proven track record of providing cost-effective, scalable and reliable carrier-grade solutions here in Japan. We are fully confident in Sonus as they have the long-distance VoIP deployments in Japan to their name," said Mr Yoshiki Chika, CTO, WILLCOM, Inc. "This new network gives WILLCOM the flexibility to extend our portfolio to next generation services and enhance customer loyalty and satisfaction while reducing network costs."

"Sonus recognized the potential of the Asia-Pacific market early-on and has been developing solutions that are designed specifically for operators in this region," said Hassan Ahmed, chairman and CEO, Sonus Networks. "Japanese operators have been among the first to embrace the enormous potential of VoIP not only for delivering cost-effective solutions, but also to provide innovative new features to consumers. WILLCOM is one of the first wireless operators in Japan to leverage the benefits of VoIP in their networks. We are proud to be partnering with this dynamic operator for their network expansion.

This latest collaboration with WILLCOM underscores Sonus' position at the forefront of one of the world's most competitive VoIP markets. Sonus has garnered a leadership position in the Japanese market, with total media gateway market share of 61.1% and more than 80% of the high density media gateway industry in the third quarter, according to a report by Synergy Research Group.

"The demand for voice over IP services in Japan is on the rise. Sonus has demonstrated its commitment to the Japanese market with large-scale deployments underway at nearly all of the major operators, and we are excited to be extending our reach into the wireless market,” said Takayuki Oshima, President, Sonus Networks Japan. “By leveraging Sonus' experience in the Japanese market and the Company's technical expertise in converged networks, WILLCOM will be able to deliver voice services to its customers that meet its requirements for scalability and reliability.”

About WILLCOM, Inc.

WILLCOM, Inc. is a leading mobile data telecommunications company, providing PHS services in Japan. In addition to data telecommunications, WILLCOM introduced the “WILLCOM Flat-Rate Plan” in May 2005, the industry's first fixed-rate voice communication service. WILLCOM has also introduced a series of other new services to the market, and currently has more than 3.56 million cumulative subscribers (as of November 2005). For more information (available in English and Japanese), visit WILLCOM's website at http://www.willcom-inc.com/.

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 of U.S. 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 August 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. The Sonus GSX9000, PSX Call Routing Server, SGX Signaling Gateway, and the Sonus Insight Management System are all trademarks of Sonus Networks. All other company and product names may be trademarks of the respective companies with which they are associated.