Frost and Sullivan Names Sonus Technology Leader of the Year

Industry Leading IMS Vendor Receives Award for Achievement in Telecommunications Market; Company Sets Industry Standard for Best-in-Class IP-based Communications Networks

CHELMSFORD, Mass., January 30, 2006 - Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider voice over IP (VoIP) infrastructure solutions, announced today it is the recipient of Frost & Sullivan's 2006 IP Communications Carrier Infrastructure Technology Innovation & Leadership of the Year Award, an award that is presented to the company that has excelled delivering advanced telecommunications solutions to the market, enabling the seamless evolution of voice networks. Sonus provides its industry leading IP infrastructure solutions to some of the world's leading telecom providers, wireless network operators, cable operators, and Internet Service Providers (ISPs).

Frost and Sullivan highlighted several key aspects of Sonus recent achievements in product development, including the expansion of its product line through the introduction of the GSX4000 Gateway, the release of its award-winning IP Multimedia Subsystem (IMS) architecture, as well as the introduction of its IMX Application Platform. The award also recognized Sonus' leadership position in the industry, noting the Company's role in establishing the industry's largest interoperability program, the Sonus Open Services Partner Alliance (OSPA).

“Voice over IP is one of the fastest developing markets in communications today, and Sonus has been at the forefront of innovation since the company's inception. The Company has established one of the most impressive customer portfolios in the industry, has deployed some of the world's largest and most complex communications networks, and has partnered with other market leaders to ensure the delivery of the most robust solutions available today,” said Lynda Starr, Senior Analyst, IP Communications Information & Communication Technology Services, Frost & Sullivan. “The Company's ability to lead the migration to IMS and help network operators deliver exciting new applications with its IMX platform underscore that the pace of innovation at Sonus has not slowed since its first product was delivered almost a decade ago.”

“By delivering the industry's most robust solutions, we are committed to helping network operators solve the business challenges posed by a constantly evolving communications landscape and capitalize on the benefits that a next generation, IP-based architecture can deliver,” said Mike Hluchyj, founder and CTO, Sonus Networks. “We are honored to receive such a distinguished award that acknowledges our ability to lead the market through constant innovation.”

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. Sonus GSX9000 Open Services Switch, PSX Call Routing Server, SGX Signaling Gateway, and the Sonus Insight Management System are trademarks of Sonus Networks, Inc. All other company and product names may be trademarks of the respective companies with which they are associated.