Voice Over Broadband Pioneers Sonus Networks and Vonage Form Alliance to Deliver Next Generation Telephony Service to Consumers

Vonage Expanding VoIP Network with Sonus to Deliver Proven Carrier-Grade Service

CHELMSFORD, Mass., January 04, 2006 - Sonus Networks (Nasdaq: SONS), a leading supplier of service provider voice over IP (VoIP) infrastructure solutions, and Vonage Network, a subsidiary of Vonage Holdings Corp. and the leading provider of broadband telephone services to residential customers in the U.S., announced today that Vonage Network has selected the Sonus Network architecture to support the increasing growth in its subscriber base. Vonage has deployed Sonus solutions including the GSX9000™, PSX™ Call Routing Server, SGX™ Signaling Gateway, and the Sonus Insight™ Management System in New York and Los Angeles and is expanding deployment into additional major markets throughout the United States. In future phases of the network expansion, Vonage plans to broaden the network to international locations.

“Voice over broadband is a technology that's redefining how service providers and consumers alike think about communications,” said Hassan Ahmed, chairman and CEO, Sonus Networks. “From day one, Vonage has been one of the most successful service providers in the industry. By selecting Sonus Networks, Vonage will have the ability to build out a premium network infrastructure to support the rapidly increasing demand for its services.”

“Vonage has been a VoIP pioneer in North America,” said Michael Tribolet, executive vice president of operations for Vonage Network. “Throughout Vonage's history we have remained committed to providing high-quality telephony service. By selecting Sonus, another pioneer in the VoBB market, we are in a position to continue to do this, while rapidly and successfully scaling the size of our network.”

Vonage Network has deployed over 1 million lines throughout its network. The Sonus Network solution provides Vonage with the flexibility, scalability and reliability required to support growth and the addition of new services. Sonus Network IMS-based Voice over Broadband (VoBB) solution, including central components GSX9000™, PSX™ Call Routing Server, SGX™ Signaling Gateway, and the Sonus Insight™ Management System, is proven architecture deployed in some of the world's largest broadband VoIP networks. By enabling network operators to rapidly scale their deployments, the Sonus solution improves the operators' ability to add new revenue-generating subscribers to their network. Additionally, Sonus was a pioneer in the deployment of Session Initiation Protocol (SIP) based voice services, which allows network operators to rapidly integrate applications and solutions from third-party vendors with Sonus products. The ability to seamlessly interoperate offers a key advantage for providers like Vonage that are focused on maintaining and expanding a network that facilitates the delivery of high quality telephony service.

About Vonage^®

Vonage is a pioneer in the broadband phone industry, setting the standard for pricing, features, call quality and reliability for the entire VoIP category. Vonage's award winning service is sold on the web and through national retailers like SAM's Club, RadioShack, Best Buy, Circuit City, Staples, Fry's Electronics, Office Depot and CompUSA. Vonage Holdings Corporation is headquartered in Holmdel, New Jersey. For more information about Vonage's products and services, please visit http://www.vonage.com or call 1-VONAGE-HELP. Vonage® is a trademark of Vonage Marketing, a subsidiary of Vonage Holdings Corp.

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 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. 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.