Leading Japanese Broadband Provider Fuels Growth and Advanced Services with Sonus Networks

CHELMSFORD, Mass., February 28, 2006 - Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider voice over IP (VoIP) infrastructure solutions, today announced that JAPAN TELECOM Co., Ltd., ("JAPAN TELECOM"), one of Japan's largest carriers and a wholly owned subsidiary of SOFTBANK Corp., has selected Sonus' award winning architecture as the foundation for its next generation voice network. Enabling a rich set of broadband applications and services, JAPAN TELECOM's new Sonus-based network significantly expands its market opportunity by facilitating the delivering of innovative new VoIP services across Japan. By selecting Sonus, JAPAN TELECOM will also achieve greater internetworking capabilities with its parent SOFTBANK Corp and will be able to leverage a seamless migration path for future network evolution.

SOFTBANK BB Corp, subsidiary of SOFTBANK Corp began deploying Sonus' industry-leading long distance solution for its voice network in 2003. Based on the success of SOFTBANK BB's Sonus-based VoIP network, JAPAN TELECOM is now building its own packet voice network utilizing Sonus' convergence-enabling architecture. Under the terms of this agreement with JAPAN TELECOM, Sonus is providing its GSX9000TM Open Services Switch, PSXTM Call Routing Engine, SGXTM Signaling Gateway, as well as the Sonus InsightTM  Management System.

“SOFTBANK group has taken a cutting-edge approach to technology, one that has propelled it to a leadership position in the voice over broadband communications industry,” said Hassan Ahmed, chairman and CEO, Sonus Networks. “Broadband voice infrastructure is undoubtedly the future of telecommunication networks. We are very pleased that SOFTBANK's newest subsidiary has turned to Sonus Networks for such a critical component of its voice network. Our infrastructure will enable JAPAN TELECOM to realize its vision of expanding its service offerings and to provide bundled voice, data and multimedia services.”

JAPAN TELECOM was acquired by SOFTBANK Group in July 2004. With a nationwide fiber optic digital network, JAPAN TELECOM is one of the largest service providers in Japan. The company is also growing its substantial international business with its worldwide presence. JAPAN TELECOM provides a wide range of voice and data communications services tailored to suit all needs of corporate, small and medium size enterprises, along with consumers.

“Our corporate mission is to revolutionize lifestyle, work style and business model with our cutting-edge broadband technology. We have decided to build our VoIP network with Sonus because they have consistently proven to provide the highest levels of performance, reliability and scalability, which we require to deliver superior service to our customer,” said Sadahiro Sato, Senior General Manager, Voice Network Division, JAPAN TELECOM. "As we continue to expand our subscriber base and offer more advanced services, the ability to rapidly scale and provide the highest quality level is critical to our success. We rely on Sonus Networks to not only provide us with the industry's leading VoIP infrastructure, but also to provide us with a migration path that will enable us to evolve our network to offer true convergence. Together, our companies will help define next-generation telecommunications in the world's largest VoBB market.”

The Sonus Networks' VoBB solution is deployed in production networks worldwide. Recent research from broadbandtrends.com shows that global broadband penetration accelerated to 194 million subscribers at the end of 3Q05, with VoBB subscribers nearly doubling over the past year to over 19 million. Asia, especially Japan, continues to lead worldwide adoption of VoBB services with nearly 11 million subscribers at the end of 3Q05, representing 57% of the global total.

About JAPAN TELECOM Co., Ltd

JAPAN TELECOM is renowned for its interconnection and partnership with the world's dominant telecom carriers to provide various international services in major areas of the world, such as the U.S.A and Europe where telecommunications demand is strongest. This targeted approach through partnership, provides JAPAN TELECOM's customers with the optimum solutions to their networking needs as they develop their multinational businesses. JAPAN TELECOM continues to be the Best Network Solutions Partner to its customers, providing them with the highest quality services and complete support systems.

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.