SUPERCOMM 2001 BOOTH #2312

Partnership with Leading Integrator Expands Sonus' Reach In Japan

WESTFORD, Mass., June 4, 2001 – Sonus Networks (Nasdaq: SONS), a leading provider of voice infrastructure solutions for the new public network, today announced that it has formed a distribution relationship with Sumitomo Corporation. Under this non-exclusive agreement, Sumitomo will provide the full range of Sonus packet voice products to the Japanese carrier market, including Sonus' award-winning GSX9000 Open Services Switch, the PSX6000 SoftSwitch, the INtelligentIP Softswitch, the SGX2000 SS7 Signaling Gateway, and the Sonus Insight Element Management System. "Japan is considered one of the more technologically innovative and rapidly growing of the world's telecommunications markets," said Gary Rogers, vice president, worldwide sales, Sonus Networks. "We look forward to working closely with Sumitomo to help Japanese carriers in building out the next-generation packet voice networks that will enable them to compete more effectively in the global market."

"Sonus is clearly recognized as the worldwide market leader in carrier-class packet voice solutions, and its range of solutions delivers clear advantages over other alternatives available today," said Yoshio Osawa, general manager of network systems department, Sumitomo Corporation. "By offering Sonus' voice infrastructure solutions, we will enable our carrier customers to enhance their businesses through the rapid development and delivery of highly competitive new services, while also significantly reducing their ongoing network operations costs."

About Sumitomo Corporation

Sumitomo Corporation (http://www.sumitomocorp.co.jp) is one of the world's leading traders and distributors of commodities, industrial goods, and consumer goods. Besides its role as a trader, Sumitomo Corporation is increasingly active as an investor in a diverse range of businesses that integrate with existing operations, or that position the company in markets with long-term potential. Sumitomo Corporation is also a major dominant player in the Japanese IT/media market, with strategic investments and affiliations including the largest leading CATV operation, Jupiter Telecom, a joint venture with Liberty Media; Jupiter Programming, a content provider for CATV and other digital broadcasting; @Home-Japan, a joint venture with Excite@Home; and, provides system integration service for next generation networking equipment. Sumitomo Corporation has a staff of 8,192 throughout Japan and in 88 other countries. Total trading transaction in 2000 was $103Bil.

About Sonus Networks

Sonus Networks, Inc. is a leading provider of voice infrastructure products for the new public network. Sonus' solutions enable service providers to deploy an integrated network capable of carrying both voice and data traffic, and to deliver a range of innovative, new services. The Sonus Open Services Architecture (OSA) and award-winning Packet Telephony suite cut the time-to-market for competitive new service products, allowing carriers and third-party developers to expand market share and build important new revenue streams. Its highly scalable products fully interoperate with and extend the life and utility of today's public network. Sonus embodies in its management and staff decades of experience in developing carrier-class voice, data and multimedia solutions for implementation in the world's largest networks. Sonus, founded in 1997, is headquartered in Westford, Massachusetts. Additional information on Sonus is available at http://www.sonusnet.com.

This release may contain projections or other forward-looking statements regarding future events or the future financial performance of Sonus 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 Sonus' Annual Report on Form 10-K, dated March 28, 2001, filed with the SEC, which identifies important risk factors that could cause actual results to differ from those contained in the forward-looking statements. These risk factors include, among others, the Company's ability to grow its customer base, dependence on new product offerings, market acceptance of its products, rapid technological and market change, integration risks relating to the acquisition of telecom technologies and manufacturing and sourcing risks.

GSX9000, PSX6000, SGX2000, Sonus Insight and Open Services Architecture are trademarks of Sonus Networks. INtelligentIP is a registered trademark of Sonus Networks. All other company and product names may be trademarks of the respective companies with which they are associated.