Founder of Bay Networks, Other Leading Network Communications Companies, Accepts Advisory Role with Leading Voice-Over-Packet Carrier Switch Start-Up.

WESTFORD, Mass., April 8, 1999 - Sonus Networks, an emerging leader in carrier-class Voice-Over-Packet solutions that fully integrate with the existing public voice network, today announced the appointment of Paul J. Severino to its Board of Directors. As Founder and Chairman of Bay Networks, and Founder and Chief Executive Officer of Wellfleet Communications and Interlan, Severino brings to Sonus Networks a rich experience in guiding communications companies from start-up to industry leadership. He assumes his advisory role as the company prepares for its forthcoming introduction of the industry's first carrier-class VoIP switch, providing an open architecture for the rapid creation and deployment of enhanced voice and voice/data services. He also currently serves as Chairman of NetCentric, the leading supplier of IP fax services for carrier customers and Internet Service Providers.

"The competitive dynamics of the telecom market are rapidly shifting; toll minutes are becoming commoditized and carriers are increasingly forced to compete through the delivery of innovative, customer-specific new service products," Severino noted. "With winners and losers in this market soon to be determined based on their time-to-market for higher-margin services, Sonus' Open Services ArchitectureTM and award-winning products uniquely position it to seize this singular opportunity. I look forward to actively working with the experienced management team at Sonus Networks."

"As the driving force behind several of the most successful companies in our industry, Paul's insight will help to guide Sonus in establishing market leadership. His market-proven vision will help us to give our carrier customers and our growing global network of development and channel partners a distinct advantage in leveraging the true potential of the new public network that Sonus is helping to build," said Hassan Ahmed, Sonus President and CEO.

Under Severino's leadership, Wellfleet Communications was named by Fortune Magazine as "America's Fastest Growing Company" in both 1992 and 1993. Wellfleet merged with SynOptics Communications to become Bay Networks; Severino served as Bay's chairman until 1997. Bay Networks was acquired by Nortel Networks in June 1998 for $9 billion.

Severino is currently chairman of NetCentric Corp., which designs, sells, and supports systems that provide Internet fax service, and is chairman of the Massachusetts Technology Development Corporation (MTDC). He is a past chairman of the Massachusetts Telecommunications Council, and is a member of the Massachusetts Governor's Council for Economic Growth. His numerous recognitions include: Inc. Magazine's Entrepreneur of the Year, New England Region, the William F. Glaser '53 Rensselaer Entrepreneur of the Year, and being named to the Massachusetts Telecommunications Council Hall of Fame. He serves as a trustee of Rensselaer Polytechnic Institute and as chair of the advisory board of the Lally School of Management and Technology at RPI.

Severino will play a strategic advisory role in the introduction and market acceptance of the Sonus Gateway Switch 9000 (GSX 9000), the industry's first open platform for rapid creation and delivery of new service products. The unprecedented capacity, sophistication and absolute reliability of the GSX 9000 enable it to support tens-to-hundreds of thousands of simultaneous calls, enabling carriers to save millions of dollars in annual network operations costs. It provides an evolutionary migration path from today's PSTN to the new public converged network that supports both voice and data, while preserving legacy infrastructure investments.

About Sonus Networks

Sonus Networks, Inc. is developing and marketing the next generation of carrier-grade IP telephony for the public voice network. Its equipment facilitates the movement of telephony from traditional circuit networks to packet networks, enabling a host of new carrier and end user services. The Sonus management and engineering teams have proven success records, having led organizations such as Ascend Communications, recently acquired by Lucent Technologies (NASDAQ: LU); Bay Networks, recently acquired by Northern Telecom (NT); and Summa Four, recently acquired by Cisco (NASDAQ: CSCO), where they directed the development and delivery of carrier-class equipment to support data, voice and multimedia information. Sonus Networks was recently awarded the prestigious Hot Startup of the Year Award by Data Communications Magazine, which also awarded the Sonus GSX 9000 the Hot Product of the Year Award. Sonus also received the 1999 Investor's Choice Award at Technologic Partners' Network Outlook Conference. Additional information is available at www.sonusnet.com.