Latest Award Follows Sonus' Recent Receipt of the Prestigious Hot Startup Award.

WESTFORD, Mass., January 18, 1999 – Sonus Networks, innovators in carrier-class IP telephony products and services, today announced that the Sonus Gateway Switch (GSW) – the first IP telephony switch with the capacity, sophistication and absolute reliability to support tens of thousands of simultaneous calls – has been named as one of the year's Hottest Products by Data Communications Magazine. The GSW Switch features the Sonus Open Services Architecture^(TM), the only open platform for IP telephony innovation that lets carriers and independent developers quickly create and deliver competitive new services.

Sonus President and CEO Hassan Ahmed noted: "The GSW is perfectly poised to leverage escalating world-wide demand for carrier-class central office IP telephony equipment that enables the rapid creation and delivery of competitive new services, and delivers the scalability, absolute reliability and sophistication to substantially evolve the intelligence, economics and market dynamics of the telephony industry."

Probe Research Executive Vice President Hilary Mine said: "At last we are seeing truly carrier-class equipment that cost-effectively integrates voice and data over IP networks while offering meaningful integration with the existing public switched network."

The GSW has been built with substantial input from many of the new converged-network carriers and leading incumbent carriers. Its ability to support the rapid introduction of competitive new services, add massive incremental call capacity, and ensure full interoperability with and graceful migration from existing circuit networks enables these carriers to fuel and quickly expand major new revenue streams.

Leading carriers also anticipate achieving substantial operational savings by employing the Sonus GWS as part of a converged IP network for voice, fax, data, video, and other applications.

"Sonus is emerging as a leader in an important new era of the telecommunications industry," said Robert Rich, Vice President of Telecomm Research at the Yankee Group. "They're giving both new IP and incumbent carriers a new dimension on which to compete, one with outstanding profit potential: the immediate development and delivery of innovative services. Undoubtedly, this will significantly evolve the market."

Chris Rothlis, Vice President of New Product Development at IXC, commented: "The ability to innovate and immediately deliver new products and services will be a key differentiator for new and incumbent carriers. Sonus is positioned to deliver a true carrier-class IP telephony platform."

The Experience to Open a New Market:

The Sonus team is distinctly successful in the delivery of carrier grade solutions. Their combined experience in telecommunications, multimedia and data communications has fostered the creation and delivery of a new class of solutions with the capacity, scalability, service support and absolute reliability to support the public network. Sonus Chairman and co-founder Rubin Gruber previously founded VideoServer (Nasdaq - VSVR), Davox (Nasdaq - DAVX), and Cambridge Telecommunications, acquired by GTE (NYSE - GTE); Sonus President Hassan Ahmed, Ph.D., was Executive Vice President and General Manager of Ascend Communications' (Nasdaq - ASND) Core Systems Division, and previously, Cascade Communications' Chief Technology Officer; and Dr. Michael Hluchyj, Vice President, founder and CTO, was previously VP and CTO at Summa Four, recently acquired by Cisco (Nasdaq - CSCO), was also Director of Networking Research at Motorola Codex (NYSE - MOT), and was a leading member of the Technical Staff at AT&T Bell Laboratories (NYSE - LU).

The editors of Data Communications scoured the industry for the best and brightest products and services networking technology. After months of rigorous research, the editors selected 50 winners which boast a key technology differentiator that sets them apart from the competition. Winners were selected in the following categories: IP Tools, Internetworking, WAN Services, Networks Software, WAN Gear, Security, Network Management/Analysis, LAN Gear and Carrier-Class Equipment.

"The HOT PRODUCTS" award is a significant endorsement of a new product or service's 'promise' in terms of the technological advancement or enhancements it intends to provide to networking professionals," according to Data Communications editor in chief, Lee Keough. "Data Communications readers, who design, build and manage the world's largest networks, recognize and respect the HOT PRODUCTS logo and use its distinction to help them make critical purchase decisions."

About Sonus Networks

Sonus Networks, Inc. is developing and marketing the next generation of carrier-grade IP Telephony. Its equipment facilitates the movement of telephony from traditional circuit networks to packet networks, enabling a host of new carrier and end user services. Sonus is funded by some of the telecommunications industry's most well-respected venture capital firms, including: Bedrock, Charles River Ventures, Matrix Partners, North Bridge Venture Partners, and Bessemer Venture Partners. The Sonus management and engineering teams have proven success records in the development and delivery of carrier-class equipment to support data, voice and multimedia information.