Newest Members Bring Broadband Infrastructure and Messaging Offerings to OSPA

WESTFORD, Mass., September 12, 2002 - Sonus Networks (Nasdaq: SONS), a leading provider of voice infrastructure solutions for the new public network, today announced that Terayon Communication Systems, Inc. (Nasdaq: TERN) and Unisys Corporation (NYSE: UIS) have joined Sonus' Open Services Partner AllianceSM (OSPA).

"By joining the OSPA, Terayon and Unisys underscore their commitment to establishing standards-based interoperability between next-generation communications products to deliver complete carrier-class voice, data and multimedia solutions," said Michael O'Hara, vice president, marketing, Sonus Networks. "We welcome both companies into the Alliance, and we look forward to working together to facilitate the deployment of packet voice with telecommunications providers worldwide."

The OSPA brings together leading telecom hardware and software vendors providing a range of products such as enhanced services, network infrastructure and operations support systems (OSS). The companies entering the program today expand the solutions options available to carriers, providing enhanced services such as messaging as well as infrastructure solutions such as cable access devices.

Partners joining the OSPA today deliver solutions including:

• Terayon provides a range of broadband systems for cable operators, including DOCSISTM (Data Over Cable Service Interface Specification) and PacketCable based cable modem termination systems (CMTSs) and embedded multimedia terminal adapters (eMTAs). Terayon is the first company to offer such products based on the DOCSIS 2.0 specification, which helps enable superior performance and scalability for cable-based VoIP systems.
• Unisys, a worldwide information technology company, combines systems integration and consulting expertise with multimedia messaging and enterprise mobilization solutions to help communication clients achieve a competitive advantage. Unisys brings to the OSPA a diverse set of communications solutions including voice/fax messaging, universal messaging and multimedia messaging services, which can be customized to address service providers' specific requirements.

About Sonus' OSPA

Sonus Networks' Open Services Partner Alliance program provides a framework that offers service providers end-to-end packet-based network solutions using best-of-breed technologies and applications. The goal of the OSPA is to empower standards-based interoperability between applications, hardware vendors, and the Sonus product family. An integral part of the Sonus OSPA, the OSPA Interoperability Laboratory is the first in the industry where product interoperability is verified, trial testing is performed and complete solutions are ultimately produced. To find additional information on the OSPA, including a list of all OSPA partners, log on to http://ospa.sonusnet.com.

About Sonus Networks

Sonus Networks, Inc., is a leading provider of packet voice infrastructure products for the new public network. With its Open Services Architecture (OSA), Sonus delivers end-to-end solutions addressing a full range of carrier applications, including trunking, residential access and Centrex, tandem switching, and IP voice termination, as well as enhanced services. Sonus' award-winning voice infrastructure solutions, including media gateways, softswitches and network management systems, are deployed in service provider networks worldwide. 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' Quarterly Report on Form 10-Q, dated August 14, 2002 and 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 adverse effect of recent developments in the telecommunications industry, the weakened financial position of many emerging service providers, Sonus' ability to grow its customer base, dependence on new product offerings, market acceptance of its products, rapid technological and market change and manufacturing and sourcing risks.

Open Services Partner Alliance is a service mark of Sonus Networks and Open Services Architecture is a trademark of Sonus Networks. All other company and product names may be trademarks of the respective companies with which they are associated.