Acme Packet Demonstrates Interoperability with Sonus Networks' Packet Voice Infrastructure Solutions

Net-Net Session Director Passes Stringent Interoperability Tests; Acme Packet Reaches "Powered" Status in Sonus' Open Services Partner Alliance

WESTFORD, Mass., August 20, 2002 - Sonus Networks (Nasdaq: SONS), a leading provider of voice infrastructure solutions for the new public network, today announced that Acme Packet has achieved "Powered" partner status in the Sonus Open Services Partner Alliance (OSPA). Acme Packet's Net-Net Session Director (SD) successfully completed interoperability testing with Sonus' Insignus Softswitch and GSX9000 Open Services Switch at the Sonus OSPA Interoperability Lab. Acme Packet's solutions address issues faced by service providers exchanging VoIP (voice over IP) traffic with other service providers as well as with enterprise networks.

"Sonus is pleased to have proven interoperability with the Acme Packet Net-Net SD product," said Michael O'Hara, vice president, marketing, Sonus Networks. "The enhanced security and SLA assurance capabilities delivered by the Net-Net SD complement Sonus' packet voice infrastructure products, allowing carriers to extend their network reach and protect revenue streams."

The Acme Packet Net-Net SD is a high performance, high capacity session border controller that delivers premium interactive communications across wireline, wireless and cable IP network borders. The Net-Net SD performs critical control functions at IP-IP network borders between service providers and subscribers, or between two service providers. These control functions satisfy critical security, service assurance and law enforcement requirements.

The OSPA's mission is to help empower standards-based interoperability between applications, third-party vendors and Sonus products. Sonus' OSPA Interoperability Lab is uniquely positioned to test packet voice solutions through the use of state-of-the-art testing equipment within environmentally controlled facilities. Once an OSPA member demonstrates interoperability with a Sonus product, the partner becomes "Powered." Sonus and its "Powered" partners collaborate to deliver end-to-end packet-based network solutions using best-of-breed technologies and applications.

"The Acme Packet Net-Net session border controllers, in combination with Sonus' industry-leading voice infrastructure solutions, enable service providers to generate new revenue by connecting VoIP trunking networks to one another to deliver new IP services like presence-based instant calling/instant videoconferencing," said Andy Ory, president and CEO, Acme Packet. "Achieving "Powered" partner status in Sonus' OSPA is a critical step forward in our companies' missions of delivering end-to-end converged network solutions to our service provider customers."

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^TM (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 Insignus, GSX9000 and Open Services Architecture are trademarks of Sonus Networks. All other company and product names may be trademarks of the respective companies with which they are associated.