CosmoCom's IP-based Call Center Demonstrates Interoperability with Sonus Networks' Voice Infrastructure Solutions

CosmoCom Achieves 'Powered' Status In Sonus' Open Services Partner Alliance; Provides Carriers Comprehensive IP-based Call Center Capabilities

WESTFORD, Mass., April 1, 2002 – Sonus Networks (Nasdaq: SONS) today announced that CosmoCom has successfully completed interoperability testing between its call center application and Sonus' industry-leading voice infrastructure solutions. As a 'Powered' partner in Sonus' Open Services Partner AllianceSM (OSPA), CosmoCom has demonstrated that its CosmoCall Universe^TM software effectively interworks with Sonus products to provide carriers a proven, network-based call center solution.

"Working together with CosmoCom, we are able to offer service providers the necessary solutions to build a rich set of IP-based call center offerings which enable organizations to increase revenues, improve customer satisfaction and promote customer loyalty," said Terri Griffin, vice president of marketing, Sonus Networks. "We are very pleased that CosmoCom has taken the next step in the OSPA."

CosmoCom is building the next generation of call center technology designed to power universal access call center platforms. The company's CosmoCall Universe product enables service providers to host and manage both computer-based and telephone-based callers in a single integrated environment without circuit switching. The Network-Based ACD (Automatic Call Distributor) offering supports multichannel customer interactions via telephone and internet, live and message-based in one high capacity, high availability, multi-tenant platform. CosmoCom's Next Generation Intelligent Network (NGIN) offering provides a rich set of pre-routing features enabling the service provider to statically or dynamically load-balance calls among the different locations of their multi-site call center customers.

The OSPA mission is to empower standards-based interoperability between applications, third-party vendors and Sonus products. Sonus is uniquely positioned to test packet voice solutions through the use of state-of-the-art equipment within its OSPA Interoperability Lab. Once an OSPA member completes interoperability testing with a Sonus product, the partner becomes 'Powered.' Sonus and its 'Powered' partners can offer service providers end-to-end packet-based network solutions using best-of breed technologies and applications.

"We are gratified to have reached 'Powered' status in Sonus' industry-leading OSPA program," said Steve Kowarsky, executive vice president, CosmoCom. "Working with Sonus' technology, we can offer carriers an integrated network capable of carrying both voice and data traffic, and which allows them to deliver a range of innovative, new services to organizations looking to enhance their call centers."

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' Annual Report on Form 10-K, dated March 28, 2002, 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 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.