CableLabs Selects Sonus to Participate in Demonstration; Sonus' Insignus Softswitch Represents Core of Company's Cable Solution

WESTFORD, Mass., February 4, 2002 – Sonus Networks (Nasdaq: SONS), a leading provider of voice infrastructure solutions for the new public network, today announced that it has been chosen by Cable Television Laboratories, Inc. (CableLabs ) for participation in the cable consortium's exclusive Winter Conference 2002, which is being held February 10-12, 2002, at the Westin Hotel in Westminster, Colorado. The main focus of the conference demonstrations is to showcase the content and services that cable customers will see in the next 12 to 18 months.

The Sonus Networks exhibit features an end-to-end packet cable telephony solution. At the heart of the live network demonstration is Sonus' carrier-grade softswitch platform, the Insignus Softswitch, which includes the PacketCable Call Management Server (CMS) function, as well as the Media Gateway Controller (MGC) and the SS7 Signaling Gateway functions. In the demonstration, the Insignus Softswitch controls cable Multimedia Terminal Adapters (MTAs) via the PacketCable Network Call Signaling (NCS) protocol, and Sonus' GSX9000 Open Services Switch, providing connectivity to the PSTN, transports voice traffic from the packet-based cable network in Sonus' booth to the circuit switched voice network.

"This demonstration illustrates that PacketCable voice is a reality today, and offers cable operators the ability to boost their competitive positions and build new revenue streams," said Terri Griffin, vice president, marketing, Sonus Networks. "We are excited to have the opportunity to take an active role in CableLabs' technology demonstrations, and look forward to working with the consortium to drive cable telephony into the mainstream."

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 November 14, 2001, 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.

Insignus, GSX9000 and Open Services Architecture are trademarks of Sonus Networks. Open Services Partner Alliance is a service mark of Sonus Networks. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective owners.