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Latest Partners Offer Array of Next-Generation Technologies and Products

WESTFORD, Mass., December 10, 2001 – Sonus Networks (Nasdaq: SONS), a leading provider of voice infrastructure solutions for the new public network, today announced that it has added six new members to the roster of telecommunications vendors participating in the company's Open Services Partner Alliance^SM (OSPA). 

By joining the OSPA, Appian Communications, Catena Networks, ipDialog, Nuance, snom technology and Virtual Access demonstrate their commitment to developing next-generation converged network solutions based on the Sonus platform. The partners entering the OSPA today continue to broaden the diversity of packet-based technologies and solutions offered within the program, and also expand the geographical scope of the partner alliance. 

"Partnerships are a key component of Sonus' mission to provide carriers with complete packet voice solutions that enhance their competitive advantage in the telecom marketplace," said Terri Griffin, vice president, marketing, Sonus Networks. "We look forward to working with each of these new partners to help our customers cost-effectively add value to their next-generation networks and provide exceptional end-user services."

Companies joining the Sonus OSPA today offer the following solutions:

• Appian Communications is enabling a new generation of carrier-class Ethernet services that bring Ethernet economics and packet service flexibility to today's widely deployed and highly reliable SONET/SDH networks. With Appian's Optical Services Activation Platform^(TM) (OSAP^(TM)) and AppianVista^(TM) Service and Element Management software, carriers can migrate to a new generation of high bandwidth packet services that combine the low cost and simplicity of Ethernet with the resilience, end-to-end manageability and global scale of today's installed SONET/SDH networks. (www.appiancom.com)  
• Catena Networks has developed groundbreaking broadband access products, which will enable the mass-market deployment of broadband DSL services and access network convergence. These products include the Catena CNX-5 Broadband DSL System and the Catena CN1000 Broadband Loop Carrier. (www.catena.com)  
• ipDialog offers a family of VoIPTone Ethernet phones for the enterprise, small office/home office and residential markets. The VoIPTone phones support SIP, H.323, Megaco/H.248 and MGCP standards and are readily customizable to meet the requirements of OEM or service-provider customers. (www.ipdialog.com)  
• Nuance delivers a range of speech recognition, voice authentication, text-to-speech and Voice Web software. Nuance's products, which include server software, application-enablers for target industries, and developer tools allow phone users and customers to interact with voice-driven telecommunications, enterprise and Internet systems. (www.nuance.com)  
• Snom technology provides VoIP phones based on open standards to transport voice over data networks. snom's VoIP phones set new standards regarding flexibility and interoperability, offering compatibility with VoIP gateways and gatekeepers based on industry standards, such as SIP and H.323/H.450, and providing an integrated HTTP browser to facilitate configuration and remote management. (www.snom.de)  
• Virtual Access develops service managed server, controller and gateway products for next-generation broadband networks. The company's LifelineIP^(TM) technology enables carriers to cost-effectively develop service-oriented IP networks offering high levels of availability, scalability and manageability. (www.virtualaccess.com) 

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 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, integration risks relative to its acquisition of telecom technologies, 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.