Sonus Networks to Participate in IMS Forum's Plugfest IV

Forum to Focus on Triple Play, OSS/BSS and Billing Applications

WESTFORD, Mass., February 5, 2008 – Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider Voice over IP (VoIP) infrastructure solutions, announced today that the Company is continuing its efforts in driving the adoption of applications and services in an IP Multimedia Subsystem (IMS) environment through its participation in the IMS Forum's "IMS Plugfest™ IV", an industry-wide forum designed to foster the interoperability of IMS applications and services for wireless, wireline and cable broadband networks. The IMS Plugfest is sponsored by the IMS Forum (www.imsforum.org), of which Sonus Networks is a founding member. The next event will be held February 25-29, 2008 at the University of New Hampshire InterOp Lab (IOL).

IMS Forum Plugfest IV will focus on IMS Triple Play, Operational Support systems (OSS), Business Support Systems (BSS), and Billing Applications. Forum members have the opportunity to test the interoperability of IMS applications and operational systems over a unified IMS network. Sonus will participate at the event testing several elements of its award-winning IMS-ready architecture. This year at Plugfest IV, Sonus is broadening its 2.0 SIP Core offering to include its Subscriber Location Function (SLF). Additionally, Sonus will have an expanded applications portfolio presence to include new multi-media applications featuring voice and video on its industry leading IMX 2.0 Multimedia Applications Platform.

"Sonus has been involved with the IMS Forum's Plugfest since its inauguration. The IMS Forum's Plugfest has grown immensely since it started last year and is certain to continue gaining participants and momentum," said Vikram Saksena, chief technology officer, Sonus Networks. "At Plugfest IV, we're focusing on the interoperability of IMS with business operations and support systems. By emphasizing these functions we hope to help our customers more effectively and efficiently navigate the path to IMS."

"Sonus has performed exceptionally well in past Plugfest tests. At Plugfest III, Sonus completed a battery of tests with a focus on IMS-powered applications and security solutions," said Michael Khalilian, IMS Forum Chairman & President. "We look forward to another successful event, and to providing an environment where industry pioneers can come together to advance interoperability of IMS solutions."

Results of IMS Plugfest IV will be announced at the Spring VON.X show, March 17 to 20, 2008, in San Jose. Spring VON.X is one of the most respected IP communications events in the industry. Pulvermedia, host of Spring VON.X, is also an IMS forum Plugfest IV event media sponsor.

About the IMS Forum^®

The IMS Forum is a global, non-profit industry association devoted to interoperable IP Multimedia Subsystem services delivery architecture and solutions. IMS Forum's mission is to accelerate the interoperability of IMS revenue-generating services and enabling enterprise and residential consumers to fully benefit from the delivery of multimedia mobile and fixed services over broadband cable, wireless, wireline and fiber networks. The IMS Forum is the creator and organizer of the IMS Plugfest™, the industry's only event focused on IMS service interoperability verification and certification through the IMS Certified™ program.

Through its organized Plugfests, working group interactions and other activities, forum members are able to develop cost-effective technical frameworks for converged IP services over wireline, cable, 3G, WiFi and WiMAX networks. Plugfest IV will be held February 25-29, 2008 at the UNH InterOp Lab in New Hampshire. Results of Plugfest IV will be revealed on March 18 at Spring VON.X 2008 in San Jose, CA. For additional information or to join the IMS Forum and the IMS Plugfests, please visit www.IMSForum.org.

About Sonus Networks

Sonus Networks, Inc. is a leading provider of voice over IP (VoIP) infrastructure solutions for wireline and wireless service providers. With its comprehensive IP Multimedia Subsystem (IMS) solution, Sonus addresses the full range of carrier applications, including residential and business voice services, wireless voice and multimedia, trunking and tandem switching, carrier interconnection and enhanced services. Sonus' voice infrastructure solutions are deployed in service provider networks worldwide. Founded in 1997, Sonus is headquartered in Westford, Massachusetts. Additional information on Sonus is available at http://www.sonusnet.com.

Sonus is a registered trademark of Sonus Networks, Inc. All other company and product names may be trademarks of the respective companies with which they are associated.