Sonus Networks Participates at Inaugural IMS Forum “IMS Plugfest for Applications and Services”

CHELMSFORD, Mass., December 12, 2006 - Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider Voice over IP (VoIP) infrastructure solutions, announced today that in an effort to advance the adoption of IP Multimedia Subsystem (IMS)-based solutions and drive interoperability across the industry, the Company will participate in the first “IMS Plugfest for Applications and Services.” The IMS Plugfest is sponsored by the IMS Forum, of which Sonus Networks is a founding member and Sonus Networks Chief Marketing Officer, Steve Edwards, is a member of the Board of Directors. The event will be held January 15-19, 2007 at the University of New Hampshire's Interoperability Lab (IOL).

The IMS Plugfest, the first in a series of events designed to advance interoperability testing industry-wide, is a critical step in helping the IMS Forum develop an industry-recognized “stamp of approval” for IMS applications and services and help network operators capitalize on the promise of IP convergence. Sonus Networks will be participating at the event by testing several elements of its award-winning IMS-ready architecture, including:

• The Sonus Networks HSX™ Home Subscriber Server (HSS): the central database of subscriber information that includes subscriber profiles and their current status in the network
• The Sonus Networks SRX™ Serving Call Session Control Function (S-CSCF): a robust coordinating entity for all voice and multimedia sessions, ensuring that the right application servers are brought into the session flow and that calls are routed to the correct destination. Session control functionality exists today in Sonus' ASX product, and full IMS S-CSCF functionality will be available in a separate product (the Sonus SRX Server) for IMS deployment
• The Sonus Networks PSX™ Breakout Gateway Control Function (BGCF): the industry's most comprehensive routing server for determining the best route for sessions between an IMS network to other networks (e.g., VoIP and TDM networks)

"Since day one, Sonus has been at the forefront of promoting interoperability throughout the IP-based voice communications market, advocating for standards-based, distributed architectures built on the foundation of principles expressed in the IMS architecture,” said Steve Edwards, chief marketing officer. “We're committed to leveraging our leadership role in this exciting industry to further promote the adoption and acceptance of IMS standards."

"Sonus has played an important role in the development of the world's largest IP-based voice networks, and we're excited to leverage the Company's rich experience and field-tested knowledge to help develop practical, robust guidelines that promote the expeditious rollout of IMS applications and services," said Michael Khalilian, IMS Forum President & Chairman and Pervasip Corp. CTO.

"With their Open Services Partner Alliance, Sonus has been one of the industry's strongest advocates for the importance of interoperability,” said Lincoln Lavoie, senior engineer, UNH IOL. “The overall objective of the IMS Plugfest is well served by the participation of companies like Sonus Networks that are committed to building networks that incorporate solutions from a variety of vendors."

Additional details about the IMS Plugfest can be found on the IMS Forum website at www.imsforum.org, or by contacting IMS Forum Program manager, Debbie Hetland, at dhetland@imsforum.org or via phone at 510-608-5907."

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 Chelmsford, Massachusetts. Additional information on Sonus is available at http://www.sonusnet.com.

This release may contain forward-looking statements regarding future events 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 Item 1A “Risk Factors” of Sonus' Quarterly Report on Form 10-Q dated May 8, 2006, filed with the SEC, which identifies important risk factors that could cause actual results to differ from those contained in the forward-looking statements. Risk factors include among others: the impact of material weaknesses in our disclosure controls and procedures and our internal control over financial reporting on our ability to report our financial results timely and accurately; the unpredictability of our quarterly financial results; risks and uncertainties associated with the Company's announced review of its historical stock option grants and accounting, including any potential impact on the Company's financial statements or results, any tax liabilities or penalties, the Company's inability to timely report with the Securities and Exchange Commission, the Company's potential inability to meet NASDAQ requirements for continued listing, potential investigations, regulatory actions or litigation arising out of the review or any restatement; risks associated with our international expansion and growth; consolidation in the telecommunications industry; and potential costs resulting from pending securities litigation against the company. Any forward-looking statements represent Sonus' views only as of today and should not be relied upon as representing Sonus' views as of any subsequent date. While Sonus may elect to update forward-looking statements at some point, Sonus specifically disclaims any obligation to do so.

The product information in this press release is for informational purposes only and is subject to change at Sonus' sole discretion without notice. Sonus has no obligation or commitment to develop or deliver any future release, upgrade, feature, enhancement or function described in this release. The information is provided “AS IS,” with all faults, and without any warranties whatsoever, express or implied, including, but not limited to, warranties of merchantability, performance, or fitness for a particular purpose.

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