Synergy Research Group Reports Sonus Leads Several Categories of IP-Based Voice Market in Key Geographies

CHELMSFORD, Mass., September 14, 2006 – Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider Voice over IP (VoIP) infrastructure solutions, announced today that Synergy Research Group, a leading independent industry analysis firm, has named Sonus Networks the market share leader in key categories of the IP-based voice industry in both the United States and Japan in their recent reports entitled, “Q2 2006 Service Provider VoIP United States Market Shares" and “Q2 2006 Service Provider VoIP Japan Market Shares."

In the United States, Sonus maintained its number one market share position in the high density gateway market with 44.7%. Sonus' high density media gateway, the GSX9000™, is one of the key components in Sonus' industry leading IP Multimedia Subsystem (IMS)-ready architecture, and is deployed in some of the United States' largest wireless and wireline networks.

"Sonus is present in both Tier 1 incumbent and emerging networks throughout the United States. As these operators continue to rely on Sonus to grow and support their networks, Sonus' position as a market leader is continually reaffirmed," said Jeremy Duke, president and CEO, Synergy Research Group. “In Q2, Sonus not only maintained its number one position, but also outpaced the overall growth in the market."

Sonus also maintained its leadership in Japan. Over the first half of 2006, Sonus has been the dominant market share leader, with approximately 80% of the high density gateway market and 63% of total media gateway market. Sonus has announced deployments with several of Japan's largest service providers including KDDI, NTT Communications, SOFTBANK BB, Fusion Communications, Jupiter Telecommunications (J:COM), , and WILLCOM, Inc.

“Japan is a very exciting market for us to be in, as Japanese network operators are among those that are farthest along in their migration to all-IP networks," said Hassan Ahmed, chairman and CEO, Sonus Networks. “Both the United States and Japanese markets are proof-positive that IP-voice is a mature technology and Sonus Networks has the right solutions, service and support to help operators be successful."

For a copy of the Synergy Research Group Report, entitled “2Q06 Service Provider Worldwide VoIP Market Share Report," please contact Heather M. Wilson, Synergy Research Group, Inc., hwilson@srgresearch.com.

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 the “Risk Factors" section of Sonus' Quarterly Report on Form 10-Q, dated May 8, 2006, filed with the Securities and Exchange Commission, 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 of the Company's financial statements or results, 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 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.

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