Market Research Firm Reports Sonus-based Networks Extends Lead with Most IP-Based Voice Traffic

CHELMSFORD, Mass., September 28, 2006 – Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider Voice over IP (VoIP) infrastructure solutions, announced today that according to a report entitled, “VoIP Minutes and Subscribers: 2Q06 Update," issued by iLocus, 37% of all long distance IP-based voice traffic is carried over Sonus Networks' IP Multimedia Subsystem (IMS)-ready networks. In August 2006, Sonus carried approximately 25 billion minutes of IP voice traffic, representing an approximately 75% increase compared to August 2005.

“The voice market is entering an aggressive phase of migration to IP-based technologies, as evidenced by the tremendous growth in minutes that Sonus-based networks support," said Jahangir Raina, Director, iLocus. “The rate of acceleration is a testament to the fundamental strength of Sonus' IMS-ready technology, their ability to support large-scale migrations seamlessly, and the Company's continued success adding tier 1 carriers to their growing customer base."

Sonus' award winning IMS-ready architecture is relied upon by network operators globally, and today, Sonus solutions form the foundation of some of the largest and most sophisticated IP-based voice networks in the world. Recent announcements have included the addition of CarPhone Warehouse's Opal Telecom and Cable and Wireless International to Sonus' global customer base. These large-scale deployments by leading communications providers demonstrate the strength of Sonus' solutions for both core and local voice networks, and underscore the maturity of the IP-voice market and the beginning of a new phase in the industry's migration to all-IP networks.

Sonus' distributed architecture enables carriers to scale their infrastructure, penetrate new markets and expand their revenue opportunity by supporting the introduction of innovative new applications and services. The iLocus report recognized that Sonus leads both the national and international long distance market with 39% and 25% of voice traffic respectively. With more than a third of all IP-based voice traffic running on Sonus-based networks, Sonus carries approximately three times traffic more than any other vendor.

"Sonus is continuing to experience strong demand for its award-winning products and solutions," said Hassan Ahmed, chairman and CEO, Sonus Networks. “Our technologies have been proven in the some of the world's most demanding voice networks. As the network operators globally move to IP-voice, Sonus is proud to be the partner of choice for these operators. Our commitment to customer success and innovation is unprecedented, and we are continuing to develop technologies that will further our customers' success."

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.