Sonus Delivers Critical Emergency Services For Consumer VoIP

Sonus Enables VoIP Service Providers to Comply with Recent FCC Ruling

CHELMSFORD, Mass., May 24, 2005 – Sonus Networks (Nasdaq: SONS), a leading supplier of service provider voice over IP (VoIP) infrastructure solutions, announced today that its industry-leading voice infrastructure solution enables VoIP service providers to offer critical emergency services to their customers. Recently, the Federal Communications Commission issued an important ruling requiring VoIP service providers to supply Enhanced 911 (E-911) emergency calling capabilities to their customers as a mandatory feature of the service. The Sonus platform facilitates the delivery of these critical services to consumers through seamless connectivity to the Public Switched Telephone Network (PSTN), and several Sonus customers, including Level 3 Communications, are already utilizing Sonus' platform to support delivery of E-911.

"As the adoption of VoIP services by consumers continues to grow, the imperative to deliver innovative telephony services that also provide traditional features, such as access to emergency services, has steadily increased," said Hassan Ahmed, chairman and CEO, Sonus Networks. "The recent decision by the Federal Communications Commission aligns with Sonus' long-standing commitment to deliver consumer VoIP services that offer the same levels of quality and reliability as their traditional telephony service. Sonus is proud that its solutions are being leveraged today to deliver fully-featured VoIP services to consumers."

To enable the delivery of E-911 services, Sonus' GSX9000TM Open Services Switch and the InsignusTM  Softswitch support the Centralized Automatic Message Accounting (CAMA) signaling standard, as well as ISDN and SS7. The support of this signaling standard allows service providers to interconnect with Public Safety Answering Points (PSAPs) around the country. The ability to reach these facilities in the event of an emergency is critical for dispatching emergency response services, or transferring or relaying 911 calls to other public safety agencies. Designed for 99.999% network availability, Sonus' platform delivers superior performance and reliability and enables the delivery of E-911 services today.

Level 3 Communications offers one of the most reliable and comprehensive E-911 services for voice over IP in the United States. The company has deployed Sonus' voice infrastructure solutions, including GSX9000TM Open Services Switch and the InsignusTM  Softswitch across its nationwide broadband fiber optic network. Level 3's E-911 feature allows ISPs, cable companies, local phone companies, long-distance providers and others to build E-911 functionality into VoIP services that these providers offer in areas encompassing more than 66 percent of households nationwide.

"Widespread adoption of VoIP as a primary service will occur only when consumers trust that it can replicate the emergency-calling capabilities of the public switched telephone network," said Jack Waters, Level 3 executive vice president and chief technology officer. "We're pleased to be working with Sonus to deliver what we believe is one of the industry's most comprehensive E-911 solutions for voice over IP, and to working with existing and prospective customers in the months ahead to enable them to comply with the FCC's E-911 directive."

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 Open Services Architecture^TM (OSA), Sonus delivers end-to-end solutions addressing a full range of carrier applications, including trunking and tandem switching, residential and business access, network border switching, and enhanced services. Sonus' voice infrastructure solutions, including media gateways, softswitches, and network management systems, are deployed in service provider networks worldwide. Founded in 1997, Sonus is headquartered in Chelmsford, Massachusetts of U.S. 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' Annual Report on Form 10-K dated March 15, 2005, and the "Cautionary Statements" section of Sonus' Quarterly Report on Form 10-Q, dated May 9, 2005, both filed with the SEC, which identify important risk factors that could cause actual results to differ from those contained in the forward-looking statements. In addition, 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. Open Services Architecture, GSX9000, Insignus and Sonus Insight are trademarks of Sonus Networks. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective owners.