Sonus Networks IMS-Ready Solution Enables Advanced VoIP Network to Deliver New Services

CHELMSFORD and BOSTON, Mass., September 20, 2005 - Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider voice over IP (VoIP) infrastructure solutions, announced today at the Fall Voice on the Net (VON) 2005 Conference and Expo, that EarthLink (Nasdaq: ELNK), the nation's next generation Internet Service Provider, has selected Sonus Networks as the framework for its complete suite of consumer voice services, which includes the ASX™ Access Server, PSX™ Call Routing Server, and the Sonus Insight™ Management System. Over the next three months, EarthLink will launch increasingly feature-rich products and services using the Sonus platform.

“We believe there are tremendous opportunities to build and deliver innovative voice communications products and services, and technology shouldn't be a hurdle to future growth,” said Steve Howe, vice president of voice services at EarthLink. “Partnering with companies like Sonus will help us expand our service offerings and differentiate us from our competitors.”

The Sonus Networks IP Multimedia Subsystems (IMS) ready VoBB solution is one of the industry's most scalable, reliable and proven architectures available for ISPs today. With the Sonus ISP solution, which was introduced in March 2005, service providers like EarthLink are able simultaneously to deliver high quality telephony service and enriched communication applications. The Sonus VoBB solution also allows service providers to seamlessly and cost effectively comply with developing IMS standards, maximizing their network investment. The Sonus VoBB solution features comprehensive support for Session Initiation Protocol (SIP) that enables the rapid integration of multiple services allowing EarthLink to develop and deliver premium services in the future, such as its Line Powered Voice service, which the company announced earlier this year.

“ISPs like EarthLink that have a strong customer base and have demonstrated a keen understanding for how users communicate have the opportunity to be a disruptive force in the telecommunications industry,” said Hassan Ahmed, chairman and CEO of Sonus Networks. “Consumer confidence that a service will be simple yet powerful is critical to propelling VoBB solutions even further into the mainstream. EarthLink, which has a distinguished history of providing user-friendly communication services, is in a position to capitalize on consumers' enthusiasm for competitive new voice offerings.”

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 of U.S. Additional information on Sonus is available at http://www.sonusnet.com.