EarthLink Selects Sonus Networks for New Consumer VoIP Network; Sonus Networks IMS-Ready Solution Enables Advanced VoIP Network to Deliver New Services

Business Wire, Sept 20, 2005

CHELMSFORD & BOSTON, Mass. -- 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(TM) Access Server, PSX(TM) Call Routing Server, and the Sonus Insight(TM) 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.

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 August 8, 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. 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 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 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.