CHELMSFORD, Mass., May 9, 2005 – Sonus Networks, Inc. (Nasdaq: SONS), a leading supplier of service provider voice over IP (VoIP) infrastructure solutions, today reported its financial results for the first quarter ended March 31, 2005.

Revenues for the first quarter of fiscal 2005 were $33.6 million compared with $45.1 million in the fourth quarter of fiscal 2004. Net loss for the first quarter of fiscal 2005 was $3.7 million or a loss of $0.01 per share compared with net income for the fourth quarter of fiscal 2004 of $6.3 million or $0.02 per diluted share. Revenues for the first quarter of fiscal 2004 were $36.5 million, and net income was $3.0 million or $0.01 per diluted share.

"We achieved a number of key objectives in the quarter, including strong order activity, the expansion of our customer base, establishment of new global partnerships and the introduction of new software for the ISP market. We are, of course, disappointed that our progress is not reflected in our revenue result this quarter," said Hassan Ahmed, chairman and CEO, Sonus Networks. "Looking ahead, the world's service providers will continue their migrations to VoIP, and we are pleased that Sonus has a leading position in this important market."

During the first quarter, Sonus announced four new customer deployments in North America and in Europe. In the U.S., America Online is deploying Sonus' technology to deliver its new Internet Phone Service, which is changing the very nature of voice service, making it a pathway not just for conversations, but also for a wide range of next-generation interactive applications. Also in the U.S., WebEx Communications is augmenting its WebEx MediaTone Network with a VoIP solution from Sonus to deliver new IP-based conferencing services to its customers. In Mexico, Marcatel is building out a VoIP network with Sonus to provide access services to businesses and cable operators. In Europe, Slovak Telecom has implemented a Sonus-based network to support the delivery of prepaid and postpaid calling services.

Demonstrating the scalability and reliability of the Sonus solution, three existing customers extended their Sonus-based networks during the first quarter. XO Communications announced their new business service, XOptions® Flex, which is the first in a series of the carrier's new enhanced services delivered over the XO national IP network and Sonus technology. Leveraging the Sonus Open Services Architecture^TM (OSA), XO Communications will deliver a broad range of IP telephony applications and features to businesses throughout the United States. South Carolina-based NuVox also announced that it is introducing a new business VoIP service that will be delivered over its Sonus-based network. Further, Global Crossing, one of the first providers to decommission a legacy switch in the core of its network and replace it with a VoIP switch, announced that it is continuing to decommission legacy switches in four additional cities. This project is expected to create increased network efficiencies and enhance the seamless delivery of converged IP services.

Underscoring Sonus' success with both existing and new customers, the company was again ranked the number one provider of carrier-class packet voice equipment for the fourth quarter of 2004. Industry research firms reported that Sonus increased its market share in several segments of the carrier packet voice market, growing faster than the market and the competition in 2004. In-Stat/MDR and Synergy Research Group named Sonus the market share leader, recognizing Sonus as the top equipment vendor in several major service provider packet telephony market segments. Additionally, Sonus estimated that at the end of Q1, service providers globally were carrying an estimated 12 billion minutes per month of customer traffic on their Sonus-based networks.

In January 2005, Sonus entered into a global reseller agreement with Samsung Electronics Company. Under the terms of this non-exclusive agreement, Samsung is able to sell and support Sonus VoIP solutions to mobile operators around the world.

Continuing the expansion of its worldwide presence, Sonus announced the opening of a software development and regional support center in Bangalore, India. Sonus Networks India Pvt. Ltd. will concentrate on the development of VoIP applications, software design and quality assurance services in support of Sonus' product portfolio. The establishment of Sonus' center in India represents another phase in the company's commitment to providing VoIP applications and services to customers around the globe.

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, filed with the SEC, 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 associated with our international expansion and growth; consolidation in the telecommunications industry; risks associated with the investigation of the company by the SEC; 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. Open Services Architecture is a trademark of Sonus Networks. All other company and product names may be trademarks of the respective companies with which they are associated.