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Unefon to Implement Packet Voice Network to Deliver Access Services; Plans to Offer Traditional Long Distance Voice and Enhanced Voice Services

WESTFORD, Mass., April 14, 2003 – Unefon and Sonus Networks (Nasdaq: SONS) today announced that Unefon has chosen Sonus Networks to deploy a next-generation packet voice network that will support access services, long distance voice and enhanced services. Unefon will implement Sonus' Open Services ArchitectureTM (OSA) and voice infrastructure solutions, including the GSX9000TM Open Services Switch, the InsignusTM Softswitch and the Sonus InsightTM Management System.

"Through the Sonus-based infrastructure we're announcing today, Unefon will deploy a network to service enterprise and residential customers who will be able to take advantage of the improved economics offered by voice over IP," said Juan Carlos Olvera, Unefon's director of Fixed Telecommunication Products. "More importantly, this new packet voice network will allow us to deliver an array of traditional voice services, as well as enhanced converged voice and data applications, thus being able to satisfy all of our customers' needs at very competitive prices."

Initially, Unefon will deliver access services to enterprise customers via PBX (Private Branch Exchange) connectivity. In this application, Unefon will provide connectivity for business customers' existing PBXs to the packet voice network by directly linking them to Sonus' GSX9000 Open Services Switch. By connecting PBXs to the packet voice infrastructure, Unefon can offer enterprise users a variety of standard local services that they have enjoyed with circuit-based solutions, including emergency services, direct dialing, call transfer, call privacy, call screening and more.

In subsequent deployment phases, Unefon plans to leverage the Sonus-based network to deliver long distance services through its existing transmission infrastructure. Additionally, with the Sonus infrastructure, Unefon can also provide a range of SIP (Session Initiation Protocol) enhanced services, such as call center, conferencing, prepaid calling and others.

"We are extremely pleased that Unefon has selected Sonus as its partner in deploying a next-generation packet voice architecture," said Hassan Ahmed, president and CEO, Sonus Networks. "The development of this network will enable Unefon to extend its presence in the fixed telephony market, where they can offer a complete package of voice services, from access services to long distance to enhanced services."

Unefon plans to initially deploy the Sonus solution in Mexico City. Based on the successful implementation in this city, Unefon will deploy Sonus' packet voice infrastructure solutions in other markets where it currently provides service. 

About Unefon

Unefon, S.A. de C.V. (BMV: UNEFON) is a Mexican telephony company whose main business is to provide mobile services to the mass market. Recently, taking advantage of its existing infrastructure it has started to provide fixed telecommunication services which includes telephony, Internet access and long distance.

About Sonus Networks

Sonus Networks, Inc., is a leading provider of packet voice infrastructure products for the new public network.  With its Open Services Architecture (OSA), Sonus delivers end-to-end solutions addressing a full range of carrier applications, including trunking, residential access and Centrex, tandem switching, and IP voice termination, as well as enhanced services. Sonus' award-winning voice infrastructure solutions, including media gateways, softswitches and network management systems, are deployed in service provider networks worldwide. Sonus, founded in 1997, is headquartered in Westford, Massachusetts.  Additional information on Sonus is available at http://www.sonusnet.com.

This release may contain projections or other forward-looking statements regarding future events or the future financial performance of Sonus 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 19, 2003 and filed with the SEC, which identifies important risk factors that could cause actual results to differ from those contained in the forward-looking statements. These risk factors include, among others, the adverse effect of recent developments in the telecommunications industry, the weakened financial position of many service providers, Sonus' ability to grow its customer base, dependence on new product offerings, market acceptance of its products, rapid technological and market change and manufacturing and sourcing risks. 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.