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AT&T-backed Joint Venture Will Start By Introducing Internet Call Diversion Solution; Sonus Equipment Will Enable Alestra to Roll Out Complement of Next-Generation Telephony Services

MEXICO, D.F. and WESTFORD, Mass., Nov. 12, 2001 – Alestra and Sonus Networks (Nasdaq: SONS) today announced that Alestra, a joint venture between AT&T (NYSE: T) and Mexican financial and industrial institutions Bancomer and ALFA, has chosen Sonus as one of its equipment suppliers in the development of Alestra's packet-based voice network. As part of a multi-million dollar project, Alestra will implement a full range of Sonus packet voice solutions to initially offload Internet traffic from their circuit switched network. The Sonus technology will be a key component of the "next-generation" infrastructure that is being deployed by Alestra to expand its data and voice services portfolios. 

"We need an infrastructure that will enable us to maintain the highest availability of our Internet dial up services in order to increase our network capacity over the next three years and roll out new services over time," said Ricardo Pineda, CTO, Alestra. "Sonus is the supplier that best met our requirements for scalability, performance, reliability and cost. Sonus has a proven track record, deploying next-generation solutions for many of the best-known U.S. and international carriers, and it has demonstrated a full commitment with the development of our network."

Alestra is deploying a full range of Sonus' award-winning voice infrastructure solutions, including the GSX9000 Open Services Switch, the PSX6000 SoftSwitch, the SGX2000 SS7 Signaling Gateway and the Sonus Insight Element Management System.

Alestra will initially leverage the Sonus-based network to augment its existing Class 5 circuit switches, offloading modem-generated Internet traffic from its voice network. In this application, Internet-bound calls destined for remote access servers are diverted away from circuit switches before they enter the voice infrastructure, thus freeing up expensive and limited circuit voice network resources. With the new packet-based voice infrastructure, Alestra is also looking beyond the initial Internet call diversion application to deliver voice and data services on the same platform. 

"We are extremely pleased to be selected as the vendor of choice for Alestra's packet-voice network," said Hassan Ahmed, president and CEO, Sonus Networks. "With the backing of AT&T, Alestra is well positioned to take advantage of a major opportunity to serve as a leader in Mexico's growing market for next-generation telecommunications services. We look forward to working together to help Alestra transform its network, to generate new revenues and deliver new, competitive services to its Mexican customers."

Alestra has begun deployment of the Sonus solution for Internet call diversion in major Mexican markets. The company plans to build out its infrastructure further over the next few years, and it expects to introduce voice services based on VoIP technology into the Mexican market shortly. 

About Alestra

Alestra provides an array of voice, data, IP, and broadband services to both residential and business customers in Mexico. The company was founded in 1996 to introduce AT&T world-class telecommunications services, including long-distance phone service, in Mexico. Alestra has installed over 5,000 kilometers of fiber optic networking throughout Mexico. This network is fully interconnected to the worldwide AT&T Intelligent Network, which transmits more than 250 million voice and data messages per day in more than 280 countries and territories. Alestra is 49 percent owned by AT&T. Other shareholders include BBVA-Bancomer, one of the most recognized financial institutions in Mexico, and ALFA, a leading industrial and commercial corporation in Mexico. Additional information on Alestra can be found at http://www.alestra.com.mx.

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 Sonus' Quarterly Report on Form 10-Q, dated August 13, 2001, 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 Company's ability to grow its customer base, dependence on new product offerings, market acceptance of its products, rapid technological and market change, integration risks relating to the acquisition of telecom technologies and manufacturing and sourcing risks.

GSX9000, PSX6000, SGX2000, Sonus Insight and Open Services Architecture are trademarks of Sonus Networks. All other company and product names may be trademarks of the respective companies with which they are associated.