Onvoy Voice Services Taps Sonus Networks for Expansion Initiative

Strategic Deployment Supports Introduction of Services into New Markets

WESTFORD, Mass., April 26, 2011 – Sonus Networks, Inc. (Nasdaq: SONS), a market leader in next-generation IP-based network solutions , today announced that Onvoy Voice Services, a provider of wholesale telecom services to wireline and wireless telecom companies, has teamed with Sonus to support Onvoy's expansion initiatives. The Onvoy deployment includes Sonus's GSX9000 media gateway , PSX centralized route server , SGX signaling gateway and Element Management System installed in facilities in Minneapolis, Denver and New York.

Throughout the evaluation process, Onvoy cited Sonus' reputation for quality and highly scalable, distributed architecture as key factors shaping the decision to deploy.

Onvoy provides its customers with a full range of voice services including Tandem, Transit and Long Distance that deliver high-quality, low-cost connectivity solutions. Following an extensive evaluation process, which included lab testing of several solutions, Onvoy determined that Sonus could best provide the scalability and reliability required to support the company's plans.

"To provide our growing customer base with the flexibility needed to adapt to the changing inter-carrier market, Onvoy needed to deploy an architecture that allowed for market expansion and at the same time undertake a sensible migration and consolidation path for existing legacy equipment," said Gary Kosin, Director of Engineering for Onvoy Voice Services. "With our decision to deploy Sonus equipment, we are well positioned to offer new and exciting services today and scale reliably to meet future demand."

"Competition in the service provider market is as strong as ever and leading organizations such as Onvoy Voice Services are consistently developing new products and services to keep ahead," said David Tipping, vice president of marketing and product management, Sonus Networks . "Having the right network infrastructure in place to support strategic growth now and in the future is critical to ongoing success and is exactly what Sonus provides."

About Sonus Networks

Sonus Networks, Inc. is a leader in IP networking with proven expertise in delivering secure, reliable and scalable next-generation infrastructure and subscriber solutions. With customers in over 50 countries across the globe and over a decade of experience in transforming networks to IP, Sonus has enabled service providers and enterprises to capture and retain users and generate significant ROI. Sonus products include media and signaling gateways, policy/routing servers, session border controllers and subscriber feature servers. Sonus products are supported by a global services team with experience in design, deployment and maintenance of some of the world's largest and most complex IP networks. For more information, visit .

About Onvoy

Onvoy Voice Services, a subsidiary of Zayo Group Holdings, Inc., has been offering a full suite of wholesale services to wireless, wireline, cable and broadband companies since 1991. Onvoy provides tandem and transit, wholesale CLEC, long distance, SS7/database services, and call management solutions such as directory assistance and operator services. Onvoy Voice Services is headquartered in Minnesota and continues to expand nationally. For more information, visit Onvoy at www.onvoy.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 Item 1A "Risk Factors" of Sonus' Annual Report on Form 10-K for the year ended December 31, 2010 and all subsequent Quarterly Reports on Form 10-Q, which identify important risk factors that could cause actual results to differ from those contained in the forward-looking statements. 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, except as required by law.

Sonus is a registered trademark of Sonus Networks, Inc. All other company and product names may be trademarks of the respective companies with which they are associated.

For more information, please contact:

Sonus Networks:
Aline Kaplan
alkaplan@sonusnet.com
+1 978-614-8167

Paul Roberts
sonus@daviesmurphy.com
+1 781-418-2418