Industry leader links with major integrator to provide local sales, service and support

SWINDON, UK, April 27, 2005 – Sonus Networks (Nasdaq: SONS), a leading supplier of service provider voice over IP (VoIP) infrastructure solutions, today announced that it has entered into a Co-operative Marketing and Teaming Agreement with NK Networks & Services , an independent IT-network and telecommunications systems integrator, targeting the German, Austrian and Swiss telecommunications markets.

This partnership forms part of Sonus' strategy of expansion into the Central and Eastern European market and builds on the extension of its local presence in this region. The agreement will allow Sonus to leverage the strong market presence NK Networks & Services has in Germany, Austria & Switzerland as a systems integrator for complex voice and data projects. Initially the two companies are co-hosting a series of roadshows, executive roundtables and NK Carrier Days where they will outline next generation solutions for ISP's and mobile carriers.

"NK Networks & Services is renowned for its intelligent network design, robust implementations and high quality customer service," commented Joop van Aard, Vice President, Sales - Europe, Middle East and Africa, Sonus Networks. "This agreement enables us to offer service providers in Germany, Austria and Switzerland a simple route to deploying next generation networks."

"Sonus' industry-leading Open Services Architecture adds a vital element to our carrier systems portfolio," added Michael Horn, managing director of NK Networks & Services. "Working with Sonus, we can now offer service providers in our target markets everything they need to rapidly deploy next generation services and applications that reduce costs and generate new revenue.

About NK Networks & Services

NK Networks & Services focuses on designing, delivering and maintaining next-generation networking technology that helps customers extend and maintain their competitive momentum. With its excellent team of technical experts and consultants, NK Networks & Services established itself as the leading systems integration and service partner for large enterprises and service providers in the Central European Region.

With its HQ in Cologne and offices in Berlin, Dortmund, Frankfurt, Hamburg, Hannover, Munich, Nuremberg and Stuttgart, NK Networks & Services employs 140 people and a German-wide service network. Since 1985, NK Networks & Services has been implementing local as well as wide area networks and largely influenced the evolution of modern data communications. Among others, freenet, EWE Tel, QSC, Tiscali, Munich and Frankfurt airports and the German parliament are clients as well as companies across a wide range of industries including banks, insurance companies, utility companies, city carriers, transportation companies, the public sector and universities. For more information: http://www.nknetworks.com..

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 ArchitectureTM (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 and filed with the SEC, 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.

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.