Slovak Telecom Relies On Sonus Networks and Pactolus Communications Software to Bring VoIP Services to the Bratislava Summit

Slovak Telecom, Sonus Networks and Pactolus Communications Software Deliver Calling Card Services at Bush-Putin Slovakia 2005 Summit

BRATISLAVA, SLOVAKIA, SWINDON, UK & WESTBOROUGH, MASS, March 10, 2005 - Sonus Networks (Nasdaq: SONS), a leading supplier of service provider Voice over IP (VoIP) infrastructure solutions, and Pactolus Communications Software, a leading supplier of carrier-class, enhanced voice applications for next-generation networks, today announced that Slovak Telecom extended its next-generation network using Sonus Networks and Pactolus solutions to support the summit of the United States and Russian presidents, George Bush and Vladimir Putin, recently held in Bratislava, Slovakia on February 24, 2005. Slovak Telecom, a leading telecommunications company in Slovakia, was selected to provide the communications and technology infrastructure during the summit. Additionally, Slovak Telecom provided prepaid/postpaid calling cards, supported by the Sonus-based network, to all journalists attending the event.

As part of an ongoing relationship with Slovak Telecom, Sonus Networks has deployed an integrated next-generation VoIP solution that includes calling card services based on Pactolus' application. Supported by the Sonus' Open Services ArchitectureTM (OSA), Slovak Telecom is delivering multiple IP-based voice services, including Global Card and Directory enquiry and operator-assisted services. Slovak Telecom first deployed Sonus' GSX9000TM Open Services Switch, InsignusÔ Softswitch and Sonus InsightTM Management System as the foundation for their VoIP network and has since expanded its next-generation network to include the Pactolus SIPware Calling Card and Operator Services. The combined Sonus / Pactolus solution provides a broad range of SIP-based calling services throughout Slovak Telecom's network, enabling feature flexibility delivered through a cost-effective IP-environment.

"A robust communications infrastructure was essential for government leaders and other attendees during that summit," said Herbert Mueller, COO, Slovak Telecom. "We required trusted partners that could deliver a cost-effective platform that was scalable, reliable and deployment-ready. The solutions from Sonus Networks and Pactolus have been deployed in large-scale networks around the world and enabled us to seamlessly support the increased demand for the duration of the summit."

"Pactolus responded very quickly to this important event and doubled Slovak Telecom's calling card services capacity in a matter of hours." said Gordon Arthur, VP Business Development, Pactolus Communications Software Corporation. "In conjunction with Sonus Networks media gateways, the entire solution continued to meet the scalability and reliability requirements expected during the peak call loads of the summit."

"As the world's telecommunications networks evolve to a packet-based infrastructure, carriers such as Slovak Telecom are finding new ways to leverage the flexibility next-generation networks can provide,” said Steve Edwards, chief marketing officer, Sonus Networks. "Integrating prepaid/postpaid applications on a Sonus packet-based architecture has allowed Slovak Telecom to rapidly scale their network to meet the expected increased demand. We are very pleased to be working with Slovak Telecom to deliver enhanced voice services to the summit, and look forward to continuing to work with them to further expand their service offerings."

About Slovak Telecom

Slovak Telecom is a leader in the area of telecommunications services in the Slovak Republic. The company provides national and international telephone services, offers a wide portfolio of data services, arranges for the distribution and transmission of radio and television signals, and offers a wide range of value-added services. The shareholders of Slovak Telecomare Deutsche Telekom AG (51 percent), Ministry of Transport, Posts and Telecommunications of the Slovak Republic (34 percent), and the National Property Fund of the Slovak Republic (15 percent). Slovak Telecom is the exclusive owner of EuroTel Bratislava, a.s., a provider of mobile communications services and operator of data networks. For more information visit the company website www.telecom.sk.

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. Sonus, founded in 1997, is headquartered in Chelmsford, Massachusetts. 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/A dated July 28, 2004 and filed with the SEC, and the "Cautionary Statements" section of Sonus' Quarterly Report on Form 10-Q, dated November 9, 2004 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. 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 and Insignus are trademarks of Sonus Networks. All other trademarks, service marks, registered trademarks, or registered service marks are the property of their respective owners.

About Pactolus Communication Software

Pactolus Communications Software Corporation is the leading provider of SIP-based voice services for today's networks with over 1 billion minutes of monthly network capacity installed worldwide in carrier networks. The company is the first to bring sophisticated, third-party call control capabilities to SIP-based networks. Pactolus offers the industry's broadest suite of commercially proven, turnkey IP voice services that can be customized for deployment in any SIP-enabled carrier network called SIPwareTM Services. These services include primary line broadband telephony (VoIP), audio conferencing, voice messaging, prepaid and post paid calling card, and SCE-built applications, built upon the RapidFLEXTM Application Server. Pactolus is a venture funded, privately held company headquartered in Westborough, Massachusetts.

Media Relations Sonus EMEA:
Tom Cheesewright
+44 (0) 1628 628080
tomc@noiseworks.com

Investor Relations:
Jocelyn Philbrook
+1 978-614-8579
jphilbrook@sonusnet.com

Media Relations Pactolus:
Ken Osowski
+1 781-929-6061
kosowski@pactolus.com

Media Relations Slovak Telecom:
Radoslav Bielka
+421 2 588 10 420
radoslav.bielka@st.sk