COLT Telecom Connected to iBasis
for Global VoIP Services

Interconnection Enables Pan-European
Carrier COLT To Expand International
Services As iBasis European Revenues
Nearly Quadruple Over Past Year

BURLINGTON, MA-November 8, 2001-iBasis, Inc., (Nasdaq: IBAS), the leader in Internet-based voice communications, today announced that COLT Telecom Group plc (Nasdaq: COLT) has interconnected its pan-European network with The iBasis NetworkTM. The agreement between the two companies has enabled COLT to route its international voice and fax traffic over The iBasis Network, the global VoIP infrastructure for the world's largest carriers. In addition, iBasis has been able to leverage COLT's extensive pan-European network to deliver its international traffic into the major business centers of Europe.

COLT operates an integrated, IP-based, pan-European network linking the financial and business centers of Europe, providing a full range of telecommunications services to corporate and carrier customers. COLT currently operates in 29 European cities in twelve countries, and plans to be providing services in 32 cities by the end of 2001. In addition COLT provides Internet connectivity, Internet hosting and enables application services in 11 European countries.

"Our strong relationship with COLT, a major European carrier, has played an important role in enabling iBasis to nearly quadruple its European business over the past year," said Ofer Gneezy, president and CEO of iBasis. "Through our interconnections in London, Frankfurt, and the US we have carried large volumes of global voice traffic for COLT, while our access to their high quality voice infrastructure has helped strengthen our footprint across Europe. With Tier 1 carriers continuing to seek outsourced international service, Europe is an important region for iBasis, representing approximately 36% of our total revenues."

"Our decision to interconnect with iBasis was based on their proven ability to provide global voice services the quality of which is comparable with that of our own state-of-the-art network," Said Ian Hinchliffe, Commercial Director for COLT Telecommunications. "By leveraging iBasis' global reach and carrier-class VoIP infrastructure, we are adding a new dimension to our service capability and are able to deliver high quality, high value service to our customers across Europe."

iBasis in Europe
Today's announcement caps a year of impressive growth for iBasis in Europe. With more than 14 major European carrier customers, iBasis revenues from European voice traffic nearly quadrupled from Q3 2000 to Q3 2001. According to industry analyst publication TeleGeography 2002, Europe has experienced the strongest international traffic growth of any region outside North America, and represented about 43% of all international traffic in 2000, (the latest year for which statistics are available.)

Much of the growing demand for iBasis international VoIP services in Europe, as in other regions, has come from Tier 1 carriers, the world's largest and most demanding service providers. More than 50% of all voice traffic carried by The iBasis Network is generated by Tier 1 carriers.

iBasis and the Move to VoIP
While the international voice services market is expected to be worth more than $70 billion, for most large carriers, international service is not core, and generally represents about 5% of revenues. At the same time, the cost of maintaining global service operations is disproportionately high. Outsourcing international traffic to iBasis offers service providers a powerful competitive advantage by lowering the cost of transport and reducing overall global infrastructure and service support requirements.

According to industry analyst firm TeleGeography, VoIP transport is expected to account for approximately 6% of all international voice traffic in 2001, double the approximately 3% it comprised in 2000. As international voice traffic continues to grow, decreasing sales of traditional circuit-switching equipment and a predicted tripling of VoIP gateway equipment sales¹ over the next five years offers further evidence that the fundamental shift to VoIP is well underway.

About COLT
COLT Telecom Group plc is a leading provider of high bandwidth data, voice and advanced telecommunication services to business and governmental customers in Europe. It currently has operations in 29 European cities in twelve countries, and plans to be providing services in 32 cities by the end of 2001. It currently has a long-distance network of 10,735km. When completed in mid 2002 it will consist of 15,500km. In addition COLT provides Internet connectivity, Internet hosting and enables application services in 11 European countries, with a backbone reaching into the US and more than 450 peering agreements. COLT Internet Solution Centres (ISCs) have been built in 16 cities totalling more than 880,000 square feet (81,000 square metres) of hosting space.

During the year ended December 2000 turnover was £640.8 million and it carried 15.8 billion switched minutes of traffic. During the quarter ended September 2001 turnover rose 39% to 231,4 million.

COLT Telecom Group plc is listed on the London Stock Exchange (CTM.L) and Nasdaq (COLT). Information about COLT and its products can be found on the World Wide Web at www.colt.net .

About iBasis
Founded in 1996, iBasis (Nasdaq: IBAS) is the leader in advanced Internet-based voice communications. iBasis delivers toll quality international voice services and provides the infrastructure for hosted communications solutions, including messaging and speech-enabled content, e-commerce and customer service applications. The company's customers include many of the largest enterprises and carriers in the world, including AT&T, Cable & Wireless, China Mobile, China Unicom, Concert, ExxonMobil, Gannett, H&R Block, Home Shopping Network, Morgan Stanley, NTT, Telefonica, Telstra, Sabre Group, Sprint, Western Union, WorldCom, and Verizon. iBasis' hosted, enhanced service solutions include SpeechPortTM, a scalable, customizable ASP environment for speech-enabled business solutions, VoCore^SM messaging and the IP CallCardTM pre- and post-paid calling card platform. The iBasis Network is the world's largest international Cisco Powered Network for Internet Telephony. iBasis is listed in both the Russell 2000® and Russell 3000® Indexes. The company can be reached at its worldwide headquarters in Burlington, Massachusetts, USA at 781-505-7500 or on the Internet at http://www.ibasis.net .

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Assured Quality Routing and iBasis are registered marks, VoCore is a service mark, The iBasis Network, Internet Central Office, Internet Branch Office, IP CallCard, SpeechPort, IPort, and PriceInteractive are trademarks of iBasis, Inc. or its subsidiaries. Cisco and Cisco Powered Network are registered trademarks of Cisco Systems, Inc. All other trademarks are the property of their respective owners.

Except for historical information, all of the expectations, projections and assumptions contained in the foregoing press release, including those relating to the company's current expectations regarding revenue growth, sources of revenue, margin improvement and future capital expenditures constitute forward-looking statements under the Private Securities Litigation Reform Act of 1995 and involve risks and uncertainties. Important factors that could cause actual results to differ materially from such forward-looking statements include, but are not limited to, (i) the extent of adoption of the company's voice-based Internet services and the timing and amount of revenue generated by these services; (ii) fluctuations in the market for and pricing of VoIP services; and (iii) the other considerations described as "Risk Factors" in iBasis' Annual Report on Form 10-K for its fiscal year ended December 31, 2000, and the company's other SEC filings.