Spanish Communications Provider Interdata Engineering Selects iBasis for Expansion of International Services

Global ISP and Satellite Communications Provider to Leverage The iBasis Network™ for International VoIP Services; Agreement Extends The iBasis Network to Spain

BARCELONA, Spain, September 25, 2000-iBasis, Inc., (Nasdaq: IBAS), the leader in advanced Internet-based communications, today announced that Interdata Engineering, a worldwide communications service provider with operations in Spain, will use The iBasis NetworkTM to expand its advanced voice communication services for global enterprises. The announcement was made at the Carriers World conference held in Barcelona, Spain. Interdata joins the more than 100 global service providers that have chosen iBasis for Internet Telephony.

Under the terms of the agreement, Interdata Engineering will be able to route international voice and fax traffic over the iBasis Network, the world's largest international Cisco Powered Network for Internet Telephony. In addition, the agreement with Interdata extends iBasis' global footprint to the major business centers of Spain.

Interdata Corporation is a global communications systems and services provider, supplying a wide range of value-added communications solutions, as well as networking, engineering and integration services, to businesses and service providers around the world. Interdata's clients include multinational telecommunications carriers, service providers and small and medium-sized enterprises. In Spain, Interdata's communications network covers the country's most important commercial centers, including Madrid and Barcelona, and the company is aggressively expanding its services to the country's other major metropolitan areas.

"In selecting a partner for IP-based communications, our choice was clear: iBasis, the provider of choice for 10 of the top 20 global carriers," said Alvaro Ramirez, President and Founder of Interdata Engineering. "Using the iBasis Network, we can efficiently extend our global footprint, while delivering a quality of service, backed by iBasis' unmatched IP and telecommunications expertise, that has become the industry's benchmark for carrier-class VoIP."

"Interdata has quickly established itself as an innovative provider of IP-based services to global enterprises," said Ofer Gneezy, president and CEO of iBasis, Inc. "Our interconnection to Interdata's rapidly growing network extends our ability to reach the most important commercial centers of Spain."

The iBasis Network and Carrier-Class VoIP 
The iBasis Network is the world's largest international Cisco Powered Network (CPN) for Internet telephony. Cisco Systems is the worldwide leader in networking for the Internet. The iBasis Network comprises large carrier-class switching facilities called Internet Central OfficesTM, strategically located in Amsterdam, Cambridge (Mass.), Frankfurt, Hong Kong, London, Los Angeles, New York and Vancouver, as well as numerous smaller points of presence called Internet Branch OfficesTM , which play an important role in both originating and terminating traffic. With this global infrastructure and through its telephony peering relationships with other communications providers, iBasis can terminate calls virtually anywhere in the world.

iBasis is the only provider that guarantees service quality by offering the industry's first Service Level Agreement (SLA) for VoIP (Voice-over-Internet-Protocol). The key to maintaining the high level of quality required by the world's largest carriers is the company's proven, proprietary Assured Quality RoutingÔ (AQRÔ) technology. At the company's 24 x 7 Network Operations Center (NOC), the nerve center of The iBasis Network, engineers continuously monitor the global circuit-switched (PSTN) and packet-switched (IP) networks to ensure the highest quality of service to customers worldwide.

About Interdata Engineering 
Interdata Engineering is a world-class communications systems provider and integrator, supplying value-added communications and multimedia network solutions to businesses and service providers around the world. The company provides a complete range of communications systems that incorporate all the networking, engineering, and integration services needed to help clients apply leading-edge technology more effectively in the global marketplace. For more than eighteen years, Interdata Corp. has provided communications and data services to global enterprise clients in the USA, Europe, Russia, the Caribbean, and Latin America.

About iBasis 
Founded in 1996, iBasis (Nasdaq: IBAS) is the leader in advanced Internet-based communications. iBasis has built the world's first global IP network that delivers toll quality voice and fax service and other advanced hosted communications solutions, including VoCoreSM Unified Communications, to global tier one carriers and other service providers. The iBasis Network is the world's largest international Cisco Powered Network for Internet Telephony and the first to receive the Unified Communications Cisco Powered Network (UC-CPN) designation. More than 100 international service providers are iBasis customers including 11 of the top 12 U.S. international carriers. iBasis is listed in both the Russell 2000® and Russell 3000® Indexes. The company can be reached at its worldwide headquarters in Burlington, Mass., USA at 781-505-7500 or on the Internet at www.ibasis.net .

Except for historical information, all of the expectations, projections and assumptions contained in the foregoing press release 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, the considerations described as "Risk Factors" in iBasis' prospectus dated March 9, 2000, and the company's other SEC filings.

Assured Quality Routing and AQR are registered trademarks, VoCore is a service mark and iBasis, The iBasis Network, Internet Central Office and Internet Branch Office are trademarks of iBasis, Inc. Cisco and Cisco Powered Network are registered trademarks of Cisco Systems, Inc.