Malaysia's First Internet Service Chooses iBasis As Exclusive Provider of Global VoIP Services

Interconnection Agreement with MIMOS Strengthens iBasis Footprint in Asia

Enables Leading Regional ISP to Expand Global Voice Services

BURLINGTON, MA - JUNE 20, 2001 - iBasis, Inc., (Nasdaq: IBAS), the leader in advanced Internet-based voice communications, today announced that Malaysia's first Internet Service Provider (ISP), MIMOS Internet Services - a subsidiary of MIMOS Berhad - has chosen iBasis as its exclusive provider of global VoIP services. The partnership enables MIMOS to efficiently expand its international reach by routing its customers' voice traffic over The iBasis Network^TM, the global Voice-over-Internet-Protocol infrastructure for the world's largest carriers. In addition, the interconnection with MIMOS enables iBasis to extend its already extensive Asian footprint to the important global markets of Malaysia. MIMOS' interconnection agreement also enables MIMOS to offer its customers international calling cards using the iBasis IP CallCardTM pre- and post-paid calling card solution.

MIMOS was established by the Malaysian government in 1985 as the Malaysian Institute of Microelectronic Systems (MIMOS), and has since become a department within Malaysia's Ministry of Science, Technology and the Environment. MIMOS owns and manages JARING, the country's first Internet Service Provider. In 1999, MIMOS launched SuperJARING, increasing network speeds to 2.5 Gbps of capacity to provide one of the fastest nationwide data networks in the world. JARING's services include dial-up and dedicated link access, value-added services, such as international voice, web hosting and global roaming.

"iBasis is known as the VoIP quality leader and the international provider of choice for many of the world's largest carriers. iBasis, whose broad Asian market experience and presence complements our own, was our first choice for global VoIP services," said Syed Md Najib Syed Md Noors, managing director, MIMOS Internet Services. "Connecting to The iBasis Network not only allows us to cost effectively expand our reach across the world, but also enables us to explore offering new enhanced communications services such as iBasis' hosted messaging and speech-enabled business services."

"MIMOS is a vital part of Malaysian telecommunications. We are pleased to have the opportunity to serve as MIMOS' global VoIP provider and extend our services to this important Asian commercial hub," said Ofer Gneezy, president and CEO of iBasis. "Moving forward, we plan to work closely with MIMOS as they explore using their advanced, high-speed IP network to provide their customers with access to our other enhanced communications services."

iBasis in Asia
iBasis has seen remarkable growth in the region with Q1 2001 revenues from its Asian business increasing by 196% or nearly three-fold over Q1 2000. One factor driving this strong regional revenue growth is the 274% increase in iBasis traffic origination from Asia during that same period. Approximately 38% of iBasis revenues in Q1 2001 came from its Asian business. International Data Corporation predicts that the worldwide market for VoIP services will grow from under US $2 billion in 2000 to more than $17 billion in 2004. In the Asian-Pacific region alone, IDC expects revenues to reach US $6.2 billion in 2006, up from approximately $7 million in 2000.

More than 110 service providers worldwide are iBasis' customers. In Asia alone, iBasis customers include four of the five largest carriers in China, including China Unicom, China Mobile, Jitong Communications, and China Netcom (CNC). Other regional customers include NTT, the Japanese carrier, Australia's Telstra, Hutchison Corporate Access, and The Communications Authority of Thailand.

In March of this year, iBasis officially opened a second Network Operations Center (NOC) on its global network in Hong Kong. The company's new Hong Kong facility provides additional global network and traffic management capabilities to support the company's rapidly growing global business. A mirror site of the first iBasis NOC, located at iBasis' US headquarters near Boston, Massachusetts, the Hong Kong NOC helps the company further scale its services and increase utilization on The iBasis Network.

The Hong Kong NOC enables iBasis to more efficiently manage its global network operations and reduce its network engineering and staffing costs by transferring more of its traffic management and monitoring tasks to less costly daylight hour shifts. This increased operational efficiency enables iBasis to deliver faster, more effective support services to its customers, without regard to time zone, culture or language. The iBasis Hong Kong facility is professionally staffed 24X7 and features state-of-the-art network monitoring and management capabilities, including the company's proprietary Assured Quality Routing^TM (AQR^TM) technology which helps ensure that iBasis' Internet-based voice service is indistinguishable from that of traditional phone networks.

The iBasis Network: A Carrier-Class Global Infrastructure For Enhanced Services
The iBasis Network^TM is a robust, global platform for the delivery of IP-based communications services, including wholesale, phone-to-phone VoIP and enhanced services, such as messaging and speech-enabled business solutions. With a carrier-class infrastructure in 65 countries and through its relationships with other communications providers, iBasis can provide voice services virtually anywhere in the world.

About MIMOS Berhad
MIMOS Berhad is a mission-oriented Research and Development (R&D) government corporation that plays a pivotal role in developing communications capabilities for the country of Malaysia.

MIMOS was established by the Malaysian government in 1985 as the Malaysian Institute of Microelectronic Systems (MIMOS). In 1990 the organization became a department within Malaysia's Ministry of Science, Technology and the Environment, and in 1995 MIMOS was appointed the Secretariat to the National IT Council. Further growth enabled the corporatization of MIMOS Berhad in November 1996, providing the organization with greater versatility in creating value-added innovations for the industry, society and nation. MIMOS can be found on the Internet at www.mimos.net.my .

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, 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 and the first to receive the Unified Communications-Cisco Powered Network (UC-CPN) designation. 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 http://www.ibasis.net .