iBasis Completes Transaction with Danish Carrier TDC, Acquires Wholesale Business and Five-year Outsourcing Deal

BURLINGTON, Massachusetts and COPENHAGEN, Denmark – 04/01/2008 – iBasis (NASDAQ: IBAS), a KPN affiliate, and TDC, the leading telecommunications company in Denmark, today announced the completion of their transaction, which results in iBasis acquiring TDC’s non-Nordic international wholesale voice business. iBasis also has become the exclusive provider of international voice services for TDC in a five-year strategic outsourcing arrangement. The agreement was originally announced on January 14, 2008.

In completing the transaction, iBasis has acquired TDC’s wholesale voice business for approximately $10 million. iBasis expects to generate approximately $80 million in new annual revenue from the exchange of approximately two billion minutes of international traffic resulting from the transaction. TDC has become a preferred partner for terminating iBasis traffic into the Nordic region. Other financial details of the agreement are undisclosed.

Approximately 130 non-Nordic international wholesale voice customers, as well as all of TDC’s interconnection and bilateral agreements for inbound and outbound international phone calls have been transferred to iBasis. TDC will maintain its Nordic customer base and its pan-Nordic reach, and will benefit from becoming iBasis’ preferred partner for termination of international traffic throughout the Nordic region. iBasis also acquired the voice-related assets, contracts, office rental and employees of TDC subsidiary TDC Carrier Services U.S., which will be fully integrated into iBasis.

The outsourcing arrangement closely follows iBasis’ transaction with Royal KPN, N.V. in October 2007, which resulted in the acquisition of KPN Global Carrier Services by iBasis, effectively outsourcing KPN’s international voice business to iBasis. Combining KPN Global Carrier Services with iBasis has enabled iBasis to become a leading platform for international voice outsourcing by giving the company far greater scale, advanced features for mobile traffic, and a more complete premium quality product portfolio.

Intense competition in telecommunications is driving carriers worldwide to focus their resources on the implementation of innovative technologies and the development of compelling services that are highly valued by their consumer customers. TDC continues to invest massively in IT and fixed and mobile network technologies to deliver the highest quality TV, telephony, and broadband services in Denmark and through its subsidiaries in other Nordic countries. The convergence of network technologies and services provides TDC exciting market opportunities and requires increased focused on the development of consumer and business services.

“Unlike most wholesale providers, international voice is our core business,” said Ofer Gneezy, president and CEO of iBasis. “Because of the efficiencies of scale we’re able to leverage, iBasis is uniquely positioned to be the outsource solution for incumbent carriers like TDC, who want to focus more effectively on their core retail businesses.”

About TDC

With nearly eight million customers, TDC is the leading provider of communications solutions in Denmark and a strong player in the Nordic business market. The company has evolved from a traditional provider of landline and mobile services into a dynamic provider of modern communications solutions. In all key markets in Denmark, TDC will continue to be the clear front-runner, and it is TDC’s goal to be the most efficient telecom operator in the Nordic region, providing the best coherent services on all terminals and networks, anytime, anywhere. The company’s shares are traded on the Copenhagen Stock Exchange.

About iBasis

Founded in 1996, iBasis (NASDAQ: IBAS) is a leading wholesale carrier of international long distance telephone calls and a provider of retail prepaid calling services and enhanced services for mobile operators. iBasis customers include KPN, KPN Mobile, E-Plus, BASE, and many other large telecommunications carriers such as AT&T, Verizon, Vodafone, China Mobile, China Unicom, IDT, Qwest, Skype, Telecom Italia, Telefonica, and Yahoo. In October 2007, iBasis acquired KPN Global Carrier Services to create one of the three largest carriers of international voice traffic in the world 1, and KPN became a majority stockholder of iBasis. On a pro forma basis, the combined company carried approximately 24 billion minutes of international voice traffic in 2007. The Company can be reached at its worldwide headquarters in Burlington, Mass., USA at +1 781-505-7500 or on the Internet atwww.ibasis.com.