Microsoft Reaches Agreement in Bid To Buy Nortel's IPv4 Addresses

Microsoft has entered a legacy agreement with the American Registry for Internet Numbers (ARIN) over its purchase of Nortel's IPv4 numbers, possibly heading off controversy over the issue of who controls IPv4 numbers.

Microsoft in March paid $7.5 million for a block of nearly 7 million slightly used IPv4 addresses from Nortel, which is in U.S. Bankruptcy Court in Delaware. The deal, which marked the first large-scale transfer of legacy addresses since IPv4 addresses started to dry up, was authorized last Monday.

The purchase touched off a possible confrontation over who controls addresses issued before the current Regional Internet Registry for North America was created. Questions immediately arose regarding whether the IPv4 addresses would -- or could -- be transferred outside the ARIN framework, or whether the Nortel numbers would be placed under a registration services agreement for legacy numbers.

ARIN said the addresses are not privately owned assets and should be transferred under its policies, which it says reflect the consensus of the Internet community. Although it has no contractual agreement with the holders of these legacy addresses, ARIN has assumed the responsibility for managing the addresses.

With the specter of IPv4 address depletion now becoming a reality, there is a growing concern of a developing unregulated black market for remaining unused addresses that have been allocated. The concern is especially high for addresses allocated by organizations such as InterNIC (the Internet Network Information Center) before December 1997, when ARIN was created.

About the Author

William Jackson is the senior writer for Government Computer News (


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