Some have raised questions about how Microsoft would be able to make such a purchase without showing a demonstrable and immediate need for the addresses as required under ARIN policy.

Microsoft's vice president of global foundation services, Dayne Sampson, suggested the purchase was intended to support Microsoft strategy. "Microsoft continues to assess opportunities to acquire useful assets, whether they are from Nortel or other sources to support the tremendous growth of our online services, particularly cloud services," he said by email.

Curran today refused to discuss the specifics of Microsoft's planned purchase. But in general, any reallocation of IPv4 addresses between two parties needs to absolutely meet ARIN policy requirements, he said.

Under current policy, if a company is acquired by another, all of its IP addresses automatically transfer to the acquiring entity. ARIN policy also allows one party to return its IPv4 addresses to ARIN or to designate them to a third-party, Curran said.

Companies that are allocating their address to a third party can ask for compensation if they want to, he said. However, the acquiring party is required to show an immediate and appropriate need for the addresses, he said.