The American Registry for Internet Numbers (ARIN) has warned members of the impending exhaustion of IPv4 addresses and advised them to begin planning for IPv6 adoption if they have not done so already.

"One of the most important steps is to make your organization’s publicly accessible resources (e.g. external web servers and e-mail servers) available via IPv6 as soon as possible. This will maintain your Internet connectivity during this transition," said John Curran, Chairman of ARIN's board of trustees, in his letter to members.

At the current rate of consumption, ARIN estimates that IPv4 will be depleted by 2011. You can read Mr. Curran's letter in full here.