[[As of 2005|As of December 2005]], IPv6 accounts for a tiny percentage of the live addresses in the publicly-accessible Internet, which is still dominated by IPv4. The adoption of IPv6 has been slowed by the introduction of [[classless inter-___domain routing]] (CIDR) and [[network address translation]] (NAT), each of which has partially alleviated the impact of [[address space]] exhaustion. Estimates as to when the pool of available IPv4 addresses will be exhausted vary — in 2003, Paul Wilson (director of [[APNIC]]) stated that, based on then-current rates of deployment, the available space would last until 2023,<ref>[http://news.zdnet.com/2100-1009_22-1020653.html Exec: No shortage of Net addresses] By John Lui, CNETAsia </ref>. December 21, 2004 [[Nortel]] becomebecame the first networking company to complete the University of New Hampshire IPv6 phase II testing. In September 2005 a report by [[Cisco Systems]] reported that the pool of available addresses would be exhausted in as little as 4–5 years.<ref>[http://www.cisco.com/web/about/ac123/ac147/archived_issues/ipj_8-3/ipv4.html A Pragmatic Report on IPv4 Address Space Consumption] by Tony Hain, Cisco Systems</ref> [[As of November 2006]], a regularly updated report projected that the [[Internet Assigned Numbers Authority|IANA]] pool of unallocated addresses would be exhausted in May 2011, with the various [[Regional Internet Registry|Regional Internet Registries]] using up their allocations from IANA in August 2012.<ref>[http://www.potaroo.net/tools/ipv4/ IPv4 Address Report]</ref> This report also argues that, if assigned but unused addresses were reclaimed and used to meet continuing demand, allocation of IPv4 addresses could continue until 2024. The [[Federal government of the United States|U.S. Government]] has specified that the network backbones of all federal agencies must deploy IPv6 by [[2008]].<ref>[http://www.gcn.com/print/25_16/41051-1.html CIO council adds to IPv6 transition primer]</ref> But there are two specific challenges to this requirement. 1) There is no special federal funding available for IPv6 transitions. Thus agencies are expected to make the migration via their ongoing equipment purchases and network updates. Most agencies now have their transition plan in place, but surveys have noted that many are lagging when it comes to making that transition a reality. <ref>[http://www.govitwiki.com/wiki/IPv6_for_Gov#Current_Situation IPv6 for government - Current Situation]</ref>. 2) Agency IT budgets are tight at the moment, especially since the current 2007 IT Budget has been stalled, thanks to the Continuing Resolution.
Meanwhile [[Peoples Republic of China|China]] is planning to get a head start implementing IPv6 with their [[5 year plan]] for the [[China Next Generation Internet]].
