It is often said that the number of TCP-IP addresses available on the Internet is running low but this time there are specific dates for when the addresses are predicted to run out. The Internet Assigned Numbers Authority predicts they will run out on April 17, 2010 while the Regional Internet Registries is predicting a December 2, 2010 doom day. The American Registry for Internet Numbers, the organization responsible for giving out IP addresses in North America, is promoting a rapid move to IPv6. ARIN says that 19% of the IPv4 addresses are still available, while 68% have been allocated and 13% percent are "unavailable," whatever that could mean. There are 4.3 billion IPv4 addresses, or 2^32 while IPv6 has 2^128 addresses, or 16 billion-billion.
There have been efforts to get more mileage out of IPv4 by using tricks like conversions to IPv6 or using duplicate IPv4 addresses within a firewall. This has helped extend the lifespan of IPv4 but it only prolonged the inevitable. The U.S. is most likely to feel the pinch because it's the most dependent on IPv4 and has the most new devices coming online. The federal government has mandated that by mid-2008 all federal agency backbones should go to IPv6. IPv6 advocates have focused on just the IP address space rather than some of the functions of IPv6, such as improved security and multicasting. For this reason, businesses, which would make the biggest positive impact by moving to IPv6, do not see a reason to take the plunge.
News source: InternetNews