2010 could be the last year for IPv4

September 8, 2009 – 5:56 PM

We’ve known we would run out of IPv4 addresses since 1981, when the Internet Protocol was standardized. The numbers dictate that there will never be more than 4,294,967,296 different IPv4 addresses. (4 billion and change being the number of combinations that can be made with IPv4’s 32 address bits). Before 1993, addresses were given out in very large blocks because of technical limitations in routing protocols. This limitation was lifted, but around the same time, the Internet started to become more mainstream, requiring more and more addresses.

This was also the moment the IETF realized that at some point, we’d run out of IP addresses. Its estimated date for the well to run dry was 2005. Although they got the year wrong, they were right about their notion that 32 bits wasn’t enough for the decades to come.

The invention of network address translation (NAT), which allows multiple systems to share a single address, has been credited for stretching the life of IPv4, but two other technologies were also very important. Variable length subnetting makes it possible to give different subnetworks the appropriate size address block, and ethernet switching made it possible to have much larger subnets, reducing wasteful subdivision of networks.


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