Back in February 2011, when the global Internet Assigned Numbers Authority (IANA) allocated the last blocks of IPv4 address space to the five regional Internet registries (that further distribute IP addresses), many experts warned of a fast approaching crisis that would severely affect Internet connectivity.

It was believed that the available IPv4 addresses would exhaust within months. But today, three years later, American Registry for Internet Numbers (ARIN) is still bestowing IPv4 addresses in the US and Canada. In an article titled Whatever happened to the IPv4 address crisis?Lee Schlesinger, Network World's former test center director shared his views on how far can we go this way and why the IPv6 adoption rate is still slow.

According to John Curran, President and CEO of ARIN, the organization still has "approximately 24 million IPv4 addresses in the available pool for the region," which he predicts will be handed out by "sometime in 2014". But that doesn't mean the shortage will begin this year, as addresses will still be available to be assigned to operators' clients for a while longer. Moreover, stable networks (that aren't expanding) would easily reuse addresses, Schlesinger argues.

So, what happened to the crisis everyone was talking about? Well, it's just been pushed out due to multiple factors. Schlesinger touches upon some of them, including use of carrier-grade network address translation (CGNAT), carriers directly purchasing IP addresses from each other, and ARIN reclaiming unused addresses.

Coming to IPv6, Schlesinger tries to answer an important question: If this new IP version is better, and has the ability to provide 2^128 IP addresses, why hasn't everyone just switched over to it?

Firstly, it isn't backward compatible with IPv4, and needs to be implemented end to end. Secondly, as John Brzozowski, fellow and chief architect for IPv6 at Comcast Cable puts it: "Service providers didn't want to implement IPv6 because the content providers weren't there, and content providers didn't want to implement it because the service providers weren't there", a classic chicken-and-egg problem.

Despite of all the hurdles, Schlesinger says that there is steady progress in IPv6 adoption and implementation. He supports his argument through various statistics, including a statistical graph from Google, which shows that the percentage of users that access Google over IPv6 has increased over the past few years.

Schlesinger believes that IPv4 addresses will remain in use for some time to come, and concludes by quoting Phil Roberts, technology program manager for the Internet Society, who says, "It takes a while to transition. After all this is done it would be a great graduate thesis for someone to see why it has taken so long".

You can read Lee Schlesinger's full story here.

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