In early 2011 the Internet Assigned Numbers Authority (IANA) allocated the last block of IPv4 addresses to various countries and warned that at the rate of historic usage that all those numbers would get gobbled up by ISPs within a few months. They further foresaw all sorts of new demands for IP addresses for new industry products like wearables, BYOD devices being connected to corporate WANs, an explosion of smartphones in the developing world and the early stages of the Internet of Things.

The IANA warned then that ISPs should begin migrating to IPv6 to avoid running out of IP addresses. But here we are almost four years later and a lot of ISPs still have not converted to IPv6. And yet somehow we are not quite out of numbers. The American Registry for Internet Numbers (ARIN) for the United States and Canada is still handing out IP addresses even today. How is that possible?

The major Internet players in the markets developed ways to conserve and reclaim IP addresses. At the end of 2013 ARIN still had 24 million addresses available. ARIN has been able to stretch the numbers by doing things like reclaiming IP addresses from dead ISPs, and by doling out IP addresses in much smaller blocks than historically. ARIN was predicting that those addresses would be gone before the end of 2014. But again the industry confounded them and there were still 16 million IP addresses at the end of 2014. You can see the count of available addresses at this web site, which is updated weekly.

So is now finally the time to convert to IPv6 or can the industry stretch this further? The issue is going to be of the most concern for growing networks that need a lot of new addresses. If you are growing you might should  convert to IPv6 before you find yourself stopped dead due to lack of IP addresses. ISPs that are not growing are probably good for some time since they can usually use numbers abandoned by old customers and assign them to new ones.

Why haven’t more ISPs converted to IPv6? There are a number of reasons.

• IPv6 is not backwards compatible and once you convert you need to run what is called a dual stack that will process both IPv4 and IPv6 addresses. And you will have to do that until IPv4 addresses are finally dead.
• The conversion to IPv6 can be expensive. Every part of your network needs to be IPv6 compatible – that means core hardware, end-user hardware, your Internet backbone provider and even content providers on the web.
• Not all of the content on the Internet is IPv6 compatible. Almost every major site like Google, Yahoo, Facebook and anybody else with a household name is now IPv6 compatible, but there are older content providers who have not bothered, and maybe who will never bother to make the conversion. (And it’s not so much the content, but the servers they sit on).
• There is no problem buying new hardware that is IPv6 compatible. So any new gear being installed today is already IPv6 compatible. But this is no help for older routers and gear that is not easily upgraded, and many companies are holding off to avoid the capital outlay or upgrades that will be needed to convert to IPv6. There probably is no way to upgrade a 10-year old DSL modem or a DOCSIS 1.1 modem to IPv6 without changing devices.

But we are finally seeing some large players converting. For example, Comcast converted all of their cable modem customers to IPv6 during 2014. But some other large ISPs are still holding back. Other parts of the industry have converted – most smartphones now use IPv6 as well as new game consoles.

Now that some large ISPs have converted and most of the web has converted most industry experts expect the rate of conversion to accelerate. Small ISPs need to pay attention to what is happening with IPv6 because you don’t want to be the last one to make the conversion. Once most of the rest of the world has converted you can expect to start having compatibility problems in unexpected places. And eventually the large carriers are going to declare IPv4 dead and cut it off. I’m thinking that most small ISPs ought to finally think about converting by no later than next year. If you wait longer than that it becomes a crap shoot.