Slow ride (on the IPv6 train), take it easy

Imagine riding a train where no one knows when it will reach its destination. Or if it will ever get there. Or worse still if it could even get re-routed along the way to a new destination. And if matters weren’t bad enough, this is the only train to get you where you are going. So you have no option but to take your chances. And ride along. Sounds like a bad dream. Nonetheless that is what the move to Internet Protocol version 6 (IPv6) has often seemed like.

Proposed in 1995 and adopted in 1999, IPv6 adoption has been moving at a considerably less than glacial pace (bit of irrelevant trivia here: the fastest glacier is apparently in Greenland moving over 40 meters in a day). Reliable, error free, efficient end-to-end communication between uniquely identifiable end nodes was the idea with which the Internet (TCP/IP) was conceived. That required each end point to have a unique address. This was all very well during the early Arpanet days. IPv4 was developed for the Arpanet in 1978 with a limit of 4 billion addresses (2 32). Trouble is the 4 billion number quickly turned out to be inadequate. Fast forward to the 2000’s and shortages began to show up. In 2011, the IANA free pool hit zero. Four of the five Regional Internet Registries have run out of addresses. ARIN, which includes the US and Canada, has been the last of the RIR’s to exhaust “IPv4 supplies.”  On the other hand with its 128 bits, we should always have enough IPv6 addresses to go by.

Ideally by now IPv6 should have been waiting in the wings, ready to step in, and take over. But that has not come to pass. Instead IPv6 adoption crossed eight percent in August this year per Google. Therefore about 92 percent of the Internet is still on IPv4. Which means demand for IPv4 is not going away any time soon. With this demand vs. supply imbalance, we should be seeing prices for buying IPv4 addresses in the “secondary market” on the rise. Folks holding on to IPv4 blocks likely have a nicely appreciating asset on their hands, at least in the short term. Should make CFOs happy!

Unfortunately IPv6 was not designed to be backward compatible, which means that the two versions 4 and 6 cannot directly talk to each other without a translator in the middle. If that weren’t the case perhaps IPv6 would have been phased in much sooner. For implementing an end-to-end IPv6 communication, both the end points as well as the intervening network have all got to support IPv6, a requirement that made the transition much harder.

Consequently an IPv4 future is what lies ahead for the next few years. Between the rates of IPv4 depletion and IPv6 transition, there has been quite a mismatch. How has the world been coping? Enter Network Address Translation (NAT) to the rescue (among other workarounds). We started off with NATs at the customer premises. These translated public IPv4 addresses to private addresses inside the customer network. Solved the problem to some extent as not everyone needed a public IPv4 address at least initially. Yet that was not enough to meet surging demand. Then ISPs introduced the next layer of NAT at their end, the Carrier Grade NAT or CGN. Essentially what it did was to assign private addresses to customers and map these to public addresses at the upstream ISP end. Two levels of translation, one on top of the other. Basically ISPs started sharing a single IPv4 address among multiple customers (could be hundreds and even thousands of customers behind a single address). Looking at the packet header, there was no way to identify the user behind it. Only the ISP running the CGN had the information to map packets to individual users. Some law enforcement implications here for sure.

Apparently the CGN solution has not been a big problem for the regular web users: email, web browsing and so on. Where the CGNs have significantly impaired performance has been in things like VOIP, video streaming, and online video gaming (all very popular, growth oriented use cases). What is the benefit to the ISP? One, they can postpone replacing thousands of boxes across their network. Two, extending the life of IPv4 helps realize gains from their own IPv4 stores (estimates run between $10 and $15 per IP address, these numbers should be on the climb). As an aside, trading in IPv4 addresses could become quite profitable. Three, vendors of the expensive CGN boxes certainly have an incentive to keep pushing more of these. A sobering possibility that arises is that the investment in CGN itself acts as a further disincentive to move on to IPv6. Indeed some ISPs might be tempted to just keep on adding the CGNs and pretty much put off IPv6 for a long time.

All this appears to have some parallels with the Y2K shift. Applications needed to be changed to support the four digit date field. There was the need for investment. Of course there was a hard, impossible to avoid deadline. Like it or not the Year 2000 was going to arrive! No workarounds were possible. Hence the move to Y2K was implemented in a timely manner and the year 2000 went off without a hitch. In the case of IPv6, there is no such hard deadline. No pressing need to make the switch. If it can wait, then it will wait. Running out of addresses should have provided the urgency but that was neutralized by NAT boxes among others. There has even been the suggestion that the IPv6 shift could possibly get derailed and converted instead into a CGN transition. Though that does seem to be a remote prospect.

Meanwhile the IPv6 train continues to chug along albeit at a slightly faster pace now. Destination still not in sight. As a virtue, patience for the passengers is strongly recommended. Real slow ride after all. Might as well sit back, relax, take it easy, and enjoy it while it lasts.


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