Philip, IPv6-only web content is unlikely to show up in the near future, that is true. That said, I believe it is reasonable to expect that once we reach a critical mass of IPv6 end-user deployment, some clever entrepreneur will develop a really awesome service that only works with IPv6. Which in turn will lead to an even greater incentive for the ISPs that are IPv4-only at that point to get busy deploying native IPv6, or risk losing customers who want to use said awesome service. As the RIPE NCC's measurements clearly show, 6to4 is unlikely to provide adequate quality for the user to be happy in this case. On web content side, the value of IPv6 compared to legacy IPv4 is to provide the optimal performance while at the same time keeping the costs down. IPv4 depletion will happen and the only way an ISP can deal with that is to install centralised NAT systems in order to let subscribers share IPv4 addresses. These systems are likely to be very expensive compared to routers, as they need to remember the state of every single flow that traverses them. So it is in the content provider's interest to deliver the web pages over IPv6 in order to use the optimal direct path to the end user that's unencumbered by these NAT systems, and it is also in the ISP's interest that the end users use IPv6 to access online content as much as possible, because this allows the ISP to buy centralised IPv4 NAT systems that are scaled for smaller traffic levels, i.e., cheaper models. Centralised NAT systems will also break a number of existing applications that rely on protocols like UPnP and NAT-PMP in order to allow applications inside of the NAT device to listen for connections originating from the outside of the NAT box. BitTorrent is a good example of such an application. UPnP and NAT-PMP only works with single-level (residental) NAT; once the ISP adds a centralised NAT system to the mix, UPnP and NAT-PMP can no longer function. So it might just be that it's not the arrival of an «awesome new IPv6-only service» that will push IPv6 deployment forward, it could just as well be that the already awesome services that people today use successfully through single-level IPv4 NAT will eventually come to rely on IPv6, because the inevitable ubiquity of centralised IPv4 NAT systems will prevent them from functioning properly any more on the legacy IPv4 internet. Tore

Philip,

"Once we get to IPv6 deployment" Again you assume that this is inevitable. It is not.

My house runs on IPv4 today and that is not going to change in the future.

My weighing scale is on the Internet. Every time I weigh myself it tweets the result on twitter. I am quite happy allowing that device outbound communication. I am not going to allow it to accept incoming calls.

You still don't get it. My tolerance of technical issues is orders of magnitude higher than that of the typical Internet user. I object to the idea that somehow the Internet can be allowed to break for IPv4 users during the inevitable IPv6 transition. The rate at which ISPs and backbone providers deploy IPv6 is irrelevant. As long as every Internet user has IPv4 connectivity and only some have IPv6 connectivity, there will be absolutely zero demand for IPv6 only anything. There is not one ISP or backbone provider that is going to break their IPv4 service to facilitate a move to IPv6. Not one. I don't care what public commitments they appear to make. It is not happening. There is a deployment trap here and people who ignore it are wasting their time and the time of everyone else that they tell their breathless stories about IPv6 deployment to. To date the IPv6 deployment strategy of IETF has been to make IPv6 deployment matter to end users as much as possible by intentionally sabotaging NAT support. That has not worked and will never work. The only way to deploy IPv6 is to make sure that it does not matter to applications AT ALL. Making NAT44 / NAT64 / NAT 46 / NAT66 work perfectly and transparently are inescapable preconditions for making IPv6 deployment possible. So worrying about the Internet breaking during the transition to IPv6 is to worry about the wrong thing. What we should be worried about here is that these figures are showing is that as things stand, the transition to IPv6 is not going to happen. Now we could all sit round and have the usual happy talk about how everyone should move to the wonderful world of IPv6 for the greater good of the net even if that means worse connectivity. Or we could take a realistic view of the problem and think about ways to fix it.

No such thing as a v6 only world. And too great a legacy base of v4.

Time will tell if en when IPv6-only networks will become more common, I believe they will, in due time because of the economics of it all: IPv4 will be a scarce resource soon, IPv6 won't (any time soon), so as soon as IPv4 becomes more expensive, while not providing additional benefits over IPv6 you have a natural driver towards IPv6. All artificial means of providing more IPv4 address space (NATs in NATs) cost money and performance and will hamper development. I agree with PHB that we should look at translation mechanisms, and as we measured 6to4 is currently problematic, but I don't agree all translations are needed. For instance if NAT64/DNS64 works really well, that is an incentive for end-users to go IPv6 only, and still reach the old IPv4 world, and the emerging IPv6 world (see http://ripe61.ripe.net/presentations/140-ripe_rome_jari.pdf for how workable this is already). If you don't believe IPv6 transition is happening, look at ASes deploying IPv6: http://v6asns.ripe.net over time. The clear trend there is that more and more ASes are deploying. For more discussion on IPv6 transition myths: http://www.circleid.com/posts/ipv6_and_transitional_myths/

Again, 'once IPv6 reaches critical mass' ... 'people will adopt'. Network effects break both ways. Until critical mass is reached, the network effect is the chicken-and-egg problem. I am fully aware that backbone providers are racking equipment that is IPv6 capable. But that does not mean that the IPv6 transition is guaranteed. Content targeted at particular niches has always had a place. But IPv4 vs IPv6 is simply not a distinction that 99% of users care to be aware of. Back in 2000, VeriSign acquired Network Solutions for the express purpose of deploying DNSSEC. Ten years later, we are still talking about DNSSEC deployment. I agree that we need to deploy IPv6, but the idea that the transition is guaranteed is making it much harder. We have already seen practical deployment proposals cancelled on spurious grounds by an IETF clique because they see the IPv6 transition as a train they can hook their personal priorities to. As a result we were set back three years with practical middlebox specs. Failure is always an option. Failing to consider the possibility of failure makes it more likely you will fail. With DNSSEC there was far too much happy talk about how inevitable the spec was and too little consideration of how difficult deployment was. Again people thought that they could hold the system hostage to their personal priorities. In one DNSEXT meeting it was proposed that if the current spec could not be deployed in .com, that we should reduce the size of .com. The speaker was cheered. They should have been laughed out of the room and ignored as a lunatic.

Philip, There is a simpler way to explain things, if you consider these two basic facts: 1) The Internet is not going to stop growing 2) IPv6 is the *only* way to continue growth of the Internet. So we can conclude that widespread IPv6 adoption is inevitable. See my article here: http://wp.me/pLN1x-3d I also recently wrote this post about IPv6 as an Internet access market disruptor. I believe deployments are going to be largely driven by this: http://wp.me/pLN1x-7B Dan

The first assumption is probably true, the second is not. Carrier grade NAT will be capable of meeting the needs of 90% of Internet users. So it is foolish to assume that Internet growth will force deployment of IPv6. Your analysis is like saying that electric cars are inevitable because supply of gas is insufficient to meet global needs. That may well be true at some level, but there are alternatives. Wealthy nations like the US can afford to invade countries like Iraq and just take what they need. Some people are advocating an attack on Iran for essentially the same reason (though they state different ones in public). War is clearly not a sane alternative to planning a sound energy policy. But anyone who wants to achieve a sound energy policy has to cope with people who are plainly idiots but are treated with tremendous respect The electric car is a rather easier sell than IPv6 since it is at least obvious that the price of gas is going to affect everyone. 'We cannot fail' is the very mindset that I think is harming the prospects of IPv6 adoption. Deployment of IPv6 is not assured. Far too many people are relying on the assumption that it is as an excuse to tie their own little pet notions to the scheme. At present we still don't have a credible transition plan that takes account of the needs of actual end users. The anti-firewall/anti-NAT constituency have seized on IPv6 as being the opportunity to ensure a borderless Internet in which every machine is permanently exposed to attacks from outside.