On 25 Mar 2022, at 2:27 PM, Philip Homburg <pch-nano...@u-1.phicoh.com> wrote: > >> If by ?straightforward transition plan? one means a clear and rational set >> of >> options that allows networks to plan their own migration from IPv4-only to >> IPv >> 6, while maintaining connectivity to IPv4-only hosts and with a level of >> effor >> t reasonable comparable to just running IPv4, then I would disagree, as such >> a >> n "IPng transition plan? was achievable, expected, and we collectively >> failed >> to deliver on it (as noted below) > > I'm a bit confused about the achievable part. > > Obviously, the adoption of IPv6 without a clear transition plan was a process > failure. However, it is not clear to me that waiting a few years would > have brought something much better. And waiting more than a decade would > mean that today there would not be a mature IPv6. > ... > The big issue is 3). If we look at the current internet, there are parties > who lack IPv4 addresses and want to switch to IPv6. Obviously, they > want to be IPv6-only. The lack of IPv4 address makes dual stack even harder. > On the other hand, there are parties who have enough IPv4 addresses and > have no reason to switch to IPv6. > > So we are clearly in the situation of 'migration from IPv4-only to IPv6, > while maintaining connectivity to IPv4-only hosts'
Correct (although I will also point out that having zero IPv4 addresses isn’t really the problem but rather “not enough IPv4 space for their networking needs” – in the ARIN region, for example, organizations can obtain a small amount of IPv4 address space specifically for purposes of IPv6 transition technology use - it’s quite necessary for nearly any IPv6/IPv6 interoperability solution since they need to have an IPv4-facing interfaces) > It should be clear that an IPv4-only host only speaks IPv4. This means that > communication with an IPv4-only host has to be IPv4. So either the > IPv6-only host or something in the network has to speak IPv4. If the > IPv6 host speaks IPv4 then we get dual stack, which has been rejected > as a broken solution. Technically, it is also possible to tunnel IPv4 > packets, then the host is in some sense dual stack, but most of the network > is not. However, automatic tunnel configuration is hard, and tunnels > tend to be fragile. > > So the only option is a device in the network that translates between > IPv6 and IPv4. Currently we have such a protocol, NAT64. And from > a technical point of view it is a disaster. We actually have an abundance of technical solutions that provide some degree of IPv6/IPv4 interoperability, all with various tradeoffs, and which address various deployment scenarios such as whether the network service has involvement in the individual CPE, DNS resolution, ability to alter/profile applications, etc… it’s a rather complex mess, and there’s far more solutions in use that just NAT64. > Looking back, we can say that the only feature of IPv6 that makes people > invest in IPv6 is the bigger address space. So it is safe to say that > most of the internet would have waited to invest in IPv6 until we were > (almost) out of IPv4 addresses. So by its very nature this transation > between IPv6 and IPv4 would have NAT component. <chuckle> Full agreement there… one would have expected a strong focused effort in making a small number of standard NAT-based interoperability protocols for IPng, including working through the transition scenario implications. > In my opinion, It is clear that during the time IPv6 was developed, any > solution involving NAT would have been rejected. Pretty much correct… As you may be aware, there was a large focus on tunnel-bases solutions (so that various islands of IPv6 exploration could be interconnected) but actual NAT-based interoperability wasn’t in the cards. > So I'm confused, what transition technology was achievable (also in the > political sense) but not delivered? Well, I think you’ve hit the nail on the head - we certainly could have delivered on the actual IPng technical requirements for a straightforward transition plan (and ended up with a short finite number of well-tested protocols with far more attention paid to them starting 10 years earlier in the process) rather than present cornucopia of last-minute solutions of various technical strength – alas, taking that path of actually working on NAT-based interoperability solutions did not align with the culture/politics of the IETF. > If there is a magical transition technology that allows an IPv6-only host to > talk to an IPv4-only host, then let's deploy it. DNS64/NAT64, DS-Lite, 6rd, 464XLAT, MAP-T, MAP-E, … pick a transition protocol and see what happens! (with more coming every year...) FYI, /John