On 25 Mar 2022, at 2:27 PM, Philip Homburg <pch-nanog-2@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