A straightforward transition plan (was: Re: V6 still not supported)

Ca By cb.list6 at gmail.com
Mon Mar 28 13:45:50 UTC 2022

On Mon, Mar 28, 2022 at 6:22 AM Philip Homburg <pch-nanog-2 at u-1.phicoh.com>

> >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.
> Transition to IPv6 so far seems to have consisted of 3 phases:
> 1) Lots of tunnels due lack of a wide spread IPv6 backbone.
> 2) Early adopters being happy that they can run IPv6 native, usually as
>    dual stack.
> 3) Lots of people looking into IPv6-only.
> I'd say 1) mostly worked. 6to4 was a bit of mess. But otherwise tunnels
> worked. Obviously, deploying IPv6 using tunnels is a lot more complex
> than deploying native IPv4 without NAT.
> From a technical perspective 2) just works. From an operational perspective
> it is about twice as expensive as IPv4-only. So 2) is popular with people
> who really want 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'
> 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.

I think what you mean to say is you don’t like NAT64.

You may also be trying to say you disapprove of how history unfolded.


But it may be worth acknowledge that some small and some very large (100M
mobiles, growing FWA broadband business) have happily operated NAT64 for
coming on 10 years  with no problems or regrets.

Yes, we would like the internet to be on a single unified and high scale
address family, but we all play the hand we are dealt.

> 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.
> In my opinion, It is clear that during the time IPv6 was developed, any
> solution involving NAT would have been rejected.
> So I'm confused, what transition technology was achievable (also in the
> political sense) but not delivered?
> 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.
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