Re: IPv6 only host NAT64 requirements?

Mikael Abrahamsson <> Mon, 20 November 2017 06:35 UTC

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Date: Mon, 20 Nov 2017 07:35:02 +0100 (CET)
From: Mikael Abrahamsson <>
To: Mark Andrews <>
cc: Ole Troan <>, 6man WG <>
Subject: Re: IPv6 only host NAT64 requirements?
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On Mon, 20 Nov 2017, Mark Andrews wrote:

> Well as this stage you can say that there are ISP that are deploying IPv6-only on
> the access network with DS-Lite to provide IPv4 as a service.  If you want your
> host to be able to connect directly to such ISPs you need to add support to detect
> that DS-Lite is in use (a IPv6 DHCP option) and bring up a IPv4 in IPv6 tunnel to
> the ISPs B4 router.

Most ds-lite networks are DOCSIS networks, and no host can connect 
directly to that. They'll end up behind a router, which will give the host 
a dual stack service. Sure, you can bridge the modem but the expectation 
is still that you'll connect a ds.lite capable router to that.

> You stop talk ipv6-only and start talking ipv6-only access + ipv4 as a service.

Same thing. Not helping.

> It’s only a “catch 22” because people fail to look at the options 
> available.  ISPs are going ipv6-only access + ipv4 as a service because 
> it is easier to manage than dual stack access + 44CGN.  Many ISPs 
> deliver CPE routers that support DS-Lite so the customer still see IPv4 
> + IPv6.

No, ISPs are not doing that, because hosts do not work properly in this 
scenario. iOS and Android does, but nothing else. So the "else" software 
vendors can just sit back, do nothing and play chicken race.

> The question to host vendors is “do you want your machines to be able to 
> connect directly to ISP’s that have ipv6-only access networks or not?” 
> Ipv6-only access networks are a reality.

I doubt vendors get any feature requests to support this scenario. When 
it doesn't work, people will blame the ISP. This means ISPs won't deply 

Mikael Abrahamsson    email: