IPv4 only apps [was: IPv6 only host NAT64 requirements?]

Brian E Carpenter <brian.e.carpenter@gmail.com> Tue, 14 November 2017 01:33 UTC

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Subject: IPv4 only apps [was: IPv6 only host NAT64 requirements?]
To: Ole Troan <otroan@employees.org>
Cc: Philip Homburg <pch-ipv6-ietf-4@u-1.phicoh.com>, 6man WG <ipv6@ietf.org>
References: <m1eEGbJ-0000EhC@stereo.hq.phicoh.net> <D43E103C-27B8-48CF-B801-ACCF9B42533E@employees.org> <m1eEHPS-0000FyC@stereo.hq.phicoh.net> <909eb642-b2a0-2fb5-8f41-297e013ae307@gmail.com> <E6BCB92F-615A-4692-8AF2-D993D5B9AF7F@employees.org>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
Message-ID: <f7baaadf-33c3-7fc2-d90e-872a0f69a5fa@gmail.com>
Date: Tue, 14 Nov 2017 14:33:06 +1300
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On 14/11/2017 13:37, Ole Troan wrote:
> Brian,
> 
>> ...
>>> But for host software there is a lot more incentive to support dual stack then
>>> to do the extra step for NAT64.
>>>
>>> The big problem I see for NAT64 is that for old IPv4-only applications you
>>> have to make two fundamental changes to the application. The first to
>>> make sure that the application handles IPv6 in every possible way. And a
>>> second pass that makes sure that every place where an IPv4 address literal
>>> is handled, works with NAT64.
>>>
>>> For an application writer it is better to try to avoid doing the second pass.
>>
>> I think there is a missing document, and it may well belong in v6ops not
>> 6man: "IPv4 Applications on an IPv6-only Host".
> 
> IPv4 applications do not run on an IPv6 only host, so that's a short document.

No, I don't think so. We haven't done a good job of advising implementers
in this area, and those apps will not go away spontaneously. Tweaking them
for the new world may be much easier than getting them rewritten, in terms
of the incentives in play.
> 
>> Your text above is probably a good summary of what the document needs
>> to cover. (I also suspect that if this document existed, we wouldn't need
>> Jordi's draft attempting to define "IPv6-only".)
> 
> Please take that to a different thread.

Done ;-)

> This thread is about a IPv6 only, single stack host connecting to an IPv6 only network.
> With a backdoor to the IPv4 Internet for legacy destinations.

And that neglects the legacy that most such hosts have inside them.
I have a bunch in the host I'm typing on right now, which is connected
via NAT64 for the week.

    Brian