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Re: TCP and IPV6_USE_MINMTU

Brian E Carpenter <brian.e.carpenter@gmail.com> Sat, 17 October 2015 22:12 UTC

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Subject: Re: TCP and IPV6_USE_MINMTU
To: Mark Andrews <marka@isc.org>
References: <20151016034110.306563A939AB@rock.dv.isc.org> <20151016202620.GI1442@verdi> <20151016203155.3D2473AA8817@rock.dv.isc.org> <56217BAB.2040608@gmail.com> <20151016225655.CC0653AA9E81@rock.dv.isc.org>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
Message-ID: <5622C7A6.6000200@gmail.com>
Date: Sun, 18 Oct 2015 11:11:50 +1300
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I think that
(a) This draft should not be Informational, it should become a BCP.
(b) I suspect it belongs in v6ops rather than 6man, since it doesn't
change anything in the standards.
(c) I think it doesn't say quite enough about how this is a very serious
and recurrent operational problem which causes real damage to IPv6 deployment.

Also - it's not OK that POSIX hasn't yet picked up the advanced socket API
and that it isn't available in all programming languages with socket calls.
We, for some value of "we", need to campaign to get this fixed.

    Brian


On 17/10/2015 11:56, Mark Andrews wrote:
> In message <56217BAB.2040608@gmail.com>, Brian E Carpenter writes:
>> On 17/10/2015 09:31, Mark Andrews wrote:
>>>
>>> In message <20151016202620.GI1442@verdi>, John Leslie writes:
>>>> Mark Andrews <marka@isc.org> wrote:
>>>>>
>>>>> Please see
>>>>> https://www.ietf.org/id/draft-andrews-tcp-and-ipv6-use-minmtu-00.txt
>>>>>
>>>>> It addresses what should be obviously done but isn't by many
>>>>> implementations.
>>>>
>>>>    Alas, this draft gives no clue _how_ to check IPV6_USE_MINMTU ...
>>>> (or, for that matter, how to set it).
>>>>
>>>>    One could reasonably guess that s/he should look through RFC3542 to
>>>> find how to check this; but RFC3542 contains no such string. (It does
>>>> contain the string IPV6_USE_MIN_MTU; but I don't feel justified in
>>>> guessing that far astream...
>>
>> Incidentally, it recently came to my attention that standard Python
>> doesn't support RFC3542. I don't know how widespread that issue is, but
>> it may be behind some of these broken MSS deployments.
>>
>>     Brian
> 
> The entire advanced socket API is poorly supported because POSIX
> didn't pick it up.
> 
> That said I've updated the document based on the feedback received
> to date.
> 
> https://tools.ietf.org/html/draft-andrews-tcp-and-ipv6-use-minmtu-03
> 
>>> Yes, I typo'd that, repeatedly.
>>>  
>>>>    Perhaps adding a citation to the specific section of a particular
>>>> RFC would help?
>>>>
>>>> --
>>>> John Leslie <john@jlc.net>

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