Re: Last Call: <draft-ietf-6man-rfc1981bis-04.txt> (Path MTU Discovery for IP version 6) to Internet Standard

Joe Touch <touch@isi.edu> Tue, 07 February 2017 18:26 UTC

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Subject: Re: Last Call: <draft-ietf-6man-rfc1981bis-04.txt> (Path MTU Discovery for IP version 6) to Internet Standard
To: otroan@employees.org, "Eggert, Lars" <lars@netapp.com>
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From: Joe Touch <touch@isi.edu>
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Date: Tue, 7 Feb 2017 10:25:33 -0800
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On 2/4/2017 10:40 AM, otroan@employees.org wrote:
> Lars,
>
>>> My apologies: my comments were probably misleading. Certainly, this
>>> document is simply RFC1981 to Std, and hence recommending RFC4821 would
>>> be kind of ou of scope, here.
>>>
>>> That say, one might wonder to what extent, and for the general Internet,
>>> RFC1981 can be considered succesful (given the filtering of ICMP
>>> messages). -- i.e., at this point in time you wouldn't rely on RFC1981
>>> (icmp-based pmtud) for path-mtu discovery.
>> What Fernando said: I'm certainly not opposed to lifting this to Standard, but it is painting an incorrect picture - PLPMTUD is de facto mandatory these days, and has been for years.
> While I'm all in favour of PLMTUD. It doesn't seem like a complete solution.
> PMTUD on the other hand supports all protocols on top of IP.
If by "supports" you mean "doesn't work", then yes. That's why we now
have PLPMTUD.

> Looking just at our specifications, we cannot state that PLMTUD can replace PMTUD. Take RFC2473 (IPv6 tunnelling) for example.
See draft-ietf-intarea-tunnels, esp. v03 Section 5.5.2

(yes, that doc has expired while we're preparing the 04 update, which
should be issued shortly)

Joe