Hi Ole,
-----Original Message-----
From: otroan(_at_)employees(_dot_)org [mailto:otroan(_at_)employees(_dot_)org]
Sent: Tuesday, February 14, 2017 10:33 AM
To: Stewart Bryant <stewart(_dot_)bryant(_at_)gmail(_dot_)com>
Cc: Templin, Fred L <Fred(_dot_)L(_dot_)Templin(_at_)boeing(_dot_)com>; Brian
E Carpenter <brian(_dot_)e(_dot_)carpenter(_at_)gmail(_dot_)com>;
gen-art(_at_)ietf(_dot_)org; 6man WG
<ipv6(_at_)ietf(_dot_)org>; ietf(_at_)ietf(_dot_)org;
draft-ietf-6man-rfc1981bis(_dot_)all(_at_)ietf(_dot_)org
Subject: Re: [Gen-art] Review of draft-ietf-6man-rfc1981bis-04
Stewart,
*If* you care about packet loss, then your only option is to probe the
path with with
synthetic data that exactly mimics the live data, or not to probe at all
and live
with the 1280. As I said 1280 is pretty close to 1496 which is all most
networks
will give you in practice.
Yes, but sending at 1280 does not work for IP tunnels. The whole purpose of
the minimum MTU was to give space for tunnel headers
(1500-1280).
But, if non-tunnel links set a 1280 MTU which is perfectly OK with the standard
then
there is no space for headers. Given the issues with classical PMTUD then (plus
the
non-applicability of RFC4821 for tunnels) the only solution for tunnels is
fragmentation.
I'll let Joe step in if he wants to.
Thanks - Fred
When I think about the people asking for fast re-route to minimise packet
loss, it seems
very strange to deliberately induce loss to try to stretch the MTU by 15%.
Please show the data that there is significant loss. The measurements I have
found has not shown that.
If not, then let's please leave that argument on the shelf.
(And please don't read me wrong, I think we should get DNS fixed, that we
should fix the IP tunnelling protocols, and that we should
get IP fragmentation deprecated).
But right here, right now. PMTUD is for many problems the only solution on
the table.
We as a community can choose not to elevate the standard of course, and that
will of course not have any big consequence.
Are you afraid that elevating 1981, will hinder people from working on new
and better solutions?
Best regards,
Ole