IETF Logo Mail Archive

Re: [Int-area] WG Adoption Call: IP Fragmentation Considered Fragile

Toerless Eckert <tte@cs.fau.de> Sun, 26 August 2018 21:27 UTC

Return-Path: <eckert@i4.informatik.uni-erlangen.de>
X-Original-To: int-area@ietfa.amsl.com
Delivered-To: int-area@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 1501B130E63; Sun, 26 Aug 2018 14:27:10 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -4.199
X-Spam-Level:
X-Spam-Status: No, score=-4.199 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.001, RCVD_IN_DNSWL_MED=-2.3] autolearn=ham autolearn_force=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id xx5J11yvV2hc; Sun, 26 Aug 2018 14:27:07 -0700 (PDT)
Received: from faui40.informatik.uni-erlangen.de (faui40.informatik.uni-erlangen.de [IPv6:2001:638:a000:4134::ffff:40]) (using TLSv1.2 with cipher ADH-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 6C0F8130E88; Sun, 26 Aug 2018 14:27:07 -0700 (PDT)
Received: from faui48f.informatik.uni-erlangen.de (faui48f.informatik.uni-erlangen.de [IPv6:2001:638:a000:4134::ffff:52]) by faui40.informatik.uni-erlangen.de (Postfix) with ESMTP id 35A8D548326; Sun, 26 Aug 2018 23:27:03 +0200 (CEST)
Received: by faui48f.informatik.uni-erlangen.de (Postfix, from userid 10463) id 1D8F7440054; Sun, 26 Aug 2018 23:27:03 +0200 (CEST)
Date: Sun, 26 Aug 2018 23:27:03 +0200
From: Toerless Eckert <tte@cs.fau.de>
To: Mikael Abrahamsson <swmike@swm.pp.se>
Cc: Tom Herbert <tom@herbertland.com>, int-area <int-area@ietf.org>, intarea-chairs@ietf.org
Message-ID: <20180826212702.pxkhrogoqo2wv7gr@faui48f.informatik.uni-erlangen.de>
References: <CALx6S34qmKngi3hK_PVrJA1DMa5kfaLww3jfqRKN=up5v0Y0Ww@mail.gmail.com> <8D23C8B1-C2DA-4A8B-A2BE-8CCF6233B3A5@strayalpha.com> <D1D5EDCE-7C43-4CD8-947C-AA43CDB18892@employees.org> <1B04E207-08FA-400F-BBED-67379FEFD64E@strayalpha.com> <137751A3-7C52-4CCF-AE9C-B99C4A85EFC1@strayalpha.com> <alpine.DEB.2.20.1808021749020.19688@uplift.swm.pp.se> <CALx6S35kw2dodgG2L3LE3A5y8RYEXy6izQWgrQTwg7-yPqpzOg@mail.gmail.com> <alpine.DEB.2.20.1808030857370.19688@uplift.swm.pp.se> <20180825032457.ol5rlrr7h2kqi6px@faui48f.informatik.uni-erlangen.de> <alpine.DEB.2.20.1808250827360.23215@uplift.swm.pp.se>
MIME-Version: 1.0
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.20.1808250827360.23215@uplift.swm.pp.se>
User-Agent: NeoMutt/20170113 (1.7.2)
Archived-At: <https://mailarchive.ietf.org/arch/msg/int-area/zR2NcXZ3cT2ThQF0DbpuaGiRm0Y>
Subject: Re: [Int-area] WG Adoption Call: IP Fragmentation Considered Fragile
X-BeenThere: int-area@ietf.org
X-Mailman-Version: 2.1.27
Precedence: list
List-Id: IETF Internet Area Mailing List <int-area.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/int-area>, <mailto:int-area-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/int-area/>
List-Post: <mailto:int-area@ietf.org>
List-Help: <mailto:int-area-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/int-area>, <mailto:int-area-request@ietf.org?subject=subscribe>
X-List-Received-Date: Sun, 26 Aug 2018 21:27:16 -0000

On Sat, Aug 25, 2018 at 08:32:41AM +0200, Mikael Abrahamsson wrote:
> > IMHO, we (network layer) should accept defeat on network layer
> > fragmentation and agree that we should make it easier for the
> > transport layer to resolve the problem.
> 
> I want to keep the fragmentation requirement for the network.

Why ? Whats the biggest benefit with IPv6 ?

Took us decades to figure out that in-network
fragmentation (as mandaory in IPv4) is not a good thing, and
we eliminated it for IPv6. Why do we hang on to fragmentation 
from the host when tranport layers would be better doing it than the IP
layer ?

Cheers
    Toerless

> > Aka: I would lvoe to see a new ICMPv4/ICMPv6 reply and/or PTB reply option
> > indicating "Fragmented Packets Not Permitted". Any network device which
> > for whatever reason does not like Fragemnts would simply drop
> > fragmented packets and send this as a reply. Allows then the
> > transport layer to automatically use packetization  (such as TCP MSS)
> > to get packets through.
> 
> I am not opposed to this option being created, but you still need PLPMTUD.
> This option might trigger faster PLPMTUD, but it doesn't make the problem go
> away. If the application still keeps sending packets that needs to be
> fragmented, what should the stack do, just send an error to the application?
> Yes, this will mean we will fail faster, but apart from that?
> 
> -- 
> Mikael Abrahamsson    email: swmike@swm.pp.se

-- 
---
tte@cs.fau.de

v2.23.0 | Report a Bug | By Email