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

Joel Jaeggli <> Sat, 25 August 2018 20:47 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id F3F97130DDA; Sat, 25 Aug 2018 13:47:10 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -6.899
X-Spam-Status: No, score=-6.899 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_HI=-5, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id fzFesmiHc35w; Sat, 25 Aug 2018 13:47:08 -0700 (PDT)
Received: from ( [IPv6:2001:418:1::81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id D06F2130DD5; Sat, 25 Aug 2018 13:47:08 -0700 (PDT)
Received: from Joels-MacBook-Pro.local ([IPv6:2607:fb90:a69f:71ba:34df:cb7:87a6:dc3d]) (authenticated bits=0) by (8.15.2/8.15.2) with ESMTPA id w7PKklIY025042; Sat, 25 Aug 2018 20:46:56 GMT (envelope-from
X-Authentication-Warning: Host [IPv6:2607:fb90:a69f:71ba:34df:cb7:87a6:dc3d] claimed to be Joels-MacBook-Pro.local
To: Toerless Eckert <>, Mikael Abrahamsson <>
Cc: int-area <>,
References: <> <> <> <> <> <> <> <> <> <> <>
From: Joel Jaeggli <>
Message-ID: <>
Date: Sat, 25 Aug 2018 13:46:47 -0700
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:60.0) Gecko/20100101 Thunderbird/60.0
MIME-Version: 1.0
In-Reply-To: <>
Content-Type: multipart/mixed; boundary="------------9B3ADDCA5B6ED2662AC74211"
Content-Language: en-US
Archived-At: <>
Subject: Re: [Int-area] WG Adoption Call: IP Fragmentation Considered Fragile
X-Mailman-Version: 2.1.27
Precedence: list
List-Id: IETF Internet Area Mailing List <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Sat, 25 Aug 2018 20:47:11 -0000

On 8/24/18 8:24 PM, Toerless Eckert wrote:
> On Fri, Aug 03, 2018 at 09:48:25AM +0200, Mikael Abrahamsson wrote:
>> I've kept saying "Networks must support ip fragmentation properly.
> Why ? Wheren't you also saying that you've got (like probably many
> else on this thread) all the experience that only TCP MSS gets you
> working connectivity in many case (like hotels) ?
> 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.
> 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. 

It's actually not that useful if it's an icmp message. because it's
going to fail in many cases where it has to be hashed to a destination.
just  like non-initial fragements do...

4821 gets you there with tcp.

> Of course. Will take a decade to get ubiquitously deployed, but
> neither IPv4 nor IPv6 will go away, only the problems with fragmentation
> will become worse and work if we do not have an exit strategy like this.
It's not going to be ubiquitously deployed because it's not going to work.
> If we don't try an exit strategy like this, we will just get what
> Joe said, the complete segmentation of the Internet with more and
> more L4 or even higher layer proxies.
> Btw: +1 for adopting the doc as a WG item, but primarily because everything
> before section 7 is on a way to become a good read of reality. Section
> 7 recommendations is only a faith based exercise (praying) as long as it tries to
> get the job done primarily by appealing to application developers.
> Cheers
>     Toerless
> _______________________________________________
> Int-area mailing list