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

Joel Jaeggli <joelja@bogus.com> Sat, 25 August 2018 20:47 UTC

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To: Toerless Eckert <tte@cs.fau.de>, Mikael Abrahamsson <swmike@swm.pp.se>
Cc: int-area <int-area@ietf.org>, intarea-chairs@ietf.org
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From: Joel Jaeggli <joelja@bogus.com>
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Date: Sat, 25 Aug 2018 13:46:47 -0700
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Subject: Re: [Int-area] WG Adoption Call: IP Fragmentation Considered Fragile
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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
>
>
>
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