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

Brian E Carpenter <brian.e.carpenter@gmail.com> Wed, 25 July 2018 03:37 UTC

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To: Wassim Haddad <wassim.haddad@ericsson.com>, "internet-area@ietf.org" <int-area@ietf.org>
Cc: "intarea-chairs@ietf.org" <intarea-chairs@ietf.org>
References: <F227637E-B12D-45AA-AD69-74C947409012@ericsson.com>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
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Date: Wed, 25 Jul 2018 15:37:48 +1200
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Subject: Re: [Int-area] WG Adoption Call: IP Fragmentation Considered Fragile
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+1 for adoption.

However, I am a bit concerned about this key recommendation:

>    Application developers SHOULD NOT develop applications that rely on
>    IPv6 fragmentation

It isn't obvious to me that this is an algorithmic requirement. If the
application runs over TCP, how does the developer ensure that TCP will
use an MSS that avoids the need for fragmentation? (The UDP situation
is a bit clearer, but RFC8085 introduces considerable complexity, unless
we accept that the Internet MTU for UDP is 576 or 1280.)

Regards
   Brian