Re: [tsvwg] I-D Action: draft-ietf-tsvwg-udp-options-09.txt

Carsten Bormann <cabo@tzi.org> Fri, 18 December 2020 14:17 UTC

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From: Carsten Bormann <cabo@tzi.org>
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Date: Fri, 18 Dec 2020 15:17:50 +0100
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To: Joseph Touch <touch@strayalpha.com>
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Subject: Re: [tsvwg] I-D Action: draft-ietf-tsvwg-udp-options-09.txt
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On 2020-11-26, at 01:14, Joseph Touch <touch@strayalpha.com> wrote:
> 
> 	• This doc now updates ROHC 3095 too
> 		• puts it in line with more recent header compression standards that we caught
> 		• UDP header compression should ever have assumed that UDP Length is implicit based on IP length

Specifically, the draft now says:

   This document hereby deprecates the requirement asserted in the UDP
   profile for Robust Header Compression (ROHC)[RFC3095], noted here:

      "The Length field of the UDP header MUST match the Length
       field(s) of the preceding subheaders, i.e., there must not
       be any padding after the UDP payload that is covered by the
       IP Length.”

This change is highly confused.

You indeed cannot initialize an IR header chain from from a UDP packet where this does not match.  So you would send that uncompressed.  If this MUST were changed, the receiver no longer would be able what length to put into decompressed UDP packets.

Somehow, I feel like responding to an errata report that needs to be rejected…

Grüße, Carsten