Re: [tsvwg] Doubts regarding motivation of draft-ietf-tsvwg-iana-dscp-registry-04

Brian E Carpenter <brian.e.carpenter@gmail.com> Tue, 08 May 2018 20:46 UTC

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To: Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>
Cc: "Black, David" <David.Black@dell.com>, "gorry@erg.abdn.ac.uk" <gorry@erg.abdn.ac.uk>, "Bless, Roland (TM)" <roland.bless@kit.edu>, "tsvwg@ietf.org" <tsvwg@ietf.org>
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From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
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Date: Wed, 9 May 2018 08:46:17 +1200
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Subject: Re: [tsvwg] Doubts regarding motivation of draft-ietf-tsvwg-iana-dscp-registry-04
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On 09/05/2018 02:55, Alexander Vainshtein wrote:
> David,
> Lots of thanks for a very detailed explanation.
> 
> Coming back to my original doubt, , changing the IANA allocation policy on Pool 3 (16 values) in order to make just one value standard still looks an exaggeration to me. 
> What are we going to do with the remaining 15 values? 

To be honest, probably nothing. Having as many as 6 bits to select a per-hop
behaviour has always seemed like a lot (and led to rather complex solutions
such as 4 distinct AF classes each with 3 drop precedences).

However, if somebody ever came along with a need for a very large number
of local-use PHBs, there's nothing to stop them using Pool 3, since
all DSCP values are RECOMMENDED anyway, except for CS0-7. 
(Paragraph 3 at https://tools.ietf.org/html/rfc2474#page-8 )

This is the irony of having misused CS1 for LE - it's one of the few code
points that is truly mandated by RFC2474.

    Brian