Subject: [Ieprep] Multiple instances of EF

From: "Gunn, Janet" <[email-masked]>
Date: Wed, 16 Jul 2003 09:48:03 -0400

Since this came up twice in today's IEPREP meeting, here is the text from
3246 (last paragraph of actual text before the author addresses).

   "It should be noted that it is quite acceptable for a Diffserv domain
   to provide multiple instances of EF.  Each instance should be
   characterizable by the equations in Section 2.2 of this
   specification.  The effect of having multiple instances of EF on the
   E_a and E_p values of each instance will depend considerably on how
   the multiple instances are implemented.  For example, in a multi-
   level priority scheduler, an instance of EF that is not at the
   highest priority may experience relatively long periods when it
   receives no service while higher priority instances of EF are served.
   This would result in relatively large values of E_a and E_p.  By
   contrast, in a WFQ-like scheduler, each instance of EF would be
   represented by a queue served at some configured rate and the values
   of E_a and E_p could be similar to those for a single EF instance."

It clearly refers to multiple instances with different priority ("an
instance of EF that is not at the highest priority", and to multiple queues
("each instance of EF would be represented by a queue").  What it doesn't
address is the use of additional code points to distinguish the additional
instances.

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From: RJ Atkinson <[email-masked]>
Date: Wed, 16 Jul 2003 11:44:55 -0400

On Wednesday, Jul 16, 2003, at 09:48 America/Montreal, Gunn, Janet 
> address is the use of additional code points to distinguish the 

I believe that most shipping DiffServ implementations already
can support multiple EF or multiple AF (or any mixture)
concurrently.  The number of queues supported does often
vary, with DoD precedence needing 8 queues and much
currently shipping equipment only supporting 2 or 4 queues.
So operators should test before they decide what to deploy
(as always).

Note Well:
	The question of which codepoints have which meanings
is quite literally a deployment detail.  Each deployment
will very probably be different.  This is not a problem
since inter-domain DiffServ is virtually non-existent today
(and will remain non-existent for the foreseeable future
for reasons discussed at length here in the past).

Ran Atkinson
[email-masked]