Subject: Re: [Ieprep] re-charter

From: Janet P Gunn <[email-masked]>
Date: Fri, 15 Jul 2005 16:25:17 -0400

[email-masked] wrote on 07/14/2005 03:48:57 PM:

>
> On Jul 13, 2005, at 5:19 PM, Richard F Kaczmarek wrote:
>
> > <snip>
>
> > With the Cisco routers we were using,
> > we could allocate bandwidth in the EF queue for emergency
> > communications
> > and for normal traffic. In this latter case, some sort of marker
> > (e.g.,
> > DSCP) may be needed for emergency traffic, but a unique per hop
> > behavior
> > may not be needed.
>
> for this last sentence, if what you are advocating is defining
> another DSCP value but with no distinctive corresponding per hop
> behavior, then I think that is a non-starter.
>

>From RFC 3246
"   Finally, it is possible to implement hierarchical scheduling
   algorithms, such that some non-FIFO scheduling algorithm is run on
   sub-flows within the EF aggregate, while the EF aggregate as a whole
   could be served at high priority or with a large weight by the top-
   level scheduler.  Such an algorithm might perform per-input
   scheduling or per-microflow scheduling within the EF aggregate, for
   example. "

This is one way of describing the functionality above.

Also from RFC 3246
"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."

And at the San Diego meeting, one of the authors of RFC 3246 (sorry, I
forget who) explicitly said in his presentation that there was never any
intention to restrict EF to a single DSCP.

There do, of course, remain issues as to whether it is a good idea or not.
But it is permissible under RFC 3246.

Janet

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From: ken carlberg <[email-masked]>
Date: Fri, 15 Jul 2005 17:08:01 -0400

ok, then you are advocating a particular realization of EF as  
stipulated in rfc3246, as opposed to a new DSCP.  thanks for the  
clarification.

-ken