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Siamack,
Some
of what you mentioned in the slides are quite inaccurate, may be implementation
specific.
The
fact is, CA applies to all priorities of traffic. However, one can choose to
implement their transit path,
line
card differently. For example, we decide to one implement for our line card
so that we can
achieve sub-millisecond jiiter for circuit emulation
traffic.
Please revisit my simulation presentations again,
you might have missed some detail. The last
thing
we want to do for the working group is getting bogged down on a non-quantitative
performance speculation.
Adisak
Harmen,
Please see my comments below. Thanks for the interest.
Regards, Siamack
Harmen van As wrote:
Dear SiamackIt would
be necessary to back off your statements on the merits andperformance of
Open Loop with simulations.
> My statements are based on the
protocol flow charts & simulation of congestion avoidance algorithms
conducted so far. Please see slide #5 for the list of
references.
The goal of MAC protocolsis also to
achieve fairness among iinterfering nodes, not merely
congestioncontrol.
> It would be helpful to have a concise
description of this goal, what is fairness in this context, and what
interference you have in mind. I have shown that CA algorithms covered
can introduce HOL blocking which is a form of interference. Open loop
congestion controls do not do this.
The first
two statements on CA mechanisms is certainly not true at all.
> Again the references in slide #5,
& existing simulations show that the weighted fairness algorithms are
only targetting the low priority class i.e. C' portion of the ring bandwidth
(C'= C-a
). This is what I call static
partitioning.
>The delay bound that I have in mind is
due to the high priority traffic class only. i.e. the ring access delay of
the high priority traffic is only due to high priority traffic on the ring.
In some CA schemes and under certain conditions described in the slides, the
low priority traffic is interfering with this bound. i.e. low priority ring
traffic is scheduled ahead of high priority acess.
>Of course if one is patient enough
even best effort traffic would eventullay make it through. So we have
to be careful that we are on the same page with respect to delay
bounds.
We will show
that by two protocols having different degrees of sophistication.Seems to
become an interesting and lively September meeting in San
Jose.
> Looking forward to
it.
Best
regardsHarmen------------------------------------------------------------------
Prof.Dr. Harmen R. van
As Institute of Communication
Networks
Head of
Institute
Vienna University of Technology
Tel
+43-1-58801-38800
Favoritenstrasse 9/388
Fax
+43-1-58801-38898
A-1040 Vienna, Austria
http://www.ikn.tuwien.ac.at
email: Harmen.R.van-As@xxxxxxxxxxxx
------------------------------------------------------------------ORIGINAL
MESSAGETo: stds-802-17@xxxxxxxx
Subject: [RPRWG]
Merits of Open Loop
From: Siamack Ayandeh <sayandeh@xxxxxxxxxx>
Date: Mon, 06
Aug 2001 11:01:39 -0400
CC: sayandeh@xxxxxxxxxx
Sender: owner-stds-802-17@xxxxxxxxxxxxxxxxxx
Folks, As some people are busy doing simulations and
writing proposals for the
San Jose meeting, I am posting this presentation early on
the
reflector. It
describes the merits of open loop congestion controls and
may impact some of the simulation
scenarios that would be presented.
The main conclusions of the document are that: - Congestion avoidance algorithms may lead to
static partitioning of the
ring bandwidth between high and low priority traffic
- With CA it may not be possible to bound
the ring access delay of high
priority traffic
-
Open loop does not suffer from HOL blocking
- Open loop has relatively low configuration and
operational complexity
-
Open loop is not prone to tuning issues, or link aggregation,
etc... Regards,
Siamack
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