Re: [RPRWG] RPR Perf: Single vs. Dual ring?]
Samian,
> So, to clarify my understanding, we are using
> dual rings for flow control packets that propagate hop-by-hop upstream.
Yes.
I believe there already is a (close to) consensus on dual rings.
Remember that dual rings are also needed for protection.
The flow control packets are, as you say, in a sense broadcasted.
But on a ring a broadcast needs to go hop by hop.
And upstream is the sensible way to send the packets, because
the node that bugs you is most probably closest upstream.
> But, wouldn't it make the simulations easier if we could default to a more
> generic flow control scheme,
I believe we have to simulate and understand the flow control schemes
down to the very details. Small changes in flow control can make big
changes in performance. Flow control is feedback, and if we don't get
it right we can get oscillations etc., that are typical for a badly
controlled feedback system.
Stein
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Subject: Re: [RPRWG] RPR Perf: Single vs. Dual ring?
Date: Fri, 27 Apr 2001 16:43:50 -0700
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Hi Stein,
Thank you for the explanation. So, to clarify my understanding, we are using
dual rings for flow control packets that propagate hop-by-hop upstream.
But, wouldn't it make the simulations easier if we could default to a more
generic flow control scheme, like maybe broadcasting the control packets.
This will be a more robust mechanism than hop-by-hop and also eliminate the
necessity of the second ring. The performance characteristics of this scheme
will also give us an insight into the performance tradeoff of this approach
for comparison.
Do you think a scenario on these lines will be interesting?
Thanks,
Samian
- -----Original Message-----
From: Stein Gjessing [mailto:steing@xxxxxxxxxx]
Sent: Tuesday, April 24, 2001 11:41 PM
To: stds-802-17@xxxxxxxx
Subject: [RPRWG] RPR Perf: Single vs. Dual ring?
Samian,
I agree that a single ring will demonstrate the performance characteristics
of interest if we disregard flow control.
Analyzing performance with flow control (by sending flow control
packets upstream), the dual rings are of course necessary.
Then the interference between flow control packets and data packets
also become an interesting issue.
(Also remember that packets are going at most half way around on one ring)
Stein Gjessing
University of Oslo
>Hi Khaled,
>
>I know that the performance adhoc committee decided that the Phase I
>simulations should be done using dual rings. I am beginning to question if
>that is necessary. I think a single ring will demonstrate the performance
>characteristics of interest and save us a lot of run time in running the
>simulations and is much easier to analyze.
>
>Am I missing something?
>
>Samian Kaur
>Lantern Communications