Re: [8023-CMSG] To Pause or not to Pause, That is the Question
Tom,
Flow- or class-based flow control could still use the 802.3x PAUSE
frames. The difference is that unlike the existing 802.3x which halts
all flows/classes/traffic types a flow/class/traffic based flow control
would only halt the data that corresponds to that flow/class/traffic
type.
I also believe that the terminology we want to use is queues. The MAC
responds to multiple queues: one for data, one for slow protocol frames
and one for pause frames. Maybe this is could be done by adding a few
new queues, maybe it requires some enhancements to flow control. I'm
sure there are many ideas of how to make improvements to the way
Ethernet handles multiple forms of traffic.
Thanks,
Brad
-----Original Message-----
From: owner-stds-802-3-cm@listserv.ieee.org
[mailto:owner-stds-802-3-cm@listserv.ieee.org] On Behalf Of Thomas
Dineen
Sent: Friday, April 23, 2004 1:36 PM
To: STDS-802-3-CM@listserv.ieee.org
Subject: Re: [8023-CMSG] To Pause or not to Pause, That is the Question
All:
Ben's statements below bring up some interesting points
many of which I agree with! However to me there is a bit
of a snicker here in that I have grave doubts that a 802.3
Task Force and the 802.3 Working Group would ever seriously
consider anything that was not a frame based pause type protocol,
thus rendering the entire effort a waist of time. This is why I voted
against the study group.
Thomas Dineen
Benjamin Brown wrote:
> All,
>
> This note is in response to a private thread that began before the
> reflector was in place. I've moved it here without reproducing all
> the previous material. Those who generated that material are
> encouraged to raise their arguments again or to simply continue
> this thread.
>
> So, most agree that PAUSE doesn't work except in very special
> cases or for some handpicked tests and, even then, it can have a big
> impact on throughput. It sounds like PAUSE exacerbates the problem
> of congestion, spreading it backwards through the network.
>
> Why do we think that flow- or class-based PAUSE will work? What
> problem does this fix that link-based PAUSE can't? Don't answer too
> quickly.
>
> Each flow/class on a particular link is likely to have multiple
sources
> so by PAUSEing one of them, doesn't that have the same effect that
> link-based PAUSE has, though perhaps only for one flow/class?
>
> A flow can be defined many different ways and, based on your
> definition, there can be many, many flows over a single link. When
> we use PAUSE, either link-based or flow/class-based, we're acting
> on a buffer. We can't act on each flow individually. That's not
practical
> for a real implementation because it is not practical for a device to
> have
> a buffer for each flow. Therefore, numerous flows are combined into
> a "class" (and I use this term generically) and each class is assigned
> a buffer. All we can do is flow-control that buffer.
>
> So, now I'll ask the question again. What does flow/class-based PAUSE
> have over link-based PAUSE? An answer to this is critical is we're to
> stand up in WG 802.3 on Thursday, July 15 and ask to become a Task
> Force.
>
> Regards,
> Ben
>
> --
> -----------------------------------------
> Benjamin Brown
> 178 Bear Hill Road
> Chichester, NH 03258
> 603-491-0296 - Cell
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