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
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>