Re: [8023-CMSG] Proposed Upper Layer Compatibility Objective
Hugh,
Thanks. Between you and Manoj, I'm starting to get a better understand
of your concerns. I don't completely agree with them, because as you've
alluded to, some of these issues are relative to implementation
strategies. I think that if priority PAUSE is added to 802.3, then it
will permit new implementation strategies that may be more efficient for
certain market segments; thereby, increasing the market potential for
Ethernet in general.
Cheers,
Brad
-----Original Message-----
From: Hugh Barrass [mailto:hbarrass@cisco.com]
Sent: Thursday, May 20, 2004 8:23 AM
To: Booth, Bradley
Cc: STDS-802-3-CM@LISTSERV.IEEE.ORG
Subject: Re: [8023-CMSG] Proposed Upper Layer Compatibility Objective
Brad,
I've answered below:
Booth, Bradley wrote:
>Hugh,
>
>I want to lock in on one paragraph you mentioned. It is listed below:
>
>"The only use of PAUSE that would (might) work would be if device 2
>could
>signal to device 1 that only frames destined for port K should be
>paused. This would require that device 1 must understand how device 2
is
>going to classify and direct the traffic and device 1 must maintain
>separate queues on its output port corresponding to the output ports of
>device 2. This means that device 1 will wind up with a total number of
>queues equal to the sum of all the queues on all of the devices
>connected to it. Scaling for more than 2 devices is left as an exercise
>for the reader."
>
>You said that this would require device 1 to understand how device 2
>classify and directs traffic. When you say that are you referring to
>the 802.3 portion of device 1? If you are, then I would agree that we
>have an issue of adding "intelligence" to the 802.3 MAC. If not, would
>not 802.1 know how to classify this traffic? Maybe this has to do with
>the definition of port, priority and queue. It might help if you could
>explain your use of the terminology to a layman.
>
>
>
If device 2 wants to send a message that says, "pause the traffic that
will be directed to my output queue K" then device 1 must understand the
criteria that device 2 will use to forward traffic to its output K. That
may be MAC address, that may be IP address, or something else entirely.
Note that the "output queues" of device 2 may be physical ports, virtual
ports or even s/w queues for an edge device.
Hugh.