Re: [8023-CMSG] Fw: [802.1] Slides for per-priority flow control
Gadi,
I don't understand the logic of making PAUSE per VLAN. VLANs were
defined to restrict the broadcast domains so that devices that don't
usually communicate with each other appear to be on different networks
(hence Virtual LAN). There is no "flow" information implied in a VLAN
tag - it should be expected that a VLAN could be just as meshed as any
other LAN. A per-VLAN PAUSE would suffer from exactly the same problems
that the current PAUSE suffers within the confines of the virtual LAN.
If your goal is to push the PAUSE back to the source of the traffic then
(in layer 2 terms) per source MAC address would be more logical. To
fully support this mechanism a network switch would have to support 2^48
queues per port - although practical implementations seem to be at
16,000 or more MAC addresses therefore 800,000 queues would be
sufficient for a 50 port network switch.
Such requirements would surely raise the complexity and cost of network
switch devices significantly. More expensive switches would only benefit
a very small section of society :-)
In short, any change to backpressure that does not include a "per-flow"
mechanism is essentially the same as we have. Any attempt at "per-flow"
backpressure will suffer from scaleability problems (and will work very
poorly on highly meshed systems).
Hugh.
Gadi Lahat wrote:
>Muneyoshi,
>Is your suggestion looks at making the priority field valid for the
>pause frame ?
>+ Has anyone raised the option of making the pause per VLAN ? (VLAN
>queuing )
>
>
>
>
>
>
>