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RE: [RPRWG] Question about B eir and C priority(My last mail have wrong text arrange)


Jiangzhou,

Firstly, note that the flow chart is a simplification to give an overview of the process. The details are in the state machine. Please read the state machine to gain more than a cursory understanding of the protocol.

Secondly, note that the stage queue state table was modified for Draft 2.2 to correct a bug that could have allowed classC frames to sometimes gain priority over classB EIR frames.

Finally, classB (CIR or EIR) always has priority over classC, when they are allowed to transmit. If classB CIR is limited by its allocated rate, then sendB will be false. If sendC is true, then any classB frames that are available can be sent as classB EIR (in other words, classB with fe (fairness eligible) set to true), with higher priority than classC.

jl

-----Original Message-----
From: Jiang zhou [mailto:zjiang@xxxxxxxxxxxxxxxxxxx]
Sent: Friday, May 16, 2003 3:24 AM
To: RPRWG (E-mail)
Cc: Jiang Zhou
Subject: [RPRWG] Question about B eir and C priority(My last mail have wrong text arrange)



Hi,all:

I have find something wrong in stage queue flow chart.
The follow is from the Draft 2.1 stage queue flow chart

    (START)
        |
    (CLASSA)
classA entry && sendA ----yes--> select classA frame--->space in stage queue
        |                                            &&PHY is ready-->start
        |
        |
    (CLASSB)
classB entry && sendB ----yes-->select classB frame---->space in stage queue
        |                                            &&PHY is ready-->start
        |
        |
    (CLASSC)
classC entry && sendC ----yes-->select classC frame---->space in stage queue
        |                                            &&PHY is ready-->start
        |
        |
    no frame selected
        |
    (START)

If the current status:

Both B frame and C frame are in client queue

sendB is false and sendC is 255.

So it will chose C frame to trasmit not the B frame.

Therefore, it violates priority. Because B traffic has high priority than C
traffic.




From my understand, I think that B traffic in CIR profile has high prioriy
than C traffic and both B traffic exceed CIR and C has the same priority,
they share the spare link capcity.



Can some one give a explain about the prioriy of B EIR traffic and C
traffic?




Best Regards
Jiangzhou
zjiang@xxxxxxxxxxxxxxxxxxx