> Doug Hanks [mailto:[email protected]]
> Sent: Wednesday, April 20, 2016 11:41 PM
>
> MX isn’t a VoQ system. It actually buffers on both ingress and egress
> chipsets. The QFX10K is a VoQ system and buffers on ingress chip. QFX10K
> has 384K VoQs per PFE. In the case of the QFX10002-72Q that would be a
> system total of 2.3M.
>
Well if the only difference between VOQ system and non VOQ system would be
buffering on ingress vs buffering on both ingress and egress we wouldn't get
far would we.
My understanding is that:
The "VOQ" on ingress module represents BW* capacity of an egress entity**.
And for the above to hold true the system has to run arbitration - and that in
turn results in implicit*** back-pressure.
*in correct implementations it should actually represent processing capacity
per egress entity which then results in BW capacity as at the end of the day we
still need to transport the whole packet body across the system.
**the egress entity could be: a queue, a BW entity (e.g. a 10Gbps entity on a
100GE int with a 10GE breakout cable), a port, a PFE/NPU, a LC.
***implicit back-pressure means the back-pressure is realized as a result of
granting access only for what can be processed(and transmitted) per the egress
entity.
adam
Adam Vitkovsky
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