My question is similar to: What is benefit of using CBWFQ with fair-queue statement
Given this policy-map (without class-maps) configuration:
policy-map test class DSCP30 bandwidth percent 20 class DSCP40 bandwidth percent 30 class DSCP50 bandwidth percent 40 class class-default fair-queue
This reserves 20% of interface bandwidth for traffic marked as DSCP30. But this queue is still handled as FIFO. I hope following 2 statements are right:
- If two clients send DSCP30 traffic and one of them is a heavy hitter, the second client will experience drops and delays in times of congestion because the queue is being FIFOed.
- If two clients send DSCP0 traffic and one of them is a heavy hitter, the second client will experience less drops and delays in times of congestion because the queue is being fair-queued.
So the benefit of fair-queuing, that traffic is put into flows and treated equally (fair), does only apply to the class-default traffic. So why do I never see a configuration like this in tutorials or examples:
policy-map test class DSCP30 bandwidth percent 20 fair-queue class DSCP40 bandwidth percent 30 fair-queue class DSCP50 bandwidth percent 40 fair-queue class class-default fair-queue
It basically activates fair-queuing for every class. Is there a reason not to use a configuration like this?
Some background: We have mainly Citrix traffic which uses very little bandwidth by default. But from time to time, some user uploads images from a camera and generates a lot of traffic. We dont have any possibility to differentiate this traffic from the rest, because it is handled in the same channel. So we would like to minimize the impact of "image peaks" for other Citrix users.
I have read somewhere that this is called "using a FQ pre-sorter" but am not sure if this is true. Thank you for having a look into this question.