QoS Advise

[DM812]

Hi,

Can anyone advice what the below refer to? I've tried researching online but can't find the specifics to some of the configs.

policy-map OUTPUT-POLICY

 class OUTPUT-QUEUE-L1
  priority level 1 percent 20

  set dscp ef

 class OUTPUT-QUEUE-L2
  priority level 2 percent 10

  set dscp af41

 class MGMT-QUEUE
  bandwidth remaining percent 5      (is this 5% of the remaining BW after priority queues 1/2 take 30%?)
  queue-limit dscp cs2 percent 80   (how do these %'s work and what dscp would you recommend?)
  queue-limit dscp cs3 percent 90
  queue-limit dscp cs6 percent 100
  queue-limit dscp cs7 percent 100
  queue-buffers ratio 10

Also which queue would non tagged traffic fall under?

Thanks.

[pieterh]

partial answer
- non-tagged traffic ends up in the class-default queue
- yes 5% after the other queues take their bit.
BUT: During congestion conditions, the traffic class is guaranteed bandwidth equal to the specified rate.
so this minimum is only in effect if no congestion occurs for this class,

from https://www.cisco.com/c/en/us/support/docs/quality-of-service-qos/qos-packet-marking/10100-priorityvsbw.html

Command Syntax Description
bandwidth {kbps} Specifies bandwidth allocation as a bit rate.
bandwidth percent {value} Specifies bandwidth allocation as a percentage of the underlying link rate.
bandwidth remaining percent {value} Specifies bandwidth allocation as a percentage of the bandwidth that has not been allocated to other classes.

[Joseph W. Doherty]

"- non-tagged traffic ends up in the class-default queue"

Actually, we don't know from the OP information posted.  Traffic not matched by a defined class would go to class-default.  As OP didn't list the class-maps, we don't know where non-tagged traffic goes.  Also, BTW, I assume by non-tagged OP means IP packets with a ToS setting of zero.  (I.e. IP packets always have a ToS tag.)

"- yes 5% after the other queues take their bit."

An expanded yes -  the 5% is based on bandwidth after LLQ, however, the 5% would only really be 5% if the other 95% of non-LLQ bandwidth is allocated (which it isn't, in OP), and in operation, the 5% minimum guarantee is only when all 100% of bandwidth has been configured and it's all being used at defined maximums.

What the bandwidth percentages really do, for non-LLQ traffic classes, it sets the dequeuing scheduling weight which is used relative to traffic classes.

"BUT: During congestion conditions, the traffic class is guaranteed bandwidth equal to the specified rate.
so this minimum is only in effect if no congestion occurs for this class, "

Actually, bandwidth guarantees are when there is congestion.  I.e. above may have been intended to read:
"BUT: During congestion conditions, the traffic class is guaranteed bandwidth equal to the specified rate.
so this minimum is only in effect if no congestion occurs for this class, "

Also, again, for the percentage to be provided, as the minimum, depends on overall policy configuration and actual traffic load against that policy.  I.e. there's more involved than whether this class, alone, is congested or not.

[pieterh]

Hello Joseph,
Yes that is what i inteded to say.
thanks for signaling and correcting my typo

[Joseph W. Doherty]

"queue-limit dscp cs2 percent 80 (how do these %'s work and what dscp would you recommend?)"

These are setting lessor threshold tail drops for some DSCP marked traffic. I.e. CS2 traffic will begin to be dropped when 80% of the queue-limit is reached.

As to recommending DSCP values, unable to really do so without knowing what you're trying to accomplish and what your traffic "looks" like.

BTW, it helps if you identify the platform and IOS for questions like these, as QoS features vary across them. Since you have PQ 1 and 2, this is an ASR platform?