Understanding show policy-map interface XX command

[Steph1963]

Hi,

Is there anybody who would have a definition for the (queue depth/total drops/no-buffer drops) 0/0/0 statistics when we used the show polilcy-map interface XX

I would like to know if the queue depth is the physical size of the queue and what is the difference between total drops and no-buffer drops.

Also would like to know if we can change the queue limit size?

Finally, I would also like to know if the number of packet in the class class-default includes packets that match other queues?

Thanks for your help

Stephane

R3#show policy-map interface Multilink1

Multilink1

  Service-policy output: SHAPE_384K

    Class-map: class-default (match-any)

      57 packets, 2254 bytes

      5 minute offered rate 0 bps, drop rate 0 bps

      Match: any

      Queueing

      queue limit 64 packets

      (queue depth/total drops/no-buffer drops) 0/0/0

      (pkts output/bytes output) 57/4874

      shape (average) cir 384000, bc 1536, be 1536

      target shape rate 384000

      Service-policy : CBWFQ

        queue stats for all priority classes:

          Queueing

          queue limit 64 packets

          (queue depth/total drops/no-buffer drops) 0/0/0

          (pkts output/bytes output) 5/510

        Class-map: VOICE (match-all)

          5 packets, 520 bytes

          5 minute offered rate 0 bps, drop rate 0 bps

          Match: ip dscp ef (46)

          Priority: 48 kbps, burst bytes 1500, b/w exceed drops: 0

        Class-map: SIGNALING (match-all)

          0 packets, 0 bytes

          5 minute offered rate 0 bps, drop rate 0 bps

          Match: ip dscp cs3 (24)

          Queueing

          queue limit 64 packets

          (queue depth/total drops/no-buffer drops) 0/0/0

          (pkts output/bytes output) 0/0

          bandwidth 8 kbps

        Class-map: class-default (match-any)

          52 packets, 1734 bytes

          5 minute offered rate 0 bps, drop rate 0 bps

          Match: any

          Queueing

          queue limit 64 packets

          (queue depth/total drops/no-buffer drops/flowdrops) 0/0/0/0

          (pkts output/bytes output) 52/4364

          Fair-queue: per-flow queue limit 16

[Peter Paluch · Accepted solution]

Hi Steph,

In my understanding, the queue depth in this output relates to the amount of currently stored packets in the appropriate software queue. The no-buffer drops should relate to drops caused by overfilling this queue, i.e. after reaching the queue limit. The total drops should also take into account drops caused by policing and WRED (if configured).

The queue limit size can indeed be changed in the appropriate class section of a policy-map using the queue-limit command. The behavior has slightly changed between pre-HQF and HQF IOS images, see the following document for more information:

http://www.cisco.com/en/US/products/hw/routers/ps341/products_tech_note09186a0080af893d.shtml

Per my understanding, the number of packets in the class-default should not match or include numbers of packets in another classes, simply because a traffic handled by a different class is not concurrently handled by class-default.

To Joseph Doherty: Please feel more than welcome to join and add/correct me here, as you are the resident QoS expert here! I am still learning tremendously lot from you!

Best regards,

Peter

[Joseph W. Doherty]

Disclaimer

The   Author of this posting offers the information contained within this   posting without consideration and with the reader's understanding that   there's no implied or expressed suitability or fitness for any purpose.   Information provided is for informational purposes only and should not   be construed as rendering professional advice of any kind. Usage of  this  posting's information is solely at reader's own risk.

Liability Disclaimer

In   no event shall Author be liable for any damages whatsoever (including,   without limitation, damages for loss of use, data or profit) arising  out  of the use or inability to use the posting's information even if  Author  has been advised of the possibility of such damage.

Posting

Peter thanks for the compliment (and I learn much, or more, from your posts too).

"I would like to know if the queue depth is the physical size of the  queue and what is the difference between total drops and no-buffer  drops."

My understanding is queue depth is a current number of packets in the queue (at the time the command ran).  No-buffer drops, I believe, are when there's no available buffer to queue the packet, i.e. physical resource exhaustions.  (My understanding differs from what Peter noted.)  My experience, you seldom see hits on this counter unless you set your logical queue limits very high, and hit them.  Buffer resources also vary per platform.  Total drops, I also believe with Peter, counts drops for any reason.

"Also would like to know if we can change the queue limit size?"

Usually, but also platform/IOS dependent.  Peter describes the normal class queue setting command.

"Finally, I would also like to know if the number of packet in the class class-default includes packets that match other queues?"

No, as Peter also describes.

[Steph1963]

Hi,

Thanks to both of you for these valuable answers.

Thanks
Stephane