CBWFQ over ATM: Questions on Show policy interface output

From: Brennan_Murphy@NAI.com
Date: Thu Mar 18 2004 - 12:49:39 GMT-3

I need help understanding the output from a show policy interface atm
command below. This is coming from a 7500 series router running
12.2.16a. Trying to understand under what circumstances packet drops
occur in the classes. Are packets dropped when the banwidth percent for
a class is exceeded or when the total banwidth available on the ATM VC
is exceeded. The output on this command seems to suggest that when the
bw percent chosen for the class is exceeded, packets are dropped.

pladcrt1#sh pol int atm10/0/0.12
 ATM10/0/0.12: VC 2/212 -

  Service-policy output: CBWFQQ

    queue stats for all priority classes:
      queue size 0, queue limit 57
      packets output 0, packet drops 0
      tail/random drops 0, no buffer drops 0, other drops 0

    Class-map: CONTROL (match-all)
      13482 packets, 986994 bytes
      5 minute offered rate 5000 bps, drop rate 0 bps
      Match: ip dscp cs6
      queue size 0, queue limit 1
      packets output 13482, packet drops 0
      tail/random drops 0, no buffer drops 0, other drops 0
      Bandwidth: 5.0%, kbps 38

    Class-map: VOICE (match-all)
      0 packets, 0 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: ip dscp ef
      Priority: 30% (230 kbps), burst bytes 5750, b/w exceed drops: 0

    Class-map: VIDEO (match-all)
      0 packets, 0 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: ip dscp cs4
      queue size 0, queue limit 1
      packets output 0, packet drops 0
      tail/random drops 0, no buffer drops 0, other drops 0
      Bandwidth: 1.0%, kbps 7

    Class-map: PLATINUM (match-all)
      651 packets, 444300 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: ip dscp cs3
      queue size 0, queue limit 1
      packets output 600, packet drops 51
      tail/random drops 51, no buffer drops 0, other drops 0
      Bandwidth: 1.0%, kbps 7

    Class-map: GOLD (match-all)
      0 packets, 0 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: ip dscp cs2
      queue size 0, queue limit 47
      packets output 0, packet drops 0
      tail/random drops 0, no buffer drops 0, other drops 0
      Bandwidth: 25.0%, kbps 192

    Class-map: SILVER (match-all)
      1116 packets, 118934 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: ip dscp cs1
      queue size 0, queue limit 1
      packets output 1096, packet drops 20
      tail/random drops 20, no buffer drops 0, other drops 0
      Bandwidth: 5.0%, kbps 38

    Class-map: BRONZE (match-all)
      466036 packets, 165312557 bytes
      5 minute offered rate 170000 bps, drop rate 0 bps
      Match: ip dscp default
      queue size 0, queue limit 1
      packets output 459726, packet drops 6315
      tail/random drops 6315, no buffer drops 0, other drops 0
      Bandwidth: 1.0%, kbps 7

    Class-map: DEFAULT (match-all)
      0 packets, 0 bytes
      5 minute offered rate 0 bps
      Match: ip dscp default

    Class-map: class-default (match-any)
      1729 packets, 792398 bytes
      5 minute offered rate 0 bps, drop rate 0 bps
      Match: any
      queue size 0, queue limit 7
      packets output 1700, packet drops 29
      tail/random drops 29, no buffer drops 0, other drops 0

Thanks,
BM

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