QOS drops

Unanswered Question
Jul 2nd, 2010
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Damn QOS.


We just experienced video stream problems on our network. I troubleshooted it down to a service policy applied to an interface:


Class-map: VOIP (match-any)
      921446302 packets, 122915135484 bytes
      5 minute offered rate 204000 bps, drop rate 0 bps
      Match:  dscp ef (46)
        921446264 packets, 122915130328 bytes
        5 minute rate 204000 bps
      Queueing
        Strict Priority
        Output Queue: Conversation 264
        Bandwidth 18 (%)
        Bandwidth 6120 (kbps) Burst 153000 (Bytes)
        (pkts matched/bytes matched) 110611415/14458935412
        (total drops/bytes drops) 1/204


    Class-map: Call_Signaling (match-any)
      146776112 packets, 8649777417 bytes
      5 minute offered rate 5000 bps, drop rate 0 bps
      Match:  dscp cs3 (24)
        146776111 packets, 8649777473 bytes
        5 minute rate 5000 bps
      Queueing
        Output Queue: Conversation 265
        Bandwidth 7 (%)
        Bandwidth 2380 (kbps)Max Threshold 64 (packets)
        (pkts matched/bytes matched) 8057314/501078417
        (depth/total drops/no-buffer drops) 0/0/0


    Class-map: VIDEO (match-any)
      165406955 packets, 126452966708 bytes
      5 minute offered rate 179000 bps, drop rate 0 bps
      Match:  dscp af31 (26)
        165406944 packets, 126452960484 bytes
        5 minute rate 179000 bps
      Queueing
        Output Queue: Conversation 266
        Bandwidth 50 (%)
        Bandwidth 17000 (kbps)Max Threshold 64 (packets)
        (pkts matched/bytes matched) 12725536/10218784437
        (depth/total drops/no-buffer drops) 0/12390/0


    Class-map: class-default (match-any)
      24045021592 packets, 15208929650829 bytes
      5 minute offered rate 7744000 bps, drop rate 0 bps
      Match: any
      Queueing
        Flow Based Fair Queueing
        Maximum Number of Hashed Queues 256
        (total queued/total drops/no-buffer drops) 0/660666/246
         exponential weight: 9


-> Video is assigned 50% bandwidth, or 17 Mbps

-> The load was only 2-4 Mbps and the class was dropping, it showed "drop rate 2000 4000 sometimes 6000 bps) (see below)

-> As you can see there are 12390 total drops (??) but they are NOT no-buffer drops. What are they then ??


5 minute offered rate 2836000 bps, drop rate 6000 bps

Match:  dscp af31 (26)
     165055018 packets, 126095913385 bytes
     5 minute rate 1425000 bps
      Queueing
      Output Queue: Conversation 266
      Bandwidth 50 (%)
      Bandwidth 17000 (kbps)Max Threshold 64 (packets)
     (pkts matched/bytes matched) 12578045/10050218983
     (depth/total drops/no-buffer drops) 0/11032/0



5 minute offered rate 2788000 bps, drop rate 2000 bps

Match:  dscp af31 (26)
    165250961 packets, 126295297289 bytes
    5 minute rate 2725000 bps
    Queueing
     Output Queue: Conversation 266
      Bandwidth 50 (%)
   Bandwidth 17000 (kbps)Max Threshold 64 (packets)
     (pkts matched/bytes matched) 12663864/10148288144
     (depth/total drops/no-buffer drops) 0/11750/0


-> Also interface shown output drops:


Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 673673


Any idea why the router would drop in VIDEO before dropping in default ? Total utilisation was only 13-14 Mbps/45 Mbps.




regards,

Geert

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