QoS Output Drops

[John Blakley]

All,

Is it possible to create your own bottleneck? Here's the problem:

I have an ethernet handoff from our provider. It's a 100Mb link with a 50Mb CIR. I have the bandwidth statement on the interface for 50000 and a service policy that shapes class-default for 50Mb. We have TONS of output drops, but the circuit hasn't been above 35Mb. I'm wondering if going from 100Mb (inside) to a bandwidth of 50Mb (specified on 'outside' interface) is causing the router to see it as congestion. Even if, why would I be seeing tail drops if I never reach above 35Mb?

policy-map COS

class HIGH

    priority 6000

  set ip dscp ef

class MEDIUM

    bandwidth remaining percent 60

  set ip dscp af31

  service-policy MARK-BGP

class LOW

    bandwidth remaining percent 30

  set ip dscp af21

class class-default

    bandwidth remaining percent 10

  set ip dscp default

     random-detect

    shape average 50000000

  service-policy AVPN

!

interface FastEthernet0/0/0

bandwidth 50000

no ip address

duplex full

speed 100

service-policy output COS

QoS Set

        dscp default

          Packets marked 220722492

        Exp-weight-constant: 9 (1/512)

        Mean queue depth: 18 packets

        class     Transmitted       Random drop      Tail drop          Minimum        Maximum     Mark

                  pkts/bytes     pkts/bytes       pkts/bytes          thresh         thresh     prob

        0       220089486/172146352525 554475/476267172  90761/75634968          20            40  1/10

Thanks,

John

[Joseph W. Doherty · Accepted solution]

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Posting

Your posted stats shows "Mean queue depth: 18 packets".

How are you "seeing" never more than 35 Mbps?  Reason I ask, shapers, policers, WRED work at a much, much, much finer granularity than something like even 30 interface stats.

There's a good change your WRED (default) thresholds are much too restrictive for 50 Mbps on a MAN/WAN.  Suggest you remove WRED altogether.

[John Blakley]

Our bandwidth monitoring server is only showing about 17Mb at the moment. I'm going to remove WRED and see if that helps.

Thanks!