Transmit Discards

Unanswered Question
Jan 12th, 2010
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I'm seeing a number of Transmit Discards showing withing Solarwinds Orion, which is our network monitoring tool.  Looking at the interface stats it is not using anywhere near the full bandwidth.


Investigation seems to show that thew drops are due to QoS configuration, is there and way of finding out what traffic might be causing this?


sh platform port-asic stats drop GigabitEthernet 1/0/24

  Interface Gi1/0/24 TxQueue Drop Statistics
    Queue 0
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0
    Queue 1
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0
    Queue 2
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0
    Queue 3
      Weight 0 Frames 1
      Weight 1 Frames 0
      Weight 2 Frames 514239
    Queue 4
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0
    Queue 5
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0
    Queue 6
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0
    Queue 7
      Weight 0 Frames 0
      Weight 1 Frames 0
      Weight 2 Frames 0

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Giuseppe Larosa Tue, 01/12/2010 - 12:23
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Hello Mark,

you need to find out what traffic is placed in queue 3


  Queue 3
      Weight 0 Frames 1
      Weight 1 Frames 0
      Weight 2 Frames 514239


you need to follow the QoS activity:


on input interfaces traffic is classified and an internal DSCP value is assigned based on several factors:

if the interface is trusted or not and depending on the type of interface (CoS is used for 802.1Q trunks, DSCP for IP packets on layer3 interfaces or access ports)

Once an internal DSCP value is assigned, based on internal DSCP to CoS mapping an outbound CoS is chosen

Cos value is then used to decide out which queue the packet is sent based on the queue set used on the interface.


Hope to help

Giuseppe

mark.j.hodge Thu, 01/21/2010 - 03:13
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It looks like this is a red herring as the counters haven't increased over the past week.  Is there a way oc learing this information without reloading the switch, a clear counters hasn't done it?

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