Available Bandwidth

Discussion in 'Cisco' started by Igor Mamuziæ, Jan 7, 2005.

  1. What does exactly represents "Available bandwidth" field in the 'show
    interfaces serial' command output?

    I ask this because I have frame relay link with contracted CIR of 2000 kbps
    and field mentioned above displays 1150 kbps... I can't find any explanation
    of this field in the "Command Lookup Tool" at cisco.com...

    Best Regards,
    Igor
     
    Igor Mamuziæ, Jan 7, 2005
    #1
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  2. Igor Mamuziæ

    John Agosta Guest

    Gof4 LMI includes a field in the Full Status message that indicated the
    available bandwidth on a PVC from the switch's perspective.
    This is what you're looking at on your 'show' command.
     
    John Agosta, Jan 8, 2005
    #2
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  3. Hi, John...

    Is this means that my carrier does not provide me a CIR contracted bandwidth
    (that is MinCIR) which is 2 Mbps? show int serial shows only 1150 Kbps...

    Regards,
    Igor
     
    Igor Mamuziæ, Jan 10, 2005
    #3
  4. No it doesn't. "Available bandwidt" in show interface bears next to no
    relationship to the real physical paramaters of your circuit.

    Some QoS features in IOS are allowed to "reserve" bandwidth for their
    own nefarious purposes.

    By default the maximum "reserved" bandwidth is 75% of the interface
    bandwidth as set by thr bandwidth command. This is another number that bears
    next to no relationship to the real physical paramaters of your circuit,
    and yours appears to be 1536 at the moment,

    If you configure "bandwidth 2000" in your interface, you will find the
    available bandwidth changes to 1500. It still bears next to no
    relationship to the real physical paramaters of your circuit.
     
    Martin Gallagher, Jan 11, 2005
    #4
  5. Igor Mamuziæ

    Ivan Ostreš Guest

    Do you have a WFQ enabled on interface?
     
    Ivan Ostreš, Jan 11, 2005
    #5
  6. Hi, Ivan,

    Yes...There is WFQ activated on interface by default.

    B.R.
    Igor
     
    Igor Mamuziæ, Jan 11, 2005
    #6
  7. Igor Mamuziæ

    Ivan Ostreš Guest

    If there's no fair-queue configured on the interface, you don't even see
    that line from "show int s 0" (try to enable fifo on interface). It just
    shows maximal reserved bandwidth on the interface and it does change
    using "bandwidth" interface command (and max-reserved-bandwidth), not
    the actual bandwidth on the line.

    To answer original question: no, it does not mean that provider is not
    "giving" you the full CIR.


    The value you're seeing is a part of WFQ operation as you can see from
    the example:

    r2#sh int s0 | incl Ava
    Available Bandwidth 1158 kilobits/sec
    r2#conf t
    Enter configuration commands, one per line. End with CNTL/Z.
    r2(config)#int s0
    r2(config-if)#bandwidth 2048
    r2(config-if)#end
    r2#conf t
    *Mar 7 05:29:18.982: %SYS-5-CONFIG_I: Configured from console by csh

    r2#sh int s0 | incl Ava
    Available Bandwidth 1536 kilobits/sec
    r2#
    r2#conf t
    Enter configuration commands, one per line. End with CNTL/Z.
    r2(config)#int s0
    r2(config-if)#max-reserved-bandwidth 100
    r2(config-if)#end
    r2#
    r2#conf t
    *Mar 7 05:29:40.802: %SYS-5-CONFIG_I: Configured from console by csh

    r2#sh int s0 | incl Ava
    Available Bandwidth 2048 kilobits/sec
    r2#
     
    Ivan Ostreš, Jan 11, 2005
    #7
  8. Ivan,

    Thanks for informations... I will leave WFQ on that interface since this is
    one of the links to my ISP, so outgoing queue scheduling is not an issue at
    the moment.
    If congestion occures, it will be (unfortunatelly) in inbound direction:)

    B.R.
    Igor

    Thank you for your support...
     
    Igor Mamuziæ, Jan 12, 2005
    #8
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