When is a circuit "congested"?

Discussion in 'Cisco' started by Dave Ward, Apr 11, 2006.

  1. Dave Ward

    Dave Ward Guest

    We have had traffic shaping configured on our WAN using the "Bandwidth
    percent" command.

    I understand that the configuration will only become active when the
    circuit to which it applies becomes congested.

    But can anyone tell me what the definition of a congested circuit is?

    i.e If a circuit has more than 75% utilisation is it treated as
    congested?

    Cheers

    Dave.
     
    Dave Ward, Apr 11, 2006
    #1
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  2. Dave Ward wrote:

    Hello,

    > We have had traffic shaping configured on our WAN using the "Bandwidth
    > percent" command.
    >
    > I understand that the configuration will only become active when the
    > circuit to which it applies becomes congested.
    > But can anyone tell me what the definition of a congested circuit is?


    When the TX ring of the output interface is full. You can set the
    "tx-ring-limit" parameter to tune this. If you set it to a low value,
    the QoS mechanisms will become active sooner.

    > i.e If a circuit has more than 75% utilisation is it treated as
    > congested?
    >
    > Cheers
    >
    > Dave.
     
    Christophe Fillot, Apr 11, 2006
    #2
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  3. Dave Ward

    AM Guest

    Christophe Fillot wrote:
    > Dave Ward wrote:
    >
    > Hello,
    >
    >> We have had traffic shaping configured on our WAN using the "Bandwidth
    >> percent" command.
    >> I understand that the configuration will only become active when the
    >> circuit to which it applies becomes congested. But can anyone tell me
    >> what the definition of a congested circuit is?

    >
    >
    > When the TX ring of the output interface is full. You can set the
    > "tx-ring-limit" parameter to tune this. If you set it to a low value,
    > the QoS mechanisms will become active sooner.


    Doing so, what about the actual bandwidth available for that interface?
    That way you activate the mechanism sooner but will the total outgoing throughput be affected?
    If no the other kind of outgoing traffic, but that specifidied for QoS rules, will flow with more bandwidth; if yes that
    command can adjust the bandwith for the outgoing traffic.

    Is it true what I said? I only argued just to see if I understood correctly the topic.
    I'll appreciate your reply.

    TIA

    Alx.
     
    AM, Apr 11, 2006
    #3
  4. AM wrote:

    > Doing so, what about the actual bandwidth available for that interface?


    The bandwidth is still the same. The difference is in the scheduling of
    packets being transmitted on the output interface, given the QoS policy.
    When there is no congestion, packets are transmitted in a FIFO way.

    > That way you activate the mechanism sooner but will the total outgoing
    > throughput be affected?
    > If no the other kind of outgoing traffic, but that specifidied for QoS
    > rules, will flow with more bandwidth; if yes that command can adjust the
    > bandwith for the outgoing traffic.
    >
    > Is it true what I said? I only argued just to see if I understood
    > correctly the topic.
    > I'll appreciate your reply.
    >
    > TIA
    >
    > Alx.
     
    Christophe Fillot, Apr 11, 2006
    #4
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