LLQ priority traffic question

namegoesherenamegoeshere Registered Users Posts: 2 ■□□□□□□□□□
Cisco - https://www.cisco.com/en/US/docs/ios/12_0t/12_0t7/feature/guide/pqcbwfq.html) - says:

Priority traffic metering has the following qualities:

•It is much like Committed Access Rate's (CAR) rate limiting, except that priority traffic metering is only performed under congestion conditions. When the device is not congested, the priority class traffic is allowed to exceed its allocated bandwidth. When the device is congested, the priority class traffic above the allocated bandwidth is discarded.

•It restrains priority traffic to its allocated bandwidth to ensure that nonpriority traffic, such as routing packets and other data, is not starved.

Does this mean LLQ gives a specific bandwidth to voice traffic that can't change? Or does it mean voice traffic can burst like data traffic? Am I caring too much?


  • Chris.MChris.M Member Posts: 6 ■□□□□□□□□□
    When a LLQ is created by default the policer creates an allowable burst of 200ms (20%) of your configured bandwidth.

    For example if you have "priority 100" then you have 100 Kbps with a 20,000 bit or 2500 Byte burst. Basically you have a dual token bucket for the conforming traffic and one for exceeding traffic. Anything that violated will be dropped.

    You can see the automatic burst allocated by "show policy-map interface xxxx"

    You can manually adjust the amount of burst and I believe it is in bytes but don't quote me on that. IE: "priority 100 1500" would give you a 100 Kbps bandwidth and 1500 Byte burst.
    "[FONT=georgia, bookman old style, palatino linotype, book antiqua, palatino, trebuchet ms, helvetica, garamond, sans-serif, arial, verdana, avante garde, century gothic, comic sans ms, times, times new roman, serif]Impossible is a word only to be found in the dictionary of fools. ~Napoleon"[/FONT]

    Completed: CCIE:Voice Written - Passed 4/14/11.
    In Progress: CCIE:Voice Lab - ETA 12/2011.
  • laidbackfreaklaidbackfreak Member Posts: 991

    Voice would use a strict priority with a fixed bandwidth. The last thing you want is voice bursting, as it will be at the mercy of being dropped leading to choppy(at best) voice.
    if I say something that can be taken one of two ways and one of them offends, I usually mean the other one :-)
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