Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?


Managing Excess Bandwidth Distribution on Static Interfaces on MICs and MPCs

Service providers often used tiered services that must provide bandwidth for excess traffic as traffic patterns vary. By default, excess bandwidth between a configured guaranteed rate and shaping rate is shared equally among all queues, which might not be optimal for all subscribers to a service.

To manage excess bandwidth:

  1. Configure the parameters for the interface.
    1. Configure the shaping rate.

      On MIC and MPC interfaces, the guaranteed rate and the shaping rate share the value specified for the burst size. If the guaranteed rate has a burst size specified, it is used for the shaping rate; if the shaping rate has a burst size specified, it is used for the guaranteed rate. If you have specified a burst for both rates, the system uses the lesser of the two values.

    2. Configure the excess rate.

      You can configure an excess rate for all priorities of traffic.

      Optionally, you can configure an excess rate specifically for high- and low-priority traffic. When you configure the excess-rate statement for an interface, you cannot also configure the excess-rate-low and excess-rate-high statements.

      Best Practice:

      We recommend that you configure either a percentage or a proportion of the excess bandwidth for all schedulers with the same parent in the hierarchy. For example, if you configure interface 1.1 with twenty percent of the excess bandwidth, configure interface 1.2 with eighty percent of the excess bandwidth.

  2. (Optional) Configure parameters for the queue.
    1. Configure the shaping rate.
    2. Configure the excess rate.
    3. (Optional) Configure the priority of excess bandwidth for the queue.

      For queues, you cannot configure the excess rate in these cases:

      • When the transmit-rate exact statement is configured. In this case, the shaping rate is equal to the transmit rate and the queue does not operate in the excess region.

      • When the scheduling priority is configured as strict-high. In this case, the queue gets all available bandwidth and never operates in the excess region.

      By default, when traffic exceeds the shaping or guaranteed rates, the system demotes traffic configured with guaranteed high (GH) priority and guaranteed medium (GM) priority. To disable priority demotion, specify the none option. You cannot configure this option for queues configured with transmit-rate expressed as a percent and when the parent’s guaranteed rate is set to zero.

For example, the following statements establish a traffic control profile with a shaping rate of 80 Mbps and an excess rate of 100 percent.

The following statements establish a scheduler with an excess rate of 5 percent and a low priority for excess traffic.