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Scheduler Delay Buffering on MIC and MPC Interfaces

To control congestion at the output stage, you can configure the delay-buffer bandwidth. Scheduler delay-buffer bandwidth provides packet buffer space to absorb burst traffic up to the specified duration of delay. After the specified delay buffer becomes full, packets with 100 percent drop probability are dropped from the head of the buffer.

The buffer size is the amount of time in milliseconds of port bandwidth that a queue can use to continue to transmit packets during periods of congestion, before the buffer runs out and packets begin to drop.

For MIC and MPC interfaces the default maximum queue buffer size is:

  • 500 ms for traffic rates below 1 Gbps.

  • 100 ms for traffic rates of 1 Gbps and faster.

  • 100 ms for all tunnel interfaces configured on MIC and MPC interfaces

You can configure an explicit buffer size ranging from 4 KB to 256 MB, depending on the MIC or MPC model. However, MIC and MPC interfaces do not support the large delay buffer size configuration statement q-pic-large-buffer.

Interfaces hosted on MIC and MPC line cards have a certain granularity in the application of configured delay buffer parameters. In other words, the observed hardware value might not exactly match the user-configured value. Nevertheless, the derived values are as close to the configured values as allowed.

When you configure an explicit buffer size, there are 256 points available and the closest point is chosen. High-priority and medium-priority queues use 64 points, and the low-priority queues uses 128.