QoS: Marking using Policers

Traffic policers measure the traffic rate for data entering or exiting an interface with the goal of determining whether a traffic contract has been exceeded.  The traffic contract consists of two components:

  • Traffic Rate configured in bits/second
  • Burst Size: configured as a number of bytes

If traffic is within the contracted rate its considered to be conformed and may pass through.

If traffic exceeds  the contracted rate its subject to being dropped.

However there is a compromise action that takes place in which a policer marks down packets instead of dropping them.  It remarks the exceeded packet using IPP or DSCP to a value that makes the packet more likely to be discarded downstream but still allows the packet to pass through the local router.


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