QoS - WRED traffic profile thresholds

Weighted Random Early Detection (WRED) is a QoS mechanism used to manage the tail end of a queue, and in particular, to mitigate against TCP global synchronization.

Refer to the following traffic profile of a particular WRED configuration:


This particular traffic profile has the following thresholds:

  • Minimum threshold: 20 packets
  • Maximum threshold: 45 packets
  • MPD (Mark Probability Denominator): 25%

These values can be configured of course. For this specific example:

  • for average queue depth values between 0 and 20, there are zero drops.
  • for average queue depth values between 20 and 45 there is an increasing number of drops depending upon the queue depth.
  • for average queue depth values exceeding 45, all packets are dropped.

For queue depth values between 20 and 45, the percentage of dropped packets goes from 0 to a maximum of 25%. The MPD is that value of 25%.




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