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RED Drop Profiles and Congestion Control

If the device must support assured forwarding, you can control congestion by configuring random early detection (RED) drop profiles. RED drop profiles use drop probabilities for different levels of buffer fullness to determine which scheduling queue on the device is likely to drop assured forwarding packets under congested conditions. The device can drop packets when the queue buffer becomes filled to the configured percentage.

Assured forwarding traffic with the PLP (packet loss priority) bit set is more likely to be discarded than traffic without the PLP bit set. This example shows how to configure a drop probability and a queue fill level for both PLP and non-PLP assured forwarding traffic. It is only one example of how to use RED drop profiles.

The example shows how to configure the RED drop profiles listed in Table 1.

Table 1: Sample RED Drop Profiles

Drop Profile

Drop Probability

Queue Fill Level

af-normal—For non-PLP (normal) assured forwarding traffic

Between 0 (never dropped) and 100 percent (always dropped)

Between 95 and 100 percent

af-with-plp—For PLP (aggressive packet dropping) assured forwarding traffic

Between 95 and 100 percent (always dropped)

Between 80 and 95 percent

To configure RED drop profiles for assured forwarding congestion control on the device:

  1. Navigate to the top of the configuration hierarchy in either the J-Web or CLI configuration editor.

  2. Perform the configuration tasks described in Table 2.

  3. If you are finished configuring the device, commit the configuration.

  4. Go on to one of the following tasks:

Table 2: Configuring RED Drop Profiles for Assured Forwarding Congestion Control


CLI Configuration Editor

Navigate to the Class of service level in the configuration hierarchy.

From the [edit] hierarchy level, enter

edit class-of-service

Configure the lower drop probability for normal, non-PLP traffic.


edit drop-profiles af-normal interpolate

set drop-probability 0

set drop-probability 100

Configure a queue fill level for the lower non-PLP drop probability.


set fill-level 95

set fill-level 100

Configure the higher drop probability for PLP traffic.

From the [edit class of service] hierarchy level, enter

edit drop-profiles af-with-PLP interpolate

set drop-probability 95

set drop-probability 100

Configure a queue fill level for the higher PLP drop probability.


set fill-level 80

set fill-level 95