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Determining Packet Drop Behavior by Configuring Drop Profile Maps for Schedulers

RED drop profiles take action on outgoing packets. When tricolor marking is enabled, Junos devices support four drop-profile map PLP designations: low, medium-low, medium-high, and high.

Drop-profile maps associate RED drop profiles with a scheduler. The map examines the current loss priority setting of the packet (low, medium-low, medium-high, or high) and assigns a drop profile according to these values. For example, you can specify that all TCP packets with low loss priority are assigned a drop profile that you name low-drop. You can associate multiple drop-profile maps with a single queue.

The scheduler drop profile defines the drop probabilities across the range of delay-buffer occupancy, thereby supporting the RED process. Depending on the drop probabilities, RED might drop packets aggressively long before the buffer becomes full, or it might drop only a few packets even if the buffer is almost full. For information on how to configure drop profiles, see RED Drop Profiles for Congestion Management.

By default, the drop profile is mapped to packets with low PLP and any protocol type.

When you configure TCM, the drop-profile map’s protocol type must be any.

The map sets the drop profile for a specific PLP and protocol type. The inputs for the map are the PLP and the protocol type. The output is the drop profile. In other words, the map sets the drop profile for each packet with a specific PLP and protocol type exiting the interface. For more information about how CoS maps work, see Mapping CoS Component Inputs to Outputs.

Note:

You can configure only the any option for the protocol statement.

For each scheduler, you can configure separate drop profile maps for each loss priority.

You can configure a maximum of 32 different drop profiles.

In the following sample configuration, the dp drop profile is assigned to all packets exiting the interface with a medium-low PLP and belonging to any protocol:To configure this drop profile map:

  1. Specify the name of the scheduler.
  2. Define the loss-priority value for a drop profile, the protocol type, and the name of the drop profile..
  3. Verify your configuration.
  4. Save your configuration.
Note:

To use this drop-profile map, you must configure the settings for the dp drop profile at the [edit class-of-service drop-profiles dp] hierarchy level..

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