Setting Packet Loss Priority

By default, the least significant bit of the CoS value sets the packet loss priority (PLP) value. For example, CoS value 000 is associated with PLP low, and CoS value 001 is associated with PLP high. In general, you can change the PLP by configuring a BA or MF classifier, as discussed in Classifier Types.

However, on M320, MX-series, and T-series routing platforms that do not have tricolor marking enabled, the loss priority can be configured only by setting the PLP within an MF classifier. This setting can then be used by the appropriate drop profile map and rewrite rule.

On M320 and T-series routing platforms with Enhanced II Flexible PIC Concentrators (FPCs) and tricolor marking enabled, you can set the PLP with a BA or MF classifier, as described in Using BA Classifiers to Set PLP and Using Multifield Classifiers to Set PLP.

Example: Overriding the Default PLP on M320 Routers

Override the default PLP.

1. The following example specifies that while the DSCP code points are 110, the loss priority is set to high; however, on M320 routers, overriding the default PLP this way has no effect.

   class-of-service {

   classifiers {

   dscp ba-classifier {

   forwarding-class expedited-forwarding {

   loss-priority high code-points 110;

   }

   }

   }

   }

2. For M320 routers, this MF classifier sets the PLP.

   firewall {

   filter ef-filter {

   term ef-multifield {

   from {

   precedence 6;

   }

   then {

   loss-priority high;

   forwarding-class expedited-forwarding;

   }

   }

   }

   }