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 behavior aggregate (BA) or multifield classifier, as discussed in Overview of BA Classifier Types and Multifield Classifier Overview.
However, on Juniper Networks M320 Multiservice Edge Routers, MX Series 3D Universal Edge Routers, and T Series Core Routers that do not have tricolor marking enabled, the loss priority can be configured by setting the PLP within a multifield classifier or by behavior aggregate (BA) classifier. This setting can then be used by the appropriate drop profile map and rewrite rule.
On M320 routers and T Series routers with Enhanced II Flexible PIC Concentrators (FPCs) and tricolor marking enabled, you can set the PLP with a BA or multifield classifier, as described in Using BA Classifiers to Set PLP and Using Multifield Classifiers to Set PLP.
On T Series routers with different Packet Forwarding Engines (non-Enhanced Scaling and Enhanced Scaling FPCs) and on M320 routers you can configure PLP bit copying for ingress and egress unicast and multicast traffic. To configure PLP bit copying, include the copy-plp-all statement at the [edit class-of-service] hierarchy level.
Example: Overriding the Default PLP on M320 Routers
The following example shows a two-step procedure to override the default PLP settings on M320 routers:
- 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;}}}}
- For M320 routers, this multifield classifier sets the
PLP.firewall {filter ef-filter {term ef-multifield {from {precedence 6;}then {loss-priority high;forwarding-class expedited-forwarding;}}}}
