How Forwarding Classes And Schedulers Work; Default Forwarding Class Queue Assignments - Juniper J2300 User Manual

J-series™ Services Router User Guide
CoS Component
Forwarding policy options
Transmission scheduling and rate
control
Rewrite markers

How Forwarding Classes and Schedulers Work

This section contains the following topics:

Default Forwarding Class Queue Assignments

J-series routers have only four queues built into the hardware. Other routing
platforms can be configured for up to eight queues. If a classifier does not
assign a packet to any other queue (for example, for other than well-known
DSCPs that have not been added to the classifier), the packet is assigned
by default to the class associated with queue 0.
Table 140 shows the four forwarding classes and queues that Juniper Networks
classifiers assign to packets based on the DSCP values in arriving packet headers.
370
Class-of-Service Overview
Use
Allow you to associate forwarding classes with next hops.
Allow you to create classification overrides, which assign forwarding classes to
sets of prefixes.
Provide you with a variety of tools to manage traffic flows. The following types are
available:
Schedulers—Allow you to define the priority, bandwidth, delay buffer size,
rate control status, and RED drop profiles to be applied to a particular
forwarding class for packet transmission. Drop profiles are useful for the
assured forwarding service class.
Fabric schedulers—For M320 and T-series platforms only, fabric schedulers
allow you to identify a packet as high or low priority based on its forwarding
class, and to associate schedulers with the fabric priorities.
Policers for traffic classes—Allow you to limit traffic of a certain class to a
specified bandwidth and burst size. Packets exceeding the policer limits
can be discarded, or can be assigned to a different forwarding class or to a
different loss priority, or to both. You define policers with filters that can
be associated with input or output interfaces. Policers are useful for the
expedited forwarding service class.
Allow you to redefine the DSCP value of outgoing packets. Rewriting or marking
outbound packets is useful when the routing platform is at the border of a network
and must alter the code points to meet the policies of the targeted peer.
"Default Forwarding Class Queue Assignments" on page 370
"Default Scheduler Settings" on page 371
"Default Behavior Aggregate (BA) Classifiers" on page 372
"DSCP Rewrites" on page 373
"Sample BA Classification" on page 373