Juniper EX9200 Series User Manual

priority. You set loss priority by configuring a classifier or a policer. The loss priority is
used later in the workflow to select one of the drop profiles used by RED.
•
Forwarding policy options—These options allow you to associate forwarding classes
with next hops. Forwarding policy also allows you to create classification overrides,
which assign forwarding classes to sets of prefixes.
•
Transmission scheduling and rate control—These parameters provide you with a variety
of tools to manage traffic flows:
•
Queuing—After a packet is sent to the outgoing interface on a routing device, it is
queued for transmission on the physical media. The amount of time a packet is
queued on the routing device is determined by the availability of the outgoing physical
media as well as the amount of traffic using the interface.
•
Schedulers—An individual routing device interface has multiple queues assigned to
store packets. The routing device determines which queue to service based on a
particular method of scheduling. This process often involves a determination of
which type of packet should be transmitted before another. The Junos OS schedulers
allow you to define the priority, bandwidth, delay buffer size, rate control status, and
RED drop profiles to be applied to a particular queue for packet transmission.
•
Fabric schedulers—For M320 and T Series routers 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—Policers 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, a different loss priority,
or both. You define policers with filters that can be associated with input or output
interfaces.
•
Rewrite rules—A rewrite rule sets the appropriate CoS bits in the outgoing packet. This
allows the next downstream routing device to classify the packet into the appropriate
service group. Rewriting, or marking, outbound packets is useful when the routing device
is at the border of a network and must alter the CoS values to meet the policies of the
targeted peer.
Default CoS Settings
If you do not configure any CoS settings on your routing device, the software performs
some CoS functions to ensure that user traffic and protocol packets are forwarded with
minimum delay when the network is experiencing congestion. Some default mappings
are automatically applied to each logical interface that you configure. Other default
mappings, such as explicit default classifiers and rewrite rules, are in operation only if
you explicitly associate them with an interface.
You can display default CoS settings by issuing the show class-of-service operational
mode command. This section includes sample output displaying the default CoS settings.
The sample output is truncated for brevity.
Copyright © 2013, Juniper Networks, Inc.6
Class of Service Overview and Examples for EX9200 Switches

Juniper EX9200 Series Specifications

General

Brand	Juniper
Model	EX9200 Series
Category	Switch
Language	English