Help us improve your experience.

Let us know what you think.

Do you have time for a two-minute survey?

TechLibrary
Navigation

Defining CoS Forwarding Classes

Forwarding classes allow you to group packets for transmission. The switch supports a total of 12 forwarding classes. In order to forward traffic, you map (assign) the forwarding classes to unicast or multidestination (multicast, broadcast, and destination lookup fail) output queues.

The switch has 12 output queues. Queues 0 through 7 are for unicast traffic and queues 8 through 11 are for multicast traffic. Forwarding classes mapped to unicast queues must carry unicast traffic, and forwarding classes mapped to multidestination queues must carry multidestination traffic. There are four default unicast forwarding classes and one default multidestination forwarding class.

The default unicast forwarding classes are:

  • best-effort—Best-effort traffic
  • fcoe—Guaranteed delivery for FCoE traffic
  • no-loss—Guaranteed delivery for TCP no-loss traffic
  • network-control—Network control traffic

The default multidestination forwarding class is:

  • mcast—Multidestination traffic

Map forwarding classes to queues using the class statement, which enables you to configure up to 12 forwarding classes. You can map more than one forwarding class to a single queue, but all forwarding classes mapped to a particular queue must be of the same type, either unicast or multicast. In addition, all forwarding classes mapped to a particular queue must be either lossless or lossy. You cannot mix lossless and lossy forwarding classes (traffic) on the same queue. Also, you cannot mix unicast and multicast forwarding classes on the same queue.

[edit class-of-service forwarding-classes]
user@switch# class class-name queue-num queue-number <no-loss>

Note: If you are using Junos OS Release 12.2 or later, use the default forwarding-class-to-queue mapping for the lossless fcoe and no-loss forwarding classes. If you explicitly configure the lossless forwarding classes, the traffic mapped to those forwarding classes is treated as lossy (best-effort) traffic and does not receive lossless treatment unless you include the optional no-loss packet drop attribute introduced in Junos OS Release 12.3 in the forwarding class configuration..

Note: Junos OS Release 11.3R1 and earlier supported an alternate method of mapping forwarding classes to queues that allowed you to map only one forwarding class to a queue using the statement:

[edit class-of-service forwarding-classes]
user@switch# queue queue-number class-name

The queue statement has been deprecated and is no longer valid in Junos OS Release 11.3R2 and later. If you have a configuration that uses the queue statement to map forwarding classes to queues, edit the configuration to replace the queue statement with the class statement.

 

Related Documentation

 

Published: 2014-07-23

Previous Page Next Page