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PICs Restricted to Four Queues

Some T-series PICs support up to 16 forwarding classes and are restricted to 4 queues. Contact Juniper Networks customer support for a current list of T-series PICs that are restricted to four queues. To determine how many queues an interface supports, you can check the CoS queues output field of the show interfaces interface-name extensive command:

user@host> show interfaces so-1/0/0
extensive

CoS queues: 8 supported

By default, for T-series PICs that are restricted to four queues, the routing platform overrides the global configuration based on the following formula:



Qr = Qd mod Rmax

Qr is the queue number assigned if the PIC is restricted to four queues.

Qd is the queue number that would have been mapped if this PIC were not restricted.

Rmax is the maximum number of restricted queues available. Currently, this is four.

For example, assume you map the forwarding class ef to queue 6. For a PIC restricted to four queues, the queue number for forwarding class ef is Qr = 6 mod 4 = 2.

To determine which queue is assigned to a forwarding class, use the show class-of-service forwarding-class command from the top level of the CLI. The output shows queue assignments for both global queue mappings and restricted queue mappings:

user@host> show class-of-service forwarding-class

Forwarding class           Queue     Restricted Queue  Fabric priority
  be                                    0           2             low
  ef                                    1           2             low
  assured-forwarding                    2           2             low
  network-control                       3           3             low

For T-series PICs restricted to four queues, you can override the formula-derived queue assignment by including the restricted-queues statement at the [edit class-of-service] hierarchy level:



[edit class-of-service]

restricted-queues {

forwarding-class class-name queue queue-number;
}

You can configure up to 16 forwarding classes. The output queue number can be from 0 through 3. Therefore, for PICs restricted to four queues, you can map multiple forwarding classes to single queues. If you map multiple forwarding classes to a queue, the multiple forwarding classes must refer to the same scheduler. The class name you configure at the [edit class-of-service restricted-queues] hierarchy level must be either a default forwarding class name from Table 27, or a forwarding class you configure at the [edit class-of-service forwarding-classes] hierarchy level.

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