Shared-queue policies

General Information

A shared-queue policy can be applied to daughter cards for optional use by SAPs. The NFM-P provides one shared-queue policy for all eight default queues. Each queue is associated with a default forwarding class.

Shared-queue QoS policies can be implemented to facilitate queue consumption on a daughter card; for example, when VPLS, IES, and VPRN services are scaled on one card. Instead of allocating multiple hardware queues for each unicast queue that is defined in an access ingress policy, SAPs with the shared-queuing feature enabled only allocate one hardware queue for each unicast queue.

However, the total amount of traffic throughput at ingress is reduced because ingress packets that are serviced by a shared-queuing SAP are recirculated for additional processing. This can reduce the available bandwidth by half. Shared queuing can also add latency. Network planners should consider these restrictions when they try to scale services on one daughter card.

The following table lists the queue IDs used by the NFM-P to identify the shared-queue types.

Table 50-6: Shared queue types

Shared-queue ID

Shared-queue type

1 to 8

Unicast

9 to 16

Multicast

17 to 25

Broadcast

26 to 32

Unknown

Note: Queue IDs 9 to 32 are also known as multipoint shared queues.

Shared policer output queue

To support hierarchical policing, a default policer output queue policy is applied automatically to each IOM that supports ingress policing. In the NFM-P, this shared policer output queue is modeled in the same manner as the existing default shared queue, except that it has only 16 queues.

Multipoint shared-queue policies

Multipoint shared queues minimize the number of multipoint queues that are created for the following:

Typically, ingress multipoint packets are handled by multipoint queues that are created for each SAP or subscriber SLA profile instance. In some cases, the number of SAPs or SLA profile instances are sufficient for the in-use multipoint queues to represent many thousands of queues on an ingress forwarding plane. If multipoint shared queuing is enabled for the SAPs or SLA profile instances on the forwarding plane, the multipoint queues are not created. Instead, the ingress multipoint packets are handled by the unicast queue that is mapped to the forwarding class of the multipoint packet.

Multipoint shared queues are a superset of shared queuing. With shared queuing on a SAP or SLA profile instance, only unicast packets are processed twice; once for the initial service-level queuing and a second time for switch fabric destination queuing. Shared queuing does not affect multipoint packet handling. Multipoint packet handling in normal service queuing is the same as shared queuing. Shared queuing for unicast packets is automatically enabled when you enable multipoint shared queuing.

The NFM-P supports multipoint shared-queue policies for the following services on the 7750 SR, 7450 ESS:

See the following chapters for more information about enabling multipoint shared queues for a service:

You can also enable multipoint shared queues in an existing shared-queue policy. See the procedures in this chapter for more information about editing shared-queue policies.