QoS Policies
56 Quality of Service Guide
Named Pool Policies
The named buffer pool feature for the 7450 ESS and 7750 SR allows for the creation of
named buffer pools at the MDA and port level. Named pools allow for a customized buffer
allocation mode for ingress and egress queues that goes beyond the default pool behavior.
Named pools are defined within a named pool policy. The policy contains a q1-pools context
which is used to define port allocation weights and named pools for buffer pools on Q1 based
IOMs (all IOMs that are currently supported). The policy may be applied at either the port or
MDA level at which time the pools defined within the policy are created on the port or MDA.
When the policy is applied at the MDA level, MDA named pools are created. MDA named
pools will typically be used when either a pool cannot be created per port or when the
buffering needs of queues mapped to the pool are not affected by sharing the pool with queues
from other ports. MDA named pools allow buffers to be efficiently shared between queues
on different ports mapped to the same pool. However, MDA named pools do present the
possibility that very active queues on one port could deplete buffers in the pool offering the
possibility that queues on other ports experiencing buffer starvation. Port named pools are
created when the policy is applied at the port level and allow for a more surgical application
of the buffer space allocated for a physical port. MDA pool names do not need to be unique.
If a name overlaps exists, the port pool will be used. The same pool name may be created on
multiple ports on the same MDA.
The named pool policy is applied at the MDA ingress and egress level and at the ingress and
egress port level. Each MDA within the system is associated with a forwarding plane traffic
manager that has support for a maximum of 57 buffer pools. The following circumstances
affect the number of named pools that can be created per MDA (these circumstances may be
different between ingress and egress for the MDA):
• The forwarding plane can be associated with multiple MDAs (each MDA has its own
named pools)
• A single system level pool for system created queues is allocated
• There must be default pools for queues that are not explicitly mapped or are
incorrectly mapped to a named pool
• Default pools for most IOM types (separate for ingress and egress)
• Access pool
Flows Default
Action
1 (one) flow defined for all traffic classes:
• All traffic mapped to queue 1 with no marking
Table 13: Default Service Egress Policy ID 1 Definition (Continued)
Characteristic Item Definition
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