A scheduler policy defines the hierarchy and all operating parameters for the member schedulers. A scheduler policy must be defined in the QoS context before a group of virtual schedulers can be used. Although configured in a scheduler policy, the individual schedulers are created when the policy is applied to an object, such as a SAP or interface.
Scheduler objects define bandwidth controls that limit each child (other schedulers and policers or queues) associated with the scheduler. The scheduler object can also define a child association with a parent scheduler of its own.
A scheduler is used to define a bandwidth aggregation point within the hierarchy of virtual schedulers. The scheduler’s rate defines the maximum bandwidth that the scheduler can consume. It is assumed that each scheduler created has policers, queues, or other schedulers defined as child associations. The scheduler can also be a child which takes bandwidth from a scheduler in a higher tier.
A parent parameter can be defined to specify a scheduler further up in the scheduler policy hierarchy. Only schedulers in Tiers 2 and 3 can have parental association. When multiple schedulers, policers, and queues share a child status with the scheduler on the parent, the weight or strict parameters define how this scheduler contends with the other children for the parent’s bandwidth. The parent scheduler can be removed or changed at any time and is immediately reflected on the schedulers created by association of this scheduler policy.
When a parent scheduler is defined without specifying level, weight, or CIR parameters, the default bandwidth access method is weight with a value of 1.
If any orphaned policers or queues (where the specified scheduler name does not exist) exist on the ingress SAP and the policy application creates the required scheduler, the status on the queue becomes non-orphaned at this time.
Figure: Virtual scheduler internal bandwidth allocation shows how child queues, policers, and schedulers interact with their parent scheduler to receive bandwidth. The scheduler distributes bandwidth to the children by first using each child’s CIR according to the CIR-level parameter (CIR L8 through CIR L1 weighted loops). The weighting at each CIR-level loop is defined by the CIR weight parameter for each child. The scheduler then distributes any remaining bandwidth to the children up to each child’s rate parameter according to the Level parameter (L8 through L1 weighted loops). The weighting at each level loop is defined by the weight parameter for each child.
