Alcatel-Lucent 7950, Quality Of Service Manual

Page: 54 / 612

QoS Policies
Page 54 7950 XRS Quality of Service Guide
Scheduler Policies
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 actually created
when the policy is applied to a site, such as a SAP or interface.
Scheduler objects define bandwidth controls that limit each child (other schedulers and 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 will have queues or other schedulers defined as child
associations. The scheduler can also be a child (take bandwidth from) a scheduler in a higher tier,
except for schedulers created in Tier 1.
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. Tier 1 schedulers cannot
have a parental association. When multiple schedulers and/or 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
anytime and is immediately reflected on the schedulers actually 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 queues (queues specifying a scheduler name that 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 4 depicts how child queues 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.