Alcatel-Lucent 7950 Quality Of Service Manual page 59

Hierarchical Scheduler Policies
Hierarchical scheduler policies are an alternate way of scheduling queues which can be used on
service ingress and service egress queues. Hierarchical scheduler policies allow the creation of a
hierarchy of schedulers where queues and/or other schedulers are scheduled by superior
schedulers.
The use of the hierarchical scheduler policies is often referred to as hierarchical QoS or H-QoS on
the SR OS.
Hierarchical Virtual Schedulers
Virtual schedulers are created within the context of a hierarchical scheduler policy. A hierarchical
scheduler policy defines the hierarchy and parameters for each scheduler. A scheduler is defined in
the context of a tier (Tier 1, Tier 2, Tier 3). The tier level determines the scheduler's position
within the hierarchy. Three tiers of virtual schedulers are supported
(also called root schedulers) are defined without a parent scheduler. It is not necessary for Tier 1
schedulers to obtain bandwidth from a higher tier scheduler. A scheduler can enforce a maximum
rate of operation for all child queues and associated schedulers.
7950 XRS Quality of Service Guide
QoS Policies
(Figure 5). Tier 1 schedulers
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