Frequently Used QoS Terms
Quality of Service Guide 893
Scheduler Policy
A scheduler policy represents a particular grouping of virtual schedulers that are defined in
specific scheduler tiers. The tiers and internal parent associations between the schedulers
establish the hierarchy among the virtual schedulers. A scheduler policy can be applied to
either a multi-service site or to a service Service Access Point (SAP). Once the policy is
applied to a site or SAP, the schedulers in the policy are instantiated on the object and are
available for use by child queues directly or indirectly associated with the object.
Tier
A tier is an organizational configuration used within a scheduler policy to define the place of
schedulers created in the policy. Three tiers are supported; Tier 1, Tier 2, and Tier 3.
Schedulers defined in Tier 2 can have parental associations with schedulers defined in Tier 1.
Schedulers defined in Tier 3 can have parental associations with schedulers defined at Tiers
1 or 2. Queues can have parental associations with schedulers at any tier level.
Virtual Scheduler
A virtual scheduler, defined by a name (text string), is a logical configuration used as a parent
to a group of child members that are dependent upon a common parent for bandwidth
allocation. The virtual scheduler can also be a child member to another parent virtual
scheduler and receive bandwidth from that parent to distribute to its child members.
Weight
The weight parameter defines the weight within the ‘above CIR’ level given to a child queue
or scheduler. When several children share the same level on a parent scheduler, the ratio of
bandwidth give to an individual child is dependent on the ratio of the weights of the active
children. A child is considered active when a portion of the offered load is above the CIR
value (also bounded by the child’s maximum bandwidth defined by the child’s rate
parameter). The portion of bandwidth given to each child is based on the child’s weight
compared to the sum of the weights of all active children at that level. A weight of zero forces
the child to receive bandwidth only after all other children at that level have received their
‘above CIR’ bandwidth. When several children share a weight of zero, all are treated equally.
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