Virtual Hierarchical Scheduling - Alcatel-Lucent 7450 Quality Of Service Manual

Virtual Hierarchical Scheduling

Virtual hierarchical scheduling is a method that defines a bounded operation for a group of
queues. One or more queues are mapped to a given scheduler with strict and weighted metrics
controlling access to the scheduler. The scheduler has an optional prescribed maximum
operating rate that limits the aggregate rate of the child queues. This scheduler may then feed
into another virtual scheduler in a higher tier. The creation of a hierarchy of schedulers and
the association of queues to the hierarchy allows for a hierarchical Service Level Agreement
(SLA) to be enforced.
Scheduler policies in the routers determine the order queues are serviced. All ingress and
egress queues operate within the context of a scheduler. Multiple queues share the same
scheduler. Schedulers control the data transfer between the following queues and
destinations:
There are two types of scheduler policies:
Schedulers and scheduler policies control the data transfer between queues, switch fabric
destinations and egress ports/interfaces. The type of scheduling available for the various
scheduling points within the system are summarized in
Scheduling From
Service Ingress Queues
Service Egress Queues
Network Ingress Queues
Network Egress Queues
Quality of Service Guide
• Service ingress queues to switch fabric destinations.
• Service egress queues to access egress ports.
• Network ingress queues to switch fabric destinations.
• Network egress queues to network egress interfaces.
• Single Tier Scheduling
• Hierarchical Scheduler Policies
Table 16: Supported Scheduler Policies
To
Switch Fabric Destinations
Access Egress Ports
Switch Fabric Destinations
Network Egress Interfaces
Table 16.
Single-Tier Hierarchical
Yes Yes
Yes Yes
Yes No
Yes No
QoS Policies
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