Juniper JUNOSE 11.1.X - QUALITY OF SERVICE CONFIGURATION GUIDE 3-21-2010, Configuration Manual

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Chapter 8
Configuring Strict-Priority Scheduling
This chapter provides information for configuring strict-priority scheduling.
QoS topics are discussed in the following sections:
■
Strict-Priority and Relative Strict-Priority Scheduling Overview on page 59
■
Comparison of True Strict Priority with Relative Strict Priority
Scheduling on page 61
■
Configuring Strict-Priority Scheduling on page 66
■
Configuring Relative Strict-Priority Scheduling for Aggregate Shaping
Rates on page 68
Strict-Priority and Relative Strict-Priority Scheduling Overview
You can configure one or more strict-priority queues per interface. Strict-priority
scheduling is implemented with a special strict-priority scheduler node that is stacked
directly above the port. Queues stacked on top of the strict-priority scheduler node
always get bandwidth before other queues.
You can configure only one node at the first scheduler level as strict priority. If any
node or queue above the strict-priority node has packets, it is scheduled next. If
multiple queues above the strict-priority node have packets, the HRR algorithm selects
which strict-priority queue is scheduled next.
Figure 11 on page 60 illustrates an example of a QoS scheduler’s hierarchy.
Strict-Priority and Relative Strict-Priority Scheduling Overview
■ 59