Shaping Rates, Assured Rates, And Relative Weights In A Scheduler; Figure 8: Qos Scheduler Hierarchy - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - QUALITY OF SERVICE CONFIGURATION GUIDE 2010-09-22 Configuration Manual

JunosE 11.3.x Quality of Service Configuration Guide

Figure 8: QoS Scheduler Hierarchy

Shaping Rates, Assured Rates, and Relative Weights in a Scheduler Hierarchy
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The scheduler supports hierarchical and static assured rates, relative weights, and shaping
rates on all three levels of the hierarchy: first-level node, second-level node, and queue.
The bandwidth delivered from a given node or queue is a function of the shaping rate
and either the assured rate or relative weight:
When the scheduler is not congested, the shaping rates determine which node or queue
can claim the bandwidth. The shaping rate specifies the maximum bandwidth to the
node or queue.
When the scheduler is congested, either the hierarchical or static assured rate or the
weight specifies the minimum bandwidth.
If the scheduler is configured to use a static assured rate and the assured rate is
other than none (the default), it is used to determine the allocated bandwidth, and
the weight setting is ignored. If the assured rate is zero, the weight setting is used to
determine the bandwidth.
The static assured rate specifies the desired bandwidth. This rate is guaranteed until
the bandwidth becomes oversubscribed.
If the scheduler is configured to use hierarchical assured rate, the scheduler
dynamically adjusts the amount of allocated bandwidth for service delivery based
on the sum of the assured rates of all child nodes and queues.
The assured rate also specifies that if bandwidth is over- or undersubscribed, all
adjustments are made in proportion to the original assured-rate specification.
For example, if Node A is configured to receive 40 Mbps and Node B receives 20
Mbps, any available bandwidth above the subscribed total of 60 Mbps would be
allocated to the two nodes at the same 2-to-1 ratio. Similarly, if the bandwidth were
oversubscribed and only 30 Mbps were available, this amount would also be allocated
to the two nodes at the 2-to-1 ratio, with Node A getting 20 Mbps and Node B getting
10 Mbps.
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