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

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Although a shared shaper can be applied to up to eight constituents, only four of
these can be weighted constituents. If you configure more than four weighted
constituents as part of the same shared shaper, the first four are treated as weighted
constituents but the remainder are handled as strict constituents, generating a warning
message.
Weighted Compound Shared Shaping Example
Weighted shared shaping is most useful for sharing bandwidth between traffic classes
carrying TCP data. Figure 31 on page 113 shows an application of weighted shared
shaping where weighted constituents span multiple traffic class groups, making them
ineligible for legacy weighted scheduling. Best-effort data and premium data
constituents are weighted.
Figure 31: Weighted Shared Shaping
Scheduler profile A specifies the shared-shaping rate of 1Mbps for the best-effort
node, which is associated with a VC logical interface. The node is further configured
with a weight of 1. Scheduler profile B specifies the VC 1 AF node as a weighted
constituent with a weight of 31.
The implicitly selected constituents of the shared shaper are the VC 1 best-effort
node, the VC 1 AF group node, and the VC 1 EF group node. Bandwidth is allocated
as follows:
■
The VC 1 EF group node is strict and can transmit up to the shared-shaping rate
of 1Mbps. Any remaining bandwidth is available to the remaining constituents.
■
The VC 1 AF group node is weighted with the VC 1 best-effort node. The sum of
the constituent weights is 32. With a weight of 31, the VC 1 AF group node can
transmit 31/32nds of the available bandwidth when both constituents are
competing for bandwidth.
Implicit Constituent Selection Overview
■ 113
Chapter 13: Configuring Implicit and Explicit Constituent Selection for Shaping