Logical Interface Traffic Carried In Other Queues; Traffic Starvation And Shared Shaping; Figure 17: Implicit Constituent Selection For Compound Shared Shaper: Mixed - 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

Logical Interface Traffic Carried in Other Queues

Figure 17: Implicit Constituent Selection for Compound Shared Shaper: Mixed Interface Types

Traffic Starvation and Shared Shaping

72
For more information about configuring low-CDV mode, see "ATM Integrated Scheduler
Overview" on page 151.
A shared shaper affects only the queues and nodes for a single interface. Queues
associated with other interfaces are not constrained by the shared shaper. This behavior
should cause no problems if you configure all queues for a single logical interface type.
However, if you configure queues for multiple interface types, you may have problems
with shared shaping.
For example, a shared shaper for VC 1 does not directly constrain the rate for a queue for
IP 1 unless that queue is stacked above a node for VC 1 in the scheduler hierarchy. If the
IP queue is stacked above a node for VC 1, then the shared shaper indirectly controls the
queue bandwidth through the VC 1 node. But if the IP 1 queue is not stacked above a VC
1 node, it is immune to the shared shaper, and the total bandwidth for VC 1 can exceed
the shared rate.
As another example, if a shared queue exists for VP 1 where VC 1 is contained within VP
1, the shared shaper for VC 1 does not constrain the bandwidth of a VP queue. The total
bandwidth for VC 1 can again exceed the shared rate.
Figure 17 on page 72 illustrates an example of mixed interface shaping and its implications
for implicit constituent selection for compound shared shaping.
Traffic in the strict-priority traffic-class group can starve out other traffic competing
within the shared shaper. You might want to configure an individual shaping rate for
strict-priority queues, thus reserving the remaining shared bandwidth for nonstrict traffic.
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