that set of queues to the shared rate. The shared-shaping rate is the total bandwidth
for the logical interface.
A typical configuration places the low-latency voice traffic in the auto-strict-priority
traffic-class group and video traffic in a separate extended traffic-class group. The
data traffic is usually queued in the best-effort traffic class in the default traffic-class
group.
The constraints of both the legacy hierarchical scheduler and the shared shaper affect
the bandwidth of scheduler objects. The shared shaper limits the bandwidth even
when the port or VP is not congested. When the port or VP is congested, the legacy
scheduler is dominant. For example, when a heavily oversubscribed VP becomes
congested, the legacy hierarchical scheduler may limit the VP bandwidth to a lower
rate, so that shared shaping of excess bandwidth does not apply.
When determining the shared-shaping rate, the system includes all bytes in Layer 2
encapsulations. The packets that are included in the rate depend on the Layer 2 node
that is specified in the QoS profile. For example, the shaping rate for an Ethernet
node includes bytes from the Ethernet and VLAN encapsulations.
Two types of shared shaping are available, depending on your hardware.
Simple
shared shaping can shape the best-effort node or queue associated with a logical
interface to a shared rate.
Compound
shared shaping is a hardware-assisted mode
that controls bandwidth for all scheduler objects associated with the subscriber logical
interface.
Table 7 on page 73 compares the two types of shared shaping that are available.
Table 7: Comparison of Simple and Compound Shared Shaping
Advantages
Shared Shaper
■
Simple shared shaping is useful for triple-play
configurations, because it manages voice and video queues
in addition to data queues so that the shared rate cannot
be exceeded.
■
You can use line modules that have any ASIC hardware.
Simple
■
Compound shared shaping is useful for triple-play
configurations, because it manages voice and video queues
in addition to data queues so that the shared rate cannot
be exceeded.
■
Compound shared shaping responds to changes in traffic
rates more rapidly than simple shared shaping, in the order
of milliseconds.
■
You can use line modules with the EFA2 ASIC or the TFA
ASIC.
Compound
Active Constituents for Shared Shaping
When you specify a shared-shaping rate on a best-effort node or queue, QoS shapes
the aggregate of traffic for the logical interface that owns the best-effort queue or
How Shared Shaping Works
■
73
Chapter 9: Shared Shaping Overview
Содержание JUNOSE 11.1.X - QUALITY OF SERVICE CONFIGURATION GUIDE 3-21-2010
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Страница 162: ...130 Scaling Subscribers on the TFA ASIC with QoS JUNOSe 11 1 x Quality of Service Configuration Guide...
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Страница 238: ...206 Monitoring QoS Configurations for L2TP JUNOSe 11 1 x Quality of Service Configuration Guide...
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Страница 388: ...356 Monitoring QoS Parameter Definitions JUNOSe 11 1 x Quality of Service Configuration Guide...
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