QoS Policies
Page 44
7950 XRS Quality of Service Guide
Egress Forwarding Class Override
Egress forwarding class override provides additional QoS flexibility by allowing the use of a
different forwarding class at egress than was used at ingress.
The ingress QoS processing classifies traffic into a forwarding class (or sub-class) and by default
the same forwarding class is used for this traffic at the access or network egress. The ingress
forwarding class or sub-class can be overridden so that the traffic uses a different forwarding class
at the egress. This can be configured for the main forwarding classes and for sub-classes, allowing
each to use a different forwarding class at the egress.
The buffering, queuing, policing and remarking operation at the ingress and egress remain
unchanged. Egress reclassification is possible. The profile processing (in/out) is completely
unaffected by overriding the forwarding class.
When used in conjunction with QPPB (QoS Policy Propagation Using BGP), a QPPB assigned
forwarding class takes precedence over both the normal ingress forwarding class classification
rules and any egress forwarding class overrides.
Figure 2: Egress Forwarding CLass Override
shows the ingress service 1 using forwarding classes AF and L1 that are overridden to L1
for the network egress, while it also shows ingress service 2 using forwarding classes L1, AF, and
L2 that are overridden to AF for the network egress.
Service Egress QoS Policies
Service egress queues are implemented at the transition from the service core network to the
service access network. The advantages of per-service queuing before transmission into the access
network are:
al_0187
FC EF
These 2 AF classes are
combined and use FC
L1 across the core
These 3 CP classes are
combined and use FC
L1 across the core
FC AF
FC L1
FC BE
FC EF
FC L1
FC AF
FC BE
EF
FC EF
EF
FC L2
FC AF
CP2
FC L1
CP1
FC BE
AF21
CP3
Classification
Ingress (Service 2):
Ingress (Service 1):
Egress (Network):
AF11
BE
BE
Summary of Contents for 7950
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Page 98: ...Command Hierarchies Page 98 7950 XRS Quality of Service Guide ...
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Page 164: ...Queue Depth Monitoring Page 164 7950 XRS Quality of Service Guide ...
Page 304: ...Service Queue QoS Policy Commands Page 304 7950 XRS Quality of Service Guide ...
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Page 430: ...Configuration Commands Page 430 7950 XRS Quality of Service Guide ...
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Page 552: ...Editing Advanced Policies Page 552 7950 XRS Quality of Service Guide ...
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Page 602: ...QoS Commands Page 602 7950 XRS Quality of Service Guide ...
Page 610: ...Standards and Protocols Page 610 7950 XRS Quality of Service Guide ...
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