Mpls Qos Features; Mpls Experimental Field; Trust; Classification - Cisco WS-SUP32-GE-3B - Supervisor Engine 32 Software Configuration Manual

Chapter 39 Configuring MPLS QoS

MPLS QoS Features

QoS enables a network to provide improved service to selected network traffic. This section explains the
following MPLS QoS features, which are supported in an MPLS network:
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MPLS Experimental Field

Setting the MPLS experimental (EXP) field value satisfies the requirement of service providers who do
not want the value of the IP precedence field modified within IP packets transported through their
networks.
By choosing different values for the MPLS EXP field, you can mark packets so that packets have the
priority that they require during periods of congestion.
By default, the IP precedence value is copied into the MPLS EXP field during imposition.You can mark
the MPLS EXP bits with a MPLS QoS policy.

Trust

For received Layer 3 MPLS packets, the PFC3B usually trusts the EXP value in the received topmost
label. None of the following have any effect on MPLS packets:
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For received Layer 2 MPLS packets, the PFC3B can either trust the EXP value in the received topmost
label or apply port trust or policy trust to the MPLS packets for CoS and egress queueing purposes.

Classification

Classification is the process that selects the traffic to be marked. Classification accomplishes this by
partitioning traffic into multiple priority levels, or classes of service. Traffic classification is the primary
component of class-based QoS provisioning. The PFC3B makes classification decisions based on the
EXP bits in the received topmost label of received MPLS packets (after a policy is installed). See the
"Configuring a Class Map to Classify MPLS Packets" section on page 39-20
OL-11439-03
MPLS Experimental Field, page 39-3
Trust, page 39-3
Classification, page 39-3
Policing and Marking, page 39-4
Preserving IP ToS, page 39-4
EXP Mutation, page 39-4
MPLS DiffServ Tunneling Modes, page 39-4
Interface trust state
Port CoS value
Policy-map trust command
Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY
MPLS QoS Features
for information.
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