Cisco 7604 Configuration Manual page 740

Understanding PFC3BXL or PFC3B Mode MPLS QoS
PFC3BXL or PFC3B mode MPLS QoS maps the EXP value to the internal DSCP using the
EXP-to-DSCP global map. What the PFC3BXL or PFC3B does next depends on whether it is swapping
labels, imposing a new label, or popping a label:
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Classification for MPLS-to-MPLS PFC3BXL or PFC3B Mode MPLS QoS
PFC3BXL or PFC3B mode MPLS QoS at the ingress to P1 or P2 supports the following:
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PFC3BXL or PFC3B mode MPLS QoS at the egress of P1 or P2 supports matching with the mpls
experimental topmost command.
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
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Swapping labels—When swapping labels, the PFC3BXL or PFC3B preserves the EXP value in the
received topmost label and copies it to the EXP value in the outgoing topmost label. The PFC3BXL
or PFC3B assigns the egress CoS using the internal DSCP-to-CoS global map. If the DSCP global
maps are consistent, then the egress CoS is based on the EXP in the outgoing topmost label.
The PFC3BXL or PFC3B can mark down out-of-profile traffic using the police command's exceed
and violate actions. It does not mark in-profile traffic, so the conform action must be transmitted
and the set command cannot be used. If the PFC3BXL or PFC3B is performing a markdown, it uses
the internal DSCP as an index into the internal DSCP markdown map. The PFC3BXL or PFC3B
maps the result of the internal DSCP markdown to an EXP value using the internal DSCP-to-EXP
global map. The PFC3BXL or PFC3B rewrites the new EXP value to the topmost outgoing label and
does not copy the new EXP value to the other labels in the stack. The PFC3BXL or PFC3B assigns
the egress CoS using the internal DSCP-to-CoS global map. If the DSCP maps are consistent, then
the egress CoS is based on the EXP value in the topmost outgoing label.
Imposing an additional label—When imposing a new label onto an existing label stack, the
PFC3BXL or PFC3B maps the internal DSCP to the EXP value in the imposed label using the
internal DSCP-to-EXP map. It then copies the EXP value in the imposed label to the underlying
swapped label. The PFC3BXL or PFC3B assigns the egress CoS using the internal DSCP-to-CoS
global map. If the DSCP maps are consistent, the egress CoS is based on the EXP value in the
imposed label.
The PFC3BXL or PFC3B can mark in-profile and mark down out-of-profile traffic. After it marks
the internal DSCP, the PFC3BXL or PFC3B uses the internal DSCP-to-EXP global map to map the
internal DSCP to the EXP value in the newly imposed label. The PFC3BXL or PFC3B then copies
the EXP in the imposed label to the underlying swapped label. The PFC3BXL or PFC3B assigns the
egress CoS using the internal DSCP-to-CoS global map. Therefore, the egress CoS is based on the
EXP in the imposed label.
Popping a label—When popping a label from a multi-label stack, the PFC3BXL or PFC3B preserves
the EXP value in the exposed label. The PFC3BXL or PFC3B assigns the egress CoS using the
internal DSCP-to-CoS global map. If the DSCP maps are consistent, then the egress CoS is based
on the EXP value in the popped label.
If EXP propagation is configured for the egress interface, the PFC3BXL or PFC3B maps the internal
DSCP to the EXP value in the exposed label using the DSCP-to-EXP global map. The PFC3BXL or
PFC3B assigns the egress CoS using the internal DSCP-to-CoS global map. If the DSCP maps are
consistent, the egress CoS is based on the EXP value in the exposed label.
Matching with the mpls experimental topmost command
The set mpls experimental imposition, police, and police with set imposition commands
Chapter 42 Configuring PFC3BXL or PFC3B Mode MPLS QoS
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