Modular QoS Deployment Scenarios on Cisco ASR 9000 Series Routers
MPLS QoS
QC-177
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide
OL-23108-02
Note that the egress LSR still uses the marking that was used by intermediate LSRs. However, the egress
LSR has to remove all labels imposed on the original packet. In order to preserve this marking carried
in the labels, the edge LSR keeps an internal copy of the marking before removing the labels. This
internal copy is used to classify the packet on the outbound interface (facing the CE) once the labels are
removed. This is usually achieved using the set qos-group and match qos-group commands.
Figure 4Pipe Mode
MPLS Short Pipe Mode
The short pipe mode (shown in Figure 5), is a slight variation of the pipe mode. The only difference is
that the egress LSR uses the original packet marking instead of using the marking used by the
intermediate LSRs.
Figure 5 Short Pipe Mode
Uniform, Pipe, Short Pipe Modes: Ingress PE Example
This example shows how to implement the MPLS DiffServ and demonstrates the configuration needed
on the ingress PE. Only precedence 4 is being matched. Precedence 4 is mapped to EXP bits value 4 by
the policer, unless the bandwidth is exceeded, in which case the EXP bits are recolored to the value 2.
The egress interface configuration is not needed for the MPLS DiffServ uniform model, but it is added
to show how to perform QoS on the EXP bits.
279791
DSCP = 5 DSCP = 5DSCP = 5
EXP = 3
EXP = 3
DSCP = 5
EXP = 3
EXP = 3
DSCP = 5
EXP = 3
Ingress
PE
PP
Egress
PE
LSP
EXP Bits Set According to
Service Provider’s Policy
Scheduling and Discard
Behavior Based on EXP
279790
DSCP = 5 DSCP = 5DSCP = 5
EXP = 3
EXP = 3
DSCP = 5
EXP = 3
EXP = 3
DSCP = 5
EXP = 3
Ingress
PE
PP
Egress
PE
LSP
EXP Bits Set According to
Service Provider’s Policy
Scheduling and Discard
Behavior Based on DSCP
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