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Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
OL-23826-09
Chapter 24 Configuring QoS
QoS Treatment for Performance-Monitoring Protocols
You can also use marking to assign traffic to a QoS group within the router. This QoS group is an internal
label that does not modify the packet, but it can be used to identify the traffic type when configuring
egress queuing on the network port.
You can specify and mark traffic CPU-generated traffic by using these global configuration commands:
cpu traffic qos cos {cos_value | cos [table-map table-map-name] | dscp [table-map table-map-name]|
precedence [table-map table-map-name]}
You can mark a QoS group by configuring an explicit value or by using the table-map keyword. Table
maps list specific traffic attributes and map (or convert) them to another attribute. A table map
establishes a to-from relationship for the attribute and defines the change to be made:
• Marking CoS by using the CoS, or the IP-DSCP, or the IP precedence of IP CPU-packets
• Marking CoS by using the CoS of non-IP CPU-packets.
• Marking IP DSCP by using the CoS, or the IP-DSCP, or the IP precedence of the CPU-packet
• Marking IP precedence by using the CoS, or the IP-DSCP, or the IP precedence of the CPU-packet
You can configure either IP-DSCP or IP precedence marking.
You can also simultaneously configure marking actions to modify CoS, IP-DSCP or IP precedence, and
QoS group.
The cpu traffic qos command specifies the traffic to which it applies: all CPU traffic, only CPU IP
traffic, or only CPU non-IP traffic. All other traffic retains its QoS markings. This feature does not affect
CFM traffic (including Layer 2 IP SLA probes using CFM).
QoS Queuing for CPU-Generated Traffic
You can use the QoS markings established for the CPU-generated traffic by the cpu traffic qos global
configuration command as packet identifiers in the class-map of an output policy-map to map CPU
traffic to class-queues in the output policy-map on the egress port. You can then use output policy-maps
on the egress port to configure queuing and scheduling for traffic leaving the router from that port.
If you want to map all CPU-generated traffic to a single class in the output policy-maps without changing
the CoS, IP DSCP, or IP-precedence packet markings, you can use QoS groups for marking
CPU-generated traffic.
If you want to map all CPU-generated traffic to classes in the output policy maps based on the CoS
without changing the CoS packet markings, you can use the table map:
• Configure CoS marking by using CoS as the map from value without a table map.
• Configure CoS marking using CoS as the map from value with a table map, using only the default
and copy keywords.
For details about table maps, see the “Table Maps” section on page 24-13.
Using the cpu traffic qos global configuration command with table mapping, you can configure multiple
marking and queuing policies to work together or independently. You can queue native VLAN traffic
based on the CoS markings configured using the cpu traffic qos global configuration command.
The cpu traffic qos command specifies the traffic to which it applies: all CPU traffic, only CPU-IP
traffic, or only CPU non-IP traffic. All other traffic is statically mapped to a CPU-default queue on the
egress port. All CFM traffic (including Layer 2 IP SLA probes using CFM) is mapped to classes in the
output policy map, and queued based on their CoS value.