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Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
OL-4266-08
Chapter 42 Configuring PFC QoS
Understanding How PFCQoS Works
Figure 42-6 shows how traffic flows through the QoS features on the PFC and DFCs.
Figure 42-6 QoS Features on the PFC and DFCs
Note The DSCP transparency feature makes writing the egress DSCP value into the Layer 3 ToS byte optional.
For trust CoS traffic:
For trust IP precedence traffic:
For trust DSCP traffic:
For untrusted traffic or
for any traffic if ignore
port trust is configured
When ignore port trust is not configured
When ignore port trust is configured,
received DSCP (if any) is initial internal
DSCP, otherwise port CoS is mapped
to initial internal DSCP
Received IP
Precedence
Map
Map
Map
154644
Policer
Marker
(Optional)
Policy map
Initial
Internal
DSCP
Final
Internal
DSCP
Egress
DSCP
Egress
DSCP
Mutation
(only on PFC3)
Received
DSCP
CoS
(Received or Port)
Map
Policer
Marker
(Optional)
Policy map
Policer
Marker
(Optional;
only
with PFC 3)
Policy map
Initial
Internal
DSCP
Policer
Marker
(Optional)
Policy map
Initial
Internal
DSCP
Policer
Marker
(Optional)
Policy map
Traffic Forwarding
MSFC routing
or
PFC Layer 3
switching
or
PFC Layer 2
switching
Egress CoS
(LAN ports only)
Ingress PFC QoS
Egress PFC QoS
Initial Internal DSCP=0