Cisco 7604 Configuration Manual page 606

Understanding How PFC QoS Works
3.
These figures provide more detail about the relationship between QoS and the router components:
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•
•
Figure 41-2
Figure 41-2 Traffic Flow and PFC QoS Features with PFC3
FlexWAN traffic
enters switch
LAN traffic
enters switch
OSM traffic
enters switch
CoS = 0 for all ATM and POS traffic (not configurable)
Figure 41-2
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•
•
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Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
41-4
—Police the traffic
Egress Ethernet LAN port QoS features:
– Layer 3 DSCP marking with the final internal DSCP (always with PFC2, optionally with PFC3)
Layer 2 CoS marking mapped from the final internal DSCP
–
Layer 2 CoS-based and Layer 3 DSCP-based congestion avoidance. (Layer 3
–
queue mapping is available only on WS-X6708-10GE ports.)
Figure 41-2, Traffic Flow and PFC QoS Features with PFC3
Figure 41-3, Traffic Flow and PFC QoS Features with PFC2
Figure 41-4, PFC QoS Features and Component Overview
shows traffic flow and PFC QoS features with a PFC3.
FlexWAN
ingress port and
QoS features
LAN ingress
Ingress
port and
PFC3
QoS features
QoS
OSM ingress
port and
QoS freatures
shows how traffic flows through the PFC QoS features with PFC3:
Traffic can enter on any type of port and exit on any type of port.
DFCs implement PFC QoS locally on switching modules.
For FlexWAN module traffic:
Ingress FlexWAN QoS features can be applied to FlexWAN ingress traffic.
–
Ingress FlexWAN traffic can be Layer 3-switched by the PFC3 or routed in software by the MSFC.
–
Egress PFC QoS is not applied to FlexWAN ingress traffic.
–
Egress FlexWAN QoS can be applied to FlexWAN egress traffic.
–
For LAN-port traffic:
Ingress LAN-port QoS features can be applied to LAN-port ingress traffic.
–
– Ingress PFC QoS can be applied to LAN-port ingress traffic.
Ingress LAN-port traffic can be Layer-2 or Layer-3 switched by the PFC3 or routed in software
–
by the MSFC.
Multilayer Switch
Feature Card
(MSFC)
Egress
PFC3
PFC3
Layer 2 or 3
QoS
switching
Chapter 41 Configuring PFC QoS
DSCP-based
FlexWAN
Transmit
egress port and
FlexWAN traffic
QoS features
CoS = IP precedence for all traffic
(not configurable)
LAN egress
Transmit
port and
LAN traffic
QoS features
OSM egress
Transmit
port and
OSM traffic
QoS freatures
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