Cisco WS-SUP32-GE-3B - Supervisor Engine 32 Software Configuration Manual page 541

Chapter 38 Configuring PFC QoS
Port Trust
In PFC QoS, trust means to accept as valid and use as the basis of the initial
can configure ports as untrusted or you can configure them to trust these QoS values:
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•
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Traffic received through an untrusted port is called untrusted traffic.
Ingress Congestion Avoidance
PFC QoS implements congestion avoidance on
traffic on the basis of its Layer 2 CoS value and assigns it to an ingress queue to provide congestion
avoidance. See the
for more information about ingress congestion avoidance.
PFC QoS Features
These sections describe PFC3Bs as they relate to QoS:
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•
•
Supported Policy Feature Cards
The policy feature card (PFC3B) is a daughter card that resides on the supervisor engine. The PFC3B
provides QoS in addition to other functionality.
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Layer 2 CoS
A port configured to trust CoS is called a trust CoS port.
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Traffic received through a trust CoS port or configured by a policy map to trust CoS is called
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trust CoS traffic.
Not all traffic carries a CoS value. Only ISL, 802.1Q, and 802.1P traffic carries a CoS value.
Note
PFC QoS applies the
untrusted ports, PFC QoS applies the port CoS value to all traffic, overwriting any received
CoS value.
IP precedence
A port configured to trust IP precedence is called a trust IP precedence port.
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Traffic received through a trust IP precedence port or configured by a policy map to trust
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IP precedence is called trust IP precedence traffic.
DSCP
A port configured to trust DSCP is called a trust DSCP port.
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Traffic received through a trust DSCP port or configured by a policy map to trust DSCP is called
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trust DSCP traffic.
"Ingress Classification and Marking at Trust CoS LAN Ports" section on page 38-15
Supported Policy Feature Cards, page 38-7
PFC QoS Feature List and Flowchart, page 38-8
Internal DSCP Values, page 38-10
Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY
port CoS value to any traffic that does not carry a CoS value. On
trust CoS ports. On a trust CoS port, QoS classifies the
Understanding How PFC QoS Works
internal DSCP value. You
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