Cisco WS-SUP32-GE-3B - Supervisor Engine 32 Software Configuration Manual page 550

Understanding How PFC QoS Works
Each policy map can contain multiple policy-map classes. You can configure a separate policy-map class
for each type of traffic handled by the interface. There are two ways to configure filtering in policy-map
classes:
•
•
Policy-map classes specify actions with the following optional commands:
•
•
•
Classification and Marking on the PISA
Some traffic is routed in software on the PISA. PFC QoS sends IP traffic to the PISA with the final
internal DSCP values. CoS is equal to IP precedence in all traffic sent from the PISA to egress ports.
Figure 38-7
Catalyst Supervisor Engine 32 PISA Cisco IOS Software Configuration Guide, Release 12.2ZY
38-16
Access control lists (ACLs)
Class-map match commands for IP precedence and DSCP values
Policy-map set commands—For untrusted traffic or if
configured IP precedence or DSCP values as the final internal DSCP value. The
DSCP Values" section on page 38-44
Policy-map class trust commands—PFC QoS applies the policy-map class trust state to matched
ingress traffic, which then uses the trusted value as the basis of its initial internal DSCP value,
instead of the QoS label that was trusted at the port (if any). In a policy map, you can trust CoS,
precedence, or DSCP.
A trust CoS policy map cannot restore received CoS in traffic from untrusted ports. Traffic
Note
from untrusted ports always has the port CoS value.
Aggregate and microflow policers—PFC QoS can use policers to either mark or drop both
conforming and nonconforming traffic.
Marking with PFC3B and PISA
From PFC
Programmable Intelligent Services Accelerator (PISA) marking
ignore port trust
shows the bit values for IP precedence and DSCP.
Write ToS
Yes
IP traffic
byte into
from PFC?
packet
No
Process
traffic
CoS = IP precedence for
all traffic (not configurable)
To egress
port
Chapter 38 Configuring PFC QoS
is enabled, PFC QoS can use
"IP Precedence and
OL-11439-03
IP