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Cisco 7600 Series Router Cisco IOS Software Configuration Guide—12.1E
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Chapter 32 Configuring PFC QoS
Understanding How PFC QoS Works
Note The explanations in this section use default values. You can configure many of the parameters (see the
“Configuring PFC QoS” section on page 32-33). All LAN ports of the same type use the same
drop-threshold configuration.
Figure 32-9 illustrates the drop thresholds for a 1q4t ingress LAN port. Drop thresholds in other
configurations function similarly.
Figure 32-9 Receive Queue Drop Thresholds
PFC Marking and Policing
Note • To mark untrusted traffic without policing in Release 12.1(12c)E1 and later releases, use the set ip
dscp or set ip precedence policy map class commands (see the “Configuring Policy Map Class
Actions” section on page 32-44).
• To mark untrusted traffic without policing in earlier releases, create a policer that only marks and
does not police.
These sections describe PFC marking and policing:
• Internal DSCP Values, page 32-17
• Policy Maps, page 32-18
C
o
S
0
a
n
d
1
C
o
S
2
a
n
d
3
C
o
S
4
a
n
d
5
C
o
S
6
a
n
d
7
Traffic is dropped
Drop threshold 4: 100%
Drop threshold 3: 80%
Drop threshold 2: 60%
Drop threshold 1: 50%
Available for
traffic with any
CoS value
Reserved for
CoS 6 and 7
Reserved for
CoS 4 and higher
Reserved for
CoS 2 and higher
Receive queue
(Default values shown)
100% available for CoS 6 and 7
80% available for CoS 4 and 5
60% available for CoS 2 and 3
50% available for CoS 0 and 1
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