41-12
Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4
78-13315-02
Chapter 41 Configuring QoS
Understanding How QoS Works
1q4t
ports have this default drop-threshold configuration:
•
Using receive-queue drop threshold 1, the switch drops incoming frames with CoS 0 or 1 when the
receive-queue buffer is 50 percent or more full.
•
Using receive-queue drop threshold 2, the switch drops incoming frames with CoS 2 or 3 when the
receive-queue buffer is 60 percent or more full.
•
Using receive-queue drop threshold 3, the switch drops incoming frames with CoS 4 or 5 when the
receive-queue buffer is 80 percent or more full.
•
Using receive-queue drop threshold 4, the switch drops incoming frames with CoS 6 or 7 when the
receive-queue buffer is 100 percent full.
1p1q4t
ports have this default drop-threshold configuration:
•
Frames with CoS 0, 1, 2, 3, 4, 6, or 7 go to the standard receive queue:
–
Using standard receive-queue drop threshold 1, the switch drops incoming frames with CoS 0
or 1 when the receive-queue buffer is 50 percent or more full.
–
Using standard receive-queue drop threshold 2, the switch drops incoming frames with CoS 2
or 3 when the receive-queue buffer is 60 percent or more full.
–
Using standard receive-queue drop threshold 3, the switch drops incoming frames with CoS 4
when the receive-queue buffer is 80 percent or more full.
–
Using standard receive-queue drop threshold 4, the switch drops incoming frames with CoS 6
or 7 when the receive-queue buffer is 100 percent full.
•
Frames with CoS 5 go to the strict-priority receive queue (queue 2), where the switch drops
incoming frames only when the strict-priority receive-queue buffer is 100 percent full.
1p1q0t
ports have this default drop-threshold configuration:
•
Frames with CoS 0, 1, 2, 3, 4, 6, or 7 go to the standard receive queue. The switch drops incoming
frames when the receive-queue buffer is 100 percent full.
•
Frames with CoS 5 go to the strict-priority receive queue (queue 2), where the switch drops
incoming frames only when the strict-priority receive-queue buffer is 100 percent full.
Note
The explanations in this section use default values. You can configure many of the parameters (for
more information, see the
“Configuring QoS” section on page 41-30
). All ports of the same type use
the same drop-threshold configuration.
Figure 41-8
shows the drop thresholds for a
1q4t
port. Drop thresholds in other configurations function
similarly.
