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Catalyst 6000 Family Software Configuration Guide—Releases 6.3 and 6.4
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Chapter 41 Configuring QoS
Understanding How QoS Works
Figure 41-6 Ethernet Egress Port Scheduling, Congestion Avoidance, and Marking
49380
2q2t port
(tail-drop thresholds)
High priority
standard queue
100% for CoS 6 and 7
80% for CoS 4 and 5
Low priority
standard queue
100% for CoS 2 and 3
80% for CoS 0 and 1
Write CoS
into
frame
ISL or
802.1Q?
IP traffic
from PFC?
Write ToS
byte into
packet
No
No
Yes
Yes
Ethernet egress port scheduling, congestion avoidance, and marking
Transmit
frame
From switching
engine or MSFC
1p2q2t port
Strict priority queue
100% for CoS 5
High priority
standard queue
(WRED-drop thresholds)
70%:100% for CoS 6 and 7
40%:70% for CoS 4
Low priority
standard queue
(WRED-drop thresholds)
70%:100% for CoS 2 and 3
40%:70% for CoS 0 and 1
1p3q1t port
(Default values shown)
Strict priority queue
100% for CoS 5
standard queues
(WRED-drop or
tail-drop thresholds)
High priority
100% for CoS 6 and 7
Medium priority
100% for CoS 2, 3 and 4
Low priority
100% for CoS 0 and 1