Cisco 6500 Series Software Configuration Manual page 413

Chapter 31 Configuring PFC QoS
2q2t Ports
For 2q2t ports, each transmit queue has two tail-drop thresholds that function as follows:
•
•
1p2q2t Ports
1p2q2t ports have a strict-priority queue and two standard transmit queues. The two standard transmit
queues each have two WRED-drop thresholds.
•
•
•
1p3q1t Ports
1p3q1t ports have a strict-priority queue and three standard transmit queues. The standard transmit
queues each have one WRED-drop threshold and one nonconfigurable tail-drop threshold.
•
•
•
•
78-14099-04
Frames with CoS 0, 1, 2, or 3 go to the low-priority transmit queue (queue 1):
Using transmit queue 1, tail-drop threshold 1, the switch drops frames with CoS 0 or 1 when the
–
low-priority transmit-queue buffer is 80 percent full.
Using transmit queue 1, tail-drop threshold 2, the switch drops frames with CoS 2 or 3 when the
–
low-priority transmit-queue buffer is 100 percent full.
Frames with CoS 4, 5, 6, or 7 go to the high-priority transmit queue (queue 2):
Using transmit queue 2, tail-drop threshold 1, the switch drops frames with CoS 4 or 5 when the
–
high-priority transmit-queue buffer is 80 percent full.
Using transmit queue 2, tail-drop threshold 2, the switch drops frames with CoS 6 or 7 when the
–
high-priority transmit-queue buffer is 100 percent full.
Frames with CoS 5 go to the strict-priority transmit queue (queue 3), where the switch drops frames
only when the buffer is 100 percent full.
Frames with CoS 0, 1, 2, or 3 go to the low-priority standard transmit queue (queue 1):
Using standard transmit queue 1, WRED-drop threshold 1, the switch drops frames with CoS 0
–
or 1 when the low-priority transmit-queue buffer is 80 percent full.
Using standard transmit queue 1, WRED-drop threshold 2, the switch drops frames with CoS 2
–
or 3 when the low-priority transmit-queue buffer is 100 percent full.
Frames with CoS 4, 6, or 7 go to the high-priority standard transmit queue (queue 2):
Using standard transmit queue 2, WRED-drop threshold 1, the switch drops frames with CoS 4
–
when the high-priority transmit-queue buffer is 80 percent full.
Using standard transmit queue 2, WRED-drop threshold 2, the switch drops frames with CoS 6
–
or 7 when the high-priority transmit-queue buffer is 100 percent full.
Frames with CoS 5 go to the strict-priority transmit queue (queue 4), where the switch drops frames
only when the buffer is 100 percent full.
Frames with CoS 0 and 1 go to the low-priority standard transmit queue (queue 1).
Frames with CoS 2, 3, or 4 go to the medium-priority standard transmit queue (queue 2).
Frames with CoS 6 or 7 go to the high-priority standard transmit queue (queue 3).
You can configure each standard transmit queue to use both a non-configurable 100 percent
Note
tail-drop threshold and a configurable WRED-drop threshold (see the
Standard-Queue Drop Threshold Percentages" section on page
Catalyst 6500 Series Switch Cisco IOS Software Configuration Guide—Release 12.1 E
Understanding How PFC QoS Works
"Configuring
31-54).
31-23