41-94
Cisco 7600 Series Router Cisco IOS Software Configuration Guide, Release 12.2SX
OL-4266-08
Chapter 41 Configuring PFC QoS
Configuring PFC QoS
• Configuring a WRED-Drop and Tail-Drop Transmit Queue, page 41-96
• Configuring 1q4t/2q2t Tail-Drop Threshold Percentages, page 41-98
Note • Enter the show queueing interface {ethernet | fastethernet | gigabitethernet |
tengigabitethernet} slot/port | include type command to see the queue structure of a port.
• 1p1q0t ports have no configurable thresholds.
• 1p3q1t (transmit), 1p2q1t (transmit), and 1p1q8t (receive) ports also have nonconfigurable
tail-drop thresholds.
When configuring thresholds, note the following information:
• Queue number 1 is the lowest-priority standard queue.
• Higher-numbered queues are higher priority standard queues.
• Receive-queue parameters can be configured only on trusted ports.
• When configuring minimum and maximum threshold values, you cannot configure minimum values
to be larger than maximumvalues.
When you configure multiple-threshold standard queues, note the following information:
• The first percentage that you enter sets the lowest-priority threshold.
• The second percentage that you enter sets the next highest-priority threshold.
• The last percentage that you enter sets the highest-priority threshold.
• The percentages range from 1 to 100. A value of 10 indicates a threshold when the buffer is
10-percent full.
• Always set highest-numbered threshold to 100 percent.
When configuring the WRED-drop thresholds, note the following information:
• Each WRED-drop threshold has a low-WRED and a high-WRED value.
• Low-WRED and high-WRED values are a percentage of the queue capacity (the range is from 1
to 100).
• The low-WRED value is the traffic level under which no traffic is dropped. The low-WRED value
must be lower than the high-WRED value.
• The high-WRED value is the traffic level above which all traffic is dropped.
• Traffic in the queue between the low- and high-WRED values has an increasing chance of being
dropped as the queue fills.
Configuring a Tail-Drop Receive Queue
These port types have only tail-drop thresholds in their receive-queues:
• 1q2t
• 1p1q4t
• 2q8t
• 1q8t
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