Cisco CRS Command Reference Manual page 78

queue-limit
Release
Release 3.3.0
Release 3.6.0
Release 3.9.2
Usage Guidelines
To use this command, you must be in a user group associated with a task group that includes appropriate task
IDs. If the user group assignment is preventing you from using a command, contact your AAA administrator
for assistance.
Packets satisfying the match criteria for a class accumulate in the queue reserved for the class until they are
serviced by the scheduling mechanism. The queue-limit command defines the maximum threshold for a
class. When that threshold is reached, enqueued packets to the class queue result in tail drop (packet drop).
Tail drop is a congestion avoidance technique that drops packets when an output queue is full, until congestion
is eliminated.
Use the show qos interface command to display the queue limit and other policer values.
Queue Limit Default Values
The following default values are used when queue-limit is not configured in the class:
• If QoS is not configured:
• If QoS is configured and Weighted Random Early Detection (WRED) is not configured:
• If QoS is configured and WRED is configured:
Cisco IOS XR Modular Quality of Service Command Reference for the Cisco CRS Router, Release 4.0
72
Modification
Command name changed from queue-limit bytes to queue-limit .
Command order modified to place value before units.
The units argument was added.
Default units was changed from bytes to packets.
The value range of 1 to 1000000000 has changed to 1 to 4294967295.
The default threshold for tail drop changed from 200 milliseconds to 100
milliseconds.
The cells unit was added.
◦ The queue limit is 100 ms at the interface rate.
◦ Queue limit is 100 ms at the guaranteed service rate of the queue for non-priority queues.
◦ Queue limit is 10 ms at the interface rate for Level 1 priority classes.
◦ Queue limit is 10 ms at parent guaranteed service rate for Level 2 priority classes.
◦ Queue limit is two times the WRED maximum threshold. The maximum threshold can be an
explicitly configured value or an implicit 100 ms.
◦ If more than one WRED profile is configured in the class, the maximum threshold is the maximum
for all profiles.
◦ When the queue-limit is configured in time units, the guaranteed service rate is used to compute
the queue limit.
Quality of Service Commands on the Cisco IOS XR Software
OL-23235-03