queue-limit
To specify or modify the maximum number of packets the queue can hold for a class policy configured in a
policy map for each port, use the
queue-limit
command in policy map class configuration mode. To remove
the queue packet limit from a class, use the
no
form of this command.
queue-limit value
[
unit
]
| percent <1-100>
no queue-limit
Syntax Description
Maximum threshold for tail drop in bytes. Range is from 1 to 4294967295.
value
(Optional) Units for the queue limit value. Values can be:
•
bytes
—bytes
•
kbytes
—kilobytes
•
mbytes
—megabytes
•
ms
—milliseconds
•
packets
—packets (default)
•
us
—microseconds
When the specified
units
is packets, packets are assumed to be 256 bytes in size.
Note
unit
(Optional) Allows you to specify queue limit thresholds as a percentage of the total buffer limit for
each port. This makes your provisioning model simpler and makes it easier for you to adjust the
queue burst limit, irrespective of the queue’s service rate. The calculation is based on the assumption
that a port takes 40 milli-seconds of buffering at port-rate. This option was introduced in Release
6.1.2.
percent
Command Default
The default value is 10 milliseconds for all queues including the high-priority queues.
Command Modes
Policy map class configuration
Command History
Modification
Release
This command was introduced.
Release 6.0
Usage Guidelines
When configuring the
queue-limit
command, you must configure one of the following commands:
priority
,
shape average
,
bandwidth
or
bandwidth remaining
, except for the default class. The default value is 10
milliseconds for all queues including the high-priority queues.
The
queue-limit
command is supported only in the egress direction.
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).
Modular QoS Command Reference for Cisco NCS 5500 Series and Cisco NCS 540 Series Routers
68
Congestion Avoidance Commands
queue-limit