11-5
Cisco 10000 Series Router Quality of Service Configuration Guide
OL-7433-09
Chapter 11 Managing Packet Queue Congestion
Queue Limit
Syntax Description
queue-limit Command History
Default Behavior for the queue-limit Command
The following describes the default behavior of the
queue-limit
command for class queues with and
without weighted random early detection (WRED):
•
Class queues with weighted random early detection (WRED)—The router uses the default queue
limit of two times the largest WRED maximum threshold value, rounded to the nearest power of 2.
Note
For Cisco IOS Release 12.2(15)BX and Release 12.2(16)BX using the PRE2, and for Cisco IOS
Release 12.2(31)SB2 and later releases using the PRE3, the router does not round the value to
the nearest power of 2.
•
Priority queues and class queues without WRED—The router has buffers for up to 50 milliseconds
of 256-byte packets at line rate, but not less than 32 packets.
number-of-packets
For PRE1,
number-of-packets
is a number from 32 to 16384; the number
must be a power of 2. If the number you specify is not a power of 2, the
router converts the number to the nearest power of 2 value.
For Cisco IOS Release 12.2(15)BX and Release 12.2(16)BX using the
PRE2,
number-of-packets
is a number from 32 to 16384. The number does
not need to be a power of 2.
For Cisco IOS Release 12.3(7)XI and later releases using the PRE2, if the
interface speed is less than 500 MB,
number-of-packets
is a number from 8
to 4096; the number must be a power of 2. If the interface speed is greater
than 500 MB,
number-of-packets
is a number from 128 to 64000 and must
be a power of 2. If it is not, the router converts the number to the nearest
power of 2 value.
For Cisco IOS Release 12.2(31)SB2 and later releases using the PRE3,
number-of-packets
is a number from 1 to 32,767. The number does not need
to be a power of 2.
Cisco IOS Release
Description
Release 12.0(17)SL
The
queue-limit
command was introduced on the PRE1.
Release 12.0(25)SX
This command was enhanced to allow you to simultaneously configure
both the
queue-limit
and
random-detect
commands in the same class of
a policy map.
Release 12.2(16)BX
This command was introduced on the PRE2.
Release 12.3(7)XI
This command was enhanced on the PRE2 to allow you to simultaneously
configure both the
queue-limit
and
random-detect
commands in the
same class of a policy map.
Release 12.2(28)SB
This command was integrated in Cisco IOS Release 12.2(28)SB for the
PRE2.
Release 12.2(31)SB2
This command was introduced on the PRE3.
