random-detect discard-class
To configure the Weighted Random Early Detection (WRED) thresholds for packets with a specific discard
class value, use the
random-detect discard-class
command in policy map class configuration mode. To
return the thresholds to the default for the discard class, use the
no
form of this command.
random-detect discard-class discard-value min-threshold
[
units
]
max-threshold
[
units
]
no random-detect discard-class discard-value min-threshold
[
units
]
max-threshold
[
units
]
Syntax Description
Discard class value. The value is 0 or 1.
discard-value
Minimum threshold in number of packets. The value range of this argument is from 0 to
1073741823 in bytes.
min-threshold
Maximum threshold in number of packets. The value range of this argument is from the
value of the
min-threshold
argument to 1073741823. When the average queue length
exceeds the maximum threshold, WRED drops all packets with the specified discard class
value.
max-threshold
(Optional) Units for the threshold values. Values can be:
•
bytes
—bytes
•
gbytes
—gigabytes
•
kbytes
—kilobytes
•
mbytes
—megabytes
•
ms
—milliseconds
•
packets
—packets (default)
•
us
—microseconds
units
Command Default
Default unit for
max-threshold
and
min-threshold
is
packets
.
Command Modes
Policy map class configuration
Command History
Modification
Release
This command was introduced.
Release 6.0
Usage Guidelines
WRED is a congestion avoidance mechanism that slows traffic by randomly dropping packets when congestion
exists. WRED is most useful with protocols like TCP that respond to dropped packets by decreasing the
transmission rate.
When you configure the
random-detect discard-class
command on an interface, packets are given preferential
treatment based on the discard class of the packet.
When the value of the
units
argument is packets, packets are assumed to be 256 bytes in size.
Modular QoS Command Reference for Cisco NCS 5500 Series and Cisco NCS 540 Series Routers
27
QoS Classification Commands
random-detect discard-class