Wred Drop Profiles - Cisco 10000 Series Configuration Manual

Controlling Congestion Using Weighted Random Early Detection
Table 11-4
Command
random-detect dscp-based
max-thresh-value
mark-probability-denominator-value
random-detect prec-based
max-thresh-value
mark-probability-denominator-value
random-detect discard-class-based
min-thresh-value max-thresh-value
mark-probability-denominator-value
random-detect atm-clp-based
max-thresh-value
mark-probability-denominator-value
random-detect cos
max-thresh-value mark-probability-denominator
The minimum threshold indicates the minimum number of packets allowed in the queue. When the
average queue length reaches the minimum threshold, WRED randomly drops some packets with the
specified DSCP, IP precedence, or discard-class value. Valid minimum threshold values are from 1 to
16,384. This option is not available on the PRE3 for the random detect discard-class command.
The maximum threshold indicates the maximum number of packets allowed in the queue. When the
average queue length exceeds the maximum threshold, WRED drops all packets with the specified
DSCP, IP precedence, or discard-class value. Valid maximum threshold values are from the value of the
min-threshold to 1.
The maximum probability denominator is the drop rate. It specifies the denominator for the fraction of
packets dropped when the average queue depth is at the maximum threshold. For example, if the
denominator is 512, 1 out of every 512 packets is dropped when the average queue is at the maximum
threshold. Valid values are from 1 to 65,535. The default value is 10.
For information about the behavior of the random-detect command on the various PRE processor cards,
see the
on page

WRED Drop Profiles

A WRED drop profile specifies DSCP, IP precedence, discard-class, or ATM CLP values, which WRED
uses to determine the drop probability of packets.
Table 11-5
depends on the PRE installed in the router as the following describes:
•
Cisco 10000 Series Router Quality of Service Configuration Guide
11-14
WRED Drop Mode Commands
min-thresh-value
min-thresh-value
cos-value min-thres-value
"WRED Drop Profiles" section on page 11-14
11-17.
lists the commands used to configure a packet drop policy. The behavior of these commands
On the PRE2, the random-detect command specifies the default profile for the queue.
Description
Drops packets based on a DSCP value. This
option is available on the PRE2, PRE3, and
PRE4.
Drops packets based on an IP precedence
value. This option is available on the PRE2,
PRE3, and PRE4.
Drops packets based on a discard-class value.
This option is available on the PRE2, PRE3,
and PRE4.
Note
Drops packets based on an ATM cell loss
min-thresh-value
priority (CLP) value. This option is available
on the PRE2, PRE3, and PRE4.
Drops packets based on the CoS bit value of
the packet. This option is available on the
PRE3, and PRE4.
and the
Chapter 11 Managing Packet Queue Congestion
The min-thresh-value option is not
available on the PRE3 for this
command.
"WRED Aggregate Drop Profiles" section
OL-7433-09