Feature History For Weighted Random Early Detection - Cisco 10000 Series Configuration Manual

Controlling Congestion Using Weighted Random Early Detection
•
You can also configure WRED to ignore the IP precedence, DSCP, or discard-class when making drop
decisions. As a result, the router implements non-weighted random early detection (RED) behavior when
deciding which packets to drop.
The PRE2 uses sampled RED and the PRE3 uses per-packet RED.
Note

Feature History for Weighted Random Early Detection

Cisco IOS Release
Release 12.0(17)SL
Release 12.0(22)S
Release 12.0(25)SX
Release 12.2(16)BX
Release 12.3(7)XI
Release 12.2(28)SB
Release 12.2(31)SB2
Release 12.2(33)SB
Cisco 10000 Series Router Quality of Service Configuration Guide
11-12
Frame Relay DE WRED—The discard eligibility (DE) bit in the address field of a frame relay frame
is used to prioritize the discarding of frames in congested frame relay networks. The frame relay DE
bit has only one bit and therefore only has two settings, 0 or 1. If congestion occurs in a frame relay
network, frames with the DE bit set at 1 are discarded before frames with the DE bit set at 0.
Therefore, important traffic should have the DE bit set at 0 while less important traffic should be
forwarded with the DE bit set at 1.
Description
The weighted random early detection feature was
introduced on the router.
This feature was enhanced to allow you to configure
WRED based on a differentiated services code point
(DSCP).
This feature was enhanced to allow you to simultaneously
configure the random-detect command and the
queue-limit for the same class queue.
This feature was introduced on the PRE2 and uses sampled
RED.
This feature was enhanced on the PRE2 to:
Enable the configuration of eight unique drop
•
precedence levels for one queue instead of four levels
Allow the simultaneous configuration of both the
•
random-detect and queue-limit commands for a
class queue
Support discard-class-based WRED
•
Maintain separate WRED drop statistics for each IP
•
precedence, DSCP value, and discard-class
This feature was integrated in Cisco IOS
Release 12.2(28)SB for the PRE2.
This feature was introduced on the PRE3 and uses
per-packet RED. This feature is DiffServ-compliant on the
PRE3.
This feature was enhanced to support ATM cell loss
priority-based WRED on the PRE2, PRE3 and PRE4.
Chapter 11 Managing Packet Queue Congestion
Required PRE
PRE1
PRE1
PRE1
PRE2
PRE2
PRE2
PRE3
PRE2, PRE3,
PRE4
OL-7433-09