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Cisco 10000 Series Router Quality of Service Configuration Guide
OL-7433-09
Chapter 7 Marking Traffic
Class-Based Frame Relay DE Bit Marking
Usage Guidelines for the set discard-class Command
You can set the discard-class on the input interface to use as a matching criterion and to affect how
packets are dropped on the output interface. You can use the discard-class with weighted random early
detection (WRED) on the output interface to classify packets and determine packet drop probability.
The router supports the
set discard-class
command only on the PRE2.
Class-Based Frame Relay DE Bit Marking
The Class-Based Frame Relay DE Bit Marking feature provides the ability to prioritize frames in a
Frame Relay network by setting the discard eligibility (DE) bit in the header of Frame Relay frames. As
congestion occurs in the Frame Relay network, frames with the DE bit set are more likely to be dropped,
resulting in improved network performance for higher priority traffic and applications.
This feature supports the classification of inbound Frame Relay traffic based on the DE bit setting and
the marking of the DE bit of outbound Frame Relay traffic. During classification, the router matches the
DE bit of inbound packets to previously configured traffic classes (created using a class map) and
classifies each matching packet as belonging to a specific traffic class.
DE bit marking can occur either as a class-based shaping action or as a class-based policing action. The
modular QoS command-line interface (MQC) commands used to mark the DE bit are the following:
•
set fr-de
command (class-based shaping)
•
set-frde-transmit
command (class-based policing)
The
set-frde-transmit
command is a policing action for conforming traffic and is used with the
police
command. When using the
conforming-action
set-frde-transmit
command, the router sends the frames
through the policer’s token bucket mechanism for processing and sets the DE bit for all frames that
conform to the committed rate.
The PRE3 and PRE4 support Frame Relay DE bit marking across packet fragments.
History for the Class-Based Frame Relay DE Bit Marking Feature
Cisco IOS Release
Description
Required PRE
Release 12.2(31)SB22
This feature was introduced on the PRE3.
PRE2, PRE3
Release 12.2(33)SB
This feature was introduced on the PRE4.
PRE2, PRE3,
PRE4
