Administrator Guide

ecn Cause explicit congestion notification (ECN) to be used to indicate network
congestion, rather than dropping packets, queues-list Enter the queue numbers,
either as individual queue numbers separated by commas or as an inclusive list
separating the starting and ending queue numbers with a hyphen
backplane Specify that the ECN marking configured for each queue applies to backplane ports
Default By default, ECN marking is disabled on all queues.
Command Modes CONFIGURATION mode
Command
History
Version 9.6.0.0 Added support for backplane changes in the Z9000 platform.
Version 9.3.0.0 Introduced on the Z9000 platform.
Usage
Information
You can add or remove ECN marking configuration on a list of queues on all backplane ports. All of the
configured attributes apply to all the backplane ports and are for each queue. You can configure all the
data queues. For Z9000, you can configure queues 0-3. For S6000, you can configure queues 0-7. By
default, ECN marking is disabled on all queues. When you enable wred-ecn, and the number of packets in
the queue is below the minimum threshold, packets are transmitted per the usual WRED treatment. When
you enable wred-ecn, and the number of packets in the queue is between the minimum threshold and the
maximum threshold, one of the following two scenarios can occur:
● If the transmission endpoints are ECN-capable and traffic is congested, and the WRED algorithm
determines that the packet should have been dropped based on the drop probability, the packet is
transmitted and marked so the routers know the system is congested and can slow transmission rates.
● If neither endpoint is ECN-capable, the packet may be dropped based on the WRED drop probability.
This behavior is the identical treatment that a packet receives when WRED is enabled without ECN
configured on the router.
When you enable wred-ecn, and the number of packets in the queue is above the maximum threshold,
packets are dropped based on the drop probability. This behavior is the identical treatment a packet
receives when WRED is enabled without ECN configured on the router.
Example
Dellconf) #service-class wred ecn backplane 0,3-5,7
DSCP Color Map Commands
The DSCP color map allows you to set the number of specific DSCP values to yellow or red. Traffic marked as yellow delivers
traffic to the egress queue which will either transmit the packet if it has available bandwidth or drop the packet due to no ability
to send. Traffic marked as red (high drop precedence) is dropped.
dscp
Sets the number of specific DSCP values for a color map profile to yellow or red.
Syntax
dscp {yellow | red} [list-dscp-values]
To remove a color policy map profile, use the no dscp {yellow | red} [dscp-list] command.
Parameters
Yellow Enter the yellow keyword. Traffic marked as yellow delivers traffic to the egress
queue which either transmits the packet if it has available bandwidth or drops the
packet due to no ability to send.
Red Enter the red keyword. Traffic marked as red is dropped.
dscp-list Enter a list of IP DSCP values. The dscp-list parameter specifies the full list of IP
DSCP value(s) for the specified color. Each DSCP value in a list is separate values
Quality of Service (QoS) 1037