Administrator Guide

service-class wred ecn
Create a service class and assign ECN marking for different queues on backplane ports to the service
class. This functionality can be configured on the Z9000 platforms.
Syntax
[No] service-class wred ecn {backplane} queues-list
Parameters
service-class Define the mapping between the service class and policy-
based QoS or routing
wred Associate WRED with ECN to mark packets instead of
dropping them
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.
Quality of Service (QoS)
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