Addendum

Command
Modes
CONFIGURATION mode
Command
History
Version 9.3.0.0 Introduced on the S6000 and Z9000 platforms
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. 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 three
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.
• If the network is experiencing congestion, the packet is transmitted. No further
marking is required. 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 0, 3-5, 7 backplane
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.
Z9000
Syntax
[No] service-class wred ecn queues-list {backplane}
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
Quality of Service (QoS)
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