Administrator Guide

Displaying WRED Drop Statistics
To display WRED drop statistics, use the following command.
● Display the number of packets that the WRED profile drops.
EXEC Privilege mode
show qos statistics
The following shows the show qos statistics output.
Dell# show qos statitstics wred-profile
WInterface Te 0/49
Drop-statistic Dropped Pkts
Green 51624
Yellow 51300
Out of Profile 0
The following shows the show qos statistics output on the port extender.
DELL#show qos statistics peGigE 0/1/1
Interface peGigE 0/1/1
Queue# Matched Pkts
0 0
1 0
2 0
3 0
4 0
5 0
6 0
7 0
DELL#show qos statistics wred-profile peGigE 0/1/1
Interface peGigE 0/1/1
Drop-statistic Dropped Pkts
Green 0
Yellow 0
Out of Profile 0
Displaying egress-queue Statistics
To display the number of transmitted and dropped packets on the egress queues of a WRED-configured interface, use the
following command.
● Display the number of packets and number of bytes on the egress-queue profile.
EXEC Privilege mode
show qos statistics egress-queue
Explicit Congestion Notification
Explicit Congestion Notification (ECN) enhances and extends WRED functionality by marking packets for later transmission
instead of dropping them when a threshold value is exceeded. Use ECN for WRED to reduce the packet transmission rate in a
congested, heavily-loaded network.
While WRED drops packets to indicate congestion, ECN marks packets instead of dropping them when the average queue
length exceeds the threshold value. ECN provides an improved method for congestion avoidance by allowing the switch to mark
packets for later transmission rather than dropping them from a queue.
ECN uses a two-bit ECN-specific field in the IP header to indicate if a packet is ECN-capable, if the endpoints in the transport
protocol are ECN-capable, and if there is network congestion.
When ECN for WRED is enabled, if the queue length is between the minimum threshold and the maximum threshold, one of the
following actions is taken:
798
Quality of Service (QoS)