Congestion Avoidance; Congestion Management; Explicit Congestion Notification - Cisco Nexus 9000 Series Configuration Manual

Congestion Avoidance

Note The provided system-defined queuing class maps cannot be modified.
Congestion Avoidance
You can use the following methods to proactively avoid traffic congestion on the device:
• Apply WRED to TCP or non-TCP traffic.
• Apply tail drop to TCP or non-TCP traffic.

Congestion Management

For egress packets, you can choose one of the following congestion management methods:
• Specify a bandwidth that allocates a minimum data rate to a queue.
• Impose a minimum and maximum data rate on a class of traffic so that excess packets are retained in a
• Allocate all data for a class of traffic to a priority queue. The device distributes the remaining bandwidth
For information about configuring congestion management, see the
section.

Explicit Congestion Notification

ECN is an extension to WRED that marks packets instead of dropping them when the average queue length
exceeds a specific threshold value. When configured with the WRED ECN feature, routers and end hosts use
this marking as a signal that the network is congested to slow down sending packets.
Note The ECN feature is not supported on the Cisco Nexus 9508 switch (NX-OS 7.0(3)F3(3)).
Note
Enabling WRED and ECN on a class on a network-qos policy implies that WRED and ECN is enabled for
all ports in the system.
Note On extended output queues (EOQ), the approximate fair-drop (AFD) feature for bandwidth management is
always enabled. The WRED configuration is ignored on EOQs. The configuration for EOQs is based on the
system queuing policy and not on the per port policy.
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queue to shape the output rate.
among the other queues.
Configuring Queuing and Scheduling
Configuring WRED on Egress Queues