This document describes the configurable Cisco NX-OS Quality of Service (QoS) features. You use the QoS features to provide the most desirable flow of traffic through a network. QoS allows you to classify the network traffic, prioritize the traffic flow, and provide congestion avoidance. The control of traffic is based on the fields in the packets that flow through the system. You use the Modular QoS CLI (MQC) to create the traffic classes and policies of the QoS features.

QoS features are applied using QoS policies and queuing policies, as follows:

• QoS policies include classification and marking features.

• Queuing policies use the queuing and scheduling features at egress. At ingress, they are used to configure buffer threshold and priority group mapping.

• Network QoS policies include configuring maximum transmission unit (MTU), pause no-drop, and queue-limit. It is also used to configure explicit congestion notification (ECN) and weighted random early detection (WRED).

• Priority flow control.