Using Qos - Cisco Nexus 7000 Series Configuration Manual

Using QoS

Caution
Before you attempt a downgrade from Cisco NX-OS Release 5.2(x) or newer release to any release prior to
Release 5.2(1), you should clear the QoS MIB and MPLS QoS defaults by using the clear qos mpls-snmp
command. The downgrade might fail if the defaults are not cleared.
Before you downgrade from Cisco NX-OS Release 5.2(x) or 5.1(x) or newer release to Cisco NX-OS Release
5.0(x) or an earlier release, remove all system QoS and QoS policies configured on F-Series I/O modules.
Use the clear qos policies command to remove the defaults for F-Series modules. An internal process failure
can result if the QoS policies are not removed prior to the downgrade.
Using QoS
Traffic is processed based on how you classify it and the policies that you create and apply to traffic classes.
To configure QoS features, you use the following steps:
1. Create traffic classes by classifying the incoming and outgoing packets that match criteria such as IP
address or QoS fields.
2. Create policies by specifying actions to take on the traffic classes, such as limiting, marking, or dropping
packets.
3. Apply policies to a port, port channel, VLAN, or a subinterface.
You use MQC to create the traffic classes and policies of the QoS features.
Note The queuing and scheduling operations of the overall QoS feature are applicable to both IPv4 and IPv6.
Classification
You use classification to partition traffic into classes. You classify the traffic based on the port characteristics
(class of service [CoS] field) or the packet header fields that include IP precedence, Differentiated Services
Code Point (DSCP), Layer 2 to Layer 4 parameters, and the packet length.
The values used to classify traffic are called match criteria. When you define a traffic class, you can specify
multiple match criteria, you can choose to not match on a particular criterion, or you can determine the traffic
class by matching any or all criteria
Traffic that fails to match any class is assigned to a default class of traffic called class-default.
Marking
Marking is the setting of QoS information that is related to a packet. You can set the value of a standard QoS
field IP precedence, DSCP and CoS, and internal labels that can be used in subsequent actions. Marking is
used to identify the traffic type for policing, queuing, and scheduling traffic (only CoS is used in scheduling).
Cisco Nexus 7000 Series NX-OS Quality of Service Configuration Guide
4
Overview