Cisco Nexus 5000 NX-OS User manual

Cisco Nexus 5000 NX-OS Quality of Service Configuration Guide,
Release 5.1(3)N2(1)
First Published: March 13, 2012
Last Modified: February 12, 2013
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Text Part Number: OL-26657-01

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CONTENTS
Preface Preface vii
Audience vii
Document Conventions vii
Documentation Feedback viii
Obtaining Documentation and Submitting a Service Request ix
CHAPTER 1 New and Changed Information 1
New and Changed Information for this Release 1
CHAPTER 2 Overview 3
Information About Quality of Service 3
Modular QoS CLI 3
QoS for Traffic Directed to the CPU 5
CHAPTER 3 Configuring Classification 7
Information About Classification 7
Ingress Classification Policies 8
Licensing Requirements for Classification 8
Configuring Classification 8
Configuring Class Maps 8
Configuring CoS Classification 9
Configuring Precedence Classification 10
Configuring DSCP Classification 12
Configuring Protocol Classification 13
Configuring IP RTP Classification 14
Configuring ACL Classification 15
Verifying the Classification Configuration 16
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CHAPTER 4 Configuring Policy Maps 17
Information About Policy Types 17
Configuring Policy Maps 19
Creating Policy Maps 19
Configuring Type QoS Policies 21
Configuring Type Network QoS Policies 22
Configuring Type Queuing Policies 23
Verifying the Policy Map Configuration 24
CHAPTER 5 Configuring Marking 27
Information About Marking 27
Configuring Marking 27
Configuring DSCP Marking 27
Configuring IP Precedence Marking 29
Configuring CoS Marking 30
Required CoS Marking Configuration in a Layer 3 Topology 31
Verifying the Marking Configuration 32
CHAPTER 6 Configuring QoS on the System 35
Information About System Classes 35
System Classes 35
Default System Classes 35
MTU 36
Configuring System QoS 37
Attaching the System Service Policy 37
Restoring the Default System Service Policies 38
Configuring the Queue Limit for a Specified Fabric Extender 39
Enabling the Jumbo MTU 40
Verifying the Jumbo MTU 41
Verifying the System QoS Configuration 41
CHAPTER 7 Configuring QoS on Interfaces 43
Information About Interface QoS 43
Trust Boundaries 43
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Policy for Fibre Channel Interfaces 44
QoS for Multicast Traffic 44
Configuring Interface QoS 45
Configuring Untagged CoS 45
Configuring an Interface Service Policy 45
Configuring a Service Policy for a Layer 3 Interface 46
Verifying the Interface QoS Configuration 47
CHAPTER 8 Configuring QoS on VLANs 49
Information About VLAN QoS 49
Precedence of QoS Policies 49
Example of Interface, System, and VLAN Policy Precedence 50
Example of Interface and System QoS Policy Precedence 50
Example of System and VLAN Policy Precedence 50
Example of VLAN QoS and VACL Policy Precedence 51
Limiting TCAM Entries for VLAN QoS 52
Guidelines and Limitations for VLAN QoS 52
Configuring VLAN QoS 53
Configuring or Changing the Interface QoS TCAM Limit 53
Removing the Interface QoS Limit from the TCAM 54
Configuring a Service Policy on a VLAN 54
Removing a Service Policy from a VLAN 55
Verifying the VLAN QoS Configuration 56
Feature History for VLAN QoS 56
CHAPTER 9 Configuring Queuing and Flow Control 57
Information About Queues 57
Ingress Queuing Policies 57
Egress Queuing Policies 57
Buffering and Queue Limits on the Cisco Nexus 5000 Platform 58
Buffering and Queue Limits on the Cisco Nexus Device 59
Information About Flow Control 60
Link-Level Flow Control 60
Priority Flow Control 60
Configuring Queuing 61
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Configuring the Queue Limit for a Specified Fabric Extender 61
Configuring No-Drop Buffer Thresholds 62
Configuring the Buffer Threshold for the Cisco Nexus 2148T Fabric Extender 63
Enabling Virtual Output Queuing Limits for Unicast Traffic on the Cisco Nexus Device 64
Configuring Flow Control 65
Link-Level Flow Control 65
Configuring Priority Flow Control 65
Configuring Link-Level Flow Control 66
Disabling Slow Port Pruning on Multicast Traffic on the Cisco Nexus 5500 Series
Device 66
Verifying the Queue and Flow Control Configurations 67
CHAPTER 10 QoS Configuration Examples 69
QoS Example 1 69
QoS Example 2 70
QoS Example 3 72
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Preface
The Preface contains the following sections:
•Audience, page vii
•Document Conventions, page vii
•Documentation Feedback, page viii
•Obtaining Documentation and Submitting a Service Request, page ix
Audience
This publication is for network administrators who configure and maintain Cisco Nexus devices and Cisco
Nexus 2000 Series Fabric Extenders.
Document Conventions
Command descriptions use the following conventions:
DescriptionConvention
Bold text indicates the commands and keywords that you enter literally
as shown.
bold
Italic text indicates arguments for which the user supplies the values.
Italic
Square brackets enclose an optional element (keyword or argument).[x]
Square brackets enclosing keywords or arguments separated by a vertical
bar indicate an optional choice.
[x | y]
Braces enclosing keywords or arguments separated by a vertical bar
indicate a required choice.
{x | y}
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DescriptionConvention
Nested set of square brackets or braces indicate optional or required
choices within optional or required elements. Braces and a vertical bar
within square brackets indicate a required choice within an optional
element.
[x {y | z}]
Indicates a variable for which you supply values, in context where italics
cannot be used.
variable
A nonquoted set of characters. Do not use quotation marks around the
string or the string will include the quotation marks.
string
Examples use the following conventions:
DescriptionConvention
Terminal sessions and information the switch displays are in screen font.screen font
Information you must enter is in boldface screen font.boldface screen font
Arguments for which you supply values are in italic screen font.
italic screen font
Nonprinting characters, such as passwords, are in angle brackets.< >
Default responses to system prompts are in square brackets.[ ]
An exclamation point (!) or a pound sign (#) at the beginning of a line
of code indicates a comment line.
!, #
This document uses the following conventions:
Means reader take note. Notes contain helpful suggestions or references to material not covered in the
manual.
Note
Means reader be careful. In this situation, you might do something that could result in equipment damage
or loss of data.
Caution
Documentation Feedback
To provide technical feedback on this document, or to report an error or omission, please send your comments
to: [email protected].
We appreciate your feedback.
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Preface
Documentation Feedback

Obtaining Documentation and Submitting a Service Request
For information on obtaining documentation, using the Cisco Bug Search Tool (BST), submitting a service
request, and gathering additional information, see What's New in Cisco Product Documentation, at: http://
www.cisco.com/c/en/us/td/docs/general/whatsnew/whatsnew.html.
Subscribe to What's New in Cisco Product Documentation, which lists all new and revised Cisco technical
documentation as an RSS feed and delivers content directly to your desktop using a reader application. The
RSS feeds are a free service.
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Preface
Obtaining Documentation and Submitting a Service Request

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Obtaining Documentation and Submitting a Service Request

CHAPTER 1
New and Changed Information
This chapter contains the following sections:
•New and Changed Information for this Release, page 1
New and Changed Information for this Release
The following table provides an overview of the significant changes to this guide for this current release. The
table does not provide an exhaustive list of all changes made to the configuration guide or of the new features
in this release.
Where DocumentedDescriptionFeature
Configuring QoS on VLANs, on
page 49
Support for QoS VLANs.VLAN QoS
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New and Changed Information for this Release

CHAPTER 2
Overview
This chapter contains the following sections:
•Information About Quality of Service, page 3
•Modular QoS CLI, page 3
•QoS for Traffic Directed to the CPU , page 5
Information About Quality of Service
The configurable Cisco NX-OS quality of service (QoS) features allow you to classify the network traffic,
prioritize the traffic flow, and provide congestion avoidance.
The default QoS configuration on the device provides lossless service for Fibre Channel and Fibre Channel
over Ethernet (FCoE) traffic and best-effort service for Ethernet traffic. QoS can be configured to provide
additional classes of service for Ethernet traffic. Cisco NX-OS QoS features are configured using Cisco
Modular QoS CLI (MQC).
Standard Ethernet is a best-effort medium which means that it lacks any form of flow control. In the event of
congestion or collisions, Ethernet will drop packets. The higher level protocols detect the missing data and
retransmit the dropped packets.
Fibre Channel requires a reliable transport system that guarantees the delivery of every packet. To properly
support FCoE, Ethernet has been enhanced with a priority flow control (PFC) mechanism to prevent congestion.
The FCoE QoS must be configured either if native FC or FCoE or FC and FCoE are in use. The FCoE QoS
must be added even if Ethernet is not configured on the switch.
The following commands will enable the default QoS configuration:
switch(config)# system qos
switch(config-sys-qos)# service-policy type queuing input fcoe-default-in-policy
switch(config-sys-qos)# service-policy type queuing output fcoe-default-out-policy
switch(config-sys-qos)# service-policy type qos input fcoe-default-in-policy
switch(config-sys-qos)# service-policy type network-qos fcoe-default-nq-policy
Modular QoS CLI
The Cisco Modular QoS CLI (MQC) provides a standard set of commands for configuring QoS.
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You can use MQC to define additional traffic classes and to configure QoS policies for the whole system and
for individual interfaces. Configuring a QoS policy with MQC consists of the following steps:
1Define traffic classes.
2Associate policies and actions with each traffic class.
3Attach policies to logical or physical interfaces as well as at the global system level.
MQC provides two command types to define traffic classes and policies:
class-map
Defines a class map that represents a class of traffic based on packet-matching criteria. Class maps are
referenced in policy maps.
The class map classifies incoming packets based on matching criteria, such as the IEEE 802.1p class
of service (CoS) value. Unicast and multicast packets are classified.
policy-map
Defines a policy map that represents a set of policies to be applied on a class-by-class basis to class
maps.
The policy map defines a set of actions to take on the associated traffic class, such as limiting the
bandwidth or dropping packets.
You define the following class-map and policy-map object types when you create them:
network-qos
Defines MQC objects that you can use for system level related actions.
qos
Defines MQC objects that you can use for classification.
queuing
Defines MQC objects that you can use for queuing and scheduling.
The qos type is the default for the class-map and policy-map commands, but not for the service-policy
which requires that you specify an explicit type.
Note
You can attach policies to interfaces or EtherChannels as well as at the global system level by using the
service-policy command.
You can view all or individual values for MQC objects by using the show class-map and show policy-map
commands.
An MQC target is an entity (such as an Ethernet interface) that represents a flow of packets. A service policy
associates a policy map with an MQC target and specifies whether to apply the policy on incoming or outgoing
packets. This mapping enables the configuration of QoS policies such as marking, bandwidth allocation,
buffer allocation, and so on.
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Modular QoS CLI

QoS for Traffic Directed to the CPU
The device automatically applies QoS policies to traffic that is directed to the CPU to ensure that the CPU is
not flooded with packets. Control traffic, such as bridge protocol data units (BPDU) frames, is given higher
priority to ensure delivery.
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QoS for Traffic Directed to the CPU

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QoS for Traffic Directed to the CPU

CHAPTER 3
Configuring Classification
This chapter contains the following sections:
•Information About Classification, page 7
•Ingress Classification Policies, page 8
•Licensing Requirements for Classification, page 8
•Configuring Classification, page 8
•Verifying the Classification Configuration, page 16
Information About Classification
Classification is the separation of packets into traffic classes. You configure the device to take a specific action
on the specified classified traffic, such as policing or marking down, or other actions.
You can create class maps to represent each traffic class by matching packet characteristics with classification
criteria.
Table 1: Classification Criteria
DescriptionClassification Criteria
Criteria specified in a named class-map object.Class map
Precedence value within the Type of Service (ToS)
byte of the IP Header.
Precedence
DSCP value within the DIffServ field of the IP
Header.
Differentiated Services Code Point (DSCP)
Selected set of protocols, including Address
Resolution Protocol (ARP) and Connectionless
Network Service (CLNS).
Protocol
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DescriptionClassification Criteria
Identify applications using Real-time Transport
Protocol (RTP) by UDP port number range.
IP RTP
Traffic is classified by the criteria defined in the
access control list (ACL).
ACL
Table 2: Supported RFCs
TitleRFC
Definition of the Differentiated Services Field (DS
Field) in the IPv4 and IPv6 Headers
RFC 2474
Ingress Classification Policies
You use classification to partition traffic into classes. You classify the traffic based on the packet property
(CoS field) or the packet header fields that include IP precedence, Differentiated Services Code Point (DSCP),
and Layer 2 to Layer 4 parameters. The values used to classify traffic are called match criteria.
Traffic that fails to match any class is assigned to a default class of traffic called class-default.
Licensing Requirements for Classification
This feature does not require a license. Any feature not included in a license package is bundled with the Cisco
NX-OS system images and is provided at no extra charge to you. For a complete explanation of the Cisco
NX-OS licensing scheme, see the Cisco NX-OS Licensing Guide.
Configuring Classification
Configuring Class Maps
You can create or modify a class map with the class-map command. The class map is a named object that
represents a class of traffic. In the class map, you specify a set of match criteria for classifying the packets.
You can then reference class maps in policy maps.
The class map type default is type qos and its match criteria default is match-all.Note
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Ingress Classification Policies

Procedure
PurposeCommand or Action
Enters global configuration mode.switch# configure terminal
Step 1
Creates or accesses a named object that represents the specified class
of traffic.
switch(config)# class-map
[type {network-qos |qos |
queuing}] class-map name
Step 2
Class-map names can contain alphabetic, hyphen, or underscore
characters, are case sensitive, and can be up to 40 characters.
The three class-map configuration modes are as follows:
•network-qos—Network-wide (global) mode. CLI prompt:
switch(config-cmap-nq)#
•qos—Classification mode; this is the default mode. CLI
prompt: switch(config-cmap-qos)#
•queuing—Queuing mode. CLI prompt:
switch(config-cmap-que)#
(Optional)
Specifies that packets must match any or all criteria that is defined
for a class map.
switch(config)# class-map
[type qos] [match-all |
match-any]class-map name
Step 3
•match-all—Classifies traffic if packets match all criteria that
is defined for a specified class map (for example, if both the
defined CoS and the ACL criteria match).
•match-any—Classifies traffic if packets match any criteria
that is defined for a specified class map (for example, if either
the CoS or the ACL criteria matches).
Class-map names can contain alphabetic, hyphen, or underscore
characters, are case sensitive, and can be up to 40 characters.
(Optional)
Deletes the specified class map.
switch(config)# no class-map
[type {network-qos |qos |
queuing}] class-name
Step 4
You cannot delete the two system-defined class maps:
class-fcoe and class-default.
Note
Class-map names can contain alphabetic, hyphen, or underscore
characters, are case sensitive, and can be up to 40 characters.
Configuring CoS Classification
You can classify traffic based on the class of service (CoS) in the IEEE 802.1Q header. This 3-bit field is
defined in IEEE 802.1p to support QoS traffic classes. CoS is encoded in the high order 3 bits of the VLAN
ID Tag field and is referred to as user_priority.
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Configuring Classification
Configuring CoS Classification

The Cisco Nexus 2148 Fabric Extender does not support frames with the dot1p vlan 0 tag.Note
If a system class is configured with a no-drop function, the match cos command serves an additional purpose.
The switch sends the CoS value to the adapter so that the adapter will apply a PFC pause for this CoS value.
The FCoE system class has a default CoS value of 3. You can add a match cos configuration to the FCoE
system class to set a different CoS value. A PFC pause will be applied to traffic that matches the new value.
Procedure
PurposeCommand or Action
Enters global configuration mode.switch# configure terminal
Step 1
Creates a named object that represents a class of traffic.
Class-map names can contain alphabetic, hyphen, or
switch(config)# class-map type
qos class-name
Step 2
underscore characters, are case sensitive, and can be up to 40
characters.
Specifies the CoS value to match for classifying packets into
this class. You can configure a CoS value in the range of 0
to 7.
switch(config-cmap-qos)# match
cos cos-value
Step 3
When a Cisco Nexus 2148T Fabric Extender is
connected and in use, data traffic should never be
marked with a CoS value of 7. CoS 7 is reserved for
control traffic transiting the Fabric Extender.
Note
(Optional)
Removes the match from the traffic class.
switch(config-cmap-qos)# no
match cos cos-value
Step 4
This example shows how to classify traffic by matching packets based on a defined CoS value:
switch# configure terminal
switch(config)# class-map type qos match-any class_cos
switch(config-cmap-qos)# match cos 4, 5-6
Use the show class-map command to display the CoS value class-map configuration:
switch# show class-map class_cos
Configuring Precedence Classification
You can classify traffic based on the precedence value in the type of service (ToS) byte field of the IP header
(either IPv4 or IPv6). The following table shows the precedence values:
Table 3: Precedence Values
List of Precedence ValuesValue
IP precedence value<0-7>
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Configuring Classification
Configuring Precedence Classification