Cisco ASR 9000 Series User manual

Cisco ASR 9000 Series Aggregation Services Router Modular Quality
of Service Configuration Guide, Release 6.1.x
First Published: 2016-11-01
Americas Headquarters
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134-1706
USA
http://www.cisco.com
Tel: [phone]
800 553-NETS (6387)
Fax: [phone]

THE SPECIFICATIONS AND INFORMATION REGARDING THE PRODUCTS IN THIS MANUAL ARE SUBJECT TO CHANGE WITHOUT NOTICE. ALL STATEMENTS,
INFORMATION, AND RECOMMENDATIONS IN THIS MANUAL ARE BELIEVED TO BE ACCURATE BUT ARE PRESENTED WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED. USERS MUST TAKE FULL RESPONSIBILITY FOR THEIR APPLICATION OF ANY PRODUCTS.
THE SOFTWARE LICENSE AND LIMITED WARRANTY FOR THE ACCOMPANYING PRODUCT ARE SET FORTH IN THE INFORMATION PACKET THAT SHIPPED WITH
THE PRODUCT AND ARE INCORPORATED HEREIN BY THIS REFERENCE. IF YOU ARE UNABLE TO LOCATE THE SOFTWARE LICENSE OR LIMITED WARRANTY,
CONTACT YOUR CISCO REPRESENTATIVE FOR A COPY.
The Cisco implementation of TCP header compression is an adaptation of a program developed by the University of California, Berkeley (UCB) as part of UCB's public domain version
of the UNIX operating system. All rights reserved. Copyright ©1981, Regents of the University of California.
NOTWITHSTANDING ANY OTHER WARRANTY HEREIN, ALL DOCUMENT FILES AND SOFTWARE OF THESE SUPPLIERS ARE PROVIDED “AS IS" WITH ALL FAULTS.
CISCO AND THE ABOVE-NAMED SUPPLIERS DISCLAIM ALL WARRANTIES, EXPRESSED OR IMPLIED, INCLUDING, WITHOUT LIMITATION, THOSE OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OR ARISING FROM A COURSE OF DEALING, USAGE, OR TRADE PRACTICE.
IN NO EVENT SHALL CISCO OR ITS SUPPLIERS BE LIABLE FOR ANY INDIRECT, SPECIAL, CONSEQUENTIAL, OR INCIDENTAL DAMAGES, INCLUDING, WITHOUT
LIMITATION, LOST PROFITS OR LOSS OR DAMAGE TO DATA ARISING OUT OF THE USE OR INABILITY TO USE THIS MANUAL, EVEN IF CISCO OR ITS SUPPLIERS
HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network
topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional
and coincidental.
Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: http://
www.cisco.com/go/trademarks. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership
relationship between Cisco and any other company. (1110R)
©2016 Cisco Systems, Inc. All rights reserved.

CONTENTS
Preface Preface xv
Changes to this Document xv
Obtaining Documentation and Submitting a Service Request xv
CHAPTER 1 New and Changed QoS Features 1
New and Changed QoS Features 1
CHAPTER 2 Modular QoS Overview 3
Information About Modular Quality of Service Overview 3
Benefits of Cisco IOS XR QoS Features 3
QoS Techniques 4
Packet Classification and Marking 4
Default Marking Behavior 5
Congestion Management 5
Congestion Avoidance 6
Differentiated Service Model for Cisco IOS XR Software 6
Access Node Control Protocol 6
Additional Cisco IOS XR QoS Supported Features 7
Modular QoS Command-Line Interface 7
Fabric QoS 7
Where to Go Next 7
Additional References 7
Related Documents 8
Standards 8
MIBs 8
RFCs 9
Technical Assistance 9
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release 6.1.x
iii

CHAPTER 3 Configuring Access Node Control Protocol 11
Prerequisites for Configuring ANCP 12
Restrictions for Configuring ANCP 12
Information About Configuring ANCP 12
ANCP Adjacencies 12
Neighbor Adjacency Timing 12
ANCP Messages 13
Port Mapping 13
Rate Adjustment 13
Prioritization of ANCP Traffic 14
Process Restart 14
ANCP and QoS Interaction 14
Multi Chassis Link Aggregation 14
ANCP over MC-LAG 15
How to Configure ANCP on Cisco 16
Enabling ANCP 16
Configuring ANCP Server Sender Name 17
Configuring ANCP Neighbors 18
Mapping AN Ports to VLAN Subinterfaces 20
Configuring ANCP Rate Adjustment 23
Configuration Examples for Configuring ANCP contains the following examples: 24
Configuring ANCP Server Sender Name: Example 24
Configuring ANCP Neighbors: Example 24
Mapping AN ports to VLAN Subinterfaces: Example 27
Configuring ANCP Rate Adjustment: Example 28
ANCP and QoS Interaction: Example 28
QoS Policy Inconsistency on an Interface: Example 31
ANCP Rate Change 33
Port Speed Change 34
The show qos inconsistency Command: Example 35
Additional References 36
Related Documents 36
Standards 36
MIBs 36
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release
6.1.x
iv
Contents

RFCs 37
Technical Assistance 37
Configuring Access Node Control Protocol 37
CHAPTER 4 Configuring Modular QoS Congestion Avoidance 39
Prerequisites for Configuring Modular QoS Congestion Avoidance 40
Information About Configuring Modular QoS Congestion Avoidance 40
Random Early Detection and TCP 40
Queue-limit for WRED 40
Tail Drop and the FIFO Queue 41
Configuring Random Early Detection 41
Configuring Weighted Random Early Detection 43
Configuring Tail Drop 46
Additional References 49
Related Documents 49
Standards 49
MIBs 50
RFCs 50
Technical Assistance 50
CHAPTER 5 Configuring Modular QoS Congestion Management 51
Prerequisites for Configuring QoS Congestion Management 52
Information About Configuring Congestion Management 53
Congestion Management Overview 53
Modified Deficit Round Robin 53
Low-Latency Queueing with Strict Priority Queueing 54
Configured Accounting 54
QoS for IPv6 ACLs 55
Traffic Shaping 55
Regulation of Traffic with the Shaping Mechanism 55
Traffic Policing 56
Regulation of Traffic with the Policing Mechanism 57
Single-Rate Policer 57
Two-Rate Policer 58
Committed Bursts and Excess Bursts 60
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release 6.1.x
v
Contents

Committed Bursts 60
Committed Burst Calculation 61
Excess Bursts 61
Excess Burst Calculation 61
Deciding if Packets Conform or Exceed the Committed Rate 62
Two-Rate Three-Color (2R3C) Policer 62
Hierarchical Policing 63
Multiple Action Set 63
Packet Marking Through the IP Precedence Value, IP DSCP Value, and the MPLS
Experimental Value Setting 63
Traffic Policing on Layer 2 ATM Interfaces 64
Restrictions 65
Traffic Policing on a Layer 2 ATM interface: Example 65
Explicit Congestion Notification 65
Implementing ECN 66
Packet Handling when ECN is enabled 66
QoS for Bridge-Group Virtual Interfaces 67
QoS on BVI 67
Restrictions 67
Classification and Marking for BVI 68
Policer Granularity and Shaper Granularity 68
Congestion Management Using DEI 68
How to Configure QoS Congestion Management 69
Configuring Guaranteed and Remaining Bandwidths 69
Configuring Guaranteed Bandwidth 72
Configuring Bandwidth Remaining 75
Configuring Low-Latency Queueing with Strict Priority Queueing 78
Configuring Traffic Shaping 80
Configuring Traffic Policing (Two-Rate Color-Blind) 82
Configuring Traffic Policing (2R3C) 85
Configuring Hierarchical Policing 88
Traffic Policing for BVI 89
Configuring ECN 93
Configuration Examples for Configuring Congestion Management 95
Service Fragment Configurations: Example 95
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release
6.1.x
vi
Contents

Traffic Policing for BVI: Example 95
ECN: Example 96
Hierarchical Policing: Example 96
Additional References 96
Related Documents 96
Standards 97
MIBs 97
RFCs 97
Technical Assistance 97
CHAPTER 6 Configuring Modular QoS Service Packet Classification 99
Prerequisites for Configuring Modular QoS Packet Classification 101
Information About Configuring Modular QoS Packet Classification 101
Packet Classification Overview 101
Traffic Class Elements 102
Traffic Policy Elements 102
Default Traffic Class 103
Bundle Traffic Policies 103
Shared Policy Instance 103
Policy Inheritance 104
Port Shape Policies 104
Support for 16 Queues 104
Class-based Unconditional Packet Marking Feature and Benefits 105
Specification of the CoS for a Packet with IP Precedence 106
IP Precedence Bits Used to Classify Packets 107
IP Precedence Value Settings 108
Classification Based on DEI 108
Default DEI Marking 108
TCP Establishment DSCP Marking/ Set IP Precedence/DSCP for NTP 109
IP Precedence Compared to IP DSCP Marking 109
Configuring DSCP for source IPv4 address for NTP Packets 109
Configure DSCP CS7 (Precedence 7) 112
Configure IPv4 DSCP Precedence 112
Configure IPv6 DSCP precedence 114
QoS Policy Propagation Using Border Gateway Protocol 116
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release 6.1.x
vii
Contents

QoS on PWHE 117
Supported Features 117
Limitations 118
Bandwidth Distribution 118
Classification and Marking Support 118
Policing and Queuing support 121
Co-existence of PWHE Main and Subinterface Policies 122
PW-Ether Subinterface Policy 123
PW-Ether Subinterface Shared Policy Instance 123
Scale Information 124
Policy Instantiation 124
PWHE without QoS policy 125
Configuring QoS on PWHE: Example. 126
Port Shaper Policy Support on L2 Fabric ICL Interface 127
Configuring Port Shaper Policy on the ICL Interface in L2 Fabric Mode 128
Ingress Queuing Support 129
In-Place Policy Modification 132
Recommendations for Using In-Place Policy Modification 133
Dynamic Modification of Interface Bandwidth 133
Policy States 133
Inter-Class Policer Bucket Sharing 133
Policer Bucket Shared 133
Policer Bucket Referred 134
Interface Support 134
Classification Support for Ethernet-Services ACL 134
How to Configure Modular QoS Packet Classification 135
Creating a Traffic Class 135
Creating a Traffic Policy 138
Attaching a Traffic Policy to an Interface 140
Attaching a Shared Policy Instance to Multiple Subinterfaces 141
Attaching a Shared Policy Instance to Bundle Interfaces or EFP Bundles 142
Configuring Class-based Unconditional Packet Marking 143
Configuring QoS Policy Propagation Using Border Gateway Protocol 147
Policy Propagation Using BGP Configuration Task List 147
Overview of Tasks 147
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release
6.1.x
viii
Contents

Defining the Route Policy 148
Applying the Route Policy to BGP 148
Configuring QPPB on the Desired Interfaces 149
Configuring QPPB on the GRE Tunnel Interfaces 150
QPPB Scenario 151
Configuring Hierarchical Ingress Policing 152
Configuring Policer Bucket Sharing 153
Overview of Multiple QoS Policy Support 156
Use Case —Multiple QoS Policy Support 156
Configuring Multiple QoS Policy Support 157
Restrictions for Multiple QoS Policy Support 160
Policy Combinations 161
Multi Policy and Interface Hierarchy 162
Statistics 166
Policy Modification 168
Supported Features by Multi Policies 169
Configuration Examples for Configuring Modular QoS Packet Classification 170
Traffic Classes Defined: Example 170
Traffic Policy Created: Example 170
Traffic Policy Attached to an Interface: Example 171
Traffic Policy Attached to Multiple Subinterfaces: Example 171
Traffic Policy Attached to a Bundle Interface: Example 171
EFP Load Balancing with Shared Policy Instance: Example 171
Configuring a Bundle Interface: Example 171
Configuring Two Bundle EFPs with the Load Balance Options: Example 172
Default Traffic Class Configuration: Example 172
class-map match-any Command Configuration: Example 172
Class-based Unconditional Packet Marking: Examples 172
IP Precedence Marking Configuration: Example 173
IP DSCP Marking Configuration: Example 173
QoS Group Marking Configuration: Example 173
CoS Marking Configuration: Example 174
MPLS Experimental Bit Imposition Marking Configuration: Example 174
MPLS Experimental Topmost Marking Configuration: Example 174
QoS Policy Propagation using BGP: Examples 175
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release 6.1.x
ix
Contents

Applying Route Policy: Example 175
Applying QPPB on a Specific Interface: Example 175
Applying QPPB on a GRE Tunnel Interface: Example 175
In-Place Policy Modification: Example 176
Configuring Inter Class Policer Bucket Sharing: Example 177
Additional References 177
Related Documents 177
Standards 178
MIBs 178
RFCs 178
Technical Assistance 178
CHAPTER 7 Modular QoS Deployment Scenarios 179
802.1ad DEI 180
Mark DEI Based on a Policing Action: Example 181
Mark DEI Based on Incoming Fields: Example 181
Congestion Management Using DEI: Example 181
Frame Relay QoS 181
Frame Relay DLCI Classification 182
Frame Relay DE Classification 182
Frame Relay DE Marking 182
Frame Relay QoS: Example 183
IP Header Compression QoS 185
IP Header Compression QoS: Example 186
L2VPN QoS 186
Frame Relay <-> Frame Relay Over Pseudowire: Example 186
Frame Relay <-> Ethernet Over Pseudowire: Example 188
MLPPP QoS/MLFR QoS 189
Multiclass MLPPP with QoS 190
MLPPP QoS/MLFR QoS: Example 191
MPLS QoS 191
MPLS Uniform Mode 192
MPLS Pipe Mode 192
MPLS Short Pipe Mode 193
Uniform, Pipe, Short Pipe Modes: Ingress PE Example 193
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release
6.1.x
x
Contents

Uniform Mode: Egress PE Example 194
Pipe Mode: Egress PE Example 195
Short Pipe Mode: Egress PE Example 195
QoS on Multicast VPN 196
QoS on Multicast VPN: Example 196
Unconditional Marking 196
Conditional Marking 196
SIP 700 for the ASR 9000 196
QoS on Multicast VPN: Example 196
QoS on NxDS0 Interfaces 197
One-Level Policy Applied to Main Interface: Example 197
Two-Level Policy Applied to a Subinterface: Example 198
VPLS and VPWS QoS 198
VPLS and VPWS QoS: Example 199
Related Information 201
CHAPTER 8 Configuring Hierarchical Modular QoS 203
How to Configure Hierarchical QoS 204
Port policy configurations - Defining a service fragment 204
Configuring sub-interface policy 205
Applying a service fragment policy on a physical interface 207
Configuring the Three-Parameter Scheduler 207
ASR 9000 Ethernet Line Cards 208
SIP 700 for the ASR 9000 210
Attaching Hierarchical Policies to Physical and Virtual Links 212
Configuring Enhanced Hierarchical Ingress Policing 214
Two-Level Hierarchical Queueing Policy: Example 216
Three-Level Hierarchical Queueing Policy: Examples 217
Three-Level Hierarchical Queueing Policy: Examples 217
SIP 700 for the ASR 9000 218
Three-Parameter Scheduler: Examples 220
Three-Parameter Scheduler: Examples 220
SIP 700 for the ASR 9000 220
Hierarchical Policing: Examples 221
Hierarchical Policing: Examples 221
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release 6.1.x
xi
Contents

SIP 700 for the ASR 9000 221
Attaching Service Policies to Physical and Virtual Links: Examples 222
Physical Link: Example 222
Virtual Link: Example 222
Service Fragment Configurations: Example 222
Enhanced Hierarchical Ingress Policing: Example 223
Verifying the Configuration of Hierarchical Policies 223
Additional References 224
Related Documents 224
Standards 225
MIBs 225
RFCs 225
Technical Assistance 225
CHAPTER 9 Configuring Modular QoS on Link Bundles 227
Link Bundling Overview 228
Load Balancing 228
Layer 3 Load Balancing on Link Bundles 229
QoS and Link Bundling 229
QoS for POS link bundling 229
Input QoS Policy setup 229
Output QoS Policy setup 230
Aggregate Bundle QoS Mode 230
Load Balancing in Aggregate Bundle QoS 231
QoS Policy in Aggregate bundle mode 231
Enabling Aggregate Bundle QoS 231
Additional References 233
Related Documents 233
Standards 234
MIBs 234
RFCs 234
Technical Assistance 234
CHAPTER 10 Configuring Flow Aware QoS 235
Information About Flow Aware QoS 235
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release
6.1.x
xii
Contents

Flow Aware QoS 235
Flow Aware QoS Key Terms 236
Variants of Flow Aware QoS 237
Difference between Regular QoS and Flow Aware CAC 238
Difference between Regular QoS and Flow Aware Policer or UBRL 239
Flow Aware CAC 239
CAC Action Variations 240
CAC Reject 240
CAC Redirect 240
Scale Information for CAC 240
Restrictions 240
User Based Rate-Limiting (UBRL) 242
UBRL Scenarios 242
UBRL for Multiple Sources 242
Bidirectional UBRL 243
Egress UBRL 243
UBRL for Multiple Destination 244
Scale Information for UBRL 244
UBRL Policer Scale Information for ASR 9000 High Density 100GE Ethernet LCs
on Cisco IOS XR 244
Flow Masks for UBRL 245
Restrictions 245
How to Configure Flow Aware QoS 246
Configuring Flow Aware CAC Reject Action 246
Configuring Flow Aware CAC Redirect Action 250
Configuring User Based Rate Limiting (UBRL) 256
Configuration Examples for Configuring Flow Aware QoS 259
Configuring Flow Aware CAC Reject Action: Example 259
Configuring Flow Aware CAC Redirect Action: Example 259
Configuring UBRL for Multiple Sources: Example 260
Configuring Bidirectional UBRL: Example 260
Configuring UBRL for Multiple Sessions: Example 261
Additional References 261
Related Documents 261
Standards 262
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release 6.1.x
xiii
Contents

MIBs 262
RFCs 262
Technical Assistance 263
CHAPTER 11 Configuring QoS on the Satellite System 265
QoS on the Satellite System 265
Limitations 266
Auto QoS 266
QoS Offload on Satellite 268
Benefits of QoS Offload 269
Supported Platform-Specific Information for QoS Offload 269
Supported Capability Matrix 269
Supported Classification Combination 278
Supported Scalability Matrix for 9000v 279
Supported Scalability Matrix for 901 280
QoS Offload Configuration Overview 281
Sample QoS Offload Configuration 281
Prerequisites for QoS Offload Configuration 282
Offloading Service-policy on Physical Access Port 282
Offloading Service-policy on Bundle Access Port 284
Offloading Service-policy on Physical Satellite Fabric Link 287
Offloading Service-policy on Bundle SFL 290
Offloading Service-policy on L2 Fabric Physical SFL 292
Offloading Service-policy on Ring Physical SFL 295
How to Configure HQoS on a Satellite 299
Configure the Traffic Class 299
Configure the Traffic Policy 300
Attach Hierarchical Policies to the Interface 302
Configuration Examples for QoS Offload 303
Offloading Service-policy on Physical Access Port: Example 304
Offloading Service-policy on Bundle Access Port: Example 304
Offloading Service-policy on Physical SFL: Example 304
Offloading Service-policy on Bundle SFL: Example 305
Offloading Service-policy on L2 Fabric physical SFL: Example 305
Offloading Service-policy on Ring Physical SFL: Example 306
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release
6.1.x
xiv
Contents

Preface
From Release 6.1.2 onwards, Cisco introduces support for the 64-bit Linux-based IOS XR operating system.
Extensive feature parity is maintained between the 32-bit and 64-bit environments. Unless explicitly marked
otherwise, the contents of this document are applicable for both the environments. For more details on Cisco
IOS XR 64 bit, refer to the Release Notes for Cisco ASR 9000 Series Routers, Release 6.1.2 document.
This guide describes the Cisco IOS XR QoS configurations. The preface for the Cisco ASR 9000 Series
Aggregation Services Router Modular Quality of Service Configuration Guide contains these sections:
•Changes to this Document, page xv
•Obtaining Documentation and Submitting a Service Request, page xv
Changes to this Document
This table lists the changes made to this document since it was first published.
SummaryDate
Initial release of this document.November 2016
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.
To receive new and revised Cisco technical content directly to your desktop, you can subscribe to the What's
New in Cisco Product Documentation RSS feed. RSS feeds are a free service.
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release 6.1.x
xv

Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release
6.1.x
xvi
Preface
Obtaining Documentation and Submitting a Service Request

CHAPTER 1
New and Changed QoS Features
•New and Changed QoS Features, page 1
New and Changed QoS Features
Table 1: New and Changed Features
Where DocumentedChanged in ReleaseDescriptionFeature
Configuring Flow Aware QoS
chapter UBRL Policer Scale
Information for ASR 9000 High
Density 100GE Ethernet LCs
on Cisco IOS XR , on page 244
Release 6.1.2NAUBRL Policer Scale
Information for ASR 9000 High
Density 100GE Ethernet LCs
Configuring QoS on the
Satellite System chapter
Release 6.1.2NAQoS offload on NCS 5000
Series Router
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release 6.1.x
1

Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release
6.1.x
2
New and Changed QoS Features
New and Changed QoS Features

CHAPTER 2
Modular QoS Overview
Quality of Service (QoS) is the technique of prioritizing traffic flows and providing preferential forwarding
for higher-priority packets. The fundamental reason for implementing QoS in your network is to provide
better service for certain traffic flows. A traffic flow can be defined as a combination of source and destination
addresses, source and destination socket numbers, and the session identifier. A traffic flow can more broadly
be described as a packet moving from an incoming interface that is destined for transmission to an outgoing
interface. The traffic flow must be identified, classified, and prioritized on all routers and passed along the
data forwarding path throughout the network to achieve end-to-end QoS delivery. The terms traffic flow and
packet are used interchangeably throughout this module.
To implement QoS on a network requires the configuration of QoS features that provide better and more
predictable network service by supporting bandwidth allocation, improving loss characteristics, avoiding
and managing network congestion, metering network traffic, or setting traffic flow priorities across the
network.
This module contains overview information about modular QoS features within a service provider network.
•Information About Modular Quality of Service Overview, page 3
•Where to Go Next, page 7
•Additional References, page 7
Information About Modular Quality of Service Overview
Before configuring modular QoS on your network, you must understand these concepts:
Benefits of Cisco IOS XR QoS Features
The Cisco IOS XR QoS features enable networks to control and predictably service a variety of networked
applications and traffic types. Implementing Cisco IOS XR QoS in your network promotes these benefits:
•Control over resources. You have control over which resources (bandwidth, equipment, wide-area
facilities, and so on) are being used. For example, you can limit bandwidth consumed over a backbone
link by FTP transfers or give priority to an important database access.
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release 6.1.x
3

•Tailored services. If you are an Internet Service Provider (ISP), the control and visibility provided by
QoS enables you to offer carefully tailored grades of service differentiation to your customers.
•Coexistence of mission-critical applications. Cisco IOS XR QoS features ensure:
◦That bandwidth and minimum delays required by time-sensitive multimedia and voice applications
are available.
◦That your WAN is used efficiently by mission-critical applications that are most important to your
business.
◦That bandwidth and minimum delays required by time-sensitive multimedia and voice applications
are available.
◦Cisco ASR 9000 series router supports 10,000 unique policy-maps per system and 2,000 unique
policy-maps per Linecard (regardless of Linecard Type).
◦That other applications using the link get their fair service without interfering with mission-critical
traffic.
QoS Techniques
QoS on Cisco IOS XR software relies on these techniques to provide for end-to-end QoS delivery across a
heterogeneous network:
•Packet classification and marking
•Congestion management
•Congestion avoidance
Before implementing the QoS features for these techniques, you should identify and evaluate the traffic
characteristics of your network because not all techniques are appropriate for your network environment.
Packet Classification and Marking
Packet classification and marking techniques identify the traffic flow, and provide the capability to partition
network traffic into multiple priority levels or classes of service. After classification is complete, any other
QoS actions can be performed.
Identification of a traffic flow can be performed by using several methods within a single router, such as
access control lists (ACLs), protocol match, IP precedence, IP differentiated service code point (DSCP), MPLS
EXP bit, or Class of Service (CoS).
Marking of a traffic flow is performed by:
•Setting IP Precedence or DSCP bits in the IP Type of Service (ToS) byte.
•Setting CoS bits in the Layer 2 headers.
•Setting EXP bits within the imposed or the topmost Multiprotocol Label Switching (MPLS) label.
•Setting qos-group and discard-class bits.
Marking can be carried out:
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide, Release
6.1.x
4
Modular QoS Overview
QoS Techniques