Cisco IOS XR Software Release 5.2 Configuration Guide

Cisco ASR 9000 Series Aggregation Services Router Broadband

Network Gateway Configuration Guide, Release 5.2.x

First Published: 2014-07-03

Last Modified: 2014-10-24

Americas Headquarters

Cisco Systems, Inc.

170 West Tasman Drive

San Jose, CA 95134-1706

USA

http://www.cisco.com

Tel: 408 526-4000

800 553-NETS (6387)

Fax: 408 527-0883

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

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)

CONTENTS

Preface

Preface xi

Changes to This Document xi

Obtaining Documentation and Submitting a Service Request xi

CHAPTER 1

New and Changed BNG Features 1

New and Changed BNG Feature Information 1

CHAPTER 2

Broadband Network Gateway Overview 5

Understanding BNG 5

BNG Architecture 6

BNG Role in ISP Network Models 8

BNG Packaging 9

Installing and Activating the BNG Pie on Cisco ASR 9000 Series Router 9

BNG Configuration Process 11

Hardware Requirements for BNG 11

BNG Interoperability 12

BNG Smart Licensing 13

CHAPTER 3

Configuring Authentication, Authorization, and Accounting Functions 15

AAA Overview 16

Using RADIUS Server Group 17

Configuring RADIUS Server Group 17

Specifying Method List 19

Configuring Method Lists for AAA 20

Defining AAA Attributes 21

Creating Attributes of Specific Format 22

Configuring RADIUS Attribute List 27

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide, Release

5.2.x

iii

Configuring RADIUS Attribute Format 28

Configuring RADIUS Attribute Nas-port-type 29

Configuring AAA Attribute Format Function 30

Making RADIUS Server Settings 31

Configuring RADIUS Server Settings 32

Configuring Automated Testing 36

Setting IP DSCP for RADIUS Server 36

Balancing Transaction Load on the RADIUS Server 37

Configuring Load Balancing for Global RADIUS Server Group 38

Configuring Load Balancing for a Named RADIUS Server Group 39

Throttling of RADIUS Records 39

Configuring RADIUS Throttling Globally 40

Configuring RADIUS Throttling on a Server Group 41

RADIUS Change of Authorization (CoA) Overview 43

Multi-Action Change of Authorization 45

Generating Accounting Records 46

High Availability for MA-CoA 46

An Example with Verification Commands 47

Restrictions in Multi-Action Change of Authorization 50

User Authentication and Authorization in the Local Network 50

Policy Configurations for IPoE Sessions 51

Policy Configurations for PTA Sessions 54

Service Accounting 55

Configuring Service Accounting 56

Statistics Infrastructure 58

Configuring Statistics IDs (statsD) 59

Understanding Per-VRF AAA Function 59

RADIUS Double-Dip Feature 60

Additional References 60

CHAPTER 4

Activating Control Policy 63

Control Policy Overview 63

Creating Class-Map 65

Configuring a Class-Map 65

Creating Policy-Map 66

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide,

Release 5.2.x

iv

Contents

Control Policy Events 66

Configuring a Policy-Map 68

Activating Policy-Map 70

Enabling a Service-Policy on a Subscriber Interface 70

Defining Dynamic Templates 70

Additional References 72

CHAPTER 5

Establishing Subscriber Sessions 73

Subscriber Session Overview 74

Establishing IPoE Session 76

Enabling IPv4 or IPv6 on an Access Interface 78

Creating Dynamic Template for IPv4 or IPv6 Subscriber Session 79

Creating a Policy-Map to Run During IPoE Session 81

Enabling IPoE Subscribers on an Access Interface 82

Routed Subscriber Sessions 85

DHCP-initiated Routed Subscriber Sessions 87

Call Flow of DHCPv4-initiated Routed Subscriber Sessions 88

Packet-triggered Routed Subscriber Sessions 89

Deployment Model for IPv6 Routed Network 90

Call Flow of IPv6 Routed Subscriber Session 91

Restrictions for Routed Subscriber Sessions 91

Configuring Routed Subscriber Sessions 92

Establishing PPPoE Session 94

Provisioning PPP PTA Session 95

Creating PPPoE Profiles 95

Creating a PPP Dynamic-Template 96

Creating a Policy-Map to Run During PPPoE Session 97

Modifying VRF for PPPoE Sessions 99

Applying the PPPoE Configurations to an Access Interface 100

Provisioning PPP LAC Session 101

Configuring the VPDN Template 102

Configuring Maximum Simultaneous VPDN Sessions 104

Activating VPDN Logging 105

Configuring Options to Apply on Calling Station ID 106

Configuring L2TP Session-ID Commands 107

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide, Release

5.2.x

v

Contents

Configuring L2TP Class Options 108

Configuring Softshut for VPDN 110

L2TP Reassembly on LAC 111

Enabling L2TP Reassembly on LAC 112

L2TP Access Concentrator Stateful Switchover 113

Enabling LAC SSO 113

Enabling RPFO on Process-failures 114

PPPoE Smart Server Selection 115

Configuring PADO Delay 116

PPPoE Session Limit, Throttle and In-flight-window 118

PPPoE Session Limit 118

Configuring PPPoE Session Limit 118

PPPoE Session Throttle 119

Configuring PPPoE Session Throttle 120

PPPoE In-flight-window 121

Making DHCP Settings 121

Enabling DHCP Proxy 122

Configuring DHCP IPv4 Profile Proxy Class 123

Configuring a Circuit-ID for an Interface 124

Configuring a Remote-ID 125

Configuring the Client Lease Time 126

Attaching a Proxy Profile to an Interface 127

DHCPv4 Server 128

Enabling DHCP Server 128

Configuring DHCPv4 Server Profile 129

Specifying DHCP Lease Limit 132

Specifying the Lease Limit for a Circuit-ID 132

Specifying the Lease Limit for a Remote-ID 133

Specifying the Lease Limit for an Interface 134

Understanding DHCP Option-82 135

Option 82 Relay Information Encapsulation 136

Configuring DHCPv4 Class of Service (CoS) 136

DHCP RADIUS Proxy 136

Subscriber Session-Restart 137

DHCP Session MAC Throttle 137

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide,

Release 5.2.x

vi

Contents

DHCPv6 Overview 138

DHCPv6 Server and DHCPv6 Proxy 139

Enabling DHCPv6 for Different Configuration Modes 139

Setting Up DHCPv6 Parameters 142

DHCPv6 Features 144

High Availability Support for DHCPv6 145

DHCPv6 Prefix Delegation 145

IPv6 IPoE Subscriber Support 145

Configuring IPv6 IPoE Subscriber Interface 146

IPv6 PPPoE Subscriber Support 152

Configuring IPv6 PPPoE Subscriber Interfaces 152

Ambiguous VLAN Support 158

Configuring Ambiguous VLANs 158

DHCPv6 Address or Prefix Pool 160

Configuring IPv6 Address or Prefix Pool Name 160

DHCPv6 Dual-Stack Lite Support 162

Configuring AFTR Fully Qualified Domain Name for DS-Lite 163

VRF Awareness in DHCPv6 164

Defining VRF in a Dynamic Template 164

Rapid commit 165

Packet Handling on Subscriber Interfaces 165

IPv6 Neighbor Discovery 167

Line Card Subscribers 167

External Interaction for LC Subscribers 168

Benefits and Restrictions of Line Card Subscribers 168

High Availability for Line Card Subscribers 169

Static Sessions 170

Restrictions for static sessions 171

Subscriber Session Limit 171

eBGP over PPPoE 172

BNG over Pseudowire Headend 173

QoS on BNG Pseudowire Headend 173

Features Supported for BNG over Pseudowire Headend 174

Unsupported Features and Restrictions for BNG over Pseudowire Headend 175

Additional References 175

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide, Release

5.2.x

vii

Contents

CHAPTER 6

Deploying the Quality of Service (QoS) 177

Quality of Service Overview 178

Configuring Service-policy and Applying Subscriber Settings Through RADIUS 179

Configuring Service-policy and Applying Subscriber Settings Through Dynamic

Template 180

Parameterized QoS 183

Parameterized QoS Syntax 184

Configuring Parameterized QoS Policy Through RADIUS 189

Modifying Service Policy through CoA 191

RADIUS Based Policing - QoS Shaper Parameterization 193

Sample Configuration and Use Cases for QoS Shaper Parameterization 194

Verification of QoS Shaper Parameterization Configurations 194

Supported Scenarios of QoS Shaper Parameterization 197

Restrictions of QoS Shaper Parameterization 197

QoS Accounting 198

Configuring QoS Accounting 199

Support for Shared Policy Instance 200

Configuring a Policy with SPI in the Input or Output Direction Using Dynamic

Template 201

Configuring a Policy with SPI in the Input or Output Direction Using RADIUS 204

Merging QoS Policy-maps 206

Enabling Policy-maps Merge 206

QoS Features Supported on BNG 210

VLAN Policy on Access Interface 214

Configuring Policy on S-VLAN 214

Configuring VLAN Policy on an Access Interface 215

Additional References 217

CHAPTER 7

Configuring Subscriber Features 219

CHAPTER 8

BNG Geo Redundancy 279

Geo Redundancy Overview 279

Subscriber Redundancy Group (SRG) 281

Session Distribution Across SRG 282

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide,

Release 5.2.x

viii

Contents

Benefits of BNG Geo Redundancy 284

Supported Features in BNG Geo Redundancy 284

BNG Geo Redundancy Configuration Guidelines 285

Setting up BNG Subscriber Redundancy Group 287

Deployment Models for BNG Geo Redundancy 288

APPENDIX A

XML Support for BNG Features 289

AAA XML Support 289

DHCP XML Support 292

Control Policy XML Support 295

DAPS XML Support 298

PPPoE XML Support 300

Subscriber Database XML Support 302

APPENDIX B

RADIUS Attributes 307

RADIUS IETF Attributes 307

IETF Tagged Attributes on LAC 309

RADIUS Vendor-Specific Attributes 310

Vendor-Specific Attributes for Account Operations 315

RADIUS ADSL Attributes 315

RADIUS ASCEND Attributes 316

RADIUS Microsoft Attributes 317

RADIUS Disconnect-Cause Attributes 317

APPENDIX C

Action Handlers 323

APPENDIX D

BNG Use Cases and Sample Configurations 325

BNG over Pseudowire Headend 325

Sample Topology for BNG over Pseudowire Headend 325

Deployment Models for Subscribers on Pseudowire Headend 326

Residential Subscribers on Pseudowire Headend 326

Residential and Business Subscribers on Pseudowire Headend 328

Configuration and Verification of BNG over Pseudowire Headend 330

Sample Configurations for BNG over Pseudowire Headend 332

Dual-Stack Subscriber Sessions 334

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide, Release

5.2.x

ix

Contents

IP Address Assignment for Clients 334

Sample IPv6 Addressing and Configurations 335

IPv6 Address Mapping 335

CPE Configurations 335

DHCPv6 Server Configuration 336

Operation and Call Flow of Dual-Stack Sessions 336

Generic Call Flow of Dual-Stack Session 337

Detailed Call Flows - PPPoE Dual-Stack 339

Scenario 1: SLAAC-Based Address Assignment 339

Scenario 2: DHCPv6-Based Address Assignment 340

Detailed Call Flows - IPoE Dual-Stack 341

Scenario 1 - IPv4 Address-Family Starts First 341

Scenario 2 - IPv6 Address-Family Starts First 342

Sample Topology for Dual-Stack 343

Configuration Examples for Dual-Stack 343

Verification Steps for Dual-Stack 345

eBGP over PPPoE 346

Sample Topology for eBGP over PPPoE 346

Configuration and Verification of eBGP over PPPoE 347

Sample Configurations for eBGP over PPPoE 348

Routed Subscriber Sessions 354

Routed Subscriber Deployment Topology and Use Cases 354

Sample Configurations for Routed Subscriber Session 355

Verification of Routed Subscriber Session Configurations 357

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide,

Release 5.2.x

x

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 Preface contains these sections:

•Changes to This Document, page xi

•Obtaining Documentation and Submitting a Service Request, page xi

Changes to This Document

This table lists the technical changes made to this document since it was first released.

Table 1: Changes to This Document

SummaryDate

Republished with documentation updates for Cisco

IOS XR Release 5.2.2 features.

October 2014

Initial release of this document.July 2014

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 Broadband Network Gateway Configuration Guide, Release

5.2.x

xi

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide,

Release 5.2.x

xii

Preface

Obtaining Documentation and Submitting a Service Request

CHAPTER 1

New and Changed BNG Features

This table summarizes the new and changed feature information for the Cisco ASR 9000 Series Aggregation

Services Router Broadband Network Gateway Configuration Guide, and tells you where they are documented.

•New and Changed BNG Feature Information, page 1

New and Changed BNG Feature Information

Where DocumentedChanged in ReleaseDescriptionFeature

Establishing Subscriber

Sessions chapter:

•Geo Redundancy

Overview, on page 279

Refer Subscriber Commands

chapter in Cisco ASR 9000

Series Aggregation Services

Router Broadband Network

Gateway Command Reference,

for information on the

commands used for BNG Geo

Redundancy feature.

Release 5.2.2This feature was introduced.BNG Geo Redundancy

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide, Release

5.2.x

1

Where DocumentedChanged in ReleaseDescriptionFeature

Establishing Subscriber

Sessions chapter:

•Packet-triggered Routed

Subscriber Sessions, on

page 89

Refer IPoE Commands chapter

in Cisco ASR 9000 Series

Aggregation Services Router

Broadband Network Gateway

Command Reference, for

information on the commands

used for Packet-triggered

Routed Subscriber Sessions

feature.

Release 5.2.2This feature was introduced.Packet-triggered Routed

Subscriber Sessions

Establishing Subscriber

Sessions chapter:

•QoS on BNG Pseudowire

Headend, on page 173

Release 5.2.2QoS support was added for

BNG Pseudowire Headend

QoS on BNG Pseudowire

Headend

Configuring Subscriber

Features chapter:

•Randomization of Interim

Timeout of Sessions or

Services, on page 276

Refer Subscriber Commands

chapter in Cisco ASR 9000

Series Aggregation Services

Router Broadband Network

Gateway Command Reference,

for information on the

commands used for this feature.

Release 5.2.2New command was introduced

to support randomization of

interim timeout of subscriber

sessions or services

Randomization of Interim

Timeout of Subscriber Sessions

or Services

Broadband Network Gateway

Overview chapter:

•Hardware Requirements

for BNG, on page 11

Release 5.2.2BNG support was extended to

new line cards

Support for New Line Cards

Establishing Subscriber

Sessions chapter:

•BNG over Pseudowire

Headend , on page 173

Release 5.2.0This feature was introduced.BNG over Pseudowire Headend

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide,

Release 5.2.x

2

New and Changed BNG Features

New and Changed BNG Feature Information

Where DocumentedChanged in ReleaseDescriptionFeature

Establishing Subscriber

Sessions chapter:

•eBGP over PPPoE, on

page 172

Release 5.2.0This feature was introduced.eBGP over PPPoE

Configuring Authentication,

Authorization and Accounting

Functions chapter:

•Multi-Action Change of

Authorization, on page

45

Refer Control Policy

Commands and Subscriber

Commands chapters in Cisco

ASR 9000 Series Aggregation

Services Router Broadband

Network Gateway Command

Reference, for information on

the commands used for

MA-CoA feature.

Release 5.2.0This feature was introduced.Multi-Action Change of

Authorization (MA-CoA)

Configuring Subscriber

Features chapter:

•Outer VLAN Range, on

page 239

Refer BNG Interface

Commands chapter in Cisco

ASR 9000 Series Aggregation

Services Router Broadband

Network Gateway Command

Reference, for information on

the commands used for Outer

VLAN Range feature.

Release 5.2.0This feature was introduced.Outer VLAN Range

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide, Release

5.2.x

3

New and Changed BNG Features

New and Changed BNG Feature Information

Where DocumentedChanged in ReleaseDescriptionFeature

Deploying the Quality of

Service (QoS) chapter:

•RADIUS Based Policing

- QoS Shaper

Parameterization, on page

193

Refer Control Policy

Commands chapter in Cisco

ASR 9000 Series Aggregation

Services Router Broadband

Network Gateway Command

Reference, for information on

the commands used for QoS

Shaper Parameterization

feature.

Release 5.2.0This feature was introduced.QoS Shaper Parameterization

Configuring Authentication,

Authorization and Accounting

Functions chapter:

•User Authentication and

Authorization in the Local

Network, on page 50

Release 5.2.0This feature was introduced.User Authentication and

Authorization in the Local

Network

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide,

Release 5.2.x

4

New and Changed BNG Features

New and Changed BNG Feature Information

CHAPTER 2

Broadband Network Gateway Overview

This chapter provides an overview of the Broadband Network Gateway (BNG) functionality implemented

on the Cisco ASR 9000 Series Router.

Table 2: Feature History for Broadband Network Gateway Overview

ModificationRelease

Initial release of BNG.Release 4.2.0

•Understanding BNG, page 5

•BNG Architecture, page 6

•BNG Role in ISP Network Models, page 8

•BNG Packaging, page 9

•BNG Configuration Process, page 11

•Hardware Requirements for BNG, page 11

•BNG Interoperability, page 12

•BNG Smart Licensing, page 13

Understanding BNG

Broadband Network Gateway (BNG) is the access point for subscribers, through which they connect to the

broadband network. When a connection is established between BNG and Customer Premise Equipment (CPE),

the subscriber can access the broadband services provided by the Network Service Provide (NSP) or Internet

Service Provider (ISP).

BNG establishes and manages subscriber sessions. When a session is active, BNG aggregates traffic from

various subscriber sessions from an access network, and routes it to the network of the service provider.

BNG is deployed by the service provider and is present at the first aggregation point in the network, such as

the edge router. An edge router, like the Cisco ASR 9000 Series Router, needs to be configured to act as the

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide, Release

5.2.x

5

BNG. Because the subscriber directly connects to the edge router, BNG effectively manages subscriber access,

and subscriber management functions such as:

•Authentication, authorization and accounting of subscriber sessions

•Address assignment

•Security

•Policy management

•Quality of Service (QoS)

Some benefits of using BNG are:

•The BNG router not only performs the routing function but also communicates with authentication,

authorization, and accounting (AAA) server to perform session management and billing functions. This

makes the BNG solution more comprehensive.

•Different subscribers can be provided different network services. This enables the service provider to

customize the broadband package for each customer based on their needs.

BNG Architecture

The goal of the BNG architecture is to enable the BNG router to interact with peripheral devices (like CPE)

and servers (like AAA and DHCP), in order to provide broadband connectivity to subscribers and manage

subscriber sessions. The basic BNG architecture is shown in this figure.

Figure 1: BNG Architecture

The BNG architecture is designed to perform these tasks:

•Connecting with the Customer Premise Equipment (CPE) that needs to be served broadband services.

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide,

Release 5.2.x

6

Broadband Network Gateway Overview

BNG Architecture

•Establishing subscriber sessions using IPoE or PPPoE protocols.

•Interacting with the AAA server that authenticates subscribers, and keeps an account of subscriber

sessions.

•Interacting with the DHCP server to provide IP address to clients.

The four BNG tasks are briefly explained in the following sections.

Connecting with the CPE

BNG connects to the CPE through a multiplexer and Home Gateway (HG). The CPE represents the triple

play service in telecommunications, namely, voice (phone), video (set top box), and data (PC). The individual

subscriber devices connect to the HG. In this example, the subscriber connects to the network over a Digital

Subscriber Line (DSL) connection. Therefore, the HG connects into a DSL Access Multiplexer (DSLAM).

Multiple HGs can connect to a single DSLAM that sends the aggregated traffic to the BNG router. The BNG

router routes traffic between the broadband remote access devices (like DSLAM or Ethernet Aggregation

Switch) and the service provider network.

Establishing Subscriber Sessions

Each subscriber (or more specifically, an application running on the CPE) connects to the network by a logical

session. Based on the protocol used, subscriber sessions are classified into two types:

•PPPoE subscriber session—The PPP over Ethernet (PPPoE) subscriber session is established using the

point-to-point (PPP) protocol that runs between the CPE and BNG.

•IPoE subscriber session—The IP over Ethernet (IPoE) subscriber session is established using IP protocol

that runs between the CPE and BNG; IP addressing is done using the DHCP protocol.

Interacting with the RADIUS Server

BNG relies on an external Remote Authentication Dial-In User Service (RADIUS) server to provide subscriber

Authentication, Authorization, and Accounting (AAA) functions. During the AAA process, BNG uses RADIUS

to:

•authenticate a subscriber before establishing a subscriber session

•authorize the subscriber to access specific network services or resources

•track usage of broadband services for accounting or billing

The RADIUS server contains a complete database of all subscribers of a service provider, and provides

subscriber data updates to the BNG in the form of attributes within RADIUS messages. BNG, on the other

hand, provides session usage (accounting) information to the RADIUS server. For more information about

RADIUS attributes, see RADIUS Attributes, on page 307.

BNG supports connections with more than one RADIUS server to have fail over redundancy in the AAA

process. For example, if RADIUS server A is active, then BNG directs all messages to the RADIUS server

A. If the communication with RADIUS server A is lost, BNG redirects all messages to RADIUS server B.

During interactions between the BNG and RADIUS servers, BNG performs load balancing in a round-robin

manner. During the load balancing process, BNG sends AAA processing requests to RADIUS server A only

if it has the bandwidth to do the processing. Else, the request is send to RADIUS server B.

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide, Release

5.2.x

7

Broadband Network Gateway Overview

BNG Architecture

Interacting with the DHCP Server

BNG relies on an external Dynamic Host Configuration Protocol (DHCP) server for address allocation and

client configuration functions. BNG can connect to more than one DHCP server to have fail over redundancy

in the addressing process. The DHCP server contains an IP address pool, from which it allocates addresses

to the CPE.

During the interaction between BNG and the DHCP server, BNG acts as a DHCP relay or DHCP proxy.

As the DHCP relay, BNG receives DHCP broadcasts from the client CPE, and forwards the request to the

DHCP server.

As the DHCP proxy, BNG itself maintains the address pool by acquiring it from DHCP server, and also

manages the IP address lease. BNG communicates on Layer 2 with the client Home Gateway, and on Layer

3 with the DHCP server.

The DSLAM modifies the DHCP packets by inserting subscriber identification information. BNG uses the

identification information inserted by the DSLAM, as well as the address assigned by the DHCP server, to

identify the subscriber on the network, and monitor the IP address lease.

BNG Role in ISP Network Models

The role of BNG is to pass traffic from the subscriber to the ISP. The manner in which BNG connects to the

ISP depends on the model of the network in which it is present. There are two types of network models:

•Network Service Provider, on page 8

•Access Network Provider, on page 9

Network Service Provider

The following figure shows the topology of a Network Service Provider model.

Figure 2: Network Service Provider Model

In the Network Service Provider model, the ISP (also called the retailer) directly provides the broadband

connection to the subscriber. As shown in the above figure, BNG is at the edge router, and its role is to connect

to the core network through uplinks.

Cisco ASR 9000 Series Aggregation Services Router Broadband Network Gateway Configuration Guide,

Release 5.2.x

8

Broadband Network Gateway Overview

BNG Role in ISP Network Models

Page is loading ...

Cisco IOS XR Software Release 5.2 Configuration Guide

Cisco IOS XR Software Release 5.2 Configuration Guide

Related papers

Other documents