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Internet routing architectures
Personal Author:
2nd ed.
Publication Information:
Indianapolis, Ind. : Cisco Press, 2000
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30000010053819 TK5105.543 H34 2000 Open Access Book
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The industry's leading resource for Internet routing solutions and scenarios

Explore the functions, attributes, and applications of BGP-4, the de facto interdomain routing protocol, through practical scenarios and configuration examples Learn the contemporary Internet structure and understand how to evaluate a service provider in dealing with routing and connectivity issues Master the addressing techniques--including Classless Interdomain Routing (CIDR)--that are demanded today to facilitate the Internet's rapid and continuing growth Develop optimal routing policies--redundancy, traffic balancing, symmetry, and stability--for your network Learn how to seamlessly integrate your intradomain and interdomain routing and manage large and growing autonomous systems

Internet Routing Architectures, Second Edition, explores the ins and outs of interdomain routing network designs with emphasis on BGP-4 (Border Gateway Protocol Version 4)--the de facto interdomain routing protocol.

Using a practical, example-oriented approach, this comprehensive resource provides you with real solutions for ISP connectivity issues. You will learn how to integrate your network on the global Internet and discover how to build large-scale autonomous systems. You will also learn to control expansion of interior routing protocols using BGP-4, design sound and stable networks, configure the required policies using Cisco IOS Software, and explore routing practices and rules on the Internet.


Author Notes

Danny McPherson is currently Director of Architecture, Office of the CTO, at Amber Networks. Formerly, he held technical leadership positions with four Internet service providers (Qwest, GTE Internetworking, Genuity, and internetMCI), where he was responsible for network and product architecture, routing design, peering, and other business- and policy-related issues. McPherson is an active contributor to the Internet Engineering Task Force (IETF), as well as several other standards bodies. He is an acknowledged expert in Internet architecture and routing protocols.

Sam Halabi is the Vice President of Business Development at Extreme Networks, responsible for defining the company's service provider product and business strategy. Recognized as one of the industry's foremost experts in the Service Provider market, Halabi has more than 15 years of experience in complex routing protocols and the design of large-scale IP networks. He is the author of the best-selling book Internet Routing Architectures , a definitive resource for internetworking design alternatives and solutions.

Halabi has held various marketing positions with leading data communications companies, including Cisco Systems, 3Com and Pluris. While at Cisco Systems, he led the Company's IP Carrier marketing efforts.

An active member in the industry, Halabi serves as a board member of the Optical Internetworking Forum and of the MPLS Forum.

Table of Contents

Part I The Contemporary Internetp. 3
Chapter 1 Evolution of the Internetp. 5
Origins and Recent History of the Internetp. 5
The Internet Todayp. 8
NSFNET Solicitationsp. 10
Network Access Pointsp. 10
What Is a NAP?p. 11
NAP Manager Solicitationp. 11
Federal Internet eXchangep. 12
Commercial Internet eXchangep. 12
Current Physical Configurations at the NAPp. 13
An Alternative to NAPs: Direct Interconnectionsp. 14
Routing Arbiter Projectp. 14
The Very High Speed Backbone Network Servicep. 18
Transitioning the Regional Networks from the NSFNETp. 21
NSF Solicits NIS Managersp. 22
Network Information Servicesp. 23
Creation of the InterNICp. 23
Directory and Database Servicesp. 23
Registration Servicesp. 25
NIC Support Servicesp. 25
Other Internet Registriesp. 25
ARINp. 26
APNICp. 27
Internet Routing Registriesp. 27
The Once and Future Internetp. 28
Next-Generation Internet Initiativep. 28
Internet2p. 30
Abilenep. 31
Looking Aheadp. 32
Frequently Asked Questionsp. 34
Referencesp. 35
Chapter 2 ISP Services and Characteristicsp. 37
ISP Servicesp. 37
Dedicated Internet Accessp. 37
Frame Relay and ATM Internet Accessp. 38
Dialup Servicesp. 39
Digital Subscriber Linep. 40
Cable Modemsp. 41
Dedicated Hosting Servicesp. 41
Other ISP Servicesp. 42
ISP Service Pricing, Service-Level Agreements, and Technical Characteristicsp. 42
ISP Service Pricingp. 42
Service-Level Agreementsp. 43
ISP Backbone Selection Criteriap. 43
Demarcation Pointp. 50
Looking Aheadp. 53
Frequently Asked Questionsp. 54
Chapter 3 IP Addressing and Allocation Techniquesp. 57
History of Internet Addressingp. 57
Basic IP Addressingp. 57
Basic IP Subnettingp. 60
VLSMsp. 62
IP Address Space Depletionp. 65
IP Address Allocationp. 66
Classless Interdomain Routingp. 67
Private Addressing and Network Address Translationp. 79
IP Version 6p. 82
Looking Aheadp. 86
Frequently Asked Questionsp. 87
Referencesp. 89
Part II Routing Protocol Basicsp. 91
Chapter 4 Interdomain Routing Basicsp. 93
Overview of Routers and Routingp. 93
Basic Routing Examplep. 94
Routing Protocol Conceptsp. 96
Distance Vector Routing Protocolsp. 96
Link-State Routing Protocolsp. 99
Segregating the World into Autonomous Systemsp. 101
Static Routing, Default Routing, and Dynamic Routingp. 101
Autonomous Systemsp. 102
Looking Aheadp. 107
Frequently Asked Questionsp. 108
Referencesp. 109
Chapter 5 Border Gateway Protocol Version 4p. 111
How BGP Worksp. 112
BGP Message Header Formatp. 115
BGP Neighbor Negotiationp. 116
Finite State Machine Perspectivep. 118
Notification Messagep. 120
Keepalive Messagep. 122
Update Message and Routing Informationp. 122
BGP Capabilities Negotiationp. 127
Multiprotocol Extensions for BGPp. 128
TCP MD5 Signature Optionp. 129
Looking Aheadp. 131
Frequently Asked Questionsp. 132
Referencesp. 133
Part III Effective Internet Routing Designsp. 135
Chapter 6 Chapter Tuning BGP Capabilitiesp. 137
Building Peer Sessionsp. 137
Physical Versus Logical Connectionsp. 139
Obtaining an IP Addressp. 140
Authenticating the BGP Sessionp. 140
BGP Continuity Inside an ASp. 141
Synchronization Within an ASp. 142
Sources of Routing Updatesp. 144
Injecting Information Dynamically into BGPp. 144
Injecting Information Statically into BGPp. 147
Origin of Routesp. 148
An Example of Static Versus Dynamic Routing: Mobile Networksp. 150
Overlapping Protocols: Backdoorsp. 150
The Routing Process Simplifiedp. 152
BGP Routes: Advertisement and Storagep. 153
The BGP Routing Information Basesp. 154
Routes Received from Peersp. 155
Input Policy Enginep. 155
Routes Used by the Routerp. 155
Output Policy Enginep. 156
Routes Advertised to Peersp. 156
Sample Routing Environmentp. 156
BGP Decision Process Summaryp. 158
Controlling BGP Routesp. 159
BGP Path Attributesp. 160
NEXT_HOP Behavior on Multiaccess Mediap. 172
NEXT_HOP Behavior Over Nonbroadcast Multiaccess Mediap. 173
Use of next-hop-self versus Advertising DMZp. 174
Using Private ASsp. 175
AS_PATH and Route Aggregation Issuesp. 177
AS_PATH Manipulationp. 178
Route Filtering and Attribute Manipulationp. 180
Inbound and Outbound Filteringp. 181
The Route Filtering and Manipulation Processp. 182
Peer Groupsp. 190
BGP-4 Aggregationp. 192
Aggregate Only, Suppressing the More-Specific Routesp. 192
Aggregate Plus More-Specific Routesp. 193
Aggregate with a Subset of the More-Specific Routesp. 195
Loss of Information Inside Aggregatesp. 196
Changing the Attributes of the Aggregatep. 196
Forming the Aggregate Based on a Subset of the More-Specific Routesp. 196
Looking Aheadp. 197
Frequently Asked Questionsp. 199
Referencesp. 201
Chapter 7 Redundancy, Symmetry, and Load Balancingp. 203
Redundancyp. 203
Geographical Restrictions Pressurep. 204
Setting Default Routesp. 205
Symmetryp. 210
Load Balancingp. 210
Specific Scenarios: Designing Redundancy, Symmetry, and Load Balancingp. 212
Scenario 1 Single-Homingp. 213
Scenario 2 Multihoming to a Single Providerp. 213
Scenario 3 Multihoming to Different Providersp. 223
Scenario 4 Customers of the Same Provider with a Backup Linkp. 228
Scenario 5 Customers of Different Providers with a Backup Linkp. 231
Looking Aheadp. 236
Frequently Asked Questionsp. 237
Referencesp. 239
Chapter 8 Controlling Routing Inside the Autonomous Systemp. 241
Interaction of Non-BGP Routers with BGP Routersp. 241
Injecting BGP into the IGPp. 241
Following Defaults Inside an ASp. 242
BGP Policies Conflicting with Internal Defaultsp. 244
Defaults Inside the AS: Primary/Backup BGP Policyp. 244
Defaults Inside the AS: Other BGP Policiesp. 250
Policy Routingp. 252
Policy Routing Based on Traffic Sourcep. 252
Policy Routing Based on Traffic Source/Destinationp. 253
Policy Routing Defaults to Dynamic Routingp. 254
Other Applications of Policy Routingp. 255
Looking Aheadp. 257
Frequently Asked Questionsp. 258
Chapter 9 Controlling Large-Scale Autonomous Systemsp. 261
Route Reflectorsp. 261
Internal Peers Without Route Reflectorsp. 262
Internal Peers with Route Reflectorsp. 263
Naming Conventions and Rules of Operationp. 264
Redundancy Issues and Multiple Route Reflectors in an ASp. 265
Route Reflection Topology Modelsp. 266
Route Reflectors and Peer Groupsp. 269
Confederationsp. 271
Confederation Drawbacksp. 273
Route Exchange and BGP Decisions with Confederationsp. 274
Recommended Confederation Designp. 274
Confederations Versus Route Reflectorsp. 275
Controlling IGP Expansionp. 275
Segmenting the AS with Multiple Regions Separated by IBGPp. 277
Segmenting the AS with Multiple Regions Separated by EBGPp. 279
Looking Aheadp. 283
Frequently Asked Questionsp. 284
Referencesp. 285
Chapter 10 Designing Stable Internetsp. 287
Route Instabilities on the Internetp. 287
IGP Instabilityp. 287
Faulty Hardwarep. 288
Software Problemsp. 288
Insufficient CPU Powerp. 288
Insufficient Memoryp. 289
Network Upgrades and Routine Maintenancep. 289
Human Errorp. 290
Link Congestionp. 290
BGP Stability Featuresp. 290
Controlling Route and Cache Invalidationp. 291
BGP Route Refreshp. 291
Route Dampeningp. 292
Looking Aheadp. 296
Frequently Asked Questionsp. 297
Part IV Internet Routing Device Configurationp. 299
Chapter 11 Configuring Basic BGP Functions and Attributesp. 301
Building Peering Sessionsp. 301
Route Filtering and Attribute Manipulationp. 308
BGP Route Mapsp. 308
Prefix Listsp. 310
Identifying and Filtering Routes Based on the NLRIp. 312
Identifying and Filtering Routes Based on the AS_PATHp. 315
Peer Groupsp. 316
Sources of Routing Updatesp. 318
Injecting Information Dynamically into BGPp. 318
Injecting Information Statically into BGPp. 325
Overlapping Protocols: Backdoorsp. 326
BGP Attributesp. 328
The NEXT_HOP Attributep. 331
The AS_PATH Attributep. 332
The LOCAL_PREF Attributep. 335
The MULTI_EXIT_DISC Attributep. 337
The COMMUNITY Attributep. 340
BGP-4 Aggregationp. 342
Aggregate Only, Suppressing the More-Specificp. 343
Aggregate Plus More-Specific Routesp. 346
Aggregate with a Subset of the More-Specific Routesp. 350
Loss of Information Inside Aggregatesp. 354
Changing the Aggregate's Attributesp. 357
Forming the Aggregate Based on a Subset of Specific Routesp. 359
Looking Aheadp. 361
Chapter 12 Configuring Effective Internet Routing Policiesp. 365
Redundancy, Symmetry, and Load Balancingp. 365
Dynamically Learned Defaultsp. 365
Statically Set Defaultsp. 367
Multihoming to a Single Providerp. 370
Multihoming to Different Providersp. 384
Customers of the Same Provider with a Backup Linkp. 388
Customers of Different Providers with a Backup Linkp. 391
Following Defaults Inside an ASp. 395
BGP Policies Conflicting with the Internal Defaultp. 398
Policy Routingp. 411
Route Reflectorsp. 415
Confederationsp. 419
Controlling Route and Cache Invalidationp. 424
BGP Soft Reconfigurationp. 425
Outbound Soft Reconfigurationp. 425
Inbound Soft Reconfigurationp. 425
BGP Route Refreshp. 429
BGP Outbound Request Filter Capabilityp. 431
Route Dampeningp. 432
Looking Aheadp. 435
Part V Appendixesp. 439
Appendix A BGP Command Referencep. 441
Appendix B References for Further Studyp. 449
Interesting Organizationsp. 449
Research and Educationp. 449
Miscellaneousp. 449
Booksp. 450
TCP/IP-Related Sourcesp. 450
Routing-Related Sourcesp. 450
Internet Request For Commentsp. 450
Appendix C BGP Outbound Route Filter (ORF)p. 455
When to Use BGP ORFp. 455
Configurationp. 456
Enabling the BGP ORF Capability as Send-Modep. 456
Enabling the BGP ORF Capability as Receive-Modep. 456
Ensuring Backward Compatibility of the Old Knobsp. 457
EXEC Commandsp. 457
Pushing Out A Prefix List and Receiving a Route Refresh from a Neighborp. 457
Displaying the Prefix List Received from a Neighborp. 458
Displaying Changes to the Neighbor BGP Tablep. 458
Closing Remarksp. 458
Appendix D Multiprotocol BGP (MBGP)p. 461
The Motivation Behind the New Command-Line Interfacep. 461
Organizing Command Groups in the New Configurationp. 462
Activatep. 464
Old Stylep. 464
AF Stylep. 464
Networkp. 465
Old Stylep. 465
AF Stylep. 465
Peer Groupsp. 465
Old Stylep. 466
AF Stylep. 466
Route Mapsp. 466
Old Stylep. 466
AF Stylep. 467
Redistributionp. 468
Old Stylep. 468
AF Stylep. 468
Route Reflectorp. 469
Old Stylep. 469
AF Stylep. 469
Aggregationp. 469
Old Stylep. 470
AF Stylep. 470
List of BGP Commandsp. 470
Upgrading to the AF Stylep. 472
Referencesp. 473
Indexp. 475