The Complete IS-IS Routing Protocol

Contents......Page 9
Foreword......Page 7
Credits and Thanks......Page 8
1.1 Motivation......Page 16
1.2.1 DECNET Phase V......Page 17
1.2.2 NSFNet Phase I......Page 18
1.2.3 OSPF......Page 19
1.2.4 NLSP......Page 20
1.2.6 IETF ISIS-WG......Page 21
1.3 Sample Topology, Figures and Style......Page 22
2 Router Architecture......Page 25
2.1 Architecture and the Global Routing Paradigm......Page 26
2.2 General Router Model......Page 29
2.3 Routing and Forwarding Tables......Page 31
2.3.1 Forwarding Plane Architectures......Page 32
2.3.2 Control Plane Architectures......Page 35
2.4 Router Technology Examples......Page 40
2.4.1 Cisco 7500 Series......Page 41
2.4.2 Cisco 7500 Series + VIP Processors......Page 43
2.4.3 Cisco GSR Series......Page 44
2.4.5 Juniper Networks M-Series Routers......Page 45
2.5 Conclusion......Page 47
3.1 Common Properties of Command Line Interfaces (CLI)......Page 49
3.1.1 Operational Mode......Page 50
3.1.2 Configuration Mode......Page 53
3.1.4 Debugging......Page 54
3.1.7 Logging......Page 55
3.2.1 Logging into the System, Authentication, Privilege Level......Page 56
3.2.2 IS-IS-related Show Commands......Page 57
3.2.3 Interface Name-space......Page 58
3.2.4 Changing Router Configuration......Page 61
3.2.6 Troubleshooting Tools......Page 64
3.2.7 Routing Policy and Filtering of Routes......Page 69
3.3 Juniper Networks JUNOS CLI......Page 70
3.3.1 Logging into the System and Authentication......Page 71
3.3.2 IS-IS-related Show Commands......Page 73
3.3.3 Interface Name-space......Page 74
3.3.4 IS-IS-related Configuration Commands......Page 77
3.3.5 Changing the Configuration......Page 79
3.3.6 Activating a Configuration......Page 82
3.3.7 Troubleshooting Tools......Page 83
3.3.8 Routing Policy......Page 87
3.4 Conclusion......Page 91
4.1 IS-IS and the OSI Reference Model......Page 93
4.2 Areas......Page 97
4.3 Levels......Page 99
4.3.1 IS-IS Routing Hierarchy Rule......Page 100
4.3.2 Route Leaking Between Levels......Page 101
4.4 Area Migration Scenarios......Page 104
4.4.3 Renumbering Areas......Page 106
4.5 Local SPF Computation......Page 108
4.6.1 IP Addressing......Page 110
4.6.2 IP Addressing Model......Page 112
4.6.3 OSI Addressing......Page 114
4.6.5 Configuring NETs......Page 118
4.7 Names, System-, LAN- and LSP-IDs......Page 119
4.8 Summary......Page 121
5.1 Hello Message Encoding......Page 123
5.1.1 LAN Hello Messages......Page 125
5.1.2 Point-to-point Hello Messages......Page 128
5.2 MTU Check......Page 130
5.3 Handshaking......Page 133
5.3.1 The 3-way Handshake on LAN Circuits......Page 134
5.3.2 The 2-way Handshake on Point-to-point Circuits......Page 137
5.3.3 The 3-way Handshake on Point-to-point Circuits......Page 142
5.4 Sub-net Checking......Page 145
5.5 Finite State Machine......Page 147
5.6.1 IGP Hellos......Page 149
5.6.3 Bi-directional Fault Detection (BFD)......Page 151
5.7 Summary......Page 154
6.1 Distributed Databases......Page 155
6.2 Local Computation......Page 158
6.3 LSPs and Revision Control......Page 160
6.3.1 Sequence Numbers......Page 161
6.3.3 Periodic Refreshes......Page 163
6.3.4 Link-state PDUs......Page 166
6.4 Flooding......Page 178
6.4.1 Is Flooding Harmful?......Page 179
6.4.2 Mesh-Groups......Page 182
6.5 Network-wide Purging of LSPs......Page 186
6.5.1 DIS Election......Page 187
6.5.2 Expiration of LSPs......Page 188
6.6 Flow Control and Throttling of LSPs......Page 189
6.6.1 LSP-transmit-interval......Page 190
6.6.2 LSP-generation-interval......Page 192
6.6.3 Retransmission Interval......Page 195
6.7 Conclusion......Page 196
7.1.1 The Self-synchronization Problem......Page 197
7.1.3 Applying Jitter to Timers......Page 199
7.2.1 The N[sup(2)] Problem......Page 200
7.2.2 Pseudonode Representation......Page 202
7.2.3 Pseudonode ID Selection......Page 205
7.2.4 Link-state Database Modelling......Page 207
7.2.5 Pseudonode Suppression on p2p LANs......Page 210
7.3 DIS and DIS Election Procedure......Page 213
7.3.1 Pre-emption......Page 214
7.3.2 Purging......Page 215
7.3.3 DIS Redundancy......Page 216
7.4 Summary......Page 217
8.1 Why Synchronize Link-state Databases?......Page 219
8.2 Synchronizing Databases on Broadcast LAN Circuits......Page 222
8.3 Synchronizing Databases on p2p Links......Page 230
8.4 Periodic Synchronization on p2p Circuits......Page 232
8.5 Conclusion......Page 236
9.1 Fragmentation and the OSI Reference Model......Page 237
9.2 The Too-small MTU Problem for IP......Page 241
9.3 The Too-small MTU Problem for IS-IS......Page 244
9.4.1 Hellos (IIHs)......Page 248
9.4.2 Sequence Number Packets (SNPs)......Page 250
9.4.3 Link-state Packets (LSPs)......Page 254
9.5 Summary......Page 259
10.1 Route Calculation......Page 260
10.2.1 Working Principle......Page 261
10.2.2 Example......Page 262
10.2.3 Pseudonode Processing......Page 267
10.3 SPF Calculation Diversity......Page 270
10.3.1 Full SPF Run......Page 271
10.3.2 Partial SPF Run......Page 280
10.3.3 Incremental SPF Run......Page 283
10.4.1 BGP Recursion and Route Dependency......Page 286
10.4.2 BGP Route Selection......Page 287
10.5.1 Flat Forwarding Table......Page 289
10.5.2 Hierarchical Forwarding Table......Page 291
10.6 Conclusion......Page 292
11.1.1 Current Software Maturation Models......Page 293
11.1.2 Ramifications of Non-extensible Routing Protocols......Page 295
11.1.3 What Does it Mean When a Routing Protocol Is Called Extensible?......Page 296
11.2 Analysis of OSPF Extensibility......Page 297
11.3.1 TLV Format......Page 301
11.3.2 TLV Encoding......Page 303
11.3.3 Sub-TLVs......Page 305
11.3.4 TLV Sanity Checking......Page 307
11.4 Conclusion......Page 311
12.1 Old-style Topology (IS-Reach) Information......Page 312
12.2.1 Internal IP Reachability TLV #128......Page 315
12.2.2 Protocols Supported TLV #129......Page 318
12.2.3 External IP Reachability TLV #130......Page 320
12.2.4 Inter-Domain Information Type TLV #131......Page 324
12.2.5 Interface Address TLV #132......Page 325
12.2.6 IP Authentication TLV #133......Page 328
12.3 New-style Topology (IS-Reach) Information......Page 329
12.3.1 Automatic Metric Calculation......Page 330
12.3.2 Static Metric Setting......Page 331
12.4 New-style Topology (IP-Reach) Information......Page 335
12.5 Old-, New-style Interworking Issues......Page 338
12.6 Domain-wide Prefix Distribution......Page 340
12.6.1 Leaking Level-2 Prefixes into Level 1......Page 342
12.6.2 Leaking Level-1 External Prefixes into Level 2......Page 348
12.6.3 Use of Admin Tags for Leaking Prefixes......Page 350
12.7 Conclusion......Page 355
13.1 Dynamic Hostnames......Page 356
13.2.1 Simple Text Authentication......Page 362
13.2.3 Weaknesses......Page 364
13.2.4 Point-to-Point Interfaces......Page 366
13.2.5 Migration Strategy......Page 367
13.2.6 Running Authentication Using IOS......Page 369
13.2.7 Running Authentication Using JUNOS......Page 372
13.2.8 Interoperability......Page 375
13.3 Checksums for Non-LSP PDUs......Page 378
13.3.1 PDUs Missing Checksum?......Page 379
13.4 Ipv6 Extensions......Page 381
13.4.1 IOS Configuration......Page 384
13.4.2 JUNOS Configuration......Page 385
13.4.3 Deployment Scenarios......Page 387
13.5 Multi Topology Extensions......Page 390
13.5.1 JUNOS Configuration......Page 394
13.5.2 IOS Configuration......Page 397
13.5.3 Summary and Conclusion......Page 398
13.6 Graceful Restart......Page 399
13.7 Summary......Page 402
14.1 Traffic Engineering by IGP Metric Tweaking......Page 403
14.2 Traffic Engineering by Layer-2 Overlay Networks......Page 405
14.3.1 Introduction to MPLS......Page 412
14.4.1 RSVP-TE......Page 418
14.4.2 Simple Traffic Engineering with RSVP-TE......Page 419
14.4.3 LDP......Page 427
14.5 Complex Traffic Engineering by CSPF Computations......Page 432
14.6 LDP over RSVP-TE Tunnelling......Page 438
14.7 Forwarding Adjacencies......Page 443
14.8 Diffserv Aware Traffic Engineering......Page 445
14.9 Changed IS-IS Flooding Dynamics......Page 446
14.10 Conclusion......Page 447
15.1 Methodology......Page 448
15.2 Tools......Page 450
15.2.1 Show Commands......Page 451
15.2.2 Debug Logs......Page 458
15.2.3 Configuration File......Page 461
15.2.4 Network Analyzers......Page 464
15.3.1 Broken IS-IS Adjacency......Page 469
15.3.2 Injecting Full Internet Routes into IS-IS......Page 478
15.4 Summary......Page 483
16.1 Topology and Reachability Information......Page 484
16.2.1 Flooding......Page 488
16.2.2 SPF Stress......Page 489
16.2.3 Forwarding State Change Stress......Page 490
16.2.4 CPU and Memory Usage......Page 492
16.3.1 Separate Topology and IP Reachability Data......Page 493
16.3.3 Avoid LSP Fragmentation......Page 494
16.3.4 Reduce Background Noise......Page 497
16.3.5 Rely on the Link-layer for Fault Detection......Page 498
16.3.6 Simple Loopback IP Address to System-ID Conversion Schemes......Page 499
16.3.7 Align Throttling Timers Based on Global Network Delay......Page 501
16.3.8 Single Level Where You Can – Multi-level Where You Must......Page 502
16.3.9 Do Not Rely on Default Routes......Page 506
16.3.10 Use Wide-metrics Only......Page 507
16.3.12 Turn on HMAC-MD5 Authentication......Page 508
16.4 Conclusion......Page 510
17.1 Who Should Evolve IS-IS?......Page 512
17.2 G-MPLS......Page 513
17.2.1 Problems in the Optical Network Today......Page 514
17.2.3 Overlay (UNI) G-MPLS Model......Page 515
17.2.4 Peer G-MPLS Model......Page 518
17.2.5 IS-IS G-MPLS Extensions......Page 522
17.2.6 G-MPLS Summary......Page 523
17.3 Multi-level (8-level) IS-IS......Page 524
17.4 Extended Fragments......Page 527
17.5 iBGP Peer Auto-discovery......Page 529
17.6 Capability Announcement......Page 532
17.7 Conclusion......Page 533
B......Page 535
C......Page 536
D......Page 538
G......Page 539
I......Page 540
L......Page 542
N......Page 543
R......Page 544
S......Page 545
T......Page 546
Y......Page 548