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Foreword xv
Preface xvii
Chapter 1 General Introduction 1
1.1 Communications Networks Today 1
1.1.1 Fundamental Networking Concepts 3
1.1.2 Layered Network Representation 5
1.1.3 Network Planes 6
1.2 Network Reliability 8
1.2.1 Definitions 9
1.2.2 Which Failures Can Occur? 12
1.2.3 Reliability Requirements for Various Users and Services 18
1.2.4 Measures to Increase Reliability 20
1.3 Different Phases in a Recovery Process 22
1.3.1 Recovery Cycle 23
1.3.2 Reversion Cycle 24
1.4 Performance of Recovery Mechanisms: Criteria 25
1.4.1 Scope of Failure Coverage 25
1.4.2 Recovery Time 26
1.4.3 Backup Capacity Requirements 26
1.4.4 Guaranteed Bandwidth 27
1.4.5 Reordering and Duplication 27
1.4.6 Additive Latency and Jitter 27
1.4.7 State Overhead 27
1.4.8 Scalability 27
1.4.9 Signaling Requirements 28
1.4.10 Stability 28
1.4.11 Notion of Recovery Class 28
1.5 Characteristics of Single-Layer Recovery Mechanisms 28
1.5.1 Backup Capacity Dedicated versus Shared 29
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1.5.2 Recovery Paths: Preplanned versus Dynamic 30
1.5.3 Protection versus Restoration 31
1.5.4 Global versus Local Recovery 32
1.5.5 Control of Recovery Mechanisms 34
1.5.6 Ring Networks versus Mesh Networks 35
1.5.7 Connection-Oriented versus Connectionless 36
1.5.8 Revertive versus Nonrevertive Mode 36
1.6 Multilayer Recovery 36
1.6.1 Sequential Approach 38
1.6.2 Integrated Approach 38
1.7 Conclusion 38
Chapter 2 SONET/SDH Networks 39
2.1 Introduction 40
2.1.1 Transmission Networks 40
2.1.2 Management of (Transmission) Networks 42
2.1.3 Structuring/Modeling Transmission Networks 43
2.1.4 Summary 45
2.2 SDH and SONET Networks 45
2.2.1 Introduction 45
2.2.2 Structure of SDH Networks 46
2.2.3 SDH Frame Structure: Overhead Bytes Relevant for
Network Recovery 48
2.2.4 SDH Network Elements 52
2.2.5 Summary 55
2.2.6 Differences between SONET and SDH 56
2.3 Operational Aspects 57
2.3.1 Fault Management Processes 58
2.3.2 Fault Detection and Propagation Inside a Network
Element 60
2.3.3 Fault Propagation and Notification on a Network Level 70
2.3.4 Automatic Protection Switching Protocol 74
2.3.5 Summary 80
2.4 Ring Protection 81
2.4.1 Multiplex Section–Shared Protection Ring 83
2.4.2 Multiplex Section–Dedicated Protection Ring 91
2.4.3 Subnetwork Connection Protection Ring 93
2.4.4 Ring Interconnection 93
2.4.5 Summary 105
2.4.6 Differences between SONET and SDH 106
2.5 Linear Protection 107
2.5.1 Multiplex Section Protection 107
2.5.2 Path Protection 108
2.5.3 Summary 113
viii Contents
2.6 Restoration 113
2.6.1 Protection versus Restoration 113
2.6.2 Summary 115
2.7 Case Study 115
2.8 Conclusion 127
2.9 Recommended Reference Work and Research-Related Topics 129
Chapter 3 Optical Networks 131
3.1 Evolution of the Optical Network Layer 132
3.1.1 Wavelength Division Multiplexing in the
Point-to-Point Optical Network Layer 132
3.1.2 An Optical Networking Layer with Optical Nodes 135
3.1.3 An Optical Network Layer Organized in Rings 135
3.1.4 Meshed Optical Networks 137
3.1.5 Adding Flexibility to the Optical Network Layer 139
3.2 The Optical Transport Network 139
3.2.1 Architectural Aspects and Structure of the Optical
Transport Network 139
3.2.2 Structure of the Optical Transport Module 142
3.2.3 Overview of the Standardization Work on the Optical
Transport Network 144
3.3 Fault Detection and Propagation 144
3.3.1 The Optical Network Overhead 145
3.3.2 Defects in the Optical Transport Network 152
3.3.3 OTN Maintenance Signals and Alarm Suppression 154
3.4 Recovery in Optical Networks 157
3.4.1 Recovery at the Optical Layer? 157
3.4.2 Standardization Work on Recovery in the Optical
Transport Network 158
3.4.3 Shared Risk Group 159
3.5 Recovery Mechanisms in Ring-Based Optical Networks 160
3.5.1 Multiplex Section Protection in Ring-Based Optical
Networks 163
3.5.2 Optical Channel Protection in Ring-Based Optical
Networks 166
3.5.3 OMS- versus OCh-Based Approach 170
3.5.4 Shared versus Dedicated Approach 171
3.5.5 Interconnection of Rings 173
3.6 Recovery Mechanisms in Mesh-Based Optical Networks 173
3.6.1 Protection 175
3.6.2 Protection in a WP Network versus Protection in
a VWP Network 176
3.6.3 Restoration 177
3.6.4 Protection versus Restoration 180
Contents ix
3.6.5 Protection Combined with Restoration 182
3.7 Ring-Based versus Mesh-Based Recovery Schemes 182
3.8 Availability 185
3.8.1 Availability Calculations 185
3.8.2 Availability: Some Observations 192
3.9 Recent Trends in Research 197
3.9.1 p-Cycles 197
3.9.2 Meta-Mesh Recovery Technique 199
3.9.3 Flexible Optical Networks 200
3.10 Conclusion 200
Chapter 4 IP Routing 203
4.1 IP Routing Protocols 204
4.1.1 Introduction 204
4.1.2 Distance Vector Routing Protocols Overview
(‘‘Bellman-Ford’’) 204
4.1.3 Link State Routing Protocols Overview 207
4.1.4 IP Routing: A Global versus Local Restoration
Mechanism? 213
4.2 Analysis of the IP Routing Recovery Cycle 214
4.2.1 Fault Detection and Characterization 214
4.2.2 Hold-Off Timer 214
4.2.3 Fault Notification Time 215
4.2.4 Computation of the Routing Table 215
4.2.5 An Example of IP Rerouting upon Link Failure 217
4.3 Failure Profile and Fault Detection 220
4.3.1 Failure Profiles 220
4.3.2 Failure Detection 222
4.3.3 Failure Characterization 224
4.3.4 Analysis of the Various Failure Types and Their
Impact on Traffic Forwarding 225
4.4 Dampening Algorithms 226
4.5 FIS Propagation (LSA Origination and Flooding) 229
4.5.1 LSA Origination Process 231
4.5.2 LSA Flooding Process 233
4.5.3 Time Estimate for the LSA Origination and
Flooding Process 237
4.6 Route Computation 237
4.6.1 Shortest Path Computation 238
4.6.2 The Dijkstra Algorithm 241
4.6.3 Shortest Path Computation Triggers 249
4.6.4 Routing Information Base Update 251
4.7 Temporary Loops during Network State Changes 252
4.7.1 Temporary Loops in the Case of a Link or Node Failure 253
x Contents
4.7.2 Temporary Loops Caused by a Restored Network
Element 257
4.8 Load Balancing 259
4.9 QoS during Failure 262
4.9.1 IP Traffic Engineering at Steady State 262
4.9.2 QoS Guarantee during Failure 264
4.10 Nonstop Forwarding: An Example with OSPF 266
4.10.1 Mode of Operation 267
4.10.2 Mode of Operation of the Restarting Router 267
4.10.3 Mode of Operation of the Restarting Router’s
Neighbors 269
4.10.4 Backward Compatibility 269
4.11 A Case Study with IS-IS 270
4.12 Summary 278
4.13 Algorithm Complexity 279
4.13.1 Definition of Algorithm Complexity 279
4.13.2 NP Complete Problem 284
4.14 Incremental Dijkstra 285
4.14.1 Motivation 285
4.14.2 History 287
4.14.3 Algorithm Description 287
4.14.4 iSPF Efficiency 293
4.15 Interaction between Fast IGP Convergence and NSF 293
4.16 Research-Related Topics 295
Chapter 5 MPLS Traffic Engineering Recovery Mechanisms 297
5.1 MPLS Traffic Engineering Refresher 298
5.1.1 Traffic Engineering in Data Networks 298
5.1.2 Terminology 301
5.1.3 MPLS Traffic Engineering Components 303
5.1.4 Notion of Preemption in MPLS Traffic Engineering 305
5.1.5 Motivations for Deploying MPLS Traffic Engineering 306
5.2 Analysis of the Recovery Cycle 307
5.2.1 Fault Detection Time 307
5.2.2 Hold-Off Timer 308
5.2.3 Fault Notification Time 308
5.2.4 Recovery Operation Time 309
5.2.5 Traffic Recovery Time 309
5.3 MPLS Traffic Engineering Global Default Restoration 310
5.3.1 Fault Signal Indication 310
5.3.2 Mode of Operation 311
5.3.3 Recovery Time 313
5.4 MPLS Traffic Engineering Global Path Protection 314
5.4.1 Mode of Operation 315
Contents xi
5.4.2 Recovery Time 316
5.5 MPLS Traffic Engineering Local Protection 316
5.5.1 Terminology 316
5.5.2 Principles of Local Protection Recovery Techniques 317
5.5.3 Local Protection: One-to-One Backup 318
5.5.4 Local Protection: ‘‘Facility Backup’’ 320
5.5.5 Properties of a Traffic Engineering LSP 325
5.5.6 Notification of Tunnel Locally Repaired 327
5.5.7 Signaling Extensions for MPLS Traffic Engineering Local
Protection 329
5.5.8 Two Strategies for Deploying MPLS Traffic
Engineering for Fast Recovery 329
5.6 Another MPLS Traffic Engineering Recovery Alternative 333
5.7 Load Balancing 334
5.8 Comparison of Global and Local Protection 336
5.8.1 Recovery Time 336
5.8.2 Scalability 336
5.8.3 Bandwidth Sharing Capability 340
5.8.4 Summary 343
5.9 Revertive versus Nonrevertive Modes 346
5.9.1 MPLS Traffic Engineering Global Default Restoration 346
5.9.2 MPLS Traffic Engineering Global Path Protection 347
5.9.3 MPLS Traffic Engineering Local Protection 347
5.10 Failure Profile and Fault Detection 348
5.10.1 MPLS-Specific Failure Detection Hello-Based Protocols 348
5.10.2 Requirements for an Accurate Failure Type
Characterization 349
5.10.3 Analysis of the Various Failure Types and Their
Impact on Traffic Forwarding 353
5.11 Case Studies 354
5.11.1 Case Study 1 354
5.11.2 Case Study 2 359
5.11.3 Case Study 3 362
5.12 Standardization 370
5.13 Summary 371
5.14 RSVP Signaling Extensions for MPLS TE Local Protection 372
5.14.1 SESSION-ATTRIBUTE Object 372
5.14.2 FAST-REROUTE Object 374
5.14.3 DETOUR Object 375
5.14.4 Route Record Object 376
5.14.5 Signaling a Protected Traffic Engineering LSP with
a Set of Constraints 378
5.14.6 Identification of a Signaled TE LSP 378
5.14.7 Signaling with Facility Backup 379
5.14.8 Signaling with One-to-One Backup 382
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5.14.9 Detour Merging 384
5.15 Backup Path Computation 385
5.15.1 Introduction 386
5.15.2 Requirements for Strict QoS Guarantees during Failure 386
5.15.3 Network Design Considerations 387
5.15.4 Notion of Bandwidth Sharing between Backup Paths 392
5.15.5 Backup Path Computation: MPLS TE Global Path
Protection 393
5.15.6 Backup Tunnel Path Computation: MPLS TE Fast
Reroute Facility Backup 397
5.15.7 Backup Tunnel Path Computation with MPLS TE Fast
Reroute One-to-One Backup 419
5.15.8 Summary 421
5.16 Research-Related Topics 422
Chapter 6 Multilayer Networks 423
6.1 ASON/G-MPLS Networks 424
6.1.1 The ASON/ASTN Framework 424
6.1.2 Protocols for Implementing a Distributed Control Plane 426
6.1.3 Overview of Control Plane Architectures (Overlay, Peer,
Augmented) 432
6.2 Generic Multilayer Recovery Approaches 437
6.2.1 Why Multilayer Recovery? 438
6.2.2 Single-Layer Recovery Schemes in Multilayer Networks 439
6.2.3 Static Multilayer Recovery Schemes 444
6.2.4 Dynamic Multilayer Recovery 457
6.2.5 Summary 464
6.3 Case Studies 464
6.3.1 Optical Restoration and MPLS Traffic Engineering
Fast Reroute 465
6.3.2 SONET/SDH Protection and IP Routing 469
6.3.3 MPLS Traffic Engineering Fast Reroute (Link Protection)
and IP Rerouting Fast Convergence 471
6.4 Conclusion 476
Bibliography 479
List of Figure Sources 491
Index 497
The range of services and applications that rely on communication networks is
impressive: business critical communication, phone calls, emails, home banking,
and even watching TV or listening to music, and this is undoubtedly just the very
beginning. Because our professional and private life is more and more dependent on
these communication services, the repercussions of a service interruption are severe.
Hence, network reliability has received intensified interest from service providers
and enterprises during the past few years to provide highly reliable networks, and
this trend is expected to continue in the future. We have dedicated a very significant
amount of our time during those past years to understanding the challenges of
network recovery and the existing and new requirements of operators and enterprises
to develop new technologies, standards, and network designs. We found that
the time was overdue to devote a book to network recovery, and this book is the
result of our experience.
Network recovery is undoubtedly a complex, fascinating, and rapidly evolving
topic, essentially because of its truly multi-dimensional nature. Indeed, although the
immediate criteria that comes to mind is convergence time (i.e., time to recover the
affected traffic), which is only one among several other aspects we should consider.
Throughout this book, we explore all the other dimensions that lead to choosing a
particular recovery mechanism and elect a specific network recovery design: Does
the backup path offer a similar quality of service in terms of bandwidth and propagation
delay? What are the consequences of maintaining extra network states? Is there
any potential impact on the network stability as a result of trying to restore the traffic
upon failure and to potentially reuse restored routes? What are the implications of
adding some extra complexity in the network both in terms of engineering and network
operation management? And finally, what are the cost implications in terms of
additional required equipment and network backup bandwidth? All the above criteria
must be carefully evaluated, because they lead to various trade-offs during the
decision-making process of network recovery design. Moreover, one must admit
that the emergence of new services and applications have resulted in some increased
complexity in terms of hardware and software equipment (indeed, it is not unusual
to see a software program with millions of code lines!). As a result, the potential for
possible failures drastically increased during the past several years, both in diversity
and identification complexity. Furthermore, both network convergence and the
rapid growth of new applications such as Voice or Video over IP led to building
networks involving several layers. Each layer offers a large set of recovery mechanisms,
which ineluctably interact when deployed at multiple layers. Hence, we
devote an entire chapter to the subject of inter-layer recovery, with the objective
of highlighting the potential interactions between multiple recovery mechanisms
operating at different layers.
کتاب بازیابی شبکه (Network Recovery) اثر مورگان کافمن به زبان انگلیسی
