1 INTRODUCTION 1
1.1 DEFINITION OF A DISTRIBUTED SYSTEM 2
1.2 GOALS 3
1.2.1 Making Resources Accessible 3
1.2.2 Distribution Transparency 4
1.2.3 Openness 7
1.2.4 Scalability 9
1.2.5 Pitfalls 16
1.3 TYPES OF DISTRIBUTED SYSTEMS 17
1.3.1 Distributed Computing Systems 17
1.3.2 Distributed Information Systems 20
1.3.3 Distributed Pervasive Systems 24
1.4 SUMMARY 30
2 ARCHITECTURES 33
2.1 ARCHITECTURAL STYLES 34
2.2 SYSTEM ARCHITECTURES 36
2.2.1 Centralized Architectures 36
2.2.2 Decentralized Architectures 43
2.2.3 Hybrid Architectures 52
2.3 ARCHITECTURES VERSUS MIDDLEWARE 54
2.3.1 Interceptors 55
2.3.2 General Approaches to Adaptive Software 57
2.3.3 Discussion 58
2.4 SELF-MANAGEMENT IN DISTRIBUTED SYSTEMS 59
2.4.1 The Feedback Control Model 60
2.4.2 Example：Systems Monitoring with Astrolabe 61
2.4.3 Example：Differentiating Replication Strategies in Globule 63
2 4.4 Example：Automatic Component Repair Management in Jade 65
2.5 SUMMARY 66
3 PROCESSES 69
3.1 THREADS 70
3.1.1 Introduction to Threads 70
3.1.2 Threads in Distributed Systems 75
3.2 VIRTUALIZATION 79
3.2.1 The Role of Virtualization in Distributed Systems 79
3.2.2 Architectures of Virtual Machines 80
3.3 CLIENTS 82
3.3.1 Networked User Interfaces 82
3.3.2 Client-Side Software for Distribution Transparency 87
3.4 SERVERS 88
3.4.1 General Design Issues 88
3.4.2 Server Clusters 92
3.4.3 Managing Server Clusters 98
3.5 CODE MIGRATION 103
3.5.1 Approaches to Code Migration 103
3.5.2 Migration and Local Resources 107
3.5.3 Migration in Heterogeneous Systems 110
3.6 SUMMARY 112
4 COMMUNICATION 115
4.1 FUNDAMENTALS 116
4.1.1 Layered Protocols 116
4.1.2 Types of Communication 124
4.2 REMOTE PROCEDURE CALL 125
4.2.1 Basic RPC Operation 126
4.2.2 Parameter Passing 130
4.2.3 Asynchronous RPC 134
4.2.4 Example：DCE RPC 135
4.3 MESSAGE-ORIENTED COMMUNICATION 140
4.3.1 Message-Oriented Transient Communication 141
4.3.2 Message-Oriented Persistent Communication 145
4.3.3 Example：IBM's WebSphere Message-Queuing System 152
4.4 STREAM-ORIENTED COMMUNICATION 157
4.4.1 Support for Continuous Media 158
4.4.2 Streams and Quality of Service 160
4.4.3 Stream Synchronization 163
4.5 MULTICAST COMMUNICATION 166
4.5.1 Application-Level Multicasting 166
4.5.2 Gossip-Based Data Dissemination 170
4.6 SUMMARY 175
5 NAMING 179
5.1 NAMES,IDENTIFIERS,AND ADDRESSES 180
5.2 FLAT NAMING 182
5.2.1 Simple Solutions 183
5.2.2 Home-Based Approaches 186
5.2.3 Distributed Hash Tables 188
5.2.4 Hierarchical Approaches 191
5.3 STRUCTURED NAMING 195
5.3.1 Name Spaces 195
5.3.2 Name Resolution 198
5.3.3 The Implementation of a Name Space 202
5.3.4 Example：The Domain Name System 209
5.4 ATTRIBUTE-BASED NAMING 217
5.4.1 Directory Services 217
5.4.2 Hierarchical Implementations：LDAP 218
5.4.3 Decentralized Implementations 222
5.5 SUMMARY 231
6 SYNCHRONIZATION 231
6.1 CLOCK SYNCHRONIZATION 232
6.1.1 Physical Clocks 233
6.1.2 Global Positioning System 236
6.1.3 Clock Synchronization Algorithms 238
6.2 LOGICAL CLOCKS 244
6.2.1 Lamport's Logical Clocks 244
6.2.2 Vector Clocks 248
6.3 MUTUAL EXCLUSION 252
6.3.1 Overview 252
6.3.2 A Centralized Algorithm 253
6.3.3 A Decentralized Algorithm 254
6.3.4 A Distributed Algorithm 255
6.3.5 A Token Ring Algorithm 258
6.3.6 A Comparison of the Four Algorithms 259
6.4 GLOBAL POSITIONING OF NODES 260
6.5 ELECTION ALGORITHMS 263
6.5.1 Traditional Election Algorithms 264
6.5.2 Elections in Wireless Environments 267
6.5.3 Elections in Large-Scale Systems 269
6.6 SUMMARY 270
7 CONSISTENCY AND REPLICATION 273
7.1 INTRODUCTION 274
7.1.1 Reasons for Replication 274
7.1.2 Replication as Scaling Technique 275
7.2 DATA-CENTRIC CONSISTENCY MODELS 276
7.2.1 Continuous Consistency 277
7.2.2 Consistent Ordering of Operations 281
7.3 CLIENT-CENTRIC CONSISTENCY MODELS 288
7.3.1 Eventual Consistency 289
7.3.2 Monotonic Reads 291
7.3.3 Monotonic Writes 292
7.3.4 Read Your Writes 294
7.3.5 Writes Follow Reads 295
7.4 REPLICA MANAGEMENT 296
7.4.1 Replica-Server Placement 296
7.4.2 Content Replication and Placement 298
7.4.3 Content Distribution 302
7.5 CONSISTENCY PROTOCOLS 306
7.5.1 Continuous Consistency 306
7.5.2 Primary-Based Protocols 308
7.5.3 Replicated-Write Protocols 311
7.5.4 Cache-Coherence Protocols 313
7.5.5 Implementing Client-Centric Consistency 315
7.6 SUMMARY 317
8 FAULT TOLERANCE 321
8.1 INTRODUCTION TO FAULT TOLERANCE 322
8.1.1 Basic Concepts 322
8.1.2 Failure Models 324
8.1.3 Failure Masking by Redundancy 326
8.2 PROCESS RESILIENCE 328
8.2.1 Design Issues 328
8.2.2 Failure Masking and Replication 330
8.2.3 Agreement in Faulty Systems 331
8.2.4 Failure Detection 335
8.3 RELIABLE CLIENT-SERVER COMMUNICATION 336
8.3.1 Point-to-Point Communication 337
8.3.2 RPC Semantics in the Presence of Failures 337
8.4 RELIABLE GROUP COMMUNICATION 343
8.4.1 Basic Reliable-Multicasting Schemes 343
8.4.2 Scalability in Reliable Multicasting 345
8.4.3 Atomic Multicast 348
8.5 DISTRIBUTED COMMIT 355
8.5.1 Two-Phase Commit 355
8.5.2 Three-Phase Commit 360
8.6 RECOVERY 363
8.6.I Introduction 363
8.6.2 Checkpointing 366
8.6.3 Message Logging 369
8.6.4 Recovery-Oriented Computing 372
8.7 SUMMARY 373
9 SECURITY 377
9.1 INTRODUCTION TO SECURITY 378
9.1.1 Security Threats,Policies,and Mechanisms 378
9.1.2 Design Issues 384
9.1.3 Cryptography 389
9.2 SECURE CHANNELS 396
9.2.1 Authentication 397
9.2.2 Message Integrity and Confidentiality 405
9.2.3 Secure Group Communication 408
9.2.4 Example：Kerberos 411
9.3 ACCESS CONTROL 413
9.3.1 General Issues in Access Control 414
9.3.2 Firewalls 418
9.3.3 Secure Mobile Code 420
9.3.4 Denial of Service 427
9.4 SECURITY MANAGEMENT 428
9.4.1 Key Management 428
9.4.2 Secure Group Management 433
9.4.3 Authorization Management 434
9.5 SUMMARY 439
10 DISTRIBUTED OBJECT-BASED SYSTEMS 443
10.1 ARCHITECTURE 443
10.1.1 Distributed Objects 444
10.1.2 Example：Enterprise Java Beans 446
10.1.3 Example：Globe Distributed Shared Objects 448
10.2 PROCESSES 451
10.2.1 Object Servers 451
10.2.2 Example：The Ice Runtime System 454
10.3 COMMUNICATION 456
10.3.1 Binding a Client to an Object 456
10.3.2 Static versus Dynamic Remote Method Invocations 458
10.3.3 Parameter Passing 460
10.3.4 Example：Java RMI 461
10.3.5 Object-Based Messaging 464
10.4 NAMING 466
10.4.1 CORBA Object References 467
10.4.2 Globe Object References 469
10.5 SYNCHRONIZATION 470
10.6 CONSISTENCY AND REPLICATION 472
10.6.1 Entry Consistency 472
10.6.2 Replicated Invocations 475
10.7 FAULT TOLERANCE 477
10.7.1 Example：Fault-Tolerant CORBA 477
10.7.2 Example：Fault-Tolerant Java 480
10.8 SECURITY 481
10.8.1 Example：Globe 482
10.8.2 Security for Remote Objects 486
10.9 SUMMARY 487
11 DISTRIBUTED FILE SYSTEMS 491
11.1 ARCHITECTURE 491
11.1.1 Client-Server Architectures 491
11.1.2 Cluster-Based Distributed File Systems 496
11.1.3 Symmetric Architectures 499
11.2 PROCESSES 501
11.3 COMMUNICATION 502
11.3.1 RPCs in NFS 502
11.3.2 The RPC2 Subsystem 503
11.3.3 File-Oriented Communication in Plan 9 505
11.4 NAMING 506
11.4.1 Naming in NFS 506
11.4.2 Constructing a Giobal Name Space 512
11.5 SYNCHRONIZATION 513
11.5.1 Semantics of File Sharing 513
11.5.2 File Locking 516
11.5.3 Sharing Files in Coda 518
11.6 CONSISTENCY AND REPLICATION 519
11.6.1 Client-Side Caching 520
11.6.2 Server-Side Replication 524
11.6.3 Replication in Peer-to-Peer File Systems 526
11.6.4 File Replication in Grid Systems 528
11.7 FAULT TOLERANCE 529
11.7.1 Handling Byzantine Failures 529
11.7.2 High Availability in Peer-to-Peer Systems 531
11.8 SECURITY 532
11.8.1 Security in NFS 533
11.8.2 Decentralized Authentication 536
11.8.3 Secure Peer-to-Peer File-Sharing Systems 539
11.9 SUMMARY 541
12 DISTRIBUTED WEB-BASED SYSTEMS 545
12.1 ARCHITECTURE 546
12.1.1 Traditional Web-Based Systems 546
12.1.2 Web Services 551
12.2 PROCESSES 554
12.2.1 Clients 554
12.2.2 The Apache Web Server 556
12.2.3 Web Server Clusters 558
12.3 COMMUNICATION 560
12.3.1 Hypertext Transfer Protocol 560
12.3.2 Simple Object Access Protocol 566
12.4 NAMING 567
12.5 SYNCHRONIZATION 569
12.6 CONSISTENCY AND REPLICATION 570
12.6.1 Web Proxy Caching 571
12.6.2 Replication for Web Hosting Systems 573
12.6.3 Replication of Web Applications 579
12.7 FAULT TOLERANCE 582
12.8 SECURITY 584
12.9 SUMMARY 585
13 DISTRIBUTED COORDINATION-BASED SYSTEMS 589
13.1 INTRODUCTION TO COORDINATION MODELS 589
13.2 ARCHITECTURES 591
13.2.1 Overall Approach 592
13.2.2 Traditional Architectures 593
13.2.3 Peer-to-Peer Architectures 596
13.2.4 Mobility and Coordination 599
13.3 PROCESSES 601
13.4 COMMUNICATION 601
13.4.1 Content-Based Routing 601
13.4.2 Supporting Composite Subscriptions 603
13.5 NAMING 604
13.5.1 Describing Composite Events 604
13.5.2 Matching Events and Subscriptions 606
13.6 SYNCHRONIZATION 607
13.7 CONSISTENCY AND REPLICATION 607
13.7.1 Static Approaches 608
13.7.2 Dynamic Replication 611
13.8 FAULT TOLERANCE 613
13.8.1 Reliable Publish-Subscribe Communication 613
13.8.2 Fault Tolerance in Shared Dataspaces 616
13.9 SECURITY 617
13.9.1 Confidentiality 618
13.9.2 Secure Shared Dataspaces 620
13.10 SUMMARY 621
14 SUGGESTIONS FOR FURTHER READING AND BIBUOGRAPHY 623
14.1 SUGGESTIONS FOR FURTHER READING 623
14.1.1 Introduction and General Works 623
14.1.2 Architectures 624
14.1.3 Processes 625
14.1.4 Communication 626
14.1.5 Naming 626
14.1.6 Synchronization 627
14.1.7 Consistency and Replication 628
14.1.8 Fault Tolerance 629
14.1.9 Security 630
14.1.10 Distributed Object-Based Systems 631
14.1.11 Distributed File Systems 632
14.1.12 Distributed Web-Based Systems 632
14.1.13 Distributed Coordination-Based Systems 633
14.2 ALPHABETICAL BIBLIOGRAPHY 634
INDEX 669