PREFACE
1 INTRODUCTlON
l.1 DEFINITION OF A DISTRIBUTED SYSTEM 2
l.2 GOALS 4
l.2.l Connecting Users and Resources 4
l.2.2 Transparency 5
1.2.3 Openness 8
l.2.4 Scalability 10
l.3 HARDWARE CONCEPTS l6
l.3.l Multiprocessors l7
l.3.2 Homogeneous MuIticomputer Systems l9
l.3.3 Heterogeneous Multicomputer Systems 2l
l.4 SOFTWARE CONCEPTS 22
l.4.l Distributed Operating Systems 22
l.4.2 Network Operating Systems 33
l.4.3 Middleware 36
l.5 THE CLIENT-SERVER MODEL 42
l.5.l Clients and Servers 42
l.5.2 Application Layering 46
l.5.3 Client-Server Architectures 50
1.6 SUMMARY 53
2 COMMUNICATION
2.l LAYERED PROTOCOLS 58
2.l.l Lower-Level Protocols 6l
2.l.2 Transport Protocols 63
2.l.3 Higher-Level Protocols 66
2.2 REMOTE PROCEDURE CALL 68
2.2.l Basic RPC Operation 69
2.2.2 Parameter Passing 73
2.2.3 Extended RPC Models 77
2.2.4 Example: DCE RPC 80
2.3 REMOTE OBJECT INVOCATION 85
2.3.l Distributed Objects 86
2.3.2 Binding a Client to an Object 88
2.3.3 Static versus Dynamic Remote Method Invocations 90
2.3.4 Parameter Passing 9l
2.3.5 ExamPle l: DCE Remote Objects 93
2.3.6 Example 2: Java RMI 95
2.4 MESSAGE-ORIEmD COMMUNICATION 99
2.4.l Persistence and Synchronicity in Conunnication 99
2.4.2 Message-Oriented Transient Conunnication l04
2.4.3 Message-Oriented Persistent Communication l08
2.4.4 ExamPle: IBM MQSeries ll5
2.5 SmAM-ORIENTED COMMUNICATION ll9
2.5.l Support for Continuous Media l20
2.5.2 Streams and Quality of Service l23
2.5.3 Stream Synchronization l27
2.6 SUMMARY 130
3 PROCESSES 135
3.l THREADS l36
3.l.l Introduchon to Threads l36
3.l.2 Threads in Distributed Systems 14l
3.2 CLIENTS 145
3.2.l User Interfaces l45
3.2.2 Client-Side Software for Distribution Transparency l47
3.3 SERVERS 149
3.3.l General Design Issues l49
3.3.2 Object Servers 152
3.4 CODE MIGRATION 158
3.4.l Approaches to Code Migration 158
3.4.2 Migration and Local Resources 163
3.4.3 Migration in Heterogeneous Systems l65
3.4.4 Example: D'Agents 168
3.5 SOFTWARE AGENTS l73
3.5.l Software Agents in Distributed Systems l73
3.5.2 Agent Technology l75
3.6 SUMMARY l78
4 NAMING
4.l NAMING ENTITIES 184
4.l.l Names, Identifiers, and Addresses l84
4.l.2 Name Resolution l89
4.l.3 The Implementation of a Name Space l94
4.1.4 Example: The Domain Name System 20l
4.1.5 Example: X.500 206
4.2 LOCATING MOBILE ENTITIES 2l0
4.2.l Naming versus Locating Entities 2l0
4.2.2 Simple Solutions 2l2
4.2.3 Home-Based Approaches 216
4.2.4 Hierarchical Approaches 2l7
4.3 REMOVING UNREFERENCED ENTITIES 225
4.3.l The Problem of Unreferenced Objects 225
4.3.2 Reference Counting 227
4.3.3 Reference Listing 23l
4.3.4 Identifying Unreachable Entities 232
4.4 SUMMARY 238
5 SYNCHRONIZATION
5.l CLOCK SYNCHRONIZATION 242
5.1.l Physical Clocks 243
5.l.2 Clock Synchronization Algorithms 246
5.l.3 Use of Synchronized Clocks 25l
5.2 LOGICAL CLOCKS 252
5.2.1 Lamport timestamps 252
5.2.2 Vector timestamps 256
5.3 GLOBAL STATE 258
5.4 ELECTION ALGORITHMS 262
5.4.l The Bully Algorithm 262
5.4.2 A Ring Algorithm 263
5.5 MUTUAL EXCLUSION 265
5.5.l A Centralized Algorithm 265
5.5.2 A Distributed Algorithm 266
5.5.3 A Token Ring Algorithm 269
5.5.4 A Comparison of the Three Algorithms 270
5.6 DISTRIBUTED TRANSACTIONS 27l
5.6.l The Transaction Model 272
5.6.2 Classification of Transactions 275
5.6.3 Implementation 278
5.6.4 Concurrency Control 280
5.7 SUMMARY 288
6 CONSlSTENCY AND REPLICATION
6.l INTRODUCTION 292
6.1.l Reasons for Replication 292
6.l.2 Object Replication 293
6.l.3 Replication as Scaling Technique 296
6.2 DATA-CENTRIC CONSISTENCY MODELS 297
6.2.l Strict Consistency 298
6.2.2 Linearizability and Sequential ConsistCncy 30()
6.2.3 Causal Consistency 305
6.2.4 FIFO Consistency 306
6.2.5 Weak Consistency 308
6.2.6 Release Consistency 3l0
6.2.7 Entry Consistency 3l3
6.2.8 Summary of Consistency Models 3l5
6.3 CLIENT-CENTRIC CONSISTENCY MODELS 3l6
6.3.l Eventual Consistency 3l7
6.3.2 Monotonic Reads 319
6.3.3 Monotonic Writes 320
6.3.4 Read Your Writes 322
6.3.5 Writes Follow Reads 323
6.3.6 Implementation 324
6.4 DISTRIBUTION PROTOCOLS 326
6.4.l Replica Placement 326
6.4.2 Update Propagation 330
6.4.3 Epidendc Protocols 334
6.5 CONSISTENCY PROTOCOLS 337
6.5.l Primary-Based Protocols 337
6.5.2 Replicated-Write Protocols 341
6.5.3 Cache-Coherence Protocols 345
6.6 EXAMPLES 346
6.6.l Orca 347
6.6.2 Causally--Consistent Lazy Replication 352
6.7 SUMMARY 357
7 FAULT TOLERANCE
7.1 INTRODUCTION TO FAULT TOLERANCE 362
7.l.l Basic Concepts 362
7.1.2 Failure Models 364
7.l.3 Failure Masking by Redundancy 366
7.2 PROCESS RESILIENCE 368
7.2.l Design Issues 368
7.2.2 Failure Masking and Replication 370
7.2.3 Agreement in Faulty Systems 371
7.3 RELIABLE CLIENT-SERVER COMMUNICAnON 375
7.3.l Point-to-Point Communication 375
7.3.2 RPC Semantics in the Presence of Failures 375
7.4 RELIABLE GROUP COMMUNICATION 38l
7.4.l Basic Reliable-Multicasting Schemes 38l
7.4.2 Scalability in Reliable Multicasting 383
7.4.3 Atomic Multicast 386
7.5 DISTRIBUTED COMMIT 393
7.5.l Two-Phase Commit 393
7.5.2 Three-Phase Commit 399
7.6 RECOVERY 40l
7.6.l Introduction 401
7.6.2 Checkpointing 404
7.6.3 Message Logging 407
7.7 SUMMARY 4l0
8 SECURITY
8.l INTRODUCTION TO SECURITY 414
8.l.l Security Threats, Policies, and Mechhosms 4l4
8.l.2 Design Issues 420
8.l.3 Cryptography 425
8.2 SECURE CHANNELS 432
8.2.l Authentication 433
8.2.2 Message Integrity and Confidentiality 44l
8.2.3 Secure Group Communication 444
8.3 ACCESS CONTROL 447
8.3.l General Issues in Access Control 447
8.3.2 Firewalls 45l
8.3.3 Secure Mobile Code 453
8.4 SECURITY MANAGEMENT 460
8.4.l Key Management 46l
8.4.2 Secure Group Management 465
8.4.3 Authorization Management 466
8.5 EXAMPLE: KERBEROS 472
8.6 EXAMPLE: SESAME 473
8.6.l SESAME Components 474
8.6.2 Privilege Attribute Certificates (PACs) 477
8.7 EXAMPLE: ELECTRONIC PAYMENT SYSTEMS 478
8.7.1 Electronic Payment Systems 478
8.7.2 Security in ElectrOnic Payment Systems 480
8.7.3 Example Protocols 484
8.8 SUMMARY 488
9 DISTRIBUTED OBJECT-BASED SYSTEMS
9.l CORBA 494
9.l.l Overview of CORBA 495
9.1.2 Communication 50l
9.l.3 Processes 508
9.l.4 Naming 5l4
9.l.5 Synchronization 5l8
9.1.6 Caching and Replication 5l8
9.l.7 Fault Tolerance 520
9.l.8 Security 522
9.2 DISTRIBUTED COM 525
9.2.l Overview of DCOM 526
9.2.2 Communication 53l
9.2.3 Processes 534
9.2.4 Naming 537
9.2.5 Synchronization 54l
9.2.6 Replication 54l
9.2.7 Fault Tolerance 54l
9.2.8 Security 542
9.3 GLOBE 545
9.3.l Overview of Globe 545
9.3.2 Communication 553
9.3.3 Processes 554
9.3.4 Naming 557
9.3.5 Synchronization 559
9.3.6 Replication 560
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