DATA COMMUNICATIONS AND DISTRIBUTED NETWORKS

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Derick Snow
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1 DATA COMMUNICATIONS AND DISTRIBUTED NETWORKS UYLESS D. BLACK CONTENTS PREFACE xv 1 INTRODUCTION 1 Purpose of Data Communications Systems and Networks 1 Purpose of Data Communications Systems 2 The Components 3 The Advent of Computer-Based Data Communications Systems 3 Evolution of Data Communications Systems, 4 Network Topologies 6 Organizations in the Industry 8 Carriers, 9 Federal Communications Commission 9 International Record Carriers 10 International Organizations 10 European Organizations 11 American National Standards Institut 11 Electronic Industries Association 12 The Institute of Electrical and Electronic Engineers 12 National Communications System, 12 National Institute of Standards and Technology 12 The Internet Activities 12 The Telephone System 13 Summary 13 2 OVERVIEW OF A DATA COMMUNICATIONS NETWORK 14 Introduction 14 Network Transfer Capacity 14 Network Types 15 Public and Private Networks 15 Switched and Broadcast Networks 15 Local and Wide Area Networks 16 Network Components 17 Connecting Networks 18 Physical Interfaces 21 Summary 22 3 DATA COMMUNICATIONS SYSTEMS OPERATIONS 23 Introduction 23 How Data Are Transmitted 23 Transmission Characteristics 24 Asynchronous and Synchronous Transmission 34 Basic Terms and Concepts 37 Frames, Headers, and Codes 37 Communication Sessions between User Applications 40 Line Characteristics 40 Use of the Telephone Network, 43

2 Use of the Telephone Network, 43 Summary 45 Appendix 3A Asynchronous Operators 45 4 MAJOR COMPONENTS IN A DATA COMMUNICATlONS SYSTEM 50 Introduction 50 The Transmission Path 50 Wire Pairs 50 Microwave 51 Coaxial Cables 52 Comparison of Wire-Pair Cable and Coaxial Cable, 53 Satellite Communications 53 Optical Fibers 58 Submarine Cable 62 Waveguides 62 Summary of Media Options, 63 Modems 63 Modulation Techniques 63 Multilevel Transmission 65 Other Modems 66 Advances in Modems 68 Interface Standards 69 The Modem Market 77 Summary of Modem Operations 80 Switching 80 Circuit Switching 81 Message Switching 84 Packet Switching 85 When and When Not to Use Packet Switching 86 Packet Voice 93 Private Branch Exchanges 93 Multiplexing, Line Sharing, and Compression 94 Multiplexing 94 Multiplexed Common Carrier Systems 101 Multiplexing Satellite Signais 101 Concentrators 102 Data Compression 102 Terminals 108 Dumb Teleprinters and CRTs 109 Smart Teleprinters and CRTs 109 Local Storage Terminals 109 The Personal Computer 110 Communications Front Ends 110 Summary SOFTWARE AND DATA BASES 114 Introduction 114 Communications Programming 114 Communications between Host and Front End 116 Applications Software 118 Data Bases 119 Data Storage, 119 Organization 120 Schemas and Subschemas 128 Summary TRANSMISSION IMPAIRMENTS 131 Introduction 131 Factors Contributing to Errors 131 Distance between Components, 132 Transmission over Hostile Environments 132 Number of Components Involved in Transmission 133 Lack of Control over the Process 133 Units of Measurement and Other Terminology 133 The Decibel 133 Resistance 135 Inductance 135 Capacitance 135 Major Impairments 135 Random Distortions 136 Nonrandom Distortions 142 Error Control Methods 146 Perceived A vailability 148 Mitigating the Effects of Distortions 148 Testing and Monitoring 152 Typical Diagnostic Equipment 153 Bit and Block Error Rates 155 Loopbacks 156 Troubleshooting Flow Charts 157 Correcting Errors 157 Summary 161

3 Summary DATA LINK CONTROLS/LINE PROTOCOLS 162 Introduction 162 Data Accountability and Line Control 162 The HDLC Specification 164 Classification of Data Link Controls 165 Message Format 165 Line Control Method 165 Error-Handling Method 170 Flow Control 173 Examples of Data Link Controls Asynchronous Control 178 Communications Protocols 180 The XMODEM Protocol, 180 The Kermit Protocol 183 Binary Synchronous Control 187 Synchronous Data Link Control 190 Communications Satellites and Data Link Controls 198 Frame Relay 199 Summary DIGITAL TRANSMISSION 201 Introduction 201 Advantages of Digital Transmission 201 How Digital Transmission Works 203 Digitization Schemes and Voice Digitization Rate 205 Companded PCM 206 Differentiai PCM 207 Delta Modulation 207 Analysis-Synthesis Techniques 207 Digital Pulse Codes 207 Nonretum to Zero 207 Retum to Zero 209 Biphase 209 Common-Carrier Pulse Codes 210 Regenerative Repeaters 210 The Digital Hierarchy 211 Integrated Services Digital Networks 212 Digital PBXs 214 Digital Switching 217 Emerging Digital Technology 218 Broadband Networks 218 Signaling Hierarchies for the Emerging Technologies 200 SONET 221 Summary DISTRIBUTED NETWORK ARCHITECTURES 226 Introduction 226 Architectures and Protocols 226 Layered Protocols 227 Open Systems Interconnection 229 Physical Layer, 230 Data Link Layer 232 Network Layer for Wide Area Networks 232 X Transport Layer 240 Session Layer 241 Presentation Layer 242 Application Layer 242 Other OSI Standards 242 Potential Problems of Merging Two Technologies 245 The TCP/IP Suite of Protocols 249 TCP/IP and the OSI 250 The Internet Layers 250 Example of Layer Operations 251 The Internet Protocol 253 IP Services 253 The Transmission Control Protocol 255 OSI and TCP/IP 261 GOSIP 267 GOSIP Version GOSIP Version 2, 271 Summary REMOTE PROCEDURE CALLS 272 Introduction 272 The Client-Server Model 272 Remote Procedure CaIIs 273 The Stub 273 Problems with Remote CaIIs 274 OSI Remote Procedure Operations 275 Sun's Remote Procedure CaII 278

4 Sun's Remote Procedure CaII 278 Supporting Protocols for an RPC 280 Obtaining the Services of a Remote Server 280 Remote Commands 283 Transfer Syntax between Distributed Processes 283 Basic Encoding Rules 287 The Presentation Context Identifier (PCI) 288 The Distributed Computing Environment (DCE) and the Distributed Management Environment (DME) 289 The DCE 289 The DME 291 Summary LOCAL AREA NETWORKS 295 Introduction 295 Local Area Networks: Definitions and Usage 295 Major Components of a Local Area Network 296 LAN Protocols 297 The IEEE Standards 297 Contention: CSMA/CD 299 Token Ring 300 Token Bus 302 Metropolitan Area Network 303 Fiber-Distributed Data Interface 304 Logical Link Control 306 Role of the Personal Computer 307 Other Local Area Networks 308 Ethemet 309 AT&T Information System Network 312 IBM Token Ring 313 Examples of Personal Computers and Local Area Networks 315 Summary MANAGING DlSTRIBUTED SYSTEMS 317 Introduction 317 Distributed Systems 317 Why Go Distributed? 318 Pros and Cons of Distributed Processing 320 The Disadvantages 320 The Advantages 321 Distributed Data Bases 323 Reasons for Distributing Data 323 Types of Distribution 324 Distributed Data Terms and Concepts 325 The Challenge of Distributed Data 328 Loading Factors, 334 Managing the Distributed Resources 336 Management Model 338 Intemode Data Administration 342 Equipment Inventory 344 Internode Configuration Management 344 Using Distributed Automation Management 345 Division Responsibilities 345 Managing Distributed Networks with the X.500 Directory 347 Key Terms and Concepts 347 X.500 Services and Ports, 350 Operating a Distributed Directory 351 Authentication Procedures for Directory Access 352 Simple Authentication 352 Strong Authentication 353 Summary DESIGN CONSIDERATIONS 356 Introduction 356 Chapter Structure 356 Communications Line Loading 357 Case Study Background 357 Approach to the Analysis 358 Line-Loading Calculations 367 Other Considerations 375 Improving the Network 379 Summary of Line-Loading Analysis 392 Partitioning and Allocation 392 Data Flow Systems 396 Dimension Analysis, 398 Partitioning Resources in the Southern Region 399 Network Data-Base Design Considerations 401 Ratio Analysis 401 Data-Base Design Decision Trees 408 Synchronization of Network Data Bases, 410 Additional Considerations on Using Personal Computers 414

5 TOP Summary of Network Data-Base Considerations 415 Summary 416 INDEX 417

Telecommunications II TEL 202 Spring, 2004

Telecommunications II TEL 202 Spring, 2004 Time: Lecture: Thursday 12:20 3:30 Lynn Campus, Room LW207 Laboratory: Thursday 4:00 5:00 Lynn Campus, Room LE201 Instructor: Scott Stimpson Office: Lynn, W228