Understanding Data Communications1

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1 Communications in a Modern Society 1
1.1 Applications 1
1.1.1 Data collection 2
1.1.2 Transaction processing 3
1.1.3 Conversational time sharing 5
1.1.4 Remote job entry 7
1.1.5 Message switching 7
1.1.6 Value-added carriers and electronic mail 8
1.1.7 Office automation 12
1.1.8 Electronic commerce 14
1.1.9 Satellite transmission 16
1.2 Constraints 16
1.2.1 Throughput 17
1.2.2 Response time 18
1.2.3 Bandwidth 18
1.2.4 Economics 19
1.3 Emerging Trends 19
1.4 ReviewQuestion s 20
2 Basic Telegraph and Telephone Operations 23
2.1 Evolution of Communications 23
2.2 Telegraphy 24
2.2.1 Operation 24
2.2.2 Morse code 26
2.2.3 Morse code limitations 27
2.2.4 Start–stop signaling and the Baudot code 28
2.2.5 Bits and codes 29
2.3 Telephony 32
2.3.1 Principle of operation 32
2.3.2 Sound wave conversion 34
2.3.3 The basic telephone connection 36
2.3.4 Switchboards and central offices 37
2.3.5 Numbering plans 39
2.3.6 Geographic calling areas and network routing 40
2.3.7 The world numbering plan 43
2.4 ReviewQuestion s 43
Understanding Data Communications: From Fundamentals to Networking.
Third Edition Gilbert Held
Copyright # 2000 John Wiley & Sons Ltd
Print ISBN 0-471-627453 Online ISBN 0-470-84148-6
3Basic Circuit Parameters, Measurement Units and
Media Overview 47
3.1 Basic Circuit Parameters 47
3.1.1 Frequency and bandwidth 47
3.1.2 The telephone channel passband 49
3.2 Measurement Units 50
3.2.1 Power ratios 50
3.2.2 Signal-to-noise ratio 52
3.2.3 Reference points 54
3.3 Media Overview56
3.3.1 Twisted-pair cable 56
3.3.2 Coaxial cable 61
3.3.3 Microwave 63
3.3.4 Fiber-optic transmission 64
3.4 Channel Capacity 67
3.4.1 Bit versus baud 67
3.4.2 Nyquist relationship 67
3.4.3 Shannon’s law68
3.5 Structured Wiring 69
3.5.1 The wiring closet 69
3.5.2 The EIA/TIA-568 standard 69
3.6 ReviewQue stions 72

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4 Fundamental Data Transmission Concepts 75
4.1 Analog Line Connections 75
4.1.1 The analog switched line 76
4.1.2 Analog leased line 79
4.1.3 Dedicated line 82
4.1.4 Switched network vs leased line economics 83
4.2 Types of Service and Transmission Devices 84
4.2.1 Digital repeaters 85
4.2.2 Modems 86
4.2.3 Acoustic couplers 87
4.2.4 Analog facilities 89
4.2.5 Digital facilities 93
4.2.6 Digital signaling 93
4.2.7 Representative AT&T digital offerings 96
4.3 Transmission Mode 98
4.3.1 Simplex transmission 98
4.3.2 Half-duplex transmission 99
4.3.3 Full-duplex transmission 100
4.3.4 Terminal and mainframe computer operating modes 101
4.4 Transmission Techniques 103
4.4.1 Asynchronous transmission 103
4.4.2 Synchronous transmission 105
4.5 Types of Transmission 106
4.6 Wide Area Network Transmission Structures 107
4.6.1 Mainframe computer-based network structure 108
4.6.2 LAN network structure 109
4.6.3 LAN internetworking structure 110
4.7 Line Discipline 111
4.8 Transmission Rate 113
4.8.1 Analog service 113
4.8.2 Digital service 114
vi CONTENTS
4.9 Transmission Codes 115
4.9.1 Morse code 115
4.9.2 Baudot code 116
4.9.3 BCD code 116
4.9.4 Extended binary-coded decimal interchange code (EBCDIC) 116
4.9.5 ASCII code 118
4.10 ReviewQue stions 122
5 Terminals, Workstations and WAN and LAN
Networking Overview 125
5.1 Terminals 126
5.1.1 Interactive terminal classification 126
5.1.2 Terminal evolution 127
5.2 Workstations and Other LAN Components 141
5.2.1 Network interface card 141
5.2.2 Hubs 142
5.2.3 File server 143
5.2.4 Print server 145
5.2.5 Other types of servers 146
5.3 Wide Area Networking Overview 146
5.3.1 Multiplexing and data concentration 146
5.3.2 Front-end processor 151
5.3.3 Network configurations 151
5.4 Local Area Networking Overview 152
5.4.1 Repeaters 153
5.4.2 Bridges 153
5.4.3 Routers 154
5.4.4 Gateways 155
5.5 ReviewQuestion s 157
6 Representative Standards Organizations:
the OSI Reference Model 159
6.1 National Standards Organizations 160
6.1.1 American National Standards Institute (ANSI) 160
6.1.2 Electronic Industries Association (EIA) 161
6.1.3 Federal Information Processing Standards (FIPS) 163
6.1.4 Institute of Electrical and Electronic Engineers (IEEE) 163
6.1.5 British Standards Institution (BSI) 164
6.1.6 Canadian Standards Association (CSA) 164
6.2 International Standards Organizations 164
6.2.1 International Telecommunications Union (ITU) 164
6.2.2 International Standards Organization (ISO) 165
6.3 De facto Standards 167
6.3.1 AT&T compatibility 168
6.3.2 Cross-licensed technology 169
6.3.3 Bellcore/Telcordia Technology 169
6.3.4 Internet standards 170
6.4 The OSI Reference Model 171
6.4.1 Layered architecture 172
6.4.2 OSI layers 173
6.4.3 Data flow176
6.5 IEEE 802 Standards 177
6.5.1 802 committees 177
6.5.2 Data link subdivision 179
6.6 ReviewQuestion s 180
CONTENTS vii
7 The Physical Layer, Cables, Connectors, Plugs
and Jacks 183
7.1 DTE/DCE Interfaces 184
7.1.1 Connector overview186
7.1.2 RS-232-C/D 188
7.1.3 Differential signaling 198
7.1.4 RS-449 200
7.1.5 V.35 202
7.1.6 RS-366-A 203
7.1.7 X.21 and X.20 204
7.1.8 X.21 bis 207
7.1.9 RS-530 207
7.1.10 High Speed Serial Interface 298
7.1.11 High Performance Parallel Interface 214
7.1.12 Universal Serial Bus 216
7.1.13 IEEE 1394 (FireWire) 218
7.2 Cables and Connectors 222
7.2.1 Twisted-pair cable 222
7.2.2 Low-capacitance shielded cable 223
7.2.3 Ribbon cable 223
7.2.4 The RS-232 null modem 223
7.2.5 RS-232 cabling tricks 225
7.3 Plugs and Jacks 226
7.3.1 Connecting arrangements 228
7.3.2 Telephone options 230
7.3.3 Ordering the business line 231
7.3.4 LAN connectivity 232
7.4 ReviewQue stions 233

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8 Basic Transmission Devices: Line Drivers,
Modems, and Service Units 235
8.1 Line Drivers 236
8.1.1 Direct connection 236
8.1.2 Using line drivers 239
8.2 Modem Operations 243
8.2.1 The modulation process 243
8.2.2 Bps vs. baud 246
8.2.3 Voice circuit parameters 246
8.2.4 Combined modulation techniques 247
8.2.5 Mode of transmission 253
8.2.6 Transmission techniques 254
8.2.7 Modem classification 255
8.2.8 Limited-distance modems 256
8.2.9 Line-type operations 257
8.2.10 Reverse and secondary channels 257
8.2.11 Equalization 258
8.2.12 Synchronization 260
8.2.13 Multiport capability 260
8.2.14 Security capability 261
8.2.15 Multiple speed selection capability 261
8.2.16 Voice/data capability 262
8.2.17 Modem handshaking 262
8.2.18 Self-testing features 263
8.2.19 Modem indicators 265
8.2.20 Modern operations and compatibility 265
viii CONTENTS
8.3 Intelligent Modems 289
8.3.1 Hayes command set modems 289
8.3.2 Key intelligent modem features 296
8.3.3 Microcom Networking Protocol (MNP) 302
8.3.4 Data compression 306
8.3.5 MNP Class 5 compression 306
8.3.6 MNP Class 7 enhanced data compression 308
8.3.7 V.42bis 311
8.4 Broadband Modems 312
8.4.1 Telephone and cable TV infrastructure 313
8.4.2 Cable modems 317
8.4.3 DSL modems 324
8.5 Service Units 330
8.5.1 The DSU 331
8.5.2 The CSU 331
8.6 ReviewQuestion s 332
9 Regulators and Carriers 335
9.1 Regulators 336
9.1.1 US regulatory evolution 336
9.1.2 International regulatory authorities 342
9.2 Carrier Offerings 343
9.2.1 AT&T system evolution 343
9.2.2 The Bell system 345
9.2.3 The regional Bell operating companies 346
9.2.4 AT&T service offerings 349
9.2.5 Regional Bell operating company offerings 355
9.3 ATM Overview356
9.4 ReviewQuestion s 357
10 Transmission Errors: Causes, Measurements and
Correction Methods 359
10.1 Causes of Transmission Errors 359
10.2 Performance Measurements 360
10.2.1 Bit error rate 360
10.2.2 Bit error rate tester 360
10.2.3 BERT time 362
10.2.4 Performance classifications 362
10.2.5 Block error rate testing 364
10.2.6 Error-free second testing 365
10.3 Error Detection and Correction Techniques 365
10.3.1 Asynchronous transmission 365
10.3.2 Synchronous transmission 370
10.4 ReviewQue stions 374
11 The WAN Data Link Layer 377
11.1 Terminal and Data Link Protocols: Characteristics
and Functions 378
11.1.1 Transmission sequence 379
11.1.2 Error control 379
11.2 Types of Protocol 380
11.2.1 Teletypewriter protocols 380
11.2.2 PC file transfer protocols 385
CONTENTS ix
11.2.3 Bisynchronous protocols 395
11.2.4. Digital Data Communications Message Protocol (DDCMP) 400
11.2.5 Bit-oriented line control procedures 402
11.3 ReviewQuestio ns 407
12 Increasing WAN Line Utilization 409
12.1 Multiplexers 410
12.1.1 Evolution 410
12.1.2 Device support 410
12.1.3 Multiplexing techniques 411
12.2 Control Units 439
12.2.1 Control unit concept 440
12.2.2 Attachment methods 440
12.2.3 Unit operation 442
12.2.4 Breaking the closed system 443
12.3 ReviewQuestio ns 445
13Local Area Networks 449
13.1 Origin 449
13.2 Comparison with WANs 450
13.2.1 Geographical area 450
13.2.2 Data transmission and error rates 450
13.2.3 Ownership 451
13.2.4 Regulation 451
13.2.5 Data routing and topology 451
13.2.6 Type of information carried 452
13.3 Utilization Benefits 452
13.3.1 Peripheral sharing 453
13.3.2 Common software access 453
13.3.3 Electronic mail 453
13.3.4 Gateway access to mainframes 453
13.3.5 Internet access 453
13.3.6 Virtual private network operations 454
13.4 Technological Characteristics 454
13.4.1 Topology 454
13.4.2 Comparison of topologies 456
13.4.3 Signaling methods 457
13.4.4 Transmission medium 460
13.4.5 Access methods 460
13.5 Ethernet Networks 465
13.5.1 Original network components 465
13.5.2 IEEE 802.3 networks 468
13.5.3 Frame composition 490
13.5.4 Media access control overview495
13.5.5 Logical link control overview495
13.5.6 Other Ethernet frame types 498
13.6 Token-Ring 504
13.6.1 Topology 504
13.6.2 Redundant versus non-redundant main ring paths 506
13.6.3 Cabling and device restrictions 507
13.6.4 Constraints 510
13.6.5 High speed Token-Ring 514
13.6.6 Transmission formats 515
13.6.7 Medium access control 524
13.6.8 Logical link control 527
13.7 ReviewQuestio ns 528
x CONTENTS
14 Basic LAN Internetworking 531
14.1 Bridge Operations 531
14.1.1 Types of bridge 531
14.1.2 Network utilization 544
14.2 The Switching Hub 546
14.2.1 Basic components 546
14.2.2 Delay times 547
14.2.3 Key advantages of use 549
14.2.4 Switching techniques 549
14.2.5 Port address support 553
14.2.6 Switching architecture 556
14.2.7 High-speed port operations 557
14.2.8 Summary 558
14.3 Router Operations 558
14.3.1 Basic operation and use of routing tables 559
14.3.2 Networking capability 560
14.3.3 Communication, transport and routing protocols 561
14.3.4 Router classifications 563
14.3.5 Routing protocols 566
14.4 ReviewQue stions 575
15 Digital Transmission Systems and
Equipment 577
15.1 The T and E Carriers 578
15.1.1 Channel banks 578
15.2 T1 Multiplexers 596
15.2.1 Waveform-based voice digitization modules 597
15.2.2 Vocoding 598
15.2.3 Hybrid coding 601
15.2.4 T1 multiplexer employment 602
15.3 The T3 Carrier 605
15.3.1 T3 circuit types 606
15.3.2 Evolution 606
15.3.3 T3 framing 609
15.4 DDS, ASDS and KiloStream facilities 615
15.4.1 Applications 616
15.4.2 ASDS 616
15.4.3 KiloStream service 617
15.5 Integrated Services Digital Network (ISDN) 619
15.5.1 Concept behind ISDN 619
15.5.2 ISDN architecture 620
15.5.3 Network characteristics 621
15.5.4 ISDN layers 625
15.6 ReviewQue stions 628
16 Network Architecture 631
16.1 SNA Overview632
16.1.1 SNA elements 634
16.1.2 System Service Control Point (SSCP) 634
16.1.3 Network nodes 634
16.1.4 The physical unit 635
16.1.5 The logical unit 635
16.1.6 SNA network structure 635
16.1.7 Types of physical unit 637
CONTENTS xi

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16.1.8 Multiple domains 637
16.1.9 SNA layers 639
16.1.10 SNA developments 641
16.1.11 SNA sessions 641
16.2 Advanced Peer-to-Peer Networking (APPN) 644
16.2.1 APPC concepts 644
16.2.2 APPN architecture 645
16.2.3 Operation 646
16.3 TCP/IP 649
16.3.1 The rise of the Internet 650
16.3.2 The TCP/IP protocol suite 651
16.3.3 Applications 653
16.3.4 TCP/IP communications 663
16.3.5 The Internet Protocol (IP) 664
16.3.6 Domain Name Service 679
16.4 Internetworking 681
16.4.1 SNA gateway operations 682
16.4.2 Supporting multiple protocols 690
16.4.3 Data Link Switching 693
16.5 ReviewQuestio ns 694
17 Packet Networks 697
17.1 Packet Switching Overview 698
17.2 X.25 Networks 700
17.2.1 Development period 700
17.2.2 Need for PADs 700
17.2.3 X.25 layers 705
17.2.4 Methods of connection 708
17.2.5 Utilization costs 709
17.2.6 Tymnet 711
17.2.7 Network information 713
17.2.8 Features 713
17.2.9 Protocol conversion 715
17.2.10 LAN interconnectivity 716
17.3 Frame Relay 717
17.3.1 Comparison to X.25 717
17.3.2 Standards 719
17.3.3 Network access 720
17.3.4 Frame construction 721
17.3.5 Service parameters 729
17.3.6 FRAD features 734
17.3.7 Voice over Frame Relay 740
17.4 ReviewQuestio ns 745
18 Communications Software 749
18.1 Terminal Emulation Software Features 749
18.1.1 Hardware utilization 752
18.1.2 Software utilization 753
18.1.3 Operational consideration 754
18.1.4 Documentation 757
18.1.5 Dialing 757
18.1.6 Transmission 762
18.1.7 Performance efficiency 766
18.1.8 Performance flexibility 770
18.1.9 Security performance 772
xii CONTENTS
18.2 Terminal Emulation Program Examination 774
18.2.1 Procomm Plus for Windows 775
18.2.2 HyperTerminal 777
18.2.3 IBM PC/3270 780
18.3 Web Browsers 783
18.3.1 Microsoft Internet Explorer 784
18.3.2 LAN operation 788
18.4 ReviewQue stions 789
19 Fiber-Optic, Satellite and Wireless Terrestrial
Communications 791
19.1 Fiber-Optic Transmission Systems 792
19.1.1 System components 792
19.1.2 Transmission advantages 799
19.1.3 Limitations of use 801
19.1.4 Utilization economics 802
19.1.5 Carrier utilization 805
19.1.6 SONET 806
19.2 Satellite Communications Systems 810
19.2.1 Operation overview810
19.2.2 Satellite access 810
19.2.3 Very small aperture terminal (VSAT) 812
19.2.4 Lowearth orbit satellites 812
19.3 Wireless Terrestrial Communications 814
19.3.1 Cellular communications 814
19.3.2 Wireless LANs 820
19.4 ReviewQue stions 821
20 Evolving Technologies 823
20.1 ATM 823
20.1.1 Cell size 823
20.1.2 Scalability 824
20.1.3 Transparency 825
20.1.4 Traffic classification 825
20.2 The ATM Protocol Stack 825
20.2.1 ATM Adaptation Layer 825
20.2.2 The ATM Layer 826
20.2.3 Physical Layer 827
20.3 ATM Operation 827
20.3.1 Components 827
20.3.2 Network Interfaces 829
20.3.3 The ATM cell header 830
20.3.4 ATM connections and cell switching 833
20.4 Virtual Private Networking 835
20.4.1 Rationale for use 836
20.4.2 Reliability 837
20.4.3 Problem areas 837
20.5 ReviewQue stions 838

bibisweetie

it seems very good

deyi2008

好料，藏

dxl123

回复 1# spiderzhuzhi


   好东西啊，谢谢了。

胜利象征

谢谢分享！

chenls_2002

太全，只能泛泛而谈啦！

Ryggeor

thnx!