JLM.MJ i j J L i Standards,

Implementation, and Architecture

Charles K. Summers

Series Editor-in-Chief

Saba Zamir

(g) CRC Press

Boca Raton London New York Washington, D.C.

Table of Contents

Acknowledgments xi Acronyms and Abbreviations xiii Introduction xvii

1 Analog and Digital Communication 1.1 Communication Forms 1

1.1.1 Analog 2 1.1.2 Digital Transmission Coding 3

1.2 Transmission Media 5 1.2.1 Copper Wiring 6 1.2.2 Other Transmission Media 6

1.3 Switching and Routing 7 1.3.1 Basics of Switching 8 1.3.2 Circuit-switches and Packet-switches 9 1.3.3 Routers 11

1.3.3.1 LANs and WANs 11 1.3.3.2 Functions of the Router 12

1.4 Multiplexing 12 1.5 Infrastructure Limits 13

1.5.1 Distance Limitations on Local Loops 15 1.5.2 Loading Coils 15 1.5.3 Repeaters, Amplifiers, and Line Extenders 16 1.5.4 BridgedTaps 16 1.5.5 Digital Loop Carriers (DLCs) 16 1.5.6 Summary 17

1.6 Bottlenecks 17 1.6.1 Host I/O Capacity 17 1.6.2 Access Line Capacity 18 1.6.3 Long-distance Line Capacity 19 1.6.4 Network Saturation 19 1.6.5 Server Access Line and Performance 19 1.6.6 Summary 19

2 The xDSL Family of Protocols 2.1 From Digital to Analog 21 2.2 Digital Modems 22 2.3 The ITU-T, ADSL, and ISDN 23 2.4 ADSL Standardization 24

2.4.1 Standards Bodies 25

2.4.2 ADSL Standards Bodies 25 2.4.2.1 ADSL Forum and UAWG 26 2.4.2.2 ANSI 26 2.4.2.3 ETSI 27 2.4.2.4 ITU-T 27

2.5 The xDSL Family of Protocols 27 2.5.1 56K Modems 31 2.5.2 BRI ISDN (DSL) 31

2.5.2.1 Physical Layer 32 2.5.2.2 Switching Protocol 35 2.5.2.3 Data Protocols 37

2.5.3 IDSL 37 2.5.4 HDSL/HDSL2 38

2.5.4.1 Signaling Using Channel Associated Signaling 40 2.5.4.2 Signaling Using Primary Rate Interface ISDN 41 2.5.4.3 HDSL2 or SHDSL 41

2.5.5 SDSL 42 2.5.6 ADSL/RADSL 42 2.5.7 CDSL/ADSL "Lite" 43 2.5.8 VDSL 45

2.6 Summary of the xDSL Family 45

3 The ADSL Physical Layer Protocol 3.1 CAP/QAM 47 3.2 Discrete Multitone 49 3.3 ANSIT1.413 50

3.3.1 Bearer Channels 51 3.3.2 ADSL Superframe Structure 55

3.3.2.1 Fast Data and Interleaved Data... 57 3.3.2.2 Fast Byte 58 3.3.2.3 Sync Byte and sc Bits 58 3.3.2.4 Indicator Bits 58 3.3.2.5 CRCbits 60

3.3.3 Embedded Operations Control 60 3.4 ADSL "Lite" 62 3.5 ATU-R Versus ATU-C 64 3.6 DSLAM Components 64

4 Architectural Components for Implementation 4.1 Open Systems Interconnection Model (OSI) 67

4.1.1 Layer 1 (Physical Layer) 68 4.1.2 Layer 2 (Data Link Layer) 69 4.1.3 Layer 3 (Network Layer) 70 4.1.4 Layer 4 (Transport Layer) 71 4.1.5 Upper Layers 71

4.1.6 Interlayer Primitives 72 4.1.7 Protocol Modularity 72

4.2 Hardware Components and Interactions 73 4.2.1 Interface Chip 74 4.2.2 Physical Layer Semiconductors 75 4.2.3 System Contiguration Design 75

4.2.3.1 Host-controlled Systems 76 4.2.3.2 Coprocessor Systems 77 4.2.3.3 Standalone Systems 77

4.3 Protocol Stack Considerations 77 4.3.1 Signaling 77 4.3.2 Interworking 78 4.3.3 Stack Combinations 78

4.4 Application Access 79 4.4.1 Host Access 79 4.4.2 Control Systems 80

5 Hardware Access and Interactions 5.1 Semiconductor Access 82

5.1.1 Memory Maps 84 5.1.2 I/O Requests 84 5.1.3 Registers 84 5.1.4 Indirect Register Access 85 5.1.5 Data Movement 85 5.1.5.1 FIFOs 85 5.1.5.2 Buffer Descriptors 86

5.2 Low-Level Drivers 87 5.2.1 Primitive Interfaces 88 5.2.2 Interrupt Servicing and Command Handling 88 5.2.3 Synchronous and Asynchronous Messages 88

5.3 State Machines 89 5.3.1 States 89 5.3.2 Events 90 5.3.3 Actions 91 5.3.4 State Machine Specifications 91 5.3.5 Methods of Implementation 92 5.3.6 Example of a Simple State Machine 92

5.4 ADSL Chipset Interface Example 94

6 Signaling, Routing, and Connectivity 6.1 Signaling Methods 98

6.1.1 Analog Devices 98 6.1.2 Channel Associated Signaling (CAS) 101 6.1.3 Q.921/Q.931 Variants 101

6.2 Routing Methods 102

6.2.1 Internet Protocol 103 6.2.2 Permanent Virtual Circuits 104

6.2.2.1 ATM Cells 104 6.2.2.2 Frame Relay 105

6.3 Signaling Within the DSLAM 105

7 ATM Over ADSL 7.1 B-ISDN (ATM) History, Specifications, and Bearer Services 108

7.1.1 Broadband Bearer Services 108 7.1.2 Specific Interactive and Distribution Services 109

7.2 B-ISDN OSI Layers 110 7.3 ATM Physical Layer 111 7.4 ATM Layer 111

7.4.1 ATM Cell Formats 113 7.4.2 Virtual Paths and Virtual Channels 115

7.5 ATM Adaptation Layer 116 7.5.1 AAL Type 1 118 7.5.2 AAL Type 5 118

7.6 ATM Signaling 120 7.6.1 Lower Layer Access 120 7.6.2 General Signaling Architecture 120

7.6.2.1 User-side States 121 7.6.2.2 Network-side States 122

7.6.3 B-ISDN Message Set 123 7.6.4 Information Elements 125

7.7 Summary of ATM Signaling 126 7.8 System Network Architecture Group (SNAG) 126

8 Frame Relay, TCP/IP, and Proprietary Protocols 8.1 Frame Relay 129

8.1.1 Frame Relay Data Link Layer 130 8.1.2 Link Access Protocol for Frame Relay 131

8.1.2.1 Address Field 131 8.1.2.2 Congestion Control 133 8.1.2.3 Control Field 134

8.1.3 Data Link Core Primitives 134 8.1.4 Network Layer Signaling for Frame Relay 136 8.1.5 MultiProtocol Over Frame Relay 137

8.2 Internet Protocol 138 8.2.1 The Data Link Layer 138 8.2.2 IP Datagrams 139

8.3 Transmission Control Protocol 141 8.3.1 TCP Virtual Circuits 142 8.3.2 TCP Header Fields 142 8.3.3 TCP Features 144

8.4 Proprietary Protocol Requirements 144 8.4.1 Data Integrity 144 8.4.2 Data Identification 145 8.4.3 Data Acknowledgment 145 8.4.4 Data Recovery 146 8.4.5 Data Protocol 146

9 Host Access 9.1 Ethernet 148

9.1.1 History 149 9.1.2 OSI Model Layer Equivalents 149 9.1.3 The Medium Access Control (MAC) 150 9.1.4 The Ethernet Frame 152 9.1.5 Physical Medium and Protocols 154 9.1.6 MACBridges 254

9.2 Universal Serial Bus 155 9.2.1 Goals of the USB 155 9.2.2 USB Architecture 156

9.3 Motherboard Support 157 9.3.1 Data Bus Extension 157 9.3.2 Microprocessor Direct Access 158

10 Architectural Issues and Other Concerns 10.1 Multi-Protocol Stacks 160

10.1.1 Architectural Choices 160 10.1.2 Software Implementation 161

10.1.2.1 "Physical Layer" Replacement 162 10.1.2.2 Coordination Tasks 163 10.1.2.3 Data Structure Use 164

10.2 Signaling 165 10.3 Standardization 165 10.4 Real-Time Issues 166

10.4.1 Bottlenecks 166 10.5 Migration Needs and Strategies 167

10.5.1 Replacement of Long-Distance Infrastructure 168 10.5.2 FTTN, FTTC, and VDSL 168

10.6 Summary of Issues and Options 170

References and Selected Bibliography 173 ITU-Rcommendations 173 Other Technical References 174 Selected Internet Uniform Resource Locators (URLs) 175 Selected Bibliography 175

Index 177