DATA COMMUNICATION PRINCIPLES For Fixed and Wireless Networks

Transcription

1 DATA COMMUNICATION PRINCIPLES For Fixed and Wireless Networks

2 DATA COMMUNICATION PRINCIPLES For Fixed and Wireless Networks Aftab Ahmad KLUWER ACADEMIC PUBLISHERS NEW YORK, BOSTON, DORDRECHT, LONDON, MOSCOW

3 ebook ISBN: Print ISBN: Kluwer Academic Publishers New York, Boston, Dordrecht, London, Moscow Print 2003 Kluwer Academic Publishers Dordrecht All rights reserved No part of this ebook may be reproduced or transmitted in any form or by any means, electronic, mechanical, recording, or otherwise, without written consent from the Publisher Created in the United States of America Visit Kluwer Online at: and Kluwer's ebookstore at:

4 NOTE TO INSTRUCTORS As an aid to instructors interested in teaching this book as a course, exercises suitable for use in a classroom setting are available by contacting the author at Aftab@ieee.org.

5 To my parents

6 Table of Contents Preface 1. Computer Communications Networks - Introduction 1.1. Main Components The Computer System The Communications System The Networking System 1.2. Network Development Example Three Role Players Network Design 1.3. Standardization Classification of Networks Example 1 - Communication of Voice Example 2 - File Transfer Local Area Networks (LANs) Wide Area Networks (WANs) Metropolitan Area Networks (MANs) 1.5. Network Protocol Architecture Protocols Standards Protocol Architecture 1.6. Example of a Protocol Architecture Open System 1.7. Summary 1.8. Review Questions 2. Network Architectures - Examples 2.1. The OSI Reference Model (OSI-RM) OSI-RM Characteristics and Terminology Communications Model within an OSI Node Communications Across the OSI Network Inter-layer communication OSI-RM Layer Definitions and Functions 2.2. The TCP/IP Protocol Suite The Internet Protocol (IP) The Transmission Control Protocol (TCP) The Application Protocols for the Internet Lower Layers of the Internet xv

7 x 2.3. The IEEE Wireless Local Area Network (IEEE WLAN) Local Area Networks Wireless Local Area Networks The Physical Layer (PHY) The Medium Access Control (MAC) Layer 2.4. Framework for Studying a Protocol Standardization of Protocols International Telecommunications Union (ITU) The Internet Society International Organization for Standardization (ISO) European Telecommunications Standards Institute (ETSI) American National Standard Institute (ANSI) Institute of Electrical and Electronic Engineers (IEEE) Summary Review Questions Network and User Data 3.1. The Network Data 3.2. The Physical Layer Data Sequence of Events and Definitions Modulation of data and signals Digital Encoding of Data Non-Return to Zero (NRZ) Multilevel Encoding Manchester Coding General Characteristics of Bit Encoding Zero-substitution and nb/nb Translation 3.3. Passband Modulation The Carrier Signal Analog Modulation 3.4. Digital Modulation Amplitude Shift Keying (ASK) Frequency Shift Keying (FSK) Phase Shift Keying (PSK) 3.5. The User Data Digital Transmission of Voice The Sampling Theorem Pulse Coded Modulation (PCM) Delta Modulation 3.6. Text and Numerical Data ASCII (American National Standard Code for Information Interchange) ISO (ISO Latin -1)

8 xi UCS (Universal multiple-octet coded Character Set) 3.7. Summary 3.8. Review Questions The Physical Layer 4.1. Channel Impairments Signal Attenuation Delay Distortion Noise Multipath 4.2. Transmission Media 4.3. Cables in data communications Twisted Pair Copper Cables Co-axial Cable Optical Fiber Cable (OFC) 4.4. The Wireless Media Characteristics Examples of Wireless Bands 4.5. Physical Layer Protocol Example: EIA-232-F Mechanical Characteristics Electrical Characteristics Functional Characteristics Procedural Characteristics PHY for IEEE Wireless Local Area Network WLAN Types Specification 122 Frequency Hopping Spread Spectrum (FH-SS) for 2.4 GHz Direct Sequence Spread Spectrum (DS-SS) for 2.4 GHz Specification Infrared PHY for IEEE WLAN 127 The Integrated Services Digital Network (ISDN) PHY 128 Review Questions Data Link Control Layer Functions and Procedures 5.1. Data Link Layer Functions Synchronization Addressing Modes Connection setup and termination Error Control Flow Control Link Control and Testing Multiplexing

9 xii 5.2. Synchronization Synchronous Transmission Asynchronous Transmission 5.3. Connection Setup and Termination 5.4. Addressing 5.5. Error Control Parity bit Block Error Check The Cyclic Redundancy Check (CRC) 5.6. Flow Control Stop-and-Wait (SnW) Flow Control The Sliding-windows (SW) Flow Control Mechanism Link Utilization of Window Flow Control Mechanisms Full-duplex Communications Using Window Flow Control 5.7. Flow Control Based Error Recovery Mechanisms Stop-and-Wait ARQ Go-Back-N ARQ Selective Reject ARQ Maximum Window Size Link Control and Testing Review Questions 6. Data Link Control Layer Protocol Examples 6.1. HDLC (High-level Data Link Control) Protocol 6.2. HDLC Frame Types 6.3. HDLC station types Primary station Secondary station Combined stations 6.4. Operation modes Normal Response Mode (NRM) Asynchronous Balanced Mode (ABM) Asynchronous Response Mode (ARM) Extended Modes 6.5. The HDLC Frame Flag Address Field Frame Check Sequence (FCS) 6.6. HDLC Protocol Operation Selection of Timeout Connection Setup and Termination Data Exchange 6.7. Asynchronous Transfer Mode (ATM) Protocol

10 xiii The ATM Cell 6.8. ATM Protocol Procedures Virtual circuit and the frame relay protocol Error Control 6.9. Medium Access Control (MAC) Layer for IEEE Wireless LANs Random Access in LANs Collision Avoidance The Distributed Coordination Function (DCF) MAC Frame Structure MAC Frame Types Review Questions Multiplexing and Carrier Systems 7.1. Analog and Digital Transmissions Analog and Digital Multiplexing Frequency Division Multiplexing (FDM) Frequency Division Duplexing (FDD) Time Division Multiplexing (TDM) Synchronous TDM Statistical TDM Statistical Versus Synchronous TDM The TDM Switch 7.2. Digital Carrier Systems 7.3. The DS-1 Carrier System Total Bit Rate Signaling Information Problems with T-1/E-1 Systems 7.4. Synchronous Optical Network/ Synchronous Digital Hierarchy 7.5. Digital Subscriber s Line (DSL) Integration With Telephone 7.6. Multiplexing at higher layers Multiple Protocols Per Layer With Connection-oriented Mode Multiple Connections Per Protocol Review Questions The Network and Higher Layer Functions 8.1. The Network Layer 8.2. Typical Functions of Network layer Connectionless Network Layers Connection-oriented Mode 8.3. The End-to-end Layers 8.4. X.25 Packet Layer Protocol

11 xiv X.25 Packet Types 8.5. Review Questions 9. Performance Models for Data Networks 9.1. The Network Performance 9.2. Performance of the Physical Layer Protocols Performance Improvement at PHY 9.3. Data Link Layer Performance Flow Control Procedures Error Control Procedures 9.4. Performance of the MAC Sublayer 9.5. Performance of the network and higher layers Connectionless and Connection-oriented Protocols QoS Differentiation in Connectionless Protocols Performance of End-to-end Protocols 9.6. System Simulation for Performance Prediction What is Simulation? Designing a Simulation Program Versus Using a Package 9.7. Performance of Wireless and Mobile Networks The Wireless Network Channel Resource Management in Wireless Networks Mobility Management in Mobile Networks 9.8. Review Questions References Index

12 Preface In spite of the fact that the electronic communication systems started as data communication systems, much of their advancement has been in the field of voice. For decades, the Public Switched Telecommunications Network (PSTN) has set standards for communication of information all over the world. Things started changing only towards the closing of 80s when Internet and mobile systems offered competition in some ways. Despite the continued importance of PSTN, these two technologies have found their niche to sustain and grow. Wireless networks offer mobility as an add-on and the Internet brought the web, and file transfer. Though PSTN could provide the Internet-like services, it has its limitations due to its circuit switched nature. For some time, we have used the term data to distinguish the storeand-forward type of information (carried by Internet) from voice. This is because the Internet uses store and forward mechanism of transmission, which is not quite suitable for interactive, real-time communication, such as voice. In this way, PSTN, Internet and wireless networks have not quite stood in each other s way. PSTN offering toll-quality digitized voice, wireless cellular networks adding mobility to voice and data, with some degradation in quality, and the Internet allowing enormous sharing power using store-andforward protocols for data communications. Ever since their debut, all these fields of technologies have made progress, with PSTN being steady and slow, Internet being slow first and then exploding, and the wireless technology making a steady progress at a rapid speed. It is only very recently that there is a slowing in wireless market. However, with ever-increasing products in license-free wireless band, this is projected to change soon. The emphasis, however, may shift from voice to web-based applications. In fact, with the availability of high-speed data links, voice is becoming part of data. Traditionally, data was generated and processed by mainframe computers. Users accessed the computer resources through a network of dumb terminals. With developments in microchip fabrication, and reduction in memory cost, processing power shifted to terminals making them intelligent, and then as powerful as the computer itself. These days, desktop computers are mostly the processing powerhouses that mainframes once were. And these machines are capable of processing data at speeds that could easily take care of the requirements of interactive information. The introduction of IMT-2000 systems in wireless arena has reduced the gap in wireless, voice and data. Now we talk about multimedia wireless networks that could use Internet as a backbone. Consequently, the entire meaning of data and communications has changed to include real-time information and wireless networks. For a student and practitioner of data networks, the fundamental concepts of networks with

13 latest technology have become more important to master than ever before. Of course, by latest technologies, we mean packet switching and wireless data networks. This book has been written with these developments in mind. The primary audience of this book is the students, senior undergraduate or first year graduate, and personnel in the fields of computer science, electrical engineering, telecommunications, information systems, and other majors that require an elementary to medium level knowledge of data communications principles. Much of the material has been used to offer graduate and undergraduate level courses in some of the above areas. The book is a compilation from lecture notes with some addition. The approach adopted is rather straightforward; define a data network as a computer communication network that could be best understood with the help of the Open System Interconnection Reference Model (OSI-RM), recommended by the International Organization for Standardization (ISO). The OSI networking standards are not nearly as prolific in use as the Internet protocols, still the pedagogical value of the reference model makes it a good choice for a first course on data communications. Besides, the main differences between the OSI and TCP/IP networks exist at layers above the data link control. The book emphasizes only on the bottom two layers, therefore making it useful for people who would work with TCP/IP, OSI or Local Area Network. Examples of protocols are chosen, among others, from the wireless data networks. This broadens the scope of the application of work. Another salient feature of the book is a chapter on performance modeling of data networks. This is a topic that results in most innovations in technology, and yet is not easy to introduce at an elementary level. Every try has been made to let the reader appreciate the models and metrics of performance measures. Separate discussions have been included about the wireless cellular network performance and simulation of networks. Here s the organization of chapters. A major part of the book is dedicated to the understanding of data and its transmission across a single link. However, to put things in perspective, the first two chapters discuss the protocol architectures in general. Examples of OSI-RM, TCP/IP suite and IEEE Wireless LAN are discussed under this topic. Chapter 3 discusses data in most of its forms, from analog form to characters and as data exists within the network (baseband signal, passband modulated signal, to protocol data unit). Chapter 4 discusses physical layer characteristics and protocol examples. Among the protocol examples, a discussion on the physical layers of IEEE Wireless LAN has been included. Simple descriptions of some important concepts have been provided here, such as the need of physical medium dependent (PMD) sublayer, and terms such as spread spectrum communications. Chapter 5, a rather lengthy one, is devoted to the discussion of functions and duties of the data link control layer. Chapter 6 builds on Chapter 5 using example protocols. HDLC, ATM and IEEE MAC have been discussed. Chapter 7 is on multiplexing and xvi

14 xvii carrier systems, that make the backbone of transmission systems. T-1, though receding in its deployment, still makes an excellent case of studying a carrier system. Discussions on SONET/SDH and DSL are also included in this chapter. Chapter 8 provides a one shot treatment of the layers above the link layer. Terminology pertinent to these layers in introduced here. Chapter 9 completes the understanding, albeit at an elementary level, by discussing the topic of performance. The material in the book, proposed to be covered in one semester, could be adjusted according to the specialty of the audience. In the end, I would like to thank and acknowledge numerous anonymous people who have contributed to this field in many ways. I have used many books, articles, websites and documents of numerous companies and standardization agencies in learning the subject, some repeatedly. Thanks are due to the reviewers of the manuscript. Also, thanks are due to the companies that designed software and hardware that went in preparing the manuscript. I also take this opportunity to thank Alex Green of the Kluwer Academic Publishers for his persistence in making this book a reality. Thanks are due to Melissa Sullivan and Deborah Doherty of the Kluwer Academic Publishers for help with formatting the manuscript. Most of all, I am much indebted to my wife for her patience during the preparation of the manuscript, especially during the final stage. Aftab Ahmad