Data Communication and Computer Network Data Communication and Computer Network About the Tutorial This tutorial gives very good understanding on Data Communication and Computer Networks. After completing this tutorial, you will find yourself at a moderate level of expertise in knowing DCN, from where you can take yourself to next levels. Audience This tutorial is prepared for the beginners to help them understand Data Communication and Computer Networks. Prerequisites Before proceeding with this tutorial, you need a basic understanding of Computer. You should know the basics of input and output devices, primary and secondary memory, and operating system. Disclaimer & Copyright  Copyright 2014 by Tutorials Point (I) Pvt. Ltd. All the content and graphics published in this e-book are the property of Tutorials Point (I) Pvt. Ltd. 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If you discover any errors on our website or in this tutorial, please notify us at [email protected]. i Data Communication and Computer Network Contents About the Tutorial ..................................................................................................................................... i Audience .................................................................................................................................................... i Prerequisites .............................................................................................................................................. i Disclaimer & Copyright .............................................................................................................................. i Contents ................................................................................................................................................... ii 1. OVERVIEW ............................................................................................................................ 1 Classification of Computer Networks ........................................................................................................ 1 Geographical Span .................................................................................................................................... 1 Inter-Connectivity ..................................................................................................................................... 1 Administration .......................................................................................................................................... 2 Network Architecture ............................................................................................................................... 2 Network Applications ............................................................................................................................... 2 2. TYPES OF COMPUTER NETWORKS ........................................................................................ 3 Personal Area Network ............................................................................................................................. 3 Local Area Network................................................................................................................................... 3 Metropolitan Area Network ..................................................................................................................... 4 Wide Area Network .................................................................................................................................. 5 Internetwork............................................................................................................................................. 6 3. NETWORK LAN TECHNOLOGIES ............................................................................................ 8 Ethernet .................................................................................................................................................... 8 Fast-Ethernet ............................................................................................................................................ 8 Giga-Ethernet ............................................................................................................................................ 8 Virtual LAN................................................................................................................................................ 9 4. COMPUTER NETWORK TOPOLOGIES ................................................................................... 10 Point-to-Point ......................................................................................................................................... 10 Bus Topology .......................................................................................................................................... 10 ii Data Communication and Computer Network Star Topology .......................................................................................................................................... 11 Ring Topology ......................................................................................................................................... 12 Mesh Topology ....................................................................................................................................... 13 Tree Topology ......................................................................................................................................... 14 Daisy Chain ............................................................................................................................................. 15 Hybrid Topology...................................................................................................................................... 15 5. COMPUTER NETWORK MODEL ........................................................................................... 17 Layered Tasks.......................................................................................................................................... 17 OSI Model ............................................................................................................................................... 18 Internet Model ....................................................................................................................................... 19 6. COMPUTER NETWORK SECURITY ........................................................................................ 20 Secret Key Encryption ............................................................................................................................. 21 Public Key Encryption ............................................................................................................................. 21 Message Digest ....................................................................................................................................... 21 7. PHYSICAL LAYER INTRODUCTION ........................................................................................ 22 Signals ..................................................................................................................................................... 22 Transmission Impairment ....................................................................................................................... 22 Transmission Media ................................................................................................................................ 23 Channel Capacity .................................................................................................................................... 23 Multiplexing............................................................................................................................................ 24 Switching ................................................................................................................................................ 24 8. DIGITAL TRANSMISSION ...................................................................................................... 25 Digital-to-Digital Conversion ................................................................................................................... 25 Line Coding ............................................................................................................................................. 25 Unipolar Encoding ................................................................................................................................... 26 Polar Encoding ........................................................................................................................................ 26 Bipolar Encoding ..................................................................................................................................... 28 iii Data Communication and Computer Network Block Coding ........................................................................................................................................... 28 Analog-to-Digital Conversion .................................................................................................................. 29 Sampling ................................................................................................................................................. 29 Quantization ........................................................................................................................................... 29 Encoding ................................................................................................................................................. 30 Transmission Modes ............................................................................................................................... 30 9. ANALOG TRANSMISSION ..................................................................................................... 32 Digital-to-Analog Conversion .................................................................................................................. 32 Analog-to-Analog Conversion ................................................................................................................. 34 10. TRANSMISSION MEDIA........................................................................................................ 38 Magnetic Media ...................................................................................................................................... 38 Twisted Pair Cable .................................................................................................................................. 38 Coaxial Cable .......................................................................................................................................... 39 Power Lines ............................................................................................................................................ 40 Fiber Optics ............................................................................................................................................. 40 11. WIRELESS TRANSMISSION ................................................................................................... 42 Radio Transmission ................................................................................................................................. 42 Microwave Transmission ........................................................................................................................ 43 Infrared Transmission ............................................................................................................................. 44 Light Transmission .................................................................................................................................. 44 12. MULTIPLEXING .................................................................................................................... 46 Frequency Division Multiplexing ............................................................................................................. 46 Time Division Multiplexing ..................................................................................................................... 46 Wavelength Division Multiplexing .......................................................................................................... 47 Code Division Multiplexing ..................................................................................................................... 48 13. SWITCHING ......................................................................................................................... 49 Circuit Switching ..................................................................................................................................... 49 iv Data Communication and Computer Network Message Switching.................................................................................................................................. 50 Packet Switching ..................................................................................................................................... 51 14. DATA LINK LAYER INTRODUCTION ...................................................................................... 53 Functionality of Data-link Layer .............................................................................................................. 53 15. ERROR DETECTION AND CORRECTION ................................................................................ 55 Types of Errors ........................................................................................................................................ 55 Error Detection ....................................................................................................................................... 56 Error Correction ...................................................................................................................................... 57 16. DATA LINK CONTROL AND PROTOCOLS .............................................................................. 59 Flow Control ........................................................................................................................................... 59 Error Control ........................................................................................................................................... 60 17. NETWORK LAYER INTRODUCTION ....................................................................................... 64 Layer-3 Functionalities ............................................................................................................................ 64 Network Layer Features .......................................................................................................................... 64 18. NETWORK ADDRESSING ...................................................................................................... 65 19. NETWORK ROUTING ........................................................................................................... 67 Unicast routing ....................................................................................................................................... 67 Broadcast routing ................................................................................................................................... 68 Multicast Routing.................................................................................................................................... 69 Anycast Routing ...................................................................................................................................... 69 Unicast Routing Protocols ....................................................................................................................... 70 Multicast Routing Protocols .................................................................................................................... 70 Routing Algorithms ................................................................................................................................. 71 20. INTERNETWORKING ............................................................................................................ 72 Tunneling ................................................................................................................................................ 72 Packet Fragmentation ............................................................................................................................. 73 v Data Communication and Computer Network 21. NETWORK LAYER PROTOCOLS ............................................................................................ 75 Address Resolution Protocol (ARP) ......................................................................................................... 75 Internet Control Message Protocol (ICMP) .............................................................................................. 76 Internet Protocol Version 4 (IPv4) ........................................................................................................... 76 Internet Protocol Version 6 (IPv6) ........................................................................................................... 77 22. TRANSPORT LAYER INTRODUCTION .................................................................................... 78 Functions ................................................................................................................................................ 78 End-to-End Communication .................................................................................................................... 78 23. TRANSMISSION CONTROL PROTOCOL ................................................................................. 80 Features .................................................................................................................................................. 80 Header .................................................................................................................................................... 80 Addressing .............................................................................................................................................. 82 Connection Management........................................................................................................................ 82 Bandwidth Management ........................................................................................................................ 83 Error Control and Flow Control ............................................................................................................... 84 Multiplexing............................................................................................................................................ 84 Congestion Control ................................................................................................................................. 84 Timer Management ................................................................................................................................ 85 Crash Recovery ....................................................................................................................................... 85 24. USER DATAGRAM PROTOCOL ............................................................................................. 87 Requirement of UDP ............................................................................................................................... 87 Features .................................................................................................................................................. 87 UDP Header ............................................................................................................................................ 87 UDP application ...................................................................................................................................... 88 25. APPLICATION LAYER INTRODUCTION .................................................................................. 89 26. CLIENT-SERVER MODEL ....................................................................................................... 91 vi Data Communication and Computer Network Communication ...................................................................................................................................... 92 27. APPLICATION PROTOCOLS .................................................................................................. 94 Domain Name System ............................................................................................................................. 94 Simple Mail Transfer Protocol ................................................................................................................. 94 File Transfer Protocol .............................................................................................................................. 94 Post Office Protocol (POP) ...................................................................................................................... 95 Hyper Text Transfer Protocol (HTTP) ....................................................................................................... 95 28. NETWORK SERVICES ........................................................................................................... 96 Directory Services ................................................................................................................................... 96 File Services ............................................................................................................................................ 96 Communication Services ......................................................................................................................... 97 Application Services ................................................................................................................................ 97 vii 1. OVEDRataV CoImEmuWnicat ion and Computer Network A system of interconnected computers and computerized peripherals such as printers is called computer network. This interconnection among computers facilitates information sharing among them. Computers may connect to each other by either wired or wireless media. Classification of Computer Networks Computer networks are classified based on various factors. They include:  Geographical span  Inter-connectivity  Administration  Architecture Geographical Span Geographically a network can be seen in one of the following categories:  It may be spanned across your table, among Bluetooth enabled devices, Ranging not more than few meters.  It may be spanned across a whole building, including intermediate devices to connect all floors.  It may be spanned across a whole city.  It may be spanned across multiple cities or provinces.  It may be one network covering whole world. Inter-Connectivity Components of a network can be connected to each other differently in some fashion. By connectedness we mean either logically, physically, or both ways.  Every single device can be connected to every other device on network, making the network mesh.  All devices can be connected to a single medium but geographically disconnected, created bus-like structure.  Each device is connected to its left and right peers only, creating linear structure. 1 Data Communication and Computer Network  All devices connected together with a single device, creating star-like structure.  All devices connected arbitrarily using all previous ways to connect each other, resulting in a hybrid structure. Administration From an administrator’s point of view, a network can be private network which belongs a single autonomous system and cannot be accessed outside its physical or logical domain. A network can be public, which is accessed by all. Network Architecture Computer networks can be discriminated into various types such as Client-Server, peer-to-peer or hybrid, depending upon its architecture.  There can be one or more systems acting as Server. Other being Client, requests the Server to serve requests. Server takes and processes request on behalf of Clients.  Two systems can be connected Point-to-Point, or in back-to-back fashion. They both reside at the same level and called peers.  There can be hybrid network which involves network architecture of both the above types. Network Applications Computer systems and peripherals are connected to form a network. They provide numerous advantages:  Resource sharing such as printers and storage devices  Exchange of information by means of e-Mails and FTP  Information sharing by using Web or Internet  Interaction with other users using dynamic web pages  IP phones  Video conferences  Parallel computing  Instant messaging 2