Information Technology Class-XII Past Paper PDF

BUREAU’S HIGHER SECONDARY INFORMATION TECHNOLOGY Class-XII Prescribed by Council of Higher Secondary Education, Odisha, Bhubaneswar BOARD OF WRITERS Ranjan Kumar Bal...

BUREAU’S HIGHER SECONDARY INFORMATION TECHNOLOGY Class-XII Prescribed by Council of Higher Secondary Education, Odisha, Bhubaneswar BOARD OF WRITERS Ranjan Kumar Bal Department of Physics B.J.B. Junior College, Bhubaneswar Ajay Kumar Mishra Dhruba Charan Pradhan Department of Computer Science Department of Computer Science P.N. Autonomous College, Khordha OAVS, Th. Rampur, Kalahandi REVIEWER Nrusingha Charan Samal Retired Reader in Physics Published by THE ODISHA STATE BUREAU OF TEXTBOOK PREPARATION AND PRODUCTION PUSTAK BHAVAN, BHUBANESWAR Published by : The Odisha State Bureau of Textbook Preparation and Production Pustak Bhavan, Bhubaneswar, Odisha, India. First Edition : 2017 / 5000 Publication No : 198 ISBN : 978-81-8005-391-7 © Reserved by The Odisha State Bureau of Textbook Preparation and Production, Bhubaneswar. No part of this publication may be reproduced in any form without the prior written permission of the publisher. Typesetting and Designed by : Print-Tech Offset Pvt. Ltd., Bhubaneswar Printed at : Jagannath Process Pvt. Ltd., Cuttack Price : ` 120/- (Rupees One Hundred Twenty Only)  Foreword Twenty first century society is learning, sharing and innovating in a pace that would be only second to the human thought process. Advent of Information and Communication Technology (ICT) has leap fogged the process of computing and communicating among the world society. The ICT policies for the Higher Secondary curriculum aim at augmenting creativity and promote global competitiveness. Now the aim is to promote critical thinking, collaborative learning and multi discipline problem-solving skills among the budding students ready to plunge in to the professional or vocational courses. The curriculum of “Information Technology” has been revised accordingly with focus on rapid application development using IDE, data processing and domain-specific applications, e.g. e-Governance, e-Business and e-Learning. Further the use of open source software is being encouraged. The text book of Information Technology, Class-XI has been published by the Bureau. The text book for Class-XII is now ready. In the Syllabus of IT for Class- XII, a unit on Networking has been introduced. Like the book for Class-XI, the RDBMS (Relational Database Management System) and IDE uses MYSQL in place of MS-Access and IDE based programming is done, by using Java in place of VB. It is just a continuation of the Class-XI course. A unit on IT Applications has been continued with the focus on designing both front end and back end with proper data connectivity. A brief but valuable idea about electronic transaction in India has been included at the end of this book as an appendix, which may be of tremendous help for every stake holder. I record my sincere thanks to the Council for allowing the Bureau to publish the text book and I do hereby express my appreciation and gratitude to the writers, for their cooperation and diligence in preparing the manuscript of this book. My special thanks go to Prof. N.C. Samal for meticulously reviewing the contents of the book before publication. Finally, I could not but extend my appreciation to the officers and staff of Bureau, and especially to Sri Biraja Bhusan Mohanty, Dy. Director of the Bureau for his untiring efforts to make this new version press ready. Further, I shall be very happy to acknowledge the suggestions regarding any correction or improvement of the from its readers. I hope all success for the book. Sri Umakanta Tripathy Director  Preface Information Technology that refers to the convergence of computer, communication and content technologies plays catalytic role in emergence of new socio-economic applications. Need of introducing IT as an elective subject to all the students of Arts, Commerce and Science stream was needed to build problem-solving skills among the students just before they enter the professional courses. Accordingly the first part of Textbook on IT was published as per the syllabus of the CHSE (Odisha) last year meant to be taught during the First Year of the Higher Secondary Class. In this Second part, some previous topics are revisited so as to make it a seam less transition for students. These two volumes will help the students to better prepare for careers in various industries requiring IT tools and applications. In this new version, we have introduced Open Standards and Open Source aims at Vendor Neutrality of tools, Creative computing and Collaborative Learning environment, development of Front End Interface, Back End Database and connectivity of both, so that a student would get a complete feel of Application Development. Emphasis has been given for better awareness of Cyber Laws to adopt good ethical practice, while working on-line. In this era of on-line financial transactions, the students should be doubly alert in respect of on-line frauds. Finally a contemporary overview of ‘Cashless Transactions in India’ is provided at the end of this book in shape of an Appendix, to help the student community to participate in spreading the idea of Less-Cash Economy in the country. The authors would like to express their deep sense of appreciation to the expertise, understanding and kindness displayed by the Director Sri Umakant Tripathy, Dy Director Sri Biraja Bhusan Mohanty and staff of the Bureau in the preparation of this book. Authors are grateful to Dr Brundaban Pradhan, Lecturer in Physics, B.J.B. Junior College, Bhubaneswar and Smt. Mrunalinee Patnaik of Rama Devi Women’s College, Bhubaneswar for providing valuable logical and material support during the preparation of this book. Akshay Tritiya Authors The 29th April, 2017  CHSE SYLLABUS Class - XII (IT Syllabus - 2016) Unit 1 : Networking and Open Standards : (25 periods / 30 mark) (i) Computer Networking: (08 periods / 10 mark) Networking-a brief overview; Network Devices (Hub, Switch, Bridge, Router, Repeater, Gateway) and their functions, Types of network (LAN, MAN, WAN, PAN), Network Topologies (Star, Ring, Bus, Tree), Communication Media:-Wired Technologies (Co-Axial, Ethernet Cable, Optical Fiber), Wireless Technologies (Blue Tooth, Infrared, Microwave, Radio Link, Satellite Link) (ii) Internet and its Application: (12 periods / 10 mark) Internet- an overview, Internet backbone, Internet access (Dial- Up, Direct, Broadband connections), Role of ISP, Internet Protocols (TCP/IP, HTTP, FTP, TELNET, WAIS, GOPHER), Internet Addressing (IP Address, Domain name, MAC (Media Access Control), Internet Application (Web Browser & Search Engines, URL, WWW, Web pages & Web sites, SMS, Voice Mail, Electronic Mail, Chat, IRC, Video Conferencing), Wireless/ Mobile Communication (GSM, CDMA, WLL, 3G, 4G)  (iii) Network Security on Internet: (05 periods / 10 mark) Threats and prevention from virus, Use of Cookies, Firewall, Digital Signature, Cyber Crimes (Hacking, On-line-Fraud, Pornography, Snooping, Spooling, Cyber Stalking, Software piracy), Cyber Laws Unit 2 : Programming : (40 periods / 16 mark) Review of 1st Year Course; (i) Programming Fundamentals: (28 periods / 10 mark) Basic concept of Access specifier for class members (data members and methods), Basic concept of Inheritance, Commonly used libraries:- String class methods [toString(), concat(), length(), toLowerCase(), toUpperCase(), trim(), substring()], Math class methods [pow(), round()], Accessing MySQL database using ODBC/JDBC to connect with database (ii) HTML based web pages covering basic tags: (12 periods / 06 mark) HTML, DHTML, TITLE, BODY, H1..H6, Paragraph (P), Line Break (BR), Section Separator (HR), FONT, TABLE, LIST (UL, OL), FORM, Creating and accessing static & dynamic pages using HTML, DHTML and introduction to XML. Unit 3 : Relational Database Management System : (30 periods / 14 mark) Review of RDBMS from 1st Year Course  (i) Database Fundamentals : (20 periods / 08 mark) Concept of Database Transaction, Committing and revoking a Transaction using COMMIT and ROLLBACK, Grouping Records (GROUP BY), Group functions [ MAX(), MIN(), AVG(), SUM(), COUNT(); using COUNT(*), DISTINCT clause with COUNT; Group Functions and Null Values, Displaying Data From Multiple Tables (Cartesian product, Union, concept of Foreign Key, Equi-Join (ii) Introduction to MySQL : (10 periods / 06 mark) Working with NULL values, ORDER BY clause (sorting in ascending and descending order, sorting by Column Alias Name, sorting of multiple columns), Manipulating data of a table/relation (UPDATE command to change existing data of a table, DELETE command for removing rows from a table), Re- structuring a table (ALTER Table for adding new columns / deleting existing columns, DROP Table for deleting a table); String functions:- ASCII( ), CHAR( ), CONCAT( ), INSTR( ), LCASE( ), UCASE( ), LENGTH( ), LTRIM( ), MID( ), RIGHT( ), RTRIM( ), TRIM( ), SUBSTR( ); Mathematical functions:- POWER( ), ROUND( ), TRUNCATE( ); Date & Time functions:- CURDATE( ), MONTH( ), DAYOFMONTH( ), DAYOFWEEK( ), DAYOFYEAR( ), NOW( ), SYSDATE( ); Unit 4 : IT Applications : (10 periods / 10mark) (i) e-Business: Definition, e-Commerce, Types of e-Commerce & their benefits, e-Business web sites & their salient features, societal impact & challenges of e-Business (ii) Front-end Interface: Introduction; content and features; identifying and using appropriate components (Text Box, Radio Button, Checkbox, List, etc.) for data entry, validation and display. (iii) Back-end Database: Introduction and its purpose, exploring the requirement of tables and its essential attributes. (iv) Development of Database: Demonstration and development of appropriate Front-end interface and Back-end Database for e-Governance applications. n n n  CONTENTS Unit 1: Networking Pages Chapter - 1 Computer Networking : 1.1 - 1.28 Networking-a brief overview; Network Devices and their functions: Hub, Switch, Bridge, Router, Repeater, Gateway Types of network: LAN, MAN, WAN, PAN Network Topologies: Star, Ring, Bus, Tree Communication Media: Wired Technologies: Co-Axial, Ethernet Cable, Optical Fiber Wireless Technologies: Blue Tooth, Infrared, Microwave, Radio Link, Satellite Link Chapter - 2 Internet and its Application : 2.1 - 2.40 Internet- an overview; Internet backbone Internet access : Dial-Up, Direct, Broadband connections Role of ISP Internet Protocols : TCP/IP, HTTP, FTP, TELNET, WAIS, GOPHER Internet Addressing: IP Address, Domain name, MAC (Media Access Control) Internet Application: Web Browser & Search Engines, URL, WWW, Web pages & Web sites, SMS, Voice Mail, Electronic Mail, Chat, IRC, Video Conferencing Wireless/Mobile Communication: GSM, CDMA, WLL, 3G, 4G Chapter - 3 Network Security on Internet : 3.1 - 3.36 Threats and prevention from virus, Use of Cookies, Firewall, Digital Signature, Cyber Crimes: Hacking, On-line-Fraud, Pornography, Snooping, Spooling, Cyber Stalking, Software piracy Cyber Laws Unit 2 : Programming Chapter - 4 Programming Fundamentals : 4.1 - 4-28 Basic concept of Access specifier for class members (data members and methods) Basic concept of Inheritance, Commonly used libraries : String class methods: toString( ), concat( ), length( ), toLowerCase( ), toUpperCase( ), trim( ), substring( ) Math class methods: pow( ), round( ) Accessing MySQL database using ODBC/JDBC to connect with database Chapter - 5 HTML based web pages covering basic tags : 5.1 - 5.40 HTML, DHTML, TITLE, BODY, H1- - -H6, Paragraph (P), Line Break (BR), Section Separator (HR), FONT, TABLE, LIST (UL, OL), FORM, Creating and accessing static & dynamic pages using HTML, DHTML Introduction to XML Unit 3 : Relational Database Management System Chapter-6 Database Fundamentals : 6.1 - 6.26 Concept of Database Committing and revoking a Transaction using COMMIT and ROLLBACK, Grouping Records using GROUP BY, Group functions:MAX ( ), MIN ( ), AVG ( ), SUM ( ), COUNT ( ), COUNT (*), DISTINCT clause with COUNT; Null Values Displaying Data from Multiple Tables Cartesian product, Union, concept of Foreign Key, Equi-Join Chapter - 7 Introduction to MySQL : 7.1 - 7.38 Working with NULL values, ORDER BY clause Sorting by Column Alias Name, sorting of multiple columns Manipulating data of a table/relation UPDATE command to change existing data of a table, DELETE command for removing rows from a table ALTER Table for adding new columns / deleting existing columns DROP Table for deleting a table String functions:- ASCII( ), CHAR( ), CONCAT( ), INSTR( ), LCASE( ), UCASE( ), LENGTH( ), LTRIM( ), MID( ), RIGHT( ), RTRIM( ), TRIM( ), SUBSTR( ); Mathematical functions: POWER ( ), ROUND ( ), TRUNCATE ( ); Date & Time functions: CURDATE ( ), MONTH ( ), DAYOFMONTH ( ), DAYOFWEEK ( ), DAYOFYEAR ( ), NOW ( ), SYSDATE ( ) Unit 4: IT Applications Chapter - 8 e-Business : 8.1 - 8.24 e-Commerce, e-Business web sites & their salient features, Societal impact & challenges of e-Business Chapter - 9 Front-end Interface : 9.1 - 9.36 Content and features; Text Box, Radio Button, Checkbox, List, etc.) Validation and Display. Back-end Database: Exploring the requirement of tables and its essential attributes. Development of Database: Demonstration and development of Front-end interface and Back-end Database for e-Governance applications. Appendix Digital Transaction in India 1 - 18 n n n NETWORKING CHAPTER - 1 Computer networking CHAPTER - 2 Internet and its applications CHAPTER - 3 Network security on Internet PROGRAMMING CHAPTER - 4 Programming fundamentals CHAPTER - 5 HTML based web pages covering basic tags RELATIONAL DATABASE MANAGEMENT SYSTEM CHAPTER - 6 Database fundamentals CHAPTER - 7 Introduction to MySQL IT APPLICATIONS CHAPTER - 8 e-Business CHAPTER - 9 Front-end interface APPENDIX Digital transaction in India UNIT - 1 NETWORKING CHAPTER - 1 COMPUTER NETWORKING In our daily life, we have been communicating with our parents, teachers and friends through mother tongue or any other dialect. This communication takes place either directly or through telephones or via Internet by using computers (a desktop or a laptop or a smart phone)! The use of computer does not stop here. We use Bank ATMs for monetary transactions; take a print-out from a printer attached to some other computer by typing appropriate command from our smart phones, purchase railway tickets from the comfort of our home computer, etc. How the information that we feed gets transferred to various other devices (like printers, servers, speakers, etc.) and we also get return information in most of the cases? Machines do not have mouth or ear for communication! It happens through a process called, Computer Networking. A computer network is a collection of interconnected computers and other hardware devices which are linked together through communication channels to facilitate communication and resource-sharing among a wide range of users. Advantages of using a Network : There are distinct advantages of using networked computers over stand alone computers. Network increases efficiency, optimizes utility and enhances overall applicability of the available resources (man & machine) in large Government or Private Organizations. Current networking software provides the following advantages. 1.2 Information Technology y Class-XII Program Security & Easy Maintenance : l Store copies of programs in locked, read-only spaces on the server. l Protect program files from unauthorized copying. l Prevent tampering with programs. l Well-planned networking serves the needs of an organization for several years. More Secure Database & Personal Work Files : l Users can save copies of their personal work in multiple computers of a network for future safety. Information do not get lost, if a single computer developes any fault. l Password protection ensures inadvertent or malicious copying and/ or deletion of files. l A given database in a computer of larger memory(called as Server) can be shared by many stakeholders of a network. l Boot disks may be needed to start up workstations. But in a network remote booting removes the need for boot disks. Collaboration of Users by File Sharing : l Users can share data and program files on a network. l A network provides publicly accessible storage to keep assignments, tests, results, clipart, and other files. l A database can be populated / updated by more than one user in a network through active permission. l Facilitate communication via email, video conferencing, instant messaging, etc. Resource Sharing : l Users in a network can share different peripheral devices, like Printers, DVD drives, Scanners, Digital Projectors, etc. which reduces the cost of installation and maintenance substantially. It cost. Share the cost of printers among all users. Networking y Computer Networking 1.3 l Users can print their documents in a common printer instead of using individual devices. Further, a user can access different types of printers connected to a network! l Software resources like Application Softwares, Anti-Virus tools etc. can also be shared on computer networks. l Network modems can access outside resources. A computer network involves different types of hardware as well as software components. The hardware devices include- (a) Computers (desktop, laptop, workstations, smart phones, etc.). (b) Peripheral devices (printers, scanners, projectors, etc.). (c) Transmission media (wired and wireless media). (d) Networking devices (hub, switch, router, modem, etc.). [Computers and other peripheral devices connected to a network arecalled as Nodes] The software components include, (a) The rules of communication (Protocols) between the systems connected to a network, (b) Translation of software formats used in different networks through gateways. In addition to the hardware and software components, we need to understand the network architecture, which defines a logical manner in which the computers in a network are connected. It is also called as network topology. Different types of Network Topologies are, (a) Point to Point topology (b) Bus topology (c) Star topology (d) Ring topology (e) Tree topology Further the computer networks can be characterized by their size as well as their purpose. The size of a network can be expressed by the geographic area 1.4 Information Technology y Class-XII they occupy and the number of computers that are part of the network. Networks can cover anything from a handful of devices within a single room to millions of devices spread across the entire globe. Some of the different networks based on size are: (a) Personal area network, or PAN (b) Local area network, or LAN (c) Metropolitan area network, or MAN (d) Wide area network, or WAN In terms of purpose, many networks can be considered general purpose, which means they are used for everything from sending files to a printer to accessing the Internet. Some types of networks, however, serve a very particular purpose. Some of the different networks based on their main purpose are: (a) Storage Area Network, or SAN (b) Enterprise Private Network, or EPN (c) Virtual Private Network, or VPN Data Communication in networks: The idea of different types of Computer systems and peripheral devices has already been outlined in the 1st part of this book. Let’s begin from the idea of communication of electromagnetic signals between different devices attached to a computer network. The signals, which are being used in communication, are of two types; analog and digital. In analog type transmission the signal voltage varies sinusoidal with time. It is transmitted through telephone lines. Networking y Computer Networking 1.5 In digital type transmission the signal voltage is transmitted as voltages pulses of fixed amplitude as shown in the following figure. Transmission mode: To-day’s computers generate data in digital form, which are transmitted in between devices in binary format. Further, the transmissions of binary data across the links are carried either in parallel mode or in serial mode. In parallel mode, group of bits (byte) are sent from one device to another with each clock pulse where as in serial mode one bit is sent with each clock pulse. The parallel mode is fast but expensive, whereas the later is slow but cost effective. Parallel mode of transmission Serial mode of transmission To-day’s computers generate data in digital form, which are transmitted in between devices in binary format. Further, the transmissions of binary data across the links are carried either in parallel mode or in serial mode. In parallel mode, group of bits (byte) are sent from one device to another with each clock pulse where as in serial mode one bit is sent with each clock pulse. The parallel mode is fast but expensive, whereas the later is slow but cost effective. Apart from these two types of transmission, the direction of signal flow between two linked devices are basically of three types: Simplex, Half-Duplex, and Full-Duplex. 1.6 Information Technology y Class-XII Simplex mode: In this mode data travels in one direction i.e. communication is unidirectional. We cannot send a message back to the sender. Unidirectional communication is done in simplex systems, like: loudspeaker, television broadcasting, television and remote, keyboard and monitor etc. Half-Duplex mode: In this mode data travels in both directions but one at a time; that is when the sender is sending the data then at that time we can’t send the sender our message. The data is sent in one direction. Example of half duplex is a walkie- talkie in which message is sent are sent in both the directions, but one at a time. Full-Duplex mode: In this mode data can be sent in both directions simultaneously. Telephone Network in which there is communication between two persons by a telephone line, through which both can talk and listen at the same time is an example of Full Duplex transmission.. Transmission media: In a computer network, computers have to exchange information (data) among themselves. The information being in form of electromagnetic signals can travel through vacuum, air or other transmission media from one point to another (from source to receiver) in a network. A transmission medium can be wired (guided) or wireless (unguided). Guided Media: Depending upon their construction type, wired media can be classified in to three categories: (1) Twisted Pair cables (2) Co-axial cables (3) Optic Fiber cables Twisted Pair Cables / Ethernet Cables : Invented almost a century ago by Alexander Graham Bell, this is a pair of insulated copper wires twisted over each other in a spiral pattern. The twisted cabling design helps to reduce noise from outside sources and crosstalk on multi-pair cables, making Networking y Computer Networking 1.7 it suitable for use in the field of telecommunication for a long time Each cable consists of one or more twisted pairs and wrapped in a protective sheath. Each pair consists of a single communication link, with one conductor serving as the forward circuit and the other as the return circuit. Twisted Pair cables used in small computer networks (ethernet) contains four twisted pairs and sometimes called as Ethernet cables. These pairs are colour coded and is used to connect to a computer through RJ-45 connectors. Two types of ethernet cables are used to connect devices to hubs and switches in a network: crossover cables and straight-through cables. The difference between the two types is that in a crossover cable, two of the wires are crossed; in a straight-through cable, all the wires run straight through. Specifically, in a crossover cable, Wires 1 and 3 and Wires 2 and 6 are crossed: Wire 1 at one end becomes Wire 3 at the other end, Wire 2 at one end becomes Wire 6 at the other end, and vice versa in both cases. Computer in a network is connected to a Hub through a straight-through cable; whereas a crossover cable directly connects two Ethernet network devices (PCs) to each other. Ethernet crossover cables support temporary host-to-host networking in situations where an intermediate device like a network router is not present. Twisted Pair Cables are of two types: Unshielded Twisted Pair (UTP) and Shielded Twisted Pair (STP); individual pairs are not shielded within the cable in case of UTP; STP adds a conductive layer (typically metal foil) surrounding either each pair or the entire cable. This shielding helps reduce 1.8 Information Technology y Class-XII interference from electrical sources outside the cable. These cables are low cost and being used to set up small networks. A cable can carry data up to a length of 100m. Comparative characteristics are given in Table-1. Co-axial Cables : This cable has an inner conductor (a copper wire) surrounded by a woven braided metal shield or foil working as the outer conductor; both the conductors share a common central axis, hence the term “co-axial”. The central conductor is electrically insulated from the outer conductor by an insulating foam material. The outer conductor not only carries electrical signal in combination with the inner one, but also shields any kind of electromagnetic noise during transmission. Finally, a plastic jacket (PVC sheath) protects the whole cable. These cables are used for Ethernet connections as well as for cable television transmission. There are two types of Coaxial cables: Baseband and Broadband cables. Baseband cables (75W) are used for digital transmission (mostly used for LAN). Baseband transmits a single signal at a time with very high speed. The major drawback is that it needs amplification after every 1000 feet. Networking y Computer Networking 1.9 Broadband cables (50W) are used for analog transmission on standard cable television. It transmits several simultaneous signal using different frequencies. Advantages: l Bandwidth is high l Used in long distance telephone lines. l Transmits digital signals at a very high rate of 10Mbps. l Much higher noise immunity l Data transmission without distortion. l The can span to longer distance at higher speeds as they have better shielding when compared to twisted pair cable Disadvantages: l Single cable failure can fail the entire network. l Difficult to install and expensive when compared with twisted pair. l If the shield is imperfect, it can lead to grounded loop. Optic-fibre Cable : An optical fibre is a flexible, thin, transparent strand made up of high quality glass or plastic, slightly thicker than a human hair. It transmits light pulses by the principle of total internal reflection, which ensures minimum loss and long distance transmission. Each pulse of light represents a ‘bit’ of data. These fibres are arranged in bundles of hundreds and thousands to form a cable, which is protected by an outer jacket. 1.10 Information Technology y Class-XII An optic fiber cable has following parts: Core - It is the thin glass /plastic rod at the center through which the light travels Cladding - It is the outer optical material (of lower refractive index) surrounding the core that reflects the light back into the core Buffer coating - It is the plastic coating that protects the cable from damage and moisture Characteristics: l It can carry data over a long distance without any intermediate amplification. l It is not affected by any external electromagnetic fields l The joining of two optical fibres is a complex job, which needs skilled persons to install these cables. l It is the most expensive and most efficient cable available for computer networks. Both twisted pair and co-axial cables can support network speeds in megabit and gigabit ranges. Both are susceptible in varying degrees to signal interference, as well as signal leakage. (Signal interference occurs when external signals interfere with transmission inside the cable, and signal leakage means that signals inside the cable leak out and become a source of interference to other devices.) Coaxial cable, being of a standard design, varies little in its susceptibility to interference. From the distance point of view, if cable runs less than 100 metre, co-axial cable is probably the best option. Between 100metre and 1kilometre, UTP wire is often the best choice. More than a kilometer; go for optic fiber cable. Following table enlists some of the comparing parameters of these wired media. Networking y Computer Networking 1.11 Table-1 Parameters Ethernet Co-axial Optic-fiber Cables Cables Cables Signal form Electrical Electrical Optical External interference High Low Nil Attenuation High Low Very low Data transfer rate 10Mbps-10Gbps 100Mbps >100Gbps Cost of cables Cheapest Average Expensive Installation Easy Fairly easy Difficult Wireless Transmission: However, wireless medium is only the free space (air or vacuum). The transmission of electromagnetic signals in free space is accomplished through carrier waves, which are nothingbut electromagnetic waves; which travels with the speed of light and carries the original signal (data) through free space. Carrier waves are generally high frequency electromagnetic waves. Electromagnetic waves are categorized on the basis of their frequencies (or wavelengths); however all of them travel with the speed of light. When we arrange the electromagnetic waves according to ascending or descending order of their frequencies (or wavelengths), they are called as Electro-magnetic Spectrum. Frequencies of waves are measured in ‘hertz’ (Hz). As the frequencies of electromagnetic waves change, their properties also change. Based on their frequencies, electromagnetic waves are categorized as: Category Frequency range Radio waves 3´103 Hz to 3´109 Hz Microwaves 3´108 Hz to 3´1011 Hz Infrared radiation 3´1011 Hz to 4´1014 Hz Visible light 4.3´1014 Hz to 7.5´1014 Hz Ultraviolet radiation more than 1014 Hz X-rays more than 1015 Hz Gamma rays more than 1017 Hz [kilo hertz = kHz = 103 Hz; giga hertz=GHz = 109 Hz] 1.12 Information Technology y Class-XII Out of these radiations, Radio waves, Micro waves and Infra-red waves are used for wireless transmission. Radio wave transmission: Radio waves having a frequency range of 3 kHz to 3GHz are used for communication over distances ranging from a few meters (in walkie-talkies) up to few kilometers. These waves are easy to generate, can travel long distances and can penetrate buildings easily. That’s why they are widely used for communication, both indoors and outdoors. Cordless phones, AM and FM radio broadcast, Garage door openers etc. are examples of radio wave transmission. Characteristics of Radio wave transmission : l These waves propagate uniformly in all directions. So the transmitting and receiving antennas do not need any alignment. l Less expensive as compared to wired media. l It offers ease of communication over difficult terrain l The transmission can be interfered by motors or other electrical equipments. l Permission from concerned authorities is required for use of radio wave transmission l Less secure mode of transmission Micro wave transmission: Microwaves having a frequency range of 0.3 GHz to 300 GHz, travel in straight lines and cannot penetrate any solid object. Therefore, for long distance microwave communication, high towers are built and microwave antennas are put on their tops. Distance between two microwave towers depends on many factors including frequency of the waves being used and heights of the towers. Networking y Computer Networking 1.13 These waves travel in straight lines and therefore the sending and receiving antennas have to be aligned with each other along the line of sight. Characteristics of Microwave transmission : l Quick installation l Less expensive than wired media l Offers ease of communication over difficult terrain l It requires line of sight transmission; so the transmitting and receiving antennas need to be properly aligned. Infrared wave transmission : Infrared waves have a frequency range of 300 GHz to 400000 GHz. This frequency range is just below the frequency of Red colour (430000 GHz) of the visible spectrum; hence the name ‘infra red’. These are used for short range wireless communications (approx. 5m) like, television remote-control devices, cordless mouse, and intrusion detectors, etc. These waves do not pass through solid objects. So, an infrared device in one room of a building does not interfere with a similar system in adjacent rooms. For example, a TV remote, in one room cannot control a television set in another room. Characteristics of Infrared wave transmission: l It is a line of sight transmission; therefore information passed to one device is not leaked to another device. l No government license is required for their use l It is a line of sight transmission, therefore at a time only two devices can communicate. l The waves do not cross any solid object in between l Performance drops with longer distances Bluetooth : This technology uses radio waves in the frequency range of 2.402 GHz to 2.480 GHz. It is used for short range communication (approx. 10m) in a variety of devices for wireless communication. Baby monitors, door openers, and cell phones are some of the devices that utilize Bluetooth communication. 1.14 Information Technology y Class-XII Characteristics of Bluetooth Transmission: l Line of sight between communicating devices is not required. (Think Why?) l Bluetooth can connect up to eight devices simultaneously. l Slow data transfer rate (up to 1Mbps). Satellite Link Satellite links are used for very long distance wireless communication which may range from intercity to intercontinental. Transmission from the earth to a satellite is known as uplink. Transmission from a satellite to the earth is known as downlink. There are multiple micro wave frequency bands which are used for satellites links. Frequency used for uplink varies from 1.6 GHz to 30.0 GHz and that for downlink varies from 1.5GHz to 20.0GHz. Downlink frequency is always lower than the uplink frequency. For example, the uplink frequency is 6.0GHz, and the corresponding downlink frequency is 4.0 GHz. A communications satellite is a relay station in orbit above the earth that receives, regenerates, and redirects signals carried on a specific frequency. The satellite system is very expensive but its area of coverage and other benefits compensate for the expenses. These satellites are artificial and move around the Earth in different types of orbits: - Networking y Computer Networking 1.15 (a) Geo-stationary Orbit (GEO) (b) Medium Earth Orbit (MEO) (c) Low-Earth Orbit (LEO) Satellites in geo-stationary orbit revolve round the Earth in West to East direction along the equatorial plane at a height of 35,838 km. This height ensures that the satellite takes exactly 24 hour to complete one revolution and appear stationary from any place on the surface of earth. These satellites are widely used as communication satellites, especially for transmission of television signal. Characteristics of Satellite link: l Because of the height, a satellite covers large area of earth l Because of larger height, geostationary satellite communication consumes more electrical power for transmission in comparison to medium and low earth orbit satellites. l A set of low earth orbit satellites are being used for the popular Global Positioning System. l Though expensive, it is commercially viable because of its long distance transmission. l Satellite communication very much requires legal permission. 1.16 Information Technology y Class-XII Network devices : Now we have discussed different types of transmission media for exchange of information (in form of electro-magnetic signal) between the Nodes (computers, printers, scanners, mobile phones, etc.) of a network. Next are the devices, which are responsible for creating a physical network of computers and other peripheral devices need to be elaborated upon. These are called as Network devices, which are meant to distribute and channelize the electric signals throughout the network. Following are the basic devices needed to create a computer network; 1. Network Interface Card 2. Hub 3. Switch 4. Repeater 5. Bridge 6. Router 7. Gateway Network Interface Card (NIC) A Network Interface Card is a hardware device which connects a computer with the network. They are installed on the motherboard of computers and are responsible for developing physical contact with network devices and other computers (nodes). Computers send or receive information (in form of electrical signals) from network devices via this card. Thus every node, which is to be connected to a network, must have an NIC installed on it. These cards also manage some data-conversion function. Now a day, the NICs are software configured as against the older versions requiring a driver to configure them. Hub A Hub is a network device that connects several nodes to form a network and redirects the received information to all the connected nodes in broadcast mode Networking y Computer Networking 1.17 (The method of sending data to all systems regardless of the intended recipient is referred to as broadcasting). Computers and other devices of a network are connected to the ports of a hub by twisted pair cables. Hubs are designed to take data from one connected device, transmit them to the other appended devices without altering any of the transmitted packets received. They act as pathways to direct electrical signals to travel along. They transmit the information to all the nodes of the network, regardless of the fact that, to which node / nodes it is destined. The device for which the information is intended accepts it and others reject it. This method of operation makes a hub an inefficient networking device. Due to the inefficiencies of the hub system and the constantly increasing demand for more bandwidth, hubs are slowly but surely being replaced with Switches; discussed in the next section. Most hubs are referred to as either active or passive. Active hubs regenerate a signal before forwarding it to all the ports on the device and require a power supply. Active hubs are also termed as ‘repeaters’. Small workgroup hubs normally use an external power adapter, but on larger units the power supply is built in. Passive hubs, which today are seen only on older networks, do not need power and they don’t regenerate the data signal. Switch A switch is an intelligent hub. Just as in hub, devices in switches are connected to them through twisted pair cabling. It has the same function as that of a hub: to connect multiple computers/devices in a network. But the difference between the two is in the way they re-transmit the received information. Unlike a hub, instead of broadcasting (sending to each device attached to it) the received information, a switch sends the information selectively only to those computers for which it is intended. It does so by having an in-built learning 1.18 Information Technology y Class-XII of the MAC address of the devices connected to it. Switches operate in full- duplex mode where devices can send and receive data from the switch at the simultaneously. The transmission speed in switches is higher than that of a hub transferring a 20Mbps connection into 30Mbps and a 200Mbps connection to become 300Mbps. All of these make a switch more efficient than a hub. Performance improvements are observed in networking with the extensive usage of switches in the modern days. Repeater When the data is transmitted over a network for long distances, the data signal gets weak after certain distance. This distance depends on the data transfer range of transmission channel being used and can be from a few meters to a few kilometers. If the signal becomes weak, it cannot reach its destination. Therefore, some device is required which can re-strengthen the data signal before it gets too weak. Repeater is such a device. A repeater regenerates the received signal and re-transmits it to its destination Bridges Bridges are networking devices that connect networks. Sometimes it is necessary to divide networks into subnets to reduce the amount of traffic on each larger subnet or for security reasons. Once divided, the bridge connects the two subnets and manages the traffic flow between them. Today, network switches have largely replaced bridges. A bridge functions by blocking or forwarding data, based on the destination MAC address written into each frame of data. If the bridge believes the destination address is on a network other than that from which the data was received, it can forward the data to the other networks to which it is connected. If the address is not on the other side of the bridge, the data is blocked from passing. Bridges “learn” the MAC addresses of devices on connected networks by “listening” to network traffic and recording the network from which the traffic originates. Networking y Computer Networking 1.19 Routers Routers are network devices which process logical addressing information in the Network header of a packet such as IP Addresses. Router is used to create larger complex networks by complex traffic routing. It has the ability to connect dissimilar LANs on the same protocol. It also has the ability to limit the flow of broadcasts. A router primarily comprises of a hardware device or a system of the computer which has more than one network interface and routing software. When a router receives the data, it determines the destination address by reading the header of the packet. Once the address is determined, it searches in its routing table to get know how to reach the destination and then forwards the packet to the higher hop on the route. The hop could be the final destination or another router. Gateway There are a large number of computer networks operating throughout the globe; ATM network of banks, computer network of big retail chains (like, BigBazar or Reliance Fresh) spread over a city, etc. These networks use different hardware and software. Many times these networks need to communicate with each other. For example, when you swipe your Bank Debit Card in a retail outlet’s PoS machine, the data exchange takes place between the particular bank network and the retail company’s network. Another example is the Internet, which contains a large number of different types of networks spread over the globe. Different networks are sometimes incompatible with each other. It is like a group of persons using different languages for conversation. When two or more networks using different hardware and software have to be connected, some device is needed which can translate one network’s language into the other’s. Here comes a ‘Gateway’. The term Gateway is applied to any device, system, or software application that can perform the function of translating data from one format to another. The key feature of a gateway is that it converts the format of the 1.20 Information Technology y Class-XII data, not the data itself. It understands the address architectures used in different networks and seamlessly translate between these address architectures. Network Topology Computers in a network have to be connected in some logical manner. The layout pattern of the interconnections between computers in a network is called network topology. It is just a virtual shape or structure of the network and sometimes referred to as ‘network architecture.’ Devices on the network are called as ‘nodes.’ Computers and peripheral devices are examples of common nodes. Network topology is illustrated by showing the nodes and their connections using cables. There are different types of network topologies, including Point-to-Point, Bus, Star, Ring, Mesh, Tree and Hybrid, etc. Point-to-Point Topology Point-to-point topology is the simplest of all the network topologies. The network consists of a direct link between two computers. This is faster and more reliable than other types of connections since there is a direct connection. The disadvantage is that it can only be used for small areas where computers are in close proximity. Bus Topology Bus topology uses one main cable to which all nodes are directly connected. The main cable acts as a backbone for the network. One of the computers in the network typically acts as the computer server. If any node has to send some information to any other node, it sends the signal to the backbone. The signal travels through the entire length of the backbone and is received by the node for which it is intended. A small device called terminator is attached at each end of the backbone. When the signal reaches the end of backbone, it is absorbed by the terminator and the backbone gets free to carry another signal. This prevents the reflection of signal back on the cable and hence eliminates the chances of signal interference. Networking y Computer Networking 1.21 Characteristics of Bus topology : l It is easy to install this network and connect different peripheral devices in it. l It requires less cable length and hence is cost effective. l Failure of a node does not affect the network. l In case of cable or terminator fault, the entire network breaks down. l It is very difficult to troubleshoot i.e difficult to diagnose the fault. l For these reasons, this type of topology is not used for large networks. l At a time only one node can transmit data. Star Topology In star topology, each computer is connected to a central hub using a point- to-point connection. The central hub can be a computer server that manages the network, or it can be a much simpler device that only makes the connections between computers over the network possible. 1.22 Information Technology y Class-XII Characteristics of Star topology l Star topology is more efficient than the Bus Topology. l It is easy to add new nodes to the network. l The network is robust in the sense that if one connection between a computer and the hub fails, the other connections remain intact. l If the central hub fails, however, the entire network goes down. l It requires more cable than bus topology and is, therefore, more expensive. Ring Topology In ring topology, the computers in the network are connected in a circular fashion, and the data travels in one direction. Each computer is directly connected to the next computer, forming a single pathway for signals through the network. Characteristics of Ring topology l This type of network is easy to install and manage. l If there’s a problem in the network, it is easy to pinpoint which connection is defective. l It is also good for handling high-volume traffic over long distances since every computer can act as a booster of the signal. l Adding computers to this type of network is more cumbersome, and if one single computer fails, the entire network goes down. Tree Topology Tree topology is a combination of bus and star topologies. It is used to combine multiple star topology networks. All the stars are connected together Networking y Computer Networking 1.23 like a bus. This bus-star hybrid approach supports future expandability of the network. Characteristics of Tree topology l It offers easy way of network expansion l Even if one network (star) fails, the other networks remain connected and working. Mesh Topology In mesh topology, every node has a direct point-to-point connection to every other node. Because all connections are direct, the network can handle very high-volume traffic. It is also robust because if one connection fails, the others remain intact. Security is also high since data travels along a dedicated connection. There are so many different types of computer networks in existence; it can be hard to understand the differences between them, particularly the ones with very similar-sounding names. In this section we discussed the structures and functions of some of the most popular computer networks. 1.24 Information Technology y Class-XII Types of Networks A computer network may span any amount of geographical area. It can be on a table, in a room, in a building, in a city, in a country, across continents or around the world. On the basis of area covered computer networks are classified as: l PAN - Personal Area Network l LAN - Local Area Network l MAN - Metropolitan Area Network l WAN -Wide Area Network Personal Area Network A personal area network, or PAN, is a computer network organized around an individual person within a single building. This could be inside a small office or residence. A typical PAN would include one or more computers, telephones, peripheral devices, video game consoles and other personal entertainment devices. If multiple individuals use the same network within a residence, the network is sometimes referred to as a home area network. In a very typical setup, a residence will have a single wired Internet connection connected to a modem. This modem then provides both wired and wireless connections for multiple devices. The network is typically managed from a single computer but can be accessed from any device. A PAN can be set up using guided media (USB cable) or unguided media (Bluetooth, Infrared). This type of network provides great flexibility. It allows you to: l Send a document to the printer in the office upstairs while you are sitting with your laptop. l Upload the photo from your cell phone to your desktop computer. l Transfer a file from your PC to an MP3 player l Watch movies from an online streaming service to your TV. Local Area Network A LAN is a network of computing/communicating devices in a room, building, or campus. It can cover an area of a few meters to a few kilometers radius. A networked office building, school, or home usually contains a single LAN, though sometimes one building can contain a few small LANs (Like some schools have independent LANs in each computer lab.). Occasionally a LAN Networking y Computer Networking 1.25 can span a group of nearby buildings. In addition to operating in a limited space, a LAN is owned, controlled, and managed by a single person or organization. A LAN can be set up using wired media (UTP cables, Co-axial cables etc.) or wireless media (Infrared, radio waves). If a LAN is entirely wireless; it is known as WLAN (wireless LAN). Metropolitan Area Network A metropolitan area network, or MAN, consists of a computer network across an entire city, college campus or small region. A MAN is larger than a LAN, which is typically limited to a single building or site. Depending on the configuration, this type of network can cover an area from several miles to tens of miles. A MAN is often used to connect several LANs together to form a bigger network. When this type of network is specifically designed for a college campus, it is sometimes referred to as a campus area network, or CAN. WAN (Wide Area Network) A WAN is a network of computing/communicating devices crossing the limits of a city, country, or continent. It can cover an area of over hundreds of kilometer radius. A network of ATMs, BANKs, National Government Offices, International Organizations’ Offices etc., spread over a country, continent, or covering many continents are examples of WANs. WANs usually contain a number of interconnected individual computers, LANs, MANs, and maybe other WANs. All types of communication media (guided and unguided) are used to set up a WAN. The best known example of a WAN is the internet. Following table summarizes the characteristics of PANs, LANs, MANs, and WANs. Parameter PAN LAN MAN WAN Area Covered Small A few meter A city and its Entire Area (up to a few km vicinity (up to country, to 10m (up to 10km 100km continent, or radius) radius) radius) globe (No upper limit) Error Rates Lowest Lowest Moderate Highest Transmission High High Speed Moderate Low speed Speed Speed speed Networking Negligible Inexpensive Moderately Expensive Cost expensive 1.26 Information Technology y Class-XII SUMMARY Ø Computer network is a collection of interconnected computers and other devices which are able to communicate with each other. Ø Communication Media are the links over which the data is sent from one node to another over a network. Ø Hardware devices used to form a network are: Cables, NIC, Hub, Switch, Repeater, and Gateway. Ø Repeaters are used to regenerate the signal which gets weakened during its transmission. Repeater are generally used to connect two networks which are more than 80 m apart. Ø Gateway is a device which connects two different types of networks. Ø On the basis of area covered by a network it is categorized as PAN, LAN, MAN, or WAN. Ø Physical arrangement of computers in a network is called network topology. Ø Basic network topologies are bus, star and tree. ––––––– Networking y Computer Networking 1.27 EXERCISE MULTIPLE CHOICE QUESTIONS : 1. Which of the following topologies is a combination of more than one topologies? a. Bus b. Tree c. Star d. None of these 2. Which of the following is used for wireless communication? a. Optical Fiber b. UTP cable c. Radio Waves d. Coaxial Cable 3. Which of the following is not a transmission medium? a. Telephone Network b. Coaxial Cable c. Modem d. Microwaves 4. IP addresses of two computers on a network: a. can be the same b. cannot be the same c. are not defined d. must match with a third computer 5. Bluetooth can be used for a. Long distance communication b. Short distance communication c. In mobile phones only d. None of the above 6. Micro waves are a. Unidirectional b. Omni directional c. Guided media d. Not used for communication. 7. A repeater a. Regenerates the received signal b. Destroys the received signal c. Can be used as a hub d. None of the above 8. Satellite links are generally used for a. PANs b. LANs c. MANs d. All of the above 1.28 Information Technology y Class-XII LONG ANSWER TYPE QUESTIONS : 1. What is a computer network? What are its advantages? 2. What is meant be communication channels? Give two examples of guided media and two examples of unguided media. 3. Why is a switch called an intelligent hub? 4. When is a repeater used in a computer network? 5. Diagrammatically show how you would connect 6 PCs, 1 server, 1 printer, and 2scanners in a. Star topology b. Bus topology 6. Two engineers in the same room have connected their Palm-tops using Bluetooth for working on a Group presentation. Out of the following, what kind of Network have they formed? LAN, MAN, PAN, WAN 7. Differentiate (with examples wherever possible) between: (a) LAN and MAN (b) MAN and WAN (c) Hub and Switch (d) Guided and Unguided media 8. Write one advantage of star topology over bus topology and one advantage of bus topology over star topology. n n n  CHAPTER - 2 INTERNET AND ITS APPLICATIONS Internet - an overview : Internet, the network of computers to share information amongst each other was first proposed by J C R Licklider of MIT (Massachusetts Institute of Technology) in 1962. His intention was to share millitary and scientific information between different organisations situated at different places in United States.During that period Leonard Kleinrock of University of California, Los Angeles developed the theory of packet switching, which eventually formed the backbone of today’s internet data transmission. The first ever network of computers was installed at National Research Laboratory, England in the year 1968. A year later, a more advanced network was established at Pentagon’s Advanced Research Project Agency (ARPA) connecting four high speed computers. This network was called as ARPAnet. By 1972, ARPAnet had 23 nodes, connecting different institutions of United States. In the same year, Raymond Samuel Tomlinson of United States incorporated the first e-mail program and picked @ symbol to link the user name and the address. The first ever international nodes of ARPAnet were set up in 1973 in England and Norway. A year later Bob Kahn and Vint Cerf put the foundation of Network Transfer protocol, which ultimately standardised as TCP/IP for ARPAnet in 1983. It assigns a number to each computer of a network, and called as IP (Internet Protocol) address. However, numeric addresses of different computers are difficult to remember. Therefore, a new technique called as Domain Name System was introduced in 1984. In this system each computer (host) of a network is given a human readable and easy to remember names called as domain names.The Domain Name Server (DNS) converts these names to corresponding numeric IP addresses. By 1990 ARPAnet ceased to exist, but its functions were continued. In 1991 WAIS (Wide Area Information Server) and Gopher were released, paving the way for modern Internet system. 2.2 Information Technology y Class-XII 1992 saw the release of WWW by CERN (European Organisation for Nuclear Research), a physics research institute in Switzerland. The brain child of the physicist Tim Berners Lee, WWW today forms the gateway to any internet transmission. He wrote the first WWW client and WWW server, and defined the standards like URL, HTML and HTTP. In 1993, the first internet browser “Mosaic” was released by Marc Andreessen and his team at National Centre for Supercomputing Applications. Later, he moved to Netscape Communication Corporation and invented the most successful graphical browser ‘Netscape Navigator’. This browser dominated the internet browsing until the Microsoft Inc introduced its “Internet Explorer” and integrated it in to its flagship Windows Operating System. Introduction to Internet: A global collection of individual networks, connected to each other by different networking devices and functions as a single large network is called an Internetwork of computers or Internet. It is a conglomeration of independent smaller networks and other connected machines spanning the entire globe. It is a window to global information super highway. In short, the internet is a worldwide network of networks. Internet Backbone and its features: An Internet backbone refers to one of the principal data routes between large, strategically interconnected networks and core routers on the Internet. It is a very high-speed data transmission line that provides networking facilities to relatively small but high-speed Internet Service Providers (ISP) all around the world. The first Internet backbone was named NSFNET. It was funded by the U.S. government and introduced by the National Science Foundation (NSF) in 1987. It was a T1 line that consisted of approximately 170 smaller networks operated at 1.544 Mbps. The backbone was a combination of fiber-optic trunk lines, each of which had several fiber-optic cables wired together to increase capacity. A backbone is a larger transmission line that carries data gathered from smaller lines that interconnect with it. Networking y Internet and its Applications 2.3 (1) At the local level, a backbone is a line or set of lines that local area networks(LAN) connect to for a wide area network(WAN) or within a LAN to span distances efficiently (for example, between buildings). (2) On the Internet or other WANs, a backbone is a set of paths that local or regional networks connect to, for long-distance interconnection. The connection points are known as network nodes or data switching exchanges (DSEs). Around the world, each country has at least one backbone network that operates at very high speed and carries bulk of the traffic. Other smaller networks connect to that backbone. Internet backbones are the largest data connections on the Internet. They require high-speed bandwidth connections and high- performance servers/routers. Backbone networks are primarily owned by commercial, educational, government and military entities because they provide a consistent way for Internet service providers (ISPs) to keep and maintain online information in a secure manner. For example, a local ISP may provide service to individual homes or business using bandwidth that it purchases from another company with a backbone network. Backbone networks are usually commercial, educational, or government owned. Some large companies that provide backbone connectivity include Verizon, British Telecom, AT&T, Sprint Nextel, Global Crossing, France Télécom, BSNL, Reliance Communications, Airtel, VSNL International, Idea, Ortel Communications, Tata Tele Services, etc. Today, these backbones are constructed of fiber optic cables. These links, called OC links (Optical Carrier), use frequency bands of electromagnetic waves (light) to transmit data to get rid of interference. OC connections use SONET (Synchronous Optical Network) technology, which is the industry standard for testing high-speed electrical signals. Features of an Internet backbone : (a) ISPs are either connected directly to their contingency backbones or to some larger ISP that is connected to its backbone. (b) The smaller networks are interlinked to support the backup that is required to keep the Internet services intact in case of failure. This is done through transit agreements and peering processes. 2.4 Information Technology y Class-XII (c) The transit agreement is a monetary contract between several larger and smaller ISPs. It is initiated to share traffic loads or to handle data traffic in case of a partial failure of some networks. In peering, several ISPs also share features and traffic burden. Different Network Technologies can be connected to create an Internetwork as described below. Token Ring network is a local area network in which all computers are connected in a ring or star topology and a bit- or token-passing scheme is used in order to prevent the collision of data between two computers that want to send messages at the same time. The Token Ring protocol is the second most widely-used protocol on local area networks after Ethernet. Ethernet is the most widely-installed local area network technology. Specified in a standard, IEEE(Institute of Electrical and Electronics Engineers) 802.3, Ethernet was originally developed by Xerox from an earlier specification called Alohanet (for the Palo Alto Research Center Aloha network) and then developed further by Xerox, DEC, and Intel. An Ethernet LAN typically uses coaxial cable or special grades of twisted pair wires. Ethernet is also used in wireless LANs. The most commonly installed Ethernet systems are called 10BASE-T and provide transmission speeds up to 10 Mbps. Devices are connected to the cable and compete for access using a Carrier Sense Multiple Access with Collision Detection (CSMA/CD ) protocol. Fiber Distributed Data Interface (FDDI) provides a standard for data transmission in a LAN that can extend in range up to 200 kilometer. Although FDDI protocol is a token ring network, it does not use the IEEE 802.5 token ring protocol as its basis; instead, its protocol is derived from the IEEE 802.4 token bus timed token protocol. In addition to covering large geographical areas, FDDI local area networks can support thousands of users in Metropolitan Area Network (MAN). A FDDI network contains two token rings, one for possible backup in case the primary ring fails. The primary ring offers up to 100 Mbps capacity. When a network has no requirement for the secondary ring to do backup, it can also carry data, extending capacity to 200 Mbps. Features of Internet : Geographic Distribution : The geographic distribution of the Internet continues to spread, around the world and even beyond. Networking y Internet and its Applications 2.5 A key attribute of the Internet is that once you have connected to any part of it, you can communicate with all of it. All of the Internet’s technologies web, newsgroups, email, mailing lists, IRC, MUD’s enable geographically distributed groups of people to communicate who otherwise couldn’t do so. Largely because the basic architecture of the Internet is open fundamentally designed to connect new networks this powerful communication medium has spread rapidly to interconnect our world and turned it into a true multi-way electronic global village. Robust Architecture : The Internet is the most robust communications network ever designed. It is able to adapt itself almost instantaneously to the outages of individual sections. The Internet has no irreplaceable central control, administration, or authority. It can’t be bought, hijacked, or monopolized. The loss of individual computers and networks does not affect its overall reliability. The Internet perfectly realizes its original intent, it is actively robust, and cannot be completely deactivated without bringing down every single connection. Near Light Speed : Digital information such as Internet packets travel at 2/3 of the speed of light on copper wire and on fiber optic cables. Since light speed is about 300,000 kilometers a second, this means digital communications travel at about 200,000 kilometers a second. At this speed and neglecting switching delays, two computers have to be more than ten thousand kilometers apart, or almost half way around the world, before they experience a tenth of a second in communications delay. With fixed near-optimal transmission speed, there are only two ways to make Internet networks faster, increase the number of bits that are traveling at once down the connection, or increase the speed at which you switch them from one connection to another at the junction points. Universal Access : The Internet provides universal access, giving the same powerful capabilities to everyone who has access to the network no matter where they are. The Internet is based on a common standard, the TCP/IP network protocol, which provides all computers with access to the network with the same technical interface and capabilities. This common foundation makes all of the internet technologies equally available to anyone connected to the Internet. This architecture gives everyone the ability to make information like text, audio, and video accessible to a world wide audience at an extremely low cost, 2.6 Information Technology y Class-XII since web site storage space and lots of bandwidth can be rented from web hosting providers for low fees. Because the Internet has a “many-to-many” architecture, with everyone having the same capabilities as anyone else, it allows anyone to become a global publisher. Internet Access : Internet access is the process that enables individuals and organisations to connect to the Internet using computer terminals, computers, mobile devices, sometimes via computer networks. Once connected to the Internet, users can access Internet services, such as email and the World Wide Web. Internet service providers (ISPs) offer Internet access through various technologies that offer a wide range of data transfer speeds. Technology is developing rapidly and methods for connecting to the Internet change almost daily. The following types of connections are most commonly available. (i) Gateway Access (ii) Dial-up Connection (iii) Direct / Leased Connection (iv) DSL (v) Cable Modem Connection (vi) VSAT (vii) Wireless Internet Access Gateway Access : Gateway Access is also known as Level-One connection. It is the access to the Internet from a network, which is not on the Internet. The gateway allows the two different types of networks to “talk” to each other. But the users of the Gateway Internet have limited access to the Internet. They might not be able to use all the tools available on Internet. The local Internet Service Provider (ISP) normally defines this limitation. Good example of network with Level One connectivity within India is that of VSNL (Videsh Sanchar Nigam Limited). All access to Internet from India is through VSNL gateway. Networking y Internet and its Applications 2.7 Dial-up Connection : ‘Dial-up’ connection is also known as Level Two connection. This provides connection to Internet through a dial-up terminal connection. Data is transmitted through an analog phone connection. You connect to the Internet by using your phone line to dial into an ISP’s (Internet Service Providers) line. This connection allows only one computer at a time, per line, to be connected. When the line is connected to the Internet, voice communication would not be available over it. 56K modem access is now widely available and supported by most ISPs. It allows user to surf the Web at 56 Kbps with graphics. So this type of connection is also known as ‘Remote Modem Access’ connection. This type of connection can further be divided into three categories. (a) Shell Connection: In this type of Internet Connection, the user will get only textual matter of a Web Page. This connection does not support Graphics display. Shell Accounts were the only type of Internet access available for many years before the Internet entered in to the world of graphics and became more users friendly. (b) TCP/IP Connection: Today’s graphical World Wide Web browsers provide easier access with multimedia sound and pictures. The major difference between Shell and TCP/IP account is that, Shell account can only display text and does not support graphics display, whereas TCP/IP can display both. (c) ISDN: ISDN (Integrated Services Digital Network) offers Internet connectivity at speeds of up to 128 Kbps through the use of digital phone lines. ISDN is a dial-up service that has been provided by telephone companies for many years. To access any of these dial-up accounts you need the followings; Computer Modem Telephone Connection Shell or TCP/IP/ISDN account from the ISP Internet client software such as Internet browser 2.8 Information Technology y Class-XII Direct / Leased Connection : Leased connection is also known as direct Internet access or Level Three connection. It is the secure, dedicated and most expensive, level of Internet connection. With leased connection, your computer is dedicatedly and directly connected to the Internet using high-speed transmission lines. It is on-line 24´7 (twenty-four hours a day, seven days a week) basis. Direct access can be availed in one of the following two ways: (1) Dialup IP direct access: Dialup IP direct access uses a modem and telephone line. You also need special software to enable internet connectivity conforming to Serial Line Internet Protocol or Point-to- Point Protocol (PPP).These internet standards provide direct connection through telephone lines. The use of dialup IP is growing rapidly. (2) The second way of obtaining direct access is to connect your computer to a local area network (LAN) that has internet connectivity. Most people in universities and corporations use this method. DSL connection : Digital Subscriber Line (DSL) is a family of technologies that provides digital data transmission over the wires of a local telephone network. In telecommunications marketing, the term DSL is widely understood to mean Asymmetric Digital Subscriber Line (ADSL), the most commonly installed DSL technology. This service delivers voice and data simultaneously over the the same telephone line. This is possible because DSL uses higher frequency bands for data & lower band for voice; separate them by filtering. This enables simultaneous use of the telephone and data. The data bit rate of consumer DSL services typically ranges from 256 kbit/s to 40 Mbit/s in the direction to the customer (downstream). In ADSL, the data throughput in the upstream direction, (the direction to the service provider) is lower, hence the designation of asymmetric service. In Symmetric Digital Subscriber Line (SDSL) services, the downstream and upstream data rates are equal. Advantages : (1) Security: Unlike cable modems, each subscriber can be configured so that it will not be on the same network. In some cable modem networks, other computers on the cable modem network are left Networking y Internet and its Applications 2.9 visibly vulnerable and are easily susceptible to break in as well as data destruction. (2) Integration: DSL will easily interface with ATM and WAN technology. (3) High bandwidth (4) Cheap line charges from the phone company. (5) Good for “bursty” traffic patterns Disadvantages : (1) No proper standardization: A person moving from one area to another might find that their DSL modem is just another paperweight. Customers may have to buy new equipment to simply change ISPs. (2) Expensive: Installation costs, including the modem is high. (3) Depends on distance: The farther you live from the DSLAM (DSL Access Multiplexer), the lower the data rate. Cable Modem Connection : A cable modem is a type of Network Bridge and modem that provides bi- directional data communication via radio frequency channels on a HFC(hybrid fibre coax) and RFoG (radio frequency over glass) infrastructure. Cable modems are primarily used to deliver broadband Internet access in the form of cable Internet, taking advantage of the high bandwidth of a HFC and RFoG network. The Cable TV Company (e.g. Ortel Communication in Odisha) runs a coaxial cable into the building to deliver their Internet service. Although fed from the same coax that provides cable TV service, most companies place a splitter outside of the building and runs two cables in, rather than using a splitter at the set-top box. The coax terminates at the cable modem. In most circumstances, the cable modem attaches directly to a user’s computer. If a LAN is present on the premises, some sort of router can be connected to the cable modem. Cable connections provide high speed data transfer downstream (from the Internet to your computer), but are slower when sending data from your computer to the network. Additionally, transfer rates are affected by the number of subscribers online simultaneously. All connections originate on one line per street, so signals degrade as more subscribers come online. Cable connections 2.10 Information Technology y Class-XII can be used by individual subscribers to connect one computer to one line, or can be used to connect multiple computers in a building to the Internet. Some of the features of Cable Internet Connections are outlined below: (1) Always Connected: A cable modem connection is always connected to the Internet. This is advantageous because you do not have to wait for your computer to “log on” to the Internet; however, this also has the disadvantage of making your computer more vulnerable to hackers. Broadband Cable modems transmit and receive data as digital packets, meaning they provide high-speed Internet access. This makes cable modem connections much faster than traditional dial-up connections. (2) Bandwidth: Cable modems have the potential to receive data from their cable provider at speeds greater than 30 megabits per second. Cable lines are shared by all of the cable modem users in a given area; thus, the connection speed varies depending upon the number of other people using the Internet and the amount of data they are receiving or transmitting. (3) File Transfer Capabilities: Downloads may be faster, but uploads are typically slower. Since the same lines are used to transmit data to and from the modem, priority is often given to data traveling in one direction. (4) Signal Integrity: Cable Internet can be transmitted long distances with little signal degradation. This means the quality of the Internet signal is not significantly decreased by the distance of the modem from the cable provider. (5) Routing: Cable routers allow multiple computers to be hooked up to one cable modem, allowing several devices to be directly connected through a single modem. Wireless routers can also be attached to your cable modem. VSAT (Very Small Aperture Terminal) : VSAT is an earthbound station used in satellite communications of data, voice and video signals, excluding broadcast television. A VSAT consists of two parts, a transceiver that is placed outdoors in direct line of sight to the satellite and a device that is placed indoors to interface the transceiver with the end Networking y Internet and its Applications 2.11 user’s communications device, such as a PC. The transceiver receives or sends a signal to a satellite transponder in the sky. The satellite sends and receives signals from a ground station computer that acts as a hub for the system. Each end user is interconnected with the hub station via the satellite, forming a star topology. The hub controls the entire operation of the network. For one end user to communicate with another, each transmission has to first go to the hub station that then retransmits it via the satellite to the other end user’s VSAT. Advantages : Satellite communication systems have some advantages that can be exploited for the provision of connectivity. These are: Ø Costs Insensitive to Distance Ø Single Platform service delivery (one-stop-shop) Ø Flexibility Ø Upgradeable Ø Low incremental costs per unit Disadvantages : However like all systems there are disadvantages also. Some of these are Ø High start-up costs (hubs and basic elements must be in place before the services can be provided) Ø Higher than normal risk profiles Ø Severe regulatory restrictions imposed by countries that prevent VSAT networks and solutions from reaching critical mass and therefore profitability Ø Some service quality limitations such the high signal delays (latency) Ø Natural availability limits that cannot be mitigated against Ø Lack of skills required in the developing world to design, install and maintain satellite communication systems adequately Broadband Internet access, often shortened to just broadband, is simply defined as “Internet access that is always on and faster than the traditional dial-up access and so covers a wide range of technologies. Broadband connections are typically made using a computer’s built in Ethernet networking capabilities, or by using an NIC expansion card. 2.12 Information Technology y Class-XII Most broadband services provide a continuous “always on” connection; there is no dial-in process required, and it does not interfere with voice use of phone lines. Broadband provides improved access to Internet services such as: (a) Faster world wide web browsing (b) Faster downloading of documents, photographs, videos, and other large files (c) Telephony, radio, television, and videoconferencing (d) Virtual private networks and remote system administration (e) Online gaming, especially massively multiplayer online role-playing games which are interaction-intensive The broadband technologies in widest use are ADSL and Cable Internet access. Newer technologies include VDSL and optical fibre extended closer to the subscriber in both telephone and cable plants. Fibre-optic communication has played a crucial role in enabling broadband internet access by making transmission of information at very high data rates over longer distances much more cost-effective than copper wire technology. Newer technologies being deployed for fixed (stationary) and mobile broadband access include WiMAX, LTE, and fixed wireless, e.g., Motorola Canopy. Starting in roughly 2006, mobile broadband access is increasingly available at the consumer level using “3G” and “4G” technologies such as HSPA, EV- DO, HSPA+, and LTE. Wireless Internet Access: wireless is a high-speed technology that transmits data over radio waves. Wireless transmission can be used to provide connectivity from an ISP to an entire building; however, service will be dependent on the existence of a clear line of sight between the ISP (internet service provider) and the building. Within a building, a wireless local area network (LAN) can connect multiple computers to each other and to the Internet. Internet access is also being delivered through mobile phone towers to computers, mobile phones and other digital devices using portable modems. Some mobile services allow more than one device to be connected to the Internet using a single cellular connection using a process called tethering. The modem may be built into laptop computers, tablets, mobile phones, and other devices, Networking y Internet and its Applications 2.13 added to some devices using PC cards, USB modems, and USB sticks or dongles, or separate wireless modems can be used. In areas not served by ADSL or cable, some community organizations and local governments are installing Wi-Fi networks. Wireless and Satellite Internet are often used in rural, undeveloped, or other hard to serve areas where wired Internet is not readily available. Role of Internet Service Provider (ISP) : The internet started off as a closed network between government research laboratories and relevant parts of universities. It got popular and the universities and colleges started giving more of their members’ access to it. As a result, commercial Internet Service Providers emerged to provide access for mainly those who missed their university accounts. It is claimed that ‘The World’ was the 1st commercial ISP in 1989. Telerama founded in 1991 claims to be the world’s 3rd Internet Service Provider. ISPs employ a range of technologies to enable consumers to connect to their network. For “home users”, the most popular options include dial-up, DSL (typically ADSL), Broadband wireless access, Cable modem, and ISDN. For customers who have more demanding requirements, such as medium-to-large businesses, or other ISPs, DSL, Ethernet, Metro Ethernet, Gigabit Ethernet, Frame Relay, ISDN, ATM, satellite Internet access and SONET are more likely. With the increasing popularity of downloading music and online video and the general demand for faster page loads, higher bandwidth connections are becoming more popular. Just as their customers pay them for Internet access, ISPs themselves pay upstream ISPs for Internet access. In the simplest case, a single connection is established to an upstream ISP using one of the technologies described above, and the ISP uses this connection to send or receive any data to or from parts of the Internet beyond its own network, in turn, the upstream ISP uses its own upstream connection, or connections to its other customers (usually other ISPs) to allow the data to travel from source to destination. Internet protocols : Internet Protocol (IP) is a set of rules that governs the exchange (transmitting and receiving) of data or procedures between electronic devices (such as computers) connected across a single network or a series of 2.14 Information Technology y Class-XII interconnected networks. Protocols generally includes rules of how and when a device can send or receive the data, how is the sent data packaged, and how it reaches its destination. Messages are exchanged as datagram, also known as data packets or just packets. Several protocols are used on the Internet, including Transmission Control Protocol / Internet Protocol (TCP / IP), Electronic Mail (e-mail), File Transfer Protocol (FTP), HTTP (World Wide Web), News (or Usenet), Wais, Gopher and Telnet. Each of these has its own standard and usage. TCP / IP It is actually a suite, or family, of protocols that govern the way data is transmitted across networks. TCP / IP protocols work together to break the data into small pieces that can be efficiently handled by the network, communicate the destination of the data to the network, verify the receipt of the data on the other end of the transmission, and reconstruct the data in its original form. Electronic Mail Included in the email protocol are three distinct protocols. SMTP (Simple Mail Transfer Protocol), IMAP (Internet Message Access Protocol) and POP3 (Post Office Protocol 3). SMTP is a protocol used for sending mail, while IMAP and POP3 are used for receiving. Almost all Internet service providers support all three protocols. However the most popular setup for most providers is to use SMTP for sending mail while using POP3 for receiving. File Transfer Protocol File Transfer Protocol, or FTP, is a means of transferring a file from one computer to another. FTP is commonly used for uploading a web page to a web server so that it may be seen on the World Wide Web. A special program, called a client, is usually needed to use FTP. HTTP (World Wide Web) Hypertext Transfer Protocol, or HTTP, is the protocol used by web server to allow web pages to be shown in a web browser. If you look up into the address bar of your web browser, the place where you type in the address that you want to visit, it has the prefix “http://” in front of the address. Because most web Networking y Internet and its Applications 2.15 browsers are capable of FTP as well as viewing web pages, the http tells the browser what kind of information to expect. News (or Usenet) Network News Transfer Protocol (NNTP) is used for serving Usenet posts Usenet is similar to the forums that many web sites have. Usenet has forums that are dedicated to specific companies as well as forums that have a wide range of topics. Usenet is divided into several areas. Some of the forums that are included in Usenet are: comp. for discussion of computer-related topics, sci. for discussion of scientific subjects, rec. for discussion of recreational activities (e.g. games and hobbies) and talk. Gopher Another tool of the Internet is Gopher, a menu-based program that enables you to browse for information without knowing where the material is located. It lets you search a list of resources and then sends the material to you. Telnet Telnet lets you log in to a remote computer just as you would if you were there. So any commands that you would be able to run from the remote computer if you were sitting in front of it, you would be able to run from the computer you logged in from. Wais It is an Internet search tool that has the capability of searching many databases at one time. The databases to be searched can be determined by the user. When WAIS completes a search, it is actually searching an index of the database. A WAIS database index is created by a person. WAIS retrieves all items from the chosen databases that contain no of the words in the search phrase, provided that the words in the search phrase appear in the indexes of the selected databases. A relevancy ranking is assigned to each retrieved item to help the user determine which items may be most useful. WAIS can be accessed via Telnet, Gopher or a WAIS client program, and increasingly WAIS indexed databases are accessible through the World Wide Web. Network Identifiers (IP address) Once a network has been set up, the nodes can communicate among themselves. But for proper communication, the nodes should be uniquely identifiable. If a node A sends some information for node B on a network, then 2.16 Information Technology y Class-XII it is mandatory that nodes A and B are uniquely identifiable on the network. It is achieved in the following manner. Each NIC (network interface card, installed in a node) has a unique address assigned to it by its manufacturer. This address is known as the MAC (Media Access Control) address of the card. It means that a machine with an NIC can be identified uniquely through its NIC’s MAC address. MAC address of an NIC is permanent and never changes. This addresses is a 12-digit hexadecimal (or 48 bit) number. By convention, MAC addresses are usually written in one of the following two formats: MM:MM:MM:SS: SS: SS MM-MM-MM-SS-SS-SS The first half (MM:MM:MM) of a MAC address contains the ID number of the adapter manufacturer. The second half (SS: SS: SS) of a MAC address represents the serial number assigned to the adapter (NIC) by its manufacturer. For example, in the following MAC address, 00:A0:C9: 14:C8:35 The prefix 00:A0:C9 indicates that the manufacturer is Intel Corporation & the last three numbers 14:C8:35 are given by the manufacturer to this NIC. IP Address Every machine in a network has another unique identifying number, called its IP Address. An IP address is a group of four bytes (or 32 bits) each of which can be a number from 0 to 255. A typical IP address looks like this: 216.27.63.135 We use this “dotted decimal number” format, to make it easier to remember. But a computer would communicate this in binary format as shown below. 11011000×00011011×00111111×01000111 The four numbers in an IP address are called octet