01 computer communication and networks v


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01 computer communication and networks v

  1. 1. Page 1 of 30 Communication And Network ConceptsNetwork:-Network is an interconnected collection of autonomous computer.Two computers are said to be interconnected if they are capable to exchanginginformation. Autonomous means that no computer on network can start, stop, orcontrol another. NetworkNeed for Networking:-(a) Resource sharing (b) Reliability(c) Cost factor (d) Communication medium(e) Access to Remote DatabaseEvolution of Networking:-Evolution of networking started way back in 1969 by the development of firstnetwork called APRANET, which led to the development of Internet.(i) ARPANET:- The acronym of ARPANET is Advanced Research ProjectsNETwork, was started to connect computers at U.S. Department of Defense andUniversities.In 1980s, National Science Foundation started to make a high capacity networkcalled NSFnet to be used strictly for academic and engineering research. Prepared By Sumit Kumar Gupta, PGT Computer Science
  2. 2. Page 2 of 30In 1990s the internetworking of ARPANET, NSFnet and other private networksresulted into Internet.(ii)The Internet:-The Internet is a super-network which connects the worldwidesmaller networks together and allows all the computers to exchange the information.Internet uses TCP/IP protocols (Transmission control Protocol/ Internet Protocol)for communication.(iii)The Interspace: - Interspace is a client/server software program that allowsmultiple users to communicate online with real-time audio, video and text chat indynamic 3-D environments.Switching Techniques*Switching techniques are used for transmitting data across networks.There are a number of ways to perform switching:  Circuit Switching  Packet Switching  Message Switching  Cell SwitchingCircuit Switching-This method involves the physical interconnection of two devices. A good exampleof circuit switching involves the Public phone network. A data example would bethe classic A/B switch!Packet Switching- Prepared By Sumit Kumar Gupta, PGT Computer Science
  3. 3. Page 3 of 30Packet Switching techniques switch packets of data between destinations.Traditionally, this applied to X.25 techniques, but this also applies to TCP/IP andIPX/SPX routers also. Proprietary Frame Relay switches can switch voice signals.Message Switching-Message Switching techniques were originally used in data communications. Anexample would be early "store and forward" paper tape relay systems. E-Maildelivery is another example of message switching. In voice systems, you can findVoice Mail delivery systems on the Internet. The classic "forward voice mail"example.Cell Switching-Cell Switching is similar to packet switching, except that the switching does notnecessarily occur on packet boundaries. This is ideal for an integrated environmentand is found within Cell-based networks, such as ATM. Cell-switching can handleboth digital voice and data signals.Data Communications Terminologies:- 1. Data Channel- a channel is the medium to carry information or data from one point to another. 2. Baud-It is the unit of measurement for the information carrying capacity of a communication channel. The Baud is synonymous with bps (bits per second). Prepared By Sumit Kumar Gupta, PGT Computer Science
  4. 4. Page 4 of 30 3. Bandwidth-Technically the bandwidth refers to the difference between the highest and lowest frequencies of a transmission channel. High bandwidth channels are called broadband and low bandwidth channels are called narrowband. *The speed of bandwidth is represented by bits per second (bps). *Frequency of bandwidth is measured in cycles per second i.e., hertz. 1 Kilohertz (KHz) =1000Hz 1Megahertz (MHz) =1000 KHz. 1Gigahertz (MHz) =1000MHz. 1Terahertz (MHz) =1000GHz. 4. Data Transfer Rates:-The transfer rate represents the amount of data transferred per second by a communication channel. *Data rate measured in units of bits per second (bps), bytes per second (Bps) or baud. 1 KB=210=1024 bytes 1 MB=1024 KB 1 GB=1024 MB 1 TB=1024 GBTransmission media: - It means the physical materials that are used to transmit databetween computers.Communication media are categorized into two types. 1. Guided Media(Cables) Prepared By Sumit Kumar Gupta, PGT Computer Science
  5. 5. Page 5 of 30 2. Unguided Media(Waves)1. Guided Media-CableFor communications between computers that are linked by cable, there are threechoices.Twisted (phone line) It consists of two identical wires wrappedPair together in a double helix. It is of two types-unshieldedCable Twisted Pair Cable (UTP) ,and Shielded Twisted Pair Cable(STP). Advantage: i) It is simple, easy to install & maintain. ii) It is physically flexible and very cheap. iii) It has low weight & can be easily connected. Disadvantage: i) It is incapable carrying a signal over long distances without the use of repeaters. ii) It is not suitable for broadband application due to low bandwidth( 1 MBPS to 10 MBPS) Prepared By Sumit Kumar Gupta, PGT Computer Science
  6. 6. Page 6 of 30Coaxial (round insulated wire) It consists of a solid wire corecable surrounded by one or more foil or wire shields, each separated by some kind of plastic insulator.it is widely used for television signals. Advantage: i)Data transfer characteristics is better than twisted-pair cables. ii) it can be used for broadband transmission due to higher bandwidth(upto 400 MBPS) Disadvantage: i) Expensive compare to twisted pair cables. ii) It is not compatible with twisted pair cables.Fiber (glass fibers) The data to be transmitted is modulated ontooptic line the light beam using frequency modulation techniques. Advantage: Smaller Lighter Faster (speed of light) No interference Disadvantage: Expensive Harder to install and modify Prepared By Sumit Kumar Gupta, PGT Computer Science
  7. 7. Page 7 of 302.Unguided Media-BroadcastFor longer distances or when cables are not practical, other transmission media comeinto play. Were getting really high tech here.It may seem odd to call microwaves, radio waves, or light a "physical" medium. Allare electromagnetic in nature. Sometimes they are treated by scientists like streamsof teeny, tiny particles and other times like waves on the beach. In their "particle"life, they do behave like a bunch of physical particles. So its not quite as odd as itfirst appears. (But all those electromagnetic things are plenty odd.)Radio Any Radio setup has two parts. i) Transmitter. ii) Receiverwave Both transmitter & Receiver use antennas to radiate & capture the radio signal. Advantage: Flexible Cheaper Portable Ease of communication Disadvantage: Slower data transfer than hard-wired methods Insecure communicationMicrowave Microwave signals are used to transmit data without the use of cables. It is similar to radio & television signals for long distance communication. It consists of transmitter, receiver and atmosphere. Prepared By Sumit Kumar Gupta, PGT Computer Science
  8. 8. Page 8 of 30 Advantage: Speed of light ease of communication. Disadvantage: Insecure communication. High cost of design & maintenance.Satellite The smart phase of communication of global standard is made possible with the aid of satellites. Signals are retransmitted back to the receiver at different frequencies on a global basis. Advantage: Always in sight Disadvantage: Expensive uplink and downlink facilities Infrared This type of transmission uses infrared light to send data. Like TV remotes, wireless speakers. Advantage: Flexible Cheaper Secure communication Portable Ease of communication Disadvantage: Slower data transfer than hard-wired methods Network Devices:- • 1. Modem:- Allows computers to communicate over a telephone line Prepared By Sumit Kumar Gupta, PGT Computer Science
  9. 9. Page 9 of 30 • Enable communication between networks or connecting to the world beyond the LANCannot send digital signal directly to telephone lineSending end: MODulate the computer’s digital signal into analog signal andtransmitsReceiving end: DEModulate the analog signal back into digital formModems come in two varieties: 1. Internal modems the modems are fixed within the computer. 2. External modems the modems that are connected externally to a computer as other peripherals are connected.RJ-45:-RJ-45 is short for Registered Jack -45 is an eight wire connector, which isused to connect computers on the local area networks i.e., LANs especiallyEthernets. Prepared By Sumit Kumar Gupta, PGT Computer Science
  10. 10. Page 10 of 30Ethernet Card:-The computers that are part of Ethernet have to install a specialcard called Ethernet Card. An Ethernet card contains connections for either coaxialor twisted pair cables. Ethernet cards are sometimes known as network interfacecards (NICs).Hub:-A hub is a hardware device used to connect several computers together. Hubscan be either passive or active.Active hubs electrically amplify the signal as it moves from one connected device toanother. It works like Repeaters.Passive hubs allow the signal from one computer to another without any change. Prepared By Sumit Kumar Gupta, PGT Computer Science
  11. 11. Page 11 of 30Switch:-A switch is a device that is used to segment networks into different subnetworks called subnets or LAN segments. A switch is responsible for filtering i.e.,transforming data in a specific way and for forwarding packets between LANsegments. Hub 3.3Mbps 10Mbps 3.3Mbps Switch 3.3Mbps 10Mbps 10MbpsRepeater:-It is a network device that amplifies and restore signals from longdistance transmission.Bridge:-A bridge is a network device that establishes an intelligent connectionbetween two local networks with the same standard but with different types ofcables.Router:-A router is a network device that is used to separate different segments in anetwork to improve performance and reliability. It works like a bridge but canhandle different protocols.Gateway:-A gateway is a network device that connects dissimilar networks. Itestablishes an intelligent connection between local network and external networkswith completely different structures. Prepared By Sumit Kumar Gupta, PGT Computer Science
  12. 12. Page 12 of 30A gateway node often acts as proxy server and a firewall.Different topologies:-There are four basic types of LAN topology.  STAR  BUS  TREELinear Bus-A linear bus topology consists of a main run of cable with a terminator at each end(See fig. 1). All nodes (file server, workstations, and peripherals) are connected tothe linear cable. Ethernet and Local Talk networks use a linear bus topology.Fig. 1. Linear Bus topologyAdvantages of a Linear Bus Topology  Easy to connect a computer or peripheral to a linear bus.  Requires less cable length than a star topology. Prepared By Sumit Kumar Gupta, PGT Computer Science
  13. 13. Page 13 of 30Disadvantages of a Linear Bus Topology  Entire network shuts down if there is a break in the main cable.  Terminators are required at both ends of the backbone cable.  Difficult to identify the problem if the entire network shuts down.  Not meant to be used as a stand-alone solution in a large building.Star -A star topology is designed with each node (file server, workstations, andperipherals) connected directly to a central network hub or concentrator (See fig.2).Data on a star network passes through the hub or concentrator before continuingto its destination. The hub or concentrator manages and controls all functions of thenetwork. It also acts as a repeater for the data flow. This configuration is commonwith twisted pair cable; however, it can also be used with coaxial cable or fiber opticcable.Fig. 2. Star topology Prepared By Sumit Kumar Gupta, PGT Computer Science
  14. 14. Page 14 of 30Advantages of a Star Topology  Easy to install and wire.  No disruptions to the network then connecting or removing devices.  Easy to detect faults and to remove parts.Disadvantages of a Star Topology  Requires more cable length than a linear topology.  If the hub or concentrator fails, nodes attached are disabled.  More expensive than linear bus topologies because of the cost of the concentrators.The protocols used with star configurations are usually Ethernet or LocalTalk.Token Ring uses a similar topology, called the star-wired ring.Tree-A tree topology combines characteristics of linear bus and star topologies. It consistsof groups of star-configured workstations connected to a linear bus backbone cable(See fig. 4). Tree topologies allow for the expansion of an existing network, andenable schools to configure a network to meet their needs. Prepared By Sumit Kumar Gupta, PGT Computer Science
  15. 15. Page 15 of 30Fig. 4. Tree topologyAdvantages of a Tree Topology  Point-to-point wiring for individual segments.  Supported by several hardware and software venders.Disadvantages of a Tree Topology  Overall length of each segment is limited by the type of cabling used.  If the backbone line breaks, the entire segment goes down.  More difficult to configure and wire than other topologies.Types of Networks:-1.Local-area networks (LANs):-->Operate within limited (local) geographical area Prepared By Sumit Kumar Gupta, PGT Computer Science
  16. 16. Page 16 of 30->Allow multi-access to high bandwidth media->Control network privately under local administration->Provide full-time connectivityConnect physically adjacent devicesSome common LAN technologies are: Ethernet Token Ring FDDI2.Wide-area networks (WANs):-->Operate over a large geographical area->Use serial interfaces (e.g. modem) operating at lower speeds->Provide full-time and part-time connectivity->Connect devices separated over wide areasSome common WAN technologies are: Modems Digital Subscriber Line (DSL) Cable modem3.Metropolitan Area Network(MAN):-MAN are the networks spread over a city. For example, cable TV networks. Prepared By Sumit Kumar Gupta, PGT Computer Science
  17. 17. Page 17 of 30Protocols:-It is a set of rules which govern data communication. It is formaldescription of message formats and the rules that two or more machines must followto exchange those messages.1.FTP(File Transfer Protocol):-FTP allows you to transfer files between two computers on the Internet. FTP is asimple network protocol based on Internet Protocol and also a term used whenreferring to the process of copying files when using FTP technology.Advantages:- i) It is very useful to transfer files from one network in an organizatrion to another. ii) It is an effective way to get a geographically dispersed group to co- operate on a project. iii) It is a potent and popular way to share information over the internet.Objectives of FTP:- i) to prompt sharing of files ii) to encourage indirect or implicit use of remote computers.2.TCP/IP(Transmission control protocol/Internet protocol):-Transmission Control Protocol (TCP) and Internet Protocol (IP) are two distinctnetwork protocols, technically speaking. TCP and IP are so commonly usedtogether, however, that TCP/IP has become standard terminology to refer to either orboth of the protocols.IP corresponds to the Network layer (Layer 3) in the OSI model, whereas TCPcorresponds to the Transport layer (Layer 4) in OSI. In other words, the term TCP/IP Prepared By Sumit Kumar Gupta, PGT Computer Science
  18. 18. Page 18 of 30refers to network communications where the TCP transport is used to deliver dataacross IP networks.TCP/IP application use 4 layers. i) an application protocol such as mail. ii) A protocol such as TCP that provides services need by many applications. iii) IP, which provides the basic services of getting datagrams to their destination. iv) The protocols needed to manage a specific physical medium,such as Ethernet or a point to point line.*Datagram is a collection of the data that is sent as a single message.3.HTTP(Hypertext Transfer Protocol):-It is an application –level protocol with the lightness and speed necessary fordistributed ,collaborative hypermedia systems.4.SLIP/PPP:-SLIP(Serial Line Internet Protocol) /PPP(Point to Point Protocols)provide the ability to transport TCP/IP traffic ever serial line between twocomputers.Telnet(TErminaL NETwork):-Telnet is an Internet utility that lets you log ontoremote computer systems. Prepared By Sumit Kumar Gupta, PGT Computer Science
  19. 19. Page 19 of 30Wireless/Mobile communication:- This is simply data communication withoutthe use of landlines. Mobile computing means that the computing device is notcontinuously connected to the base or central network.GSM(Globle System for Mobile):- uses narrowband TDMA(Time Division Multiple access) which allows eight simultaneous calls on the same radio frequency.CDMA(Code Division Multiple Access):-uses a speed –spectrum technique where data is sent in small pieces over a number of discrete frequencies available for use. Each user’s signal is spread over the entire bandwidth by unique spreading code. At the receiver end the same unique code is used to recover the signal.WLL(Wireless in Local Loop):-It is a system that connects subscribers to thepublic switched telephone(or PBX) network using radio signal as a substitute forother connecting media.3G(third Generation):-3G mobile communication technology is a broadband,packet-based transmission of text, digitized voice, video and multimedia at data ratesup to and possibly higher than 2Mbps provides set of services to mobile computerand phone users.1SMS(Short Message Service):-It is the transmission of short text messages toand from a mobile phone ,fax machine and/or IP address.Voice Mail:-It refers to e-mail system that supports audio.Email(Electronic mail):-It is sending and receiving message s by computer. Prepared By Sumit Kumar Gupta, PGT Computer Science
  20. 20. Page 20 of 30Advantages of email:-i) low cost. ii) Speed iii) Waste reduction.Chat:-Online textual talk,in real time, is called Chatting.Video Conferencing:- A two-way videophone conversation among multipleparticipants is called Video Conferencing.Network Security Concepts:-1.Cyber Law:- Cyber law (also referred to as Cyberlaw) is a term used to describethe legal issues related to use of communications technology, particularly"cyberspace", i.e. the Internet.. In essence, cyber law is an attempt to apply lawsdesigned for the physical world to human activity on the Internet.Cyber law is impotant because it touches almost all aspects of transactions activitieson aaand concerning the Inernet ,the World Wide Web and Cyberspace.Virus threats and prevention:- Today’s threats bring us any combination ofTrojans, worms, and viruses in one tidy package.Antivirus software is must-haveprotection. Keep it installed, enabled, and up-to-date at all times. But thoughantivirus software is critical, alone its not enough to keep you protected. Followsound security practices, install a firewall, and use other adjunct protection incombination with your own common sense. Prepared By Sumit Kumar Gupta, PGT Computer Science
  21. 21. Page 21 of 30Cookies:- are messages that Web server transmits to a Web browers so that Webserver can keeo track of the user’s activity on a specific Web site.It is a text sent bya server to a web client (usually a browser) and then sent back unchanged by theclient each time it accesses that server.Cookies have six parameters that can be passed to them:-Name,Value,expiration date ,path,domain and secure server for Cookies..Hackering:-Hacker (computer security), someone who breaks computer and network security.Hacker is a person who enjoys learning programming languagees and computersystems and can often be considered an expert on the subject.Hackers themselvesmaintain that the proper term for such individual is cracker.Thus Crackers are the malicious parogrammers who break into secure systemswhereas Hackers are more interested in gaining knowledge about computer systemsand possibly using this knowledge for playful pranks.Firewall:-The system designed to prevent unathorized to or from a private networkis called Filewall.XML (eXtensible Markup Language) : -Xml is a markup language fordocuments containing structured information.HTML(Hypertext Markup Language) :-It is a language which is use to webpage design.It is ajust page-layoand hyperlink specificationut . Prepared By Sumit Kumar Gupta, PGT Computer Science
  22. 22. Page 22 of 30DHTML ( Dynamic Hypertext Markup Language): - DHTML is a TERMdescribing the art of making dynamic and interactive web pages.it is HTMLextension that will enable a Web page to react to user input without sending requestto the web server.URL(Uniform Resource Locator):-Internet addresses in a special format calleda URL. i.e. http:/www.yahoo.com. DNS(Domain Name System):- An Internet address which is character based is called a DNS.Website:- A location on a net server is called Web Site.A document that uses HTTP is called Web Page.Web browser:-It is a WWW(World Wide Web) client that navigates through the WWW and displays web pages.Web server:-It is a WWW server that responds to the requests made by web browsers.Web hosting:-It is a means of hosting a web-server application on a computersystem through which electronic content on the internet is readily available to anyweb-browser client.*The computer system providing the web-hosting is known as web-server or theweb-host. Prepared By Sumit Kumar Gupta, PGT Computer Science
  23. 23. Page 23 of 30Solved Questions of AISSE Computer Science (2008)Q 1.What is modem? Q.2Expand the following term PPP GSM XML HTTPQ.3 how is Hacker different from Cracker?Q4.China Middleton Fashion is planning to expand their network in India, Startingwith two cities in India to provide infrastructure for distribution of their product. Thecompany has planned to set up their main office units in Chennai at three differentlocation and have named their offices as “Production Unit” “Finance Unit” and“Media Unit”. The company has its corporate unit in Delhi.A rough layout of the same is as follow: Prepared By Sumit Kumar Gupta, PGT Computer Science
  24. 24. Page 24 of 30 INDIA Corporate unit (DELHI) Production unit Finance unit Media unitApproximate distance between these Units as follow: From TO Distance Production unit Finance Unit 70 Mtr Production unit Media Unit 15 KM Production unit Corporate Unit 2112 KM Finance Unit Media Unit 15KMIn continuation of the above, The company expert have planned to install thefollowing number of computers in each of their office units Production 150 Unit Prepared By Sumit Kumar Gupta, PGT Computer Science
  25. 25. Page 25 of 30 Finance Unit 35 Media Unit 10 Corporate Unit 30 (i) Suggest the kind of network required(out of LAN,MAN,WAN)for connecting each of the following office units:  Production nit and Media unit  Production Unit and Finance Unit (ii) Which one of the following Device s will you suggest for connecting all the Computers within each of their office units?  Switch/Hub  Modem  Telephone (iii) Which of the following communication media , will you suggest to be produced by the company for connecting their local office units in Chennai for very effective (High Speed) communication.  Telephone Cable  Optical Fiber  Ethernet Card (iv) Suggest a cable/wiring layout for connecting the Company’s S local office units located in Chennai .Also suggest an effective method/technology for connecting the company’s office unit located in Delhi. Solved Answer of 2008Q.1 Modem:-Modem is a Modulation Demodulation device that convert analogsignal to digital signal and vice versa. Prepared By Sumit Kumar Gupta, PGT Computer Science
  26. 26. Page 26 of 30 Q.2 Hackers are the ones who get into someone’s code or computer without any malicious intention ,where as Crackers are the one’s who get into someone’s code or computer with malicious intention. Q.3 PPP(Point to point Protocol) GSM(Global System for Mobile) XML(eXtensible Markup Language) HTTP(Hyper Text Transfer Protocol) Q.4 (i) Production nit and Media unit: MAN Production Unit and Finance Unit: LAN (ii)Switch/Hub (iii)Optical fiber INDIASatelliteAntennaSatelliteSignal Production unitOpticalFiberQuestions:- Corporate unit Questions:-(iv)Optical Fiber/Star Topology (DELHI) Wireless/Satellite Link/Leased LineEthernet Finance unit MediaCable Prepared By Sumit Kumar Gupta, PGT Computer Science
  27. 27. Page 27 of 30Very Short Questions:-  What is Network? Why is it needed  Explain Communication Channel  Explain Different types of Network?  Explain LAN topology?  What is Bandwidth? How is it measured?  What is the role of modem in communication?  What is the different between Hub and Switch?  Explain the Protocols?  What is web hosting?  What is video conferencing?  What is Firewall?  What is hacking?Short Questions:-  Discuss the various types of network?  What is the difference between Internet and Intranet?  Define network security. What is its need?  Compare the Fiber and Coaxial Transmission Media.  What is difference between Hackers and Crackers  Expand and explain the following terms:  XML,HTML,DHTML,GSM,HTTP,WWW,WLL,ISP,CDMA,SMS,FTP  What is URL  What is Protocols?  Define the following term Bridge, Repeater, mail, chatting TCP/IP,TELNET, CookiesLONG ANSWER QUESTIONS:-Q .1 The Great Brain Organization has set up its new Branch at Shrinagar for itsoffice and web based activities .It has 4 wings to building as shown in the diagram Prepared By Sumit Kumar Gupta, PGT Computer Science
  28. 28. Page 28 of 30 Wing Z Wing Y Wing X Wing UCenter to center distance between various blocks Wing X To Wing Z 50 m Wing Z To Wing Y 70 m Wing Y To Wing X 125 m Wing Y To Wing U 80 m Wing X To Wing U 175 m Wing Z To Wing U 90 m Number of computers Wing X 50 Wing Z 30 Wing Y 150 Wing U 15 (i) Suggest a suitable layout of connection between the wings and topology. (ii) Suggest a suitable place (i.e. wing) to house the server of this organization with a suitable reason with justification (iii) Suggest the placement of the following devices with justification. (a)Repeater (b) Hub/Switch Prepared By Sumit Kumar Gupta, PGT Computer Science
  29. 29. Page 29 of 30 (iv) The Organization is planning to link its head office situated in the Delhi with the offices of Shrinagar.Suggest a economic way to connect it: if the company is ready to compromise on the speed of connectivity .Justify your Answer.Ans: -( i) BUS Topology Wing Z Wing Y Wing X Wing U(ii) The most suitable place to house the server is Wing Y as it has the most numberof computers thus cabling cost will be reduced and traffic will be local(iii) Repeater(iv)Dial-up or Broadband.Q.2. K.V. No1 in Bhubaneswar is setting up the network between itsdifferent wings. There are wings named as CRPF(S),MANCHESWAR(J),CUTTACK(A) and PURI(H).Distance between various wings is given below:- Wing A To Wing S 100 m Wing A To Wing J 200 m Wing A To Wing H 400 m Prepared By Sumit Kumar Gupta, PGT Computer Science
  30. 30. Page 30 of 30 Wing S To Wing J 300 m Wing S To Wing H 100 m Wing J To Wing H 450 mNumber of computers Wing A 20 Wing S 200 Wing J 100 Wing H 50(i) Suggest a suitable Topology for Networking the Computer of all Wings.(ii) Name the wing where the server is to be installed(iii) Suggest the placement of Hub/Switch in the network.(iv) Mention an economic technology to provide internal accessing to all wingsAns:-(i)star topology(ii)wing S(iii)Hub/Switch will be required in all the wings(iv)dial-up networkSubmitted by : Ramesh Singh (K.V. Bondamunda) Deepa Behera(K.V. Rourkela) Kusum Kumari(K.V.Hinoo, Ranchi) Prepared By Sumit Kumar Gupta, PGT Computer Science