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Maharashtra State Board of Technical Education, Mumbai, , Course Name : Diploma in Computer Engineering, Semester : Fourth (I Scheme), Subject Name : Data Communication and Computer Network, Subject Code : 22414, , Unit – I, Fundamentals of Data Communication and Computer Network, (12 Marks), Prepared By, A.K. Rathod, (M.E. C.N.E.), Lecturer in Computer Engineering, Government Polytechnic Jintur District Parbhani, , 1
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Unit – I Fundamentals of Data Communication and Computer Network, , Unit Outcomes (in Cognitive Domain), 1 a. Describe role of a given component in the process of data, communication., 1 b. Compare the characteristics of analog and digital signals on the given, Parameter., 1 c. Explain the process of data communication using the given mode., 1 d. Classify the computer networks on the given parameters., 1 e. Select network architecture for the given situation with justification., , 2
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Unit – I Fundamentals of Data Communication and Computer Network, , 1.1 Process of Data Communication and its Components :, - Transmitter, Receiver, Medium Message, Protocol., Data communication : It refers to the exchange of data between a source, and a receiver via form of transmission media such as a wire / cable or, , wireless transmission. Data communication is said to be local if, communicating devices are in the same building or a similarly restricted, geographical area., , The meanings of source and receiver are very simple. The device, that transmits the data is known as source and the device that receives the, transmitted data is known as receiver. Data communication aims at the, , transfer of data and maintenance of the data during the process but not the, actual generation of the information at the source and receiver., 3
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Unit – I Fundamentals of Data Communication and Computer Network, , 4
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Unit – I Fundamentals of Data Communication and Computer Network, Components of data communication system, A Communication system has following components:, 1.Message: It is the information or data to be communicated. It can consist of text,, numbers, pictures, sound or video or any combination of these., 2.Sender: It is the device/Computer that generates and sends that message., 3.Receiver: It is the device or Computer that receives the message. The location of, receiver computer is generally different from the sender computer. The distance between, sender and receiver depends upon the types of network used in between., 4.Medium: It is the channel or physical path through which the message is carried from, sender to the receiver. The medium can be wired like twisted pair wire, coaxial cable,, fiber-optic cable or wireless like laser, radio waves, and microwaves., 5.Protocol: It is a set of rules that govern the communication between the devices. Both, sender and receiver follow same protocols to communicate with each other., 5
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Unit – I Fundamentals of Data Communication and Computer Network, A protocol performs the following functions:, 1. Data sequencing. It refers to breaking a long message into smaller packets of fixed, size. Data sequencing rules define the method of numbering packets to detect loss or, , duplication of packets, and to correctly identify packets, which belong to same message., 2. Data routing. Data routing defines the most efficient path between the source and, destination., 3. Data formatting. Data formatting rules define which group of bits or characters, within packet constitute data, control, addressing, or other information., 4. Flow control. A communication protocol also prevents a fast sender from, overwhelming a slow receiver. It ensures resource sharing and protection against traffic, congestion by regulating the flow of data on communication lines., 5. Error control. These rules are designed to detect errors in messages and to ensure, transmission of correct messages. The most common method is to retransmit erroneous, message block. In such a case, a block having error is discarded by the receiver and is, retransmitted by the sender., , 6
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Unit – I Fundamentals of Data Communication and Computer Network, A protocol performs the following functions:, 6. Precedence and order of transmission. These rules ensure that all the nodes get a, chance to use the communication lines and other resources of the network based on the, , priorities assigned to them., 7. Connection establishment and termination. These rules define how connections are, established, maintained and terminated when two nodes of a network want to, , communicate with each other., 8. Data security. Providing data security and privacy is also built into most, communication software packages. It prevents access of data by unauthorized users., , 9. Log information. Several communication software are designed to develop log, information, which consists of all jobs and data communications tasks that have taken, place. Such information may be used for charging the users of the network based on, their usage of the network resources., , 7
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Unit – I Fundamentals of Data Communication and Computer Network, The effectiveness depends on four fundamental characteristics of data, communications. –, 1. Delivery- The system must deliver data to the correct destination. Data must be, received by the intended device or user and only by that device or user., 2. Accuracy- The system must deliver the data accurately. Data that have been altered in, transmission and left uncorrected are unusable., 3. Timeliness- The system must deliver data in a timely manner. Data delivered late are, useless. In the case of video and audio, timely delivery means delivering data as they are, produced, in the same order that they are produced, and without significant delay. This, kind of delivery is called real-time transmission., 4. Jitter- Jitter refers to the variation in the packet arrival time. It is the uneven delay in, the delivery of audio or video packets. For example, let us assume that video packets are, sent every 3-ms. If some of the packets arrive with 3-ms delay and others with 4-ms, delay, an uneven quality in the video is the result., 8
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Unit – I Fundamentals of Data Communication and Computer Network, 1.2 Protocols, Standards, Standard Organizations, Bandwidth, Data, Transmission Rate, Baud Rate, Bits Per Second. :PROTOCOL : - A Protocol is one of the components of a data communications system., , Without protocol communication cannot occur. The sending device cannot just send the, data and expect the receiving device to receive and further interpret it correctly., When the sender sends a message it may consist of text, number, images, etc. which are, , converted into bits and grouped into blocks to be transmitted and often certain additional, information called control information is also added to help the receiver interpret the data., For successful communication to occur, the sender and receiver must agree upon certain, , rules called protocol., A Protocol is defined as a set of rules that governs data communications., A protocol defines what is to be communicated, how it is to be communicated and when it, is to be communicated., 9
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Unit – I Fundamentals of Data Communication and Computer Network, Elements of a Protocol :- There are three key elements of a protocol:, A. Syntax - It means the structure or format of the data. It is the arrangement of data in a, particular order., , B. Semantics - It tells the meaning of each section of bits and indicates the interpretation, of each section. It also tells what action/decision is to be taken based on the interpretation., C. Timing - It tells the sender about the readiness of the receiver to receive the data It, , tells the sender at what rate the data should be sent to the receiver to avoid overwhelming, the receiver., STANDARDS : - Standards are necessary in networking to ensure interconnectivity and, interoperability between various networking hardware and software components., Without standards we would have proprietary products creating isolated islands of users, which cannot interconnect., , 10
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Unit – I Fundamentals of Data Communication and Computer Network, Concept of Standard :- Standards provide guidelines to product manufacturers and, vendors to ensure national and international interconnectivity. Data communications, standards are classified into two categories:, 1. De facto Standard - De facto standards are those which have been accepted as the, best standard for their purpose. They have evolved to be accepted because of wide, public support and market forces. This is often because they have a proven track, record for efficiency and reliability. These standards are not approved by any, organized body but are adopted by widespread use. Examples of de facto standards, include: the QWERTY keyboard, the Windows operating system, 2. De jure standard - De jure standards are those which have been approved by formal, authorities like the Institute of Electrical and Electronics Engineers (IEEE) and the, International Organization for Standardization (ISO). These standards are critically, assessed before being approved. An example of a de jure standard is, the, , ASCII, , character, , set., , Some, , de, , jure, , hardware, , standards, , include USB, FireWire and HDMI., 11
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Unit – I Fundamentals of Data Communication and Computer Network, STANDARD ORGANIZATIONS :- Standards are created by standards creation, committees, forums, and government regulatory agencies., Examples of Standard Creation Committees :, 1. International Organization for Standardization(ISO), 2. International Telecommunications Union – Telecommunications Standard (ITU-T), 3. American National Standards Institute (ANSI), , 4. Institute of Electrical & Electronics Engineers (IEEE), 5. Electronic Industries Associates (EIA), Examples of Forums, , 1. ATM Forum, 2. MPLS Forum, 3. Frame Relay Forum, , Examples of Regulatory Agencies: 1. Federal Communications Committee (FCC), 12
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Unit – I Fundamentals of Data Communication and Computer Network, BANDWIDTH :Bandwidth is measured as the amount of data that can be transferred from one, point to another within a network in a specific amount of time. Typically, bandwidth is, expressed as a bitrate and measured in bits per second (bps). Bandwidth can be defined as, the portion of the electromagnetic spectrum occupied by the signal. It may also be defined, as the frequency range over which a signal is transmitted., , Different types of signals have different bandwidth. Ex. Voice signal, music, signal, etc. Bandwidth of analog and digital signals are calculated in separate ways; analog, signal bandwidth is measured in terms of its frequency (hz) but digital signal bandwidth is, , measured in terms of bit rate (bits per second, bps) Bandwidth of signal is different from, bandwidth of the medium/channel., The bandwidth of the medium should always be greater than the bandwidth of, , the signal to be transmitted else the transmitted signal will be either attenuated or distorted, or both leading in loss of information. The channel bandwidth determines the type of, signal to be transmitted i.e. analog or digital., , 13
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Unit – I Fundamentals of Data Communication and Computer Network, DATA TRANSMISSION RATE :The data transfer rate (DTR) is the amount of digital data that is moved from, one place to another in a given time. The data transfer rate can be viewed as the speed of, travel of a given amount of data from one place to another. In general, the greater, the bandwidth of a given path, the higher the data transfer rate., In telecommunications, data transfer is usually measured in bits per second. For, , example, a typical low-speed connection to the Internet may be 33.6 kilobits per second, (Kbps). On Ethernet local area networks, data transfer can be as fast as 10 megabits per, second. Network switches are planned that will transfer data in the terabit range. In earlier, , telecommunication systems, data transfer was sometimes measured in characters or blocks, (of a certain size) per second. Data transfer time between the microprocessor or RAM and, devices such as the hard disk and CD-ROM player is usually measured in milliseconds., , In computers, data transfer is often measured in bytes per second. The highest data transfer, rate to date is 14 terabits per second over a single optical fiber., 14
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Unit – I Fundamentals of Data Communication and Computer Network, BIT RATE and BAUD RATE :BIT RATE - It is the number of bits transmitted in one second. It is expressed as bits per, second (bps). Relation between bit rate and bit interval can be as follows Bit rate = 1 / Bit, interval 2.4.5, Baud Rate - It is the rate of Signal Speed, i.e. the rate at which the signal changes. A, digital signal with two levels „0„ & „1„ will have the same baud rate and bit rate & bit rate., The diagram below shows three signal of period (T) 1 second a) Signal with a bit rate of 8, bits/ sec and baud rate of 8 baud/sec b) Signal with a bit rate of 16 bits/ sec and baud rate, of 8 baud/sec c) Signal with a bit rate of 16 bits/ sec and baud rate of 4 baud/sec., , 15
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Unit – I Fundamentals of Data Communication and Computer Network, 1.3 Modes of Communication :Data Transmission mode defines the direction of the flow of information, between two communication devices. It is also called Data Communication or Directional, , Mode. It specifies the direction of the flow of information from one place to another in a, computer network., In the Open System Interconnection(OSI) Layer Model, the Physical Layer is, , dedicated to data transmission in the network. It mainly decides the direction of data in, which the data needs to travel to reach the receiver system or node., The data transmission modes can be characterized in the following three types based on, the direction of exchange of information:, 1. Simplex, 2. Half-Duplex, 3. Full Duplex, , 16
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Unit – I Fundamentals of Data Communication and Computer Network, 1. Simplex Mode:Simplex is the data transmission mode in which the data can flow only, in one direction, i.e., the communication is unidirectional. In this mode, a sender, can only send data but can not receive it. Similarly, a receiver can only receive, data but can not send it., This transmission mode is not so popular because we cannot perform, two-way communication between the sender and receiver in this mode. It is, mainly used in the business field as in sales that do not require any corresponding, , reply. It is similar to a one-way street., For Example, Radio and TV transmission, keyboard, mouse, etc., Direction of Data Flow at all Time, , Sender, , Receiver, , Device 1, , Device 2, Fig – Simplex Mode, , 17
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Unit – I Fundamentals of Data Communication and Computer Network, Following are the advantages of using a Simplex transmission mode:, •, , It utilizes the full capacity of the communication channel during data, transmission., , •, , It has the least or no data traffic issues as data flows only in one, direction., , Following are the disadvantages of using a Simplex transmission mode:, , • It is unidirectional in nature having no inter-communication between, devices., • There is no mechanism for information to be transmitted back to the, , sender(No mechanism for acknowledgement)., , 18
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Unit – I Fundamentals of Data Communication and Computer Network, 1. Half-Duplex Mode : Half-Duplex is the data transmission mode in which the data can flow in, both directions but in one direction at a time. It is also referred to as SemiDuplex. In other words, each station can both transmit and receive the data but, not at the same time. When one device is sending the other can only receive and, vice-versa. In this type of transmission mode, the entire capacity of the channel, can be utilized for each direction. Transmission lines can carry data in both, directions, but the data can be sent only in one direction at a time., Direction of Data Flow at Time T1, , Sender, , Receiver, , Receiver, , Sender, , Device 1, , Direction of Data Flow at Time T2, , Device 2, , Fig – Half-Duplex Mode, 19
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Unit – I Fundamentals of Data Communication and Computer Network, This type of data transmission mode can be used in cases where there is, no need for communication in both directions at the same time. It can be used for, error detection when the sender does not send or the receiver does not receive the, data properly. In such cases, the data needs to be transmitted again by the, receiver. For Example, Walkie-Talkie, Internet Browsers, etc., Following are the advantages of using a half-duplex transmission mode:, It facilitates the optimum use of the communication channel., It provides two-way communication., , Following are the disadvantages of using a half-duplex transmission mode:, The two-way communication can not be established simultaneously at the, same time., , Delay in transmission may occur as only one way communication can be, possible at a time., 20
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Unit – I Fundamentals of Data Communication and Computer Network, 1. Full-Duplex Mode : Full-Duplex is the data transmission mode in which the data can flow in, both directions at the same time. It is bi-directional in nature. It is two-way, , communication in which both the stations can transmit and receive the data, simultaneously., Full-Duplex mode has double bandwidth as compared to the halfduplex. The capacity of the channel is divided between the two directions of, communication. This mode is used when communication in both directions is, required simultaneously., Sender, Receiver, , Receiver, Direction of Data Flow at all Time, , Device 1, , Sender, , Device 2, Fig – Full-Duplex Mode, 21
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Unit – I Fundamentals of Data Communication and Computer Network, For Example, a Telephone Network, in which both the persons can talk and listen, to each other simultaneously., Following are the advantages of using a full-duplex transmission mode:, The two-way communication can be carried out simultaneously in both, directions., It is the fastest mode of communication between devices., Following are the disadvantages of using a full-duplex transmission mode:, The capacity of the communication channel is divided into two parts. Also,, , no dedicated path exists for data transfer., It has improper channel bandwidth utilization as there exist two separate, paths for two communicating devices., , 22
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Unit – I Fundamentals of Data Communication and Computer Network, 1.4 Analog Signal and Digital Signal :- A signal is an electromagnetic or electrical, current that carries data from one system or network to another. In electronics, a signal is, often a time-varying voltage that is also an electromagnetic wave carrying information,, though it can take on other forms, such as current. There are two main types of signals, used in electronics: analog and digital signals., Analog Signal :- Analog signal is a continuous signal in which one time-varying quantity, represents another time-based variable. These kind of signals works with physical values, and natural phenomena such as earthquake, frequency, volcano, speed of wind, weight,, lighting, etc. An analog signal can be defined by using amplitude, time period, frequency,, , & phase. Amplitude streaks the highest height of the signal, frequency streaks the rate at, which an analog signal is varying, and phase streaks the signal position with respect to, time nothing. An analog signal is not resistant toward the noise, therefore; it faces, , distortion as well as reduces the transmission quality. The analog signal value range, cannot be fixed., 23
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Unit – I Fundamentals of Data Communication and Computer Network, Characteristics Of Analog Signal These type of electronic signals are time-varying, Minimum and maximum values which is either positive or negative., It can be either periodic or non-periodic., Analog Signal works on continuous data., The accuracy of the analog signal is not high when compared to the digital signal., , It helps you to measure natural or physical values., Analog signal output form is like Curve, Line, or Graph, so it may not be meaningful, to all., , 24
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Unit – I Fundamentals of Data Communication and Computer Network, Digital Signal :- A digital signal is a signal that is used to represent data as a sequence of, separate values at any point in time. It can only take on one of a fixed number of values., This type of signal represents a real number within a constant range of values. Similar to, analog, digital signals carry the data although it is a bit different., These signals are discrete or not continuous. A digital signal carries the data in, the form of binary because it signifies in the bits. These signals can be decomposed into, sine waves which are termed as harmonics. Every digital signal has amplitude, frequency,, & phase like the analog signal. This signal can be defined by bit interval as well as bit rate., Here, bit interval in nothing but the required time for transmitting an only bit, whereas the, , bit rate is bit interval frequency., Digital signals are more resistant toward the noise; therefore, it barely faces, some distortion. These waves are simple in transmitting as well as more dependable while, , contrasted to analog waves. Digital signals include a limited variety of values which lies, among 0-to-1., 25
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Unit – I Fundamentals of Data Communication and Computer Network, , Fig: - Digital Signal, , Characteristics of Digital Signals, Digital signal are continuous signals, This type of electronic l signals can be processed and transmitted better compared to, analog signal., Digital signals are versatile, so it is widely used., The accuracy of the digital signal is better than that of the analog signal., 26
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Unit – I Fundamentals of Data Communication and Computer Network, Difference between Analog Signal and Digital Signal :Analog Signal, , Digital Signal, , An analog signal signifies a continuous signal, that keeps changes with a time period., , A digital signal signifies a discrete signal that, carries binary data and has discrete values., , Analog signals are continuous sine waves, , Digital signal is square waves., , Analog signals describe the behavior of the, wave with respect to amplitude, time period,, & phase of the signal., , Digital signals describe the behavior of the, signal with respect to the rate of a bit as well, as bit interval., , Analog signal range will not be set., , Digital signal is limited as well as ranges, from 0 to 1., , Analog signal is further horizontal toward, distortion during the response to noise., , A digital signal has resistance in response, toward the noise, therefore, it does not often, face distortion., , An analog signal broadcasts the information, in the signal form., , A digital signal broadcasts the information in, the form of binary that is bits., , The example of an analog signal is the, human voice, , The example of a digital signal is the data, transmission in a computer., , 27
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Unit – I Fundamentals of Data Communication and Computer Network, , 1.5 Fundamentals of Computer Network :Definition of Computer Network : A computer network is a system in which, multiple computers are connected to each other to share information and resources., , Fig : Computer Network, , Characteristics of Computer Network :, , , Share resources from one computer to another., , Create files and store them in one computer, access those files from the other, computer(s) connected over the network., Connect a printer, scanner, or a fax machine to one computer within the network and let, other computers of the network use the machines available over the network., , 28
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Unit – I Fundamentals of Data Communication and Computer Network, Need of Computer Network :- Computer networks have become valuable to, organizations as well as individuals. Some of its main uses are Internet access, ecommerce, Entertainment, VoIP is briefly explained below., Internet access: We can easily access information all because of the internet, which provides a variety of information and communication facilities, using, standardized communication protocols., e-commerce: also known as electronic commerce, refers to buying or selling, product, service etc through the internet. It has been one of the world most, profitable business in the world which is only possible of a computer network., Entertainment: It includes games, online video streaming and many other which, is only possible because of the computer network., VoIP: Through Voice over Internet protocol, telephone calls are made digitally, using Internet Protocols instead of the regular analog phone lines., 29
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Unit – I Fundamentals of Data Communication and Computer Network, Components of Computer Network :-, , Two or more computers, Cables as links between the computers, A network interfacing card(NIC) on each computer, Network operating system (NOS), Connectors, Networking Devices (Switches, Hub, Routers, Bridges, Gateways), , Applications of Computer Network : File Sharing, , Resources such as printer, scanner sharing., Communication., Remote Access, , Centralized data management., 30
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Unit – I Fundamentals of Data Communication and Computer Network, , Benefits of Computer Network : Sharing, (Hardware and Software), , Connectivity, , Other Benefits of Computer Network : Increased speed, Reduced cost, Improved security, Centralized software managements, Electronic mail, , Flexible access, 31
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Unit – I Fundamentals of Data Communication and Computer Network, Disadvantages of Computer Network : High cost of installation, Requires time for administration, , Failure of server, Cable faults, , 32
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Unit – I Fundamentals of Data Communication and Computer Network, Classification of Computer Network :- Network can be broadly classified, based on two types., 1., , Classification of Network Based on Their Geographical Area., , Examples :, Local Area Network,, Wide Area Network,, Metropolitan Area Network,, Personal Area Network,, Campus Area Network., 1., , Classification of Network Based on Their Role of Component, , Examples :, , Peer to Peer Network,, Client Server Network,, 33
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Unit – I Fundamentals of Data Communication and Computer Network, Classification of Network Based on Their Geographical Area., , Local Area Network :-, , It is a privately-owned network. A network is a group, , of computers and other devices connected so they can pass information back and, forth. The local area network (LAN) is a network which is designed to operate over a, small physical area such as an office, factory or a group of buildings up to a few, kilometers in size. LANs very widely used in a variety of computers to share, resources (e.g., printers) and exchange information., The personal computers and workstations in the offices are interconnected, via LAN to share resources. The resources to be shared can be hardware like, a printer or software's or data. A LAN is a form of local (limited-distance), shared, packet network for computer communications. In LAN all the machines are, connected to a single cable. The data rates for LAN range from 4 to 16 Mbps with, the maximum of 100 Mbps. Example of LAN are Ethernet, Local Talk., 34
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Unit – I Fundamentals of Data Communication and Computer Network, The components used by LANs can be divided into cabling standards,, hardware, and protocols. Various LAN protocols are Ethernet, Token Ring: TCP/IP,, NetBIOS and NetBeui, IPX/SPX, Fiber Distributed Data Interchange (FDDI) and, , Asynchronous Transfer Mode (ATM)., , LANs can be distinguished from different types of networks by their size, their, transmission technology, and their topology., , A local-area network (LAN) restricted in size, which means that it can span in a, relatively small area., , 35
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Unit – I Fundamentals of Data Communication and Computer Network, LANs use a transmission technology consisting of a cable. Traditional, LANs technology transmits at speeds of 10 Mbps to 100 Mbps and makes very, few errors. However, current LANs technology transmits at up to 10 Gbps., , Various network topologies are possible for broadcast LANs. In a linear, cable network (Bus), at any given time, one client machine is the master, machine, and that is only allowed to transmit. All other machines refrain from, sending data. The second type of broadcast LANs is the ring. In it, LAN operating, at 4 and 16 Mbps. FDDI is another example of a ring network., Types of LAN, Ethernet is the most common type of LAN. Different Lan can be differentiated, on the behalf of following characteristics., , 36
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Unit – I Fundamentals of Data Communication and Computer Network, Protocols: It is a guidelines for communicating data between two devices. The, protocols, , also, , determine, , type, , of, , error, , and, , data, , compression., , Media: The cable used in Lan to connect devices are twisted-pair wire, coaxial, cables, or fiber optic., Example of Lan Topologies, Various topologies are possible for the broadcast LANs such as bus topology or, ring topology., , 37
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Unit – I Fundamentals of Data Communication and Computer Network, , Advantages of LAN :• LAN work on higher operating speed than WAN and MAN., • LAN are suitable for the requirements of a specific organization., • LAN are easy to install and maintain., • LAN exist as connected (wired) and wireless configurations., , Applications of LAN : File-based services., , Print services, Application-based services, Mail and message-based services, , Database services, Distributed data services, Remote Access Services, 38
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Unit – I Fundamentals of Data Communication and Computer Network, , Metropolitan Area Network (MAN) :The MAN network (Metropolitan Area Network) is a high-speed network, , (broadband) that covers larger geographic area such as city (tens of kilometers) or, districts than local area network (LAN) but smaller than wide area network (WAN), and providing the ability to integrate multiple services through the transmission of, data, voice, and video, on transmission media such as copper, fiber optics, and, microwaves., The term is applied to the single network such as a cable television network,, or it can be a way of connecting a certain number of LANs in a more extensive, network so that resources can share from LAN to LAN and from device to device., For example, a company can use a MAN to connect the LANs of all its offices, scattered around the city. Local libraries and government agencies often use a MAN, to connect to citizens and private industries. It may also connect MANs within a, larger area than LAN. The geographical limit of a MAN may span a city., , 39
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Unit – I Fundamentals of Data Communication and Computer Network, In MAN, different LANs connected through a local telephone exchange., Some of the widely used protocols for MAN are X.25, Frame Relay, Asynchronous, Transfer Mode (ATM), ISDN (Integrated Services Digital Network), xDSL (Digital, , Subscriber Line), ADSL (Asymmetrical Digital Subscriber Line), WDM (Wavelength, Division Modulation), etc. These protocols are quite different from those used for, LANs., , A MAN can wholly own by a private company, This type of networks is a, larger version than the LAN. The networks of the metropolitan area, comprise a, specific geographical location “city, the municipality,” and its distance of coverage is, , greater than 4 km. They are networks with two unidirectional buses, each of which is, independent of the other in terms of data transfer., , 40
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Unit – I Fundamentals of Data Communication and Computer Network, , Wide Area Network (WAN) :WAN is the acronym for, Wide Area Network and refers to a network used, to connect different equipment's from remote areas. Typically a WAN consists of a, series of switching devices interconnected. A WAN is also a remote access network, , that connects “sites” across a large geographic area. Wide Area Networks (WANs), connect larger geographic area, such as New York, Canada, or the world. The, geographical limit of WAN is unlimited. Dedicated transoceanic cabling or satellite, , uplinks may be used to connect this type of network. Hence, a WAN may be defined, as a data communications network that covers a relatively broad geographic area to, connect LANs together between different cities with the help of transmission facilities, , provided by common carriers, such as telephone companies. WAN technologies, function at the lower three layers., 41
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Unit – I Fundamentals of Data Communication and Computer Network, There are a large number of transmission services used to support WAN, communications, all of them using hardware components that connect to different, LANs. For connected users, all those services and components work together (a WAN, system) to create the illusion of an extensive virtual network (the WAN cloud). The, objective of a WAN is to allow access to critical data and applications to users located, in other parts of a city or other cities, even abroad. LAN interconnection is needed to, achieve more efficient communications between dispersed users, as well as to achieve, higher bandwidth for image and video applications. All this is to be achieved with, proper administration and cost control, as well as allowing adequate growth or, expansion., , 42
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Unit – I Fundamentals of Data Communication and Computer Network, WAN is composed of a number of autonomous computers that are distributed, over a large geographical area. WAN must be scalable to long distances and many, , computers. A wide area network (WAN) must be installed. The communication between, different users of “WAN” is established using leased telephone lines or satellite links and, similar channels. example of WAN is an airline reservation system. Terminals are located, , all over the country through which the reservations can be made ., It is important to note here that all the terminals use the same common data, provided by the central reservation computer., , A WAN provides long distance transmission of data, voice image and, video information over large geographical areas that may comprise a country, a continent, or even the whole world., , 43
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Unit – I Fundamentals of Data Communication and Computer Network, , Difference Between LAN, MAN, and WAN :-, , 44
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Unit – I Fundamentals of Data Communication and Computer Network, Classification of Network Based on Their Component Role., , Peer to Peer Network :Figure shows the structure of peer to peer network., Peer, , Peer, , Fig. - Peer to Peer Network, , Peer, , Peer, , In peer to peer network, each computer is responsible for making its own resources, available to other computers on the network., Each computer is responsible for setting up and maintaining its own security for all, its resources., Each computer is responsible for accessing required resources using peer to peer, relationship., , 45
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Unit – I Fundamentals of Data Communication and Computer Network, Peer to Peer network is useful for a small network containing less than 10 computers, on a single LAN. Each computer maintain its own account and their security settings., In this, each computer can function as both server and client as per requirement., , Peer to peer network does not have any central controlling system called server., In this every computer is responsible for sharing its own software as well as, hardware resources., In Peer to peer network all systems are organized into the same workgroup. Also, there is no central login process., In this, every computer can restrict access to their resources by providing password, to them.., As in this peer to peer network there is no central security, the every user will have to, know the password of each user to access the other systems resources., It reduces the initial cost of installation because there is no need of expensive server, system as well as any expensive networking software. It can be created by using, windows 2000 operating system or its subsequent versions., , 46
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Unit – I Fundamentals of Data Communication and Computer Network, When to Use Peer to Peer Network : - Peer to peer network can be used in, following conditions., When network security is not an important issue., , Number of computers required in the network are less than 10., When all users are situated in the same area / room., Requirement of Future expansion is very less., , Having Less installation cost., , Advantages of Peer to Peer Network : - Peer to peer network have following, advantages., No extra investment in server hardware or software is required., Easy to administrator. Every system can perform its own administration., No specific Network operating system required, If any system in the network fails remaining network will work., Easy to setup, user can control its own resources. Also user is not dependent on other, system., , 47
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Unit – I Fundamentals of Data Communication and Computer Network, Disadvantages of Peer to Peer Network : - Peer to peer network have following, disadvantages., Individual Performance is affected., , Less Security, Backup is difficult., Users are supposed to manage their own security., , Data can not be managed in a centralized manner., Additional load on computers because of resource sharing and absence of server., , 48
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Unit – I Fundamentals of Data Communication and Computer Network, Classification of Network Based on Their Component Role., , Client Server Network :-, , Figure shows the structure of client server, , network., Server, , Fig. – Client Server Network, Client, Client, , Client, , In client server network, one powerful computer acts as server and rest of the, computers act as clients., A Client is a computer which requests the services from server. Individual, workstations in the network are clients., A Server is a powerful computer in the network that makes its resources available, and provides its services to the clients when they requests it., , 49
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Unit – I Fundamentals of Data Communication and Computer Network, In this network, LAN relationship is based on client server relationship., Client server network typically uses directory service to store information about network, and all its users., In this type of network all available network resources such as files, directories,, applications and shared devices are centrally managed, stored and then acced by clients., In this, the servers provides security and centralized administration of the entire, network., In this no client user access the services, resources of server until it gets authenticated, (permitted)., In this network, special network operating system such as Microsoft windows server, 2000 or more versions is required to be installed on server machine. And any version of, , windows operating system is installed on all clients., In this before actual data transmission takes place among server and client the process of, authentication, identification and authorization should be performed by both., 50
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Unit – I Fundamentals of Data Communication and Computer Network, Advantages of Client Server Network : More Secure Network., Better Performance, Easy Expansion., Centralized Management, Centralized Backup., Higher Reliability, Increased Speed., Single password allows access to all shared resources., Individual used don‟t have to manage all its resources., , Disadvantages of Client Server Network : Professional Administration is required., Expensive Server Hardware, Software (NOS) is required., If Server fails then entire network collapses., Installation cost is more., , Applications of Client Server Network : E-mail Clients, Web Browsers, FTP clients, 51
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Unit – I Fundamentals of Data Communication and Computer Network, Types of Servers : File Servers, Print Servers, Application Servers, Message Servers., Database Servers., , Factors Influencing the choice of Network : Need of Network Security., Is the network administration required., Is the central storage of files essential., Importance of cost effectiveness., Is Resource sharing is necessary., Requirement of Future Expansion., 52
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Unit – I Fundamentals of Data Communication and Computer Network, Network Features: File Sharing., Printer Sharing., Application Services., Remote Access., Email, Internet and Intranet., Network Security (Internal and External)., , 53
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Unit – I Fundamentals of Data Communication and Computer Network, Difference Between Peer to Peer Network and Client Server Network:-, , 54
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Unit – I Fundamentals of Data Communication and Computer Network, , 55
