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Note for Computer Network - CN By prakash reddy

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Unit – I Introduction: Data Communication Components, Line Configuration, Topology, Transmission Mode, Categories of Networks, ISO Reference Model–Layered Architecture, Functions of Layers, TCP/IP Reference Model. Transmission Media: Guided Media–Twisted Pair Cable, Coaxial Cable, Optical Fiber, Unguided Media– Satellite Communication, and Cellular Telephony. Multiplexing: Frequency–Division Multiplexing, Time–Division Multiplexing. Page 1 of 63

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Chapter: 1 Basic of communication Model: Communication model is used to exchange data between two parties. For example communication between a computer, server and telephone (through modem). Source: Data to be transmitted is generated by this device, example: telephone, personal computers etc. Transmitter: The data generated by the source system are not directly transmitted in the form they are generated. The transmitter transform and encodes the information (data) in such a form to produce electromagnetic waves or signals. Transmission System: A transmission System can be a signal transmission line or a complex networking connecting source and destination. Receiver: Receiver accepts the signal from the transmission system and convert it to a form which is easily managed by the destination device. Destination: Destination receives the incoming data from receivers.  Data Communication: The exchange of data between two devices through a transmission medium is data Communication. The data is exchanged in the form of 0’s and 1’s. the transmission medium used to wire cable. For data communication to occur, the communication device must be part of a communication system. Data communication has two types. They are 1. Local Communication and 2. Remote Communication 1. Local Communication: Local Communication takes place when the communication devices are in the same geographical area, same building, face to face between individuals etc. 2. Remote Communication: Remote Communication takes place over a distance i.e. the devices are remoter. Effectiveness of a Data Communication can be measured the following features: i. Delivery: delivery should be done to the correct destination. ii. Timeliness: Delivery should be on time. iii. Accuracy: Data delivered should be accurate. Page 2 of 63

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iv. Components of Data Communication following are a. Message: it is information to be delivered. b. Sender: sender is the person who is sending the message. c. Receiver: Receiver is the person to him the message is to be delivered. d. Medium: it is the medium through which message is to be sent for example Modem. e. Protocol: these are some set of rules which run data communication. NETWORK TOPOLOGY Network topology is the schematic description of a network argument, connecting various nodes(sender and receivers) through lines of communications. They are different types of network topologies. They are 1. 2. 3. 4. 5. 6. BUS TOPOLOGY RING TOPOLOGY STAR TOPOLOGY MESH TOPOLOGY TREE TOPOLOGY HYBRID TOPOLOGY 1. BUS TOPOLOGY: Bus Topology is a network type in which every computer and network device is connected to single cable. When it has exactly two endpoints, then it is called Linear BUS Topology. Features of BUS Topology: 1. It transmits data only in one direction. 2. Every device is connected to a single cable. Advantages of BUS Topology: 1. 2. 3. 4. 5. It is cost effective. Cable required is latest compared to other network topology. Used in small networks. It is easy to understand. Easy to expand joining two cables together. Disadvantages of BUS Topology: 1. Cable fails then whole network fails. 2. If network traffic is heavy or nodes are more performance of the network decreases. 3. Cable has limited length 4. It is slower than the other network topology. 2. RING TOLOPOGY: It is called Ring Topology because it forms a ring as each computer is connected to another computer, with last one connected to the first. Exactly two neighbors for each device. Page 3 of 63

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Features of RING Topology: 1. A number of repeaters are used for RING Topology with large number of Nodes, because if someone wants to send some data to the last Node in the RING Topology with 100 Nodes, then the data will have to pass through 99 Nodes to reach the 100th Node. Hence to prevent data loss repeaters are used in the networks. 2. The transmission is unidirectional, but it can be made bidirectional by having 2 connection between each network Node, it is called Dual Ring Topology. 3. In Dual Ring Topology, two ring networks are formed, and data flow is in opposite direction in them, also, if one ring fails, the second ring network can act as a backup, to keep the network up. 4. Data is transferred in a sequential manner that is bit by bit. Data transmitted, has to pass through each node of the network, till the destination node. Advantages of RING Topology: 1. Transmitting network is not affected by high traffic or by adding more Nodes, as only the nodes having tokens can transmit data. 2. Cheap to install and expand. Disadvantages of BUS Topology: 1. Troubleshooting is difficult in RING Topology 2. Adding or deleting the computers disturbs the network activity. 3. Failure of one computer the disturb the whole network. 3. STAR TOLOPOGY: In this type of Topology all the computers are connected to a single hub through a cable. This hub is the central Node and all other Nodes are connected to the central Node. Page 4 of 63

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