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Class Notes Class: XII Date: 04-11-
Subject: Informatics Practices
Topic: Chapter 9. Introduction to Computer Network
Computer Network : A Computer Network is a collection of interconected autonomous computing devices so as to exchange
information or share resources. You can connect your computer to your cellphone, printer or any other music system to share
the data among the devices.
Advantages of Computer Network:
- It is used to share resources.
- It can also share the storage.
- Software can be shared among the users.
- Internet is widely used for communication. Disadvantages:
- Trained person/staff is needed to run the internet-based applications.
- If network bandwidth is low, it becomes unusable and difficult to perform the job.
- If the server fails, it is difficult to get the data from server.
- Computer viruses are spread through internet if proper precaution is not taken.
Components of a computer network:
The major components of a Computer Networks are:
a. Host/Nodes b. Servers c. Clients d. Network Hardware e. Communication Channel f. Software g. Network Services
Types of Computer Network:
a. LAN – Local Area Network which are confined to a localized are like building, an office or a factory etc. The key purpose of LAN is resource sharing. b. WAN – Wide Area Network spreads across countries and cover a very big geographical area. It can be a group of LANs. The Wans link computers tofacilitate fast and efficient exchange of information. c. MAN- Metropolitan Area Network is a type of network which covers an area as big as a city. d. PAN – Personel Area Network is the interconnection IT devices within the range of an individual person, typically within the range of 10 meters.
Network Topologies : The pattern of inter connection of computers in a network is called Network Topology. There are a
number of factors to consider a topology. These are:
- Cost: - For a network to be cost effective, one would try to minimize installation cost.
- Flexibility: The topology should allow reconfiguration of the network with flexibility.
- Reliability: The topology chosen for the network can help by allowing the location of the fault to be detected and to provide the better network.
Types of Topologies:
- Star Topology: All the computers are connected to a central Node using a single path.
Advantages of Star Topology: a. Easy access for service or reconfiguration of the network. b. One device per connection, failure of single connection involves disconnecting the nodes from the network. c. Centralized control – Central node is connected directly to every node in the network means faults are easily detected and corrected in the network. d. Simple access Protocols: In Star network access protocols are very simple.
Disadvantages of Star Topology:
a. As each node is connected directly with the central node it requires separate network cable for the connection thus long cable length is required. b. Star topology network is difficult to expand. c. It is central node dependency.
- Bus Topology : This consists of a single length of the transmission medium on to which various nodes are attached. The topology is used in traditional communication network where the host at one end of the bus communicates with several terminals attached along its length.
Advantages: a. Short cable length is needed. b. Resilient Architecture. c. Easy to extend.
- External Modem: This modem is connected externally to a computer.
B. HUB: A hub is a network device having multiple ports that are used for connecting multiple computers or segments of a LAN together.
A hub contains multiple independent but connected modules of network and inter-networked equipment. Hubs can be either passive or active. Active hub electrically amplify the signal as it moves from one connected device to another whereas passive hub allow the signal to pass from one computer to another without any change.
Switch : A switch is used to segment networks into different subnetwork called subnets or LAN segments. Segmenting the network prevents the traffic overloading in a network.
The Function of a switch : To insulate the transmission from the other ports, the switch establishes a temporary connection between the source and destination, and then terminates the connection once the conversation is done.
Repeater: A repeater is a device that amplifies a signal being transmitted on the network. It is used in long
network lines. Because over distance, the cable connecting a network lose the signal transmitted. In this case repeaters are installed along the way to ensure that data packets reach their destination.
Bridge: A bridge is a device that lets you link two networks together having the same protocols.
Router: It looks like a bridge but it can handle different protocols, a router can link ethernet to a mainframe.
