1. CHAPTER - 4 COMPUTER NETWORK Dr. BALAMURUGAN MUTHURAMAN 12015-2016

2. INTRODUCTION OF NETWORK A Computer Network may be defined as an interconnection of two or more autonomous computers. Two computers are said to be interconnected if they can share or exchange information. In a computer network each computer operates independently on separate tasks. Each computer is a complete unit itself with its own CPU, memory and other peripheral devices. 22015-2016

3. LAN, MAN & WAN  Network in small geographical Area (Room, Building or a Campus) is called LAN (Local Area Network)  Network in a City is call MAN (Metropolitan Area Network)  Network spread geographically (Country or across Globe) is called WAN (Wide Area Network) 32015-2016

4. TYPICALLY NETWORKS COMPONENTS  In a client/server network arrangement, network services are located in a dedicated computer whose only function is to respond to the requests of clients.  The server contains the file, print, application, security, and other services in a central computer that is continuously available to respond to client requests. 42015-2016

5. ADVANTAGES OF CLIENT-SERVER NETWORK  Very secure  Better performance  Centralized backup  Very reliable DISADVANTAGES OF CLIENT-SERVER NETWORK  Requires professional administration  More hardware-intensive  More software intensive  Expensive dedicated software 52015-2016

6. ADVANTAGES OF NETWORKS Data Sharing : Data sharing is one of the biggest advantages provided by the computer networks. All the data and resources like documents, files, accounts information, reports, multi media etc. can be shared with the help of computer networks. Hardware sharing and application sharing is also allowed in many organizations such as banks and small firms. 62015-2016

7. Instant and Multiple Accesses : Computer Networks are multiply processed, many of users can access the same information at the same time. Immediate commands such as printing commands can be made with the help of computer networks. High Reliability : High reliability is achieved by replicating important data or files on two or three machines. This cause that if one of machines goes down, the user can still access the data through some other machines on the network. 72015-2016

8. Video Conferencing : Before the arrival of the computer networks there was no concept for the video conferencing. LAN and WAN have made it possible for the organizations and business sectors to call the live video conferencing for important discussions and meeting. Internet Service : Computer networks provide internet service over the entire network. Every single computer attached to the network can experience the high speed internet, fast processing and work load distribution. 82015-2016

9. COMPUTER NETWORKING DEVICES Computer networking devices are units the mediate data in a computer networks. These are also called networks equipment, Intermediate System (IS) or Inter Working Unit (IWU). Units which are the last receiver or generate data are called hosts or data terminal equipment. Computer networking devices also known as communication devices and they constitute a data communication network. 92015-2016

10. BASIC COMPUTER NETWORKING DEVICES 1.Router 2.Network Switch 3.Modem 4.Firewall 5.Proxy Server 102015-2016

11. ROUTER A router is communication device that is used to connect two logically and physically different networks, two LANs, two WANs, and a LAN with WAN. The main function of the router is to sorting and the distribution of the data packets to their destination based on their IP addresses. Routers provide the connectivity between the enterprise business, ISPs and in the internet infrastructure, router is a main device. 112015-2016

12. NETWORK SWITCH A network switch or switching hub is a computer networking devices that connects network segments. The term commonly refers to a multi-port network bridge that processes and routes data at the data link layer of the OSI (Open System Interconnection) model. 122015-2016

13. MODEM A modem (modulator-demodulator) is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. Modems can be used over any means of transmitting analog signals, From light emitting diodes to radio. 132015-2016

14. FIREWALL The term firewall originally referred to a wall intended to confine a fire or potential fire within a building. A firewall is a device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass. Many personal computer operating systems include software-based firewalls to protect against threats from the public Internet. 142015-2016

15. PROXY SERVER In computer networks, a proxy server is a server (a computer system or an application) that acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource, available from a different server. The proxy server evaluates the request according to its filtering rules. 152015-2016