25-08-2017, 09:32 PM
INTRODUCTION TO COMPUTER NETWORKS
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Computer Networks
A network consists of two or more computers that are linked in order to share resources (such as printers and CDs), exchange files, or allow electronic
communications.
The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.
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)
Applications of Networks
Resource Sharing
Hardware (computing resources, disks, printers)
Software (application software)
Information Sharing
Easy accessibility from anywhere (files, databases)
Search Capability (WWW)
Communication
Message broadcast
Remote computing
Distributed processing (GRID Computing)
Network Topology
The network topology defines the way in which computers, printers, and other devices are connected. A network topology describes the layout of the wire and devices as well as the paths used by data transmissions.
Bus Topology
Commonly referred to as a linear bus, all the devices on a bus topology are connected by one single cable.
Bus: Stations attach to transmission medium or bus
At each end of the bus there is a terminator which absorbs the signal energy
Star & Tree Topology
The star topology is the most commonly used architecture in Ethernet LANs.
When installed, the star topology resembles spokes in a bicycle wheel.
Larger networks use the extended star topology also called tree topology. When used with network devices that filter frames or packets, like bridges, switches, and routers, this topology significantly reduces the traffic on the wires by sending packets only to the wires of the destination host.
Computers: Clients and Servers
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.