Introduction to LAN (Local Area Network)
A group of computers and other devices dispersed over a relatively limited area and connected by a communications link that enables any device to interact with any other on the network. LANs commonly include microcomputers and shared (often expensive) resource such as laser printer and large hard disk. Most (modern) LANs can support a wide variety of computer and other devices. Each device must use the proper physical and data-link protocols for the particular LAN, and all devices that want to communicate with each other on the LAN must use the same up-level communications protocol. Although single LANs are geographically limited (to a department or to an office building, for example), separate LANs can be connected to form larger networks. Similarly LANs are linked by bridges, which act as transfer points between networks; dissimilar LANs are linked by gateways, which both transfer data and convert it according to the protocols used by the receiving network.
The devices on a LAN are known as nodes, and the nodes are connected by cabling through which messages are transmitted. Types of cable include twisted-pair wiring, coaxial cable, and fiber-optic (light-transmitting) cable. Nodes on a LAN can be wired together in any of three basic topologies, known as bus, ring, and star. As implied by their names, a bus network is more or less linear, a ring network forms a loop, and a star network radiate from a central hub.
To avoid potential collisions when two or more nodes attempt to transmit at the same time, LANs use either contention or collision detection or token passing to regulate traffic.
Local Area Network Applications:
- Data Processing
- Data entry
- Transaction processing
- File transfer
- Inquiry / response
- Batch / RJE
- Office Automation
- Document / word processing
- Electronic mail
- Intelligent copying / facsimile
- Factor / automation
- CAD / CAM
- Inventory control / order entry / shipping
- Monitor and control of factory floor equipment
- Energy management
- Heating
- Ventilation
- Air conditioning
- Process control
- Fire and security
- Sensors / alarms
- Cameras and monitors
- Telephones
- Teleconferencing
- Television
- Off-the-air
- Video presentation
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