NETWORKING

Local Area Network.

This is the connection of two or more PC?s and other devices which allow them to share software, hardware, data and communication services. The devices are confined to a small geographical area. The distance that a LAN spans depends on specific implementations. A LAN covers a clearly defined local area such as a office suite, a building, or a group of buildings.

Benefits.

1. Sharing of software.

2. Sharing of data.

3. Sharing system resources.

4. Security and backups.

5. Easier maintenance and upgrades.

A LAN can provide office workers with the following benefits:

· Memo and document distribution to recipients using electronic mail.

· Scheduling of meetings.

· Down-loading or building machines with software from the server, a universal set-up.

· Multiple user access to printers, plotters, facsimile machines, CD Drives and scanners.

· Backup of documents on a global scale.

· Security of file access.

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LAN Characteristics.

· Flexibility. To be able to add or remove devices without complication.

· Speed. High data transfer, the costs increase as you increase the speed.

· Reliability. Minimal down time and it should be able to recover from a system failure without losing jobs or files located on the server.

· Hardware and Software sharing. Multiple users accessing individual devices is cheaper than multiple devices accessing single users.

· Transparent Interface. The appearance of operations should not differ between a LAN or a stand alone.

· Adaptability. Must allow for ease of growth and be easily adapted to new configurations.

· Security. Against hackers, viruses and allowing hardware connections only to relevant users.

· Centralised Management. An administrator should be able to perform backups of the entire system from a centralised station. They also should monitor performance and use of the LAN.

LAN Components.

Two major items must be considered when planning or installing a LAN and they are network hardware components and the network software.

Three major categories of devices make up the hardware components of a local area network and these are the server, the LAN communication system, and the work-stations.

Servers are computers on the network that are accessible to the users of the network. It usually is a standard computer with large hard drives which stores network software, Application software and data files.

LAN Communication System.

To connect two or more computers on a network the following is necessary:

1. Cable.

2. Network Interface Card or NIC.

The cable is used to connect each PC using the network card placed in each machine. Connections can be made through serial ports however the transmission rate is a great deal slower.

LAN Software.

The processes that take place on the hardware devices of a LAN must be controlled by software. The software is the Network Operating System.

The NOS controls the operation of the file server, and it makes the network resources accessible. It manages security and provides administrators with the tools to control user access and to manage the file structure of the network disks.

It is an extension of the PC,s operating system but handles the functions on offer at a larger scale.

Bandwidth.

How much the capacity is of data the network can transmit.

Two Types:

1. Broadband is the same method used in telephone lines (Analogue Signals). It can also share the lines with video and facsimile transmissions. Extra equipment is needed for the translation from digital to analogue and then back to digital.

2. Baseband is the method of transmitting data, one way, in its own digital format. Advantages are lower in cost, easier to install and less maintenance.

Topology.

The organisation of the equipment on the LAN. There are three basic structures. They are the Star, Bus and Ring.

1. The Star Topology each terminal has a point to point connection with the file server. The server will ever send information back or direct it to its location. So this means all data must pass through the server. Problems are if server goes down, no one can communicate.

2. A Bus Topology is a single length of cable which terminals are connected to. The cable may be extended but only at the ends. If another cable is connected to it and extends to another end it is known as a tree. This network is the most used in America.

3. A Ring Topology is each terminal is connected to the next until the end returns to the beginning. The signal must pass through each PC until it returns back to the original PC. This network is mostly used in Europe.

General Installation of a LAN.

Once the software, type of topology is chosen and the network distributions designed installation is the next step. The type and amount of personnel required for the installation of the LAN depends on the size, type, and scope of the LAN. But all LANs share the same common characteristics:

· The use of a personal computer as a basic client.

· The use of one or more fast computers as dedicated servers.

· All PC,s require interface cards.

· All hardware in the LAN needs to be protected.

· A profile or structure of the network needs to be created and maintained. View of the LAN

· All users login onto the network.

· Copyright laws with software have to be checked.