Local Area Networks

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Local Area Networks

• Why we use them
• How they work
• What you need to build one
• Managing Them
• Security

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DEFINITION

• A Local Area Network is defined as a system of
  interconnecting PCs and other devices within a
  small area, typically a few hundred metres.

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The Advantages of a LAN

• It allows sharing of Data
• It avoids duplication of Data
• It distributes the processing tasks
• It can reduce software costs
• It allows sharing of expensive peripherals
• It allows communications between users
• It allows users to share a gateway

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A Multi User System
Main Frame or Mini
Printer
Dumb Terminals
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A Typical PC Network
File Server
Printer
Print Server
Work Stations
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Networks

• Have a Topology
• The way they are wired together
• A Communicating Method
• The way signals are passed around the network

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Network Topology
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Multiple Access Units (MAUs)
Multiple Access Unit
Ring
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Types of LAN Communications

• Polling
• Carrier Sense Multiple Access
• With Collision Detection
• With Collision Avoidance
• Token Ring

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Peer to Peer Networks

• each work station is the same as every other
• each can access the others facilities
• Hard disks, Printers
• suitable for 2 or 3 work stations

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Non Dedicated File Server

• One machine handles all the files
• It also acts as a work station
• Only suitable for very small networks
• Is very slow as a work station

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Dedicated File Server

• Most common type of network
• One powerful PC is dedicated to supplying the
  needs of the users
• It has no other function
• Can handle up to 100 users

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What do you need ?

• A File Server
• Work Stations
• Network Cards
• Cabling
• Software to run the Network
• A Person to manage it

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File Server

• Powerful PC (Pentium)
• Lots of RAM (16Mb )
• A Large Hard Disk (1 Giga Byte )
• A Network Card
• Backup Tape Drive
• Installed Network software

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Work Stations

• Normal PCs
• Disk Drives not essential
• Network Cards
• Installed Network software

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Cabling

• Twisted Pair
• Up to 4M Bits/Sec
• Coaxial Cable (thin ethernet)
• Up to 50M Bits/Sec
• Fibre Optic
• Uses light to transmit signal
• 100 M Bits/Sec upwards

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Software

• Peer to Peer
• Windows for Work Groups
• Windows 95
• Novell Netware Lite
• Server type
• Windows NT
• Novell Netware

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Network Managers

• On Peer to Peer
• D.I.Y.
• On Small Server networks
• Part time by an existing employee
• Large Networks
• Run by qualified person
• Run by IT department

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Security Aspects

• Password Controls
• Different Access levels
• Backup Systems
• Automatic backup to tape
• Usually overnight