Transfer of Data

Transfer of Data

1. A network is a collection of connected computer systems (PC's, laptop's, printer's, server's etc.)

   • Client-Server Network
     • A Network of PCs (clients) and Servers that have specialised jobs such as managing emails or My Documents folders.
       • Benefits
         • Users can connect to their accounts from any computer.
         • Software can be installed just once.
         • Easy to backup from 1 server instead of 100 PCs.
       • Limitations
         • If lots of data is being sent to/from the servers (e.g. streaming video or playing games) then the network can slow down for all users.
         • Servers are expensive to buy/run.
       • Example
         • Large organisations like schools, hospitals, banks etc.
   • Peer-To-Peer
     • A simple network where every computer is connected to each other computer.
       • Benefits
         • If any part of the network breaks, the rest will continue to function.
         • Simple for home users to set up.
       • Limitations
         • Software must be installed on every PC individually.
         • Users can only log onto computers they are set up on.
       • Example
         • Small networks like retail shops or home users.

2. Communication Devices

   • Network Interface Card
     • Prepares data for sending over the network, sends the data and controls the flow of data from the computer terminal to the transmission medium (wired or wireless).
   • Hub
     • Used to join computers in a network, allows the sharing of files and Internet access
     • NB: now obsolete – replaced by switches.
   • Switches
     • Similar device to a hub but more intelligent - can look at a packet of data to decide where it should go.
   • Router
     • Can be wired or wireless, is used to join several networks together, often used to connect several computers in the home to the Internet.

3. Data Transfer Media

   • Metal Wires (UTP vs STP)
     • Ethernet cables – used in wired networks, high transmission speeds, expensive to install.
     • Unshielded or Shielded twisted pair varieties.
   • Fibre Optic Cables
     • Data is passed in pulses of light, so very fast.
     • Expensive so mainly used to connect different locations – same site or between sites/countries.
   • Wireless
     • Uses radio waves travelling through the air – so no cables required.

4. Network Topologies

   • Ring
     • Easy to add devices (P2P).
     • Equal access for all connected devices.
     • If break in cable then whole network fails.
   • Bus
     • Cost effective – small amount of cable; easy to install.
     • Limited number of devices; if backbone cable fails network can’t be used.
   • Star
     • Fault tolerant, easy to add additional computers.
     • Expensive because of cabling required, if central point fails, whole network will fail.
   • Mesh
     • Fault tolerant, often used to create a wireless network.
     • Higher cost – requires lost of cable runs.

5. WWW and Intranet

   • Intranet
     • A private computer network restricted to a small geographic location.
     • The FitzWimarc Intranet of web pages (SharePoint) with information for students/teachers.
   • Extranet
     • An Intranet made partially available to people outside the organisation’s building.
     • FitzWimarc’s Intranet is accessible to students from home (email & docs).
   • Standards and Protocols
     • Rules that tell computers in networks how to communicate together.
       • Benefits
         • You are not restricted to only buying hardware/software made by whoever made your computer system.
         • You can transfer data between different types of system easily (e.g. between PC and Mac or Mobile).
     • A common way of doing something, for example, storing data in a particular format or transferring data in a predetermined way.
       • Limitations
         • They are difficult to change because everyone has to follow exactly the same standards and protocols – and update all at the same time. So it can take time for everyone to update to the latest standards needed for the latest hardware.

6. Networks

   • Benefits
     • Ability to share files
     • Ability to share hardware resources
     • Ability to share software
     • Lower software costs
     • Improved security
     • Easier to implement acceptable use policies
     • Easier to back up files
     • Improved communication
     • Central maintenance and support
   • Limitations
     • Technical knowledge needed
     • Lack of access when file server fails
     • Cost