A hub is a device that connects a number of computers together to make a LAN.
The typical use of a hub is at the centre of a star network (or as part of a hybrid network) - the hub has cables plugged into it from each computer.
A hub is a ‘dumb’ device: if it receives a message, it sends it to every computer on the network. This means that hub-based networks are not very secure - everyone can listen in to communications.
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Router
A router is a network device that connects together two or more networks.
A common use of a router is to join a home or business network (LAN) to the Internet (WAN).
The router will typically have the Internet cable plugged into it, as well as a cable, or cables to computers on the LAN.
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Implementing the system
Implementation is the next stage of developing a new system, after design. This is where the new system is installed, including:
• writing programs purchasing hardware and software
• writing user documentation testing the system using the test plan
• installing networks training staff
If the tests are not satisfactory then any problems will need to be corrected and the system tested again. User documentation will be written to help staff become familiar with the new system. It will include:
• a user guide installation details
• input and output samples screen shots
• error messages (troubleshooting)
When the system is ready to go on-line there are different ways of changing to the new system:
• Parallel running - running both the old and new system until you are certain the new system is working correctly. Parallel running is likely to be the most expensive as it involves doing the work twice for a period of time. However, it is the safest. If there are any bugs in the new system, you can always go back to the old system while the problems are corrected.
• Pilot changeover - changing over in a small part of the company to start with. Only when the system is deemed satisfactory will it be rolled out to the rest of the organisation. A supermarket introducing a new 'self-scanning' system might choose to introduce it in two or three stores at first. This is a pilot changeover.
• Direct changeover - the old system is scrapped and immediately replaced by the new system. With this option there is a danger that there may still be problems with the new system. Even though it is the most risky type of changeover, many companies use this method.
(Taken from external notes!)