Yr12ITGS-Network+Components2010

=__**NETWORK COMPONENTS**__=

 **Router -** a device that transfers data from one network to another in an intelligent way. It has the task of forwarding data packets to their destination by the most efficient route. It can also:
 * Exchange Protocol information across networks
 * Filter traffic - useful for preventing hacker attacks for example

Each type of network cable has a maximum usable length. If you go beyond that length, the signal will be too weak to be useful. Of course, computers on a real network can easily be more than 200 meters apart. Therefore the network cable is split up into segments. Each segment is less than the maximum length allowed. Joining the segments together is a device known as a 'Repeater'.
 * Repeaters-**  All signals fade as they travel from one place to another.


 * Readers-** does just what you would expect it to do - it joins two networks together so as far as data packets are concerned it looks like one large network


 * Bridges-** does just what you would expect it to do - it joins two networks together so as far as data packets are concerned it looks like one large network. It is not as capable as a Router.


 * Hub-** Depending on the network Topology (Bus, Ring, Star, or Tree) each computer must be able to send data packets to any other computer on the network.


 * Switches-** has number of ports that stores all device addresses directly or indirectly to each port. When a data packet comes to the switch, the destination address is examined then is directly connected to the machine or device it needs to connect to.


 * Protocols-**  an agreed method of doing something. If your network is to be kept secure it is often essential that some filtering takes place.


 * Gateways-** a mixture of hardware and software components, which converts data passing between dissimilar networks so that each side can communicate with each other. i.e converts data into the correct network protocol.


 * Filters-** It is also a mixture of hardware and software components, however unlike gateways, filters are set up to block unwanted packets trying to come in.


 * Servers-** a resource that another machine needs to use.


 * E.g. are Printer servers
 * File Servers
 * Database Servers
 * E-mail servers
 * Internet Proxy Server
 * Intranet Server


 * Proxy Servers-** (another word for substitute) It's main tasks is to supply authorized internal users with web pages and to Supply external users with authorized information and services. It also acts as a filter that Prevents unauthorized users from accessing external networks such as the internet, prevents unauthorized web sites to be accessed (stops time wasting!), and Provides a web service to external clients, but does not allow them through to the internal network itself. For example a bank web site would be running a proxy service.

Standard modems come in two forms. An external box that links to your computer either through a serial or USB port, or an internal modem that is plugged directly to the motherboard inside the computer.
 * Modems-** <span style="font-family: arial,Arial,Helvetica;">or MODulation - DEModulation box. It converts digital data from the computer into a continuous analogue wave form that the telephone system is designed to deal with (MODulation). The reason for this is that the telephone system was originally designed for the human voice i.e. continuous signals. The modem also converts the analogue signal from the telephone network back into digital data that the computer can understand. (DEModulation).


 * Network Cards-** <span style="font-family: arial,Arial,Helvetica; font-size: 11pt;">required in every machine connected to the network. They allow the signal from the network to be transmitted to the machine – this could be via a fixed cable, infra red or radio waves.


 * Cables-** The three main ways transferring data is through Electrical, Radio/Microwave and Infrared cabling.