Local area networks (LANs) are computer networks that cover a small area such as a home, school, office or small group of buildings. Local area networks have a high-transfer rate, a smaller geographic range and don’t need leased communication lines as much. Wide area networks are computer networks that cover a much larger area compared to a LAN such as metropolitan, regional or national boundaries. An example of a WAN is the internet which is the largest and most well known.
What is needed to make a Local area network or Wide area network?
File servers, workstations, network interface cards, hubs, switches, repeaters, bridges, routers and gateways would all be needed for a LANs and WANs, but in LANs, routers would not be used.
File servers will stand at the heart of most networks and is a very fast computer with a very large amount of RAM, storage space and has a fast network interface card. The network operating system software resides on this computer along with any software and data that would need to be shared. The server will control the communication of information between the nodes on a network such as when it might be asked to send a word processor programme to one of the workstations, receive a database file from another workstation and store e-mail messages during the same time. This all requires a computer that can store a lot of information and share it very quickly.
Workstations are the user computers that are connected into a network. A normal workstation is a computer that is configured with a network interface card, networking software and the proper cables. The workstations do not necessarily need floppy disk drives because files can be saved on the networks file server. Almost any computer can serve as a workstation in a network.
Network interface cards provide the physical connection between the network and the computer workstation. Most network interface cards are internal with the card having been fitted into a expansion slot inside the PC. Laptops can be bought with a NIC built in or with network cards that slot into a PCMCIA slot. The network interface card is a major factor in finding out the speed and performance of a network. It is a good idea to use the fastest network card available for the type if workstation you have. A NIC would now come with speeds from 10 Mbps to 1000 Mbps or 1 Gbps. The most common NICs are Ethernet cards and token ring cards. Ethernet would be the most popular method, although wireless access is now common.
Hubs are devices that connect twisted pair or fibre optic Ethernet devices together. Hubs would work at the physical part of a network. Hubs may be active or passive, an active hub regenerates signals and passes them along (also called a mulitport repeater) and a passive hub is simply a central connection point with no amplification or regeneration of the data being transmitted. Hybrid hubs will maximize networks efficiency by interconnecting different types of cables and topologies. Hubs today are no longer used, switches would be used instead.
A switch determine destinations of messages and sends it only to the destination port, it provides full bandwidth to each station on a network. Switches will also handle several conversations on a network at one time. Switches used to be more expensive than hubs but you can’t buy hubs anymore because switches provide for better performance and would be the device of choice for many technicians.
Since signals will lose their strength as it passes along a cable if would be necessary to boost the signal with a device called a repeater. A repeater will electrically amplify the signal it receives and will rebroadcast it. Repeaters can be separate devices or they can be incorporated into a switch or hub. They would be used when the total length of your network cable exceeds the standards that are set for the type of cable being used.
A bridge is a device that will take a large LAN a segment it into two smaller, more efficient networks. A bridge will monitor the information traffic on both sides of the network so it can pass packets of information to the correct location. Most bridges can “listen” to the network and figure out the address of each computer on both sides of the bridge automatically. The bridge can look at each message and, if it necessary, broadcast it on both sides of the network. The bridge manages the traffic to keep optimum performance on each side of the network. It works as if it is a traffic policeman at a busy crossroads, it keeps information flowing on both sides of the network but it will not allow unnecessary traffic through. Bridge can be used to connect different types of cabling or physical topologies, but bridges must be used between networks with the same protocol.
A router will connect different types of networks together and is typically used for wide area networks (WANs). Routers use IP addresses and select the best path to route a message, based on the destination’s address and where it is located. A router can direct traffic to prevent collisions and is smart enough to know when the traffic will be needed to be directed along back roads and shortcuts. While bridges know the MAC addresses of all computers on each side of a network, the routers will know the IP addresses of computers, bridges and any other routers on the network. Routers can even listen top all the traffic on a network and determine which parts are the busiest and redirect the traffic away from the busiest paths until they become cleared so that traffic can use those routes again. If you only have one single computer on a local area network that you want connected to the internet you will need a router. In this case the router will act as a translator between the information on your computer/LAN and the internet and will also determine the best route for the data to be sent over. A router can direct signal traffic efficiently, route messages between any two protocols, route messages between linear bus, star and star-wired topologies, route messages across fibre optic, coaxial and twisted-pair cabling.
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