Networks

Networks

1. LAN

   • LANs are characterised by high-speed transmission over a restricted geographical area. If the LAN is too large, signals need to be boosted. A local area network is a computer network across one building or site.

2. WAN

   • While LANs operate where distances are relatively small, wide area networks (WANs) are used to link LANs that are separated by large distances that range from a few tens of metres to thousands of kilometres. The internet is the biggest example of a WAN.

3. computer networks

   • advantages
     • A network allows users to share software stored in a main system. Files can easily be shared between users over a network. Network users can communicate via email, instant messenger, and VoIP. Within networks, it is much more straightforward to backup data as it is all stored on the file server. Networks allow data to be transmitted to remote areas that are connected within local areas. Networking computers allows users to share common peripheral resources such as printers, fax machines, etc. therefore saving money.
   • disadvantages
     • Purchasing cabling to construct a network as well as the file servers can be costly. The management of a large network is complicated, which requires training, and a specialist network manager usually needs to be employed. In the event of a file server breaking down the files contained on the server become inaccessible, although email might still work if it is stored on a separate email server. The computers can still be used but are isolated. If a virus gets into the system through a network it can easily spread to other computers. There is a risk of hacking, particularly with wide area networks. Stringent security measures are required to prevent such abuse, such as a firewall.

4. Routers

   • A router receives packets of data transmitted over a network, and using their IP address, forwards them to the correct destinations over the most efficient available path.

5. Switches

   • A switch is 'smarter' than a hub and offers more bandwidth. A switch forwards data packets only to the appropriate port for the intended recipient. The switch establishes a temporary connection between the source and the destination

6. servers

   • A network server is a computer which acts as a central storage point for files and applications. Servers also act as a connection point to shared peripherals such as printers. Active components are required for all but the simplest of networks. These include: repeaters, hubs and switches.

7. Repeaters

   • Due to loss of signal strength it is often necessary to use a repeater to boost the signal. A repeater is a hardware device to link together two cable segments. The repeater amplifies the signal it receives before passing it on.

8. hubs

   • A hub is a device which allows the interconnection of a group of users. A hub will forward any packet of data it receives over one port from one station to all of the remaining ports. Hubs are used in the star topology.

9. Star topology

   • In the star topology all stations are connected to a central node, called a hub. Nearly all wired home networks use the star topology. This topology is, therefore, better understood than many other networks. The star network has a central connection point referred to as a 'hub node' that could be a device such as network hub, switch or router. The router on its own cannot be the hub node of a network. It needs to be linked to a switch although in practice they are usually in the same box.
   • Disadvantages
     • The network operation ultimately relies on the correct functioning of the central hub. So if the central hub crashes it will lead to the failure of the whole network. The use of a hub, router or switch as the central device and the additional cabling costs increase the overall cost of the network. Performance and the number of nodes which can be added depends on the capacity of the central device.
   • Advantages
     • Compared with bus topology, star topology is better in terms of performance as signals don’t necessarily get transmitted to all the workstations although performance does depend on the capacity of the central hub. The transmission medium is not shared so there can be multiple simultaneous communications. Failure of one node or link doesn’t affect the rest of the network and it is easy to detect a failure and troubleshoot it as it allows isolation of each device within the network.

10. mesh topology

    • The latest network arrangement is mesh networking. In mesh networks each node connects to at least two other nodes and can connect to every other network node. If this happens the arrangement is referred to as being 'fully connected'. A mesh network is the most expensive type of network to install.