By Matt Wright
A computer or computer program that manages access to a centralized resource or service in a network.
Different types of network
A LAN (Local Area Network) is a localized network, typically within a single building. Each LAN is separate from each other, and cannot reach each other except through a wider connection (like a WAN). LANs typically have a faster transfer rate and don't require any equipment that can't be purchased off a shelf. They typically have one or more routers hooked to several computers, workstations and/or servers. They can be used for anything from internet sharing in a home setting to internal company communications and resource sharing.
• Workstations can share peripheral devices like printers. This is cheaper than buying a printer for every workstations.
• Workstations do not necessarily need their own hard disk or CD-ROM drives which make them cheaper to buy than stand-alone PCs.
• User can save their work centrally on the network’s file server. This means that they can retrieve their work from any workstation on the network.
• They don’t need to go back to the same workstation all the time.
• Users can communicate with each other and transfer data between workstations very easily.
• One copy of each application package such as a word processor, spreadsheet etc. can be loaded onto the file and shared by all users.
• When a new version comes out, it only has to be loaded onto the server instead of onto every workstation.
• Special security measures are needed to stop users from using programs and data that they should not have access to;
• Networks are difficult to set up and need to be maintained by skilled technicians.
• If the file server develops a serious fault, all the users are affected, rather than just one user in the case of a stand-alone machine.
Examples of use:
- 2 or more computers connected together
- A small office
A WAN is more expensive than a LAN. It is easier to expand a LAN than a WAN. The equipment needed for a LAN is a network interface card (NIC), a switch and a hub. On the other hand, the equipment needed to connect a WAN to the Internet is a modem and a router. The modem may be a cable modem or a DSL modem that is connected to a wall jack, while the router should be configured so that it can handle the packets traveling between the WAN and the Internet.
- Messages can be sent very quickly to anyone else on the network. These messages can have pictures, sounds, or data included with them (called attachments).
- Expensive things (such as printers or phone lines to the internet) can be shared by all the computers on the network without having to buy a different peripheral for each computer.
- Everyone on the network can use the same data. This avoids problems where some users may have older information than others.
- Share information/files over a larger area
- Setting up a network can be an expensive and complicated experience. The bigger the network the more expensive it is.
- Security is a real issue when many different people have the ability to use information from other computers. Protection against hackers and viruses adds more complexity and expense.
- Once set up, maintaining a network is a full-time job which requires network supervisors and technicians to be employed.
- Information may not meet local needs or interests
- Volunerable to hackers or other outside threats
Examples of use:
A protocol is a set of rules or procedures for transmitting data between electronic devices, such as computers. In order for computers to exchange information, there must be a pre-existing agreement as to how the information will be structured and how each side will send and receive it. Without a protocol, a transmitting computer, for example, could be sending its data in 8-bit packets while the receiving computer might expect the data in 16-bit packets.
The MAC address (Media Access Control) is a hexadecimal number that is
unique to that particular device.
The MAC address is used to transmit between devices on a LAN.
If devices are going to communicate they must have a unique reference number.
It is the same principal as addressing a letter; you need to put a unique address on the front so the postman knows where to deliver it.
Within a LAN each device must have a Network Interface Card (NIC) to connect it to the network. This card will have a MAC address.
The MAC address is hard‐coded into the NIC when it is manufactured, it cannot be configured in software.