OCR Computing A-Level Revision

Introduction to Networks

A network consists of two or more computing devices connected together so that they can share data and resources.

Standalone Computers

A standalone computer is not connected to any other computers.



Computers that are connected together are known as a "network".

LAN & WAN (1.5.a)

Broadly speaking, networks can be split into two categories, LAN's (computers connected to each other in a geographically small area) and WAN's (computers connected to each other over a geographically large area). An example of a LAN would be within school, or within a singe office building. An example of a WAN would be all the schools in Kent, or all the offices of an international company.

Bitrates (1.5.d)

As shown in parallel data transmission, the more lines between two computers, the more data can be transferred in a given time. The number of bits that can be transferred per second is known as the bitrate, or the baud rate. Generally speaking, the more time sensitive the information, the higher the bitrate that is required. For example, a higher bitrate is required to have a Skype video-conference than to send a document, because the Skype conversation is time sensitive, otherwise there would be delayed reactions.

Protocols (1.5.h, 1.5.i, 1.5.j)

Computing devices on a network will need to send and receive messages. (e.g. printer out of paper, web pages from the internet, etc). Therefore, when two devices want to communicate, they must agree to follow some rules about the way they will do it. These rules are known as a protocol.

Protocols are really important! In the early days of computing, people had to buy all their software and hardware from the company who manufactured their computer, because computers were not inter-compatible. However, now standard protocols are used, hardware from different companies works harmoniously. This also leads to competition, which drives down prices.

Protocols are divided into logical protocols and physical protocols.

Logical protocols relate to aspects like:

Physical protocols relate to aspects like: