The purpose of a network is to transmit information from one computer to another. To do this, you first have to decide how to encode the data to be sent, in other words its computer representation. This will differ according to the type of data, which could be:
- Audio data
- Text data
- Graphical data
- Video data
Data representation can be divided into two categories:
- Digital representation: which means that the information is encoded as a set of binary values, in other words a sequence of 0s and 1s
- Analogue representation: which means that the data will be represented by the variation in a continuous physical quantity
Data transmission medium
In order for data transmission to occur, there must be a transmission line, also called transmission channel or channel, between the two machines.
These transmission channels are made up of several segments that allow the data to circulate in the form of electromagnetic, electrical, light or even acoustic waves. So, in fact, it is a vibratory phenomenon that is propagated over the physical medium.
Encoding of transmission signals
In order for data to be exchanged, an encoding must be chosen for the transmission signals. This depends basically on the physical medium used to transfer the data, the guaranteed data integrity and transmission speed.
Simultaneous data transmission
Data transmission is called "simple" if there are only two machines communicating, or if only a single piece of data is sent. Otherwise, it is necessary to install several transmission lines or to share the line among several different communication actors. This sharing is called multiplexing.
A protocol is a common language used by all actors in the communication to exchange data. However, its role does not stop there. A protocol also allows:
- Initiation of communications
- Data exchange
- Error detection
- A "courteous" end of communications