Media communication is the process in which data is transferred from one computer to another. This involves transmission of digital of information to different devices through wireless or cabled connections.
The data transmitted over networks could be either digital or analog. * Analog signals are continuous signals that vary in strength. Sound is an example of an analog signal. Telephones have transmitters that encode sound waves into electromagnetic waves, which then travel over wires toward their destination. The receiving telephone decodes the electromagnetic waves back into sound waves. Our brains then decode the sound waves into the words we hear. Computer modems use the same principle. Analog signals can be represented digitally. For instance, a high electromagnetic voltage could be interpreted as 1 and low voltage as 0. * Digital signals are discrete rather than continuous. Either there is a signal or there isn't a signal. Telegraphs transmit data with discrete signals. You either hear a tap or you do not hear a tap. Discrete signals can be represented by on and off pulses. The duration of a discrete signal can be varied, as with dots and dashes in Morse Code.
To explain how this data is transmitted over the network, first I had to explain the mediums. Mediums are ways, which the data use to travel from one place to another. These mediums may vary depending the environment or type of network.
The most commonly used data communication media include: * Wire pairs (lan cable) or Coaxial cable * Microwave transmission or Communication satellites * Fiber optics

Wire pair or coaxial cable characteristics are: * The use electrical pulses to communicate. * The cover distances up to 500 meters. * Maximum rate of communication of 100MB/s. * It can transmit l a low rate of errors (except if it is induced by an external source of electricity). * The cost is low. * The transmission has moderate secure.

The transmission of data through this medium is commonly used on big buildings. Computers can be interconnected to share files and devices in a network by means of cabling which facilitates faster communication of information.

Microwave transmission or satellite characteristics are: * Signals travel as waves of varying lengths and frequencies. * Needs a direct point of sight * Depending of the environment the cost could be low or moderate. * High rate of error * The maximum possible rate is 1 Gb/s. * Less secure medium. * Can be affected by rain or clouds. * It could transmit up to 300 meters * The signals suffer delays on long distances over satellites.

This medium is used on small networks or home networks. Also the use of satellite is of common use over cell phones, TV and remote places where other mediums are not possible to go.

Fiber characteristics are: * Can cover over 600 miles * Use light or laser to transmit the data. * Has the lowest rate of errors. * Can transmit up to 40GB/s. * It is the most secure medium. * It is very expensive. * The medium is very fragile.

This medium is mostly used on big cities, large technological companies, data centers and countries overseas by submarine cables. It is used to transmit video, data and voice at the same time over the same line.

Now that I explain the mediums and know that the data can be transferred analog or digital, we can learn how this works over the OSI model.

Lets transfer the letter A over the layers. The first layer or application is the interface used by the client. It provides the user with the necessary programs to write the letter A. After this we can find the presentation layer which formats the data to be display to the user, in this case is the one that will give format to the letter A. The next layer is the session layer. It handles problems, which are not communication issues. After that layer came the transport layer, which Provides end-to-end communication control. The network layer is the one performs routing. It determines the next computer the message should be sent to so it can follow the best route through the network and finds the full address for that computer if needed. It will tell the letter A where to go and how. The data link layer provides error control; it will make sure the letter A has no errors at the time of its journey. And at the end we find the physical layer, which will take the latter A and will encapsulate it into a digital signal to travel over the network.
The mediums previously mentioned were the data is transmitted are determinate in the physical layer, depending the topology that the network is working. The physical layer has the necessary circuits to encode the data and determinate if the data will be transferred over electrical pulses, waves of wireless signals or specters of light. Thanks to these circuits, analog transmission, can be change to digital signals to travel over the network and when it arrives its destination it will be changed back to analog. The next diagram we can see some of the different connections using the mediums we mention before.