lecture3:OSI Model

What is OSI model???
To understand what is the OSI model and why it use, first we will take the following example:
imagine that you are in Baghdad and you want to send an e-mail to your friend in Lebanon . Successfully sending and receiving e-mail involves doing many things, including the following:
? You must type the message in your e-mail application.
? You must address the message in your e-mail application.
? You must click the Send button in your e-mail application to start sending the message.
? You must use the correct type of connections and wires to connect your PC to your local network.
? Your PC must put the data on the wire.
? Your PC must be able to connect to the Internet, and you must provide any necessary login information.
? Network devices must find the best path through the Internet so that the e-mail is received by the right person.


OSI is stand for (Open System Interconnection) Reference Model.

The International Standards Organizations (ISO) committee created a list of all the network functions required for sending data and divided them into seven categories. This model is the OSI seven layer model. The OSI seven-layer model was released in 1984.
Each of the Seven Layers of the OSI Model Represents Functions Required for Communication.