Data Communications And Networking |Chapter-2 | "Introduction" |Fourth Edition|

 Network Models

2-1 LAYERED TASKS

We use the concept of layers in our daily life. As an example, let us consider two friends who communicate through postal mail. The process of sending a letter to a friend would be complex if there were no services available from the post office. 

Topics discussed in this section:

Sender, Receiver, and Carrier Hierarchy

Figure 2.1 Tasks involved in sending a letter

2-2 THE OSI MODEL

Established in 1947, the International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards. An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. It was first introduced in the late 1970s. 

Topics discussed in this section:

• Layered Architecture

• Peer-to-Peer Processes

• Encapsulation

Note:-

ISO is the organization.
OSI is the model.

Figure 2.2 Seven layers of the OSI model

Figure 2.3 The interaction between layers in the OSI model

Figure 2.4 An exchange using the OSI model

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