Network Models, Explained!

What are network models?

For data communication to take place and two or more users can transmit data from one to another, a systematic approach is required. This approach enables users to communicate and transmit data through an efficient and ordered path. It is implemented using models in computer networks and is known as computer network models. In general, it's nothing but a set of rules and standards.

Now we understand what a model is, let's talk about why we need these models? 

There was a big problem which is:

If some company buy their computers from a manufacturer, they need to buy the rest of their devices from the same manufacturer. Also, if a department in a company bought their equipment from IBM, and the other department bought theirs from Digital Equipments they can not communicate. 

So International Standards Orginazion "ISO" developed Open System Interconnect "OSI" to solve the problem. At about the same time, there was a competing model! Which is TCP/IP. TCP/IP was a stripped-down version of the OSI.

What are the similarities between TCP/IP and OSI? 

• Both the reference models are based upon layered architecture.
• The layers in the models are compared with each other. The physical layer and the data link layer of the OSI model correspond to the link layer of the TCP/IP model. The network layers and the transport layers are the same in both the models. The session layer, the presentation layer, and the application layer of the OSI model together form the application layer of the TCP/IP model.
• In both models, protocols are defined in a layer-wise manner.
• In both models, data is divided into packets and each packet may take the individual route from the source to the destination.

What is the difference between TCP/IP and OSI? 

• OSI model is a generic model that is based upon functionalities of each layer. TCP/IP model is a protocol-oriented standard.
• OSI model distinguishes the three concepts, namely, services, interfaces, and protocols. TCP/IP does not have a clear distinction between these three.
• OSI model gives guidelines on how communication needs to be done, while TCP/IP protocols layout standards on which the Internet was developed. So, TCP/IP is a more practical model.
• In OSI, the model was developed first and then the protocols in each layer were developed. In the TCP/IP suite, the protocols were developed first, and then the model was developed.
• The OSI has seven layers while the TCP/IP has four layers.

What are the layers for each model?

First, OSI layers.

Second, TCP/IP layers.

Finally, here is a picture that describes the protocols used at each layer.