Back in old days when network communication was in infancy, different make equipment had proprietary standards of communication. People and big organisations felt the dire need of open and standard communication model which could be independent of the underlying hardware architecture of diverse networking devices. That’s when TCP/IP reference model and OSI model came into existence.
OSI model consists of 7 different communication layers whereas TCP/IP follows a leaner approach and consists of only 4 layers. The internet you see today is purely based on TCP/IP model, and even the emerging technologies are based on TCP/IP model. In fact, TCP/IP model came into picture almost a decade ago from the year (1984) when OSI model was introduced. Then you must be thinking why OSI model came into existence and what is the difference between OSI and TCP/IP model?
As mentioned before, OSI model has 7 layers in comparison to TCP/IP model which has only 4 layers of communication. There are several structural advantages of layering in a networking concept. Every layer must complete its function before the datagram (data unit) is passed over to the next stacked layer.
In a way, there are high interdependencies between layers. Also, individual layers must be optimised separately for the overall model to function in the most desired manner. It was evident that increased laying of OSI model increased the OPEX (operating expense) of the network.
On the hand, TCP/IP model less layered structure made possible to build a simplified and cheaper communication network.
Undoubtedly, people worked on OSI model to develop a better version of TCP/IP model. But interlayer dependencies, increased architecture and elaborate design made it tough to implement newer technologies on OSI model. Whereas, TCP/IP model was easy to implement and was more reliable.
“OSI is a beautiful dream, and TCP/IP is living it!” – Einar Stefferud (Computer researcher)
Free vs paid implementation
TCP/IP model was not developed keeping commercial usage in the view. But government agencies researched for decades and build a free & an open networking model. The Internet protocol is such example which was implemented free of cost on TCP/IP model, and it is not required to educate people about the commercial intent of internet. Isn’t it!
On the contrary, if you want to use OSI model for any networking device then you may have to purchase paper copies from ISO. This is one of the biggest reason why big companies and industries shifted away from OSI model to TCP/IP model.
Final thoughts on OSI vs TCP/IP model
From an architecture perspective, there is not much of difference between OSI and TCP/IP model. For instance, the application layer of TCP/IP embodies the functionality of application, presentation and session layers of OSI model. Same goes with the link layer in TCP/IP suite which emulates features of data link and physical layer of OSI model.
OSI model faltered in the early 90’s, and TCP/IP gained momentum since then. Also, it is a fact that the internet has grown by leaps and bounds only because of openness and simplicity of TCP/IP reference model. OSI model was based on the years of research happened on TCP/IP, and several researchers in the networking domain accuse lousy timing and complicated architecture as the leading cause of OSI not becoming famous.