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13 : Comparison and contrast of TCP/IP and OSI models

As a learner of computer networks, it is of prime importance to be able to identify the differences between TCP/IP model and OSI model. Hence, I am trying, in what follows, to draw a distinction between these two indispensable models as well as delineate each one’s characteristics and significance.

Brief history of TCP/IP

Before embarking on a rigorous dissection of TCP/IP model vis-à-vis OSI model, a briefly useful chronicle of TCP/IP model’s rise and development would be crucially substantial in order to have a thorough grasp of the whole issue. 

TCP/IP model, as the name implies, is composed of two elements TCP and IP, which are the first and original protocols in the suite in terms of development. In 1978, it was split into two protocols : TCP and IP. With regard to TCP, standing for Transmission Control Protocol, it is one of the main protocols of the Internet protocol suite ( a set of protocols working together for the purpose of data transmission), including IP, being short for Internet Protocol, which is also a constituent part of the model, playing a central role in the communication of data. Thus TCP and IP protocols are complementary, that is, no one can accomplish a successful transfer of data without the other.

TCP/IP model was created in the 1970s, long before OSI model, by DARPA (Defense Advanced Research Projects Agency), an agency of the United States Department of Defense specialized in the development of technologies for the sake of the military. That is why it is sometimes referred to as DoD (Department of Defense) model. The first founding name of DARPA was ARPA which was created in 1958 by President Dwight D. Eisenhower as a reaction to the launching of Sputnik, the first satellite to be placed in orbit, by the former Soviet Union. Then the name changed to DARPA in March 1972 to last only few years to be altered again to ARPA in February in 1993, to finally get its final name as DARPA in March 1996. 

Comparison and contrast of TCP/IP and OSI models

The most obvious contrast between the two models, in terms of the layered diagram, is that TCP/IP model comprises only four layers, whereas OSI model encompasses seven hierarchical layers. Being made of only four layers, the top fourth layer, Application layer (in TCP/IP), is equivalent to the three upper layers in OSI model, which are Application, Presentation, and Session layers. As for the third layer in TCP/IP model, Host-to-Host layer, is corresponding Transport layer in OSI model. However, the second layer of TCP/IP, Internet layer, has altered to Network layer in OSI model. In a similar way, the first layer in TCP/IP, Network Access Layer, corresponds to the Data-Link layer and Physical Layer in OSI model. The following figure sums it all up.

A very major difference between the two models is that OSI model is theoretical while TCP/IP is practical ; or, in other words, OSI model is a reference model whereas TCP/IP is an implementation of the former.  OSI model is conceptual in the sense that it describes how data transmission occurs between sender and receiver  in terms of seven illustrative layers in addition to characterizing and standardizing communication regardless of the nature of the technology being utilized. So the object of OSI model is to enable respective networking devices and systems made by different manufacturers to interoperate.

In contrast, TCP/IP is the very essence protocol, among others, of the Internet Protocol Suite used for data communication. TCP/IP suite is a set of protocols that are employed in a basic transfer of data, for this reason it is known as a practical model. The protocols included in the suite are put into function in a basic data transport.
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13 : Comparison and contrast of TCP/IP and OSI models Reviewed by M. Bouftira on 5:25:00 PM Rating: 5

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