SIMILARITIES
The main similarities between the two models include the following:

They share similar architecture. – Both of the models share a similar architecture. This can be illustrated by the fact that both of them are constructed with layers.

They share a common application layer.- Both of the models share a common “application layer”. However in practice this layer includes different services depending upon each model.

Both models have comparable transport and network layers.- This can be illustrated by the fact that whatever functions are performed between the presentation and network layer of the OSI model similar functions are performed at the Transport layer of the TCP/IP model.

Knowledge of both models is required by networking professionals.- According to article obtained from the internet networking professionals “need to know both models”. (Source:

Both models assume that packets are switched.- Basically this means that individual packets may take differing paths in order to reach the same destination.

DIFFERENCES:
The main differences between the two models are as follows:

TCP/IP Protocols are considered to be standards around which the internet has developed. The OSI model however is a “generic, protocol- independent standard.”

TCP/IP combines the presentation and session layer issues into its application layer.

TCP/IP combines the OSI data link and physical layers into the network access layer.

TCP/IP appears to be a more simpler model and this is mainly due to the fact that it has fewer layers.

TCP/IP is considered to be a more credible model- This is mainly due to the fact because TCP/IP protocols are the standards around which the internet was developed therefore it mainly gains creditability due to this reason. Where as in contrast networks are not usually built around the OSI model as it is merely used as a guidance tool.

The OSI model consists of 7 architectural layers whereas the TCP/IP only has 4 layers.

Service : it tells only what the layer does, and not how entities above it access it or how the layer work.
Interfaces : it tells the processes above it how to access it, and specifies parameters and results.
Protocol : With this definition, the layer can characterize its own protocols, as many as he wants, and change them without affecting software in higher layers.

So we can introduce main differences between from these concepts :

OSI Model Reference

TCP/IP Model Reference

Service, interface
and protocol Service, interface and protocol are not clearly defined. For example, the only real services offered by the Internet layer are
- Send IP Packet
- Receive IP Packet Protocols in the OSI model are better hidden and can be replaced relatively easily as the technology changes, which is one of the main objective of layered protocols. Functionalities Because models were invented before protocols, functionalities put in each layer are not very optimized. In this case, the protocols have been invented before models, so the functionalities are perfectly described. Numbers of layers Seven layers, Network (Internet), Transport and Application layers being similar to TCP/IP Only four layers. Connectionless/
Connection-oriented communication Both connectionless and connection-oriented communication are supported in the network layer, but only connection-oriented communication in the transport layer. Only one mode in the network layer (connectionless) but both modes in the transport layer are supported, giving the users a choice.