Similarities and differences between TCP/IP Reference Model and OSI reference model

The OSI reference model has many similarities with the TCP/IP reference model. They are based on the concept of an independent protocol stack. In addition, the features of the layer are similar. For example, in the two models, the transmission layer and above all provide end-to-end and network-independent transmission services for processes that want to communicate. These layers form a transport provider. Similarly, in both models, the former users at the transport layer and above are application-dominated users of the transmission service.

The OSI model has three main concepts: Service, interface, and protocol.

The greatest contribution of the OSI model is to clarify the differences between the three concepts. Each layer provides services for the layer above it. The service defines what the layer does, regardless of how the above layer accesses it or how the layer works.

A layer of excuse tells the above process how to access it. It defines what parameters are required and what the expected results are. Similarly, it has nothing to do with how the layer works.

Finally, the internal transactions of a layer when the Peer protocol is used. It can use any protocol, as long as it can complete the work, it can also change the protocol used without affecting the layer above it.

These ideas are very consistent with modern object-oriented technology. An object (like a layer) has a set of methods (Operations) that can be used by external processes of the object. The semantics of these methods defines the service provided by the object. The parameters and results of the method are the interface of the object, and the code inside the object is its protocol, which is invisible outside the object.

At first, the TCP/IP reference model did not clearly distinguish between services, interfaces, and Protocols. Later, people tried to improve it to be close to OSI, for example, the real service knowledge sending IP group and interface IP group provided by the Internet layer.

Therefore, the protocols in the OSI model are better concealed than those in the TCP/IP reference model, and can be easily replaced when technology changes. At first, one of the main purposes of protocol layering was to make such a replacement.

The OSI reference model is generated before the Protocol. This means that the model is not biased towards any specific protocol, so it is quite universal. However, the disadvantage is that the designer does not have much experience in the protocol, so he does not know which functions should be put to the best layer.

The opposite is true for TCP/IP. This model actually describes the existing protocols, so there is no possibility that the model cannot match, and they work very well together. The problem is that this model is not suitable for any other protocol stack. Therefore, it is not particularly useful for describing other non-TCP/IP network technologies.

The obvious difference between the two models is the number of layers: the OSI model has seven layers, while the TCP/IP model has only four layers. They all have the network layer, transport layer, and application layer, but the other layers are different.

Another difference is connection-oriented and connectionless communication. The OSI model provides connectionless and connection-oriented communication at the network layer, but only connection-oriented communication at the transport layer, which is dependent on it. However, the TCP/IP model only has one communication mode (no connection) at the network layer, but it supports two modes at the transport layer, giving users the opportunity to choose from. This is important when selecting a simple request-response protocol.