The Open Systems Interconnection Model (i.e. OSI Model) is a standard reference model for connecting computers on a network. It divides network protocol design and communications into seven different layers. Each layer in the model is designed to provide services to the layer above it. However perfect the OSI Model seems, it has been questioned and compared with other existing models.
Looking into the OSI Model
Since each layer in this model serves a purpose for the layer above it, it would be interesting how each layer interacts with the next one in the upper tier. Here are the seven models you will find:
Physical Layer: This is the first layer in the OSI Model. This refers to the physical hardware used in your network. It also defines physical medium and device relationships. It also includes electrical signals and its transmission. Some of its functions include establishing and terminating communications and connections. It is also responsible for flow control and resolution of any possible contention within the physical layer of the network.
Data Link Layer: This layer provides the means whereby various entities within a network would be able to transfer data. This layer is also responsible for the management of the interaction between various devices. It is also understood that these devices interact using a shared medium thus necessitating a layer that manages how these devices interact and transfer data. Its major function therefore encompasses physical addressing.
Network Layer: This is the last of the media layers in the OSI Model. It is responsible for logical addressing and path determination. It also maintains the quality of the service that was requested by the transport layer. It also performs routing functions, which makes the Internet a possibility.
Transport Layer: This layer is responsible for data transfer between different end users of a network. It also facilitates the data transfer for the other upper tiers in this model. It facilitates the reliability of data transfer and end to end communications.
Session Layer: This layer provides control over the dialogues and communications between the different computers in the network. It is also responsible for the management of both remote and local applications.
Presentation Layer: This layer is mainly responsible for representing data over the network and its encryption. This also translates data into a format that the application layer can work with.
Application Layer: This is the last layer in the OSI Model. It is the part of the model that interacts with the end user and software applications. This is what you interact with when you send e-mails, surf the internet, send files to another computer etc. It interacts with both users and applications in information synchronization and resource availability.
There are also other models beside this reference model. It has been noted that the TCP/IP model is more applicable to real life situations as compared the OSI Model. This is also why some want to abolish this reference model.