The OSI 7 Layer Model
What is OSI 7 Layer Model
OSI stands for Open Systems Interconnection. It is a model used to standardize the functions of telecommunication and computing systems around the world. OSI 7 is conceptual, as the layers are abstractions that don’t define the actual technology used, however, the network topology and interoperability can be designed.
But what does that actually mean? In Information Technology, standardization is abstract so that providers, manufacturers, programmers and everyone involved has a model to work with that provides a uniform level of understanding. This enhances the interoperability of the different systems and processes, so they can work with each other.
OSI layers
- The physical layer: Layer one is concerned with the transmission of data bits over physical mediums.
- Data link: Layer two specifies transmission of frames between connected nodes on the physical layer.
- Network: Addressing, routing and traffic control of a multi-node network is described by Layer three.
- Transport: Segmentation, acknowledgement and multiplexing between points on a network is defined at Layer four.
- Session: Layer five looks at the continuous exchange of data between two nodes
- Presentation: Encoding, data compression and encryption / decryption between a network service and application happens at Layer six.
- Application: Resource sharing, high level APIs and remote file access is defined by Layer seven.
Layers 1, 2 and 3 are Media Layers while layers 4, 5, 6 and 7 are Host Layers.
