What is the OSI Model? The 7 Layers Explained

The OSI Model (Open Systems Interconnection Model) is a conceptual framework used to describe the functions of a networking system. The OSI model characterizes computing functions into a universal ready of rules and requirements in order to back up interoperability betwixt different products and software. In the OSI reference model, the communications between a computing system are divide into vii different abstraction layers: Physical, Information Link, Network, Transport, Session, Presentation, and Application.

Created at a time when network computing was in its infancy, the OSI was published in 1984 by the International Organization for Standardization (ISO). Though it does not ever map directly to specific systems, the OSI Model is still used today every bit a ways to describe Network Architecture.

The lowest layer of the OSI Model is concerned with electrically or optically transmitting raw unstructured data bits beyond the network from the physical layer of the sending device to the physical layer of the receiving device. It can include specifications such as voltages, pin layout, cabling, and radio frequencies. At the physical layer, 1 might find “physical” resources such as network hubs, cabling, repeaters, network adapters or modems.

At the data link layer, directly connected nodes are used to perform node-to-node data transfer where data is packaged into frames. The data link layer likewise corrects errors that may accept occurred at the physical layer.

The data link layer encompasses two sub-layers of its own. The first, media access command (MAC), provides flow control and multiplexing for device transmissions over a network. The 2d, the logical link command (LLC), provides flow and error command over the physical medium as well every bit identifies line protocols.

The network layer is responsible for receiving frames from the data link layer, and delivering them to their intended destinations amidst based on the addresses contained inside the frame. The network layer finds the destination past using logical addresses, such as IP (net protocol). At this layer, routers are a crucial component used to quite literally route information where it needs to go betwixt networks.

The transport layer manages the commitment and fault checking of information packets. It regulates the size, sequencing, and ultimately the transfer of data between systems and hosts. One of the well-nigh common examples of the send layer is TCP or the Transmission Control Protocol.

The session layer controls the conversations between dissimilar computers. A session or connectedness betwixt machines is set up, managed, and termined at layer 5. Session layer services also include authentication and reconnections.

The presentation layer formats or translates data for the application layer based on the syntax or semantics that the application accepts. Considering of this, it at times also called the syntax layer. This layer can also handle the encryption and decryption required by the application layer.

At this layer, both the cease user and the application layer interact straight with the software awarding. This layer sees network services provided to end-user applications such as a web browser or Office 365. The application layer identifies communication partners, resource availability, and synchronizes communication.