OSI model

The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology

OSI model
Layer Protocol data unit (PDU) Function
Host layers 7 Application Data High-level APIs, including resource sharing, remote file access
6 Presentation Translation of data between a networking service and an application; including character encoding, data compression and encryption/decryption
5 Session Managing communication sessions, i.e., continuous exchange of information in the form of multiple back-and-forth transmissions between two nodes
4 Transport Segment, Datagram Reliable transmission of data segments between points on a network, including segmentation, acknowledgement and multiplexing
Media layers 3 Network Packet Structuring and managing a multi-node network, including addressing, routing and traffic control
2 Data link Frame Reliable transmission of data frames between two nodes connected by a physical layer
1 Physical Symbol Transmission and reception of raw bit streams over a physical medium

Snippet from Wikipedia: OSI model

The Open Systems Interconnection model (OSI model) is a conceptual model that characterises and standardises the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology. Its goal is the interoperability of diverse communication systems with standard communication protocols.

The model partitions the flow of data in a communication system into seven abstraction layers, from the physical implementation of transmitting bits across a communications medium to the highest-level representation of data of a distributed application. Each intermediate layer serves a class of functionality to the layer above it and is served by the layer below it. Classes of functionality are realized in software by standardized communication protocols.

The OSI model was developed starting in the late 1970s to support the emergence of the diverse computer networking methods that were competing for application in the large national networking efforts in the world. In the 1980s, the model became a working product of the Open Systems Interconnection group at the International Organization for Standardization (ISO). While attempting to provide a comprehensive description of networking, the model failed to garner reliance by the software architects in the design of the early Internet, which is reflected in the less prescriptive Internet Protocol Suite, principally sponsored under the auspices of the Internet Engineering Task Force (IETF).

Source: YouTube