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 'provides a common basis for the coordination of [ISO] standards development for the purpose of systems interconnection'. In the OSI reference model, the communications between a computing system are split into seven different abstraction layers: Physical, Data Link, Network, Transport, Session, Presentation, and Application.

The model partitions the flow of data in a communication system into seven abstraction layers, to describe networked communication 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 all software development through all and any standardized communication protocols.

Each layer in the OSI model has its own well-defined functions, and the functions of each layer communicate and interact with the layers immediately above and below it, unless the layer does not have layers below or above. In either case, each layer of the OSI model has its own well-defined functions that describe the basic applications for communication of all communication protocols.

The Internet protocol suite has a separate model, the layers of which are mentioned in RFC 1122 and RFC 1123. That model combines the physical and data link layers of the OSI model into a single link layer, and has a single application layer for all protocols above the transport layer, as opposed to the separate application, presentation and session layers of the OSI model.

In comparison, several networking models have sought to create an intellectual framework for clarifying networking concepts and activities, but none have been as successful as the OSI reference model in becoming the standard model for discussing, teaching, and learning for the networking procedures in the field of Information technology. Additionally, the model allows transparent communication through equivalent exchange of protocol data units (PDUs) between two parties, through what is known as peer-to-peer networking (also known as peer-to-peer communication). As a result, the OSI reference model has not only become an important piece among professionals and non-professionals alike, but also in all networking between one or many parties, due in large part to its commonly accepted user-friendly framework.

The OSI-model.txt
Layer 1: The physical layer
Layer 2: The data link layer
Layer 3: The network layer
Layer 4: The transport layer
Layer 5: The session layer
Layer 6: The presentation layer
Layer 7: The application layer

Source: YouTube

  • kb/osi_model.txt
  • Last modified: 2022/08/16 15:15
  • by Henrik Yllemo