Editing OSI model (section)

{{Short description|Model of communication of seven abstraction layers}}
{{Use British English|date=March 2020}}
{{Use dmy dates|date=April 2019}}
{{OSI model}}

The '''Open Systems Interconnection''' ('''OSI''') '''model''' is a [[reference model]] developed by the [[International Organization for Standardization]] (ISO) that "provides a common basis for the coordination of standards development for the purpose of systems interconnection."<ref name="ISO-7498-1">{{cite ISO standard |date=June 1999|title=ISO/IEC 7498-1:1994 Information technology — Open Systems Interconnection — Basic Reference Model: The Basic Model |csnumber=20269 |at=Introduction |access-date=26 August 2022}}</ref>

In the OSI reference model, the components of a communication system are distinguished in seven [[abstraction layer]]s: Physical, Data Link, Network, Transport, Session, Presentation, and Application.<ref>{{Cite web |date=2018-08-10 |title=What is the OSI Model? |url=https://www.forcepoint.com/cyber-edu/osi-model |access-date=2022-05-20 |website=Forcepoint |language=en}}</ref>

The model describes communications from the physical implementation of transmitting [[bit]]s across a [[transmission medium]] to the highest-level representation of data of a [[distributed application]]. Each layer has well-defined functions and semantics and serves a class of functionality to the layer above it and is served by the layer below it. Established, well-known [[communication protocol]]s are decomposed in software development into the model's hierarchy of function calls.

The [[Internet protocol suite]] as defined in {{IETF RFC|1122}} and {{IETF RFC|1123}} is a model of networking developed contemporarily to the OSI model, and was funded primarily by the U.S. Department of Defense. It was the foundation for the development of the [[Internet]]. It assumed the presence of generic physical links and focused primarily on the software layers of communication, with a similar but much less rigorous structure than the OSI model.

In comparison, several networking models have sought to create an intellectual framework for clarifying networking concepts and activities,{{citation needed|date=April 2022}} but none have been as successful as the OSI reference model in becoming the standard model for discussing and teaching networking in the field of [[information technology]]. The model allows transparent communication through equivalent exchange of [[protocol data unit]]s (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.<ref name="guide-to-networking-essentials">{{cite book|url=https://www.cengage.com/c/guide-to-networking-essentials-7e-tomsho/9781305105430PF/|title=Guide to Networking Essentials|edition=7th|first=Greg|last=Tomsho|publisher=Cengage|date=2016|access-date=2022-04-03}}</ref>

[[File:OSI-model-Communication.svg|thumb|400px|Communication in the OSI model (example with layers 3 to 5)]]