Editing OSI model (section)

===Comparison with TCP/IP model===
{{See also|Internet protocol suite#Comparison of TCP/IP and OSI layering}}
The design of protocols in the [[TCP/IP model]] of the Internet does not concern itself with strict hierarchical encapsulation and layering. {{IETF RFC|3439}} contains a section entitled "Layering [[considered harmful]]".<ref>{{cite IETF|rfc=3439|title=Some Internet Architectural Guidelines and Philosophy|section=3|sectionname=Layering Considered Harmful|date=December 2002|access-date=25 April 2022}}</ref> TCP/IP does recognize four broad layers of functionality which are derived from the operating scope of their contained protocols: the scope of the software application; the host-to-host transport path; the internetworking range; and the scope of the direct links to other nodes on the local network.<ref>
{{cite book|title=The Illustrated Network: How TCP/IP Works in a Modern Network|author=Walter Goralski|year=2009|page=26|isbn=978-0123745415|publisher=[[Morgan Kaufmann]]|url=http://www.exa.unicen.edu.ar/catedras/comdat1/material/TP1-Ejercicio5-ingles.pdf}}</ref>

Despite using a different concept for layering than the OSI model, these layers are often compared with the OSI layering scheme in the following manner:
* The Internet [[application layer]] maps to the OSI application layer, presentation layer, and most of the session layer.
* The TCP/IP [[transport layer]] maps to the graceful close function of the OSI session layer as well as the OSI transport layer.
* The [[internet layer]] performs functions as those in a subset of the OSI network layer.
* The [[link layer]] corresponds to the OSI data link layer and may include similar functions as the physical layer, as well as some protocols of the OSI's network layer.
These comparisons are based on the original seven-layer protocol model as defined in ISO 7498, rather than refinements in the internal organization of the network layer.

The [[OSI protocols|OSI protocol suite]] that was specified as part of the OSI project was considered by many as too complicated and inefficient, and to a large extent unimplementable.<ref name="Tanenbaum 2023">{{cite book |last=Tanenbaum |first=Andrew S. |author-link=Andrew S. Tanenbaum |title=Computer networks |publisher=Prentice Hall PTR |publication-place=Upper Saddle River, NJ |year=2003 |isbn=978-0-13-066102-9 |oclc=50166590 |page=}}</ref>{{page needed|date=July 2024}} Taking the "forklift upgrade" approach to networking, it specified eliminating all existing networking protocols and replacing them at all layers of the stack. This made implementation difficult and was resisted by many vendors and users with significant investments in other network technologies. In addition, the protocols included so many optional features that many vendors' implementations were not interoperable.<ref name="Tanenbaum 2023"/>{{page needed|date=July 2024}}

Although the OSI model is often still referenced, the [[Internet protocol suite]] has become the standard for networking. TCP/IP's pragmatic approach to computer networking and to independent implementations of simplified protocols made it a practical methodology.<ref name="Tanenbaum 2023"/>{{page needed|date=July 2024}}  Some protocols and specifications in the OSI stack remain in use, one example being [[IS-IS]], which was specified for OSI as ISO/IEC 10589:2002 and adapted for Internet use with TCP/IP as RFC 1142.<ref name="RFC 1142">{{cite IETF |rfc=1142 |title=OSI IS-IS Intra-domain Routing Protocol |website=IETF Datatracker |access-date=2024-07-12}}</ref>