OSI model: Difference between revisions - Wikipedia

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The '''Open Systems Interconnection''' ('''OSI''') '''model''' is a [[reference model]] from 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 communications between systems are split into seven different abstraction layers: 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 partitions the flow of data in a communication system into seven [[abstraction layer]]s to describe networked communication from the physical implementation of transmitting [[bit]]s across a [[transmission medium|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 realizedimplemented in all software development through allusing standardizedestablished [[communication protocol]]s.

Each layer in the OSI model has well-defined functions, and the methods of each layer communicate and interact with those of the layers immediately above and below as appropriate.

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In the early- and mid-1970s, networking was largely either government-sponsored ([[NPL network]] in the UK, [[ARPANET]] in the US, [[CYCLADES]] in France) or vendor-developed with proprietary standards, such as [[IBM]]'s [[Systems Network Architecture]] and [[Digital Equipment Corporation]]'s [[DECnet]]. [[Public data network]]s were only just beginning to emerge, and these began to use the [[X.25]] standard in the late 1970s.<ref name=":3" /><ref name=":2">{{cite journal|last1=Roberts|first1=Dr. Lawrence G.|date=November 1978|title=The Evolution of Packet Switching|url=http://www.ece.ucf.edu/~yuksem/teaching/nae/reading/1978-roberts.pdf|journal=IEEE Invited Paper|access-date=February 26, 2022}}</ref>

The [[Packet switching#EPSS|Experimental Packet Switched System]] in the UK {{circa|1973}}–1975 identified the need for defining higher level protocols.<ref name=":3">{{Cite book|last1=Davies|first1=Howard|url=https://books.google.com/books?id=DN-t8MpZ0-wC&pg=PA3|title=A History of International Research Networking: The People who Made it Happen|last2=Bressan|first2=Beatrice|date=2010-04-26|publisher=John Wiley & Sons|isbn=978-3-527-32710-2|pages=2–3|language=en}}</ref> The UK [[National Computing Centre]] publication, ''Why Distributed Computing'', which came from considerable research into future configurations for computer systems,<ref>{{Cite book|url=https://books.google.com/books?id=fbm7AAAAIAAJ|title=Why distributed computing?: An NCC review of potential and experience in the UK|last1=Down|first1=Peter John|last2=Taylor|first2=Frank Edward|date=1976|publisher=NCC Publications|isbn=9780850121704|language=en}}</ref> resulted in the UK presenting the case for an international standards committee to cover this area at the ISO meeting in [[Sydney]] in March 1977.<ref>{{cite book |last=Radu |first=Roxana |doi=10.1093/oso/9780198833079.003.0003 |chapter=Revisiting the Origins: The Internet and its Early Governance |title=Negotiating Internet Governance |isbn=9780191871405 |date=2019 |pages=43–74 |publisher=Oxford University Press}}</ref><ref name="ieee201703">{{cite magazine|author=Andrew L. Russell|date=30 July 2013|title=OSI: The Internet That Wasn't|url=https://spectrum.ieee.org/computing/networks/osi-the-internet-that-wasnt|magazine=[[IEEE Spectrum]]|volume=50|issue=8}}</ref>

Beginning in 1977, the ISO initiated a program to develop general standards and methods of networking. A similar process evolved at the [[International Telegraph and Telephone Consultative Committee]] (CCITT, from French: ''Comité Consultatif International Téléphonique et Télégraphique''). Both bodies developed documents that defined similar networking models. The British [[Department of Trade and Industry (United Kingdom)|Department of Trade and Industry]] acted as the secretariat, and [[universities in the United Kingdom]] developed [[prototype]]s of the standards.<ref>{{Cite journal |last1=Campbell-Kelly |first1=Martin |last2=Garcia-Swartz |first2=Daniel D |date=2013 |title=The History of the Internet: The Missing Narratives |url=https://papers.ssrn.com/abstract=867087 |journal=Journal of Information Technology |language=en |volume=28 |issue=1 |pages=18–33 |doi=10.1057/jit.2013.4 |ssrn=867087 |s2cid=41013 |issn=0268-3962}}</ref>

The OSI model was first defined in raw form in [[Washington, D.C.]], in February 1978 by French software engineer [[Hubert Zimmermann]], and the refined but still draft standard was published by the ISO in 1980.<ref>{{cite magazine|urlname=https://spectrum.ieee.org/computing/networks/osi-the-internet-that-wasnt |title=OSI The Internet That Wasn't|magazine=IEEE Spectrum |date=March"ieee201703" 2017}}</ref>

The drafters of the reference model had to contend with many competing priorities and interests. The rate of technological change made it necessary to define standards that new systems could converge to rather than standardizing procedures after the fact; the reverse of the traditional approach to developing standards.<ref>{{Cite book|last=Sunshine|first=Carl A.|url=https://books.google.com/books?id=Hzj2BwAAQBAJ&pg=PA35|title=Computer Network Architectures and Protocols|publisher=Springer Science & Business Media|year=1989|isbn=978-1-4613-0809-6|pages=35|language=en}}</ref> Although not a standard itself, it was a framework in which future standards could be defined.<ref>{{Cite book|last=Hasman|first=A.|url=https://books.google.com/books?id=u2KyQjiwwTUC&pg=PA251|title=Education and Training in Health Informatics in Europe: State of the Art, Guidelines, Applications|date=1995|publisher=IOS Press|isbn=978-90-5199-234-2|pages=251|language=en}}</ref>

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{{cite web| url = http://www.itu.int/rec/T-REC-X/en| title = ITU-T X-Series Recommendations}}</ref> Some of the protocol specifications were also available as part of the ITU-T X series. The equivalent ISO/IEC standards for the OSI model were available from ISO. Not all are free of charge.<ref>{{cite web|url=http://standards.iso.org/ittf/PubliclyAvailableStandards/index.html |title=Publicly Available Standards |publisher=Standards.iso.org |date=30 July 2010 |access-date=11 September 2010}}</ref>

OSI was an industry effort, attempting to get industry participants to agree on common network standards to provide multi-vendor interoperability.<ref>{{Cite book|url=https://books.google.com/books?id=OVpzAwAAQBAJ&q=Open+Standards+and+the+Digital+Age:+History,+Ideology,+and+Networks|title=Open Standards and the Digital Age: History, Ideology, and Networks|last=Russell|first=Andrew L.|date=2014-04-28|publisher=Cambridge University Press|isbn=978-1-139-91661-5|language=en}}</ref> It was common for large networks to support multiple network protocol suites, with many devices unable to interoperate with other devices because of a lack of common protocols. For a period in the late 1980s and early 1990s, engineers, organizations and nations became [[Protocol Wars|polarized over the issue of which standard]], the OSI model or the [[Internet protocol suite]], would result in the best and most robust computer networks.<ref name="ieee201703" /><ref>{{Cite webjournal|url=https://www2courses.cs.duke.edu/courses/common/compsci092/papers/govern/consensus.pdf|title=Rough Consensus and Running Code' and the Internet-OSI Standards War|last=Russell|first=Andrew L.|publisherjournal=IEEE Annals of the History of Computing|volume=28|issue=3|date=July-September 2006|pages=48-61|doi=10.1109/MAHC.2006.42}}</ref><ref>{{Cite web|date=2006|title=Standards Wars|url=https://courses.cs.washington.edu/courses/csep590a/06au/projects/standards-wars.pdf}}</ref> However, while OSI developed its networking standards in the late 1980s,<ref>{{Cite book|url=https://books.google.com/books?id=CRMEAAAAMBAJ|title=Network World|date=1988-02-15|publisher=IDG Network World Inc|language=en}}</ref>{{page needed|date=July 2024}}<ref>{{Cite book|url=https://books.google.com/books?id=dBMEAAAAMBAJ&pg=PA50|title=Network World|date=1988-10-10|publisher=IDG Network World Inc|language=en}}</ref>{{page needed|date=July 2024}} [[TCP/IP]] came into widespread use on multi-vendor networks for [[internetworking]].

The OSI model is still used as a reference for teaching and documentation;<ref>{{Cite web|title=The OSI model explained: How to understand (and remember) the 7 layer network model|url=https://www.networkworld.com/article/3239677/the-osi-model-explained-how-to-understand-and-remember-the-7-layer-network-model.html|last=Shaw|first=Keith|date=2018-10-22|website=Network World|language=en|access-date=2020-05-16|archive-date=4 October 2020|archive-url=https://web.archive.org/web/20201004172259/https://www.networkworld.com/article/3239677/the-osi-model-explained-how-to-understand-and-remember-the-7-layer-network-model.html|url-status=dead}}</ref> however, the [[OSI protocols]] originally conceived for the model did not gain popularity. Some engineers argue the OSI reference model is still relevant to [[cloud computing]].<ref>{{Cite web|title=An OSI Model for Cloud|url=https://blogs.cisco.com/cloud/an-osi-model-for-cloud|date=2017-02-24|website=Cisco Blogs|language=en-US|access-date=2020-05-16}}</ref> Others say the original OSI model does not fit today's networking protocols and have suggested instead a simplified approach.<ref>{{Cite web|title=Why it's time to let the OSI model die|url=https://www.networkworld.com/article/2276158/why-it-s-time-to-let-the-osi-model-die.html|last1=Taylor|first1=Steve|last2=Metzler|first2=Jim|date=2008-09-23|website=Network World|language=en|access-date=2020-05-16}}</ref><ref name="Crawford"/>

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===Layer 5: Session layer===

{{main|Session layer}}

The session layer creates the setup, controls the connections, and ends the [[teardown (communications)|teardown]], between two or more computers, which is called a "session". Common functions of the session layer include user logon (establishment) and user logoff (termination) functions. Including this matter, authentication methods are also built into most client software, such as FTP Client and NFS Client for Microsoft Networks. Therefore, the session layer establishes, manages and terminates the connections between the local and remote application. The session layer also provides for [[full-duplex]], [[half-duplex]], or [[Simplex communication|simplex]] operation,{{cn|date=April 2024}}, and establishes procedures for checkpointing, suspending, restarting, and terminating a session between two related streams of data, such as an audio and a video stream in a web-conferencing application. Therefore, the session layer is commonly implemented explicitly in application environments that use [[remote procedure call]]s.

===Layer 6: Presentation layer===

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* [[Security service (telecommunication)]]<ref name=x800>{{cite web|url=http://www.itu.int/rec/T-REC-X.800-199103-I/e|title=ITU-T Recommendation X.800 (03/91), ''Security architecture for Open Systems Interconnection for CCITT applications''|publisher=ITU|access-date=14 August 2015}}</ref> as defined by [[ITU-T]] X.800 recommendation.

* Management functions, i.e. functions that permit to configure, instantiate, monitor, terminate the communications of two or more entities: there is a specific application-layer protocol, [[Common Management Information Protocol]] (CMIP) and its corresponding service, [[Common Management Information Service]] (CMIS), they need to interact with every layer in order to deal with their instances.

* [[Multiprotocol Label Switching]] (MPLS), ATM, and X.25 are 3a protocols. OSI subdivides the Network Layer into three sublayers: 3a) Subnetwork Access, 3b) Subnetwork Dependent Convergence and 3c) Subnetwork Independent Convergence.<ref name="Hegering, Abeck, & Neumair 1999">{{cite book |lastlast1=Hegering |firstfirst1=Heinz-Gerd |last2=Abeck |first2=Sebastian |last3=Neumair |first3=Bernhard |chapter=Fundamental Structures of Networked Systems |chapter-url=https://archive.org/details/integratedmanage0000hege/page/12/mode/2up |chapter-url-access=registration |title=Integrated management of networked systems: concepts, architectures, and their operational application |url=https://archive.org/details/integratedmanage0000hege/page/12/mode/2up |url-access=registration |publisher=Morgan Kaufmann |publication-place=San Francisco, Calif. |year=1999 |isbn=978-1-55860-571-8 |oclc=1341886747 |page=[https://archive.org/details/integratedmanage0000hege/page/54/mode/2up 54] |via=Internet Archive}}</ref> It was designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients which provide a [[datagram]]-based service model. It can be used to carry many different kinds of traffic, including IP packets, as well as native ATM, SONET, and Ethernet frames. Sometimes one sees reference to a Layer 2.5.

* Cross MAC and PHY Scheduling is essential in wireless networks because of the time-varying nature of wireless channels. By scheduling packet transmission only in favourable channel conditions, which requires the MAC layer to obtain channel state information from the PHY layer, network throughput can be significantly improved and energy waste can be avoided.<ref name="Miao & Song 2014">{{cite book |lastlast1=Miao |firstfirst1=Guowang |authorauthor1-link=Guowang Miao |last2=Song |first2=Guocong |title=Energy and spectrum efficient wireless network design |url=https://archive.org/details/energyspectrumef0000mia |url-access=registration |publisher=Cambridge University Press |publication-place=New York |year=2014 |isbn=978-1-139-62677-4 |oclc=898138775 |page= |via=Internet Archive}}</ref>{{page needed |date=July 2024}}

==Programming interfaces==

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|style="text-align:center;"| 7

| Application

| {{hlist |[[FTAM]] |[[X.400]] |[[X.500]] |[[Directory Access Protocol|DAP]] |[[Remote Operations Service Element protocol|ROSE]] |RTSE |[[Association Control Service Element|ACSE]]<ref> name="ITU Rec.-T X.227">{{cite (ISOweb 8650),|title=ITU-T X.217227 (ISO 864904/1995).</ref> |[[Common management information protocol|CMIP]]<ref>X.700 series of recommendations from the website=ITU-T (in particular X.711) and ISO 9596.</ref>}}Recommendations

|date=1995-04-10 |url=https://www.itu.int/itu-t/recommendations/rec.aspx?rec=X.227 |access-date=2024-07-12}}</ref><ref name="ITU-T X.217">{{cite web |title=ITU-T X.217 |website=Open Systems Interconnection |date=1995-04-10 |url=https://www.itu.int/rec/T-REC-X.217-199504-I |access-date=2024-07-12}}</ref> |[[Common management information protocol|CMIP]]<ref name="X.700">{{cite web |title=X.700: Management framework for Open Systems Interconnection (OSI) for CCITT applications |website=ITU |date=1992-09-10 |url=https://www.itu.int/rec/T-REC-X.700-199209-I |access-date=2024-07-12}}</ref><ref name="X.711">{{cite web |title=X.711 |website=Open Systems Interconnection |date=2014-05-15 |url=https://www.itu.int/rec/T-REC-X.711/en |access-date=2024-07-12}}</ref><ref name="9596-1:1998(en)">{{cite web |title=ISO/IEC 9596-1:1998(en) |website=ISO |url=https://www.iso.org/obp/ui/#iso:std:iso-iec:9596:-1:ed-3:v1:en |access-date=2024-07-12}}</ref><ref name="9596-2:1993(en)">{{cite web |title=ISO/IEC 9596-2:1993(en) |website=ISO |url=https://www.iso.org/obp/ui/#iso:std:iso-iec:9596:-2:ed-1:v1:en |access-date=2024-07-12}}</ref>}}

| {{hlist |[[HTTP]]| [[HTTPS]] |[[FTP]] |[[SMTP]]}}

| {{hlist |[[INAP]] |[[Mobile Application Part|MAP]] |[[Transaction Capabilities Application Part|TCAP]] |[[ISDN User Part|ISUP]] |[[Telephone User Part|TUP]]}}

| {{hlist |[[Apple Filing Protocol|AFP]] |[[Zone Information Protocol|ZIP]] |[[Routing Table Maintenance Protocol|RTMP]] |[[AppleTalk#Name Binding Protocol|NBP]]}}

| {{hlist |[[Service Advertising Protocol|SAP]]}}

| {{hlist |Transaction Services |Presentation Services}}

| {{hlist |[[IBM Advanced Program-to-Program Communication|APPC]]}}

|

| {{hlist |[[Web Browser]] |[[WebDAV]] |[[SOAP]] |[[OpenID]] |[[REST API]] |[[OAuth]] |[[GraphQL]] |[[ActivityPub]] |[[Git]] |[[DNS over HTTP]]}}

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| {{hlist |[[Apple Filing Protocol|AFP]]}}

|

| Presentation Services

|

|

| {{hlist |[[XML]] |[[JSON]] |[[MIME]] |[[Percent-encoding]] |[[base64]] |[[gzip]] |[[brotli]]}}

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| {{hlist |[[AppleTalk#AppleTalk Session Protocol|ASP]] |[[AppleTalk#AppleTalk Data Stream Protocol|ADSP]] |[[AppleTalk#Printer Access Protocol|PAP]]}}

| {{hlist |[[NWLink]]}}

| {{hlist |[[Presentation Services |Data LinkFlow Control|DLC]]?}}

|

| {{hlist |HTTP [[List_of_HTTP_header_fields|headers]], including [[HTTP cookie|cookies]] |[[CSRF token]]s |[[WebSocket]]}}

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| {{hlist |[[Datagram Delivery Protocol|DDP]]}}

| {{hlist |[[Sequenced packet exchange|SPX]]}}

| {{hlist|Data Flow Control |Transmission Control}}

|

|

| {{hlist |[[HTTP]]/[[HTTP/2]]/[[HTTP/3]] |[[WebSocket]] |[[DTLS]]}} Port number can be specified.

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| [[AppleTalk#AppleTalk Transaction Protocol|ATP]] {{small|([[TokenTalk]]{{\}}[[EtherTalk]])}}

| {{hlist |[[IPX]]}}

| {{hlist |[[IBM NetworkTransmission Control Program|IBMPath NCP]]Control}}

| {{hlist |[[Radio Resource Control|RRC]]{{\}}[[Broadcast/Multicast Control|BMC]]}}

| Out of scope. [[IP address]]es can be used instead of [[domain names]] in [[URL]]s.

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| {{hlist |[[LocalTalk]] |[[AppleTalk Remote Access|ARA]] |[[Point-to-Point Protocol|PPP]]}}

| [[IEEE 802.3|IEEE 802.3 framing]]<br/>[[Ethernet II framing]]

| {{hlist |Path Control | [[Synchronous Data Link Control|SDLC]]]}}

| {{hlist |[[PDCP]]<ref name="TS36300">{{cite web|url=http://www.3gpp.org/ftp/Specs/html-info/36300.htm|title=3GPP specification: 36.300|work=3gpp.org|access-date=14 August 2015}}</ref> |[[Logical Link Control|LLC]] |[[Medium access control|MAC]]}}

| Out of scope.

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| {{hlist |[[RS-232]] |[[RS-422]] |[[PhoneNet]]}}

|

| {{hlist |[[Twinaxial cabling|Twinax]]Physical}}

| [[Universal Mobile Telecommunications System#Air interfaces|UMTS air interfaces]]

| Out of scope.

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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 Networksnetworks |publisher=Prentice Hall PTR |publication-place=Upper Saddle River, §NJ 1.4.4.|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|rfc=1142 |title=OSI IS-IS Intra-domain Routing Protocol |website=IETF Datatracker |access-date=2024-07-12}}.</ref>

==See also==

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==Further reading==

*{{cite [[book |last=Day |first=John D. |author-link=John Day (computer scientist)|John Day]], "|title=Patterns in Network Architecture: A Return to Fundamentals" (Prentice|publisher=Pearson HallEducation 2007|publication-place=Upper Saddle River, N.J. {{ISBN|year=2008 |isbn=978-0-13-225242-3 |oclc=213482801}})

*{{cite book |last=Dickson |first=Gary |last2=Lloyd |first2=Alan |title=Open Systems Interconnection |publisher=Prentice Hall |publication-place=New York |year=1992 |isbn=978-0-13-640111-7 |oclc=1245634475 |url=https://archive.org/details/opensystemsinter0000dick |url-access=registration |via=Internet Archive}}

* [[Marshall Rose]], "The Open Book" (Prentice-Hall, Englewood Cliffs, 1990)

*{{cite book |last=Piscitello |first=David M. |last2=Chapin |first2=A. Lyman |title=Open systems networking : TCP/IP and OSI |publisher=Addison-Wesley Pub. Co. |publication-place=Reading, Mass. |year=1993 |isbn=978-0-201-56334-4 |oclc=624431223 |url=https://archive.org/details/opensystemsnetwo0000pisc |url-access=registration |via=Internet Archive}}

* David M. Piscitello, A. Lyman Chapin, ''Open Systems Networking'' (Addison-Wesley, Reading, 1993)

*{{cite book |last=Rose |first=Marshall T. |author-link=Marshall Rose |title=The Open Book: A Practical Perspective on OSI |publisher=Prentice Hall |publication-place=Englewood Cliffs, N.J. |year=1990 |isbn=978-0-13-643016-2 |oclc=1415988401 |url=https://archive.org/details/openbookpractica00rose |url-access=registration |via=Internet Archive}}

* [[Andrew S. Tanenbaum]], Computer Networks, 4th Edition, (Prentice-Hall, 2002) {{ISBN|0-13-066102-3}}

* {{Citecite book |last=Russell |first=Andrew L. |url=https://books.google.com/books?id=OVpzAwAAQBAJ |title=Open Standards and the Digital Age: History, Ideology, and Networks |date=2014 |publisher=Cambridge University Press |isbn=978-1-139-91661-5 |oclc=881237495}} [{{GBurl |id=OVpzAwAAQBAJ}} Partial preview] at [[Google Books]].▼

* {{Cite book |title= Open Systems Interconnection/Computer Communications Standards and Gossip Explained |publisher= Prentice-Hall |author1= Gary Dickson |author2 = Alan Lloyd |date= July 1992 |isbn= 978-0136401117 }}

* {{cite journal |citeseerxlast=10.1.1.136.9497Zimmermann |first=Hubert |title=OSI Reference Model — The ISO Model of Architecture for Open Systems Interconnection |first=Hubert |last=Zimmermann |journal=IEEE Transactions on Communications |volume=28 |issue=4 | date=April 1980 |pages=425–432 |doi=10.1109/TCOM.1980.1094702 |citeseerx=10.1.1.136.9497 |s2cid=16013989 |issn=0090-6778 |oclc=5858668034}}▼

▲* {{Cite book |last=Russell |first=Andrew L. |url=https://books.google.com/books?id=OVpzAwAAQBAJ |title=Open Standards and the Digital Age: History, Ideology, and Networks |date=2014 |publisher=Cambridge University Press |isbn=978-1-139-91661-5}}

==External links==

{{Sister project links |wikt= |c= |n=no |q=no |s=no |b= |v=}}

{{Commons category}}

*{{cite web |title=Windows network architecture and the OSI model |website=Microsoft Learn |date=2024-02-02 |url=https://learn.microsoft.com/en-us/windows-hardware/drivers/network/windows-network-architecture-and-the-osi-model |access-date=2024-07-12}}

* [https://support.microsoft.com/en-us/kb/103884 Microsoft Knowledge Base: The OSI Model's Seven Layers Defined and Functions Explained]

*{{cite [web |url=http://standards.iso.org/ittf/PubliclyAvailableStandards/s020269_ISO_IEC_7498-1_1994(E).zip |title=ISO/IEC standard 7498-1:1994] - Service definition for the association control service element |website=ISO Standards Maintenance Portal |access-date=2024-07-12}} ([[Portable Document Format|PDF document]] inside [[ZIP (file format)|ZIP archive]]) (requires [[HTTP cookies]] in order to accept licence agreement)

*{{cite [web |url=http://www.itu.int/rec/dologin_pub.asp?lang=e&id=T-REC-X.200-199407-I!!PDF-E&type=items |title=ITU-T Recommendation X.200 (the|website=International sameTelecommunication contentsUnion as|date=1998-06-02 from ISO)]|access-date=2024-07-12}}

* {{cite web |url=https://infchg.appspot.com/usr?at=1263939371 |url-status=dead |archive-url=https://web.archive.org/web/20120526075133/http://infchg.appspot.com/usr?at=1263939371 |archive-date=26 May 2012 |title=INFormation CHanGe Architectures and Flow Charts powered by Google App Engine |website=infchg.appspot.com}}

*{{cite [web |title=Internetworking Technology Handbook |website=docwiki.cisco.com |date=2015-07-10 |url=http://docwiki.cisco.com/wiki/Internetworking_Technology_Handbook Cisco Systems Internetworking Technology Handbook] {{Webarchive|archive-url=https://web.archive.org/web/20150906053851/http://docwiki.cisco.com/wiki/Internetworking_Technology_Handbook |archive-date=6 September 2015-09-06 |url-status=dead}}▼

▲* {{cite journal |citeseerx=10.1.1.136.9497 |title=OSI Reference Model — The ISO Model of Architecture for Open Systems Interconnection |first=Hubert |last=Zimmermann |journal=IEEE Transactions on Communications |volume=28 |issue=4 | date=April 1980 |pages=425–432 |doi=10.1109/TCOM.1980.1094702|s2cid=16013989 }}

*{{cite web |last=EdXD |last2=Saikot |first2=Mahmud Hasan |title=7 Layers of OSI Model Explained |website=ByteXD |date=2021-11-25 |url=https://bytexd.com/osi-model/ |access-date=2024-07-12}}

▲* [http://docwiki.cisco.com/wiki/Internetworking_Technology_Handbook Cisco Systems Internetworking Technology Handbook] {{Webarchive|url=https://web.archive.org/web/20150906053851/http://docwiki.cisco.com/wiki/Internetworking_Technology_Handbook |date=6 September 2015 }}

* [https://bytexd.com/osi-model/ What is the OSI Model – 7 Layers of OSI Model Explained]

* [https://www.cengage.com/c/guide-to-networking-essentials-7e-tomsho/9781305105430PF/ Guide to Networking Essentials, 7th Edition – Cengage]

{{ISO standards}}

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{{DEFAULTSORT:Osi Model}}

[[Category:OSI model| ]]

[[Category:Reference models]]▼

[[Category:Computer-related introductions in 1977]]

[[Category:ISO standards]]

▲[[Category:ReferenceISO/IEC models7498]]

[[Category:ITU-T recommendations]]

[[Category:ITU-T X Series Recommendations]]

[[Category:ISO/IECReference 7498models]]