The Open Systems Interconnection (usually abbreviated to OSI) was an effort to standardize networking that was started in 1982 by the International Organization for Standardization (ISO), along with the ITU-T. System (from Latin systēma, in turn from Greek sustēma) is a set of entities, real or abstract, comprising a whole where each component interacts with or is related to at least one other component. ... This article or section is in need of attention from an expert on the subject. ... The International Organization for Standardization (ISO) is an international standard-setting body composed of representatives from national standards bodies. ... The ITU Telecommunication Standardization Sector (ITU-T) coordinates standards for telecommunications on behalf of the International Telecommunication Union (ITU) and is based in Geneva, Switzerland. ...

Prior to OSI, according to its proponents, networking was largely vendor-developed and proprietary, with protocol standards such as SNA, Appletalk, NetWare and DECnet. OSI was an industry effort, attempting to get everyone to agree to common network standards to provide multi-vendor interoperability. It was common for large networks to support multiple network protocol suites, with many devices unable to talk to other devices because of a lack of common protocols between them. However while OSI developed its networking standards, TCP/IP came into widespread use on multivendor networks, while below the network layer, both Ethernet and token ring played much the same role. In networking, a communications protocol or network protocol is the specification of a set of rules for a particular type of communication. ... Systems Network Architecture (SNA) is IBMs proprietary networking architecture created in 1974. ... AppleTalk is a proprietary suite of protocols developed by Apple Computer for computer networking. ... NetWare is a network operating system and the set of network protocols it uses to talk to client machines on the network. ... DECnet is a proprietary suite of network protocols created by Digital Equipment Corporation, originally released in 1975 in order to connect two PDP-11 minicomputers. ... The Internet protocol suite is the set of communications protocols that implement the protocol stack on which the Internet runs. ... Ethernet is a large and diverse family of frame-based computer networking technologies for local area networks (LANs). ... Token-Ring local area network (LAN) technology was developed and promoted by IBM in the early 1980s and standardised as IEEE 802. ...

The OSI reference model (which actually predates the OSI protocol work, dating to 1977) was a major advance in the teaching of network concepts. It promoted the idea of a common model of protocol layers, defining interoperability between network devices and software.

However, the actual OSI protocol suite that was specified as part of the project was considered by many to be too complicated and to a large extent unimplementable. Taking the "forklift upgrade" approach to networking, it specified eliminating all existing protocols and replacing them with new ones 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 OSI protocols were specified by committees filled with differing and sometimes conflicting feature requests, leading to numerous optional features; because so much was optional, many vendors' implementations simply could not interoperate, negating the whole effort. Even demands by the USA for OSI support on all government purchased hardware did not save the effort. The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...

Beyond their objections to the Byzantine protocol suite itself, OSI opponents generally contended that the very OSI standardization process represented little more than institutional unwillingness on the part of the ISO and ITU-T to admit that vendor-neutral standards might exist that had not been developed and ratified by their own particular processes. Much bad blood arose between these standards organizations and the IETF, the Internet standards body, as a result of this dispute. The most vitriolic opponents of the OSI suite at times made the further claim that, far from being a "vendor neutral" standard, OSI represented an attempt by minor, or diminishing, players in the networking and computer industries to recover by government fiat market share that they were rapidly losing to the proponents of TCP/IP through fair competition. The Internet Engineering Task Force (IETF) is charged with developing and promoting Internet standards. ...

The OSI approach was eventually eclipsed by the Internet's TCP/IP protocol suite. TCP/IP's pragmatic approach to computer networking and two independent implementations of simplified protocols made it a practical standard. For example, the definition for OSI's X.400 e-mail standards took up several large books, while the Internet e-mail (SMTP) definition took only a few dozen pages in RFC-821. It should be noted, however, that over time there have been numerous RFCs which extended the original SMTP definition, so that its complete documentation finally took up several large books as well. Furthermore, the X.400 standard contained so many optional format choices that early implementations in France and Germany were unable to parse each other's messages. It has been suggested that Internet Protocols be merged into this article or section. ... A protocol stack is a particular software implementation of a computer networking protocol suite. ... In computing, X.400 is an OSI standard developed by the ITU-T (at the time the CCITT) in cooperation with ISO for the exchange of messages, both between people and between software applications. ... Wikipedia does not yet have an article with this exact name. ... Simple Mail Transfer Protocol (SMTP) is the de facto standard for e-mail transmissions across the Internet. ... In internetworking and computer network engineering, Request for Comments (RFC) documents are a series of memoranda encompassing new research, innovations, and methodologies applicable to Internet technologies. ...

Many of the protocols and specifications in the OSI stack are long-gone or have been superseded, such as token-bus media, CLNP packet delivery, FTAM file transfer, and X.400 e-mail. Some still survive, often in significantly simplified forms. The X.500 directory structure still remains with significant usage, mainly because the original unwieldy protocol has been stripped away and effectively replaced with LDAP. IS-IS also continues as a network routing protocol used by larger telecommunications companies, having been adapted for use with the Internet Protocol. Many legacy SONET systems still use TARP (TID Address Resolution Protocol - utilizes CLNP and IS-IS) to translate Target Identifier of a SONET node. Often protocols and specifications in the OSI stack remain in use in legacy systems, unless or until such legacy systems are eventually upgraded, replaced or decommissioned. Token bus is token ring over a virtual ring on a coaxial cable. ... CLNS is an abbreviation of Connectionless Network Service. ... FTAM, an ISO 8571 standard, is an OSI Application layer protocol for File Transfer Access and Management. ... In computing, X.400 is an OSI standard developed by the ITU-T (at the time the CCITT) in cooperation with ISO for the exchange of messages, both between people and between software applications. ... X.500 is the set of ITU-T computer networking standards covering electronic directory services such as white pages, Knowbot and whois. ... In computer networking, the Lightweight Directory Access Protocol, or LDAP (IPA: ), is a networking protocol for querying and modifying directory services running over TCP/IP. A directory is a set of information with similar attributes organized in a logical and hierarchical manner. ... Intermediate system to intermediate system (IS-IS), is a protocol used by network devices (routers) to determine the best way to forward datagrams or packets through a packet-based network, a process called routing. ... The Internet Protocol (IP) is a data-oriented protocol used for communicating data across a packet-switched internetwork. ... Synchronous Optical Networking, commonly known as SONET, is a standard for communicating digital information over optical fiber. ... TARP (Terminal Identifier - Address Resolution Protocol) is a protocol defined in Telecordia (a. ...

The collapse of the OSI project in 1996 severely damaged the reputation and legitimacy of the organizations involved, especially ISO. The worst part was that OSI's backers took too long to recognize and accommodate the dominance of the TCP/IP protocol suite. The financial damage done to Japan and Europe (where internet deployment was delayed by years) is difficult to estimate.

Philosophically, successful standards are generally defacto, based on existing proven technology. The OSI project was criticized for violating that tradition and attempting to design a complex system from scratch by committee.

OSI Model

Further reading

• Marshall T. Rose, The Open Book (Prentice-Hall, Englewood Cliffs, 1990)
• David M. Piscitello, A. Lyman Chapin, Open Systems Networking (Addison-Wesley, Reading, 1993)

See also

• OSI Model, The OSI model
• CMIS, Common Management Information Services

The Open Systems Interconnection Basic Reference Model (OSI Reference Model or OSI Model for short) is a layered, abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnection initiative. ... The Common Management Information Services (CMIS) is part of the OSI body of network standards. ...

References

• ISO 7498:1984 Open Systems Interconnection - Basic Reference Model
• Open System Interconnection Protocols