Internet protocol suite
The Internet protocol suite, commonly known as TCP/IP, is a framework for organizing the communication protocols used in the Internet and similar computer networks according to functional criteria. The foundational protocols in the suite are the Transmission Control Protocol, the User Datagram Protocol, and the Internet Protocol. Early versions of this networking model were known as the Department of Defense 'Internet Architecture Model' because the research and development were funded by the Defense Advanced Research Projects Agency of the United States Department of Defense.
The Internet protocol suite provides end-to-end data communication specifying how data should be packetized, addressed, transmitted, routed, and received. This functionality is organized into four abstraction layers, which classify all related protocols according to each protocol's scope of networking. An implementation of the layers for a particular application forms a protocol stack. From lowest to highest, the layers are the link layer, containing communication methods for data that remains within a single network segment ; the internet layer, providing internetworking between independent networks; the transport layer, handling host-to-host communication; and the application layer, providing process-to-process data exchange for applications.
The technical standards underlying the Internet protocol suite and its constituent protocols are maintained by the Internet Engineering Task Force. The Internet protocol suite predates the OSI model, a more comprehensive reference framework for general networking systems.
History
Early research
The Internet protocol suite has its roots in research and development into computer networks sponsored by the Defense Advanced Research Projects Agency in the late 1960s. After DARPA initiated the pioneering ARPANET in 1969, Steve Crocker established a "Network Working Group" which developed a host-host protocol, the Network Control Program. In the early 1970s, DARPA started work on several other data transmission technologies, including mobile packet radio, packet satellite service, local area networks, and other data networks in the public and private domains. In 1972, Bob Kahn joined the DARPA Information Processing Technology Office, where he worked on both satellite packet networks and ground-based radio packet networks, and recognized the value of being able to communicate across both. In the spring of 1973, Vinton Cerf, at Stanford University, began collaborating with Kahn on the goal of designing the next protocol generation for the ARPANET to enable internetworking. They drew on the experience the international research community, through the International Network Working Group, chaired by Cerf, which included researchers from the ARPANET community, Xerox PARC, the United Kingdom and France.During the summer of 1973, Kahn and Cerf worked out a fundamental reformulation, in which the differences between local network protocols were hidden by using a common internetwork protocol, and, instead of the network being responsible for reliability, as in the existing ARPANET protocols, this function was delegated to the hosts. Cerf and Khan credit several members of INWG with important influences on this design, which was published in May 1974. The first specification of this Transmission Control Program was written in December 1974 by Cerf, Yogen Dalal and Carl Sunshine at Stanford University.
DARPA contracted with BBN Technologies, Stanford University, and University College London to begin developing operational versions of the protocol on several hardware platforms in 1975. Several versions were developed through discussion via the Internet Experiment Note series. Initially, the Transmission Control Program, the precursor to the later protocol suite, provided only a reliable byte stream service, not datagrams. As experience with the protocol grew, collaborators recommended division of functionality into layers of distinct protocols, providing direct access to datagram service. Advocates included Bob Metcalfe, Yogen Dalal and John Shoch at Xerox PARC; Danny Cohen, who needed it for his packet voice work; and Jonathan Postel of the University of Southern California's Information Sciences Institute, who edited the Request for Comments, the technical and strategic document series that has both documented and catalyzed Internet development. Postel stated, "We are screwing up in our design of Internet protocols by violating the principle of layering." Encapsulation of different mechanisms was intended to create an environment where the upper layers could access only what was needed from the lower layers. A monolithic design would be inflexible and lead to scalability issues. In version 4, written in 1978, Postel split the Transmission Control Program into two distinct protocols, the Internet Protocol as a connectionless layer and the Transmission Control Protocol as a reliable connection-oriented service.
The design of the network included the recognition that it should provide only the functions of efficiently transmitting and routing traffic between end nodes and that all other intelligence should be located at the edge of the network, in the end nodes. This end-to-end principle was pioneered by Louis Pouzin and Hubert Zimmermann in the CYCLADES network, based on the ideas of Donald Davies. Using this design, it became possible to connect other networks to the ARPANET that used the same principle, irrespective of other local characteristics, thereby solving Kahn's initial internetworking problem.
Internet Protocol version 4 was installed in the ARPANET in 1983, forming the network layer protocols used on the Internet. Initially referred to as the DOD Internet Architecture Model, together with the Transmission Control Protocol, it became commonly known as TCP/IP.
Early implementation
In 1975, a two-network IP communications test was performed between Stanford and University College London. In November 1977, a three-network IP test was conducted between sites in the US, the UK, and Norway. Several other IP prototypes were developed at multiple research centers between 1978 and 1983.A computer called a router is provided with an interface to each network. It forwards network packets back and forth between them. Originally a router was called gateway, but the term was changed to avoid confusion with other types of gateways.
Adoption
In March 1982, the US Department of Defense declared TCP/IP as the standard for all military computer networking. In the same year, Norway and Peter Kirstein's research group at University College London adopted the protocol. The migration of the ARPANET from NCP to TCP/IP was officially completed on flag day January 1, 1983, when the new protocols were permanently activated.In 1985, the Internet Advisory Board held a three-day TCP/IP workshop for the computer industry, attended by 250 vendor representatives, promoting the protocol and leading to its increasing commercial use. In 1985, the first Interop conference focused on network interoperability by broader adoption of TCP/IP. The conference was founded by Dan Lynch, an early Internet activist. From the beginning, large corporations, such as IBM and DEC, attended the meeting.
IBM, AT&T and DEC were the first major corporations to adopt TCP/IP, this despite having competing proprietary protocols. In IBM, from 1984, Barry Appelman's group did TCP/IP development. They navigated the corporate politics to get a stream of TCP/IP products for various IBM systems, including MVS, VM, and OS/2. At the same time, several smaller companies, such as FTP Software and the Wollongong Group, began offering TCP/IP stacks for DOS and Microsoft Windows. The first VM/CMS TCP/IP stack came from the University of Wisconsin.
Some programmers are notable for early TCP/IP stack implementations. Jay Elinsky and Oleg Vishnepolsky of IBM Research wrote software for VM/CMS and OS/2, respectively. In 1984, Donald Gillies at MIT wrote a ntcp multi-connection TCP which runs atop the IP/PacketDriver layer maintained by John Romkey at MIT in 1983–84. Romkey leveraged this TCP in 1986 when FTP Software was founded. Starting in 1985, Phil Karn created a multi-connection TCP application for ham radio systems.
The spread of TCP/IP was fueled further in June 1989, when the University of California, Berkeley agreed to place the TCP/IP code developed for BSD UNIX into the public domain. Various corporate vendors, including IBM, included this code in commercial TCP/IP software releases. For Windows 3.1, the dominant PC operating system among consumers in the first half of the 1990s, Peter Tattam's release of the Trumpet Winsock TCP/IP stack was key to bringing the Internet to home users. Trumpet Winsock allowed TCP/IP operations over a serial connection. The typical home PC of the time had an external Hayes-compatible modem connected via an RS-232 port with an 8250 or 16550 UART which required this type of stack. Later, Microsoft would release their own TCP/IP add-on stack for Windows for Workgroups 3.11 and a native stack in Windows 95. These events helped cement TCP/IP's dominance over other protocols on Microsoft-based networks, which included IBM's Systems Network Architecture, and on other platforms such as Digital Equipment Corporation's DECnet, Open Systems Interconnection, and Xerox Network Systems.
Nonetheless, for a period in the late 1980s and early 1990s, engineers, organizations and nations were 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.
Formal specification and standards
The technical standards underlying the Internet protocol suite and its constituent protocols have been delegated to the Internet Engineering Task Force.The characteristic architecture of the Internet protocol suite is its broad division into operating scopes for the protocols that constitute its core functionality. The defining specifications of the suite are RFC 1122 and 1123, which broadly outlines four abstraction layers ; the link layer, IP layer, transport layer, and application layer, along with support protocols. These have stood the test of time, as the IETF has never modified this structure. As such a model of networking, the Internet protocol suite predates the OSI model, a more comprehensive reference framework for general networking systems.
A successor Internet Protocol version 6 was developed to address issues such as IPv4 address exhaustion.