The Internet model was designed as the solution to a practical engineering problem. The OSI model, on the other hand, was proposed as a theoretical approach and also as a first phase in the evolution of computer networks. Therefore, the OSI model is easier to understand, but the TCP/IP model is the one that is actually used. It is helpful to understand OSI before learning about TCP/IP, as the same principles apply, but they are easier to understand in OSI.

TCP/IP is the successor to the Network Control Program (NCP), with which ARPANET operation began, and was first presented with RFC 791,[3]​ RFC 792[4]​ and RFC 793[5]​ in September 1981. By November of the same year, the definitive transition plan was presented in RFC 801,[6]​ and January 1, 1983 was marked as “Flag Day”.

The family of Internet protocols were the result of work carried out by the “Defense Advanced Research Projects Agency”: DARPA, in the early 1970s. After the construction of the pioneering ARPANET in 1969, DARPA began working on a large number of data transmission technologies. In 1972, Robert E. Kahn was hired by DARPA's Information Processing Techniques Office, where he worked on packet communication by satellite and radio waves, recognizing the important value of communication in these two ways. In the spring of 1973, Vint Cerf, developer of the ARPANET protocol, Network Control Program, joined Kahn with the goal of creating an open interconnection architecture and thus designing the next generation of ARPANET protocols. Kahn and Cerf were awarded the Presidential Medal of Freedom on November 10, 2005 for their contribution to American culture.[7]​.

By the summer of 1973, Kahn and Cerf had achieved a fundamental remodeling, where the differences between network protocols were hidden using a communications protocol and in addition, the network was no longer responsible for the reliability of the communication, as was the case in ARPANET, it was the host that was responsible. Cerf recognized the merit of Louis Pouzin, creator of the CYCLADES network, since his work was greatly influenced by the design of this network.

With the role that networks played in the communication process reduced to a minimum, it became a real possibility to communicate with different networks, regardless of the characteristics they had. There is a popular saying about TCP/IP, which was the final product developed by Cerf and Kahn, that it can work even between “two cans connected by a string.” In fact there is even an implementation using carrier pigeons, IP over carrier pigeons, which is documented in RFC 1149.[8]​[9]​.

A computer called router (a name that was later changed to gateway, gateway or gateway to avoid confusion with other types of gateway), is equipped with an interface for each network, and sends datagrams back and forth between them. The requirements for these routers are defined in RFC 1812.[10]​.

This idea was executed in more detail by Cerf's Stanford research group "Stanford (California)") during the period 1973 to 1974, resulting in the first TCP specification (Request for Comments 675).[11] DARPA was then contracted by BBN Technologies, Stanford University, and University College London (UCL) to develop operational versions of the protocol on different hardware platforms. Four different versions were thus developed: TCP v1, TCP v2, a third divided into two: TCP v3 and IP v3, in the spring of 1978, and then version TCP/IP v4 was stabilized: the standard protocol that is still used on the Internet.

In 1975, the first test of communication between two networks with TCP/IP protocols was carried out between Stanford University and UCL. In 1977 another communication test was carried out between three different networks with locations in the United States, the United Kingdom and Norway. Several different prototypes of TCP/IP protocols were developed in multiple research centers between 1978 and 1983. The complete migration of the ARPANET network to TCP/IP officially concluded on January 1, 1983, when the protocols were permanently activated.[12]​.

In March 1982, the United States Department of Defense declared TCP/IP the standard for communications between military networks.[13] In 1985, the Internet Architecture Board (IAB) hosted a three-day "Workshop" attended by 250 tradesmen. This served to promote the protocol, which contributed to an increase in its commercial use.

The Internet protocol family can be described by analogy with the OSI (Open System Interconnection) model, which describes the levels or layers of the protocol stack, although in practice it does not correspond exactly to the Internet model. In a protocol stack, each level solves a series of tasks related to data transmission, and provides a well-defined service to higher levels. The higher levels are those closest to the user and deal with more abstract data, leaving the lower levels with the task of translating the data so that it is physically manipulable.

The Internet model was designed as the solution to a practical engineering problem. The OSI model, on the other hand, was proposed as a theoretical approach and also as a first phase in the evolution of computer networks. Therefore, the OSI model is easier to understand, but the TCP/IP model is the one that is actually used. It is helpful to understand OSI before learning about TCP/IP, as the same principles apply, but they are easier to understand in OSI.

TCP/IP is the successor to the Network Control Program (NCP), with which ARPANET operation began, and was first presented with RFC 791,[3]​ RFC 792[4]​ and RFC 793[5]​ in September 1981. By November of the same year, the definitive transition plan was presented in RFC 801,[6]​ and January 1, 1983 was marked as “Flag Day”.

The family of Internet protocols were the result of work carried out by the “Defense Advanced Research Projects Agency”: DARPA, in the early 1970s. After the construction of the pioneering ARPANET in 1969, DARPA began working on a large number of data transmission technologies. In 1972, Robert E. Kahn was hired by DARPA's Information Processing Techniques Office, where he worked on packet communication by satellite and radio waves, recognizing the important value of communication in these two ways. In the spring of 1973, Vint Cerf, developer of the ARPANET protocol, Network Control Program, joined Kahn with the goal of creating an open interconnection architecture and thus designing the next generation of ARPANET protocols. Kahn and Cerf were awarded the Presidential Medal of Freedom on November 10, 2005 for their contribution to American culture.[7]​.

By the summer of 1973, Kahn and Cerf had achieved a fundamental remodeling, where the differences between network protocols were hidden using a communications protocol and in addition, the network was no longer responsible for the reliability of the communication, as was the case in ARPANET, it was the host that was responsible. Cerf recognized the merit of Louis Pouzin, creator of the CYCLADES network, since his work was greatly influenced by the design of this network.

With the role that networks played in the communication process reduced to a minimum, it became a real possibility to communicate with different networks, regardless of the characteristics they had. There is a popular saying about TCP/IP, which was the final product developed by Cerf and Kahn, that it can work even between “two cans connected by a string.” In fact there is even an implementation using carrier pigeons, IP over carrier pigeons, which is documented in RFC 1149.[8]​[9]​.

A computer called router (a name that was later changed to gateway, gateway or gateway to avoid confusion with other types of gateway), is equipped with an interface for each network, and sends datagrams back and forth between them. The requirements for these routers are defined in RFC 1812.[10]​.

This idea was executed in more detail by Cerf's Stanford research group "Stanford (California)") during the period 1973 to 1974, resulting in the first TCP specification (Request for Comments 675).[11] DARPA was then contracted by BBN Technologies, Stanford University, and University College London (UCL) to develop operational versions of the protocol on different hardware platforms. Four different versions were thus developed: TCP v1, TCP v2, a third divided into two: TCP v3 and IP v3, in the spring of 1978, and then version TCP/IP v4 was stabilized: the standard protocol that is still used on the Internet.

In 1975, the first test of communication between two networks with TCP/IP protocols was carried out between Stanford University and UCL. In 1977 another communication test was carried out between three different networks with locations in the United States, the United Kingdom and Norway. Several different prototypes of TCP/IP protocols were developed in multiple research centers between 1978 and 1983. The complete migration of the ARPANET network to TCP/IP officially concluded on January 1, 1983, when the protocols were permanently activated.[12]​.

In March 1982, the United States Department of Defense declared TCP/IP the standard for communications between military networks.[13] In 1985, the Internet Architecture Board (IAB) hosted a three-day "Workshop" attended by 250 tradesmen. This served to promote the protocol, which contributed to an increase in its commercial use.