TCP/IP architecture

TCP/IP is an acronym for two protocols used by many companies marketing network equipment. These two protocols, IP (Internet Protocol) and TCP (Transmission Control Protocol), form the network layer and the transport layer respectively, and were developed to interconnect the various heterogeneous networks used by American defense forces. The basic idea is simple: to make these networks homogeneous by imposing a common protocol, the IP protocol. In this way, to pass from one subnetwork to another, it is necessary to use the IP protocol, which manages routing.

In fact, the acronym TCP/IP stands for much more than just the two protocols developed to interconnect sub-networks; it designates an entire environment that includes, of course, the TCP and IP protocols, but also the applications that have been developed on top of these two protocols: SMTP (Simple Mail Transport Protocol) e-mail, FTP (File Transfer Protocol) file transfer, access to WWW (World Wide Web) information databases, and so on.

The success of this environment initially stems from its use in the Internet network, and to fully understand its foundations, we need to go back to the basic structures of this Internet network.

The Internet is a network of networks developed by the U.S. Department of Defense in the late 70s and early 80s to interconnect the department's various computing machines. The solution was to develop a common protocol that all connected networks and machines must have. This common protocol is IP (Internet Protocol). The interconnected networks, which we call sub-networks, can be any number of things. All they have to do is carry IP packets from one end to the other, i.e. packets that comply with IP protocol specifications. These sub-networks can be X.25, Ethernet, frame relay, ATM, and so on. The IP protocol is the basic protocol required in the Internet environment.

The Internet was created to transport computer data, and the sub-networks are of various types, typically using packet switching adapted to asynchronous applications.

As we shall see, the IP protocol is very simple, at least in its first version, and uses a routing technique. In other words, packets from the same user are independent of each other and are routed by the nodes managing the IP protocol. As a result, two packets from the same user can take different paths.

The evolution of networks using TCP and IP protocols is dictated by the prospect of transporting multimedia applications rather than just computer data. To achieve this, first-generation protocols will have to be replaced by a new generation, capable of supporting the synchronization essential for routing isochronous applications such as speech or video....