The OSI, or Open System Interconnection, model defines a networking framework for implementing protocols in seven layers. Control is passed from one layer to the next, starting at the application layer in one station, and proceeding to the bottom layer, over the channel to the next station and back up the hierarchy. The OSI model is not a real network architecture, because it does not really specify the services and protocols each layer should use. It rather describes what the layers must do. Nevertheless, the ISO has developed its own standards for each layer, and this independently of the OSI model, i.e. as does any manufacturer. Regarding its use and implementation, and in spite of an update of the model in 1994, the ...view middle of the document...
TCP/IP dates from the ARPANET network. ARPANET is a telecommunication network developed by the ARPA (Advanced Research Projects Agency), the research agency of the American ministry of defense (the DOD: Department Of Defense). Besides the possibility to interconnect heterogeneous networks, this network was supposed to resist to a possible nuclear war, contrary to the telephone network usually used for telecommunication but considered as too vulnerable. It was then decided that ARPANET would use a standing out and promising new technology: packet switching (datagram mode). It is to meet this context that the TCP and IP protocols were invented in 1974. The ARPA then signed several agreements with manufacturers (especially BBN) and the Berkeley University, where a Unix system was under development, to impose this standard, and that was done.What would the implications be for the industry as a whole to change from using the OSI model to another model such as TCP/IP, etc.?The OSI model will still remain for a while in memories for several reasons. First, it is one of the first main efforts as regards standardization in the area of networks. Manufacturers now tend to do with TCP/IP, but also WAP, UMTS etc. what they were supposed to do with the OSI model, namely to propose standardizations from the beginning. The OSI model will also remain memories for another reason: even if TCP/IP is the model concretely used, people have tendency and use OSI like the current network model of reference. In fact, TCP/IP and OSI have very close structures, and it is especially the effort of standardization of OSI which imposed this general "confusion" between the 2 models. One commonly tends to consider TCP/IP as the real implementation of OSI.
