ABSTRACT
While the OSI reference model has been used to model networked systems and for pedagogic reasons, quite often an ad hoc model, called the TCP/IP or DOD model, is the one that is used for actual implementation of the network protocols and applications. As the legend goes, at one point the OSI network stack was supposed to make the world a better place and everything was supposed to follow the OSI reference model for implementation. However, as is often the case in the real world, the ultimate test for any solution is whether it works or not and how quickly it becomes available to use. Since until the point when the OSI model was conceived, while there was a large number of proprietary network solutions such as IBM SNA, DEC Net, Burroughs BNA (Chapin), etc., the reality was that the TCP/IP-based network model proposed and implemented by various research and academic institutions was taking hold and was expanding its reach. So when the OSI model was developed, and people tried to actually implement OSI model-based protocols, it was found to be quite slow in actual implementations, and thus the practicality of TCP/IP networks won the day and TCP/IP became the ad hoc standard for the networking world.
