Today's networks and internetworks need to connect end system and intermediate systems manufactured by a variety of vendors. The complexity increases when we realize that internetworking is not only the connecting of end systems or intermediate systems, but also the need to force different application programs to communicate with one another. In other words, real communication is between one application program on one end system and another application program on another end system. This means the end for harmony: the application programs should understand each other, the end system should coordinate, the intermediate system should facilitate the routing of information, the transmission media should be able to transmit the information with the rate and accuracy needed by end systems, and so on. The task is very complex.The complexity is due to the fact that some part of the system should handle a subset of the task and others another subset. An end system cannot be responsible for carrying information from one place to another; this should be done by a transmission medium such as a cable or the air. Switching and routing of data are not functions of an end system; these tasks should be done by some intermediate systems.
Layered Architecture
Open System Interconnection(OSI) Model
TCP/IP Protocol Suite
IEEE Standards