Internet communication has become a fundamental part of life. The World Wide Web contains information about such diverse subjects as atmospheric conditions, crop production, stock prices, airline traffic etc. Groups establish electronic mail so they can share information of common interest. Professional colleague's exchange business correspondence electronically and even relative's personal greetings.
Unfortunately, most networks are designed for a particular purpose. Each enterprise chooses hardware technology appropriate for specific needs and budget. More important, it is impossible to engineer a universal network from a single network technology because no single network suffices for all users. Some groups need high-speed networks to connect computers in a single building. Low cost technologies that fill the need cannot span large geographical distances. Other groups settle for slower speed networks that connect machines thousands of miles apart.
For over two decades, a new technology has evolved that make it possible to interconnect many disparate physicals networks and make them functional as a coordinated unit. The technology is called internetworking accommodates multiple diverse underlying hardware technologies by providing a way to interconnect heterogeneous networks and a set of communication conventions that makes them inter operate. The Internet technology hides the details of network hardware and permits computers to communicate independent of their physical network connections.
The Internet technology is an example of open system interconnection. It's called open because unlike proprietary communication systems available from one specific vendor, the specifications are publicly available. Thus any one can build the software needed to communicate across an Internet. More important, the entire technology has been designed to foster communication among machines with diverse hardware architecture, to use almost any packet switched network hardware to accommodate a wide variety of applications and to accommodate multiple computer operating systems.
