2.6 Distributed and network architectures

Not all systems consist of one computer. Modern systems used in academia, business, and government are more frequently being interconnected to form information-sharing systems or multiprocessing systems. These networks and computer interconnects are constructed by providing yet another input and output path for the computer to receive or send information. The input and output unit and controller for the network peripheral device are called a network interface unit (NIU) or processor bus. The function of these interface units and buses is to provide a seamless (typically) way for one computer to interact with another as if they were located in the same machine. Networks come in a variety of configurations for example, the NIUs can be configured as a single global bus topology, as a central star or hub topology, as a ring topology, or as some hybrid. When interconnected in such ways over a relatively small distance (a single floor, building, or small organization), we have what is referred to as a local area network, or LAN. A LAN is used to interconnect a subunit of some larger organization or to interconnect a small number of users who need to share information. Beyond a LAN we have wide area networks and the Internet. Multiprocessor systems are interconnected using similar concepts. They are combined using shared buses or shared memory.