Chapter 40 Computer-network examples 511

Technically, the goals of the network are (1) to make a user (T) at any site behave as though it were a T at another site and (2) to let a C at any site use a C at another site for load, program, and data sharing. To each site has been added a special C('Interface Message Processor/IMP). The C('IMP) has been designed by the creators of the network, and it provides the communality that will permit the network to function. One constraint in the network design is to make only small perturbations to the larger host computers. The C('IMP) is responsible for network messages among other nodes (i.e., to their C('IMP)'s) and for the interface between the network and the C (or N) at the local site. The local computer C('Host)-C('IMP) interface is shown in Figs. 7b and 7c