Pouzin draws on his considerable experience to show how independent networks of computing systems can be connected to one another. Some networks are designed around a computer vendor’s architecture; others reflect the needs of a single application area; still others are designed for economical use of transmission facilities. As a result, messages passing from one network into another may have to be translated, reformatted, readdressed, and resynchronized at each network boundary.

Pouzin outlines a number of potential solutions to these problems. Most of the solutions are clumsy and expensive, frequently cancelling out some efficiencies of a subnetwork in order to handle foreign messages. The straightforward solution would be a single architecture covering all subnetworks. Unfortunately, as Pouzin points out, such a standard architecture runs into severe political, jurisdictional, and economic obstacles. However, internetworking is growing in importance and there are signs that the methods of implementing the connections will become reasonably efficient. Examples of the trend can be seen in the interconnection of independent automated teller machine networks, the standardization of local networks, and the introduction of the ISDN (Integrated Services Digital Network) in telephone transmission. None of these address all the problems of internetworking, but they reduce the number of variables and simplify the remaining implementation problems.