With the development of individual computer networks comes the need to interconnect them. Network designers are faced with heterogeneity of networks just they were previously faced with heterogeneity of computers within a single network.This paper shows that similar structuring techniques,namely multiplexing, switching, cascading, wrapping and layering, can be applied, and that a set of simple principles can be derived which facilitate greatly the design of the interconnection of computer networks.

These simple principles are applied to the analysis of some typical examples of network interconnection problems, in areas of addressing, routing, non-equivalent communication services, error control,flow control and terminal access.Similar principles could be applied to some unresolved issues in computer network interconnection, such as congestion control or administrative functions. It is finally claimed that final objective of network interconnection studies are to determine the set of international standards which are required to make network interconnection straightforward in the near future.

Data processing is gradually evolving from its original model,to networking and distributed processing.Computers have been linked into individual networks to satisfy needs of individual organizations. Now, networks must be interconnected to cater to inter-organizational relationships.Even though this requirement for interconnection of computer networks was identified early, it is only recently that the problem has been widely recognized..A set of simple rules can tremendously help to analyse specific interconnection problems, as well as improve potential interconnectability of a network through proper design choices.First question to be raised is "What is specific network interconnection, as opposed to building single network ?".Basically, an interconnected set of networks can be considered from an external (user's) point of view and from an internal (designer's) point of view.From a user's viewpoint, an interconnected set of networks is not different from a single network.

In particular, two identical networks can usually be integrated into a single bigger one. In addition, it is essential to preserve freedom in the design of future computer networks,but still be able to interconnect them with existing ones. In other words, the question is "how to interconnect heterogeneous networks" rather than "how to build a world wide homogeneous network".Before being faced with the constraint of interconnecting heterogeneous networks, network designers have been faced with the problem of interconnecting heterogeneous computers.

Conclusion

Interconnection of computer networks is a complex problem and largely still an open question. However, it has been solved satisfactorily in a number of cases, permitting partial interconnection .Experience shows that a set of simple rules can be applied to analyze network interconnection problems. Of course, these simple principles are not sufficient, and practical experience is still essential. It could reasonably be expected that the same type of techniques could be applied to the remaining network interconnection issues, but this still to be tried. The final objective of all present studies and experiments in network interconnection should be to determine which common properties networks must exhibit to make them readily interconnectable, and to establish them as international standards.Common levels of services, expandability of network addresses to global addresses, common layering structure, common protocols on top of common services are such candidates for standardization.