What is the architecture of the Internet?
A short reflection should convince you that the fundamental, unifying organization of the Internet is neither its physical structure nor its software structure. Both are quite volatile. Rather, the enduring, organizing elements of the Internet are its protocols, especially IP, and its key routing concepts. From IP and the routing concepts, one can infer a great deal about possible network structures, limitations on possible services, and much more. However, from the momentary physical, or even software, structure, one can learn very little about the fundamental nature of the Internet. This exercise can be repeated for any enterprise information system, for the World Wide Web and many other systems. Our conclusion is that architectures are often, increasingly, non-physical and that the definition of architecture should respect and evoke that realization. Note that nothing in the definition precludes its application to systems where structural concerns dominate the architecture, but we c
