5 The Architecture of the Internet—A Historical Perspective

My introduction to architecture in chapter 3 was abstract. In this chapter, I use the architecture of the current Internet as a more concrete example. In 1988, I wrote a paper titled “The Design Philosophy of the DARPA Internet Protocols” (Clark, 1988), which tried to capture the requirements that have shaped the design of the Internet and the basic design decisions that had been made in meeting these requirements—what I might now call architecture but then called design philosophy. It is now more than 25 years since that paper was published, and looking back at that paper is a way to get started with a less abstract, more concrete example of network architecture.