One of the key factors contributing to the success of the Internet is an architecture that is well suited to rapid and substantial changes in usage. The Internet originally descended from the “Arpanet” in the late 1960s, a network connecting universities and government institutions for research purposes and enabling remote sites to quickly access information from each other and execute programs on distant computers. The World Wide Web commercialized the Internet in the 1990s, making it available beyond the academic and government communities. More recently, the higher speeds of third-generation cellular networks in conjunction with advances in smart phone user interfaces are enabling the widespread use of the Internet on mobile and portable devices. Today, the Internet is the most important communications medium other than the telephone network, serving nearly 2 billion users .
Despite this staggering evolution, the Internet still retains most of its early architectural properties. This chapter describes Internet architecture, including basic Internet topology, Internet exchange points (IXPs), the history of IXPs', and the principles of Internet relationships and Internet service providers (ISPs).
The Internet is a collection of routers, interconnected by links, that forward data from a source to a destination. Computers, or nodes, exchange data across the Internet by splitting the data into portions, or so-called packets