The compositional architecture of the internet

IN 1992, THE explosive growth of the World Wide Web began. The architecture of the Internet was commonly described as having four layers above the physical media, each providing a distinct function: a “link” layer providing local packet delivery over heterogeneous physical networks, a “network” layer providing best-effort global packet delivery across autonomous networks all using the Internet Protocol (IP), a “transport” layer providing communication services such as reliable byte streams (TCP) and datagram service (UDP), and an “application” layer. In 1993, the last major change was made to this classic Internet architecture;¹¹ since then the scale and economics of the Internet have precluded further changes to IP.¹².