The World Wide Web is a major distributed system, with millions of users. A site may become a web host by running an HTTP server. While web clients are typically users with a browser, there are many other “user agents” such as web spiders, web application clients, and so on.
The Web is built on top of the HTTP (Hypertext Transport Protocol), which is layered on top of TCP. HTTP has been through four publically available versions. Version 1.1 (the third version) is the most commonly used, but there is expected to be a rapid transition to HTTP/2 and this is now at over 10% of the current traffic.
This chapter ...
