Designing an Internet

by David D. Clark

The World Wide Web is specified by a set of protocols that allow a Web client (often called a browser) to connect to a Web server.5 A Web server (a particular kind of end node attached to the Internet) stores Web pages and makes them available for retrieval on request. The pages have names called URLs (uniform resource locators). The first part of a URL is actually a DNS name, and a browser uses the DNS system to translate that name into the address of the intended Web server. The browser then sends a message to that Web server asking for the page. URLs are disseminated in various ways so that potential readers can discover them. They also form the basis of cross-references or links from one Web page to another; when a user positions the mouse over a link and clicks it, the browser uses the matching URL to retrieve the indicated page. There is a longer discussion of URLs in chapter 8.