1. How Web Servers and The Internet Work The Basic Process

2. You’re sitting at your computer and cussing, because Tulloss has once again posted CIS 345 info at the last minute and you need to download it You type in the URL www.homepages.dsu.edu/tullossb/default.htm Up pops my page, but how did it happen?

3. The Basic Process

4. The browser broke the URL into 3 parts The protocol (http) – what’s http? The server name (www.homepages.dsu.edu)www.homepages.dsu.edu The folder where it resides (tullossb) And finally the filename (default.htm)

5. The Basic Process The browser communicated with a name server to translate the server name into an Internet Protocol (IP) address, which it uses to connect to the server machine

6. The Basic Process The browser then formed a connection to the server at the IP address on port 80 What’s a port? Basically, a value used to distinguish among the multiple applications that may have connections with a single host E.g. www = 80, ftp = 21

7. The Basic Process Following the http protocol, the browser sent a GET request to the server, asking for the file default.htm located at www.homepages.dsu.edu/tullossb www.homepages.dsu.edu/tullossb

8. The Basic Process The server then sent the HTML text for the Web page to the browser Finally, the browser read the HTML tags and formatted the page onto your screen