HTML and CSS Reference
How does information get transferred from the Web server to the Web browser? Clients
(such as Web browsers) and servers (such as a Web server) exchange information
through the use of communication protocols such as HTTP, TCP , and IP .
Protocols are rules that describe how clients and servers communicate with each other
over a network. There is no single protocol that makes the Internet and Web work—a
number of protocols with specific functions are needed.
File Transfer Protocol (FTP) is a set of rules that allow files to be exchanged
between computers on the Internet. Unlike HTTP, which is used by Web browsers to
request Web pages and their associated files in order to display a Web page, FTP is
used simply to move files from one computer to another. Web developers commonly
use FTP to transfer Web page files from their computers to Web servers. FTP is also
commonly used to download programs and files from other servers to individual
Most of us take e-mail for granted, but there are two servers involved in its smooth
functioning—an incoming mail server and an outgoing mail server. When you send
e-mail to others, Simple Mail Transfer Protocol (SMTP) is used. When you receive
e-mail, Post Office Protocol (POP; currently POP3 ) and Internet Message Access
Protocol (IMAP) can be used.
HTTP is a set of rules for exchanging files such as text, graphic images, sound,
video, and other multimedia files on the Web. Web browsers and Web servers usu-
ally use this protocol. When the user of a Web browser requests a file by typing a
Web site address or clicking a hyperlink, the browser builds an HTTP request and
sends it to the server. The Web server in the destination machine receives the request,
does any necessary processing, and responds with the requested file and any associ-
ated media files.
Transmission Control Protocol/Internet Protocol (TCP/IP) has been adopted as the offi-
cial communication protocol of the Internet. TCP and IP have different functions that
work together to ensure reliable communication over the Internet.