Application Layer

2.2 The Web and HTTP
Home
Introduction
2.1 Principles of Network Applications
2.1.1 Network Application Architectures
2.1.2 Processes Communcating
2.1.3 Application-Layer Protocols
2.1.4 What Services Does an Application Need?
2.1.5 Services Provided by the Internet Transport Protocols
2.2 The Web and HTTP
2.2.1Overview of HTTP
2.2.2 Nonpersistent and Persistent Connections
2.2.3 HTTP Message Format
2.2.4 User-Server Ineraction: Cookies
2.2.5 HTTP Content
2.2.6 Web Caching
2.2.7 The Conditional GET
2.3 File Transfer: FTP
2.3.1 FTP Commands and Replies
2.4 Electronic Mail in the Internet
2.4.1 STMP
2.4.2 Comparison with HTTP
2.4.3 Mail Message Formats and MIME
2.4.4 Mail Access Protocols
2.5 DNS--The Internet's Directory Service
2.5.1 Services Provided by DNS
2.5.2 Overview of How DNS Works
2.5.3 DNS Records and Messages
2.6 P2P File Sharing
2.7 Socket Programming with TCP
2.7.1 Socket Programming with TCP
2.7.2 An Example Client/Server Application in Java
2.8 Socket Programming with UDP

2.2.4 User-Server Interaction: Cookies

Cookies allow sites to keep track of users.  Although not all sites use cookies, most major portal, e-commerce, and advertising sites make extensive use of cookies.
 
Cookie technology has four componets: (1) a cookie header line in the HTTP response message; (2) a cookie header line in the HTTP request message; (3) a cookie file kept on the user's end system and managed by the user's browser; (4) a back-end database at the Web site.
 
Although cookies often simplify the Internet shopping experience for the user, they remain highly controversial because they can also be considered as an infringement ona user's privacy.