Application Layer

Introduction
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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

Network applications are the raisons d'etre of a computer network.  Over the past 35 years, numerous ingenious and wonderful based applications have been created.  These applicatons include the classic text-based applications that became popular in the 1980's: text e-mail, remote access to computers, file transfers, newsgroups, and text chat.

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They include the killer application of the mid-1990's: the Web. They include many multimedia applications, such as streaming video, Internet radio, Internet telephony, and video conferencing.  And they include the two killer application introduced at the end of the millennium--instant messaging with contact lists, and peer-to-peer (P2P) file sharing.