Internet apps: application, transport protocl Application Underlying Application layer protocol transport protocol e-mail SMTP [RFC 2821 TCP remote terminal access Telnet [RFC 854 TCP Web htTp [rFc 2616]Tcp file transfer FTP [RFC 959 TCP streaming multimedia Http (eg Youtube), TcP or Udp RTP TRFC 1889 Internet telephony SIP, RTP, proprietary (e.g, Skype) typically UDP uct by Weiteng Sun chapter 2-application layer 16/73
Introduct by Weifeng Sun chapter2- application layer 16/73 Internet apps: application, transport protocols Application e-mail remote terminal access Web file transfer streaming multimedia Internet telephony Application layer protocol SMTP [RFC 2821] Telnet [RFC 854] HTTP [RFC 2616] FTP [RFC 959] HTTP (eg Youtube), RTP [RFC 1889] SIP, RTP, proprietary (e.g., Skype) Underlying transport protocol TCP TCP TCP TCP TCP or UDP typically UDP
Chapter 2 application layer 2. 1 Principles of 2.6 P2P applications network 2.7 Socket applications programming with app architectures app requirements 2. 8 Socket 2.2 weB and Http programming with 2. 4 Electronic Mail UDP SMTP POP3, IMAP 2.5 DNS uct by Weifeng Sun chapter 2-application layer 17/73
Introduct by Weifeng Sun chapter2- application layer 17/73 Chapter 2: Application layer • 2.1 Principles of network applications – app architectures – app requirements • 2.2 Web and HTTP • 2.4 Electronic Mail – SMTP, POP3, IMAP • 2.5 DNS • 2.6 P2P applications • 2.7 Socket programming with TCP • 2.8 Socket programming with UDP
Web and Http First some jargon Web page consists of objects Ob ject can be html file jPeg image Java applet, audio file, Web page consists of base htMl-file which includes several referenced ob jects Each object is addressable by a URL Example URL Www. someS chool.edu/some Dept/pic. gif host name path name uct by Weiteng Sun chapter 2-application layer 18/73
Introduct by Weifeng Sun chapter2- application layer 18/73 Web and HTTP First some jargon • Web page consists of objects • Object can be HTML file, JPEG image, Java applet, audio file,… • Web page consists of base HTML-file which includes several referenced objects • Each object is addressable by a URL • Example URL: www.someschool.edu/someDept/pic.gif host name path name
Http overview Uses TCp Http is"stateless" PC running 7 Explo xp e Protocols that maintain state"are complex e Server Apache Web server Mac running Navigator uct by Weiteng Sun chapter2-application layer 19/73
Introduct by Weifeng Sun chapter2- application layer 19/73 HTTP overview Uses TCP HTTP is “stateless” Protocols that maintain “state” are complex! PC running Explorer Server running Apache Web server Mac running Navigator
Http connections Nonpersistent Http Persistent Http At most one ob ject multiple ob jects is sent over a tcp can be sent over connection single TCp connection between client and server uct by Weifeng Sun chapter 2-application layer 20/73
Introduct by Weifeng Sun chapter2- application layer 20/73 HTTP connections Nonpersistent HTTP • At most one object is sent over a TCP connection. Persistent HTTP • Multiple objects can be sent over single TCP connection between client and server