Internet apps:application,transport protocols 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 (e.g.,YouTube), TCP or UDP RTP [RFC 1889] Internet telephony SIP,RTP,proprietary (e.g.,Skype) TCP or UDP Application Layer2-16
Application Layer2-16 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 (e.g., YouTube), RTP [RFC 1889] SIP, RTP, proprietary (e.g., Skype) underlying transport protocol TCP TCP TCP TCP TCP or UDP TCP or UDP
Securing TCP TCP UDP SSL is at app layer no encryption apps use SSL libraries,that“talk”to cleartext passwds sent into socket TCP traverse Internet in cleartext SSL socket APl SSL cleartext passwords sent into socket provides encrypted TCP connection traverse Internet encrypted ■data integrity ■see Chapter8 end-point authentication Application Layer2-17
Securing TCP TCP & UDP ▪ no encryption ▪ cleartext passwds sent into socket traverse Internet in cleartext SSL ▪ provides encrypted TCP connection ▪ data integrity ▪ end-point authentication SSL is at app layer ▪ apps use SSL libraries, that “talk” to TCP SSL socket API ▪ cleartext passwords sent into socket traverse Internet encrypted ▪ see Chapter 8 Application Layer2-17
Chapter 2:outline 2.I principles of network 2.5 P2P applications applications 2.6 video streaming and 2.2 Web and HTTP content distribution 2.3 electronic mail networks ·SMTP,POP3,IMAP 2.7 socket programming 2.4 DNS with UDP and TCP Application Layer2-18
Application Layer2-18 Chapter 2: outline 2.1 principles of network applications 2.2 Web and HTTP 2.3 electronic mail • SMTP, POP3, IMAP 2.4 DNS 2.5 P2P applications 2.6 video streaming and content distribution networks 2.7 socket programming with UDP and TCP
Web and HTTP First,a review... 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,e.g., www.someschool.edu/someDept/pic.gif host name path name Application Layer2-19
Application Layer2-19 Web and HTTP First, a review… ▪ 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, e.g., www.someschool.edu/someDept/pic.gif host name path name
HTTP overview HTTP:hypertext transfer protocol Web's application layer protocol PC running HTTP request client/server model Firefox browser HTTP ·client:browser that esponse requests,receives, (using HTTP protocol) server and "displays"Web HTTP request running objects HTTP response Apache Web ·server:.Veb server server sends(using HTTP protocol)objects in iPhone running response to requests Safari browser Application Layer2-20
Application Layer2-20 HTTP overview HTTP: hypertext transfer protocol ▪ Web’s application layer protocol ▪ client/server model • client: browser that requests, receives, (using HTTP protocol) and “displays” Web objects • server: Web server sends (using HTTP protocol) objects in response to requests PC running Firefox browser server running Apache Web server iPhone running Safari browser