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 Layer 2-16
Application Layer 2-16 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 cleartext passwds libraries,.which“talk” sent into socket to TCP traverse Internet in SSL socket API cleartext cleartext passwds SSL sent into socket provides encrypted traverse Internet TCP connection encrypted data integrity ÷See Chapter7 *end-point authentication Application Layer 2-17
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, which “talk” to TCP SSL socket API cleartext passwds sent into socket traverse Internet encrypted See Chapter 7 Application Layer 2-17
Chapter 2:outline 2.1 principles of 2.6 P2P applications network 2.7 socket applications programming with app architectures UDP and TCP app requirements 2.2 Web and HTTP 2.3 FTP 2.4 electronic mail ■SMTP,POP3, IMAP 2.5 DNS Application Layer 2-18
Application Layer 2-18 Chapter 2: outline 2.1 principles of network applications app architectures app requirements 2.2 Web and HTTP 2.3 FTP 2.4 electronic mail SMTP, POP3, IMAP 2.5 DNS 2.6 P2P applications 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 Layer 2-19
Application Layer 2-19 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 HTTP request server protocol)and HTTP response running 'displays”Web Apache Web objects server server:Web server sends (using HTTP iphone running protocol）objects in Safari browser response to requests Application Layer 2-20
Application Layer 2-20 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 HTTP re H quest TTP response HTTP request HTTP response