8_WebDhcpNtpNat_spring10

8_WebDhcpNtpNat_spring10 - Chapter 8 The Web, DHCP, NTP and...

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TCP/IP Essentials A Lab-Based Approach Chapter 8 Chapter 8 The Web, DHCP, The Web, DHCP, NTP and NAT NTP and NAT Spring 2010
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Polytechnic Institute of NYU Slide 2 zjzhao World Wide Web (WWW) •The first WWW browser was written by Tim Berners-Lee in 1990. •The popularity of WWW resulted in the exponential growth for the Internet. •In WWW, information is typically provided as Hyper Text Markup Language (HTMP) files (web pages). •WWW resources are specified by Uniform Resource Locators (URL) .
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Polytechnic Institute of NYU Slide 3 zjzhao Uniform Resource Locator (URL) A standard scheme for compactly identifying any document on any Web server Components: •A protocol name : http, rtp, rtsp :// •A server domain name or server IP address • A path to a resource ( an HTML file or a CGI script) http://today@poly.edu:999/ee-dept/event.html Service Type : http, telnet, ftp, gopher, … System Name Port Number : specified if non- default port is used File Name Path Name
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Polytechnic Institute of NYU Slide 4 zjzhao HyperText Transfer Protocol (HTTP) •Application layer protocol •Distributes information in the WWW •Based on the client/server architecture – HTTP client (web browser): sends a request to a server for a file – HTTP server (web server): well-known port number 80, responds with the requested file if it is available – A single TCP connection is used Network IP TCP web browser HTTP Network IP TCP web server HTTP request response
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Polytechnic Institute of NYU Slide 5 zjzhao HTTP Messages English-based and flexible, not code-based as lower layer protocols •Components of an HTTP message: –A start-line –Optional headers, each has a header name and a value –A blank line (a “\r\n” only) –The requested file or other data in an HTTP response.
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Polytechnic Institute of NYU Slide 6 zjzhao HTTP Request Message Request Line: Request Type URL HTTP version Optional Headers Header name Value A blank line The Request Type defines methods in messages GET, HEAD – retrieve a full document or some info about a document from the server PUT, PATCH – provide a new/replacement document or a list of difference to implement in an existing document to the server COPY, MOVE, DELETE – copy, move, or delete a document ……
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Polytechnic Institute of NYU Slide 7 zjzhao HTTP Response Message Status Line: • HTTP version • Status Code • Status phrase Optional Headers • Header name •Va lue A blank line Data Body • The Status Code is similar to those in the FTP and the SMTP protocol with 3 digits • The Status Phrase explains the status code such as continue, switching, OK, accepted, no content, multiple choices, bad request, unauthorized,
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Polytechnic Institute of NYU Slide 8 zjzhao HTTP TCP Connections • The client first establishes a TCP connection to the server before an HTTP request • The server may terminate the TCP connection after the HTTP
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8_WebDhcpNtpNat_spring10 - Chapter 8 The Web, DHCP, NTP and...

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