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Computer Networks with Internet Technology William Stallings. Chapter 04 Modern Applications 4.1 Web Access - HTTP. Hypertext Transfer Protocol HTTP. Underlying protocol of the World Wide Web Not a protocol for transferring hypertext

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Computer Networks with Internet Technology William Stallings

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Computer networks with internet technology william stallings l.jpg

Computer Networks with Internet TechnologyWilliam Stallings

Chapter 04

Modern Applications

4.1 Web Access - HTTP


Hypertext transfer protocol http l.jpg

Hypertext Transfer ProtocolHTTP

  • Underlying protocol of the World Wide Web

  • Not a protocol for transferring hypertext

    • For transmitting information with efficiency necessary for hypertext jumps

  • Can transfer plain text, hypertext, audio, images, and Internet accessible information


Http overview l.jpg

HTTP Overview

  • Transaction oriented client/server protocol

  • Usually between Web browser (client) and Web server

  • Uses TCP connections

  • Stateless

    • Each transaction treated independently

    • Each new TCP connection for each transaction

    • Terminate connection when transaction complete


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Key Terms

See Table 4.1

Page 116

  • Cache

  • Client

  • Connection

  • Entity

  • Gateway

  • Message

  • Origin server

  • Proxy

  • Resource

  • Server

  • Tunnel

  • User agent


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  • HyperText Transfer Protocol (HTTP)

    • http://www.im.ncnu.edu.tw:80/~ycchen/http://www.im.ncnu.edu.tw/~ycchen/www/test.cgi?var1=123&var2=value2

  • File Transfer Protocol (FTP)

    • ftp://ftp.ncnu.edu.tw/

    • ftp://ftp.ncnu.edu.tw/JavaDownload/Docs/ftp://anonymous:guest@ftp.ncnu.edu.tw/ftp://ycchen@www.im.ncnu.edu.tw/

  • Gopher Protocol (Gopher)

    • gopher://gopher.nsysu.edu.tw/11/traveler/train

  • Electronic Mail (Mailto)

    • mailto:username@ncnu.edu.tw

    • mailto:username@ncnu.edu.tw?subject=Hello!

  • Usenet News (News)

    • news:tw.bbs.rec.travelnews:*

  • Telnet to Remote Host (Telent)

    • telnet://bbs.ee.cycu.edu.tw/telnet://guest@bbs.ncnu.edu.tw/

  • Host-Specific File Names (File)

    • file:///C|/My Documents/

URL Examples

URL: Uniform Resource Locator


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Figure 4.1Examples of HTTP Operation


Figure 4 2 intermediate http systems l.jpg

Figure 4.2Intermediate HTTP Systems


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HTTP Messages

  • Requests

    • Client to server

  • Responses

    • Server to client

  • Request line

  • Response line

  • General header

  • Request header

  • Response header

  • Entity header

  • Entity body


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General Header Fields

  • Cache control

  • Connection

  • Data

  • Forwarded

  • Keep alive

  • MIME version

  • Pragma

  • Upgrade


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Request Methods

  • Request-Line = Method <SP> Request_URL <SP> HTTP-Version <CRLF>

  • Methods:

    • Options

    • Get

    • Head

    • Post

    • Put

    • Patch

    • Copy

    • Move

    • Delete

    • Link

    • Unlink

    • Trace

    • Wrapped

    • Extension-method


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Request Header Field

  • Accept

  • Accept charset

  • Accept encoding

  • Accept language

  • Authorization

  • From

  • Host

  • If modified since

  • Proxy authentication

  • Range

  • Referrer

  • Unless

  • User agent


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Response Messages

  • Status line followed by one or more general, response and entity headers, followed by optional entity body

  • Status-Line = HTTP-Version <SP> Status-Code <SP> Reason-Phrase <CRLF>


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Status Codes

  • Informational

  • Successful

  • Redirection

  • Client error

  • Server error


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Response Header Fields

  • Location

  • Proxy authentication

  • Public

  • Retry after

  • Server

  • WWW-Authenticate


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Allow

Content encoding

Content language

Content length

Content MD5

Content range

Content type

Content version

Derived from

Expires

Last modified

Link

Title

Transfer encoding

URL header

Extension header

Entity Header Fields


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Entity Body

  • Arbitrary sequence of octets

  • HTTP transfers any type of data including:

    • text

    • binary data

    • audio

    • images

    • video

  • Interpretation of data determined by header fields

    • Content encoding, content type, transfer encoding


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