The Internet and World Wide Web

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The Internet and World Wide Web
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History of the Internet

• In 1969, US Department of Defense wanted to
  establish a reliable communications network
• The network was to remain operational, even in
  the event of nuclear war!
• The result was ARPANET, based on TCP/IP
• Over time, other networks connected to this,
  using the same protocols
• Eventually this came to be known as the Internet

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Internet History Links

• Yahoo! List of Internet History Links

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Protocols

• The basic Internet communication protocol is
  TCP/IP
• Additional higher layer protocols include HTTP,
  FTP, SMTP, etc.

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TCP/IP Addresses

• Every Internet client and server has a unique IP
  address
• Addresses are numeric
• These correspond to Domain Names using the Domain
  Name system
• Example
• IP address 129.100.100.50
• Domain name hyperserver.engrg.uwo.ca

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Internet Applications

• Email (SMTP)
• File transfer (FTP)
• Remote login (telnet)
• Newsgroups (NNTP)
• World Wide Web
• Others
• archie
• gopher

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The World Wide Web

• In 1989, Tim Berners-Lee invented the World Wide
  Web by developing the core elements
• Hypertext Transfer Protocol (HTTP)
• Hypertext Markup Language (HTML)
• Uniform Resource Locators (URL)
• Read his original project proposal !

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HTTP

• HTTP provides standard methods for communication
  between clients and servers

Web server
Web browser (client)
HTTP
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Uniform Resource Locators

• URLs specify the location or address of a page or
  resource on the Web
• e.g. http//www.uwo.ca
• The prefix indicates the protocol used
• URLs allow many Internet services and resources
  to be accessed in a standard way, including
• FTP
• NNTP
• TELNET

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HTML

• HTML provides a standard markup language for
  describing hyperlinked documents

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Mosaic and Web Browsers

• The Web took off when Marc Andreesen and fellow
  students at the National Center for Supercomputer
  Applications (NCSA) wrote the first graphical web
  browser, Mosaic, in 1993
• Andreesen left NCSA to become a founder of
  Netscape
• Mosaic was rewritten and became Netscape
  Navigator
• Some thought Andreesen would be the next Bill
  Gates

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Internet E-mail

• Address format someone_at_machine.domain
• e.g. rbuchal_at_julian.uwo.ca
• Simple Mail Transfer Protocol (SMTP)
• universal Internet standard, text only
• Post Office Protocol (POP)
• incoming messages downloaded from server
• messages stored locally
• IMAP
• newer than POP
• messages stay on server

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Email Attachments

• SMTP messages are plain text only
• Files are attached using Multimedia Internet Mail
  Extensions (MIME) standard

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Formatted Email

• SMTP is plain text only - no formatting!
• Proprietary mail systems allow formatting, but
  are not interoperable
• Netscape and Microsoft mail readers use HTML for
  text formatting

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Mailing Lists

• People can subscribe to mailing lists - like
  newsletters
• Messages sent to all members of the list
• Basically like a common distribution list

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Threaded Discussions

• Messages are stored in a shared database,
  organized by topic
• Threads permit many parallel discussions -
  messages are organized around discussion threads,
  not chronologically
• Sometimes called conferencing or bulletin board
  systems

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Threaded Discussion Structure

• Newsgroup 1
• Message one
• reply to message one
• another reply to message one
• reply to the reply
• Message two
• Newsgroup 2
• Message one
• etc.

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Newsgroups and USENET

• USENET is a global bulletin board based on the
  Network News Transfer Protocol (NNTP)
• Messages are replicated to servers all over the
  world
• Several thousand topics

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Private Newsgroups

• NNTP servers can be used to create local or
  private newsgroups
• The ES250b newsgroup on hyperserver is an example

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Web-Based Discussions

• Many Web-based discussion systems exist.
• These use HTTP and HTML instead of NNTP to
  implement threaded discussions
• Heres a sample conference using WebBoard

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Links

• David Woolley has a guide to web conferencing
  software. He defines it as Web software for
  asynchronous group discussions using stored text
  messages.

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Basic Elements of HTML

• Document structure defined with tags
• headings, normal text, bullet list, etc
• formatting and presentation up to the browser
• Embedded image files
• Embedded links to other pages or locations

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Bells and Whistles

• Many features have been added to HTML, including
• Scripting
• Tables and frames
• Applets
• Forms
• Text formatting

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Link Types

• To location in same page

ltA HREFbottomgt Go to bottom lt/Agt
ltA NAMEbottomgt Bottom of page lt/Agt
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Link Types

• To another page in the same directory

ltA HREFpage.htmgt highlighted text lt/Agt
page.htm
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Link Types

• To a URL

ltA HREF http//www.somewhere.com/page.htmgt
highlighted text lt/Agt
Http//www.somewhere.com/page.htm
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lt!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML
3.2//EN"gt ltHTMLgt ltHEADgt ltTITLEgtYour Title
Herelt/TITLEgt ltLINK REV"made"
HREF"mailtoauthor_at_machine.uwo.ca"gt lt/HEADgt ltBODY
gt lt!-- Your HTML Page here
--gt ltPgt ltIMG SRC"/icons/back.xbm" ALT"Back
to"gt ltA HREF"http//www.uwo.ca/"gt ltIMG
SRC"/images/uwo-button.gif" ALT"UWO Home
Page"gtlt/Agt ltHRgt ltADDRESSgt Maintained by Your
Name ltauthor_at_machine.uwo.cagtltBRgt Last
update yyyy-mm-dd lt/ADDRESSgt lt/BODYgt lt/HTMLgt
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Problems

• Broken links
• Designed for static content
• Limited formatting
• Difficult to search

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Emerging Web Technologies

• Extensible Markup Language (XML)
• Dynamic HTML (DHTML)

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XML

• Extends capability of HTML
• Extensible (new tags can be defined)
• Can define content-specific tags
• e.g., ltpricegt, ltcustomergt, ltpart numbergt etc
• Much more powerful and flexible than HTML
• Easier to search

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DHTML

• Goals Richer content, faster downloads
• Includes
• HTML 4.0
• Cascading Syle Sheets (CSS) to control formatting
• Document Object Model (DOM) for programmability
• Scripting standards