The Internet

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The Internet
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The Internet

• Definition Network of networks.
• Began in 1969, DOD project called ARPANET.
• Early 1980s NSF creates NSFnet
• NSF takes over both by mid 80s
• The Internet is created.

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IP Addresses

• Needed a way to identify individual computers on
  the internet.
• Hit upon the idea of IP addresses.
• Give each computer a unique number (address) and
  then you can send information to it.
• Stands for
• Internet Protocol Addresses

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IP Addresses

• Format
• x.x.x.x
• Where each x is a number from 0 to 255.
• Do the math
• 256256256256 4,294,967,296
• Despite this, we are running out of IP addresses
• IPv6 may take care of this

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TCP/IP

• Early on, realized they needed a better way to
  transfer files.
• Large files moved slowly, clogged up the network,
  and if damaged in transit, were a pain to
  re-send.
• So lets break up the large files into smaller
  ones, and send the smaller pieces.
• Thats TCP/IP

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TCP/IP

• Transmission Control Protocol/Internet Protocol
• Protocol for how to
• break up information into standard sized
  packets
• address each one,
• send them out to their destination,
• reassemble them upon receipt.

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Domain Name System

• Remember each computer has a unique IP address.
• To connect to that computer, use its IP address.
• To connect to the alphas 129.89.8.201
• To connect to miller 129.89.???.???
• Way too tedious.

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Domain Name System

• Early on, realized the need to associate unique
  names with each IP address.
• Domain Name System established
• A single organization responsible for assigning
  domain names.
• IANA
• A decentralized system of distributing the names
• domain name servers

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Domain Names

• Names separated by dots
• E.g., www.uwm.edu
• Last part is called top-level domain (TLD) or
  zone.
• Usually 3 or 2 letters long.
• Next part is second-level domain.
• The unique name of the organization to whom the
  name belongs.
• From there, individual organization can name the
  individual computer whatever they want.

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In summary

• IP addresses give each computer a unique address.
  
• TCP/IP is the protocol that made sending files
  over the internet possible.
• Domain names make it easier to remember computer
  names.
• Domain name servers handle the translation from
  names into IP addresses.

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The WWW
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World Wide Web

• The World Wide Web
• Tim Berners-Lee working at CERN decided he wanted
  a way to share information easily with his
  colleagues.
• worlDwidEweb ca 1991

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Four inventions

• HTTP HyperTextTtransfer Protocol
• URL Uniform Resource Locator
• HTML HyperText Markup Language
• Web Servers

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HTTP

• Hypertext Transfer Protocol

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URLs

• Format scheme//host name / path name
• Scheme the type of transfer/connection you have
• Usually http
• Host name the name of the computer to which you
  are connecting.
• www.uwm.edu.
• Path name the full path name to the file you
  are looking for.
• Series of directories ending in a file name.
• If a file is not specified, by default browser
  looks for an index.html file.

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HTML

• HyperText Markup Language
• Plain text document with hidden codes that tell
  a browser how to format the information.
• Based on structured documents in which the
  content of the document is separated from the
  formatting of the document.
• lth1gtThis is a heading lt/h1gtAnd this is
  ltbgtsomelt/bgt formatted ltigt textlt/igtltulgtThis is a
  list ltligtItem 1 ltligtItem2lt/ulgt

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Web Servers
The Internet
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Graphical Web Browser

• 1991 1994 tremendous growth
• 1993 NCSA Mosaic
• Written by Marc Andreesen.
• Incorporated images into text.
• Ran under Unix.
• By end of year, PC and Mac versions were out.

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Internet Web Growth

• As of January 2003
• 171,638,297 hosts
• Taken from http//www.isc.org/

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