Transcript Internet & WWW

The Internet
The Internet
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Definition: Network of networks.
Began in 1969, DOD project called ARPANET.
Early 1980’s NSF creates NSFnet
NSF takes over both by mid ’80’s
The Internet is created.
IP Addresses
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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:
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Internet Protocol Addresses
IP Addresses
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Format:
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Do the math:
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x.x.x.x
Where each x is a number from 0 to 255.
256*256*256*256 = 4,294,967,296
Despite this, we are running out of IP addresses
IPv6 may take care of this
TCP/IP
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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 let’s break up the large files into smaller ones, and send the
smaller pieces.
That’s TCP/IP
TCP/IP
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Transmission Control Protocol/Internet Protocol
Protocol for how to:
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break up information into standard sized “packets”
address each one,
send them out to their destination,
reassemble them upon receipt.
Domain Name System
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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.
Domain Name System
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Early on, realized the need to associate unique names with
each IP address.
Domain Name System established:
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A single organization responsible for assigning domain names.
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IANA
A decentralized system of distributing the names
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domain name servers
Domain Names
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Names separated by dots
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Last part is called top-level domain (TLD) or zone.
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Usually 3 or 2 letters long.
Next part is second-level domain.
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E.g., www.uwm.edu
The unique name of the organization to whom the name belongs.
From there, individual organization can name the individual
computer whatever they want.
In summary
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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.
The WWW
World Wide Web
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The World Wide Web
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Tim Berners-Lee working at CERN decided he wanted a way to share
information easily with his colleagues.
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worlDwidEweb ca 1991
Four inventions
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HTTP: HyperTextTtransfer Protocol
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URL: Uniform Resource Locator
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HTML: HyperText Markup Language
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Web Servers
HTTP
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Hypertext Transfer Protocol
URLs
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Format: [scheme]://[host name] / [path name]
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Scheme — the type of transfer/connection you have
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Host name — the name of the computer to which you are connecting.
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Usually http
www.uwm.edu.
Path name — the full path name to the file you are looking for.
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Series of directories ending in a file name.
If a file is not specified, by default browser looks for an index.html file.
HTML
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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.
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<h1>This is a heading </h1>
And this is <b>some</b> formatted <i> text</i>
<ul>This is a list
<li>Item 1
<li>Item2
</ul>
Web Servers
The Internet
Graphical Web Browser
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1991 – 1994 tremendous growth
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1993: NCSA Mosaic
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Written by Marc Andreesen.
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Incorporated images into text.
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Ran under Unix.
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By end of year, PC and Mac versions were out.
Internet & Web Growth
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As of January 2003
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171,638,297 hosts
Taken from: http://www.isc.org/