Transcript The Internet - Matthew T. Jones

The Internet
(The History Channel)
(Straubhaar & LaRose)
History
• The internet is a global network of
computer-based communication.
• The internet was first envisioned in the
1950s by MIT scientist J. C. R. Licklider.
• After the Soviet Union launched the
Sputnik satellite in 1957, President
Eisenhower established the Advanced
Research Projects Agency (ARPA) to
keep pace with Soviet space technology.
Development
• Queuing Theory
– Leonard Kleinrock worked with queuing
theory to study how information arrives,
remains, and leaves locations.
– Queuing theory works based on:
• Demand Access: Having access to information
only at the time it is required.
• Distributed Control: All nodes in a system share
control of information transmission.
Development
• Unlike telephones which rely on a system
of “circuit switching,” the internet relies on
a system of “packet switching” in which
information may share avenues of
transmission.
– Circuit Switching: Dedicated lines of
communication
– Packet Switching: Information is transmitted
through a network of avenues based on
demand access and distributed control.
Development
• Inspired by an article authored by Claude
Shannon (1952), Paul Baran sought to
develop a packet switching method called
“hot potato” routing.
Development
• “Hot Potato” packet switching:
– Packets (pieces of a file) are assigned
headers (address & return address) and
transmitted through a network connected by
nodes which distribute them from place to
place based on the availability of memory.
Development
• Computer scientist Bob Taylor devised a
way to use a single terminal to access
multiple computer mainframes.
• In 1969, Dr. Larry Roberts of ARPA
created the ARPAnet by combining
multiple computers into a single network
through Interface Message Processors
(IMPs) which could communicate with one
another (see diagram on following slide).
Development
• Bob Metcalfe invented the “ethernet”
capable of linking together a Local Area
Network (LAN).
• Ray Tomlinson invented E-mail in 1971 by
combining message files with mailbox
files.
Development
• Vinton Cerf and Robert Kahn developed
the protocols necessary to join networks
into larger networks.
– Internet Protocol (IP): Specifies how files are
broken into packets and how they are
addressed.
– Transmission Control Protocol (TCP):
Controls the movement of information from
one network device to another through
retransmission.
Development
• Networks are combined through
“gateways” to form the internet as a
network of networks.
Development
• In 1992, Congress passed a bill
transferring the ARPAnet to the private
sector.
• Tim Berners-Lee started the World Wide
Web by developing Hypertext Markup
Language (HTML) needed for linking files.
Development
• Mark Andreessen developed the first web
browser, “Mosaic,” which was later
marketed as “Netscape Navigator.”
How it Works
• Visiting a website:
1. You enter an address (uniform resource
locator - URL) into your browser.
2. The address of the website is translated into
the numerical IP (Internet Protocol) address
of its server by the Domain Name Service
(DNS) protocol and sent to the modem.
How it Works
• Visiting a website:
3. The request is formatted in Hypertext Markup
Language (HTML) and routed through the modem
to the Internet Service Provider (ISP).
4. The request arrives at the server which responds by
deploying the webpage as a series of data packets
which are assigned the Transmission Control
Protocol (TCP) necessary for reconfiguration at your
computer.
How it Works
5. The packets and TCP information are sent
through various routers to your IP (Internet
Protocol) address where the webpage is
reassembled as an HTML file.
Sectors
• The Internet has several industry sectors:
– Hardware: Computer manufacturing (e.g. Dell,
Gateway, Mac).
– Software: Program manufacturing (e.g.
Microsoft, Adobe, Macromedia, Nuance)
– Content Providers: Website manufacturing
(e.g. web designers)
– Internet Service Providers: Provide
connection to the internet (e.g. AOL, MSN).
Content
• Electronic Publishing
– (e.g. Online editions of newspapers.)
• Entertainment
– (e.g. TV stations and movie websites.)
• Online Games
– (e.g. The Sims, Halo, EverQuest)
• Portals
Implications
• The internet will absorb all previous media
systems.
– “Hardware,” such as television sets and radio
receivers already exist as applications (e.g.
RealPlayer, Windows Media Player,
QuickTime, WinAmp)
– Broadcast transmissions will be replaced or
duplicated by webcast transmissions once the
image quality of streaming video becomes
equivalent with HDTV.