How the Web Works

1
How the Web Works

• AGED 3142

2
How the Web Works

• Most people use an internet service provider
  (ISP) or an online service provider (OSP) like
  AOL to access the internet through a modem
• (average modem connection56,000 bps cable
  modem 500,000 bps)
• The U of A computer labs have their own direct
  connection to the internet through an internet
  server
• (T1 connection1,544,000 bps T344,736,000 bps)

3
How the Web Works

• Modems convert digital information to analog
  information that can travel over the physical
  lines that make up the internet
• These lines include phone lines (twisted pair and
  optical fiber), coaxial cable, satellite
  airwaves, then they convert incoming analog
  signals back to digital
• Digital conversion takes time and slows download
  speeds

4
How the Web Works

• Information downloaded to your lab computer from
  a Web server in India, for example, probably
  follows this route
• Server in India Regional network in Asia
  backbone network regional network in U.S. U
  of A server PC in computer lab
• All the files related to a Web site are stored on
  a server (usually owned by an ISP/OSP or by a
  large company or organization)
• Every server has its own address called a URL
  (uniform resource locator)

5
How the Web Works

• URLs contain the following elements
• access method (usually hypertext transfer
  protocol -- http//)
• location or domain name (www.uark.edu)
• directories and HTML file (/depts/aeedhp/courses/a
  ged3143/index.htm)
• So, the address for the AGED3142 course home page
  is
• http//www.uark.edu/depts/aeedhp/courses/aged3143/
  index.htm

6
How the Web Works

• Organizations like InterNIC, working with the
  World Trade Organization, register domain names
  for 35 and up
• Each web site is a collection of pages linked by
  hypertext that can be read with a web browser,
  like Netscape Navigator or Microsoft Internet
  Explorer
• When you open a web site, your computer
  downloads each individual file associated with
  each page to its RAM and displays the visual
  images on your monitor

7
How the Web Works

• Download time is dependent on a few factors
• Connection speed (modem)
• Computer speed (speed of processor and amount of
  RAM)
• Network bandwidth
• Size of files
• Server speed

8
How the Web Works

• The files are cached, or saved temporarily, in
  your computers memory so when they need to be
  loaded again they load very quickly
• If the browsers cache files are not cleared
  occasionally, you may not be looking at the most
  recent version of a page
• Cached files are a record of where youve been
  recently on the Web

9
How the Web Works

• This has been a brief overview. The intricacies
  of how the Web works could fill an entire
  semester. We havent even touched on e-commerce,
  networked databases, web security, or many other
  aspects of the Internet and the Web.