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How the Web Works
AGED 3142
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 connection=56,000 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 connection=1,544,000 bps; T3=44,736,000 bps)
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
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)
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/aged3143/index.htm)
• So, the address for the AGED3142 course home page ishttp://www.uark.edu/depts/aeedhp/courses/aged3143/index.htm
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
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
How the Web Works
• The files are “cached”, or saved temporarily, in your computer’s memory so when they need to be loaded again they load very quickly
• If the browser’s 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 you’ve been recently on the Web
How the Web Works
• This has been a brief overview. The intricacies of how the Web works could fill an entire semester. We haven’t even touched on e-commerce, networked databases, web security, or many other aspects of the Internet and the Web.