How Does the Internet Work?

Download Report

Transcript How Does the Internet Work? 

The Internet
What is the Internet?
 The Internet involves
millions of computers,
connected in complex
ways to a maze of local
and regional networks
Origins of the Internet
 1969
 Department of Defense established experimental
network connecting 4 research computers (UCLA,
Stanford Research Institute (SRI) , UC@Santa
Barbara and U. of Utah.
 Called ARPANET
 1980s National Science Foundation involved

Only scientific, research and academic institutions (no
commercial traffic)
Other Developments…
 1989 - E-mail connectivity thru CompuServe
and MCI Mail
 1991 – move towards private sector


National Access Points (NAPs)
Internet Service Providers (ISPs)
 Communication coordinated through national
and international organizations (standards)
Who Owns the Internet?
 No one company or country can be considered as
owner of Internet

Ownership shared among various entities
 Coordination:
 Internet Society (ISOC)
 Internet Engineering Task Force (IETF)
 Internet Architecture Board (IAB)
 In the US –
 ICANN – Internet names and port numbers
(Internet Corporation for Assigned Names and
Numbers)
Cost ($$$$)…
 Revenue is required to offset expenses
 Servers, routers, communication lines, etc.
 Costs must be covered by users
 Companies, organizations and individuals
 AOL – subscribers charges monthly fee
Difference Between Internet and Web?
 World Wide Web is the Multimedia portion of
the Internet


Images, video, sound, animation, etc.
Early 1990s
Internet Address

Domain Name
 Logical name for computing system
www.scranton.edu
 Top-Level Domain (suffix)
 ICANN
 IP Number
 32-bit address (4 part decimal #)
 ARIN (American Registry for Internet Numbers)/ RIPE / APNIC
 132.161.33.60
Internet Address…
 Ethernet Address


48-bit address built into machine or Ethernet
board
Refers to specific board in a local computer
Addressing
 Domain Name Server (local)
 Network Information Server (wider area)

Maintain databases with domain names and
IP numbers in binary format
Domain Name

IP Number (logical)

Ethernet Address (physical)
Laptops
 Static IP address

Specified manually and entered into network
tables
 Dynamic IP address


Dynamic Host Configuration Protocol (DHCP)
Ask network for an IP address when you turn it
on (from a pool of available addresses)

IP address changes each time computer is used
Web Browsers
 Internet Explorer, Mozilla, Netscape
Navigator, Firefox
 System of communicating Web documents

Hypertext Transfer Protocol (HTTP)
 Formatting instructions called:

HTML (Hypertext Markup Language)
HTML Tags
 <html> </html>
Begin/End of document
 <b> </b>
Bold
 <p> </p>
Paragraph
 <title> </title>
Title – top of window
 <table> </table>
Use in tabular form
 <ol> </ol>
Ordered List
 <br>
Break (new line)
 <img src=“mypicture.gif”>
Image
JavaScript – for Interactivity
 Allows for local processing (on your machine)
instead of on server (server-side processing)
 Browser handles some processing chores
 Client-Side Processing

Buttons, Check boxes, drop-down lists
 Advantage

Faster response to user interaction
 Disadvantage

Opens user to possible risks