Internet and Web Background

  1. Slides: (pptx or pdf)
    1. The Kids Guide to the Internet
  2. Internet
    1. Global system of interconnected computer networks that use the standard Internet Protocol Suite (TCP/IP) to serve billions of users worldwide
    2. Started as ARPANET; first went live in 1969
    3. TCP/IP
      1. Internet Protocol (IP): directs packets to a specific computer using an IP address
      2. Transmission Control Protocol (TCP): directs packets to a specific application on a computer using a port number
    4. IP address
      1. Uniquely identifies nodes on the Internet
      2. 4 numbers that range from 0-255, separated by periods
      3. Example: 10.2.15.25
  3. Web
    1. The system of interlinked hypertext documents accessed over the Internet using the HTTP protocol
    2. Created in 1990 by Tim Berners-Lee
    3. Web browser
      1. Software that runs on the client used to access and display web content
      2. Most popular: Chrome, IE, Firefox
      3. Most popular mobile browsers: Android, iPhone, Opera
    4. Web server
      1. A computer (or software running on a computer) on the Internet that listens for HTTP requests, typically on port 80, and responds with HTTP responses
      2. Most popular: Apache, IIS, ngnix
    5. URL
      1. Example: http://www.foo.org/abc/bar.html
      2. scheme or protocol: http
      3. hostname: www.foo.org
      4. local hostname: www
      5. domain name: foo.org
      6. top-level domain (TLD): .org
      7. path: /bar.html
    6. Domain Name System (DNS)
      1. A hierarchical look-up service that converts a given hostname into its equivalent IP address
  4. Hypertext Transfer Protocol (HTTP)
    1. Protocol that runs over TCP/IP and governs communication between web browsers and web servers
    2. HTTP request
      1. Send from browser to web server
      2. Example: 
        GET /comp/ HTTP/1.1
Host: www.harding.edu
User-Agent: Mozilla/5.0 Firefox/3.6.8
      3. Request type
      4. Relative URL
      5. Host
      6. User-Agent (History)
      7. If-None-Match and If-Modified-Since
    3. HTTP response
      1. Sent from web server to browser in response to a request
      2. Example: 
        HTTP/1.1 200 OK
Content-Length: 3027
Content-Type: text/html
Content-Location: http://www.harding.edu/comp
Last-Modified: Mon, 29 Jul 2014 14:43:55 GMT
Server: Microsoft-IIS/7.5

<!DOCTYPE html> 
<html> 
  <head>
    <title>Harding University - Computer Science</title>
Etc...
      3. Head and body
      4. Common status codes
        200 - Successful
        301 - Moved permanently
        302 - Found under different temporary URI
        304 - Not modified
        403 - Forbidden
        404 - Not found
        500 - Internal server error
      5. Content-Length
      6. Content-Type (MIME type)
        1. Type/sub-type
        2. Examples: text/plain, image/jpeg, application/pdf, video/quicktime
      7. Content-Location
      8. Last-Modified
      9. Server
      10. ETag
    4. Viewing in a web browser