1's and 0's Flying Through the Air

Understanding the Internet

Osher Lifelong Learning Institute
University of Illinois, Urbana-Champaign

Scott Badman, Instructor

Session 2: Connections to the Internet

October 15, 2014



Review of Internet addresses and HyperText Markup Language (HTML)

Webpage Development and Uploads to a Web Server.
HTML is a text based protocol for creating multimedia web pages.
It uses "tags" enclosed in "angle brackets" (just the less than, <, and the greater than, >, symbols).
It can be created on any text editor.
The HTML text file is then uploaded to a web server.

The web server computer runs a special web server program
The server receives HyperText Transfer Protocol (HTTP) requests and replies by sending back your HTML web page.

Universal Resource Locator (URL)
The familiar human readable addresses, such as: www.nytimes.com

The final characters after the last dot, such as .com, are called the "domain".
They help the routing computers to find the proper numeric address, and also provide a human understandable category of the web page.
The www at the beginning is often optional and assumed if missing. It stands for "world wide web".

Officially, all URL's are preceded by a type, such as: http://www.nytimes.com or ftp://scottbadman.com
If it is missing, http:// is assumed, meaning "HyperText Transfer Protocol", or more simply "the web page".
The other types are much rarer, and used mainly by web pages to do special data transfers.
The first thing your web browser does when you enter a URL is contact a special "Domain Name Server" (DNS) computer that replys with the numeric IP address.

IP Addresses
These are the numeric addresses that the Internet routing computers actually use to find a web server computer.

Usually there is one IP Address per computer.

The IP Address is simply a 32-bit binary number, written in a funny was as four decimal numbers from 0 to 255, separated by periods.

You can find your computer's IP Address by:
Windows: pressing the Start button, entering "Command" in the Search box, and typing "ipconfig" in the black window that appears.
Mac: pressing the "Apple" symbol in the upper left corner, selecting System Preferences, and Network.
You can find the IP Address of most web pages on the Internet, plus all the intermediate routing computers, the following way:
Windows: pressing the Start button, entering "Command" in the Search box, and typing "tracert URL" in the black window that appears.
  Example: tracert www.nytimes.com

Mac: from Finder, select Go, Utilities, Terminal, and then typing "traceroute URL" in the white window that appears.
  Example: traceroute www.nytimes.com

IP Version 6 Addresses (IPv6)
These are the new IP Addresses that are slowly being adopted because we have run out of traditional (Version 4) addresses.

The IP Version 6 Address is a 128-bit binary number, written with a complicated system using hexadecimal numbers (0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f).

There are more IP Version 6 Addresses than there are atoms in the Universe. We won't run out of them ever.

MAC Addresses
Most pieces of computer related hardware have a unique Media Access Control (MAC) address.

These addresses are assigned by a world-wide authority to computer equipment manufacturers.

They are permanently burned into the equipment's firmware program chips, and never change.

The MAC Address is a 48-bit binary number, written with a simple system using hexadecimal numbers (0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f).

They are used by the hardware when communicating with another directly connected piece of computer hardware.

You will probably never have to use or think about the MAC address.

Connections to the Internet Service Provider (ISP)

as a Power Point presentation (very large file)
as a .pdf file (loads faster)

End to End Connection From Your Computer to the Web Server and Its Database Server

as a Power Point presentation (very large file)
as a .pdf file (loads faster)

(10 to 15 Minute Break)

Practical Tips and Techniques

How Can I Connect to the Internet?

Class discussion and questions.