I n t e r n e t  

A little History

• 1969: ARPNET (US Department of Defence). TCP/IP protocol.
• 1986 NSFNET (National Science Foundation), replaces ARPNET in 1990.
• 1989: Tim Berners-Lee at CERN (high energy physics center in Geneva): idea about the internet, unify the different available services (telnet, FTP, gopher, ...).
• 1990: First (text) browser, concept of hypertext. The HTTP protocol (HyperText Transfer Protocol). WWW.
• 1993: "Mosaic", the first graphical browser, written by Marc Andreesen was released by the NCSA.

How does it work

It is a worldwide WAN.

TCP/IP

The Transmission Control Protocol divides each message into small pieces (packets), numbers them, and hands them to the

Internet Protocol. This protocol takes care of sending these packets. Each one is sent separately and contains IP address and the number of the piece.

The IP address has the form of four numbers, separated by dots, like 151.170.102.15. The first one/two/three of these numbers are the network number, the last three/two/one the host number, depending on whether the number belongs to a class A/B/C subnet.

Domain Name Service. Since IP addresses are difficult to remember, each server has also a domain name like "www.fc.edu" or "mycompany.com", something separated by dots (but the parts between the dots don't correspond to the parts between the dots in the IP addresses). "de" or "com" is the top-level domain, the other one, two or three parts are sub-level domains. Common top-level domains are:

• edu: educational US institutions,
• com: commercial US servers,
• gov: US government servers,
• net: US network providers,
• org: other US servers,
• ch: swiss servers,
• it: italian servers, ... and so on.

Routing and Gateways

How does data find the corresponding address? Gateways are computers for exchanging data between different subnets. They use so-called routing tables. The way data takes between two fixed points differs over time, depending on which ways are currently unavailable or congested. Even part of the same page may go over a different continent than another.

• email: need either mail client (like outlook) or
  web interface.
• telnet: Use your computer as the terminal for another. You have to login and have a password.
• FTP (file transfer protocol) for downloading large files, usually with anonymous FTP where the login is "anonymous" and password is your email address.
• gopher ("go for")
• chat (IRC)
• newsgroups
• WWW (one big document with billion of HTML-pages)

URL

Uniform Resource Locator, like "http://www24.brinkster.com/prisnerich/CPT105/CPT105.html" shows you the protocol used (http), the domain name (www24.brinkster.com), and the path (prisnerich/CPT105/CPT105/CPT105.html)---folder and subfolders---where the page you are looking for (CPT105.html) is located on the server.

In other cases, when you don't just look for an existing page but let yourself create a special page using scripts, you have protocol, domain name, and some query.

MIME type

MIME means Multipurpose Internet Mail Extension is a way of describing the document's type. Here are examples:

MIME-type	document extension	document type
text/html	html	HTML page
image/gif	gif	GIF Format
image/jpeg	jpeg or jpg	JPG Picture
application/postscript	ps	Postscript file
application/postscript	ps	Postscript file

Dynamical Web Pages

Browser (on client computer)

Searching the Internet

The Internet in Business