1. 26-3-2015
What is the Internet?
The Internet is a global system of interconnected computer networks. These
computers are connected by phone lines, fiber optic lines, coaxial cable,
satellites, and wireless connections. The Internet enables computers to send
one another packets of digital data. Information that travels over the Internet
does so via protocols: The TCP and the IP protocol. They establish a set of
rules that specify how to send data in the form of message units between
computers over the Internet. The TCP divides the file into one or more packets,
numbers the packets, and then forwards them individually to the IP program
layer. Although each packet has the same destination IP address, it may get
routed differently through the network. TCP is responsible for ensuring that a
message is divides into the packets that IP manages and for ressembling the
packets back into the complete message at the other end.
Network types
LAN (Local Area Network) connects network devices over a relatively short
distance: computers at home, in an office building, or school. WAN (Wide Area
Network): spans a large physical distance.
History of the Internet
1969: ARPANET (Advanced Research Projects Agency Network): The first real
network to run on packet switching technology. Computers at Standford
Research Institute (Santa Barbara) and UCLA (LA) connected for the first time.
1971: Email was first developed in 1971 by Ray Tomlinson, who also made the
decision to use the “@” symbol to separate the user name from the computer
name (later it became the domain name).
1972: France began its own Arpanet-like project, called CYCLADES. While
Cyclades was eventually shut down, it did pioneer a key idea: the host
computer should be responsible for data transmission rather than the network
itself.
1979: Newsgroups are born. Usenet was an internet-based discussion system,
allowing people from around the globe to converse about the same topics by
posting public messages categorized by newsgroups.

2. 1984: The Domain Name System (DNS) was created along with the first
Domain Name Servers (DNS). The Domain name system helps to give every
Internet server a memorable and easy-to-spell address. The domain names
keep the really technical IP address invisible for most viewers. Every domain
name has a suffix that indicates which top level domain (TLD) it belongs to.
-Gov (government agencies)
- edu (educational institutions)
- org (organizations non profit)
-mil: military
-com: commercial business
- net: network organizations
Each country has got it own domain. Germany (de), France (fr), Italy (it), Japan
(jp), Mexico (mx)…
1988: Internet Relay Chat (Irc) was first deployed, paving the way for real-time
chat and the instant messaging programs we use today.
1989 brought about the proposal for the WWW, written by Tim Berners-Lee. It
was a global hypertext system, originally called “Mesh”.
1991: The first web page was created.
1993: Mosaic, the first widely downloaded internet browser, was released.
While Mosaic wasn’t the first web browser, it is considered the first browser to
make the internet easily accessible to non-techies because it was the first
graphical web browser for the general public.
1994: Netscape Navigator.
2004: The term web 2.0 is coined by Dale Dougherty, a vice-president of
O’Really Media Inc. referring to websites and rich internet applications (RIA)
that are highly interactive and user-driven.
What is the World Wide Web?
Many people use the terms “Internet” and 2World Wide Web” interchangeably,
but they are not synonymous. The Web is only part of the Internet. It is just one
of the ways that information can be disseminated over the Internet. The Web
was invented in 1993 by Tim-Berners-Lee. The web uses the HTTP protocol
(HyperText Transfer Protocol). Web pages are sets of text files coded with

3. special notation called HyperText Markup Language (HTML) that is interpreted
by a web browser. They also contain graphics, sounds, text and video. Web
pages are linked to each other via hyperlinks. Hyperlinks are certain keywords
or phrases linked to other online documents.
The concept of hypertext
The concept of hypertext predates the Web by many years. Vannevar Bush is
credited with inventing the concept of hypertext in his article 2As we may think”
(1945). He describes an imaginary machine called “Memex”. The term hypertext
did not appear until the 1960s.
HTTP and HTML
HTTP is the protocol for transferring hypertext documents. HTML is the
formatting language for a hypertext or hypermedia document. It is viewable with
a wen browser. HTML documents are plain ASCII text and can be created with
a text editor, but they contain formatting codes and links to other documents
and media (images and sounds) which can be followed using a web browser.
What is a web browser?
Program that lets the computer communicate in the web’s language with other
computers on the internet.
Is like a translation device because it takes a document written in the HTML
language and translates it into a formatted Web page.
The first browser, called NCSA Mosaic, was developed at the National Center
for Supercomputing.
Nowadays, the most popular browsers are “internet explorer” and “firefox”.
A plugin or extension is the software that interacts with a host application to
provide a more specific, function “on demand”.
Web browsers use plugins to play video and presentation formats.
What is the URL (uniform resource locator)?
It is the standard way to specify addresses on the WWW. URLs are typically
entered into the address or location bar of the web browser. URLs have the
following format:

4. 1)The protocol: specifies how information from the link is transferred, the type of
service the resource is served by (HTTP, Gopher, FTP).
2)The host or domain name: the protocol is followed by a colon, two slashes,
and then the domain name. It refers to the computer on which the resource is
located.
3)Directory names: they explain the location of the resource in the directory
structure of the server. They are links to particular files or subdirectories.
Directory names are separated by single forward slashes. Sometimes they also
include the internet port number of the service. They usually specify with “an
extension” the type of resource we are getting access to.
IP address
IP (Internet Protocol Address). This is the locator for an IP device to find
another one and interact with it. If your IP address isn’t hidden, virtually anyone
with internet access can track you directly to your home.
A static IP address: when a computer uses the same address every time a
user logs on to a network, such as the internet.
A dynamic IP address, that will be the same every time the user logs on, will
be different every time you connect to the internet.
To see you IP address click on http://www.ip-address.com/
An IP address contains 32 bits divided in 4 groups of bytes (each byte contains
8 bits). The value of each bit is represented either by 1 or by 0 in a base 2-
system. IP addresses are usually written in “dotted-decimal” notation (a notation
using decimal numbers separated by dots).
Other protocols in the internet
Gopher
FTP: File Transfer Protocol
WAIS Wide Area Information Servers
News Usenet news
Telnet Reference to interactive sessions
Mailto Electronic mail address