What is the Internet?

toughhawaiiNetworking and Communications

Oct 26, 2013 (3 years and 7 months ago)

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Lecture

Network Communication: The INTERNET


What is a network?


A network is what you get when you connect two or more computers together. A network allows you
to transfer files from one computer to another, send messages to another omputer, and run
programs on the other computer. One of the benefits of networks is tha
t they allow users to share
peripherals.

If the computers connected via the network are in the same building or in buildings not
far away, you have a local area network (LAN). If the computers are separated by significant
distances (hundreds of miles), yo
u have a wide area network (WAN). The Metropolitan Area
Network (MAN) is somewhere in between: it covers an area greater than a single building or
campus but smaller than the whole country.

Of course, all these networks
-

local, metropolitan and wide area

-

can be connected together, and
in fact they normally are. So your computer on your desk in your office (or in the lab or wherever
you use a computer) will be connected to your institution's local network (or one of them, if there are
several local area
networks set up), and that local network will be connected to the MAN for your
area. The MAN will be connected to the Internet, and therefore to a wide area network. Therefore,
by networking computers, you can transfer files from one computer to another wi
thout using
external storage media such as flash drives.


What is the Internet?

Definition & Protocols

Notes & preliminary definitions from
Internet Investigations in Criminal Justice
, by Cynthia B.
Leshlin, published by Prentice Hall (1997). (Available o
n reserve at John Jay)


1. World's largest information network.


2. Global web of computer networks.


3. Inter
-
network of many networks all running the TCP/IP protocol


4. Powerful communication tool


5. Giant 'highway' system connecting computers and the
regional and local networks that
connect these computers.


6. Virtual database


7.

Information superhighway,

data highway, electronic highway, net, cyberspace.

To access the internet, you need three elements
:

The first is the hardware to connect your computer to the internet: via the phone line or via a cable
connection or via a wireless connection. The phone line possibilites are
a modem
, a
network card
,
a
Direct Subscriber Line line (DSL)
. In order to connect

to the internet through the cable network,
you need a cable service and modem from your local cable provider.

Second, you need the software to display the files from the internet,
an internet browser

(Netscape or Internet Explorer).



Finally, access to
a computer that is connected to the internet. In school, almost all computer
workstations are connected to the internet via the John Jay network, the CUNY node on the internet
and a T
-
1 line. From home, if you have a dial
-
up modem, you usually need to pay
a commercial
Internet Service Provider (ISP) to connect you to the internet. AOL, MSN, Mindspring, AT&T,
Worldnet, Erols and many others are ISPs. DSL service is available from your local telephone
service providers.


Question: Can you use a network to sha
re an Internet connection?

Answer: If you install a device called a
router

to your network, you can share broadband Internet
connections, but not with dial
-
up.




Examples of networks


Global economy networks ...

http://sharp
-
world.com/worldwide/index.html


http://www.symantec.com/globalsites.html


Community network ...

http://www.bev.net/


History


The internet began in 1969 when a series of computer networks were developed. The first network
(ARPANET) was sponsored by the United States Department of Defense in response to a need for
military institutions and universities to share their research. In
the 1970s, government and university
networks continued to develop as many organizations and companies began to build private
computer networks. In the late 1980s, the National Science Foundation (NSF) created five
supercomputer centers at major universiti
es. This special network is the foundation of the internet
today.

Any commercial service or institution which provides full access to the internet includes the
following:

* Electronic Mail (e
-
mail)

E
-
mail allows you to send, receive and forward messages
from people all over the world, without
additional charge. E
-
mail addresses are made up of USERIDs and DOMAIN names.

fceballos (my
userid) + jjay.cuny.edu (CUNY Domain Name) is my e
-
mail address.

* Telnet

Telnet provides the capability to log in to a remo
te computer and work interactively with it.

* File Transfer Protocol (FTP)

FTP is a method which allows you to move files and data from one computer to another, for
instance to download from the internet to your PC.

* World Wide Web

A collection of docum
ents linked together a what is called a hypermedia system. Links point to any
location on the internet that can contain information in the form of text, graphics, video or sound
files. Using the Internet requires a "browser" capable of viewing documents an
d navigating the
structure of the Web. The Web was developed at the European Particle Physics Laboratory (CERN)
in Geneva, Switzerland.

The Web and the Internet are not synonymous. The internet is the network of computers, linked by
telephone or cyberopti
c lines. The Web is a collection of protocols that allow you to construct, send
and display files with color, sound, and image, on the internet.

URL Uniform Resource Locator

protocol/server
-
name/path/file

http://home.netscape.com/home/welcome.html


URLs may be used to access ftp files,

news files, web (HTTP) files, and others.

HTTP Hypertext Transfer Protocol
-

the addressing system for the web.

HTML Hypertext Markup Language
-

the document forma
t for the web.

More Terminology


Modem Hardware device


BPS


ISDN line



T
-
1 line



DSL


T
-
3


Cable modem


Bandwidth

TCP/IP

(Transmission Control Protocol/Internet Protocol)



SLIP

(Serial Line Internet Protocol)



PPP

(Point
-
to
-
Point Protocol)

ETHERNET

CARD



ISP

(Internet Service Provider)




JAVA



Applet