Transcript Figure 11.01 - personal.kent.edu

Web and Internet
Part I
ST: Introduction to Web Interface Design
Prof. Angela Guercio
Spring 2007
What to expect…
Title of the course:
Web Interface Design

Today we focus our attention to the
word WEB

in the next classes we will focus our
attention to the word INTERFACE and
then to the word DESIGN
Objectives
In this lecture, you will learn about:

The definition of world wide web

The difference between Web and Internet.

The way computers communicate

The protocol of communication of the Internet

How computers communicate on a channel.

Some basic definitions of Web related items

The protocol of transmission of the Web\
Web Interface Design
What is the Web?
 World Wide Web (or shortly WEB)
is the premier Internet software
application.
 It is a application that allows linked
documents, called hypertext to run
over the Internet
 The Web uses (is NOT) the
Internet!
What is the Internet?

The Internet (sometimes simply
called the Net) is a world-wide
interconnected system of
networks that connects
computers around the world.

The word Internet stands for
Interconnected Network of
networks
Internet
From the http://www.infosatellite.com/images/articlepics/internet2_usa_map.jpg
Network


A network is a group of two or more
computers that are linked together.
Two well known types of networks
are:

Local Area Networks (LANs)

A network that connects computers in a
small geographic area



Computers in the same building or in a group
of buildings
Computers in the same university small
campus (Stark)
Wide Area Networks (WANs)

A network of LANs
How does the Internet work?

Computer exchange packets

A packet contains a set of data
that are addressed to a specific
computer
message
packet
message
packet
Traffic

The traffic represent the network
usage at a given moment.


Congestion can cause delay in data
transmission


The data transmitted of the net.
Internet Traffic Report
IN CLASS PRACTICE - Go to
http://www.internettrafficreport.com/main.htm
What is the current index in Europe?
Which continent has the best traffic
performance at the moment?
Which router in the continent with the worse
performance is the cause of the problem?
Router

A router is a dedicated machine that selects
the best route that the packet should take to
go from the source to the destination

Decision is taken according to traffic and other
parameters
Pinging


Ping is a network tool used to verify
if another computer is active or not.
How it works?




The program sends to the other
computer an “echo request” (Ping?)
message which is made of 4 packets
The data are sent over the Net and if
received the target replies with “echo
response” (Pong!)
The tool measures the time for the
round trip as well as the number of
packets that got lost
No reply indicates that the target is not
active.
Pinging
IN CLASS PRACTICE: How to ping?
1.
Open the Command Prompt
2.
type ping followed by the name or
the IP address of the computer that
you want to ping
Internet Services

The Internet is a client-service
architecture

A server is a shared machines that
provides a service to other machines


Ex. A Web Server is a machine dedicated to
sending, storing and receiving Web Page
documents
A client is a machine that asks for
services or resources from a server
TCP/IP

The protocol of communication
of the Internet is the TCP/IP

TCP = Transmission Control
Protocol


It ensures the reliable delivery of the
packets
IP = Internet Protocol

It takes care of how the packets are
routed
IP address

The IP Address is similar to a phone
number or a postal address

Each server and client have a unique
address
(the logical name)
loki.cs.kent.edu
or the corresponding numerical
(IP address)
131.123.35.15
IP address (cont.)
loki.cs.kent.edu
Machine name

Top-Level Domain



Domain name
com
.it
edu
.au
gov
.jp
mil
.fr
net
.de
org
.uk
Exercise: What is your IP
address?
Open your Command Prompt
 Type ipconfig

Matching host names and IP
addresses

If you have the logical name
and you want to find the IP
address, open the Command
Prompt and type:

nslookup logical_name
How to get on the Internet?

Technologies:

Dial-up

Requires the use of a modem and a telephone line


ADSL (Asymmetric Digital Subscriber Line)

It is DSL technology that transmits over the
telephone network in a faster way than the
conventional modem.



Slow (56 Kbps)
Range from 256 kbit/s (kilobits per second) to
24,000kbit/s, depending on DSL technology, line
conditions and service level implemented.
Data are transmitted at a frequency that are higher
that the human voice so they not interfere with the
telephone voice communication.
Digital Cable

Requires the use of a cable modem (512 Kbps up
to 11Mbps) that transfers the data over the cable
television infrastructure
What is the Web?


Returning back to the word Web….
World Wide Web (or shortly WEB) is
the premier Internet software
application.

It is a application that allows linked
documents, called hypertext, to run over
the Internet
Question:
How do I access a document?
URL

A URL (Uniform Resource Locator) is
the global address of documents and
other resources that are on the Web.

It is formed by a IP address or the
domain name and the protocol (ex. http)
that should be used to access the page
Ex:


http://www.cnn.com
ftp://cs.kent.edu/~aguercio/index.html
Web Protocols

HTTP (Hyper Text Transfer Protocol)
describes how messages are
formatted and transmitted from the
Web server to the Web browser.

FTP (File Transfer Protocol) is used
to transfer files from one machine to
another over the Internet.

It works in similar way as HTTP which
transfer pages but it is used to transfer
files
Other Web terms….

Web Bowser: The software
application that displays Web pages





Netscape
Internet Explorer
SeaMonkey
Mozilla Firefox
Web server: the computer that serves
the requests sent from the Web
Browsers
Other Web terms….(cont.)

Web Page: is a document on the
Web.
It is accessed with a unique URL
address
 It may contain any type of media
such as text, images, sounds,
video.
 The document is called hypertext
because it contains hyperlinks to
other documents.

Other Web terms….(cont.)

Hyperlink: is an element of an
electronic document which
indicates an address in the
same document or outside the
document.

To follow the link, click on it and
you will be moved from the current
document to the referred one.
Conclusion
We have learned….

The definition of Internet and of World
Wide Web

How computers communicate over the
Internet

How to get connected to the Internet

Basic terminology related to the Internet
and to the Web.