Transcript Mastering the Internet, XHTML, and JavaScript

Mastering the Internet,
XHTML, and JavaScript
Chapter 1
Overview of the Internet
Outline










Goals and Objectives
Chapter headlines
Introduction
Internet and WWW
Client/Server Model
Diagnostic commands
Evolution of Internet
Transmission
IP Addresses and URLs
Internet Domain Names








E-mail addresses
File Protocols
File Compression and
Decompression
Intranets and Extranets
Connecting to the Internet
Types of Modems
Internet Tools
Summary
Chapter 1 - Overview of the Internet
2
Goals and Objectives

Goals
Understand and master some of the basic concepts of Internet
and World Wide Web, to be able to use them effectively in
ordinary life, as well as in professional activities

Objectives








Client/Server Model
Data and file transmission
URLs and IP addresses
E-mail addresses
File protocols, compression and decompression
Intranets and Extranets
Internet connections
Modems
Chapter 1 - Overview of the Internet
3
Chapter Headlines





1.1 Introduction
 The Internet is dubbed as a new mode of transportation
1.2 The Internet and the World Wide Web
 The web is the section of internet that features multimedia
capabilities
1.3 Internet Jargon
 Learn the internet jargon as you go
1.4 Client Server Model
 This model allows two networked computers to talk to each
other
1.5 Client/Server Diagnostic Commands
 These are useful to probe communication with a server
Chapter 1 - Overview of the Internet
4
Chapter Headlines





1.6 Evolution of the internet and the World Wide Web
 The internet has been evolving since the 1960s
1.7 Transmission across the Internet
 The TCP/IP protocol and its packets are central to internet
use
1.8 IP Addresses and URLs
 Computers use IP addresses and humans use URLs
1.9 Internet domain Names
 An internet domain is a part of a URL
1.10 E-mail Addresses
 An E-mail address extends the naming scheme of a domain
name
Chapter 1 - Overview of the Internet
5
Chapter Headlines






1.11 File protocols on the Internet
 Formats and rules of exchanging files on the Internet
1.12 File Compression and Decompression
 Keeping file size small to speed up downloads and uploads
1.13 Intranets and Extranets
 Companies use these private networks for security reasons
1.14 Connecting to the Internet
 Companies use T lines while homes use dial-up connection
1.15 Types of Modems
 Analog (phone), cable, and DSL modems
1.16 Internet Tools
 These tools depend on you interest
Chapter 1 - Overview of the Internet
6
Introduction



The internet provides an instant mode of
information and communication
Internet had more users in its first five years than
telephone did in its first thirty years
E-mails already outnumbers regular mails
Chapter 1 - Overview of the Internet
7
Internet and World Wide Web





Internet is a network of networks
It is known as information
superhighway
Internet links powerful servers in
every part of the world
World Wide Web (WWW) is the
driving force of internet that features
multimedia capabilities, such as, text,
audio, video, graphics, and images
The heart of internet is its dynamic
nature and randomness of
information
Chapter 1 - Overview of the Internet
8
Client/Server Model



Client/Sever model uses two
computer programs installed
on separate, but networked,
computers located at
different locations
The client requests services
from the server
Multiple clients can access a
server concurrently
Chapter 1 - Overview of the Internet
9
Two-tier/Three-tier Architecture



Client/Server databases
are used extensively on
web.
Two-tier architecture is
the most common
model.
In three-tier model, a
middle server is added
between the database
and the client for
security purposes.
Chapter 1 - Overview of the Internet
10
Client/Server Diagnostic Commands
The three important commands are:
1.
finger: Allows you to find who is currently logged into
a given host or whether a particular user is logged in
e.g. – finger hostname
finger username@hostname
2.
ping: Allows a client to check whether a server is up
and running
e.g. – ping hostname
3.
tracert: Traces the transmission route of data from
client to a server
e.g. – tracert hostname
Chapter 1 - Overview of the Internet
11
Evolution of the Internet




Early research on the concept of internet began in
1962 at Advanced Research Project Agency (ARPA)
The sequence of Internet development is:
 1960s  ARPANET
 1970s-1980s  CSNET, USENET,
BITNET, NSFNET
 1990s  World Wide Web
In 1989, WWW was conceived by Berner-Lee
The Web exploded when Mosaic (first graphicallyoriented browser) became available from the NCSA
Center at the University of Illinois, UrbanaChampaign in 1992
Chapter 1 - Overview of the Internet
12
Transmission across the Internet



Data, such as Web pages and e-mail messages, are
transmitted from one computer to another across the
Internet via the TCP/IP protocol
The TCP/IP protocol is embedded in TCP/IP software
that is part of the OS (operating system) of any computer
Each computer on the Internet has a unique IP address
that is used to identify it. The TCP/IP software uses this
IP address in data transmission
Chapter 1 - Overview of the Internet
13
Transmission across the Internet


The TCP/IP software breaks the data to be delivered
into TCP packets (similar to letters), bundles them,
labels them with the sender and receiver IP addresses
(similar to envelopes), and sends them to the
receiver’s IP address
The TCP/IP software of the receiving computer
unpacks the TCP packets (similar to opening an
envelope), connects them to construct the original
data (such as an e-mail message), and makes it
available for an application program to read (such as
an e-mail tool)
Chapter 1 - Overview of the Internet
14
The Internet
Chapter 1 - Overview of the Internet
15
IP Addresses and URLs







An IP address is a 32 bit integer represented by four 8-bit
numbers, separated by periods
A typical IP address is 155.33.227.141
An IP address is assigned to one and only one host
A URL (uniform resource locator) is the name version of IP
address
A typical URL is http://www.neu.edu whose IP address is the
one given above
We use URLs because IP addresses are difficult to remember
DNS (Domain Name System) software converts URLs to IP
addresses and vice-versa.
Chapter 1 - Overview of the Internet
16
Internet Domain Names






URLs are also known as domain names
Domain name consists of sub-domains (usually less
than 5)
The first sub-domain is host name
The last sub-domain is top-level domain (TLD)
Second level domain excludes the host name
Example:
Domain name
www.coe.neu.edu
Host name
TLD
Second level domain name
Chapter 1 - Overview of the Internet
17
Internet Domain Names

TLD can also be geographic i.e. country codes, such
as ‘au’ for Australia, ‘uk’ for England, etc.
The most common top-level domain names are
 .com: commercial organization
 .edu: educational institution
 .gov: government agency
 .org: nonprofit organization
 .net: network service provider
 .mil: U.S. military
Chapter 1 - Overview of the Internet
18
E-mail Addresses




Each user on the internet has a unique e-mail address
The format of e-mail address is:
username@second-levelDomainName
The username in the format above is selected by the
user and it can be a combination of letters, numbers
and certain special characters
Some example e-mail addresses are:
[email protected]
[email protected]
[email protected]
[email protected]
Chapter 1 - Overview of the Internet
19
File Protocols


File protocols determine the formats and rules of
exchanging files between the server and client
The file protocols used on the web are







http: Allows client to request a webpage from server
https: Secure http for secure communication
smtp/pop/imap: Sends an e-mail message to a specified
address
nntp: Allows client to read and post messages on
newsgroups
ftp: Allows downloads and uploads for files
telnet: Allows access to a remote computer
file: Displays a file existing on client local drive
Chapter 1 - Overview of the Internet
20
File Compression and Decompression






File transfer through internet depends on internet
connection speed, file size and server traffic.
File size affects both transfer time and disk space
File compression and decompression allow us to
control the file size
File compression softwares, e.g. winzip, use complex
algorithms to decode (decompress) and encode
(compress) a file.
For example, the file “AAAAAAAGGGWZZZZ”
can be compressed as “7A3G1W4Z”
Multiple files can be compressed together to create
archives that maintain file directory structure
Chapter 1 - Overview of the Internet
21
Intranets and Extranets





Intranet and Extranet are same as internet, the
difference being in their geographical domains and
level of security they use
Intranet is a network that is contained within an
organization. Outside intruders are not allowed to
access this network
Firewalls are installed around intranets for security
Extranet is an organization network that allows access
to outside networks
Extranet may be viewed as an intermediate network
between internet and intranet
Chapter 1 - Overview of the Internet
22
Intranets and Extranets
Chapter 1 - Overview of the Internet
23
Connecting to the Internet




Internet Service Providers (ISPs) provide access to the
internet by dial-up connection, DSL, or Cable connection
AOL and MSN are ISPs who offer access and content
Phone and cable companies are ISP who offer access only.
Finding the content is users task
Some ISP selection guidelines are:





Maximum connection speed
Type of connection (dial-up or broad band)
Available help line
Software provided
Costs and charges
Chapter 1 - Overview of the Internet
24
Types of Modems


Modem is a device used to transfer data from one
location to another through phone lines
The types of modems are:







Telephone (analog) modem
Cable modem
DSL and ADSL modem
ISDN (digital) modem
B-ISDN modem
Satellite modem
Wireless (cellular) modem
Chapter 1 - Overview of the Internet
25
Internet Tools




Internet tools allow effective use of the internet
These tools are computer programs
Some of these tools are shareware and the others are
freeware
The basic internet tools are:





Web browsers
Virus scan programs
File compression and decompression programs
FTP and Telnet programs
Graphics programs
Chapter 1 - Overview of the Internet
26
Summary
•
•
•
•
•
•
•
The Internet and WWW are simple and enjoyable
concepts to learn
TCP/IP protocol and software transmit data (Web pages,
e-mail messages) across the Internet
Computers use IP addresses and humans use URLs
DNS software provides URL-to-IP-address conversion
Top-level domains: .com, .edu, .gov, .org, .net, and .mil
E-mail addresses use username@DNS-domain format
Intranets and Extranets are private networks
Chapter 1 - Overview of the Internet
27