Transcript internet

Network, Internet and
World Wide Web
Essential Concepts
Natalia Mosina - 2005
Network
• Most people work in a network
environment
A network is a collection of computers
connected together with special hardware
and software to manage it.
LAN – local area network (small area)
WAN – wide area network (long distances)
From LAN to WAN
(a) Home Network
(b) Local Area Network
From LAN to WAN (continued)
(c) Wide Area Network
The Internet and How We Connect
to It Using an ISP
• Explain what the Internet is
Internet
• The Internet is a worldwide collection of
computer networks
• The Internet is a network of networks that
connects users in every country in the
world. There are currently over one billion
Internet users worldwide.
The Internet and How We Connect
to It Using an ISP
• Define an Internet Service Provider and
its purpose
ISP
• An ISP is a company that provides the
connections and support to access the Internet.
• It can also provide additional services such as
Email and web hosting.
• ISPs are essential to gaining access to the
Internet
• ISPs range in size from small to very large and
differ in terms of the area they service.
• ISPs also differ in the types of connection
technologies and speeds they offer
The Internet and How We Connect
to It Using an ISP
• Describe how you connect to the Internet
through the ISP and the ISP’s
relationship to the Internet
PoP
• A POP is the connection point between the
ISP's network and the particular
geographical region that the POP is
servicing.
• An ISP may have many POPs depending
on its size and the area it services
• The Internet is made up of very highspeed data links that interconnect ISP
POPs and ISPs to each other.
• These interconnections are part of the
very large, high capacity network known
as the Internet Backbone.
The Internet and How We Connect
to It Using an ISP
• ISPs provide a variety of ways to
connect to the Internet, depending on
location and desired connection speed.
• The choice of Internet access
technologies depends on availability,
cost, access device used, media used
and the speed of the connection.
The Internet and How We Connect
to It Using an ISP
• The contract with the ISP determines the
type and level of services that are
available.
How Information is Sent When
Using an ISP
• Define and explain that the most
important protocol of the Internet is
the Internet Protocol (IP).
The World Wide Web (www)
• The Web presents information through multimedia
formats: graphics, sound, animation, and video.
• The Web uses several tools to provide a visual layout:
• Hypertext links
• Browser software
• Code structure
• The Web resembles an electronic library – each location or
site is like a book.
• These books are created using Hypertext Markup
Language (HTML).
• These materials, along with interactive objects such as
Java, JavaScript, and VBScript adds functionality to web
pages.
Client vs. Server
• When you connect to Internet to become
part of the web, your computer becomes a
Web client in a worldwide client/server
network.
• Web browser is the software that you run
on your computer to make it work as a
Web client.
A Client/Server Model
• A server (Web server or Web site) is any
computer that stores documents and furnishes
them upon request
• A client is any computer that requests services
(requests and then displays documents )
• Every client must be able to display every
document from every server and does so
through a browser (e.g., Netscape or Internet
Explorer)
•
Connecting to the Internet
• Elements required to connect to the Internet:
• Computer, WebTV, mobile phone, or Personal Digital Assistant
(PDA)
• Dial-up modem, digital subscriber line (DSL) modem, or cable
modem
• Operating System: Windows 95/98/Me, Windows NT/2000/XP,
Linux/UNIX, Macintosh
• Telecommunications/Client Software: Web browser, e-mail or news
client programs
• Internet Connection (telephone line or cable connection): dial-up or
direct connection to an Internet Service Provider (ISP) or ValueAdded Network (VAN) such as America Online (AOL) or Microsoft
Network (MSN)
• Internet Addresses: Web addresses (e.g., www.msn.com), e-mail
addresses (e.g., [email protected]), server addresses (e.g.,
ss1.ProSoftTraining)
Connecting to the Internet
• At Work or School
– Via a Local Area Network
• At Home
– Traditional Modem (56Kbps)
– Cable Modem
• Uses TV cable
• Requires network card
– DSL Modem
• Voice and data on the same line
• Requires network card
•
Connection Types
• Dial-Up Connection
– Use a modem to access the Internet on a per-use basis. The user
accesses the ISP via phone line and when finished, disconnects from
the ISP.
– The speed of access is determined by the speed of your modem.
– To gain faster access, you can install an Integrated Services Digital
Network (ISDN) line, which is a digital phone line.
• Direct Connection
– Provide continuous access to the Internet
– Convenient and fast and capable of handling high bandwidth
Domain Name System (DNS)
• To access a website, you must enter the address of the web
server in your browser.
• The IP address (the dotted quad) is one way to identify the
server; however, most users prefer to use domain names
because they are easier to remember.
• The Domain Name System (DNS) translates IP addresses
into easily recognizable names.
• Examples: IP address: 72.64.56.86
Domain name: www.microsoft.com
Domain Names
• Each domain name is unique. It consists of
letters and numbers separated by dots and
includes two or more words (labels).
• The last label in a domain name is usually a
two- or three-letter code called a top-level
domain.
• Example: www.microsoft.com
Server (Host) Name Registered Company Domain Category
Domain Name
(Top-Level Domain)
Domain Name Syntax
• A domain name, read left to right, specifies
general divisions, then specific companies, and
individual computers (web servers or e-mail
servers)
com = a commercial site
microsoft = the name registered by the company
www = the name of the web server at the company,
also called the web site host
Domain Names
• A fully qualified domain name (FQDN) is the complete
domain name of an Internet computer. It provides enough
information to covert the domain name to an IP address.
• Top-Level Domains
.com = commercial or company sites
.edu = educational institutions
.gov = U. S. civilian government
.mil = U. S. military
.org = organizations
.net = network sites, including commercial ISPs
.int = international organizations
• Two-Letter Country Codes – categorize domains by
country or region. For example: us = United States
au = Australia
Registering a Domain Name
• To register a domain name, your Internet Service
Provider (ISP), your employer, or you must make a
formal request to a domain name registrar.
• In the U. S., the Internet Corporation for Assigned
Names and Numbers (ICANN) verifies which companies
can serve as domain name registrars. The ICANN is
responsible for accrediting its registrars.
• Each country has a different process for registering domain
names.
• Domain name registrars activate domain names using a
first-come, first-served basis.
• If your domain name choice is available, you will receive
notice via standard and electronic mail.
Registering a Domain Name
• Network Solutions (www.networksolutions.com) was
selected as one of the original five registrars.
• Registrars provide the following services:
– Domain name registration
– Registration service forms for domain name transfers,
modifications, etc.
– Resource links for payment options and policies.
– Search capabilities for registered domain names, host IP addresses,
and last name/first name queries using WHOIS (an internet utility
primarily used to query databases to determine registered hosts)
Uniform Resource Locators (URL)
• A URL is a text string that supplies an internet or intranet
address and the method by which the address can be accessed.
• URLs start with the http:// prefix which identifies them as web
pages using the Hypertext Transfer Protocol.
• For example, if you enter the following web address:
http://www.microsoft.com
The URL will access a web page because it begins with http.
It then contacts the web server and domain named
www.icann.org. It will locate a file on the server.
Uniform Resource Locator (URL)
http://www.prenhall.com/reed/index.html
Name of the page
Or document
Web Server
Protocol
(means of
access)
Directory where the
Page is stored
URL
 Top-level domains include “edu,” “gov,” and
“org,” but “com” is most common
 Examples:
 www.microsoft.com
 www.nba.com
 www.whitehouse.gov
 www.miami.edu

Cookies
• Cookies are small text files placed on a website visitor’s
computer so website managers can customize their site to a
visitor’s preferences. They also gain information about
visitors that could be used for marketing needs.
• Unless you register with a site, cookies do not have access to
any personal information about you.
• The text is entered into the memory of the browser. The
browser in turn stores the cookie information on the hard drive
so when the browser is closed and reopened at a later date the
cookie information is still available.
Cookies
• Cookies are small text files placed on a website visitor’s
computer so website managers can customize their site to a
visitor’s preferences. They also gain information about
visitors that could be used for marketing needs.
• Unless you register with a site, cookies do not have access to
any personal information about you.
• The text is entered into the memory of the browser. The
browser in turn stores the cookie information on the hard drive
so when the browser is closed and reopened at a later date the
cookie information is still available.
Web sites use cookies for several
different reasons:
• To collect demographic information about who is
visiting the Web site. Sites often use this
information to track how often visitors come to the
site and how long they remain on the site.
• To personalize the user's experience on the Web
site. Cookies can help store personal information
about you so that when you return to the site you
have a more personalized experience.
Web sites use cookies for several
different reasons:
If you have ever returned to a site and have seen your
name mysteriously appear on the screen, it is because on a
previous visit you gave your name to the site and it was
stored in a cookie so that when you returned you would be
greeted with a personal message.
A good example of this is the way some online shopping
sites will make recommendations to you based on previous
purchases. The server keeps track of what you purchase
and what items you search for and stores that information
in cookies.
Web sites use cookies for several
different reasons:
• To monitor advertisements. Web sites will often use
cookies to keep track of what ads it lets you see and how often
you see ads.
• To collect demographic information about who is
visiting the Web site. Sites often use this information to
track how often visitors come to the site and how long they
remain on the site.
• To personalize the user's experience on the Web site.
Cookies can help store personal information about you so that
when you return to the site you have a more personalized
experience.
Web sites use cookies for several
different reasons:
If you have ever returned to a site and have seen your
name mysteriously appear on the screen, it is because on a
previous visit you gave your name to the site and it was
stored in a cookie so that when you returned you would be
greeted with a personal message.
A good example of this is the way some online shopping
sites will make recommendations to you based on previous
purchases. The server keeps track of what you purchase
and what items you search for and stores that information
in cookies.
Web sites use cookies for several
different reasons:
• To monitor advertisements. Web sites will often use cookies to
keep track of what ads it lets you see and how often you see
ads.
Cookies
• Cookies do not act maliciously on computer systems. They are
merely text files that can be deleted at any time - they are not
plug ins nor are they programs.
• Cookies cannot be used to spread viruses and they cannot
access your hard drive. This does not mean that cookies are
not relevant to a user's privacy and anonymity on the Internet.
• Cookies cannot read your hard drive to find out information
about you; however, any personal information that you give to
a Web site, including credit card information, will most likely
be stored in a cookie unless you have turned off the cookie
feature in your browser. In only this way are cookies a threat
to privacy.
Cookies
• The cookie will only contain information that you
freely provide to a Web site.
Cookies have six parameters that
can be passed to them:
• The name of the cookie.
• The value of the cookie.
• The expiration date of the cookie - this determines
how long the cookie will remain active in your
browser.
• The path the cookie is valid for - this sets the URL
path the cookie us valid in. Web pages outside of that
path cannot use the cookie.
Cookies have six parameters that
can be passed to them:
• The domain the cookie is valid for - this takes the
path parameter one step further. This makes the
cookie accessible to pages on any of the servers
when a site uses multiple servers in a domain.
• The need for a secure connection - this indicates that
the cookie can only be used under a secure server
condition, such as a site using SSL.