Transcript internet fundamentals

INTERNET
FUNDAMENTALS
The Internet
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A vast network of networks that electronically connects millions of
people worldwide.
Formed in 1968, when the U. S. Department of Defense’s Advanced
Research Projects Agency (ARPA) funded what would become the
first global computer network—the Advanced Research Projects
Agency Network (ARPANET).
The ARPANET allowed university and government engineers to
research and work from any location on the network.
In the late 1980s, the Department of Defense decommissioned the
ARPANET, and all sites switched over to the National Science
Foundation network, called NSFnet.
The NSFnet, plus thousands of others, compose what has become the
largest network of networks: the Internet.
The World Wide Web (www)
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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.
How the Internet Works
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Internet communication is made possible by the
Transmission Control Protocol/Internet Protocol (TCP/IP)
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software on your computer.
This software sends information to the computer with
which you are connected, which then passes it on to other
computers until it reaches its destination.
TCP/IP ensures that your information is transferred quickly
and reliably. It divides your data into packets and sends
each packet separately across the Internet.
The routing flexibility of TCP/IP software ensures the
accurate and steady flow of information, regardless of any
one user’s connection.
Internet Protocols
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Hypertext Transfer Protocol (HTTP)
The set of rules required to exchange files, such as text, images, video, and
multimedia content, across the Web. Files contain references to other files, so
they are “linked” to one another.
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File Transfer Protocol (FTP)
Used to access programs and transfer files across the Internet.
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Simple Mail Transfer Protocol (SMTP) – Electronic Mail
Involves an outgoing and incoming mail server. You receive e-mail from an
incoming mail server using the Post Office Protocol (POP) or the Internet
Message Access Protocol (IMAP).
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Telnet
The Internet standard protocol for remote terminal connection service. Some
public Telnet servers are still widely used by administrators to remotely
manage servers, firewalls, and routers.
Internet Protocols
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Network News Transfer Protocol (NNTP) - Newsgroups
After registering with a newsgroup, you can read and post
news
Gopher (An older menu-based program in UNIX-based
systems used to find resources)
One of the first tools developed to unite the Internet so that
users could access the entire Internet rather than just one
site. Gopher allows you to browse for information (usually
text-based) without having to know exactly where the
information is located. Most Gopher servers have been
replaced with HTTP (Web) servers.
The Difference Between
FTP and HTTP
FTP
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File Transfer Protocol, or FTP, is a protocol used
to upload files from a workstation to a FTP server
or download files from a FTP server to a
workstation.
It is the way that files get transferred from one
device to another in order for the files to be
available on the Internet.
When ftp appears in a URL it means that the user
is connecting to a file server and not a Web server
and that some form of file transfer is going to take
place.
FTP
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Most FTP servers require the user to log on
to the server in order to transfer files.
HTTP
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In contrast, Hyper Text Transfer Protocol, or
HTTP, is a protocol used to transfer files from a
Web server onto a browser in order to view a Web
page that is on the Internet.
Unlike FTP, where entire files are transferred from
one device to another and copied into memory,
HTTP only transfers the contents of a web page
into a browser for viewing.
FTP is a two-way system as files are transferred
back and forth between server and workstation.
HTTP
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HTTP is a one-way system as files are transported
only from the server onto the workstation's
browser.
When http appears in a URL it means that the user
is connecting to a Web server and not a file server.
The files are transferred but not downloaded,
therefore not copied into the memory of the
receiving device.
Connecting to the Internet
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Elements required to connect to the Internet:
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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): dialup or direct connection to an Internet Service Provider (ISP) or
Value-Added Network (VAN) such as America Online (AOL) or
Microsoft Network (MSN)
Internet Addresses: Web addresses (e.g., www.msn.com), email addresses (e.g., [email protected]), server addresses
(e.g., ss1.ProSoftTraining)
Connection Types
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Dial-Up Connection
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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
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Provide continuous access to the Internet
Convenient and fast and capable of handling high bandwidth
Domain Name System (DNS)
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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
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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
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A domain name, read left to right, specifies
general divisions, then specific companies,
and individual computers (web servers or email 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
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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
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Two-Letter Country Codes – categorize domains by
country or region. For example: us = United States
au = Australia
Registering a Domain Name
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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
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Network Solutions (www.networksolutions.com) was
selected as one of the original five registrars.
Registrars provide the following services:
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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)
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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.
INTERNET SECURITY
Internet Security
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The Internet harbors many security hazards.
Most hazards can be avoided using your browser and virus
protection.
Other security features include:
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Hypertext Transfer Protocol Secure (HTTPS)
Authentication (verifying the identity of the user)
Digital Certificates (equivalent to an ID card and digitally
signed by the creator of the certificate)
Encryption (reduces the possibility of information theft by
scrambling information using mathematical algorithms;
encrypted text cannot be understood by anyone with the correct
encryption key)
Firewalls (restrict unauthorized users, retain control of private
information, and prevent unauthorized export of proprietary
information)
Firewalls
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Personal firewalls are available for individuals’ computers.
They offer protection for an individual system rather than
an entire network (used by businesses).
Tools for Windows Systems
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Zone Alarm – www.zonealarm.com
Black Ice – www.networkice.com
Firewalls
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Inspect all incoming traffic for security threats
When used in conjunction with anti-virus software, a personal
computer is very secure, provided that the user updates the antivirus and personal firewall software frequently.
Example of Firewall
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Firewalls are systems that establish access control policies among
networks. They can block information from entering a network or
from getting out of that network, they can permit different users to
perform different kinds of operations, according to the user's
authorizations.
Do Cookies Compromise
Security?
Cookies
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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:
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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:
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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.
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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.
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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:
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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
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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
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The cookie will only contain information that you
freely provide to a Web site.
Cookies have six parameters
that can be passed to them:
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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:
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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.
Cookies in Netscape and
Internet Explorer
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Both Netscape and Microsoft Internet Explorer (IE) can be
set to reject cookies if the user prefers to use the Internet
without enabling cookies to be stored.
In Netscape, follow the Edit/ Preferences/ Advanced
menu and in IE, follow the Tools/Internet
Options/Security menu to set cookie preferences.
For more information, see:
The Electronic Privacy Information Center
The Unofficial Cookie FAQ