Transcript 55f3c79e23c2089x

The Internet,
intranets, extranets
Ch-7-
The Internet
• The largest computer network in the world
• Is a network of networks owned by governments,
universities, nonprofit groups, and companies.
• Exchange information by using the same open,
nonproprietary standards and protocols.
• Connected via high-speed, long-distance backbone
networks.
• Forms a massive electronic communications
network among businesses, consumers, government
agencies, schools, and other organizations
worldwide.
The evolution of the Internet
• The Internet began as one network, called the ARPANET
in 1969.
• ARPANET for military and scientific activities (defense
research).
• ARPANET was split into two networks in 1980.
• UUCP, worldwide UNIX communications network, and
USENET for academic and commercial organizations.
• CSNET and BITNET nationwide networks for academic
and research activities.
• NSFNET linked researchers across the country with five
supercomputer centers.
The Internet Today
• In 1998, less than 2 percent of the world’s adults had access to
the Internet.
• In 2001, 500 million people worldwide were Internet users
• In June 2012,
Internet Divide 2013
• Countries with a higher gross domestic product per person
will have higher rates of personal computer ownership and
higher Internet adoption rates than those with lower GDP
figures.
Infrastructure of the Internet
• Commercial communications companies provide
largely the physical network backbone of the
Internet.
• U.S government and the National Science
Foundation (NSF) contribute some funds to
essential administrative processes, such as
standards development and the domain name
system (DNS), through contracts with private
organizations that perform these functions.
• The Internet infrastructure is supplied by
network service providers such as UUNET, MCI
WorldCom company, GTE Internetworking, etc.
• Businesses and individual subscribers connect to
the Internet through these and other smaller
Internet Service providers.
• The provider may be a large backbone provider,
or may be a smaller local company connecting to
the larger network service provider.
• ISP: Internet service providers are both
backbone and access providers.
• Backbone providers should be connected to one another and
to access providers over backbone networks.
How the Internet work?
Fred
Zip
Frontier
Customer
Public Peering
Point
Frontier
MCI
Peer
WorldCom
Sprint
Peer
ISP
Susan
How The Internet Works?
• The ISP maintains a pool of modems for
their dial-in customers.
• This is managed by some form of
computer (usually a dedicated one), which
controls data flow from the modem pool
to a backbone or dedicated line router.
This setup may be referred to as a port
server, as it 'serves' access to the network.
Billing and usage information is usually
collected here as well.
• After the packets traverse the phone
network and the ISP's local equipment,
they are routed onto the ISP's backbone or
a backbone the ISP buys bandwidth from.
• From here the packets will usually journey
through several routers and over several
backbones, dedicated lines, and other
networks until they find their destination,
the computer with address 5.6.7.8 (for
example).
Internet Protocol (IP)
• The set of rules used to send and
receive packets from one machine to
another over the Internet.
• The IP and TCP protocols are
commonly used together that they
are referred to as the TCP/IP protocol.
• The Internet is packet-switching
network.
Internet Addresses
• Each computer connected to the Internet has a unique
address called IP address (IP stands for Internet
Protocol) .
• Internet addresses are in the form ###.###.###.###
where ### must be a number from 0 - 255.
• If you connect to the Internet through an Internet
Service Provider (ISP), you are usually assigned a
temporary IP address for the duration of your dial-in
session.
• If you connect to the Internet from a local area network
(LAN) your computer might have a permanent IP address
or it might obtain a temporary one from a DHCP
(Dynamic Host Configuration Protocol) server.
Here are some example IP
Addresses:
• 64.54.23.198
• 244.32.121.100
• 209.178.41.76
• 132.62.128.91
Domain Name
• Consist of multiple parts, separated by dots, and are
translated from right to left.
• For example: “software.ibm.com”:
Com is the name of the top-level specification or the zone.
Ibm is the name of the company
Software is the name of the computer within the company
to which the message is being sent.
• The rightmost two letters in a domain name, if present,
represent the country of the website.
• For example:
“us”, ”ru”, ”it”, ”uk”, ”ca”, ”fr”
Domain Name
• "DNS" is "Domain Name service," and it provides a
facility to substitute more human-friendly names for
IP Addresses
• DNS was designed to map IP Addresses to computer
names
• DNS names typically have three parts:
The computer's name, also called the "hostname."
The responsible organization's name or
abbreviation.
A suffix that identifies the type of organization or its
country of origin.
Domain Name
• Network names, such as 'unc.edu,' are
commonly referred to as 'Domain Names' or just
'Domains.'
• Full/specific names, such as 'www.unc.edu,' are
often referred to as 'fully-qualified hostnames' or
just 'hostnames.‘
• When an organization decides it needs a Domain
Name for its network, a representative of that
organization contacts a 'Domain Name Registrar'
to register the name.
• This Domain Name Registrar is an organization
(usually a commercial company) that has the ability
to save new Domain Names to the Top-Level Servers
and ensure their uniqueness.
• Organizations are not allowed to choose a Domain
Name that is already in use, and they cannot
permanently own those names. Domain Names are
leased, like automobile leases. In order to keep a
Domain Name, an organization must continue to
renew the lease before it expires. If a lease expires
without being renewed, the Domain Name becomes
available for other organizations to lease it.
Accessing the Internet
• Connect via LAN server
• Connect Via Serial Line Internet
Protocol/Point-to-Point Protocol
(SLIP/PPP)
• Connect via online service.
Connect via LAN server
• The user’s computer must have a communications stack
• Communications stack:
Is specialized software that provides a set of communications
protocols that perform the complete functions of the seven
layers of the OSI communications model.
• Speed of 56kbps or faster
• Expensive but cost spread over many users.
Connect via SLIP/PPP
• Users should have modem and specialized software that
allows them to dial into a SLIP/PPP server through a service
provider .
• Company’s intranet or employees who work at home.
Connect via online service
• Requires a modem, standard communications software, and
an online information service account with an Internet service
provider.
How can you connect to the
Internet?
Slow-speed
technology
Dial-up access
modem in your
computer uses a
standard telephone line
to connect to the Internet
Connection must be established
each time you log on.
Slow but inexpensive
High-speed
connection
Digital subscriber line (DSL),
cable telephone Internet
services (CATV), cable modem,
fixed wireless, and satellite modems
Connection is always on—
whenever the computer
is running
Most Internet access methods used in homes involve a small
hardware unit called a modem that connects to a physical
medium supporting one of these fixed location services:
• phone line (for DSL)
• cable Internet (CATV) line
• fiber optic cable
• wireless antenna (for satellite and wireless broadband
services)
• Portable computers, like tablets, can be connected to fixed
location networks inside a home, but they additionally
support mobile broadband Internet access via cellular
networks that can be used at home and while traveling.
• outside the home, portable computers can also reach the
Internet via Wi-Fi hotspots, hardware access points installed in
fixed locations that are in turn networked to Internet service
through one of the other above methods.
Who controls the Internet?
 No one — it is
a public, cooperative, and
independent network
 Several organizations set standards
c
c
World Wide Web
Consortium (W3C)
Oversees research, sets 
standards and guidelines
Tim Berners-Lee, director 
Internet2 (I2)
Internet-related research 
and development project
Develops and tests 
advanced Internet
technologies
What is the World Wide Web?
A worldwide collection of electronic documents
Also called the Web
Each electronic document is called a Web page
Can contain text, graphics, sound, video, and built-in connections
A Web site is a collection of related Web pages
World Wide Web
• The Internet functions as the transport mechanism
• www or W3 is an application that uses those transport
functions.
• E-mail is another application run on the Internet.
• Web is a system with universally accepted standards for
storing, retrieving, formatting and displaying information via a
client/server architecture.
• Web uses GUI.
• Web is based on a standard hypertext language called
Hypertext Markup Language (HTML)
• Offering information through the Web requires establishing a home
page.
• Home page : is a text and graphical screen display that usually
welcomes the user and explains the organization that has
established the page.
• Home page lead users to other pages.
• Web site: is all the pages of a particular company or individual.
• Uniform Resource Locator (URL): is the address of a specific
resource on the Web, e.g. : URL for Microsoft is
http://www.microsoft.com
• URL: Unique address for a Web page:
A web server delivers the Web page to your computer
• HTTP: Hypertext Transport Protocol which is the
communications standard used to transfer pages across the
WWW.
• HTTP: defines how messages are formatted and transmitted
and what actions Web servers and browsers should take in
response to various commands.
• Browser: is a software application used by users to access the
Web.
• A Browser is able to communicate via HTTP, managing HTML,
and displaying different data types.
What is a Web browser?
• Program that allows you to view Web pages
Microsoft
Internet
Explorer
Safari
Netscape
Mozilla
Opera
Internet Regulation
• Technical organizations such as the Internet Engineering Task
Force and the World Wide Web Consortium, define the
standards that govern the Internet’s functionality.
• Regulate the content of Internet-connected computers:
Privacy, security and the legal liability of service providers.
• Some content providers have addressed these issues with:
Filters, ratings, and restricted address.
Internet Expansion
• Slowdowns in retrieval time, unreliable transmission of
streamed data, and denial of service by overloaded servers.
• Causes of slowdowns:
Improperly configured networks
Overloaded servers
Rapidly changing Internet usage patterns
Too much traffic for available bandwidth
• Solutions:
Installing high-speed transmission media
Bigger, faster routers
More sophisticated load balancing and management software
Local caching of frequently requested Web pages to improve
response time
Internet Privacy
• Websites collect information with and without consumers’
knowledge.
• Through: registration (Amazon.com)
• Clickstream data:
Information about where people go within a Web site and the
content they see.
• Clickstream data are collected by cookies.
• Cookie:
Is a small data file placed on users’ hard drives when they first
visit a site.
Intranet
• A private network that uses Internet software and TCP/IP
protocols.
• A private Internet , or group of private segments of the public
Internet network, reserved for use by people who have been
given the authority to use that network.
• Common applications on intranets:
Document sharing
Corporate telephone directories
Human resources forms
Training programs
Search engines
Customer databases
Intranet security
• Public key security ( encryption and certificate authorities)
• Encryption: scrambles outgoing data
• Digital certificate: like electronic Identification cards to ensure
that the person trying to access is a valid user.
• ValiCert is the leader in the certificate authority market.
• Firewall: is a device located between a firm’s internal network
and external networks.
• Firewall regulates access into and out of a company’s network.
• Firewall examines only the header of a packet
• Assured pipeline examines the entire request for data and
then determines whether the request is valid.
Extranet
• Interorganizational information system
• Enable people who are located outside a company to work
together with the company’s internally located employees.
• Networks that link business partners to one another over the
Internet.
• Extranet= extended intranet
• Closed to the general public
• Extranet uses virtual private network (VPN) technology to
make communications over the Internet more secure.
Types of extranets
• A company and its dealers, customers, or suppliers
• An industry’s extranet:
the major players in an industry may team up to create an
extranet that will benefit all.
• Joint ventures and other business partnerships:
Several companies partner on a joint venture and use the
extranret as a vehicle for communications and collaboration
Enterprise Information Portals
• EIP:
Web-based applications that enable companies to access
internally and externally stored information, and provide users a
single point of access to personalized information needed to
make informed business decisions.
• EIPs integrate:
Content management, business intelligence, data warehouse,
data mart and data management applications.
Mobile Internet
• Refers to the use of wireless communications technologies to
access network-based information and applications from
mobile devices.
• Mobile Internet= wireless Web
How do handheld computers
and cellular telephones access
the Web?
 Use a
microbrowser that displays Web pages that
contain mostly text
 Must be
Web-enabled