The Internet is a global system of interconnected computer networks that use TCP/IP protocols to link billions of devices worldwide. It consists of private, public, academic, business and government networks linked through a variety of networking technologies carrying a wide range of information and services. Research into packet switching networks in the 1960s and 1970s led to the development of early networks like ARPANET that eventually evolved into the Internet.

4. WHAT IS INTERNET ???
The Internet is the global system of interconnected computer networks that use the Internet
protocol suite (TCP/IP) to link billions of devices worldwide. It is a network of networks that
consists of millions of private, public, academic, business, and government networks of local to
global scope, linked by a broad array of electronic, wireless, and optical networking
technologies. The Internet carries an extensive range of information resources and services,
such as the inter-linked hypertext documents and applications of the World Wide Web
(WWW), electronic mail, telephony, and peer-to-peer networks for file sharing.
Research into packet switching started in the early 1960s, and packet switched networks such
as the ARPANET, CYCLADES, the Merit Network, NPL network, Tymnet, and
Telenet, were developed in the late 1960s and 1970s using a variety of protocols.

5. ARPANET development began with two
network nodes which were interconnected
between the Network Measurement Center
at the University of California, Los Angeles
(UCLA) Henry Samueli School of
Engineering and Applied Science directed
by Leonard Kleinrock, and the NLS system
at SRI International (SRI) by Douglas
Engelbart in Menlo Park, California, on 29
October 1969. The third site was the
Culler-Fried Interactive Mathematics
Center at the University of California,
Santa Barbara, followed by the University
of Utah Graphics Department. In an early

7. There are many ways a personal electronic device
can connect to the internet. They all use different
hardware and each has a range of connection
speeds. As technology changes, faster internet
connections are needed to handle those changes.

9. Dial-up access is cheap but slow. A modem (internal or
external) connects to the Internet after the computer dials a
phone number. This analog signal is converted to digital via
the modem and sent over a land-line serviced by a public
telephone network. Telephone lines are variable in quality
and the connection can be poor at times. The lines regularly
experience interference and this affects the speed, anywhere
from 28K to 56K. Since a computer or other device shares the
same line as the telephone, they can’t be active at the same
time.
Shell Connection: In this type of Internet Connection, the
user will get only textual matter of a Web Page. This
connection does not support Graphics display.Shell Accounts
were the only type of Internet access available for many years
before the Internet entered in to the world of graphics and
became more users friendly.

10. provide easier access with multimedia sound and
pictures. The major difference between Shell and
TCP/IP account is that, Shell account can only
display text and does not support graphics display,
whereas TCP/IP can display both.
ISDN:
ISDN (Integrated Services Digital Network) offers
Internet connectivity at speeds of up to 128 Kbps
through the use of digital phone lines. ISDN is a
dial-up service that has been provided by
telephone companies for many years.
To access any of these dial-up accounts you need
the followings;
• Computer
• Modem
• Telephone Connection

11. DSL
DSLstands for Digital Subscriber Line. It is an internet connection that
is always “on”. This uses 2 lines so your phone is not tiedup when your
computer is connected. There is also no needto dial a phone number to
connect. DSL uses a routerto transport data and the range of connection
speed, depending on the service offered, is between 128Kto 8 Mbps.
ADSL stands for asymmetric DSL, and its distinguishing characteristic is
that the uploadand downloadspeeds are different. Usually the
download speed is faster than your upload speed, and this is because the
typical user will be downloading things more often than uploading
things.
SDSLstands for symmetric DSL, and its distinguishing characteristic is
that the uploadand downloadspeeds are the same.

12. Advantages:
• Security: Unlike cable modems, each subscriber can be configured so that it will not be on
the same network. In some cable modem networks, other computers on the cable modem
network are left visibly vulnerable and are easily susceptible to break in as well as data
destruction.
• Integration: DSL will easily interface with ATM and WAN technology.
• High bandwidth
• Cheap line charges from the phone company.
• Good for “bursty” traffic patterns
Disadvantages :
• No current standardization: A person moving from one area to another might find that
their DSL modem is just another paperweight. Customers may have to buy new equipment to
simply change ISPs.
• Expensive: Most customers are not willing to spend more than $20 to $25 per month for
Internet access. Current installation costs, including the modem, can be as high as $750.
Prices should come down within 1-3 years. As with all computer technology, being first
usually means an emptier wallet.
• Distance Dependence: The farther you live from the DSLAM (DSL Access Multiplexer), the
lower the data rate. The longest run lengths are 18,000 feet, or a little over 3 miles.

13. CABLE
Cable provides an internet connection through a cable modemand operates over
cable
TV lines. There are different speeds depending on if you are uploading data
transmissions or downloading. Since the coax cable provides a much greater
bandwidthover dial-upor DSL telephone lines, you can get faster access. Cable
speeds range from512K to 20 Mbps.
Advantages :
• Always Connected: A cable modemconnection is alwaysconnectedto the Internet.
This is advantageous becauseyou do not haveto wait for your computer to “log on”
to the Internet; however, this also has the disadvantage of making your computer
more vulnerable to hackers. Broadband: Cable modems transmit and receive data
as digital packets, meaning theyprovide high-speed Internet access. This makes
cable modemconnections muchfaster than traditional dial-upconnections.

14. • Bandwidth: Cable modems have the potential to receivedata from their cable provider at speeds
greater than 30 megabits per second; unfortunately, this speed is rarelyeverrealized. Cable lines
are sharedby all of the cable modemusersin a given area; thus, the connection speedvaries
dependingupon the number of other people usingthe Internet and the amount of datatheyare
receiving or transmitting.
• File Transfer Capabilities: Downloads may be faster, but uploadsare typicallyslower. Since the
same linesare used to transmit datato andfrom the modem, priorityis often given to data
traveling in one direction.
• Signal Integrity: Cable Internet can be transmittedlong distanceswithlittlesignal degradation.
This means the qualityof the Internet signal is not significantlydecreased by the distance of the
modemfrom the cableprovider.
• Routing: Cablerouters allowmultiplecomputersto be hookedup to one cable modem, allowing
several devices to be directlyconnected througha single modem. Wireless routerscan also be
attached to your cable modem.
• Relyon Existing Connections: Cablemodemsconnect directlyto preinstalled cablelines. This is
advantageous because you do not need to have other services, such as telephone or Internet, in
order to receive Internetthroughyourcable modem. The disadvantage is that youcannot have
cable internet in areas where there are no cable lines.

15. Disadvantages :
• Cable internet technology excels at maintaining signal strength
over distance. Once it is delivered to a region, however, such as
a neighborhood, it is split among that regions subscribers. While
increased capacity has diminished the effect somewhat, it is still
possible that users will see significantly lower speeds at peak
times when more people are using the shared connection.
• Bandwidth equals money, so cable’s advantage in throughput
comes with a price. Even in plans of similar speeds compared
with DSL, customers spend more per Mb with cable than they
do with DSL.
• It’s hard to imagine, but there are still pockets of the United
States without adequate cable television service. There are far
fewer such pockets without residential land-line service
meaning cable internet is on balance less accessible in remote
areas.

17. infrastructure
In spite the fact that satellite internet is the most
expensive form of broadband internet, many
subscribers are using satellite. The biggest
advantage of the satellite internet is that it is
available anywhere. If you have all needed equipmen
(satellite dish, transceiver and modem), you can
have the high speed internet connection everywhere.
Unlike from all other internet providers, satellite
internet providers don’t have any need for extra
infrastructure.
All other service providers provide connection usually
to the urban areas, with a dense concentration of
the customers. They bring their infrastructure to
the area with enough customers, to make their
investment in the infrastructure profitable.

18. Disadvantages :
•high cost
•relatively slower
•big latency
High speed satellite internet can be quite expensive. The reason for
higher price is they need to cover the following cost:
•installation
•expensive equipment
•shipping of the quite big and heavy equipment
•activation fee.
Some satellite providers charge you for dish rental or even for
a whole price of the dish. It is important that you keep an eye on
these hidden costs.
The initial cost of the installation and activation of the service could
be very high, but the most of these charges are often negotiable.

19. connection.
It is the access to the Internet from a
network, which is not on the Internet. The
gateway allows the two different types of
networks to “talk” to each other. But the
users of the Gateway Internet have limited
access to the Internet. They
might not be able to use all the tools
available on Internet. The local Internet
Service Provider (ISP) normally defines this
limitation. Good example of network with
Level One connectivity within India is that of
VSNL (Videsh Sanchar Nigam Limited). All

21. VSAT
Short for very small aperture terminal, an earthbound station used in satellite
communications of data, voice and video signals, excluding broadcast television. A VSAT
consists of two parts, a transceiver that is placed outdoors in direct line of sight to the
satellite and a device that is placed indoors to interface the transceiver with the end
user’s communications device, such as a PC. The transceiver receives or sends a signal to
a satellite transponder in the sky. The satellite sends and receives signals from a ground
station computer that acts as a hub for the system. Each end user is interconnected with
the hub station via the satellite, forming a star topology. The hub controls the entire
operation of the network. For one end user to communicate with another, each
transmission has to first go to the hub station that then retransmits it via the satellite to
the other end user’s VSAT.

22. Advantages:
Satellite communication systems have some advantages that can be
exploited for the provision of connectivity. These are:
• Costs Insensitive to Distance
• Single Platform service delivery (one-stop-shop)
• Flexibility
• Upgradeable
• Low incremental costs per unit
Disadvantages:
However like all systems there are disadvantages also. Some of these
are
• High start-up costs (hubs and basic elements must be in place
before the services can be provided)
• Higher than normal risk profiles
• Severe regulatory restrictions imposed by countries that prevent
VSAT networks and solutions from reaching critical mass and
therefore profitability
• Some service quality limitations such the high signal delays
(latency)
• Natural availability limits that cannot be mitigated

25. Tier 1 or T1 is a digital line that is
usually private and used for businesses.
The businesses that use T1 tend to have
more control over their line than other
options. It also is considered more
reliable. Its speeds are roughly the same
or lower than Cable and DSL, reaching
up to 1.5Mbitps upload and download.
This upload/download isn't amazing,
however T1 lines do well for smaller
businesses.

28. Theterm‘wireless’is a bigcatch-alltermto cover
anytypeof Internetaccessthatdoesn’trequirea
cablebetweenyouandyourISP. Thismakesit
importantfor youto aska fewquestionsbefore
signingup for ‘WirelessInternet’.Eachtypeworks
a littlebitdifferentlyandhasit’sownprosand
cons.

31. Types of Wireless Networks
: