Transcript - lakshya education hub

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INTERNET
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What Is Internet
• Internet is the global network of networks
• The Internet is a collection of computer networks which
have a common way of passing material between them, in
effect creating a single world-wide network.
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Networking
• Networking
allows
data
transmission
between
computers.
• A network is a set of devices (computers, printers or any
device capable of sending and/or receiving data)
connected by communication links.
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Data Transmission
• Data transmission is the transfer of data from one point
to another. The device which sends data is called
sender, and the device which receives data is called
receiver.
Data Transmission Mode
Data can be transmitted in three different ways. They are:
• Simplex Mode
• Duplex Mode
• Full Mode
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Data Communication (simplex, half-duplex, and full-duplex)
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Data Transmission Speed
• A term used to describe the data-handling capacity of a
communication system is bandwidth. Bandwidth is the
range of frequencies that is available for transmission of
data.
• The data transfer rate is measured in a unit called baud.
• The number of signal sent in one second is called baud
rate.
• Depending on their transmission speed communication
channels are grouped into the following three basic
categories.
 Narrow band
 Voice band
 Broadband
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Narrow Band
• Narrowband or subvoice grade channels range in speed from 45 to
300 baud. They are mainly used for telegraph line and low speed
terminals.
Voice Band
• Voiceband channels handle moderate data volume and can transmit
data at speeds up to 9600 baud. They are so called because there
major application is for ordinary telephone voice communication.
They are used for data transmission from slow I/O devices to CPU
or from CPU to slow I/O device.
Broad Band
• Broadband or wideband channels are used when large volume of
data is to be transmitted at high speed. This system provides data
transmission rate of 1 million baud or more. The use of broadband
facility is for high-speed computer-to-computer communication.
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Data Transmission Media
The path over which data is transmitted is known as data transmission
media. Different types of transmission media are described below.
Twisted Pair Wire
• A twisted pair wire consist of few bunches of thin copper wires, each
bunch enclosed separately in a plastic insulation, then twisted around
each other to reduce interface by adjacent wires.
• They are commonly used for local telephone communication and short
distance digital data transmission. The data transmission speed up to
9600 baud. This cable is inexpensive medium of data transmission. They
are easy to install and use.
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Coaxial Cable
• Coaxial cables are group of specially wrapped wire lines
that are able to transmit data at higher rates.
• They consist of central copper wire surrounded by a
PVC insulation over which a sleeve of copper mesh is
placed. The metal sleeve is again shielded by an outer
shield of thick PVC material.
• The signal transmitted by the inner copper mesh is
placed. The metal sleeve is again shielded by an outer
shield of thick PVC material. The signals transmitted by
the inner copper wore and is electrically shielded b the
other metal sleeve.
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Outer PVC
Shield
Copper Mesh
PVC Shield
insulation
Outer PVC
Shield
Coaxial cables offers much higher bandwidth than twisted pair cable
and are capable of transmitting digital signal of rate of 10 mega bits
per second They are extensively used in long distance telephone
lines and as cables for cable TV.
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Optical Fibers
• Optical fibers are hair-thin threads of glass or plastic that
can serve as a data transmission medium as copper wire
or coaxial cables.
• The basic difference is that optical fibers transmit light
signals instead of electrical signals. Because light wave
travel more fast than electricity.
• Optical fibers can transmit data at much higher speed
than copper wires or coaxial cables and also with no
significant loss of intensity over a long distance.
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Microwave System
• Another popular transmission media is microwave. This is a popular
way of transmitting data since it does not incur the expense of laying
cables.
• Microwave system use very high frequency radio signal to transmit
through space. However at microwave frequencies the
electromagnetic waves cannot bend or passes obstacles like hill.
Hence it is necessary that microwave transmission be in line-ofsight. Microwave system permit data transmission rate about 16
giga bits per second.
Communication Satellite
• A communication satellite is basically a microwave relay station
placed in outer space. These satellites are positioned 36000 kms
above the equator with an orbit speed that exactly matches the earth
rotation speed.
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Data transmission and modes
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Parallel transmission
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Serial transmission
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Asynchronous transmission
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Synchronous transmission
Protocol
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• For data transmission the sender and receiver must
agree a set of communication rules. These rules for
exchanging data between computers are known as
protocol.
• A protocol is a set of rules that govern data
communication.
• A protocol defines what is communicated, how it is
communicated, when it is communicated.
Terms in Network
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•
There are a number of specialized terms that described computer network
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Node: A Node is any device that is connected to a network. It could be a
computer, printer, or data storage device.
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Client: A Client is a node that requests and user available from other nodes.
Typically client is a user’s microcomputer.
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Server: A server is a node that share resources with other node. Depending
on the resources shared it may be called File Server, Print Server,
Communication Server, Web server, or database Server.
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Network operating system: It Control and coordinate the activities between
computers on a network. These activities include e-mail, the shearing of
information and resources.
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Distributed System: In a distributed system computing power is located and
shared at different locations.
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Host computer: A host computer is a large centralized computer usually a
minicomputer
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Topology
•
A network can be arranged in several different ways. This arrangement is
called the networks topology. Different types of topologies are described
below
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Categories of Networks
• LAN - Local Area Network
• MAN- Metropolitan Area Network
• WAN- Wide Area Network
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Local area network (LAN)
• Local Area Network (LAN) is a computer network
covering a small physical area, like a home, office, or
small groups of buildings, such as a school, or an airport.
• The defining characteristics of LAN s, in contrast to wide
area networks (WAN s), include their usually higher
data-transfer rates, smaller geographic area, and lack of
a need for leased telecommunication lines
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Local area network (LAN)
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Metropolitan Area Network (MAN)
• A metropolitan area network (MAN) is a large computer
network that usually spans a city or a large campus. A
MAN usually interconnects a number of local area
networks (LAN s) using a high-capacity backbone
technology, such as fiber-optical links, and provides uplink services to wide area networks
• (or WAN) and the Internet.
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Metropolitan Area Network (MAN)
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Wide Area Network (WAN)
•A wide area network (WAN) is a computer network that
covers a broad area (i.e., any network whose
communications links cross metropolitan, regional, or
national boundaries ).
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Network Interface Cards
• NIC or network card, is a hardware device
that allows a computer to be connected to
a network, both functionally and
physically.
• The NIC is a printed circuit board that is
installed on to one of the expansion slots
of the computer and provides a port on the
back of the computer to which the network
cable is attached.
• NIC is one of the several add-on cards
that the computer may have. Every NIC
have its own unique number called MAC
(Media Access Control) address. No two
NIC's have same MAC address in world.
Bridges
• The bridges are used in to connect two networks having different
transmission medium in two networks one of which uses fiber optic
communication medium and the other uses coaxial cable; or one of
which uses Ethernet technology and other uses token ring
technology. Both the networks must use the same high-level
protocol to communicate.
• Bridges are intelligent devices in the sense that they use a process
of learning and filtering in data forwarding to keep network traffic
within the segment of the network to which it belongs.
• Therefore bridges are also useful in network partitioning, When the
performance of a network segment degrades due to excessive
network traffic it can be broken into two network segments with a
bridge interconnecting.
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Routers
• Unlike bridges routers do not view an internetwork form
end to end. That is, bridges knows the ultimate
destination of a data, but routers only know which is the
next router for the data being transferred across the
network.
• However routers are smarter than bridges in the sense
that they not only copy a data from one network
segment to another, but they also choose the best route
for the data by using information in a routing table to
make this decision. That is managing traffic congestion
is a big pulse of router; they employ a flow control
mechanism to direct traffic on to
alternative less
congested paths.
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Cont.
• Routers are commonly used to interconnect those networks that use
the same communication protocol. They are particularly useful in
controlling traffic flow by making intelligent routing decision.
• An internetwork often uses both bridges and routers to handle both
routing and multiprotocol issues. This requirement has resulted in
the design of devices called Brouters, which are a which is a kind of
hybrid of bridges and routers. They provide many of the advantages
of both bridges and routers.
Gateways
• Gateways are the most sophisticated internetworking
tools and used for interconnecting dissimilar networks
that use different communications architectures. For
instance a gateway may be used to interconnect two
networks one of which uses the IP suite and the other
uses SNA protocol suit.
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History
• The Internet was born about 20 years ago, out of an
effort to connect together a U.S defense department
network called ARPANET (Advance Research Projects
Agency).
• The ARPANET was an experimental network designed
to support military research - in particular
• In the ARPANET model, communication always occurs
between a source and a destination computer.
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NSFNET
• In 1980 the National Science Foundation of U.S. funded
the development of a network named NSFNET.
• In 1993 NSF created the InterNIC to provide Internet
service.
• The purpose to connect the schools, universities,
libraries,….
Who Governs The Internet?
• Internet is not governed by any particular body.
• It has no president or Chief Executive Officer. However, a council of
volunteers, called Internet Architecture Board, of the lAB meets
regularly to approve standards and allocate resources, such as
address.
• Every Internet user has opinion about how the things ought to be
run. Internet users express their opinion through meetings of the
Internet Engineering Task Force (IETF).
• IETF meets regularly to discuss operational and technical problem
of the Internet. When it considers a problem important enough to
merit concern, the lETF sets up a "Working Group" for further
investigation.
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WHO PAYS FOR IT?
Every Internet user or corporation pays for its connection to Internet Service
Provider for the access. Therefore, everyone pays for their pert. Networks get
together and decide how to connect themselves and fund their interconnections
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INTERNET FOR ONE AND FOR ALL
For Student's
: A man who learns for knowledge is always a student.
Whether you are five years old or fifty, if you need any
information on any subject it is the network you
should check out first.
For Business Society
: A ordinary man/woman can develop his/her
business/profession by the use of internet for; market
survey, products availability, scope and market size.
For foreign Trade.
: For people dealing in foreign trade, the internet is of
further advantage. Whether you are into Imports or
exports internet can reduce your communication
costs as well as act as a direct interface between you
and your clients.
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THE INTERNET PROTOCOL
(IP)
• Protocols are the rules that govern how the Internet
works.
• The Internet Protocol takes care of addressing, or
making sure that the routers know what to do with the
data when it arrives.
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WHAT IS AN IP ADDRESS?
An IP address is a unique, numeric identifier used to specify a particular
host on a particular network, and is part of a global, standardized scheme
for identifying machines that are connected to the Internet.
The InterNIC, under the authority of the Internet Assigned Numbers Authority (IANA),
allocates the network portions of IP addresses to Internet Service Providers (ISPs):
ISPs are responsible for assigning the host portion of the IP address to machines
within their local networks. The IP addressing system uses:


The Letter Addressing System
The Number Addressing System
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Transmission control Protocol
• TCP provide process to process, full-duplex and
connection oriented services.
• TCP uses error control to provide reliable service.
• A TCP connection consists of
– Connection Establishment
– Data Transmission
– Connection Termination
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URL's:
• Uniform Resource Locator (URL) is a standard for
specifying any kind of information on the Internet.
• URL defines four things: protocol, host computer, port
and path.
• World Wide Web uses URLs; URL is a way to locate
people, computers, and Internet resources and is used
to identify specific sites and files available on the World
Wide Web.
• Not all URLs will have the directory and filename.
– http://www. Healthyway.conlexercise/mtbike.html
– gopher://figopher.state.edu/
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Domain Name System
• DNS is a client/server application that identifies each
host on the Internet with a unique and friendly name.
• It is a supporting program that is used by other
programs such as e-mail.
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NON GEOGRAPHIC DOMAINS
.com
Commercial organizations
netcom.com, apple.com,
sun.com etc.
.net
Network organizations
intemic.net.
.gov
parts of governments
nasa.gov, oklahoma.gov
etc.
.edu
organizations of higher
education
sjsu.edu, ucsc.edu, mit.edu
etc.
.org
organizations that do not
otherwise fit the commercial or
educational designation,
eff.org, farnet.org etc.
.int
International institutions
(e.g. NATO)
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GEOGRAPHIC DOMAINS
• The geographically based top level domains use two-letter country
designations.
– .us for United States
– .ca for Canada
– .in for India.
• A domain name always contains two or more components separated
by periods, called "dots." internic.net, netsol.com, nasa.gov.
• Domain Name System completes the task of matching domain
names to IP (internet Protocol) addresses. Domain names and their
corresponding IP addresses, must be unique.
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INTERNET CONNECTION OPTIONS
• There are several ways to connect to the
internet.
• Dedicated Internet Access
• PC dial-up access
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Dedicated Internet Access
• It needs a dedicated phone line connecting your LAN or PC to the
Internet 24 Hours a day. A dedicated Internet access requires
substantial initial investment in equipment and a monthly fee for the
use of the line. It varies with line capacity and line capacity
determines how many users can connect to internet simultaneously.
PC Dial-up Access
• It needs a computer modem (attached to a phone line) and any of
the popular telecommunications packages.
• The user dials in to an internet service provider. Each user has an
account on the Internet Services providers host computer.
• User ask the host computer to go out onto the Internet to, do what
you want to be done. Host providers will send & receiver E-mail,
transfer files from a remote internet computer to the host from where
you can then down lead to your own computer.