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Data Communication & Computer Network
A computer network, sometimes referred to as a data network,
is a type of telecommunications network that permits the
exchange of data between computers
...
" The physical connection between
networked computing equipment is made through cable or
wireless media
...

You will learn the principles of Data Communication and
Computer Network (DCN) in this session in addition to a number
of advanced concepts related to DCN
...
The exchanging of
information between computers is made easier by this link
...

Network Engineering
The complex task of networking engineering includes the use of
hardware, electric pulses, chip-level engineering, software, and
firmware
...
Each layer is
independent of the others and is involved in a specific task
...
Layers exchange information
and rely entirely on one another to receive input and provide
output
...

The internet vastly connects all WANs and can connect to LANs
and home networks, making it the biggest network on the earth
...
Today, IPv4 is commonly used for
Internet implementation
...

Users of the internet can share and access a vast amount of
information on a global scale
...
Internet utilizes
a Client-Server architecture at a large scale
...
To interconnect various continents, fibers are laid under sea known to
us as submarine communication cable
...
They provide numerous advantages:
•
•
•
•
•

Resource sharing such as printers and storage devices
Exchange of information by means of e-Mails and FTP
Information sharing by using Web or Internet
Interaction with other users using dynamic web pages
IP phones

•
•
•

Video conferences
Parallel computing
Instant messaging

Computer networks are collections of connected computers and
computerized devices like printers
...

Computers can communicate with one another wirelessly or
over wired networks
...
They
includes:
Geographical span
• Inter-connectivity
• Administration
• Architecture
Geographical Span
•

Geographically a network can be seen in one of the following
categories:
•

•

•
•
•

It may be spanned across your table, among
Bluetooth enabled devices,
...

It may be spanned across a whole building, including
intermediate devices to connect all floors
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It may be spanned across multiple cities or provinces
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Inter-Connectivity
Components of a network can be connected to each other
differently in some fashion
...

Every single device can be connected to every other
device on network, making the network mesh
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• Each device is connected to its left and right peers
only, creating linear structure
...

• All devices connected arbitrarily using all previous
ways to connect each other, resulting in a hybrid
structure
...
A network can
be public which is accessed by all
...

•

There can be one or more systems acting as Server
...
Server takes and processes request on
behalf of Clients
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They both reside at the same
level and called peers
...

Network Applications
Computer systems and peripherals are connected to form a
network
...
A network can span the entire world and be as little as the
space between your smartphone and Bluetooth headphones or
as huge as the internet itself
...
This may include Bluetooth enabled devices

or infra-red enabled devices
...
PAN may include wireless computer keyboard and
mouse, Bluetooth enabled headphones, wireless printers and TV
remotes
...

Local Area Network
A computer network spanned inside a building and operated
under single administrative system is generally termed as Local
Area Network (LAN)
...
Number of systems connected
in LAN may vary from as least as two to as much as 16 million
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The resources such as printers, file servers, scanners, and
internet are easily sharable among computers
...
It may contains local servers serving file storage and
other locally shared applications
...
LAN works
under its own local domain and controlled centrally
...
Ethernet is
most widely employed LAN technology and uses Star topology,
while Token-ring is rarely seen
...

Metropolitan Area Network
The Metropolitan Area Network (MAN) generally expands
throughout a city such as cable TV network
...

Metro Ethernet is a service which is provided by ISPs
...
For

example, MAN can help an organization to connect all of its
offices in a city
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MAN works in between Local Area Network and Wide Area
Network
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Wide Area Network
As the name suggests,the Wide Area Network (WAN) covers a
wide area which may span across provinces and even a whole
country
...
These networks provide connectivity to MANs and
LANs
...


WAN may use advanced technologies such as Asynchronous
Transfer Mode (ATM), Frame Relay, and Synchronous Optical
Network (SONET)
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Internetwork
A network of networks is called an internetwork, or simply the
internet
...
The
internet hugely connects all WANs and it can have connection to
LANs and Home networks
...
Present day, Internet is
widely implemented using IPv4
...

Internet enables its users to share and access enormous amount
of information worldwide
...
At huge level, internet works on
Client-Server model
...
To interconnect various continents, fibers are laid under sea known to
us as submarine communication cable
...
When a user requests a page using some web
browser located on some Web Server anywhere in the world, the
Web Server responds with the proper HTML page
...

Internet is serving many proposes and is involved in many
aspects of life
...
This technology
was invented by Bob Metcalfe and D
...
Boggs in the year 1970
...
3 in 1980
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Network which uses shared media has
high probability of data collision
...
On the occurrence of collision in Ethernet, all
its hosts roll back, wait for some random amount of time, and
then re-transmit the data
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This helps other Ethernet devices to identify
and communicate with remote devices in Ethernet
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The number
10 depicts 10MBPS speed, BASE stands for baseband, and T
stands for Thick Ethernet
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Ethernet follows star
topology with segment length up to 100 meters
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Fast-Ethernet
To encompass need of fast emerging software and hardware
technologies, Ethernet extends itself as Fast-Ethernet
...
It can provide speed up
to 100 MBPS
...
2
using Cat-5 twisted pair cable
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Fast Ethernet on fiber is defined under 100BASE-FX standard
which provides speed up to 100 MBPS on fiber
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Giga-Ethernet
After being introduced in 1995, Fast-Ethernet could enjoy its
high speed status only for 3 years till Giga-Ethernet introduced
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IEEE802
...
IEEE802
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Virtual LAN
LAN uses Ethernet which in turn works on shared media
...
Introduction of switches to Ethernet has
removed single collision domain issue and each device
connected to switch works in its separate collision domain
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Virtual LAN is a solution to divide a single Broadcast domain into
multiple Broadcast domains
...
By default, all hosts are placed into the same
VLAN
...
Hosts in one VLAN, even if connected on the same Switch
cannot see or speak to other hosts in different VLANs
...
To route
packets between two different VLANs a Layer-3 device such as
Router is required
...

Topologies may define both physical and logical aspect of the

network
...


Point-to-Point
Point-to-point networks contains exactly two hosts such as
computer, switches or routers, servers connected back to back
using a single piece of cable
...


If the hosts are connected point-to-point logically, then may
have multiple intermediate devices
...

Bus Topology
In case of Bus topology, all devices share single communication
line or cable
...
Therefore, Bus topology
either uses CSMA/CD technology or recognizes one host as Bus
Master to solve the issue
...
But failure of the shared communication line can make
all other devices stop functioning
...
The data
is sent in only one direction and as soon as it reaches the extreme
end, the terminator removes the data from the line
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That is,
there exists a point to point connection between hosts and hub
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If hub fails,
connectivity of all hosts to all other hosts fails
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Star topology is not expensive as to connect one more host,
only one cable is required and configuration is simple
...
When one
host tries to communicate or send message to a host which is
not adjacent to it, the data travels through all intermediate
hosts
...


Failure of any host results in failure of the whole ring
...
There are methods
which employ one more backup ring
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This topology has hosts in point-to-point connection with
every other host or may also have hosts which are in point-topoint connection to few hosts only
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Mesh technology comes
into two types:
•

•

Full Mesh: All hosts have a point-to-point connection
to every other host in the network
...
It
provides the most reliable network structure among
all network topologies
...
Hosts connect to each
other in some arbitrarily fashion
...


Tree Topology
Also known as Hierarchical Topology, this is the most common
form of network topology in use presently
...

This topology divides the network in to multiple levels/layers of
network
...
The lowermost is access-layer where
computers are attached
...
The highest layer is known as core layer, and is
central point of the network, i
...
root of the tree from which all
nodes fork
...
Similar to the Bus topology, if the root goes down, then the
entire network suffers even
...
Every connection serves as point of failure, failing of
which divides the network into unreachable segment
...
Similar to
Ring topology, all hosts are connected to two hosts only, except
the end hosts
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Each link in daisy chain topology represents single point of
failure
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Every intermediate host works as relay for its
immediate hosts
...
Hybrid topology inherits
merits and demerits of all the incorporating topologies
...
The
combining topologies may contain attributes of Star, Ring, Bus,
and Daisy-chain topologies
...
Internet is the best example of
largest Hybrid topology



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