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Jan 31, 2013 (4 years and 7 months ago)

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Summary of LAN hardware for the network design:


LAN network

LAN
hardware

Description

Problem

To connect
two
computers

NIC

Network interface card for
connecting two computers
on LAN

Cannot connect over
long distances

To connect
two
computers
over long
distances

Repeater

Extends the distance
limitations of Ethernet
cable by boosting the signal

Only two computers
can be connected if you
want to connect more
computers then it is a
problem

To connect
more than
two
computers

Hub

hub is a multiport device
for building star
-
configured topologies with
twisted
-
pair cable



It cannot filter
traffic



It is confined to
small network




maximum nodes
can be 30

To connect
more than
two
computers
in
small
network
which can
filter traffic.

Bridge

Provides repeater functions
along with selective
filtering of traffic to reduce
congestion and contention




Bridges have
limited ports



It introduce latency
for large networks.

For large
network .

Switches

Basically a multiport bridge
that segments a network
into many smaller collision
domains while maintaining
the broadcast
characteristics. Greatly
improves the performance
of LANs



Here network
traffic travels to all
LAN segments
without knowing
the

exact IP
address of the
destination
segment.



It controls collision
domains but not

Switching:


Circuit
-
switching networks

In this technique, first the complete physical connection between two computers is
established and then
data are transmitted from the source computer to the destination
computer



Dedicated paths are used between source and destination.




no queuing



Example: telephone systems.

Message Switching

In this technique, the source computer sends data or the message to

the switching office
first, which stores the data in its buffer. It then looks for a free link to another switching
office and then sends the data to this office. This process is continued until the data are
delivered to the destination computers. Owing t
o its working principle, it is also known
as store and forward. That is, store first (in switching office), forward later, one jump at
a time.




The network receives the entire messages, stores them in a


Secondary storage and transmit them.



It

provides long term storage even after the message has

been delivered.

Example:




Hop
-
by
-
hop
Telex

forwarding and
UUCP

are examples of message switching
systems.

E
-
mail

is another example of a message switching system


Packet Switching

broadcast domains.

For
internetworks
( connecting
more than
one LAN
network with
high speed
and
flexibility)

Router

Routers
make forwarding
decisions based on network
layer addresses.

In addition to controlling
collision domains, routers
control broadcast domains

………………………….

. In
packet switching
no fixed path is created between devices that communicate; it is
broken into packets, each of which may take a separate path from sender to recipient.




The message is divided into a number of slices called



Packets of certain fixed size.



Each packet has its destination address.




Queuing involved



Routing is needed



errors involved



Example:
when you connect to the Internet using a dial
-
up modem.


Network topologies:


In Computer Networking “topology” refers to the layout or design of the connected
devices.


Topology can be classified into two :



1
-
D (bus)



2
-
D (tree, stars, rings, mesh, etc.)


13.8.1


Point to Point Topology

Point to Point topologies are simplest and
most straightforward.
Point
-
to
-
point (PTP)
topology connects two nodes directly together

You can think of as a chain of devices
and another name for this type of connectivity is called
daisy chaining
. Most computers
can 'daisy chain' a series of serial de
vices from one of its serial ports. Networks of
routers

are often configured as point
-
to
-
point topologies.


The following examples are pure point to point links:

Two computers communicating

via modems.

A mainframe terminal communicating

with a front end processor.

A workstation

communicating along a parallel cable to a printer.





Advantage:



It is easy to set up



Installation
Cost is low



Fault identification
is easy



Allows flexibility in communication hardware, packet formats, etc.



Provides security and privacy because communication channel is not
shared


Disadvantages



Number of wires grows as square of number of computers



Connections between buildings can b
e prohibitive



Adding a new computer requires
N
-

1

new connections

13.8.2

Linear Bus

A linear bus topology consists of a main run of cable with a terminator at each end . All
nodes (file server, workstations, and peripherals) are connected to the linear ca
ble.

Access and control of bus networks are typically maintained by a method called

contention
, whereby if a line is unused, a terminal or device can transmit its message at
will, but if two or more terminals initiate messages simultaneously,
they must sto
p and
transmit again at different intervals


Fig. 1. Linear Bus topology

Advantages of a Linear Bus Topology



The advantage of the Bus network is that if one computer fails in the network the
others are still not affected and they continue to work.




Bus network is very simple and easy to set up. If there is an urgent need to set
up a network and perhaps be used on a short term basis then the Bus network is
the best possibility.




Bus networks use the least amount of cable to set up making it cost effe
ctive.

Disadvantages of a Linear Bus Topology



Entire network shuts down if there is a break in the main cable.



Terminators are required at both ends of the backbone cable.



Difficult to identify the problem if the entire network shuts down.



Not meant to
be used as a stand
-
alone solution in a large building.


13.8.
3

Star Topology


A star topology consists of a central connection hub to which devices are connected
with UTP (Unsh
ielded Twisted Pair) Ethernet. Contrary to the bus topology, a star
topology utilizes a point
-
to
-
point connection to connect each node to the central hub.
The hub acts as a signal booster as well, and all the data traffic that transverses the
network passe
s through this hub.

The entire network is dependent upon the central hub in a star topology, so if the entire
network is not working, it means that there is problem in the hub. This makes it easy to
troubleshoot the network because of the only one point fo
r error correction. As all the
computers in star topology are independent to each other and dependent only on the
central hub, network failure or other network problems are less likely to happen. The
privacy of each of the computers is also maintained in t
his topology.

In star topology, new devices and nodes can be easily added and by just extending a
cable from the hub.


Advantages of star topology:



A star topology is simple in functionality and easy to manage.



If a problem occurs in the network, it can be easily isolated and cleared.



It is very easy to expand the star topology because of its simple format.


Disadvantages of star topology:



The entire network of the star topology is completely dependent on the h
ub. If
the hub fails, the whole network fails.



Network connection may slow down when the number of nodes increases or
the cable lengthens.



Star topology needs more cable length than
other topologies
.



It is more expensive compared to
bus topology
.





Star Topology


13.8.
4

Ring Topology



A ring topology consists of network of computers in which each node connects to
exactly two other nodes. This forms a single continuous path for the flow of signals
through each nodes of the network. Data travels from node to node, with each node
along the

way handling every packet. Each of the nodes in the ring topology are
connected to each other through only one pathway, so the failure of only one link
disrupts the whole network.

To overcome this fallacy, the data in a ring topology is transmitted both c
lockwise and
counter clockwise, so that if there is single break of the cable, all the nodes on both sides
can be reached.





Ring Topology




Advantages of Ring Topology



It is an

orderly network in which all the nodes in the network have equal access
to all the resources.



Its performance is far better compared to star topology under heavy network.



It does not need network servers to manage the connections.

Disadvantages of Ring
Topology



If one of the workstations fails to operate, it may lead to the unusability of the
whole network.



Addition and removal of devices in the network can affect the entire network.



Ring network is slower than


the Ethernet network.

13.8.
5

Tree topology



A tree topology consists of bus and star topologies framed in a common network. The
tree like structure of this network allows the colleges, schools, universities
and other
institutions to maintain their own network as a branch of a bigger network through
which they can maximize their area of access to the network. This type of network
topology is most suitable for such networks which are widely spread and divided i
nto
many branches.

On tree topology the hubs of each smaller topologies are connected to the central hub
that controls the entire network. However, some nodes can be directly connected to the
central hub.



Tree topology



Advantages of tree topology



It

is

possible to form a point to point connection with tree topology.



All the computers can access other computers

which are in other larger and
immediate networks.



Tree topology is best suited for branched out networks.

Disadvantages of tree topology



In this topology, the length of the network depends on the type of cable utilized
to form the network.



The entire tree topology would fail if the central trunk fails as it forms the
backbone of the network.



The tree topology is comparatively more complex

than the bus and star
topologies. If it gets bigger, it would be difficult to configure and manage it.



It is expensive as more hubs and cables are required to install the network.

13.8.
6

Mesh Topology


The
mesh

topology incorporates a unique network design in which each computer on
the network connects to every other, creating a point
-
to
-
point connection between every
device on the network. The purpose of the mesh design is to

provide a high level of
redundancy. If one network cable fails, the data always has an alternative path to get to
its destination
An example of a Mesh Network is the Mobile Adhoc Network or
MANet. Mesh topology can also be called as
fully connected netwo
rk

as each node is
connected to other node via cables in the network.





Mesh Topology



Advantages of Mesh topology



As it has multiple routes between the source and the destination, if one route
fails, there would be a number of other routes through which data transfer can
take place.



Traffic problem is minimized in this topology.



Troubleshooting is easier compared to

other networks like
star

and
ring
.



Heavy load of data transfer has little impact on the performa
nce of this
topology.



This network can be easily expanded without affecting the existing users.

Disadvantages of Mesh topology




It is expensive as it requires more cable than other topologies.



Installation is difficult and complicated.

13.8.
7

Hybrid Topology



A hybrid topology, as the name suggests, is an interconnection of two or more
networks. The component networks may be ring, star, tree, mesh or any other,
depending upon the requirement of a firm or institution. For example, in an institution,
if there is a ring topology in one department, bus topology in the next department, star
topology in another department and so on, all the departments can connect to e
ach
other through a bus topology that connects the ring, bus and star topologies of each
department to each other. Such a topology that consists of more than one type of
individual topologies is known as hybrid topology.




Hybrid topology


Advantages o
f hybrid topology



Hybrid topologies are reliable and have increased fault tolerance than other
topologies.



A hybrid topology can efficiently diagnose and isolate faults.



Hybrid topologies are flexible and are designed to suit a variety of network
environments and needs.



A hybrid topology is able to tap into the strengths of other topologies and ignore
their weaknesses. This results in a complex network that is more efficient and
effective than individual topologies



Disadvantages of hybrid topolog
y




Comparatively expensive than other topologies.

Freeware


Software which is distributed free by the author. freeware is proprietary software made
available free of charge.

It

is
the
programming that is offered at no cost and is a common class of
small
applications available for downloading and use in most operating systems
.

Although it is
available for free, the author retains the copyright, which means that it cannot be altered
or sold.


Free software

is distinct from freeware;
Free software may be p
ackaged and distributed for a fee; the
"free" refers to the ability to reuse it, modified or unmodified, as part of another software package. As
part of the ability to modify, users of free software may also have access to and study the
source code
.

The term 'free' does not mean free of charge. It refers to a user's freedom to run, copy,
distribute, study, change and improve the software without the payment of a royalty or
obtaining express permission. Everyone is free to sell copies of free software,

to use it
commercially, and to charge for distribution and modifications. Because anyone who
has a copy may distribute the software at no cost, the software generally is available at
no cost. Free software business models are usually based on adding value

such as
support, training, customization, integration, or certification like open source softwares
are free softwares.


13.13.4

Shareware


Software distributed freely, but with certain conditions applying to it. It is distributed
free on a trial basis wi
th the understanding that the user may need or want to pay for it
later. Either the software is released on a trial basis only, and must be registered after a
certain period of time, or in other cases no support can be offered with the software
without reg
istering it. In some cases direct payment to the author is required. Some
software developers offer a shareware version of their program with a built
-
in
expiration date (after 30 days, the user can no longer get access to the program). Other
shareware (som
etimes called
liteware
) is offered with certain capabilities disabled as an
enticement to buy the complete version of the program.




13.13.5

FLOSS/FOSS

FLOSS is common and
combined term of Free/Libre/Open Source Software.

Actually this term for free software and open source where free means it was cost free software Libre

means liberty : to make changes Open source means code or patch files are available openly to fix bugs,
and for further development.


13.13.6

GNU


GNU

is a computer operating system composed entirely of free software. Its name is a
recursive acronym for
GNU's Not Unix
, which was chosen because its design is Unix
like, but differs from Unix by being free software and by not containing any Unix
code.GNU w
as founded by Richard Stallman and was the original focus of the Free
Software Foundation


GNU Public License (GPL)

Most new open source software around these days uses this license, as does Moodle. In
a nutshell, the GPL says:



Anyone can download, use, modify and distribute this software



All modified versions must ALSO be under the GPL license



All copyright notices must be maintained, and all modifications must be clearly
marked



All distributions must include the full source
code



There is no warranty on the software

13.13.7

FSF


The Free Software Foundation (FSF)was est
ablished in 1985 to promote the
development

of free software with full rights to use, study, copy, modify, and
redistribute computer

programs. particularly t
he GNU operating system, used widely
in its GNU/Linux variant. Its a non profit, non political and international organization
provides standards for developing free softwares.


13.13.8

OSI

Open Source Initiative (OSI)

is a non
-
profit corporation dedicated
to managing and
promoting the Open Source Definition for the good of the community, specifically
through the OSI Certified Open Source Software certification mark and program.

The
basic idea behind open source

is to read, redistribute, and modify the source code
for a piece of software, the software evolves. People improve it, people adapt it, people
fix bugs. We in the open source community have learned that this rapid evolutionary
process produces better soft
ware than the traditional closed model, in which only a
very few programmers can see the source and everybody else must blindly use an
opaque block of bits.

13.13.9

Examples of Open source software

Linux :

Like Windows and Unix ,Linux is also an operating

system developed Linus Torvalds but this operating
system was freely distributed as Open Source i.e code is freely available to read ,edit and fix bugs.


Apart from the fact that it's freely distributed, Linux's

functionality, adaptability and robustness, has
made it the main alternative for proprietary Unix and Microsoft operating systems. IBM, Hewlett
-
Packard atre the top companies which has embraced Linux and support its ongoing development. It was
primarily

adapted as a server platform.


Mozilla

An open
-
source XML/HTML browser have with dynamic image and table resizing, quick insert and
delete of table cells, improved CSS support.

It is a free web browser descended from the Mozilla Application Suite, manage
d by the Mozilla
Corporation. It is the second
-
most popular browser currently worldwide, after Internet Explorer. Firefox
includes tabbed browsing, a spell checker, incremental find, live bookmarking, a download manager, and
an integrated search system tha
t uses the user's desired search engine. Functions can be added through
around 2,000 add
-
ons created by third
-
party developers, the most popular of which include NoScript
(script blocker), Stumble Upon (website discovery), Tab Mix Plus (adds many customiza
ble options to
tabs), FoxyTunes (controls music players), Adblock Plus (ad blocker), DownThemAll! (download
functions) and Web Developer (web tools).



Apache HTTP Server

The Apache HTTP Server is to develop and maintain an open
-
source web server for
modern operating systems including UNIX and Windows NT. The goal of this project is
to provide a secure, efficient and extensible server that provides HTTP services in sync
wit
h the current HTTP standards.Apache has been the most popular web server on the
Internet since April 1996.


Uses of apache are:


Serves both static content and dynamic Web pages on the World Wide Web. Apache
provides environment to run web applications li
ke java based and XML

MYSQL

MySQL is the world's most popular open source database software. It is a structured query language like
SQL used for managing database systems.Many of the world's largest and fastest
-
growing organizations
use MySQL to save t
ime and money powering their high
-
volume Web sites, business
-
critical systems and
packaged software
--

including industry leaders such as Yahoo!, Alcatel
-
Lucent, Google, Nokia.


POSTGRES


PostgreSQL

is an object
-
relational database management system (ORDBM
S). It is released under as a free
software. And like other open
-
source programs, PostgreSQL is not controlled by any single company,
but relies on a global community of developers and companies to develop it.


PANGO



Pango

is a free and open source computing library for rendering internationalized texts in high quality.
Pango has been integrated into most Linux distributions. It most notably provides the rendering for text
in the Mozilla Firefox web browser Different font b
ackends can be used, allowing cross
-
platform support.


PHP
:

Hypertext Pre Processor (PHP) is a server side technology introduced to design
dynamic and interactive web pages.

PHP is the widely
-
used, free, and efficient
alternative to competitors such as Microsoft's ASP. PHP is perfectly suited for Web
development and can be embedded directly into the HTML code. The PHP syntax is
very similar to Perl and C. PHP is often used to
gether with Apache (web server) on
various operating systems.
It is based on open source technology under PHP license to
develop graphic and web applications.


It was written as a set of Common Gateway Interface (CGI) binaries in the C
programming languag
e by the Danish/Greenlandic programmer Rasmus Lerdorf in
1994, to replace a small set of Perl scripts he had been using to maintain his personal
homepage.

PYTHON

Python is a multi
-
paradigm programming language (functional, object oriented and
imperative) w
hich has a fully dynamic type system and uses automatic memory
management; it is thus similar to Perl, Ruby, Scheme, and Tcl.

The language has an open, community
-
based development model managed by the non
-
profit Python Software Foundation.

TOMCAT

Tomcat

is

an application server developed at the Apache Software Foundation (ASF).
To run java applications on web server It has its own internal HTTP server and
implements the Java Servlet and the JavaServer Pages (JSP) specifications from Sun
Microsystems, provi
ding an environment for Java code to run in cooperation with a
web server.

OPENOFFICE

The OpenOffice.org project aims "
To create, as a community, the leading international office
suite that will run on all major platforms and provide access to all functio
nality and data
through open
-
component based APIs and an XML
-
based file format like Microsoft Office
”.

It is free and open source office suit, including

Writer : A word Processor

Calc : Spread sheet software similar to Micrpsofyt Excel





Quick Review:

Definitions:


Network:

A network is an interconnected collection of autonomous
computers

Internet

It is the network of networks that transmit data by
packet
switching

using a standardised
Internet Protocol

(IP) and many
other protocols.


Interspace

Interspace is the networked virtual reality system on the Internet.


Bandwidth
:

The range of transmission frequencies that
can be carried on a
communication line is referred to as the bandwidth of the line

Modem:


device, which converts digital signal into analog, and the
reverse, is known as modem
.

Modulation:


The technique by which a digital signal is converted to
analogform is known as modulation
.

Topology


refers to the layout or design of the connected devices

Protocol

A protocol is a set of rules that governs the communications
between computers on a network.

Telnet

is

a protocol for remote computing on the Internet. It allows a
computer to act as a remote terminal on another machine,
anywhere on the Internet

Wireless

local
loop


Wireless

local loop

(WLL) technology simply means that the
subscriber is connected to the
nearest exchange through a radio
link instead of through these copper wires
.

Short Message
Service

(
SMS)


is the text communication service component of phone, web or
mobile communication systems, using standardized
communications protocols that allow the

exchange of short text
messages between fixed line or mobile phone devices

Voice Mail :


The electronic transmission of voice messages over the Internet. The
messages are stored on a computer until the recipient accesses and
listens to them

Email,

also

sometimes written as e
-
mail, is simply the shortened form of
electronic mail, a protocol for receiving, sending, and storing
electronic messages

chatting:



On line talk in the form of text is known is chatting.


video
conferencing:

A
videoconferencing

or
video conference

(also known as a
videoteleconference
) is a set of interactive
telecommunication

technologies

which allow two or more locations to interact via two
-
way video and audio
transmissions simultaneously


Viruses

:



Computer programs written by devious programmers and
desi
gned to replicate themselves and infect computers when
triggered by a specific event.

Cookies


are small bits of information that get stored on your hard drive
(persistent cookies) or in memory (non
-
persistent cookies) of
your computer. They are placed o
n your computer by the
websites you are visiting.

Firewall

stands between the company’s network and a public network,
effectively shielding your computers from malicious hacker activity,
and controlling the flow of data

Cyber Law

is the law governing cyber space.It is a very wide term and includes
computers, networks, software, data storage devices (such as hard
disks, USB disks etc), the Internet, websites, emails and even
electronic devices such as cell phones, ATM machines et
c.

World Wide Web


It is a repository of information containing a set of programs ,
standards and protocols that allows the multimedia and hypertext files
to be created , displayed and linked on the internet.

W3C

The organization responsible for managing

standards for the WWW.


Browser

A browser is an application which provides a window to the
Web. For example : Internet explorer ,Mozilla Firefox.

Web Page


A document formatted for distribution over the web. Most often a web
document is formatted in a m
arkup language like HTML or XML.

Web Document


A document formatted for distribution over the web. Most often a web
document is formatted in a markup language like HTML or XML.

Website


A collection of related web pages belonging to a company or an
individual.

URL (Uniform
Resource Locator)


A URL refers to an address in the special format on the internet.

It is a standard way to address web documents (pages) on the Internet
(like:
http://www.microsoft.com/
)
. URL are of two types: absolute
URL ,relative URL


Web Host



A web server that "hosts" web services like providing web site space to
companies or individuals.

Web Hosting


The action of providing web host services.

Domain name

A domain name is a unique name for a web site, like
ntchosting.com

.Domain names must be registered

An
Internet
Protocol address

(
IP address
)


is a numerical label that is assigned to any device participating
in a computer network that uses the Internet
Protocol for
communication between its nodes




I
n 1969 by the development of first network called ARPANET , led to the development of
internet .



ARPANET ( Advanced Research Projects Agency NETwork) was the project for
connecting computers at different
Universities and U.S. defense.



network architecture: peer to peer network ,client server networking.



peer to peer networks :
All computers are of equal importance. Software and data are
stored on each computer.



client/server network:
Software and data are

held on a file server and may be used by
other computers on the network. Security is controlled centrally.



Local
-
Area Networks (LANs)

The computers are geographically close together (that is, in the same building).



Wide
-
Area Networks (WANs)

The computers
are farther apart and are connected by telephone lines or radio waves.



MAN
-

Metropolitan Area Network

: It covers large span of physical area than LAN
but smaller than WAN, such as a city.



Personal area network (PAN) is a computer network designed for
communication
between computer devices(including telephones and personal digital assistants close to
one person)



The Internet, or simply the Net, is the information superhighway.



The end devices that wish to communicate with each other are called
station
s
.



The switching devices are called
nodes



there are three types of switching:
Circuit Switching ,Packet Switching and Message
Switching



In
circuit switching
, a circuit is first established and then used to carry all data between
devices. example:
telephone system



In
packet switching
no fixed path is created between devices that communicate; it is
broken into packets, each of which may take a separate path from sender to recipient.
example : connecting internet using dial up modem.



message switching
: In this technique, the source computer sends data or the message to
the switching office first, which stores the data in its buffer.example : email



Frequency is measured in hertz(Hz).



1 MHz = 1million Hz



Baud: It describes the rate of change of the si
gnal on the line i.e.how many times (per
second) the signal changes its pattern.



Data Transfer rate :
A data transfer rate is the amount of digital data that is moved
from one place to another in a given time usually in seconds. In general, the greater th
e
bandwidth of a given path ,higher the transfer rate.



Bit rate :
A data transfer rate expressed in bits per second .



Kbps= 1000 bits per second



Mbps=1000 kbps=1,000,000bps



Gbps=1000 mbps



Tbps=1000gbps



Twisted pair cable : two type shielded and
unshielded Twisted Pair(UTP)

o

Advantages: Reasonable cost ,High Speed ,Easy to add additional network
devices ,Supports large number of network devices, Easy to install, because of
physical flexibility, low weight & easy connectivity.

o

Disadvantages of twisted pair: Signals loose energy due to attenuation, so
repeaters are required, Bandwidth is low, High attenuation (signal loss) limits
individual runs to 100 meters



Cat
-
5Short for
Cat
egory 5
,
network

cabling that consists of four twisted pairs of copper
wire terminated by
RJ45

connectors. Cat
-
5 cabling supports frequencies up to 100
MHz

and speeds up to 1000
Mbps
. It can be used for
ATM
,
token ring
,
1000Base
-
T
,
100Base
-
T
, and
10Base
-
T

networking. Computers hooked up to
LAN

s are connected using Cat
-
5
cables, so if you're on a LAN, most likely the cable running out of the back of your PC is
Category 5.



Coaxial c
able : Coaxial cable, in its simplest form, is a single wire wrapped in a foam
insulation,surrounded by a braided metal shield, then covered in a plastic jacket

o

advantages:

greater bandwidth ,greater channel capacity and low error rates.

o

disadvantage:

Prob
lems with the deployment architecture, Bidirectional
upgrade required, Great noise, High installation costs, Susceptible to
damage from lightning strikes.



Infrared ,radiowave ,microwave and satellite are wireless technology for
communication.



NIC known as

network interface card :

network device required to access the
network .



Hub:

a network device to connect more than two computer on network .it is
preferred for small network where number of nodes are less than 30.



Switch: Basically a multiport bridge
that segments a network into many smaller
collision domains while maintaining the broadcast characteristics. Greatly
improves the performance of LANs



A Router is responsible for connecting two physical and logically different
networks.



A repeater connects
two segments of your network cable.



A bridge is a product that connects a local area network (LAN) to another local
area network that uses the same protocol (for example, Ethernet or Token Ring).



Topology can be classified into two :

o

1
-
D (bus)

o

2
-
D
(tree, stars, rings, mesh, etc.)



Protocol can be classified into two groups : network and communication
protocol.



Network protocol : Ethernet ,FDDI,ATM, Local talk ,token ring.



Communication protocols : HTTP,FTP,TCP/IP,SMTP,SLIP,PPP,POP3



SMTP and POP3 are
email protocols.



Wireless and mobile communication technology:

o

FDMA

o

GSM

o

TDMA

o

CDMA

o

3G

o

4G



EDGE and Wimax are 3G technologies .



CDMA(Code Division Multiple Access) :

It is a digital cellular technology which uses spread spectrum techniques means the data is sent in
small pieces over a number of discrete frequencies available for use in the specified range .All the
users will transmit in the same wide spectrum. Each use
r‘s signal is spread over the entire bandwidth
by a unique spreading code . At the receiver’s end same unique code is used to recover the signal.



CDMA has been used in many military applications, such as:



Anti
-
jamming (because of the spread signal,

it is difficult to jam or interfere with a CDMA signal).



Ranging (measuring the distance of the transmission to know when it will be received).



Secure communications (the spread spectrum signal is very hard to detect).




Time Division Multiplexing
:TDMA

works by dividing a radio frequency into time slots and
then allocating slots to multiple calls . In this way ,a single frequency an support multiple,
simultaneous data channels



Frequency Division Multiple Access (
FDMA): allocates users with different car
rier frequencies
of the radio spectrum.The radio spectrum is available to the users where communications
signals are pass through that spectrum. Multiple access enables allows more than one
communications signal to pass within a particular band



Enhanced

Data rates for GSM Evolution

(
EDGE
) or
Enhanced GPRS
(
EGPRS
),



It is an Advanced technology over GSM which is widely used in digital mobile phone technology
which allows increased data transmission rate .This technology was developed in North America
and us
ed extensively in packet switched applications such as Internet Connection, VDO services
,multimedia services .




Protocols for chat and video conferencing : VoIP.



Voice over Internet Protocol (VoIP), is a technology that allows you to make voice calls usin
g a
broadband Internet connection instead of a regular (or analog) phone line.



Network security : protection from threats to network.



Threats to network security are viruses ,worms ,Trojan horse



In a computer, a worm is a self
-
replicating
virus

that does not alter files but
resides in active memory and duplicates itself. Worms use parts of an
operating
system

that are automatic and usually invisible to the user.



In 1981
-

First virus Elk Cloner was transmitted by floppy disk.



Spam is flooding the Int
ernet with many copies of the same message, in an
attempt to force the message on people who would not otherwise choose to
receive it.



There are various ways to protect from network threats some are :

o

Authentication Definition

o

Authorization Definition

o

Iden
tity Management

o

Firewall

o

Identification methods

o

Antiviruses



The
Information Technology Act 2000

(
ITA
-
2000
)(IT ACT) is an Act of the
Indian Parliament

for
cyber related issues.



hackers are intelligent people who breaks into a system for gaining knowledge
,
freely share what they have discovered, and never, ever intentionally damage data.



crackers are “ evil hackers “
who breaks into or otherwise violates

the system integrity of
remote machines, with malicious intent.



HTML :Hypertext markup language for designing web sites.



XML(

EXtensible Markup Language)

is a standard, simple, self
-
describing way of
encoding both text and data so that content can be pro
cessed with relatively
little human intervention and exchanged across diverse hardware, operating
systems, and applications



server side scripting languages:
The

code which is executed at server end is
called server side script and computer languages used to write this script are
called
server side scripting languages

Examples of server side scripting
languages are CGI, ASP and PHP,JSP



Client side scripting:
The r
esponse or output of web server is send to requesting
client. This response consists of HTML and some other script. The HTML is
rendered by browser. Browser also executes the script received from server. This
script or small program embedded in HTML is cal
led client side script and
languages used to write this script are client side scripting languages .Forex:
JavaScript and VB Script.



The term ‘Web 2.0’ refers to the idea of the
“New Internet”
, or the second wave of the World
Wide Web. Web 2.0 is not a spe
cific application or technology, but explains two paradigm shifts
within Information Technology, ‘user
-
generated content’ and ‘thin client computing’.



Major difference between bridge ,router and gateway is bridges are used to connect same
network and hav
ing same network protocols while router is used to connect same LAN network
with different set of protocols while gateway is used to connect different networks.



To connect very high range of network use satellite communication where range of signals i
s
very high.



Thick Coaxial cables support up to 500ms for greater than that range use optical fibers for better
.data transmission.



Switch manages the data required for larger network approximately 50 and above .




High level connectivity could be provi
ded by radio transmission using satellite channels .



Wireless networking known as WLL speed comes in 54mbps,108mbps.



HTML is used for designing web pages has predefined tags to be used while in XML you can
define your own tags.



A newsgroup is online commu
nity bulletin board where users can post messages , respond to
posted messages or just read them.



ARCHIE

is a software tool that help you search for the files stored on FTP server.



Cyber law means a

wide variety of political and legal issues related to the Internet and other
communications technology, including intellectual property, privacy, freedom of expression, and
jurisdiction.



Important Definitions :

1.

DHTML
--

(Dynamic Hypertext Markup Language)

:
DHTML refers to web pages that use a
combination of HTML, JavaScript, and CSS to create features such as letting the user drag items
around on the web page, some simple kinds of animation, and many more.

2.

Extranet

:
An intranet that is accessible to
computers that are not physically part of a company’s'
own private network, but that is not accessible to the general public, for example to allow
vendors and business partners to access a company web site. Often an intranet will make use of
a Virtual Priv
ate Network. (VPN.)

3.

Fire Wall

:
A combination of hardware and software that separates a Network into two or more
parts for security purposes.

4.

FTP

--

(File Transfer Protocol) :
A very common method of moving files

between two Internet sites. FTP is a way to

login to another Internet site for the purposes of retrieving
and/or sending files. There are many Internet sites that have established publicly accessible
repositories of material that can be obtained using FTP, by logging in using the account name
"anon
ymous", thus these sites are called "anonymous ftp servers".

5.

Gateway

:
The technical meaning is a hardware or software set
-
up that

translates between two dissimilar protocols, for example America Online has a gateway that
translates between its internal, p
roprietary e
-
mail format and Internet e
-
mail format. Another,
sloppier meaning of gateway is to describe any mechanism for providing access to another system,
e.g. AOL might be called a gateway to the Internet.

6.

Email
--

(Electronic Mail) :
Messages, usual
ly text, sent from one person to

another via computer. E
-
mail can also be sent automatically to a large number of addresses.

7.

GIF

--

(Graphic Interchange Format) :
A common format for image files,

especially suitable for images containing large areas of the

same color. GIF

format files of simple images are often smaller than the same file would be if stored in JPEG format,
but GIF format does not store photographic images as well as JPEG.

8.

Gopher

:
Invented at the University of Minnesota in 1993 just before t
he Web, gopher was a
widely successful method of making menus of material available over the Internet. Gopher was
designed to be much easier to use than FTP, while still using a text
-
only interface.

9.

Hypertext

:
Generally, any text that contains links to ot
her documents


words or phrases in the
document that can be chosen by a reader and which cause another document to be retrieved and
displayed.

10.

Internet (Upper case I)

:
The vast collection of inter
-
connected networks that are connected using
the TCP/IP pr
otocols and that evolved from the ARPANET of the late 60's and early 70's. The
Internet connects tens of thousands of independent networks into a vast global internet and is
probably the largest Wide Area Network in the world.

11.

Intranet

:
A private network
inside a company or organization that uses the same kinds of
software that you would find on the public Internet, but that is only for internal use. Compare
with extranet.

12.

IP Number

--

(Internet Protocol Number) :
Sometimes called a dotted quad.

A unique nu
mber consisting of 4 parts separated by dots, e.g. 165.113.245.2. Every machine that is on
the Internet has a unique IP number
-

if a machine does not have an IP number, it is not really on the
Internet. Many machines (especially servers) also have one or
more Domain Names that are easier for
people to remember.

13.

ISDN
--

(Integrated Services Digital Network) :
Basically a way to move more

data over existing regular phone lines. ISDN is available to

much of the USA and in most markets it is
priced very comparably to standard analog phone circuits. It can provide speeds of roughly 128,000
bits
-
per
-
second over regular phone lines. In practice, most people will be limited to 56,000or 64,000
bits
-
per sec
ond. Unlike DSL, ISDN can be used to connect to many different locations, one at a time,
just like a regular telephone call, as long the other location also has ISDN.

14.

ISP
--

(Internet Service Provider)

:
An institution that provides access to the Internet
in some
form, usually for money.

15.

JPEG
--

(Joint Photographic Experts Group)

:
JPEG is most commonly

mentioned as a format for image files. JPEG format is preferred to the GIF format for photographic
images as opposed to line art or simple logo art.

16.

Leased
Line

:
Refers to line such as a telephone line or fiber
-
optic cable that is rented for
exclusive 24
-
hour, 7
-
days
-
a
-
week use from your location to another location. The highest speed
data connections require a leased line.

17.

Modem
--

(Modulator, Demodulator)

:
A device that connects a computer to a phone line. A
telephone for a computer. A modem allows a computer to talk to other computers through the
phone system by converting digital signals to analog and vice versa. Basically, modems do for
computers , what

a telephone does for humans.

Modem are of two types:

Internal modem : are the modem that are fixed within the system.

External modem : are the modems that are connected externally to a computer as other peripheral
devices are connected.

18.

Mosaic

:
The first

WWW browser that was available for the Macintosh,

Windows, and UNIX all with the same interface. Mosaic really started the

popularity of the Web. The source
-
code to Mosaic was licensed by several

companies and used to create many other web browsers.

19.

PDF
-
-

(Portable Document Format
) :
A file format designed to enable

printing and viewing of documents with all their formatting (typefaces, images, layout, etc.)
appearing the same regardless of what operating system is used, so a PDF document should look the
same on Windows, Macintosh, Linux, OS/ 2, etc. The PDF format is based on the widely used
Postscript document description language. Both PDF and Postscript were developed by the Adobe
Corporation.

20.

OSS

: Open source software.

21.

OSI:

Open Source Initiative (
OSI)

is a non
-
profit corporation dedicated to managing and
promoting the Open Source Definition.

22.

Berkeley Source Distribution (BSD
):one of the license for open source software

23.

Apache


open source web server software .

24.

Mozilla

is open source web browser.

25.

L
inux
is an open source operating system.

26.

PHP
is an open source web scripting language

27.

Tomcat
is the web server supports java applications to run.

28.

Python
is an open source programming language like Perl etc.

29.

MySQL

is an open source database language.



FAMILY

OF PROTOCOLS


30.

SMTP
-

Simple Mail Transfer Protocol :
The SMTP protocol is used for

the transmission of e
-
mails.

31.

MIME
-

Multi
-
purpose Internet Mail Extensions :
The MIME protocol

lets SMTP transmit multimedia files including voice, audio, and binary data a
cross TCP/IP networks.

32.

IMAP
-

Internet Message Access Protocol :
The IMAP protocol is used for

storing and retrieving e
-
mails.

33.

POP
-

Post Office Protocol :
The POP protocol is used for downloading emails from an e
-
mail
server to a personal computer.

34.

FTP
-

File Transfer Protocol :
The FTP protocol takes care of the transmission of files between
computers.

35.

NTP
-

Network Time Protocol :
The NTP protocol is used for synchronizing the time (the clock)
between computers.

36.

SNMP
-

Simple Network Management Protocol
: The SNMP protocol is

used for the administration of computer networks.

37.

ICMP
-

Internet Control Message Protocol :
The ICMP protocol takes care of error handling in
the network.

38.

ARP
-

Address Resolution Protocol :
The ARP protocol is used by IP to find th
e hardware
address of a computer network card based on the IP address.

39.

RARP
-

Reverse Address Resolution Protocol :
The RARP protocol is used by IP to find the IP
address based on the hardware address of a computer network card.

40.

PPTP
-

Point to Point Tunne
ling Protocol :
The PPTP protocol is used for

setting up a connection (tunnel) between private networks.

41.

SMTP
-

Simple Mail Transfer Protocol :
The SMTP protocol is used for

the

transmission of e
-
mails. SMTP takes care of sending your email to another computer. Normally
your email is sent to an email server (SMTP server), and then to another server or servers, and finally
to its destination. SMTP can only transmit pure text.

42.

POP
-

Post Office Protocol :
The POP protocol is used by email programs

(like Microsoft Outlook) to retrieve emails from an email server. If your email program uses POP, all
your emails are downloaded to your email program (also called email client), each time

it connects to
your email server.

43.

IMAP
-

Internet Message Access Protocol “
The IMAP protocol is used by email programs (like
Microsoft Outlook) just like the POP protocol. The main difference between the IMAP protocol
and the POP protocol is that the IMA
P protocol will not automatically download all your emails
each time your email program connects to your email server.







Short Questions


1.

What is networking?

Ans


Networking is the term used to describe connectivity between the systems with
or without Cables or satellites.


2.

What is website?

Ans

It is the collection of web pages used to link text or images with each other. Ex
www.yahoo.com


3.

Define the term topology.

Ans It is the framework or arrangement of systems on network ex: ring ,star, bus etc


4.

What are the two types of topology
.

Ans


Star Topology



Bus Topology


5.

What is LAN?

Ans LAN

stands for Local Area Network. It is the connectivity of systems within


the local organization covers around 100 ms area


6.

What do you understand by protocol.

Ans

A set of rules or instructions govern communication on computer network are
called prot
ocols.


7.

EDGE stands for…

…………

Ans Enhanced Data rates for GSM Evolution


8.

Which protocol is used for sending and receiving emails respectively?

Ans SMTP used for sending emails and POP for receiving emails.


9.

How TCP/IP works.

Ans

T
CP/IP(Transmission
Control Protocol /Internet Protocol)

A collection of Internet communication protocols between two computers. The
TCP protocol is responsible for an error free connection between two computers,
while the IP protocol is responsible for the data packets sent
over the network.

TCP splits message into fixed size datagram which are then tagged with
destination address and sent to receiver where the datagram are merged to form
proper message.

IP is the protocol controlling addressing on the network . As and when
any
computer gets connected to the network, it must owe a unique address with
which it will be identified by other systems. IP protocol assigns address to the
different system on the network.


10.

FDDI is an example of ________

Ans t
oken ring network


11.


Token r
ing is based on ___________

Ans
ethernet



12.

MODEM is used for _____________

and _________________

Ans

modulation


demodulation


13.

What is the significance of HTTP and FTP .

Ans

HTTP (Hyper Text Markup Protocol ) :

This protocol is responsible for accessing

hypertext documents on world wide web. Set of rules governing exchange of
hypertext between two computers is commonly known as HTTP. It consists of 2
distinct items
-



a set of requests from browsers to servers



a set of responses from server to browsers


FT
P (File transfer protocol ) :
It defines a method for transferring large files
from one computer to another over a network. Set of rules, which enables files
to be uploaded or downloaded on a network is known as FTP. It is very effective
way to get a g
eographically dispersed group to co
-
ordinate on a project and
share information on the internet. It serves as client server process.

Downloading
: refers to transfer of files from FTP server to your computer.

Uploading

:

refers to transfer of files from your computer to FTP servers. Only
authorized users can upload a file .Most common use of FTP is to download and
upload a file


14.


What is XML?.

Ans

XML (eXtensible Markup Language)

:

It is a meta language for describing t
he markup languages A simplified version
of SGML especially designed for web documents, developed by the W3C.. There
is no predefined tag set. It will be defined by either the application that process
them or by style sheets.


15.


What do you understand by th
e term e
-
commerce.

Ans

Ecommerce stands for electronic commerce i.e buying and selling of products or
services over electronic systems such as the Internet and other computer
networks.


16.

Explain the types of networks.

Ans

Types of networks:
-



LAN
-
Local area
network



Privately owned networks



Used to connect PC’s and workstation within a building or computers in
an area upto
100mts

of range.



Speed of data transmission is not very high



MAN
-
Metropolitan Area Network




Bigger version of LAN




May be private or publi
c




Covers a group of nearby offices or city



WAN
-
Wide area network




Spans a large geographical area like countries




Public Network




Speed very high


17.

What is search engine .Name any four search engines.

Ans

A
search engine

is program or an information retrieval system designed to help
find information stored on a computer system. Search engines help to minimize
the time required to find information and the amount of information on any
topic .

Ex: www. google.com,
www.yahoo.com
,
www.khoj.com
, www.altavista.com


18.

What is web browser .Name any two commonly used web browsers..

Ans

A web browser is a program which is used to visit web pages . The two most
well

known are Netscape Navigator and Microsoft Internet Explorer which are
used by vast majority .Some other browsers are MOSAIC , LYNX , OPERA etc.


19.

What is the syntax of URL?.

Ans

A Uniform Resource Locator refers to an address in the special format on the

internet .It is a standard way to address web documents (pages) on the Internet
(like: http://www.microsoft.com/)


20.

What is bandwidth and baud rate.

Ans

The range of transmission frequencies that can be carried on a communication
line is referred to as the

bandwidth of the line .In digital systems bandwidth is
data speed in bits per second (bps).


Baud rate:


It describes the rate of change of the signal on the line i.e.how many times (per
second) the signal changes its pattern. The baud rate is the measure

of the
modulation rate ,the number of discrete signaling events per second. In low
speed modem the baud is same as bit rate.


21.

Explain the following terms:

a.

Email




b. Chatting


c. Videoconferencing


d. Domain Name System

e. GSM




f. Telnet

g. Veronica



h. Usenet

i. WAIS




j. Mosaic

Ans

a.

Email

: Electronic mail is the way of sending and receiving messages
electronically.


Major advantage is easy record maintenance, Low
cost and fast delivery.


b.

Chatting:

On line talk in the form of

text is known is chatting. In chatting as
you type a message on the screen which is immediately received by the
recipient then the recipient can type a message in response to your message
which is received by you instantly.

Sites which provide this
facility are http:/ chat .yahoo.com , chat.123india.com
, chat.sify.com


c.

Videoconferencing:

is a set of interactive telecommunication technology
which allow two or more locations to interact via two
-
way video and audio
transmissions simultaneously.


d.

Domai
n Name System

: A domain name is a unique name for a web site, like
yahoo.com .Domain names must be registered. When domain names are
registered they are added to a large domain name register, and information
about your site
-

including your internet IP ad
dress
-

is stored on a DNS server.


e.

DNS

stands for Domain Name System. A DNS server is responsible for
informing all other computers on the Internet about your domain name and
your site address





f.

GSM(Global system for Mobile):

It is one of the leading digital cellular system for mobile communication .The
digital nature of GSM allows data, both synchronous and synchronous data, to
be transported as a bearer service to or from an ISDN terminal. The data rates
supported by GSM are
300 bps, 600 bps, 1200 bps, 2400 bps, and 9600 bps.

The most basic teleservice supported by GSM is telephony. A unique feature of
GSM compared to older analog systems is the Short Message Service (SMS).
Supplementary services are provided on top of telese
rvices or bearer services,
and include features such as international roaming, caller identification, call
forwarding, call waiting, multi
party conversations, and barring of outgoing
(international) calls, among others.


g.

Telnet

: It is an internet facilit
y that supports remote login.

This facility allows users to access files and execute programs on a remote
computer without being physically present at the actual site of working.


h.

Veronica
:

‘Veronica’ actually stands for “Very Easy Rodent
-
Oriented
Netwide
Index to Computerized Archives.” It’s a program that allows you to
search the files of the internet’s Gopher servers using keywords. It i
s a search
engine system for the Gopher protocol.

After entering a particular keyword for
searching, Veronica displays
a list of gopher menus and articles containing the
keyword you searched for. The more recent versions of Veronica can also
search certain Web pages, newsgroups, and FTP sites.


i.

Usenet


:

It is the public bulletin board of the internet and used as a
means to share news and other information among users . It is many to many
conversation.


j.

WAIS


: Wide area information Network ) : is the facility on the
internet that can search for a given i
tem in the database which may be on the
different sites on the internet . Searching can be possible by specifying the
search string or a topic.


k.

MOSAIC

: It is a graphical WWW browser created by (NCSA) National center
for super Computing applications. It c
an display hyper text documents that
include digital video , audio , graphic images and text in a variety of formats.


22.

Expand the following terms:

a.

TCP/IP

b. HTTP

c. FTP


d. URL

e.

DNS


f. IP address

g. SMTP

h. POP

i.

IMAP


j. SLIP

k.WLL

l.CDMA

m.

TDMA

n. FDMA

o. XML

p.WDM

q.

NFS


r. CSMA/CD s. NNTP

t. GSM

u.

PSTN


v. ISDN

w. W3C

x. WLL

y. MODEM



Ans


a)

TCP/IP


: Transmission Control Protocol/Internet Protocol

b)

HTTP



: Hyper Text Transfer Protocol

c)

FTP



: File Transfer Protocol

d)

URL



: Uniform Resource Locator

e)

DNS



: Domain Name System

f)

IP address

: Internet Protocol address.

g)

SMTP



: Simple Mail Transfer Protocol.

h)

POP


: Post Office Protocol.

i)

IMAP


:

Internet Message Access Protocol.

j)

SLIP


:

Serial Line Internet Protocol

(
SLIP
)

k)

WLL


:

Wireless Local Loop

l)

CDMA


:

C
ode division multiple access

(
CDMA)

m)

TDMA


:

Time division multiple access

(
TDMA
)

n)

FDMA


:

FDMA

(
frequency division multiple access
)

o)

XML :

Extensible Markup Language (
XML
)

p)

WDM :

wavelength
-
division multiplexing

(
WDM)

q)

NFS


:

Network File System

(
NFS
)

r)

CSMA/CD

:

Carrier Sense Multiple Access / Collision




Detection

s)

NNTP


:

Network News Transfer Protocol

t)

GSM


:
Global system for Mobile.

u)

PSTN


: Public Switched Telephone Network

v)

ISDN


:
Integrated Services Digital Network

w)

W3C


: World wide web Consortium

x)

WLL


: Wireless in Local Loop

y)

MODEM


: Modulation Demodulation


23.

What is web hosting?

Ans

Web hosting means storing your web site on a public server. It normally includes
email services and often

includes domain name registration.

24.

What is WAN?

Ans

WAN
-
Wide area network




Spans a large geographical area covering countries




Public Network




Speed very high


25.

What is the significant of ARPANET in the network?


Ans

ARPANET ( Advance Research Projects A
gency NETwork) was the project for
connecting computers at different Universities and U.S. defense . Soon the
engineers ,scientists ,students and researchers who were part of this system
began exchanging information and messages on it .ARPANET started with

a
handful of computers but it expanded rapidly.


26.

What do you understand by peer to peer network

Ans

It is also known as non dedicated server . where

in small networks work station
that can be doubled up as a server is known as non
-
dedicated server , since it is
not completely dedicated to the cause of serving. It is a slower and requires more
memory. The small networks using such servers are known as

peer to peer
network.


27.

What is client server model
.


Ans


It is a network in which a workstation (client ) can request information from a
computer that can share resources (server) and fulfills request. The client/server
model provides a convenient way t
o interconnect programs that are distributed
efficiently across different locations. Computer transactions using the
client/server model are very common.

Advantage : Distribution of work between the client and the server . Server is available to many
clien
ts.


28.

Give the usage of the following network devices.

a.

Hub

b.

Repeater

c.

Switch

d.

Bridge

e.

Router

f.

Gateway

Ans

a.

Hub

:

It is a hardware device used to connect several computers together. Hubs act as junction boxes
,permitting new computers to be connected to the network as easily as plugging a power cord into an
electrical socket, and provide an easy way to connect networ
k cables .It also act as a repeater or
amplifier .Hubs are sometimes also called concentrators, multistation access units or transceivers.


b.

Repeater
: It is a simple device that amplifies all incoming signals on a
communication channel and transmits them
back the regenerated signal. It connects
two segments of your network cable. It retimes and regenerates the signals to proper
amplitudes and sends them to the other segments.


c.

Switches :

A switch is a device that is used to divide network into different

subnetworks called LAN segments.It typically provides 10/100Mbps network access speed for each
device connected to it. This is different to a hub which typically operates at 10/100 Mbps but this is
the maximum throughput for all devices attached to it. Hub
s cannot cope with the increased
demands of today’s high bandwidth applications, e.g. video conferencing and therefore should be
phased out in favour of switches.


d.

Bridge
: It is a device that links two networks together which are physically

separate but
logically same i.e.the networks that follow the same protocols but
different type of cables.

e.

Router
:It is a device that works likes a bridge but can handle different types of
protocols . It is also used to balance the traffic on various parts of the net
work. It
uses logical address whereas the bridge uses physical address .


f.

Gateway

: It is a system that joins two dissimilar networks together. A network
gateway can be implemented completely in software, completely in hardware, or as
a combination of t
he two. It expands the functionality by performing data
translation and protocol conversion before transmission. It provides flexibility in
communication.


29.

Explain the following topologies diagrammatically for five workgropus connected
with the server:

a.

St
ar topology

b.

Ring topology

c.

Bus topology

d.

Tree topology.

Give two advantages and disadvantages for all of the above topologies.


Ans

a: Star Topology
-

Most common type of topology used in homes and offices and well
suited for smaller networks.

In a star topology, various nodes are connected to a
central connection point called hub which can be computer hub or sometimes switch
alone.

The drop cables are extended in all directions and each device is connected to the hub
via these cables. . It
is inherently fault tolerant .


Advantages



If a node goes down, network keeps on working without interruption, only
one computer might get affected and not the entire network.



Network management is easy because of its simplicity in functionality



Fault det
ection is easy , the problems can be easily located logically in a Star
Topology

Disadvantages
-



The Star Topology is fully dependant on the hub and the entire working of
the network depends on the hub or the switch. More cabling is required



If there are ma
ny nodes and the cable is long then the network may slow
down



The Star Network Topology typically needs more cable to be networked than
the usual Bus topology

Example : Archnet , Ordinary telephone conversation


b. Ring Topology
-

Also known as daisy chain
topology, is large circular cable



and each node is connected to two of its adjacent nodes, thus forming a ring


Advantages



One node can transmit at a time and collisions do not occur



Need for repeaters is reduced

Disadvantages



Each node

must handle data transmitted by other nodes.



If one node fails whole network goes down.

Example : Mitrenet



c.

Bus Topology( Multi
-
drop topology)
-

It is a method of transmission on networks
that uses a common vehicle (backbone cable) for transmissions and thus it is
categorized as shared
communication.

Bus topology only one device is allowed to
transmit at a given point of time. A bus structure use
s a main trunk

called backbone. The two ends of the backbone are terminated by absorbers, which
absorb the signals passed by all the devices. On the backbone that is a twisted pair
co
-
axial cable, peripherals and PCs connected with the help of short ca
bles called
drop cables.


Advantages



Wide range of equipments are attached to such networks.



A new node can be attached to network without disrupting the network



Low cabling cost, very easy to set up , Use least amount o cable

Disadvantages



One message
can travel at a time



When a message from two nodes comes, a collision can occur. If the data
transfer

rate is high then the Bus network does not perform very well because
the data travels in a stream and cannot be overloaded



Reliability is low because a si
ngle break in backbone can bring the whole
network down



Fault detection & isolation is difficult

Example : Ethernet


d.
Tree Topology
:

The shape of network is an inverted tree with central root branching and then
sub
-
branching till extremes of network. . I
t is a modification of pure topologies (
combination of star and bus topology ) so is also called hybrid topology. It is best
suited where when the network is widely spread and vastly
divided

into many
branches & hierarchical flow of data is required.


Advantages



Data communication is very fast as there is a direct link between
nodes.



A point to point connection is possible with Tree Networks



Best topology for branched out networks

Disadvantages



Cabling and setup is quite complex.For big networks it is d
ifficult to
configure and get complicated .



The Tree Topology network is entirely dependant on the trunk which
is the main backbone of the network. If that has to fail then the entire
network would fail.

30.

What is multiplexing.

Ans

A term used to refer to a

process where multiple analog message signals or
digital data streams are combined into one signal. Ex. Time division mutiplexing,
Frequency Division

Multiplexing .


31.

Explain FDM and TDM
.

Ans

FDM(Frequency Division Multiplexing):

where multiple baseband

signals are
modulated on different frequency carrier waves and added together to create a
composite signal.

In analog transmission, signals are commonly multiplexed using frequency
-
division multiplexing (FDM), in which the carrier bandwidth is divided int
o
subchannels of different frequency widths, each carrying a signal at the same
time in parallel.


TDM (Time division Multiplexing
):
a type of multiplexing that combines data
streams by assigning each stream a different time slot in a set

.It works by
dividing a radio frequency into time slots and then allocating slots to multiple
calls . In this way ,a single frequency an support multiple, simultaneous data
channels.

TDM repeatedly transmits a fixed sequence of time slots over a single
t
ransmission channel. Within T
-
Carrier systems, such as T
-
1 and T
-
3, TDM
combines Pulse Code Modulated (PCM) streams created for each conversation or
data stream.

32.

How CDMA is different from all other channel allocation techniques
.

A

It is a digital cellula
r technology which uses spread spectrum techniques means
the data is sent in small pieces over a number of discrete frequencies available for
use in the specified range.


33.

What do understand by 3G system.

Ans

3G is short for third
-
generation mobile telepho
ne technology. The services
associated with 3G provide the ability to transfer both voice data (a telephone
call) and non
-
voice data (such as downloading information, exchanging email,
and instant messaging.


34.

What provisions will you take to make your net
work secure.

A

Providing Firewall and antivirus solutions.


35.

What is the importance of cookies.

Ans

A cookie is a small file that web server can store on your machine . It is the
temporary file that stores information at the client side by the server and

thus
reduce the overhead of the server.


36.

How firewall acts as security solution.

Ans

It is a combination of specialized hardware and software set up to monitor traffic
between an internal network and an external network (ie the Internet). Its
primary pur
pose if for security and is designed to keep unauthorized outsiders
from tampering with or accessing information on a networked computer system.


37.

Write any two components of openoffice.

Ans

OpenOffice has these components: writer ,calc and draw.



38.

How will you explain the concept of WLL.

Ans


WLL is a system that connects subscribers to the public switched telephone network (PSTN) using radio
signals as a substitute for copper for all or part of the connection between the subscriber and the switch.
This includes cordless access systems, proprie
tary fixed radio access, and fixed cellular systems.


39.

What are the following software use for ?

a.

PHP


b.

Linux

Ans

PHP
: Short of Hypertext Preprocessor. It a server side side technology
introduced to design dynamic web pages like ASP,It is based on open
source
technology under PHP license to develop graphic and web applications



Linux

is an open source operating system.


40.

What is token ring? What type of cables are used for token ring?

Ans
Token ring is the IEEE 802.5 standard that connects computers

together in a closed ring. Devices on the ring cannot transmit data

until permission is received from the network in the form of an



electronic 'token'.

There are three major physical token ring cabling systems; Shielded


Twisted Pair (ST
P), Unshielded Twisted Pair (UTP), and optic fiber.


41.

What is Ethernet ? To which OSI layer does Ethernet belongs?

Ans

Ethernet
is

a Local Area Network (LAN) cabling and signaling specification for
baseband networks. Ethernet uses a bus or star topology for connecting different
nodes in a network. Ethernet belongs to both the Physical Layer (Layer 1) and the
Data Link layer (Layer 2)

in the OSI architecture.

42.

What is a collision ? How is
"collision" handled in Ethernet networks?

Ans

At any one instance, in an Ethernet network, only one device can transmit. If two
devices transmit at the same instance, then the signals from both devices will
collide and a "collision" will occur. When a "collision" occurs, the signals will get
distorted

and the frame will be lost. Collisions are very common in a Ethernet
network. Ethernet uses the Carrier Sense Multiple Access with Collision
Detection (CSMA/CD) media access control mechanism to detect and recover
from a collision.

43.

What is CSMA/CD?

Ans

C
SMA/CD is a media access control mechanism used in Ethernet to recover from
frame collision. The following steps are followed to recover from a collision.

Step 1
: Before an Ethernet device sends a frame on the Ethernet cable, it listens to
find if another

device is already transmitting a frame (Carrier Sense).

Step 2
: Once the device finds that other devices are not transmitting any frame, it
starts transmitting the frame. If two devices detect that the Ethernet cable is free
at the same time, then both w
ill start transmitting the frames (Multiple Access).
This will result in collision.

Step 3
: The Ethernet devices while transmitting the frames, also listen for the
collision. (Collision Detect).

Step 4
: If they detect a collision, both the devices stop s
ending the frame (back
off).

Step 5
: They retry the transmission after a logarithmic time
-
out period. This
process is repeated till the frame is transmitted successfully, for a maximum of 16
times. The frame is discarded after the 16th retry.

44.

What is pro
tocol? How many types of protocols are there?

Ans.


When computers communicate each other, there needs to be a common set of
rules and instructions that each computer follows. A specific set of
communication rules is called a protocol.

Some protocol: PPP,
HTTP, SLIP, FTP, TCP/IP


45.

What is the difference between Networking and Remote Networking?

Ans.


The main difference between Networking and Remote Networking, is the
network which we use in offices or other places locally such LAN or INTERNET
and remote net
working is one which we use TERMINAL Services to
communicate with the remote users such WAN.


46.

What is point
-
to
-
point protocol?

Ans
.

A communication protocol used to connect computer to remote networking
services include Internet Service Providers. In networking, the Point
-
to
-
Point
protocol is commonly used to establish a direct connection between two nodes.
Its primary use has been to
connect computers using a phone line.


47.

How gateway is different from router?

Ans
.

A gateway operates at the upper levels of the OSI model and translates