These
details contain all things covered in the course of TE 121 in the second
semester also many things explained as well as brief explanation but each part thought
the lecture, presentations and extra things related to the course. It analyses
in this document things explained are network and computer network,
transmission media, network software,
application of computer network and the satellites.
A
network refers to the connection between two or more devices that enables them
to share files, information or signals among users of that network. Computer
network is the process of collecting and connecting different computing devices
and enable them have the sharing of data or information.
In
computer network any device that is being connected is called node and what is
being shared among the devices is known as the services.
This
concept of the computer network may be used or applied in many areas like in
business, in education, at home, at military at hospitals and other social
issues. In business the computer network may be used though the client server
system whereby it involves the request and replies, where one person makes
order of the things needed through the network and the other receives the order
and makes the replies through the network. Through this people are able to do
even business through online purchase and sale, make the view on the currency
change in a particular day and time. For
example the value of a dollar compared to the Ural, buying a car online
obtaining the book from internet and getting the ticket through a network.
Network
is also applied at home where it help much in accessing the remote information,
makes people be able to communicate among themselves also in sharing of the
information from one colleague to another in the society. This also used in
education whereby it computer network help much in finding out the teaching and
learning materials in schools and colleges, it also help much in the
communication among people in the education sector or among the education
stakeholders. The good and well accessible computer network once available help
in accessing much of the e-learning where by the student can be able to make the
follow up on what is being taught in class while is far away from the area
where teaching is taking place also the teacher may be able to access the
student while is not in classroom, for example doing of the exam online. Help
also in storage of resources that are used in teaching and learning process for
the next use and also facilitate in management of the educational program and
institution. In hospitals it help in
disease quire through finding different method of disease medicine and other
medication related to the disease, it also assist in doing many scientific
research on different kinds of disease that erupt or are virus affected. For
example research on HIV/AIDs. People in the society are using networking in
finding the information on many matters like politics, employment, marketing,
schooling opportunity in the areas.
a.
Sharing of resources among the computers that are
connected together. For example sharing the modem, scanner, and printer.
b.
Faster sharing of information and files across the
network, this enables most efficient communication among the users of the
network.
c.
Helps much in serving the cost since the program may be
in one computer and be shared by other computers and all get the access of that
program.
d.
The information being stored in the computer network
are reliable and up to date and be shared by different people in different
location.
I.
The individuals may fail to obtain the access of the
network when the central system is destroyed or fail and this makes both
hardware and software non-use.
II.
Once the whole system is collapse it becomes difficult
to trace the problem and make the recover to each computer and once done needs
a lot of cost.
III.
The whole computer network is highly dependent to
electric current thus once it is not present the system cannot be archived by
the user.
The
network can be classified on basing on the geographical area, access
restriction and according to the model employed by the node. In personal area
network (PAN); a network sharing of the network is done by few people found in
the area of few meters. This method can be conducted either being wired or
wireless. In the local area network (LAN); the network sharing is done in the
limited geographical area like home, school, hospital, working place and police
station. Under LAN one computer may be served as the sever of other computer on
which they share a network, where by those computer which shares a network from
the central computer are called the working stations. This type is more
efficient than the personal network since it accommodates more people in a
system used. On metropolitan area network (MAN); is the network that is shared
by many individuals in the given geographical area such as city or large
companies and this make communication reliable. In the wide area network IS
covered under the large area on which many individuals are found. WAN covers a
large area such as a country and connects the world together and is more
efficient than the all kinds of network although once a system is compromised a
problem become difficult to be traced back also once is identified its
maintenances becomes more closetful to care it.
The
network category can be point to point or a broad cast model. In point to point
model the information flows or moves in a specific direction across the network
in order to get from one node to the other node. Under this people who
communicate are those found in same direction or class whereby under the
broadcast model the message sent the message sent or shared by all members in
the network. In wireless local area network sharing of the information between
the computers is well facilitated among the individuals although this kind
involves the use of high cost in doing initial sharing of the information. During
the initial stage of doing the computer connection involves the use of the
devices that help in connection this involves the use of hubs, repeaters,
bridges, switch and routers. Those devices when well connected in the manner series
they lead to the network topology. Network topology is the way on how different
computers and other devices in a network are arranged to each other and the way
used by the signals to get transferred from one device to each other device.
The route may be bus topology, ring topology and star topology. In bus topology
the computer devices are connected in the liner way where the signals are being
transferred in a continuation form from one device to the other device. In ring
topology the signals being transferred are moving from one point to other point
through the cycle form while in star topology the one computer is being
connected to other computers which shares the signals from it and this uses the
hub to connect the all devices in the network here each device has its own wire
which is used to connect it in a central network. This mode has advantage of
connecting many devices at a time and once a problem occurs it is easily to
trace the problem and get fixed.
Transmission
media refer to means through which the signals travel over a network. This
method of transmission can be guided or unguided media. Conducted media or
guided media refer to the one in which there is use of a wire or optical fiber
in the transmission of the signals in a network from the sender to the
receiver, in unguided or wireless uses the radio waves of different
frequencies. Also the transmission media during developing depend on the
bandwidth, transmission impairment, interferences and number of receivers.
Guided transmission media thus depend on the distance to which signals travels
and nature of the media weather is point to point or is multi- point. The
twisted pair is highly susceptibility to interferences and noise and once
damage occur the repair needs high cost to be used.
In
the unguided or wireless media the signals are being transmitted through all
directions and can be received in all directions by many antennas. This kind of
connections is much widely used for connecting laptops in the local area
network. As many kind are this method is also having its limits such as it is
more expensive poor security of data, slow in running the network when many
users are present, this is also highly suspected to electrical interference
from light and radios.
The
wireless transmission can be infrared transmission in which signals are sent
using infrared light waves at a frequency too low of about (1-4 megabits per second) for human eyes to
receive and interpret. Infrared ports are found on laptop computers, wireless
mice, printers TV remote -control units and cameras. For communication to take
place between the sending and receiving device, the line of sight is
required-i.e. there should be no obstacle between transmitter and receive
Infrared transmission is confined to short range.
Wireless
Fidelity (Wi-Fi). It is a new wireless technology for connecting portable devices
and handheld computers to Ethernet LAN. This one it operates 2-25 gigahertz, wireless
transmission used up to 300 feet. Allows wide variety of nearby device
communicate with one another without physical connection. Bluetooth is a short
range digital standard aimed at linking cell phones and is useful for short
range communication only. Involves earthbound microwave systems which transmit
high-speed radio signals in a line-of-sight path between relay stations spaced
approximately 30 miles apart. Use the atmosphere as the medium through which to
transmit signals. Cellular phone system is a radio communications technology
that divides a geographic area into small areas or cells typically from one to
several square miles in area. This
division depends much on the size or the number of users in the given
geographical area. Each cell has its own low-power transmitter or radio relay
antenna device to relay calls from one cell to another. This technology is used
to support mobile phone service, and mobile voice and data communications. This
technology is used to support mobile phone service, and mobile voice and data
communications.
Digital
data/signals are method of storing, processing and transmitting information
through the use of distinct electronic or optical pulses that represent the
binary digits 0 and 1. Computers and all electronic devices send and receive
digital signals.
In
analog data/signal wave form (or signal) is characterized by being continuously
variable along amplitude and frequency is the number of times a radio wave
repeats during specific time intervals. Communication modes, a communication
mode specifies the capability of a device to send and receive data it does so
by determining the direction of the signal between two connections and this may
be simplex mode in which data goes in one direction only or half- duplex mode
where the data goes in both directions but at time goes in one direction and in
other direction at a next time and when the signals goes in both directions at
a time is called full-duplex mode. Also in a computer the devices are not able
to communicate to analogue lines and now is able to communicate over the
digital signals where by the modem is able to be used and now is translating
the analogue signals to digital signals by modulation process and by
demodulation where it converts the digital signals to analogue signals which
are sent to the network.
Web
browser application is the application of software designed to enable users of
the application to access, retrieve and view document and other resources to
the World Wide Web (www). This help much in finding of many useful materials
for example Operamin, Google chrome, safari, Firefox. The primary purpose of the web browser is to
bring information resources to the users of the browser in which the access of
this depend on the correctly used URL (Uniform Resource Identifier) and the
findings may be fining image, video, audio, pages, location and other pieces of
content.
Google
search engine are program in the browser application which help in searching of
the document that are available in the system based on the words of the search
terms. For example Google, Bing, and Yahoo although the mostly and commonly
used search engine is Google. The searching engine is more efficiently through
sing different search methods like use of key words of the search engine, using
the correct URL of the certain website which reads to the opening of the
relevant pages that are related to the certain search.
The
use of Google search method involves the use of different technique search as
Boolean And, Boolean Or and those methods helps much in finding of many
resources that are more helpful in education and other sectors like business
and other social aspects like journey. In education this help in finding of
different teaching and learning material like books, stimulations like audio
and videos also help in finding dictionary that gives the meaning of difficult
words to learners. This search engine helps the parents to obtain the schools
for their children and finding their results. In business the search engine
also helps the people in business to find the areas where can find the market of
goods, finding the stocks, converting of units, flight and searching maps. In
the society the search engine may be used in weather forecasting, searching the
sun rise and the sun set in different places, finding of the public data,
searching movies and other packages. In public data it may be used to search
different governmental data such as population, employment. Google hacking is
the most method used by the hackers in finding things or webs to be exploited.
Hackers are intelligent people with many computer skills and uses those skills
to exploit the vulnerability that are present in computer system get compromised.
Thus when those vulnerability are not controlled, this lead threats exploitation
of the information and the whole system get compromised. The hackers uses
different method on the process of hacking through phishing, drive dumping,
ring, shoulder surfing , eavesdropping, in this process the attackers of
hacking normally follow the procedure before and after hacking they start with
reconnaissance, scanning, gaining access, maintain access and covering truck.
Although other hackers try to exploit the information and does the
disconnection from the internet and then after they reconnect again after
installation of new.
In
this networking the page that help the person to view or interact with the page
that is intended is called webpage the collection of many pages leads to
website. Thus once need to access the certain website one need to know the
collect URL which is needed to be used in making the access of the websites.
- Website
is more usefully in education, through finding books, journals and
simulations.
- It
is used in finding of job opportunities that are found on the area,
foreaxample in private organizations and education sector.
- Finding
education stakeholders.
- It
minimizes the cost it is represented as whole.
- It
needs highly level of technology in developing it.
- Since
has built up with many pages, it consumes a time in looking to the
specific page.
- It
can be accessed by hacker and study the vulnerabilities present and lead
to loss of data.
- They
need to be paid for its presence thus few of organization owns it.
An electronic mail is the established system that is
used in communication among people where by the users of a mail is able to send
and receive the massage from one individual to the other individual. During
communication people can send and receive video, audio, photos, message,
documents and other materials. The use of this network needs the internet
connection and all users are supposed to have the mail account.
Important things needed during establishing the
E-mail
·
The names to be used.
·
Date, month and year of birth. Here the
person should be with age of eighteen years and above.
·
Place or the nationality of the
individual.
·
Choosing of the strong password. A
strong password is the one which cannot be gassed by anyone who use not the
user of the mail although it is advised that names of the relatives or hobbies
should not be used during creating the password because are the one prone to be
hacked.
·
The mobile number to be used in
notifications in a mail or during making restore of E-mail account.
v It
enables the user or owner of the account to have a YouTube account.
v The
account helps much in making the blogger of an individual.
v This
help in the installation of the software in androids like watsap.
v In
computer communication it is a safe method which is not prone to viruses.
v Enables
most of people to communicate through this since few conditions are needed.
v This
method is highly prone to be attacked and the communication that is done
through this method may be exploited by the hackers.
Software
is any application that is not manually in the system, in the computer network
it involves all application program that are used in network system. In this
category there is a protocol which is followed during doing the communication
in a network. A protocol is a set of established and agreed system upon the
certain need to enhance reliable and effective communication on a network. This
protocol can be made by the vendor or by networking standard organization thus
involves the set of rules and regulation and procedures for computers to
exchange data or information. For
example two computers to exchange data must be in the same protocol and this
involves.
Transport
Control Protocol (TCP).
Internet
Protocol (IP).
Protocol
Suite (PS)
In the Network protocol involves
Internet
Message Access Protocol (IMAP)
File
Transfer Protocol (FTP)
Hypertext Transfer Protocol (HTTP).
On
the above level of communication network protocol one layer on the upper
depends much on the lower layer of communication. For example the transfer of
one type of the file to be transferred needs the hypertext transfer protocol
(HTTP); also the internet message access protocol needs both the hypertext
transfer protocol and the file transfer protocol.
v It
helps to send data over the internet.
v Has
an application in e-mail using through communication.
v Is
used in studies like being taught in schools
v Helps
in access of the information when the protocol is well designed
v The
knowledge about the network is used in requesting and delivery of webpage.
v Help
in communication system among the members of the society
v Makes
people in the areas to send and receive and send the information
v Helps
the students to send their file and other academic work through the e-mail
v Through
used protocol is easily to fix the problem once occurs.
v It
involves high cost on establishing it
v Needs
the expertise of controlling the whole system
v The
materials needs high cost in managing and maintaining them
v The
system become useless on the remove of the lower layer or network layer and
makes the communication to difficult.
v It
has lead to increase of network climes especially for young.
Satellites
communicate by using radio waves to send signals to the antennas on the Earth.
The antennas then capture those signals and process the information coming from
those signals.
It
is also used for TV broadcasting. Satellites uses microwave frequencies for
communication with each other using inter-satellite links and with earth
stations.
Ø
Scientific data (like the pictures the
satellite took),
Ø
The health of the satellite,
Ø
Where the satellite is currently located
in space.
Services
offered by satellite services in its types
v Fixed
services satellite (FSS).
Examples
Point to Point communication
v Broadcast
services satellite (Direct BS).
Example
TVs and Radios
·
It is used for mobile and wireless
communication applications independent of location.
·
It covers wide area of the earth hence
entire country or region can be covered with just one satellite.
·
It co-exists with terrestrial microwave
line of sight communication.
·
It is easy to install and manage the
ground station sites.
·
It does not incur much of the costs per
VSAT site.
·
It has small fading margin on the order
of about 3dB.
·
It is used in wide variety of
applications which include weather forecasting, radio/TV signal broadcasting,
gathering intelligence in military, navigation of ships and aircrafts, global
mobile communication, connecting remote areas
·
LEO and MEO satellite types have lower
propagation delay and lower losses compare to GEO satellite. This will help
them to be used for global coverage.
- Satellite
has been constructed for years. Moreover satellite design and development
requires higher cost.
- Satellite
once launched, requires to be monitored and controlled on regular periods
so that it remains in the orbit.
- Satellite
has life which is about 12-15 years. Due to this fact, another launch needs
to be planned before it becomes un-operational.
- Redundant
components are used in the network design. This needs more cost in the
installation.
- In
the case of LEO/MEO, large number of satellites is needed to cover radius
of earth. Moreover.
A
collection of two or more computers interconnected by the telephone lines,
co-axial cable, satellite links, radio and microwave transmission and some
other communication techniques. A
computer network is a group of computers that are connected together and that
communicate with one another for a common purpose.
Although
the computer industry is young compared to anther industries (e.g., automobiles
air transportation), computer have made spectacular progress in a short
time. During the first two decades of
their extrinsic, computer system highly centralized, usually a single large
room. A medium size company or
university might have had one or two computers, while large instructions had at
most a few dozen. The idea that within 20 years equally powerful computers
smaller than postage stamps would be mass produced by the millions was pure
science fiction.
The
merging of computers & communications has had a profound influence on the
way computer systems are organized. The concept of the computer center as a
room with a large computer to which users bring their work for processing is
now totally obsolete. The old model of single computer serving all of the
organizations computational needs has been replaced by one in which a large
number of separate but interconnected computers do the job. These systems are
called computer networks.
Two
computers are said to be interconnected if they are able to exchange
information’s. The connection need not be via a copper wire; fiber optics,
microwaves, and communication satellites can also be used. By requiring the
computer to be autonomous, we which to execute from our definitions systems in
which there is a clear master/slave relation. If one computer can forcibly
starts , stop, or control another one, the computers are not autonomous. A
system with one control unit and many slaves is not a network; nor is a large
computer with remote printers and terminals.
There
is considerable confusion in the literature between a computer network and a
distributed system. The key distinction is that in a distributed system, the
extended of multiple autonomous computers is transparent to the user. He can
type a command to run a program. And it runs. It is up to the operating system
to select the best processor, find and transport all the input files to the
processor, and put the result in the appropriate place. In other words, the
user of a distributed system is not aware that there are multiple processors;
it looks like a virtual uni-processer. A location of jobs to processors and
files to disks, moment of files between where they are stored and where they
are needed, and all other system functions must be automatic.
With
a network, user must explicitly log on to one machine, explicitly submit jobs
remotely, explicitly move files around and generally handle all the network
management personally. With the distributed system, nothing has to be done
explicitly it is all automatically done by the system without the users
knowledge.
In
effect, a distributed system is a software system built on top of a network.
The software gives it a high degree of cohesiveness and transparency. Those
distinction between a network and a distributed system lies with the software
rather than with the hardware. Nevertheless, there is considerable our lap
between the two subjects. E.g., both distributed system and computers networks
need to move file around. The difference lays in whom in vokes the movement,
the system or the user.
Local
area network, generally called LANs, is privately-owned networks within a
single building or campus of up to a few KM in size. They are widely used to
connect personal computers and workstation in company offices and factories to
share resources (e.g., printers) and exchange information. LANs are
distinguished from other kinds of networks by three characteristics:
1. Their
size,
2. Their
transmission technology,
3. Their
topology.
LANs
are restricted in size, which means that the worst-case transmission time is bounded
and known in advance. Knowing this bound makes it possible to use certain kinds
of designs that would not otherwise be possible. It also simplifies network
management.
A
metropolitan area network, or MAN (plural: MANs, not MEN) is
basically a bigger version of a LAN and normally uses similar technology. It
might cover a group of nearby corporate offices or a city and might be either
private or public. A MAN can support both data and voice, and might even be
related to the local cable television network. A MAN just has one or two cables
and does not contain switching elements, which shunt packets over one of
several potential output lines.
Wide Area Networks (WAN):
A
wide area network, or WAN, spans a large geographical area,
often a country or continent. It contains of machines intended for running user
(i.e., application) programs. We will follow traditional usage and call these
machines hosts. The term end system is sometimes also used in
the literature. The hosts are connected by a communication subnet, or just subnet
for short. The job of the subnet is to carry messages from host to host,
just as the telephone system carries words from speaker to listener. By
separating the pure communication aspects of the network (the subnet) from the
application aspects (the hosts), the complete network design is greatly
simplified.
In
most wide area networks, the subnet consists of two distinct components: transmission lines & switching elements. Transmission lines
(also called circuits, channels, or trunks) move bits between machines.
The
switching elements are specialized computers used to connect two or more
transmission lines. When data arrive on an incoming line, the switching element
must choose an outgoing line to forward them on.
In
most WANs, the network contains numerous cables or telephone lines, each one
connecting a pair of routers. If two routers that do not share a cable
nevertheless wish to communicate, they must do this indirectly, via other
routers. When a packet is send from one
router to another via one or more intermediate routers, the packet is received
at each intermediate router in its entirety, stored there until the required
output line is free, and the forwarded.
A subnet using this principle is called a Point to Point, store and
forward or packet switched
subnet. Nearly all wide area networks
(except those using satellite) have store and forward subnet. When the packet are small and all the same
size, they often called cells.
Mobile
computers, such as notebook computers and personal digital assistants (PDA) are
the fastest growing segment of the computer industries. Many of the owners of these computers have
desktop machines on LAN’s and WAN’s back at the office and want to be connected
to their home base even when away from home or en route. Since having a wired connection is impossible
in cars and airplanes, there is a lot of interest in wireless network.
Wireless
networks come in many forms. Some universities are already installing antennas
all over campus to allow students to sit under the trees and consult the
libraries card catalogs. Here the
computers communicate directly with the wireless LAN in a digital form. Another possibility is using a cellular (i.e.
portable) telephone with a traditional analog modem. Direct digital cellular service, called CDPD (Cellular Digital Packet Data) is
becoming available in many cities.
It
is now time to turn our attention from the application and social aspects of
networking to the technical issues involved in network design. There is no
generally excepted taxonomy into which all computer network fit, but two
dimensions stand out as important: transmission technologies and scale. We will
now examine each of these in turns.
Broadly
speaking, there are two types of transmission technologies:
- Broadcast
networks.
- Point-to-point
networks.
Broadcast networks: It
have a single communication channel that is shared by all the machines on the
network. Short messages, called packets
in certain contexts, sent by any machine are received by all the others. An
address field within the packet specifies for whom it’s intended. Upon
receiving a packet, a machine checks the address field. If the packet is
intended for itself, it process the packet, if the packet is intended for the
other machine, it is just ignored.
Broadcast
systems generally also allow the possibility of addressing a packet to all
destinations by using a special code in the address field. When a packet with
this code is transmitted, it is received and processed by every machine on the
network. This mode of operation is called broadcasting.
Some broadcast system also support transmission to a subset of a machines,
something now has multicasting.
Point-to-point networks:
It consists of many connections between individual pairs of machines. To go
from the source to the destination, a packet on this type of network may have
to first visit one or more intermediate machines. Often multiple routes, of
different lengths are possible, so routing algorithm play an important role in
point-to-point networks. As a general rule (although there are many
exceptions), smaller, geographically localized networks tend to use
broadcasting, where larger usually are point-to-point.
Whenever
we want two devices – transmitting and receiving device to communicate with
each other, we need hardware’s to achieve that.
We would be discussing about the various hardware such as:
1. Sender
and Receiver hardware
2. Communication
devices
3. Communication
channels
Sender
and Receiver Hardware:
Following
hardware are used for handling communication messages, data transfer etc.
Data
communication is done using various communication devices and softwares
interconnected for information exchange.
The devices used to communicate a data in communication network are
called Workstations. These workstations
may be computer, terminal, printer, telephones and other communication devices. Each workstation is connected to something
called a Data Communication Network Mode.
Multiplexer: As
the name suggests, multiplexing is a form of data transferring which are
communication channels and is used for several transmission. For e.g. the telephone lines that we used for
our daily conversation can carry 100’s and even 1000’s of conversations using
multiplexing. In other words
multiplexing is a type of network which allows a number of simple, low cost
terminals to share each communication lines introduces almost no delay and requires
no special computer software.
Communication devices: There
are several types of communication devices or interface used in data
communication. These interfaces are
connection between receiver and sender hardware involved in data communication
and the communication network. Some of
these interface or communication devices are discussed below:
1.
Modems:
Modulator and Demodulators are devices which converts digital signals in to
analog for transmission over the analog transmission facilities such as
telephones. At the receiving end, a modem
performs the reverse function and converts analog signals into digital form.
2.
Codec
performs
the opposite function of a modem. A
communication port / adapter is a connector on the computer, which is used as
an entry to departure point for data involved in data communication. A common type of communication port is
RS-232c. This adapter is used for
transfer of data between the computer and the telephone lines.
3.
Line
Drivers are simple devices used to transmit digital signals
over short distances. These devices do
not modulate or demodulate signals, but use filters to reduce the high
frequency components and the modified signal is transmitted directly over the
media.
The
most basic hardware required for communication is the media through which data
is transferred. There are several types
of media, and the choice of the right media depends on many factors such as
cost of transmission media, efficiency of data transmission and the transfer
rate.
Some
of the following transmission Medias is as follows:
- Two wire open
line: This is
the simplest of all the transmission media. It consists of a simple pair of metallic
wires made of copper or some times aluminums of between 0.4 and 1mm
diameter, and each wire is insulated from the other. There are variations to this simplest
form with several pairs of wire enclosed in a single protected cable
called a multi core cable or molded in the form of a flat ribbon.
This
type of media is used for communication within a short distance, up to about 50
M, and can achieve a transfer rate of up to 19200 bits per second.
a. Twisted Pair cable:
A twisted pair consists of a pair of insulated conductors that are twisted
together. The advantages of a Twisted
Pair cable over the Two Wire Open Lines are; it provides better immunity from
spurious noise signals. As the Two Wires
are closed to each other, both pick equal interferences caused by extraneous
signal sources and this reduces the differential signal added by the noise. Twisted
Pair cable is used for communication up a distance of 1 KM and can achieve a
transfer rate of up to 1-2 MBPS. But as
the speed increased the maximum transmission distances reduced, and may require
repeaters.
Twisted
pair cables are widely used in telephone network and are increasingly being
used for data transmission.
v Co-axial Cable: A
co-axial cable consists of a solid conductor running co-axial inside a solid or
braided our annular conductor. The space
between the two conductors is filled with a dielectric insulating material. Larger the cable diameter, lower is the
transmission loss, and higher transfer speeds can be achieved. A co-axial cable can be used over a distance
of about 1 KM and can achieve a transfer rate of up to 100 MBPS.
A
co-axial cable is of two types- a 75 Ohm cable which is used by the cable TV
operators and 50 Ohm cable which is used in high speed broad band networks and
is low loss cables.
Fiber
Optic Cables:
A
fiber optic cable carries signals in the form of fluctuating light in a glass
or plastic cable. An optical fiber cable consists of a glass or plastic core
surrounded by a cladding of a similar material but with a lower refractive
index. The core transmits the light while the change in refractive index. The
core transmit the light while the change in refractive index between the core and the cladding causes
total internal reflection, thus minimizing the loss of light from fiber.
As
light waves gave a much wider wand width then the electrical then the
electrical signal and are immune from electromagnetic interferences, this leads
to high data transfer rate of about 1000 mega bites per second & can be
used for long & medium distance transmission links.
Radio,
Microwaves & Satellite Channels use electromagnetic propagation in open
space. The advantage of these channels lie in their capability to cove large
geographical areas & being inexpensive than the wired installation.
The
demarcation between radio, Microwave & satellite channels lie in the
frequencies in which they operate. Frequency bellow 1000 MHZ are radio
frequencies & higher the Microwave frequencies.
The
radio frequency transmission may be bellowing 30 MHZ above 30 MHZ & thus
the techniques of transmission are different. Owing to the characteristics of
the ionosphere, frequencies bellow 30MHZ are reflected back towards the surface
of the earth. Above 30Mhz propagation is on line of sight paths. Antennas are
placed in between the line-of- sight paths to increase the distance. Radio
frequencies are prone to attenuation and, thus, they require repeats along the
path to enhance the signal. Radio frequencies can achieve data transfer rate of
100 Kbps to 400 Kbps.
Microwave
links use line- of- sight transmission with repeaters placed every 100-200 Kms.
Microwave links can achieve data transfer rates of about 1000 Mbps.
Satellite
links use microwave frequencies is the order of 4-12 GHz with the satellite as
a repeater. They can achieve data transfer rates of about 1000 Mbps.
Network Concept and Classifications:
Communication
using computer has brought a revolution in the world of computer technology,
particular in the field of computers. We
have always heard of networking or the term network, a network is a way or
means of transmitting or receiving information one or more sources. As an e.g. car salesman after years in the
business, have developed a network of associates. When the car salesman needs a
car to make a sale the car salesman calls out to his network to retrieve
information on the location of the car. Employment agents also develop a
network. Their customers become their network. Employment agents will
frequently keep in touch with their clientele for possible openings or to
locate a candidate for an opening. Without the capability of networking, these
two people would have a difficult time. It is the same in computing. Networks
provide the means for locating transporting information.
In computing networks, the origin of the
information request utilized the service of a network to locate & return
the information. This is done with addresses. In the two previous examples of
the car sales man & the employment agent, a telephone number can be
considered the address of their associate or client. Addresses in computer
networking are used in the same manner. These addresses identify the network
resource. There are two popular architectures for networking – hierarchical
& peer.
Hierarchical
addressing is defined in a master slave relationship. In hierarchical network,
the master controls the network & therefore assigns addresses to the
network resource. This architecture has the mainframe as the master & all
network resources as slave. The bases of this is that if the master does not
know beforehand of a network resource existence through a pre- defined address
then that resource cannot participate in the network.
Peer
networking does not need pre- defined networking addressing. Instead, each
resource on the network is seen as a peer. Each network resource is a peer to
the other network resource. When a new network resource joins the network it
introduced itself & notifies its peer to any other network resources that
it knows about peer networks are share network information. The entire computer
network can be classified into two board categories. They are (a) LAN (Local
Area Network) (b) WAN (Wide Area Network)
As
numbers of system grow within an organization, a need is felt for sharing
expensive resource and exchanging data and information between systems. This
need of information exchange and resource and sharing with in a organization
has given birth to a local area network or LAN.
A
LAN is a data communication network, which connects many computers or
workstation (Computer’s Terminals, Printer etc.) and permits exchange of data
& information among themselves, with in a localized area, typically
confined to a building, or a cluster of buildings. The distance between two
communications prints connected on the same LAN channels is usually up to 02 to
05 kms.
LANs
are not rigidly defined but tend to share most of all of the following
characteristics.
§ The
transmission media is shared by all the connected devices in the network.
§ Each
device is connected in the network can either operate stand alone or in the
network.
§ Area
covered is small.
§ Data
transfer rates are high, usually 1 Mbps- 100 Mbps (Million of bits per second).
§ Each
device connected in the network can communicate with any other device in
network.
§ Cost
of setting up the network is usually low.
A
network topology refers to the physical lay out of the network in which all the
devices are connected. This includes all the hardware that makes up the
network. The points of the connection to the network by the station are calls
Nodes or Link stations. There are several types of topographical design &
strategies are used to implement LAN. The majority of these are based on three
types of topologies.
a)
Star b) Bus c) Ring
Each
topology has its advantages & disadvantages.
8.1.1.1
Star
Topology
Star
topology is shown bellow. In this topology. A number of stations are connected
directly to a central station or controller. Communication on the connecting
links between the stations & the central station of the star topology can
be bi- directional and are point to point. A station on this type of network
passes an information frame to the central controller, which then forwards the
information to the destination station. The central controller manage and
controls all communication between stations on the network.
Star
Network
Failure
of a station on a star network is easy to detect and can be remove from the
network. However, failure of the central controller will disable communication
through out the whole network.
8.1.1.2 Bus Topology
A bus topology is shown bellow all stations
are connected to a single communication line. This single communication line is
referred to a bus. Information frames originating at a station are propagated
away from the station in both directions on the bus. Each station on the bus
interrogates the information frame destination address failed for its on
addresses. If the destination failed does not mach the station address, the
station discards the information frame back on to the bus. If the destination
address matches the station addresses, it accepts the information frame &
processes the frame.
An
extension to the bus topology is tree topology is in the following figure. Tree
topology extends the branches of the bus topology allowing more stations to
access the bus.
Bus Topology
On
a bus or tree network there is no central point for management &
control. These function ions are
distributed to each station on the bus. A brake in the bus can be difficult to
locate but limits the outage to communications between stations that traverse
the broken point.
8.1.1.3 Ring Topology
A
ring topology is shown bellow. Local area network that have each station
attached to an adjacent station using point to point links from a physical
ring. Each station attached and active to the ring regenerate the information
frame, then retransmits the information frame on the ring. The ring itself is
logically circle and the information travels in one direction.
Failure
of a station in a ring topology disrupts the ring because the information frame
is not regenerated. Additions or deletions of stations of the ring can be
disruptive, if the changes are not managed properly.
LAN Hardware and Software
As
we have seen so far, to realize a LAN process, several functions are to be
performed. These are so specialized in nature the require hardware specially
built for such purpose. Here we will discuss briefly the basic hardware
components of LAN, these are:
(A) Network
Interface Unit (NIU)
(B) Servers
(C) Work
Station
A)
Transfer
mission Channels
Generally
following four types of channels are used for data communication in a LAN. They
are:
(i)
Twisted Pair Cable
(ii)
Coaxial Cable
(iii)
Fiber Optic Cable
Network
interface units connect each device in the LAN network to shared transmission
device. It contains the rules or logic to access the LAN. NIU is also used for
to implement LAN protocols and for device attachments. Its functions depend on
the type of topology used in LAN.
B)
Servers
One
of the major benefits of implementation of LAN is sharing expensive resources
such as storage device, printer etc. this is achieved through providing servers
on the LAN. It is a dedicated computer that controls on or more resources. This
contains both hardware & software for LAN. Three major categories of servers
used in LANs are
(i)
File Server
(ii)
Printer Server
(iii)
Modem Server
In
a networking file server is used to share storage space for files. Beside
providing storage space for files in a LAN environment, it is used for talking
periodical backup, and also to provide gateway to other servers with in &
between LANs.
Similarly
printer server is use to handle printing works of all workstations connected in
the network. In the LAN environment also modem is required to get connected to
other network or simply to use a telephone. A modem server is used to share
these expensive resources by all connected workstation in a networking ring.
LAN Software/
Operating System
As
the name suggest LAN operating system is required to operate on the LAN system,
manage the tremendous work load with a number of various types of server
attached to it. It has basically two aspects (i) Server Software (ii) Work
station Software. As case of other multi user operating system, LAN operating
system also facilitate the sharing of expensive resources such as printer,
storage space etc. among all LAN users, provides security of data permits
connections to other network.
There
are various types of LAN operating systems for example Novel Netware, LAN
server, omni met, PC Net, IBM PC LAN, Etherlik plus etc.
As
the name suggest, WAN spread across countries and continents satellites being
one of the transmission media.
A
wide area network WAN is a network that links separate geographical location. A
WAN can be a public system such as the Public Switched Telephone Network (PSTN)
or one of the various packet switched services provided by the public
telecommunication authorities. WANs can also use most other types of other
types of circuit including satellite networks, ISDN, Value Added Networks
(VANs/VADs). The network can be a private system made up from the local
telephone company or set up using public systems as virtual private network. A
virtual private network is one which operates in the same way as a private
network but which uses public switched services for the transmission of
information.
The
main distinguishing feature between a LAN and WAN is that, the LAN is under the
complete control of the owner, whereas the WAN needs the involvement of another
authority like the telephone company. LANs are also able to handle very high
data transfer rates at low cost because of the limited area covered. LANs have
a lower error rate then WANs.
Communication Switching Techniques
In
a WAN, two computing devices are not connected directly. A network of switching
nodes provides a transfer path between the two devices. The process of
transferring data blocks from one node to another is called data switching.
There
are three switching techniques commonly employed and these are:
i)
Circuit
Switching
In
circuit switching there is a dedicated communication path between the sending
and receiving devices. The dedicated path is a connected sequence of links
switching nodes. A conventional telephone network, where a dedicated path is
set between the called parties for the duration of a telephone call is an
example of circuit switching.
Communication
viz. circuit switching involves three steps-circuit establishment; data
transfer; and circuit termination. Circuit switching is mainly used for voice
telephone network, but is not that effective for data communication network, as
channel capacities are not fully utilized, as data communication equipments do
not generate data continuously.
ii)
Massage
Switching
Massage
switching is an alternative switching techni8que, where it is not necessary to
establish a dedicated path between the sending and receiving devices. In
massage switching, the sending device appends the destination address to the
massage and passes to the network; the massage is then passed through the network
from one node to another till it reaches the intended destination. Each
switching are electronic mails, computer files, telegrams and transaction
queries and responses. A complete exchange may consist of several messages.
The
basic disadvantage of massage switching is the variable delay at intermediate
switching nodes.
iii)
Packet
Switching
Packet
switching combines the advantages of message & circuiting switching. Packet
switching is functionally similar to message switching, in which data is
transmitted in blocks, stored by the first switching node it meets in the
network and it forwarded to the next and subsequent downstream nodes until it
reaches the destination. The length of data block is limited in packet
switching network. Typical maximum length of packets is between 128 bytes to
4096 bytes. There are two approaches to packet switching:
In
datagram approach, each packet is treated independently and may follow a
different path through the network. Packets may be reordered, dropped or
delivered in wrong sequence. The communication protocols provide the error
recovery sequencing of packets at the receiving device.
In
virtual circuit approach, a fixed logical path through the network from the
sender to the receiver is established before any packets are sent. This path
remains unchanged for the duration of the session. This is quite like circuit
switching, but no resources are reserved along the path. Packets are buffered
at intermediate nodes awaiting transmission.
The
switching techniques utilized the routine technology of data transfer. Routing
is responsible for searching a path between two computing devices that wish to
communicate and for following the data packets on this path. Devices such as
bridges, router and gateway provide this routing function.
i)
Bridges
Bridges
are used to connect two LANs that use identical LAN protocols over a wide area.
The bridge acts as an address filter which picks up packets from one LAN that
are identical for a destination on the another LAN and passes these packets on
the network. Bridges operate at the data link layer (layer 2) of the OSI model.
As all devices use the same protocols, the amount of processing required at the
bridge is minimal. If the distance between the two LANs is large, the user would
require two additional bridges at either end of the communication link.
ii)
Routers
Routers
can be used to connect networks that may not be similar. Routers provide
connectivity between two LANs or two WANs over large geographical distance.
Routers operate at the network layer (layer 3) of the OSI model. All routers
participate in routing protocols to access the network topology, and based on
this information routers computes the best route from a sender to the receiver,
For
large wide area network spanning thousands of kilometers, the normal practice
is to put network routers at suitable locations to minimize link cost for
leased link and provide adequate reliability from link failures. Networks and
other system are then connected to the nearest router.
iii)
Gateways
Gateways
are used to connect to dissimilar LANs. The term gateway and routers are used
interchangeably, though there is a subtle difference between the two. A router
operates at the network layer (layer 3) of the OSI model, whereas a gateway
operates on the application layer (layer 7) of the OSI model. A gateway is
required to convert data packets from one protocol format to another before
forwarding it, as it connects two dissimilar networks.
Public
networks are those networks which are installed and run by the
telecommunication authorities and are made available to any organization or
individual who subscribe. Examples include Public Switched Telephone Networks
(PSTN), Public Switched Data Network (PSDN), Value Added Service (VANs/ VADs)
and the Integrated Service Digital Networks (ISDN). We would be discussing the
main features of there services:
a)
Public
Switched Telephone Network (PSTN)
The
features of the PSTN are its low speed, the analog nature of transmission,
restricted bandwidth & its wide spread availability. As PSTN is designate
for telephones, modems are required when it is used for data communication.
b)
Public
Switched Data Network (PSDN)
The
term PSDN covers a number of technologies; all through currently it is limited
to Public Packet Switch Networks available to the public. The main features of
all PSDNs are their high label reliability and the high quality of the
connection provided. The can support both high & low speeds at appropriate
costs.
c)
Value
Added Services (VANs/ VADs)
In
value added services, the provider of such services must process, store and
manipulate the data that is carried on the network, that add value to it. The
technique can be used in specific types of business in which it is advantageous
to be able to share information with other companies in the same line.
d)
Integrated
Services Digital Network (ISDN)
The ISDN is
the networking concept providing for the integration of voice, video and data
servicing using data service using digital transmission combining both circuits
and packet switching techniques. The motivating force behind ISDN is that
telephone networks around the world have been making a transition towards
utilizing digital transmission facilities for many years.
The basic technique used in all forms of private WAN
is to use private (or more usually leased) circuits to link the locations to be
served by the network. Between these fixed points the owner of the network has
complete freedom to use the circuits in any way they want. They can use the
circuit to carry large quantities of data or for high speed transmission.
Private WIDE area network can be built using whatever
standard technology is available. The way private networks have generally been
set up has to specify .
By
using a modem in a laptop computer, explain practically how you can create a
network account and share to other computers supporting Wireless Network.
odem
is device or program that convert digital computer signal to analog signal to
transmit data over telephone or cable line then to receive these signal and
convert back to digital signal.
Computer
information store digitally telephone transmitted over the telephone
transmitted in the form of analogy. The modem sending modem modulates the data
into a signal with phones line, and receiving modem demodulates the signal back
into digital data.
Wireless
modem convert digital data into radio signal and back. There part of connection
modem of the main computer which receive the network for modem.
The
steps that used before create new account
v Insert
subscriber identity module (SIM) into the modem.
v Insert
the modem into the computer through the universal serial bus port (USB).
NOTE:
If modem is used for first time in the computer install the modem software.
The
following are the steps creation a network a new account as follows by using
modem.
✓ click the start bar.
✓ click the control panel.
✓ Click network and internet.
✓ Click network sharing and sharing
center.
✓Then choose and click set up a new
connection and network.
✓ Click set up wireless ad hoc (computer
to computer) network.
✓Then create account by naming network
account and security key.
The security must contain 8-63 characters.
➢Then save and click next for to allow
internet connection sharing.
Then
save and click next for to allow internet connection sharing.
Alternatively
way.
➢ Click network icon.
➢ Click open network and network Centre.
➢Then choose and click set up a new
connection and network.
➢ Click set up wireless ad hoc (computer
to computer) network.
➢Then create account by naming network
account and security key.
➢Then save and click next for to allow
internet connection sharing.
The
follows are step of sharing the network to other computer.
➢ Click the start bar.
➢ Click control panel.
➢ Click network and
internet.
➢ Click connect to
network.
➢Choose the account name
from host computer and connect.
➢Then write password
from host computers
➢Now the computer is able to share the network with
other computers.
What
is blog? Practically explain how to create a simple blog (you can create a
class blog) show a class how the blog owner will sign in the blog and add the
information to it ? How others users can access your blog? What they can do and
cannot do to your blog?
log
can be defined as the place of express yourself to the world. OR It is a place
to share your thoughts and your passions. Blogger is a person who keeps a blog.
Also sometime can be a tool for creating a blog like Google blogger. Blogging
is an action of writing a blog and adding information. For examples of common
blogs in Tanzania are Maswayetu blog, Muungwana blog, millardayoblog, Mzalendo
blog, Jamifolum blog, Mpekuzi blog, Massage blog. Requirements for creating
blog E-mail account which could be used in signing up and in, this can be from
gmail, yahoo and others.
The needed procedures of creating a blog are
v The
first thing to do is to open the search engine such as a Google and then type
the word ‘blogger’ then you click search
v After
obtaining the result then you select the option written “create a unique and
beautiful blog. it's easy and free.”
v After
selecting an option of creating a unique and beautiful blog you will find an
option written “create a blog” then select it.
v When
you select that option u will have to enter the gmail account then click next
where you will enter the password of the gmail account.
v Enter
the recovery Email account and click next.
v Till
here you will have already a blog but you will not be able to post anything
until you open the smallest blog within the largest one.
v This
will have option where you can enter the title of and the address of the blog
then you will click continue then you will see Congratulation,, “Your blog has
been created” on the screen then click
“start blogging now”.
TO
SIGN OUT
To sign out the owner can press or click the
icon of email on the right Conner and select sign out. After then the owner
will be already signed out of the blog. Also the group number one presented
this as a unique feature of their work in a case of blog what people can do and
can not do in my blog
o
People can add comments on a blog and
you can restrict adding comment on blog.
o
You can set a blog to be viewed by
public, private.
o
You can add author to your blog that
will have the same authority with. He/she can add any information, edit, and
post anything.
Searching
information in a network is a skillful task that requires the searcher to have
considerable techniques on searching information in a network. Basing on this
clue, explain practically different search engine techniques
earch
engine is the software system that is designed to search for information on
worldwide web. (www). Example of search engine Google, Bing, Yahoo, Ask.com,
Aol.com, Baidu, Internet archive, Chacha.com, search. The following are
techniques of search information in network search engine.
Google scholar:
This is the techniques which provide the simple broad search of scholarly
literature, by using Google scholar one may search different material across
many disciplinary such as books, articles and different scholar research from
different academic publishers. Google scholar ranks the document from the way
researcher do, means the full text for each document, where it was published,
who has written it and how it was cited from other scholar research. In the
Google search one have to type Google scholar and Google scholar search box
will appear where one can type to search.
Google books:
This is the technique used to search the full text of books that Google has
scanned and store on it database. It allows users to view pages from book which
appear in the search terms. Books can searched by typing the name of the book
or the name of the author, also the genre of the book thus in Google search one
have to type Google books and the Google book search box will appear here one
can write the name of the book or author. In Google book, books which are
public are available for full view and can be downloaded for free. Also there
are books which can be full viewed only if the publisher has given permission.
And there are preview books which are restricted to a limit number of pages to
be viewed by users.
Google calculator: Google calculator' this
technique enable us to perform different calculations through Google search
engine. Calculations like addition, subtractions, multiplication and other mathematical
problems can be solved by Google search engine. On how to use this technique go
to Google then type you calculation
Google map: A
Google map is a web mapping service developed by Google. It offers satellite
imagery, street map 360˚ panoramic views of street, real-time traffic condition
and route planning for travelling by foot, car, bicycle or public
transportation. The following are the procedure of Google mapping. First step
go Google then write “Google map”, after that you may get many option, then
click Google map.
Google phet simulation:
The suite of research based interactive computer simulation for teaching and
learning physics, chemistry, math and other science subject. This can run
online or downloaded free from the website. Google phet simulation is using of
searching engine to search the different simulation.
What
is Google hacking? Practically describe different Google hacking techniques
oogle
hacking, also named Google docking, Google hacking is the use of a search
engine, such as Google, to locate a security vulnerability on the Internet.
Google hacking involves using advanced operators in the Google search engine to
locate specific strings of text within search results. Search for terms within
the URL of a website inurl:
Ø Search
for a specific term or terms within the URL of a website. [ inurl:resume ] Tip:
The query must be a complete or whole term, meaning that you cannot extract a
term from a string of consecutive letters or numbers. Using the above example,
the following demonstrates what is and is not possible when using the inurl:
operator. Yes: [ my-resume-123 ] or [ my/resume/123 ] No: [ myresume123 ]
Google’s
hacking techniques
1.
GOOLGLE MENTALPLEX: You have to use these technique of
Google hacking to hack various page in Google, to do this you have type the
word Google mentalplex in Google you will find the page if actually from a
Google .. It was posted for April 2000 fool’s day.
If
you click on it, it sends to another page with a lot of information making fan
of you where you can choose and see its details. For example you can open the
page which acquire to choose among of difference pages motioned or if your page
which acquire you not mentioned above then you can turn back and type that kind
of page which acquire you then place on it, then the page will open and start
to peruse that kind of information on that page. for example you need the page
of ‘Tasisiya Kiswahili Tanzania’, then will type these page above on given
place to type then click on it then the page will be open then several
information will happen then select what you want to see.
2. GOOGLE GRAVITY: These is another technique in Google hacking
which you may use to hack different information and other techniques like how
to play Quitter, Terminals and snake games and other techniques which acquire
you. Therefore if you want to use these technique to hack information in Google
you have to type ‘Google gravity’ on Google then you will find a threat part
web page clawer Google and you will see the simulating Google part of moving of
phenomena these can be impressive for few second if you step away from you
computer is well and see the reaction of someone who does not know this trick
on the same note you can find on this web site few more tricks like play
Quitter, snake game and packman.
3. MATH TOOL FORMULAS: If
you type math formulas in Google then you will get more information about
mathematic calculation/ problems and you can perform different calculation as
well as drawing graphs using Google
4. ATARI BREAKOUT:
These are few magic words that provide a search result with a games that you
can play during working hours in order to refresh your mind. The trick is to
click on the image result rather than word result then you can have some fun
when playing this game.
5. GOOGLE DOODLES:
If you do not search anything but still press the I’m feeling lucky button you
will get all the Google’s doodles that Google has used in the past for specific
event and for specific country. You need to understand that Google has
different depend on the way you’re with different logos.
With
examples, differentiate between website and WebPages. Explain practically how we
can get different educational resources from different websites.
he
websites and WebPages are too commonly used words that are always used
interchangeably. However they are not the same at all and so it should be noted
that there are many existing differences between the two words. The differences
between the websites and the WebPages are in various aspects. The followings
are the major aspect in which the two words differ from each other. The aspects
are:
A
website is a well grouped collection of various related WebPages. A website
acts as a room of storing the WebPages. A webpage is a single part of a website
carrying a certain document or a media file. A webpage is the interface that
one opens when accessing the contents of the website.
Example of website is the UDOM SRMS website
while its WebPages are course evaluation webpage, course results WebPages as
well as the course works WebPages.
2:
Access address: A website is accessed by the address directly from the World
Wide Website (www). A webpage is accessed from the world wide website via a
Uniform Resource Locator (URL)
Example
a website can be accessed by the address www.udom.comwhereas
a webpage can be accessed by the address www.udom.ac.tz
whereas a user will be directly directed to the log in interface. So the
address of the website brings many results from the website while the address
of the webpage opens a certain specific page of the website
3:
DOMAIN NAME
A
website has a unique domain name and no any website that shares a domain name
with another.
WebPages
however shares a domain name. Various WebPages shares a common domain name from
the website.
4:
CONTENTS
A
website is multi-contented. This means that it comprises of many different
files, documents, media contents just to mention a few of them
A
webpage however contains a specific content such as files, documents, and
media.
Example,
in the website www.udom.ac.tz there are
various contents such as about university of Dodoma, the almanac, academic
timetable, and other while opening a webpage of academic timetable, what is
found inside is the timetable only, in the almanac what is found inside is the
year schedule of events of the university.
5:
SHARING ADRESS
A
website address cannot be directly shared to other user since it is always
available
A
webpage address can be directly shared to other users since it is uniform.
Example;
sharing an address to the video uploaded to a certain YouTube account one uses
a URL address to share the video to other user whereas a user opening that link
will be directed directly to the specific video and not to the YouTube
homepage.
6:
AUTHENTICATION
In
social websites such as Facebook and twitter, as well as in academic websites
such as UDOM SRMS the user need to register to get access to the contents. This
secures personal privacy.
In
webpages however, authentication is merely available. But happens in some cases
such as when one need to access the porn videos from YouTube, a user has to
verify that he is aged 18 or above. But the case is strict in websites.
7:
EDITORIAL ACCESS
In
website, editing the contents can be accessed by many authentic different
personnel/webservers.
In
webpage, editing the contents can be accessed by a single authentic user.
Example,
in the UDOM SRMS each webpage can be edited by the single authentic user.
People with access to edit the results, course works, students’ details, course
evaluation, and other webpages are different and each accesses a certain
webpage only.
8:
AVAILABILITY ON SEARCH ENGINE
Websites
are always available on the search engine’s database the world wide website
abbreviated as www. The WebPages are merely available on the search engine
since the user should know the exact address to find out the webpage.
For
Example; writing the word UDOM on the search engine may result on showing up
the related to UDOM, but the user cannot be directed exactly to the certain
webpage contained in the website.
Practically describe how to create different email accounts.
Mention other accounts that come with Gmail account and explain how to use
these accounts.
-mail is
a system for sending messages from one individual to another via
telecommunication links between computers or terminals. Email is used to send
things like files, graphic images, video, text and sound. Examples of e-mail
provider are Gmail, yahoo, msn, hotmail, Yandex, GMX, AOL, and outlook.
GMAIL ACCOUNT
Steps on
how to create Gmail account.
i.
Open Gmail in your
Google search engine
ii.
enter all the
required information
iii.
choose a username for your email address,
choose your Gmail address
iv.
Choosing a
password for your email this help to
protect your Gmail account with a
security question.
Examples of
accounts provided by gmail account
·
Google plus
·
Google drive
·
Google photos
·
Blogger
·
Google+ (plus)
How to use Google+?
·
Go to the Google+ home
page
·
Sign in if you have already have a Gmail
account
·
after sign in enter
your name and select a profile picture to get started with Google+
·
Now you can use a
Google+
How to use Google drive
ü
Go to drive.google.com
ü
Sign in into Google
drive by using Gmail account
ü
Sign in now you can upload or create files.
YAHOO
ACCOUNTS
Steps on
how to create Yahoo account
b.
Click on Mailat the
top left corner of the page.
c.
Create Account, to set up your new
account by filling your particular information
d.
Choose the username of
your yahoo account.
What
is Carbon Copy (CC), Blind Carbon Copy (BCC), Sign in and Sign up as applied in
emails? Using Gmail account explain practically how to attach different types
of files while sending emails. What the maximum data size that can be attached
and sent using Gmail?
igning
In is the process of logging into the
E-mail account. And SIGN UP means opening new account in E-mail. They are done
when a person needs to access an email account and also need to create a new
account.
Electronic
mail, or email, is a method of exchanging digital messages between people using
digital devices such as computers, mobile phones and other electronics. Email
operates across computer networks, which today is primarily the internet. Some
early email systems required the author and the recipient to both be online at
the same time, in common with massaging. Today's email systems are based on a
store-and-forward model. Email servers accept, forward, deliver, and store
messages. Neither the users nor their computers are required to be online
simultaneously. Internet email messages consist of two major sections, the
message header and the message body, collectively known as content. The header
is structured into fields such as To, CC, BCC, Subject, Date, and other
information about the email. The body contains the message, as unstructured
text, sometimes containing a signature block at the end. The header is separated
from the body by a blank line.
Common
header fields for email include;
TO…
CC…
BCC…
SUBJECT…
To:
The email addresses (es), and optionally name(s) of the message's recipient(s).
Indicates primary recipients (multiple allowed), Cc stands for "carbon
copy." Anyone you add to the cc: field of a message receives a copy of
that message when you send it. All other recipients of that message can see
that person you designated as a cc: recipient. To add an entry in the cc:
field, click the Add cc: link under the To: field. Bcc: stands for "blind
carbon copy." Anyone you add to the bcc: field of a message receives a
copy of that message when you send it. But, bcc: recipients are invisible to
all the other recipients of the message including other bcc: recipients. To add
an entry in the bcc: field, click the Add bcc: link under the To: field.
Email
body The email body is the main part of an email message. It contains the
message’s text, images and other data (such as attachments).
Attachments
An email attachment is a computer file sent along with an email message. One or
more files can be attached to any email message, and be sent along with it to
the recipient. Think! What does the attachment icon look in e-mail programs?
All e-mail programs and services are different. However, the standard for the
attachment icon is a paper clip icon. Below is a picture of the attach files
icon in Google Gmail.
When
referring to e-mail, an attachment is a file sent with an e-mail message. An
attachment can be a picture, a word document, a movie, a sound file, an Excel
document or any other file that requires another program to open it. Attachment
is added just by clicking t he attachment icon. By clicking the icon the files
in your computer will be open and allow you to search for the file you need to
attach then double click it or right click and select to attach it.
Explain
practically how can you use your laptop computer for video calling and
conferencing? What are the software requirement(s) for video calling and/or conferencing?
IDEO
CALL; is the audio and video communication process which uses a live internet
connection between people in different locations. That communication including
people such as : A. Family B. Friends
VIDEO
CONFERENCING; is alive visual connection between two or more people residing in
separate location for purpose of communication.
Requirement
for video call and conferencing:
• Video input; web camera or video
camera.
• Audio input; microphone.
• Audio output; loudspeaker associated
with display device.
Software
used on video call and conferencing are Skype, Google hangout, viber, imo,
facebook messenger, i chat (macbook), tango.
Skype
is software that enables the world's conversations. Millions of individuals and
businesses use Skype to make free video and voice one-to-one and group calls, send
instant messages and share files with other people on Skype. You can use Skype
on whatever works best for you – on your mobile, computer or tablet. Skype is
free to download and easy to use.
Try
Skype today and start adding your friends, family and colleagues. They will not
be hard to find; hundreds of millions of people are already using Skype to do
all sorts of things together and get communicate easily and pass the needed
information.
By
using multimedia teaching materials describe communication satellites and its
types.
attilate is an
artificial body placed in orbit around the earth or moon or other planet in
order to collect the information for communication.
A
satellite is a solid object which revolves around some body due to the effect
of Gravitation force. Satellites are classified into different type based on
the purpose and size. The various types of satellite include; weather
satellite, communication satellite, navigation satellite, earth observation
satellite, astronomical satellite, miniaturized satellite.
In
this work by using multimedia teaching materials, the communication satellites
and its types are discussed in detailed.
Communication
satellites: The communication satellite is a satellite that transmits the
signals such as telephone, television, radio, internet signals over long
distances.
In
satellite communication, signal transferring between the sender and receiver is
done with the help of satellite. In this process, the signal which is basically
a beam of modulated microwaves is sent towards the satellite. Then the
satellite amplifies the signal and sent it back to the receiver’s antenna
present on the earth’s surface. So, all the signal transferring is happening in
space. Thus this type of communication is known as space communication.
Also
satellite communication is the method of transporting information from one
place to another using the communication satellite in orbit around the earth.
Example, Watching the English premier league every weekend with your friends
would have been impossible without it.
Electrical
signal is used to transmit the information through the wire. However,
electrical signal or electric current is not transmitted wirelessly because air
is a pure insulator. Hence, it resists the flow of electric current or
electrical signal.
Types
of communication satellites
1.
Passive satellites.
2.
Active satellites.
Passive
satellites receive the electromagnetic signal from the source or transmitter
and redirect it towards the receiver or destination; They are relay stations in
space. For example if you put a hydrogen
balloon which has a metallic coating over it, in the air it is technically
becomes a passive satellite.
It
is divided into two types (Natural satellite and artificial satellite). A moon
is natural satellite of earth. The electromagnetic signal transmitted from the
source collides continuously with the atmospheric particles. Because of this
continuous collision, the signal strength is reduced. Hence, the receiver will
receive a weak signal.
Advantageous
of Passive satellite,
a)
Low cost
b)
Work as a reflector
Disadvantageous
of Passive satellite,
i)
The large attenuation of signals.
ii)
Earth stations require high power (10kw)
to transmit the signals.
iii)
Large Earth station with tracking
facilities was expensive.
iv)
Require a large number of satellites
accessed randomly by different users.
v)
Control of satellite not possible from
ground.
An
active satellite is a satellite that receives the signal from the source,
amplifies the signal, and redirects the signal towards the receiver. Have
Transponder that provide the action to incoming signal and prevent the
interference between two signals. Amplify or modify and retransmitted the
signal from the earth. Are satellites which can transmit powe.
These
amplified signals are stored in the memory of the satellites, when earth
properly faces the satellite. Then the satellite starts sending the signals to
earth. Some active satellites also have programming and recording
features. Then these recording can be
easily played and watched. Their amplification is done by the receivers
themselves (AndersonP.et al(2007).
Advantageous
of Active satellite,
Ø Require
lower power earth station.
Ø Not
open to random use.
Ø Directly
controlled by operator from the ground.
Disadvantageous
of Active satellite,
v More
expensive because use electronic devices.
v Require
skilled person.
Differentiate
between cloud storage facilities and cloud backup facilities. Practically show
how to use one selected cloud storage and backup facility.
loud
backup or online backup is designed to make a copy of the files you store on
your computer and save this copy on a secure online server. In the event that
your laptop is stolen, destroyed, crashes or gets damaged in any other way that
leads to the loss or corruption of your original data, you’ll only need to
download the software client of the online backup service to your computer, and
restore your backed up data to your new computer. These restored files will be
the same as your original computer-stored files.
Apart
from this backup automation feature, these services also offer what’s called a
continuous backup, that is, every edit or change you make to your files gets automatically
backed up as well. Online backup services will offer file restoring and file
versioning too. If you edit a file that you shouldn’t have, you can go back a
number of previous versions of the file. Similarly, if you accidentally delete
a file from your computer, you can restore this file within a certain period.
Other features may include mirror image backup offered by Carbonate or remote
wipe feature offered by Sugar Sync that lets you wipe out data synced to a
computer that is subsequently lost or stolen.
With
cloud storage services you have to manually select the files you want to upload
to the cloud and synced to all of your other devices. If you delete a file or
somehow the file gets corrupted, this file can no longer be retrieved (again,
the flash drive analogy is quite illustrative!).
With
an online storage you can access your files directly in your sync folder a
feature typical for Drop box and One Drive, or you can access them online
through the host site
As
a person may have already concluded from reading all of the above, the main
difference between a cloud storage and a cloud backup is their purpose or
finality – cloud backups are meant for automatically and continuously keeping
all of your files safe, while cloud storage solutions are primarily used for
storing a number of files always defined by the user, and as a collaborative
tool via their excellent sharing capabilities.
Apart
from this main and crucial distinction, the following differences also apply:
- Automatic
versus manual saving of data – cloud backup services like Just Cloud work
automatically, that is, they automatically save and sync all your files
that are stored on your computer. Cloud storage services like Drop box
only save and sync the files that you’ve manually added to your sync
folder;
- Security
– cloud backup services are very serious about security, thus, they
encrypt files both on transfer and on storage with the latest in
encryption technologies (256-bit AES encryption, TSL), and some services
like Carbonate will even allow you to manage your own encryption key. This
level of security makes sharing and collaboration features much more
limited and file preview features much more tedious (files have to be
decrypted before you can view them) than in the case of cloud storage
services that usually only encrypt files on their servers without locally
encrypting them on your computer;
- Redundancy
– online storage services don’t offer the same file redundancy offered by
online backups. If a file is deleted or overwritten, the change will
appear on all synced devices usually without the possibility to restore
previous versions of a file or restore the backup of a file. An online
backup service will retain several versions of a file and allow you to
recover even deleted files. This file versioning and deleted file recovery
feature may be available at some cloud storage providers as well (e.g.
Drop box), but only in higher tier plans or only as an add-on service,
while online backups contain these feature as a core element of their
service.
Procedures
for opening and storing data in cloud storage facilities
a) Searching
a sample cloud storage facility using search engine.
b) Sign
in if you do not have an account and log in if you have an account.
c) To
add any data to drop box go to file then upload file.
d) It will come note asking you choose a file from your
device.
e) After
clicking CHOOSE FILE then you has choose file you want to store in drop box.
