Hello!
guys My name is Praveen Mishra, and I am a computer science student.
This is my second blog
here, and my first blog was about concepts of hacking, I expect that you have
enjoyed and learned from my previous blocks. Well! as you know that I am new in
blogging, so I request you to please leave comments after reading my block,
that how you feel after reading my blog and what improvement should i have to
make in my blogging, to make it more efficient for you all. Well this blog is
also related to that blog, because most of hacking is performed on networks,
yeah you get it right, I am going to describe concepts of networking
here. If you want to read my previous blog, you may go to http://praveenmishrahacking.blogspot.com
Why Network was discovered : Lets have a tour of old age,
when people was unknown of the language, then they invented a technique of
communication by signaling each other by hands. They just produce sounds of
huhhh hahhh... and give signals by hands. As you know that human mind is
very creative and develope mechanism at its own when it requires to solve
something, like you make your omelate on clothing iron.
Then humans invented
the language, and communication became easier. When they started talking to
each other, their mind pinched them to communicate with people who are far from
them, so they invented mail service. After that they thought about faster data
communication because mail service take more time to message transfer. When
computer evolved, the way was clear for faster communication, then after,
network got created and faster communication was possible now. Network is the
name for connection of two devices which use that connection to transfer data.
So you can say that network is medium for sending and receiving data.
Let’s talk about DATA COMMUNICATION now. Data communication is of
two types, local communication and remote communication. Local communication
is direct communication, like you talk face to face to anyone. Remote communication
consist data communication through networks like whatsapp chating, email
service etc.
Data
communication does not mean that we send data from our side and assume that on
other end, user will receive correct data, no its not good idea. Our data
communication must be effective. Effective data communication depends upon four
fundamental characteristic.
# DELIVERY: Message must be delivered at other
end, a delivery signal indicates that message is delivered properly.
#ACCURACY: Message must be accurate, means it
contain same data as we send from our side.
#TIMELINESS: Timeliness
tells us about message will arive at time.
#JITTER: Jitter
specifies the time interval in packets arrival, if we send packets at 30 ms
time interval and user receives it at 50 ms, then quality of data will be
affected.
Lets talk about
components of data communication. Components means what we are going to need to
transfer and receive data.
° MESSAGE
° SENDER
° RECEIVER
° TRANSMISSION MEDIUM
° PROTOCALL
Message can be
represented in various forms like text, image, audio, and video. Where text and
images can be presented ad set of bits but audio and video are continues
signals, which have to be converted in appropriate form before transmission.
Lets discuss about
every form of data representation in data communication. Brief description
about every format of data representation is here.
•TEXT FORMAT: Text format is represented as
series of bits(0s and 1s). Different sets of bit pattern is designed to represent
text symbols. Each set is called code and process of representing symbols as
bits is called coding. Today the prevelent coding system is called Unicode which use 32 bit to represent
symbols.
•IMAGE FORMAT: Images are also
represented as bit patterns. In the simplest form an image can be represented
as the matrix of pixels. Where each pixel is a small dot. A picture can be of
100 pixels or 10000 pixels, but in the second case resolution of the picture
will be much better. For representing a black and white image only 1 bit pattern
is enough to represent a pixel. 1for black and 0 for white. There are various
methods present to represent an color image, one of them is RGB, so called because every color is
made up of these three parent colors. Intensity of each pixel is measured and
bit pattern is assigned to it. Another method is called YCM in this method every color
consists part of yellow, cyan, and megenta.
• AUDIO: Audio refers to the recording or
broadcasting of sound or music. Audio is by nature different from text and
images. It is continuous not discrete. When we use microphone to convert sound
into electronic signals, it generates electronic signals. We will learn how to
convert these continuous signals to discrete and analog later.
• VIDEO: Video refers to recording or
broadcasting a picture or movie. Video can either be produced as continuous
entity or it can be combinations of images which are discrete entity, arranged
to convey the idea of motion.
Lets come to the DATA FLOW. Data flow describes how data is
transmitting on the network. On the networks data can flow in three ways, which
are described bellow.
•SINPLEX: Simplex means
data will flow to only one direction on the network. If two devices are connected
with simplex network then it means that one device can only send data to other
device and second device can only receive, no reverse order is possible.
•HALF DUPLEX: Half duplex
allow us both side transmission of data, but one direction at a time. At any
instance only one device can send and other device can only receive, but at
another movement transmission direction can be reversed. This type of
transmission can not transmit data to both sides at same time.
• FULL DUPLEX: Full duplex is
like two way street, transmission on both side is possible at the same time.
Like internet we are using at this time, at same time we download data and
sending our request to server.
There are mainly two
types of connections are present for data communication.
° Point to point
° Multipoint
Point to point connection
is only connected to two devices and data transfer occurs only between these
two devices. Like your bluetooth headphone connected with your cellphone.
Multipoint connection
means that one server can send data to various devices, best example for this
type of communication is Internet. In multi point communication there are more
than two devices are connected with each other for data transmission.
Various TOPOLOGIES are presented today for data trans
mission. Topology means structure of the networks. If many computers are
connected with a single server, and that server serves to all the computers and
the client computer only receives is called BUS topology.
Various types of
topologies are enlisted bellow.
• BUS TOPOLOGY
• STAR TOPOLOGY
• MESH TOPOLOGY
• RING TOPOLOGY
• HYBRID TOPOLOGY
You can draw these
topologies structures as their name suggests.
NETWORK MODELS: Various kinds
of networks are made up of different entities, so it gets very important to
create some common standards for all the networks.
The two best known standards are OSI(OPEN
SYSTEM INTERCONNECTIO) and INTERNET MODEL. OSI model defines a seven layer
network, and internet model defines a five layer network. About OSI and Network
models, i will give detailed description in my next blog.
Now its time to
discuss about categories of network, now a days when we talk about networks we
are just talking about two main categories of network. LAN and WAN, categories of
network depends upon size of networks. I am giving brief description about
various categories of network.
* LAN: LAN (local area networks) as
name suggests, is the network created for communication and resource sharing in
a local area. Currently LAN size is limited to few kilometers. LAN can be used
for connection inside a university, government department, a bank or in any
industry.
Ian present time LAN
have a capacity to transmit data on the rate of 100 mbps to 10000.
* WAN: WAN (wide area
network) work for a very wide range of data communication like for continents,
countries, we can say that wan works for whole world. We will talk much more
about WAN in my next blog on Internet.
*MAN: metropolitan
area network works for the range between LAN and WAN.
PROTOCOLLS AND
STANDARDS:
In computer networks,
communication occurs between entities in computer. Entity is anything capable
of sending and receiving information. However two entities cant just start to
send data to each other and expect that other entity to understand, that is not
possible both the entities have to be agreed upon some protocol.
Protocol is the set of
rules that govern data transmission.
The key elements of
protocol are SYNTAX, SEMANTICS and TIMING.
* SYNTAX: Syntax refers to structure of
format of data, meaning the order in which they are presented. For example, a simple
protocol expect the first 8 bit of data to be address of sender and the second
8 bit to be the address of the receiver, and the rest of the stream to be
message itself.
* SEMANTICS: Semantics refers to meaning of each
section of the bit. How a particular problem to be interpreted and what action
is to be taken based on interpretation.
* TIMING: The tem timing refers to two characteristic,
first is when data should be sent and second is how fast they can be sent.
STANDARDS: Standards are
agreed upon rules. Data communication standards fall into two categories, DE FACTO (means by fact or by
convention) and DE JURE (means by law) .
STANDARD CREATION ORGANIZATIONS
Standards are created
through the cooperation of standard creation committees, forums and government
regulatory agencies. Some of the standard creating committees are ISO, ANSI, and IEEE etc.
That was a brief
introduction about data communication and networking, In my next blog I am
going to Introduce you with Internet in detail. I will start from the
backbone server and come to the your entity which is connected to the internet.
So stay tuned and visit regularly on http://praveenmishrahacking.blogspot.com for more interesting technical
topics and enjoy easy learning.
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Have a great day! and All the best for
your future. :)
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