Download Data Communication and Networking

Data Communication
and Networking
Week 2
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Data Com & Networks LLU by Bilal Ahmad
Introduction
Data Communication and Networking are
changing the way we do business.
In order to have best productivity decisions has to
be made quickly.
Decision makers love to have accurate
information at no time.
Why to wait for DHL or TCS or Pakistan Post
when mail can be delivered via Email.
Business today relies on computer networks and
internetworks.
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Data Com & Networks LLU by Bilal Ahmad
Introduction (Continued)
But before we ask how quickly we can have the
accessibility we need to find what are Networks, How
they Operate, What type of technologies are available
in the market, which design best fills which set of
needs.
Similar to the fact that computers has brought a
tremendous change for business, data communication
and networking is revolutionary.
Just imagine the internet connectivity, it was very slow
and expensive. Now we do have broadband with
optical cable.
Before a twisted cable was used and optical cable can
operate on speed of light.
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Data Com & Networks LLU by Bilal Ahmad
Overview
This lecture will address two issues and in the next
lecture remaining two issues will be discussed;
1. Data Communication
2. Networks
3. The Internet
4. Protocol and Standards
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First a broad definition of data communications,
then it will be defined “network as highway
where you can travel”. The internet will be
discussed as a network of networks, and finally
different protocols, standards and their
differences will be discussed.
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Data Com & Networks LLU by Bilal Ahmad
Data Communication
When we communicate, we are sharing
information.
The sharing can be local or remote.
Between individuals communication occurs face
to face
Remote communication takes place over distance.
If you take an example of Telecommunication it
includes Telephony, Telegraphy and Television.That
reflects communication at a distance. Tele is a
Greek Oriented word means ‘far’.
The word ‘data’ refers to information. Data can
be text, voice, multimedia etc.
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Data Com & Networks LLU by Bilal Ahmad
Data Communication (Continued)
Data communication means exchange of
information in the form of data between two
devices via some form of transmission media such
as a wired cable or air in case of wireless medium.
For Data Communications to occur, the
communicating devices must be a part of a
communication system made up of combination
of hardware (Physical Equipment ) and Software
(Programs).
The effectiveness of Data Communication
depends on four fundamental characteristics;
delivery, accuracy, timelines and jitter.
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Data Com & Networks LLU by Bilal Ahmad
Fundamental Characteristics to
determine the effectiveness
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3.
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Delivery:
Data must be delivered to the correct destination.
Accuracy:
The information should be received accurately. Data
if altered in transmission or left uncorrected are
unusable.
Timelines:
The data must reach on time. Just imagine not every
time you will be sending emails. If you are
transmitting a video and the message is not reached
on time, it will cause severe problems to your
transmission.
Data Com & Networks LLU by Bilal Ahmad
Fundamental Characteristics to
determine the effectiveness
4.
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Jitter:
Jitter refers to the variation in the packet arrival
time. It is the uneven delay in the delivery of
Audio or video Packets. For example lets assume
that you are having a video conference calls or
you are talking to someone using Skype. You will
observe some jitters on the video if delay has
been caused in the transmission. There are so
many factors that can cause delays. Slow
Network, Poor Cable infrastructure etc can
cause delays.
Data Com & Networks LLU by Bilal Ahmad
Components of Data Communication
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Data Com & Networks LLU by Bilal Ahmad
Components Explained
Message:
The message is the information in the form of
data to be communicated. Popular forms are text,
numbers, pictures, audio and video.
 Sender:
The device that sends the data is called a sender.
Example of senders can be computer, mobile
phones, video cameras etc.
 Receiver:
The Devices that receives the data is called a
receiver. Again receiver should be according to the
transmitter.
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Data Com & Networks LLU by Bilal Ahmad
Components Explained
Transmission Medium:
The Transmission medium is the physical path by which
a message can be conveyed. Message travels from the
sender to receiver. In case of mobile phones the device
is considered to be a transmitter and a receiver at the
same time. Examples of transmission media are
cables, twisted pair cables, network cables, fiber optic
cables, radio waves.
 Protocol:
A set of rules that governs to data communications. It
represents an agreement between the two devices.
Without protocol you may be able to connect two
devices but there will be no communications.
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Data Com & Networks LLU by Bilal Ahmad
Data Representation
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Information today comes in different forms such as;
Texts
Examples are 32 bit/ 64 bit etc.
Numbers
Example is ASCII
Images
Composed of Pixels
Audio
Video
Both Audio and Video are different from Text,
Numbers and Images. They are real time analog
signals which are converted to discrete values.
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Data Com & Networks LLU by Bilal Ahmad
Data Flow
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Data Com & Networks LLU by Bilal Ahmad
Networks
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A Network is a set of devices (often referred as
nodes) connected by communication links. A
node can be a computer, a printer, or any other
device capable of transmitting and receiving data
generated by other nodes.
Distributed Processing:
Most Networks use distributed processing. A task
is divided among multiple computers. Example of
a server that is used to manage different
computers. Remember we do have limited
resources and we need to achieve the best results.
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Data Com & Networks LLU by Bilal Ahmad
Criteria of a Network
A Network must be efficient and effective. The criteria
is;
1. Performance
2. Reliability
3. Security
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Here is a group activity for you. Consider four mobile
networks Ufone, Warid, Telenor and Mobilink. On the
basis of above criteria debate which is the best
network? And why it is the best network. Work in
groups of 2 or 3.
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Data Com & Networks LLU by Bilal Ahmad
Physical Structures
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Before discussing Networks we need to define
some network attributes.
A network is two or more devices connected
through Links.
A Link is a communication pathway that transfers
data from one device to another.
For simplicity consider a link as a line drawn
between a sender and receiver.
Two types of connection are point to point and
point to multipoint.
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Data Com & Networks LLU by Bilal Ahmad
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Data Com & Networks LLU by Bilal Ahmad
Topology
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Topology term is used for the Physical Topology it
refers to way how two or more devices in a
network are connected. The Physical topology is
very important. It depends on the available
resources.There are total 4 Topologies, they are;
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Data Com & Networks LLU by Bilal Ahmad
Mesh Topology
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If the communication is Duplex than we need
total links;
n (n - 1) / 2, How?
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Data Com & Networks LLU by Bilal Ahmad
Star Topology
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In Star topology, each device has a dedicated link
to the central controller.
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Data Com & Networks LLU by Bilal Ahmad
Bus Topology
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The preceding examples were point to point, the
Bus topology is multipoint. One long cable acts as
a backbone to other devices in a Network.
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Data Com & Networks LLU by Bilal Ahmad
Ring Topology
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Data Com & Networks LLU by Bilal Ahmad
Categories of Network
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Usually we discuss two types, Local Area Network
and Wide Area Network.
LAN’s are usually within a building.
Most common topologies are bus, star and ring.
Speeds are 100 or 1000 Mbps.
For Long distance communication we use WAN’s.
You know the Internet, I am sure.
Mobile Telephony and Internet are the Perfect
Examples of WAN.
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Data Com & Networks LLU by Bilal Ahmad
Protocols and Standards
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In Computer Networks, communication occurs
between entities in a different system. An entity is
capable of sending and receiving the information.
However two entities cannot simply send bit
streams to each other and expect to be
understood. For communication to occur there
must be a set of defined rules known as protocol.
Protocol defines what is communicated, how it is
communicated and when it is communicated.
Syntax refers to the structure and format,
semantics for the meaning and timing what data
should be send and how fast it should be send.
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Data Com & Networks LLU by Bilal Ahmad
Network Models
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A Network is a combination of Hardware and
software that sends Data from one location to
another.
In our daily life we do use the concepts of Layers.
Just consider an example of two friends who
communicate through postal mail.
You have sender, receiver and carrier. Just try to
draw a sketch in your mind, how will be the
process.
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Data Com & Networks LLU by Bilal Ahmad
Layered Tasks
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Data Com & Networks LLU by Bilal Ahmad
The OSI Model
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Established in 1947, The International Standard
Organization is a multinational body dedicated to
worldwide agreement on International Standards.
It is an open system interconnectivity.
You have been told that why we need to have an
open system standard?
OSI Model is a Layered framework for the design
of a Network systems that allows communication
between all types of computer systems.
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Data Com & Networks LLU by Bilal Ahmad
OSI Layers: 7 Layered Architecture
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Data Com & Networks LLU by Bilal Ahmad