chapter 2.pptx

Data Communications
 When we communicate, we are sharing
information. This sharing can be local or remote.
Between individuals, local communication usually
occurs face to face, while remote communication
takes place over distance
 The term telecommunication means
communication at a distance.
 The word data refers to information presented in
whatever form is agreed upon by the parties
creating and using the data.
 Data communications are the exchange of data
between two devices via some form of
transmission medium such as a wire cable.

Five components of data
communication
 Message :- is information to (Data) be
communicated
E.g. text, numbers, Audio, Video.
 Sender :- Device that sends the Data message
E.g. Computer , Work-station ,telephone
handset television and so on.
 Receiver:- Device that receive the message
E.g. Computer , Work-station ,telephone
handset television and so on.
 Transmission Medium :- Physical Path in which
the message travels from sender to Receiver.
E.g Twisted Pair, Coaxial Cable, Fiber Optics
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Five components of data
communication
Conti…
 Protocols:- Set of Rules that Govern the data
communication.
 Represent the agreement between
Communication.
 Without Protocol two Device can be connected but
not communicate each other
E.g. Just person speaks amharic can’t
understand a person speak Somali.
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Four Fundamental Characteristics
 Delivery :- the system must deliver data to the
correct destination.
 Accuracy:-the system must deliver the data
accurately.
 Timeliness:- The data must deliver data in a
timely manner, data delivery late are useless.
In case of video, and Audio, timely delivery
means delivering date as they produced – this
kind of delivering is known as Real-time transition.
 Jitter, refers the variation of the packets arrival
time
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The effectiveness of data communications
system depends four fundamental
characteristics:

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Data flow (simplex, half-duplex, and full-duplex)

Data Flow
 Communication between two devices can be
simplex, half duplex or full duplex
In Simplex mode, the communication is
unidirectional, as on a one-way. Only one of
the two devices on a link can transmit the
other can only receive
In half-duplex mode, each station can both
transmit and receive but not at the same
time.
When one device is sending, the other can
only receive and vice versa.
In full-duplex mode, both stations can
transmit and receive simultaneously.

 What are the network criteria that the
network must be able to meet?

Network Criteria
 A network must be able to meet a
certain number of criteria. The most
important of these are:
 performance
Reliability
Security

Performance
 Performance can be measured in many
ways including transit time and response
time.
 Transit time is the amount of time
required for a message to travel from
one device to another.
 Response time is the elapsed time
between an inquiry and a response.
 The performance of a network depends
on a number of factors including the
number of users, the type of
transmission medium, the capabilities of
the connection hardware and the
efficiency of the software.

Reliability
 In addition to accuracy of delivery,
network reliability is measured by the
frequency of failure, the time it takes a
link to recover from a failure.

Security
 Network security issues include
protecting data from unauthorized
access, protecting data from damage
and development, and implementing
policies and procedures for recovery
from data loss.

NETWORKS
• A network is a set of devices (often referred to as
nodes) connected by communication links. A
node can be a computer, printer, or any other
device capable of sending and/or receiving data
generated by other nodes on the network.
• For communication to occur, two devices must
be connected in some way to the same link at the
same time.
• There are two possible types of connections:
 Point-to-Point
 Multipoint

 What is the difference between Point-
to-Point and multipoint connections?

Types of connections: point-to-point and multipoint

Point-to-Point and Multipoint
 A Point-to-Point connection provides a
dedicated link between two devices.
 A multipoint connection is one in which
more than two specific devices share
a single link.

chapter 2.pptx

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