This document discusses data communication and computer networks. It defines data communication, computer networks, and their key components. The five components of data communication are the message, sender, receiver, transmission medium, and protocols. Data can flow between devices in simplex, half-duplex, or full-duplex mode. Important network criteria include performance, reliability, and security. Networks can connect devices via either point-to-point or multipoint connections, with the difference being that point-to-point provides a dedicated link between two devices while multipoint allows more than two devices to share a single link.

1. Data Communication and
Computer Network
Chapter 1: Introduction
Presented by: Abdalle M. Geele
abdallegeele@gmail.com

2. Objectives
At the end of this chapter, the learner
should know the concepts of:
 Data communication
 Computer network
 The components of data
communication
 The data flow
 The fundamental characteristics of DC
 Network criteria and network
connections

3. What is Computer Networking
 A computer Network is a system that
connects numerous independent
computers in order to share
resources.
 The integration of computers and
other different devices allows users to
communicate more easily
 A computer network consists of
various kinds of nodes, servers and
networking devices.

4. 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.

5. 5/15
Five components of data communication

6. 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
6/15

7. 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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8. 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:

9. 9/15
Data flow (simplex, half-duplex, and full-duplex)

10. 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.

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

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

13. 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.

14. 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.

15. 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.

16. 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

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

18. Types of connections: point-to-point and multipoint

19. 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.

20. Any Question??

21. Thanks