NETWORKING AND DATA COMMUNICATION STUDY NOTES
CONTENTS
a. Computer network
b. Data communication
c. Types of computer networks
d. Components of networking
Definition of terms used in Networking
Network
A Network can be defined as a collection of independent entities that are arranged in such a
manner as to exchange data, information or resources.
Computer Network
A computer network can be defined as a collection 2 or more computers connected together
using transmission media (e.g., cables, or Satellites) for the purpose of communication and
sharing of resources.
Apart from computers, other devices such as Printers, plotters, fax machines, modems, etc
can also be connected to the network.
The term Transmission media refers to any physical or non-physical link between 2 or more
computers, and in which a signal can be made to flow from source to destination.
Network Server.
A Server is a powerful computer that provides services (shared resources) to the other
computers on the network. It enables information, resources & network devices to be shared
by users on a computer network.
Network servers;
i). Have a higher hard disk & main memory (RAM) capacity than the other computers on
the network.
ii). Store & run a special program called the server software (network operating system),
which controls computers on the network.
Clients (workstations)
Clients (also referred to as Workstations) are standalone Computers attached to the network,
on which the network users do their work. They are used by network users to send their
requests to the server.
Clients;
i). Are usually less powerful than the server, and use the resources provided by the Server.
ii). Have their own operating systems and files.
The figure below shows a server on a network.
COMPUTER NETWORKING NOTES PREPARED BY MR. ANTONY AMBIA Page 1
,DATA COMMUNICATION
Data communication refers to the process of transmitting data signal from one place to
another through a communication media.
The basic components of a data transmission system are:
(a) A central computer (server).
(b) Terminal devices (clients, printers etc)
(c) Telecommunications link between the central computer & the terminal devices.
Terms used in data communication
Data signal:
A data signal is a voltage level in the circuit which represents the flow of data.
In data communication, there are 2 types of data signals; Digital and Analog.
Analog data is made up of continuous waveforms, while digital data is made up of a non-
continuous discrete waveform.
Signal modulation and demodulation:
This is the process of converting data signals to a form that can be transmitted over a
transmission medium .e.g., a modem converts a digital signal to an analog signal, which can
be transmitted over analog telephone lines. This process is called modulation. A modem at
the receiving end converts the analog signal into a digital signal, a process known as
demodulation.
Multiplexing and Demultiplexing:
Multiplexing is the process of sending multiple data signals over the same medium, e.g., a
wire conductor can be made to carry several data signals either simultaneously or at different
times.
Demultiplexing is the process of separating the multiplexed signals at the receiving end.
The different data signals have different frequencies on the cable; hence, they do not
interfere with one another.
Demultiplex
Multiplexer
Multiplexed line
From computers To computers
er
Fig.: A multiplexed link
Bandwidth:
COMPUTER NETWORKING NOTES PREPARED BY MR. ANTONY AMBIA Page 2
, A Bandwidth is the maximum amount of data that a transmission medium can carry at any
one time. E.g., a certain cable may have a bandwidth of 100 Mbps (Mega bits per second).
Attenuation:
Attenuation is the decrease in magnitude and energy of a signal as it progressively moves
along a transmission medium.
If the signal is not boosted, it will totally be lost along the way, and may never reach the
destination.
Attenuation (or signal loss) is usually corrected by placing signal amplifiers (also called
repeater stations) along the medium at appropriate distances in order to receive the weak
signal, clean it, amplify it, then retransmit it.
Modes of data communication
There are 3 modes of data communication:
(a). Simplex.
(b). Half duplex.
(c). Full duplex.
Simplex transmission:
This is where communication is only in one direction (as in radio or television broadcast).
The listener or viewer cannot communicate back through the radio or television receiver
back to the broadcaster.
Half duplex transmission:
This refers to communication in both directions, but one direction at a time.
A sender must first send the data before the recipient can reply.
Full duplex transmission:
This is where communication occurs in both directions simultaneously (as in computers that
are sending & receiving data on a network).
Factors to consider when selecting a data transmission system
1. Cost of each type of data transmission method.
2. Distance between the computer & the terminal.
3. Volume of data to be processed; and whether it is batched at particular times, or whether
it is collected individually and required to be processed immediately.
4. Speed of transmission required.
5. Accuracy and reliability required.
PURPOSE AND LIMITATIONS OF NETWORKING
PURPOSE OF NETWORKING
i. Resource sharing – Different computers are connected to each other hence a user at one
site may be able to use the resource available at another site e.g. printer, internet.
ii. Remote communication – This involves the transmission of data signals between two
communication devices located at different geographical locations. Through remote
communication people can be able to share ideas and pass messages over the network.
iii. Distributed processing – If a particular process can be subdivided into several sub-
processes then each sub-process can be processed at different sites concurrently hence
speeding up the entire process.
COMPUTER NETWORKING NOTES PREPARED BY MR. ANTONY AMBIA Page 3
CONTENTS
a. Computer network
b. Data communication
c. Types of computer networks
d. Components of networking
Definition of terms used in Networking
Network
A Network can be defined as a collection of independent entities that are arranged in such a
manner as to exchange data, information or resources.
Computer Network
A computer network can be defined as a collection 2 or more computers connected together
using transmission media (e.g., cables, or Satellites) for the purpose of communication and
sharing of resources.
Apart from computers, other devices such as Printers, plotters, fax machines, modems, etc
can also be connected to the network.
The term Transmission media refers to any physical or non-physical link between 2 or more
computers, and in which a signal can be made to flow from source to destination.
Network Server.
A Server is a powerful computer that provides services (shared resources) to the other
computers on the network. It enables information, resources & network devices to be shared
by users on a computer network.
Network servers;
i). Have a higher hard disk & main memory (RAM) capacity than the other computers on
the network.
ii). Store & run a special program called the server software (network operating system),
which controls computers on the network.
Clients (workstations)
Clients (also referred to as Workstations) are standalone Computers attached to the network,
on which the network users do their work. They are used by network users to send their
requests to the server.
Clients;
i). Are usually less powerful than the server, and use the resources provided by the Server.
ii). Have their own operating systems and files.
The figure below shows a server on a network.
COMPUTER NETWORKING NOTES PREPARED BY MR. ANTONY AMBIA Page 1
,DATA COMMUNICATION
Data communication refers to the process of transmitting data signal from one place to
another through a communication media.
The basic components of a data transmission system are:
(a) A central computer (server).
(b) Terminal devices (clients, printers etc)
(c) Telecommunications link between the central computer & the terminal devices.
Terms used in data communication
Data signal:
A data signal is a voltage level in the circuit which represents the flow of data.
In data communication, there are 2 types of data signals; Digital and Analog.
Analog data is made up of continuous waveforms, while digital data is made up of a non-
continuous discrete waveform.
Signal modulation and demodulation:
This is the process of converting data signals to a form that can be transmitted over a
transmission medium .e.g., a modem converts a digital signal to an analog signal, which can
be transmitted over analog telephone lines. This process is called modulation. A modem at
the receiving end converts the analog signal into a digital signal, a process known as
demodulation.
Multiplexing and Demultiplexing:
Multiplexing is the process of sending multiple data signals over the same medium, e.g., a
wire conductor can be made to carry several data signals either simultaneously or at different
times.
Demultiplexing is the process of separating the multiplexed signals at the receiving end.
The different data signals have different frequencies on the cable; hence, they do not
interfere with one another.
Demultiplex
Multiplexer
Multiplexed line
From computers To computers
er
Fig.: A multiplexed link
Bandwidth:
COMPUTER NETWORKING NOTES PREPARED BY MR. ANTONY AMBIA Page 2
, A Bandwidth is the maximum amount of data that a transmission medium can carry at any
one time. E.g., a certain cable may have a bandwidth of 100 Mbps (Mega bits per second).
Attenuation:
Attenuation is the decrease in magnitude and energy of a signal as it progressively moves
along a transmission medium.
If the signal is not boosted, it will totally be lost along the way, and may never reach the
destination.
Attenuation (or signal loss) is usually corrected by placing signal amplifiers (also called
repeater stations) along the medium at appropriate distances in order to receive the weak
signal, clean it, amplify it, then retransmit it.
Modes of data communication
There are 3 modes of data communication:
(a). Simplex.
(b). Half duplex.
(c). Full duplex.
Simplex transmission:
This is where communication is only in one direction (as in radio or television broadcast).
The listener or viewer cannot communicate back through the radio or television receiver
back to the broadcaster.
Half duplex transmission:
This refers to communication in both directions, but one direction at a time.
A sender must first send the data before the recipient can reply.
Full duplex transmission:
This is where communication occurs in both directions simultaneously (as in computers that
are sending & receiving data on a network).
Factors to consider when selecting a data transmission system
1. Cost of each type of data transmission method.
2. Distance between the computer & the terminal.
3. Volume of data to be processed; and whether it is batched at particular times, or whether
it is collected individually and required to be processed immediately.
4. Speed of transmission required.
5. Accuracy and reliability required.
PURPOSE AND LIMITATIONS OF NETWORKING
PURPOSE OF NETWORKING
i. Resource sharing – Different computers are connected to each other hence a user at one
site may be able to use the resource available at another site e.g. printer, internet.
ii. Remote communication – This involves the transmission of data signals between two
communication devices located at different geographical locations. Through remote
communication people can be able to share ideas and pass messages over the network.
iii. Distributed processing – If a particular process can be subdivided into several sub-
processes then each sub-process can be processed at different sites concurrently hence
speeding up the entire process.
COMPUTER NETWORKING NOTES PREPARED BY MR. ANTONY AMBIA Page 3
