Data Communications and Networks

HNDIT1213
Data Communications and Networks

Definition
A network can be defined as two or more computers
connected together in such a way that they can share
information and resources.
Or
Two or more computers or communication devices
connected by transmission media and channels and
guided by a set of rules for communication purpose
that allows user to communicate with each other and
share information and resources

Definition (cont..)
A resource may be:
 A file
 A folder
 A printer
 A disk drive
 Or just about anything else that exists on a computer.

Advantages of networking
 Connectivity and Communication
 Data Sharing
 Hardware Sharing
 Internet Access
 Internet Access Sharing
 Data Security and Management
 Entertainment
 Sharing devices such as printers saves money.
 Files can easily be shared between users.
 Security is good - users cannot see other users' files unlike on stand-
alone machines.
 Data is easy to backup as all the data is stored on the file server.
 Etc…

Disadvantages of networking
 Network Hardware, Software and Setup Costs
 Hardware and Software Management and Administration Costs
 Data Security Concerns
 Managing a large network is complicated, requires training and a
network manager usually needs to be employed.
 If the file server breaks down the files on the file server become
inaccessible.
 Viruses can spread to other computers throughout a computer
network.
 There is a danger of hacking, particularly with wide area networks.
 Etc..

kinds of networks
Depending on one's perspective, classify networks in different
ways
 Based on the transmission media : Wired (UTP, Coaxial cables,
fiber-optic cables) and wireless
 Based on the Network Size: LAN,WAN and MAN
 Based on the management method: peer to peer,
Client/Server
 Based on the topology (Connectivity): Bus, Star, Ring

Types of Network(Based on the Network Size)
 Local Area Networks (LANs)
 Wide Area Networks (WANs)
 Metropolitan Area Network (MAN)
Types of
Networks

Local Area Networks (LANs)
 A local area network is usually privately owned and links the
devices in a single office, building, or campus
 LANs are designed to allow resources to be shared (i.e.,
printers or applications programs )between PCs or
workstations

Metropolitan Area Network (MAN)
 A metropolitan area network is designed to extend over an
entire city. It may be a single network
 In addition, it may be a means of connecting a number of
LANs into a larger network

Wide Area Network (WAN)
 A wide area network (WAN) provides long-distance
transmission of data, voice, image, and video information
over large geographical areas that may comprise a country,
a continent, or even the whole world.

Types of Network in LAN (Based on the management method)
 Peer-to-Peer Networks
A peer-to-peer (P2P)network is created when two or more PCs are
connected and share resources without going through a separate
server computer
 Client/Server Networks
A computer network in which one centralized, powerful computer
(called the server) is a hub to which many less powerful personal
computers or workstations (called clients) are connected.

Advantages of Peer-to-peer networking
 Easy set up
 Each connected computer can act as a server so no need
for a dedicated server
 Failure doesn’t affect all computers
 Less expense
 Less configuration and implementation time

Disadvantages of Peer-to-peer networking
 Easy access to any computer
 Security is only as strong as whatever security is in place
on each computer
 Backup has to be done on each computer
 No control of access to data as there is no server

 Central management – all of the resources of the network
are available from one server
 Easy configuration – Systems on the network are simple
to set up and can make troubleshooting easier
 Scalability – because of a centralized system, it can be
easy to add more resources & clients.
 Security – There are fewer security issues to deal with as
all of the information is stored on a server and it’s
primarily the server that has to worry about securing data
and setting permissions
Advantages of Client/Server networking

Disadvantages of Client/Server networking
 Server Faults – If there is a fault on the server all of the
clients would go down too
 Crashes – If the server cannot handle large amounts of
traffic due to too many concurrent log-ins or file transfers,
it can cause system crashes
 Cost – Initial start-up costs can be expensive and you’d
also have to have a systems administrator to configure
and oversee the network

Peer-to-Peer Networks Versus Client/Server
Client-Server Peer-Peer
Complex to set up Simple to set up
Requires technical expertise to
set up and maintain
Needs basic technical skills
Server present No server present, each computer is a
'peer' of the others
Centralized data and application
management
Each computer has its own data and
applications loaded
Uses a dedicated network
operating system
Uses standard operating system with
network capabilities
User access and authentication
is managed centrally
Fairly basic login authentication for
each user

Data Communication
The process of transferring data from one location to
another is called Data Communication.
Data formats – analog or digital
Data travels across the medium
Wired Medium
Wireless Medium

characteristics of data communication
The data communication system depends on 4 fundamental
characteristics:
 Delivery. The system must deliver data to the correct
destination
 Accuracy. The system must deliver data accurately
 Timeliness. The system must deliver data in a timely
manner
 Jitter: jitter refers to the variation in the packet arrival time.
It is the uneven delay in the delivery of packets.

Process/Components of a data communication
 Message : The message is the information to be communicated. It can
consist of text, number, pictures, sound, or video-or any combination of
these (multimedia).
 Sender /Transmitter: The sender is the device that sends the data
message. It can be a computer, workstation, telephone handset, video
camera, and so on.
 Receiver : The receiver is the device that receive the message
 Medium : The transmission medium is the physical path by which a
message travels from sender to receiver. It can consist of twisted par
wire, coaxial cable, laser, or radio wares (terrestrial or satellite
microwave).
 Protocol : A protocol is a set of rules that govern data communication.
It represents an agreement between the communicating devices

Encoder and Decoder
In communication systems, computers are used for senders
and receivers. A computer works with digital signals. The
communication channels usually use analog signals. The
encoder and decoder are used in communication systems to
convert signals from one from to another.
Encoder: The encoder is an electronic device. It receives data
from sender in the form of digital signals. It converts digital
signals into a form that can be transmitted through
transmission medium.
Decoder: The decoder is an electronic device. It receives data
from transmission medium. It converts encoded signals (i.e.
analog signals) into digital form.

Interference
 In data communications ,interference is anything
which modifies, or disrupts a signal as it travels along
a channel between a source and a receiver.
 Interference is any barrier to the data communication.

Basic Communication/transmission Modes
of Operation
There are three modes of transmission simplex, half
duplex, and full duplex.
Transmission mode describes the direction, of flow of
signal between two connected devices.

Simplex
 Simplex is one direction.
 a network cable or communications channel can only
send information in one direction; it's a “one-way
street”

half duplex
Technologies that employ half-duplex operation are
capable of sending information in both directions
between two nodes, but only one direction or the other
can be utilized at a time.

full duplex
Full-duplex data transmission means that data can be
transmitted in both directions on a signal carrier at the
same time.

BASIS FOR
COMPARISON
SIMPLEX HALF DUPLEX FULL DUPLEX
Direction of
Communication
Communication is
unidirectional.
Communication is two-
directional but, one at a
time.
Communication is two
directional and done
simultaneously.
Send/Receive A sender can send data but,
cannot receive.
A sender can send as well
as receive the data but
one at a time.
A sender can send as well as
receive the data
simultaneously.
Performance The half duplex and full
duplex yields better
performance than the
Simplex.
The full duplex mode
yields higher
performance than half
duplex.
Full duplex has better
performance as it doubles the
utilization of bandwidth.
Example Keyboard and monitor. Walkie-Talkies. Telephone.

Data Communication :Applications
 e-mail, Voice mail,
 File transfer, Document transfer,
 Fund Transfer, e-commerce,
 Software download
 Tele-shopping, Tele-medicine, Telecommuting
 Distance learning, Teleconferencing,
 Long distance telephone calls, Chat,
 Weather reports, Stock exchange information,News

Data Communications and Networks

More Related Content

What's hot (20)

Similar to Data Communications and Networks (20)

Recently uploaded (20)

Data Communications and Networks