4. DATA COMMUNICATION:
DEFINITION
Data Communication has two types :
1. Local -Local communication takes place when the
communicating devices are in the same
geographical area, same building, face-to-face
between individuals etc
2. Remote-Remote communication takes place over
a distance i.e. the devices are further 4
Transfer of data from one device to another via
some form of transmission medium.
Transfer of data from one device to another via
some form of transmission medium.
5. EFFECTIVENESS OF A DATA
COMMUNICATION CAN BE MEASURED
THROUGH THE FOLLOWING FEATURES
Delivery : Delivery should be done to the correct
destination.
Timeliness : Delivery should be on time.
Accuracy : Data delivered should be accurate.
Jitter : Variation in packet arrival.
6. DATA REPRESENTATION
Numbers
8/16/32 bit integers
floating point
Text
ASCII, Unicode
Images
Bit patterns, Graphics formats JPG/GIF/etc
Audio → Samples of continuous signal
Video → Sequence of bitmap images
6
7. PROTOCOLS
Protocol
A set of rules governing data communications
Syntax
Structure or format of the data
Semantics
Interprets the meaning of the bits
Knows which fields define what action
Timing
When data should be sent and what
Speed at which data should be sent or speed at which it is
being received.
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8. DIRECTION OF DATA FLOW
Simplex: One direction only
8
Server Monitor
data flow
Keyboard
data flow
9. DIRECTION OF DATA FLOW
Half Duplex: Both directions, one at a
time
E.g., walkie-talkies
9
data flow at time 1
data flow at time 2
10. DIRECTION OF DATA FLOW
Full Duplex: Both directions simultaneously
E.g., telephone
Can be emulated on a single communication
link using various methods
10
data flow
data flow
12. NETWORK
Topics discussed in this section:Topics discussed in this section:
Définitions
Network Criteria
Physical Structures
Categories of Networks
13. NETWORK DEFINITION
AA networknetwork is a set of devices (often referred to asis a set of devices (often referred to as nodesnodes))
connected by communicationconnected by communication linkslinks..
A node can be a computer, printer, or any other deviceA node can be a computer, printer, or any other device
capable of sending and/or receiving data generated bycapable of sending and/or receiving data generated by
other nodes on the network.other nodes on the network.
A link can be a cable, air, optical fiber, or any mediumA link can be a cable, air, optical fiber, or any medium
which can transport a signal carrying information.which can transport a signal carrying information.
14. PURPOSE
The purpose of a network is to share resources.
A resource may be:
A file
A folder
A printer
A disk drive
Or just about anything else that exists on a
computer.
15. NETWORK CRITERIA
A network must be able to meet certain criteria, these are mentioned below:
Performance
Reliability
Scalability
Performance :
It can be measured in following ways :
Transit time : It is the time taken to travel a message from one device to
another.
Response time : It is defined as the time elapsed between enquiry and
response.
Other ways to measure performance are :
Efficiency of software
Number of users
Capability of connected hardware
16. CONTD..
Reliability
It decides the frequency at which network failure
take place. More the failures are, less is the
network's reliability.
Security
It refers to the protection of data from the
unauthorized user or access. While travelling
through network, data passes many layers of
network, and data can be traced if attempted. Hence
security is also a very important characteristic for
Networks.
17. PROPERTIES OF GOOD NETWORK
Interpersonal Communication : We can
communicate with each other efficiently and
easily example emails, chat rooms, video
conferencing etc.
Resources can be shared : We can use the
resources provided by network such as printers
etc.
Sharing files, data : Authorized users are
allowed to share the files on the network.
18. TYPES OF CONNECTIONS
Point-to-point-Dedicated link
Multipoint (Timeshared)-Shares a single link
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21. ADVANTAGES OF NETWORKING
Connectivity and Communication
Data Sharing
Hardware Sharing
Internet Access
Internet Access Sharing
Data Security and Management
Entertainment
22. THE DISADVANTAGES (COSTS) OF
NETWORKING
Network Hardware, Software and
Setup Costs
Hardware and Software Management
and Administration Costs
Undesirable Sharing
Illegal or Undesirable Behavior
Data Security Concerns
23. NETWORK CATEGORIES
Local Area Network (LAN)
Wide Area Network (WAN)
Metropolitan Area Network (MAN)
23
24. LOCAL AREA NETWORKS
A local area network (LAN) is a computer
network covering a small geographic area, like a
home, office, or group of buildings
24
25. WIDE AREA NETWORKS
Network providing long-distance
communication over a country, a
continent, or the whole world
Two or more LANs connected together
The Internet is an example
25
27. NETWORK TERMS- HOST,
WORKSTATIONS, SERVER, CLIENT,
NODE
Host:
A network host is a computer or other device
connected to a computer network. A network host
may offer information resources, services, and
applications to users or other nodes on the network. A
network host is a network node that is assigned
a network layer host address
Workstations:
A workstation is a special computer designed for
technical or scientific applications. Intended primarily
to be used by one person at a time, they are commonly
connected to a local area network and run multi-user
operating systems.
28. CONTD..
Server :
computer is a core component of the network,
providing a link to the resources necessary to perform
any task.
Client :
computers normally request and receive
information over the network client. Client computers
also depends primarily on the central server for
processing activities
