Data Communication and Computer Networks, LAN, WAN and MAN, Network topology- Star, Mesh, Bus and Ring, Simplex, Half- Duplex and Full Duplex, Types of connection- point-to-point and multi-point, types of transmission- unicast, multicast and broadcast

1. Unit 5
DATA
COMMUNICATION

7. What is Data Communication...??
Data refers to information presented in
whatever form is agreed upon by the parties
creating and using the data.
And
Telecommunication means Communication
at a distance.

8. So

9. Data communication is the
exchange of data between two
devices via some form of
transmission medium such as a wire
cable.

10. Characterstics of Data Communication
Delivery
Accuracy
Timeliness
Jitter

11. Components
Of
Data Communication

13. How does the
Communication
Takes Place….

14. Graham Betts

15. So,
This is how Data moves around…
--Data
Source (where the
data originates)
--Transmitter (device used
to transmit data)
--Transmission Medium
(cables or non cable)
--Receiver (device used to

16. Data Flow

17. Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)
1.17

18. 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. A link can be a cable, air, optical fiber, or any
medium which can transport a signal carrying
information.
1.18

19. Physical Structures
 Type of Connection
 Point to Point - single transmitter and receiver
 Multipoint - multiple recipients of single transmission
 Physical Topology
 Connection of devices
 Type of transmission - unicast, mulitcast, broadcast
1.19

20. Types of connections: point-to-point and multipoint
1.20

21. Categories of topology
1.21

22. A fully connected mesh topology (five devices)
--The mesh topology connects all devices (nodes) to each other for
redundancy and fault tolerance.
--It is used in WANs to interconnect LANs and for mission critical
networks like those used by banks and financial institutions.
--Implementing the mesh topology is expensive and difficult.
1.22

23. Advantages:
•Fault tolerance
•Guaranteed communication channel capacity
•Easy to troubleshoot
Disadvantages:
•Difficulty of installation and reconfiguration
•Cost of maintaining redundant link
1.23

24. A star topology connecting four stations
--All the cables run from the computers to a central location, where they are all connected by a device called a
hub. Each computer on a star network communicates with a central hub that resends the message either to all the
computers or only to the destination computers.
--Hub can be active or passive in the star network
----Active hub regenerates the electrical signal and sends it to all the computers connected to it.
----Passive hub does not amplify or regenerate signal and does not require electrical power to run.
--We can expand a star network by placing another star hub.
1.24

25. Advantages:
--Easy to modify and add new computers to a star net
--Center of a star net is a good place to diagnose network faults
--Single computer failure do not necessarily bring down the whole net
--Several cable types can be used with the hub
Disadvantages:
--Central hub fails, the whole network fails to operate
--Many star networks require a device at the central point to rebroadcast
or switch network traffic.
--Costs more for cabling in star net than bus.
1.25

26. A bus topology connecting three stations
--All the devices on a bus topology are connected by one single cable.
When one computer sends a signal up the wire, all the computers on the
network receive the information, but only one accepts the information.
The rest regrets the message.
--One computer can send a message at a time.
--A computer must wait until the bus is free before it can transmit.
1.26

27. Advantages
 The bus is simple, reliable in small network, easy to use
and understand
 Requires the least amount of cable to connect the
computers and less expensive
 Easy to extend the bus
Disadvantages
 Heavy network traffic can slow a bus considerably
 Each barrel connector weakens the electrical signal
 Difficult to troubleshoot a bus
1.27

28. A ring topology connecting four stations
--Each computer is connected to the next computer ,with the last one connected to the
first.
--Every computer is connected to the next computer in the ring, and each retransmits
what it receives from the previous computer.
--The message flow around the ring in one direction.
-- Some ring networks do token passing.
It passes around the ring until a computer wishes to send information to
another computer.
1.28

29. Advantages:
•No computer can monopolize the network
•The fair sharing of the network allows the net to degrade gracefully as more
user are added.
Disadvantages:
•Failure of one compute can affect the total network
•Difficult to troubleshoot
•Adding or removing Computers disrupts the network
1.29

30. Categories of Networks
 Local Area Networks (LANs)
 Short distances
 Designed to provide local interconnectivity
 Wide Area Networks (WANs)
 Long distances
 Provide connectivity over large areas
 Metropolitan Area Networks (MANs)
 Provide connectivity over areas such as a city, a campus
1.30

31. LAN
(Local Area Network)
A local area network (LAN) is
usually privately owned and links
the devices in asingle office,
building, or campus. Depending on
the needs of an organization and
the type of technology used.

32. 5

33. WAN
(Wide Area Network)
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.

35. MAN
(Metropolitan Area Network)
A metropolitan area network
(MAN) is designed to extend over an
entire city. It may be a single network
such as a cable television network,
or it may be a means of connecting a
number of LANs into a larger network
so that resources may be shared
LAN-to-LAN as well as device-todevice.