This document discusses different network topologies and modes of data communication. There are three main modes of communication: simplex (unidirectional), half duplex (bidirectional but not simultaneous), and full duplex (simultaneous bidirectional). The four basic network topologies covered are bus, star, ring, and mesh. A bus topology connects all devices to a single cable backbone. A star topology connects each device to a central hub/switch. A ring topology connects each device in a continuous loop, passing signals in one direction. A mesh topology connects each device to every other device through dedicated links, providing redundancy if one link fails.

1. Networking
Chap:02
Topologies

2. 1.2
1.3 Data Flow (Modes of Communication)1.3 Data Flow (Modes of Communication)
•Simplex:Simplex: in simplex mode communication isin simplex mode communication is
unidirectional. Only one device on a linkunidirectional. Only one device on a link
can send the data. The other device willcan send the data. The other device will
only receive the data. E.g Keyboard &only receive the data. E.g Keyboard &
MonitorMonitor
•Half Duplex:Half Duplex: in this mode both sender and receiverin this mode both sender and receiver
can send and receive, but not at the samecan send and receive, but not at the same
time. At a time one is sender the other acttime. At a time one is sender the other act
as receiver. E.g Walki-talkiesas receiver. E.g Walki-talkies

3. 1.3
Conti...Conti...
•Full Duplex:Full Duplex: in this mode both sender andin this mode both sender and
receiver can send and receive at thereceiver can send and receive at the
same time. E.g telephonesame time. E.g telephone

4. 1.4
Topology:Topology:
•The Physical structure of the network is known as
Topology.
•The Physical layout of the links and devices is called
topology.

5. 1.5
Figure 1.4 Four basic Categories of topology

6. 1.6
Bus Topology:Bus Topology:
•All devices are directly connected to a single main
cable
•Main cable act as the backbone for the network
•Computer are connected with the main cable via
local loop/drop line
•Only one device can send the data at a time
•Otherwise collision will occur.
•Terminator are used at the end of the main cable
•Main cable is used either thick net/ thick net.

7. 1.7
Figure 1.7 A bus topology connecting three stations

8. 1.8
Bus Topology

9. 1.9
Advantages
Use of cable is economical
Media is inexpensive and easy to work with
System is simple and reliable .
Bus is easy to extend
Disadvantages of Bus Topology:
Network can slow down in heavy traffic
Problems are difficult to isolate
Cable break can affect many users

10. 1.10
Star Topology:Star Topology:
•In a star topology, each device/computers has
a direct point-to-point link only to a central
controller
•central controller is called a hub/switch
•The devices/computers are not directly linked
to one another.
•If one device wants to send data to
another, it sends the data to the controller,
•Controller then send the data to the other
connected Device/computers

11. 1.11
Figure 1.6 A star topology connecting four stations

12. 1.12
Star Topology

13. 1.13
Star Topology

14. Advantages of Star Topology
 Modifying system and adding new
computers is easy . Centralized
monitoring and management are possible
Failure of one computer does not affect
the rest of the network
Disadvantages of Star Topology :
 If the centralized point fails, the network
fails

15. 1.15
Ring Topology:Ring Topology:
•In a Ring topology, each device has a
dedicated point-to-point connection with only
the two devices on either side of it.
• A signal is passed in ring in one direction,
from device to device, until it reaches its
destination.
• token (frame) is circulating in the ring

16. 1.16
Ring Topology:Ring Topology:
•Each device wait for its number to send the
data
•At a time only one device can send the data
•Each device in the ring contain a repeater.
Note: Repeater is used to Re-generate the
weaken signals

17. 1.17
Figure 1.8 A ring topology connecting six stations

18. 1.18
Advantages of Ring Topology
System provides equal access for all computer
Performance is even despite many users
Disadvantages of Ring Topology:
Failure of one computer can impact the rest
of the network
Problems are hard to isolate.

19. 1.19
Ring Topology

20. 1.20
Mesh Topology:Mesh Topology:
•In a mesh topology, every device has a
dedicated point-to-point link to every
other device in the Network
•If a network contain ‘N’ number of computers
then each computer needs ‘N-1’ number of
Input/output ports
•The link between devices usually are Full
duplex
• very reliable topology (if one link goes down
then other line is available)

21. 1.21
Figure 1.5 A fully connected mesh topology (five devices)

22. 1.22
Mesh Topology

23. 1.23
•End of Chapter