The document discusses three common network topologies: Bus topology uses a single cable with devices connected directly to it. If the backbone cable fails, the whole network fails. Ring topology forms a closed loop with devices connected along it. Data travels in one direction around the ring. If a device on the ring fails, those after it cannot communicate. Star topology connects all devices to a central hub. Data passes through the hub to travel between devices. If a device fails only it is affected, but if the hub fails the whole network fails.

1. CHAPTER 3: COMPUTER
NETWORKS AND
COMMUNICATIONS
Network Topology

2. Network Topology
 Network topology is the physical arrangement of
computers in a network. Common network
topologies include the bus, ring and star .
nodes
nodes
nodes

3. I) Bus Topology
 A bus network consists of a single central cable, to which all computers and
other devices connect. The bus physical cable that connects the computer
and other devices.
 The bus in a bus network transmits data, instruction and information in both
directions.
 When sending device transmits data, the address of the receiving device is
included with the transmission so the data is routed to the appropriate
receiving device.
 Bus networks are and popular on LANs because they are inexpensive and
easy to install.
 One advantage of the bus network is that computers and other device can
be attached and detached at any point on the bus without disturbing the
rest of the computer.

4. If one node fail, the bus
network would still function as
long as the backbone is
working

5. Advantages Disadvantages
a) easy to implement and extend Limited cable length and
b) Cost effective as only a single number of stations
cable is used n If there is a problem with the
c) Cable faults are easily cable, the entire network goes
identified down
e Maintenance costs may be
higher in the long run.
n Performance degrades as
additional computers are
added or on heavy traffic
y Proper termination is required
(loop must be in closed path)

6. II) Ring Topology
 On a ring network, a cable forms a closed loop (ring) with all computers
and device arranged a long the ring.
 Data transmitted on the ring networks travel from device to device around
entire ring, in one direction.
 When a computer or device send data, the data travels to each computer
on the ring until it reaches its destination.
 If computer or device on a ring network fails, all devices before the failed
device are unaffected, but those after the failed device cannot function.
 A ring network can span a larger distance than a bus network, but it is
more difficult to install.
 The ring topology primarily is used for LANs but also is used in WANs.

7. If one of the nodes fails,
the network will fail to
function.

8. Advantages Disadvantages
a) A physical ring topology has a) If any nodes goes down, the
minimal cable requirement entire ring goes down.
b) No wiring center or closet b) Troubleshooting is difficult
needed because communication is only
c) The message can be one way.
automatically acknowledge c) There will be a limit on the
d) No collision exist between distance between nodes.
nodes.

9. III) Star Topology
 All of the computers device (node) on the network connect to the central
device, thus forming a star.
 The central device that provides a common connection point for nodes on
the network is called the hub.
 All data that transfer from one node to another passes through the hub, in
both direction.
 Similar to a bus network, star networks are fairly easy to install and
maintain.
 Nodes can be added to and removed from the network.
 In one node fails, one that node affected.
 If the hub fails, the entire network inoperable until the hub is repaired.
 A star network generally requires more cable

10.  If one nodes fails, the star
network can still function as long
as the host is working.
 If the host fails, the network will
fail to function.

11. Advantages Disadvantages
a) Easy to install and wire i Failure of the central hub
b) No disruption to the network causes the whole network
then connecting or removing failure
devices It is slightly more expensive
c) Easy to detect faults and to than using bus topology
remove parts o Requires more cable
d) More suited for larger
networks
e) Easy to expand network
f) Easy to troubleshoot because
problem usually isolates itself

12. Differentiate between the three
types of Network Topology
TOPOLOGY BUS RING STAR
Configuration
Central Device Not available Not available Hub or switch
Data Transmitted Both direction One direction Both direction
Installation and Easy Difficult Easy
Maintenance
If one node fails Does not effect the The entire network Does not effect the
rest of nodes stop working rest of nodes