2. Index
Sr. No Title Page No
1 Topology 3
Types of Topology 4
2 Bus Topology 5
How to connect Pc’s
How data is transferred
Characteristics
Merit & Demerit of Bus Topology 5
3 STAR Topology 6
Characteristics
Merit & Demerit of STAR Topology 6
4 Ring Topology 7
Merit & Demerit of Ring Topology 7
5 Mesh Topology 8
Merit & Demerit of Mesh Topology 8
6 Tree Topology 9
Merit & Demerit of Tree Topology 9
7 Hybrid Topology 10
Troubleshooting
Acknowlegdement
8 Reference 11
3. 1. What is Network Topology
Network Topology means arrangement and connection of computer or nodes or
devices in such way by which they can communicate with one-another. In Network
topology many other devices are present like cables, switch, Hub, Server etc.
There are main two category I) Physical
II) Logical.
I. Physical category means network include the device, location, and cable
installation.
There are seven layers in Physical category which do interaction between
two computers.
II. Logical category means HOW actually data is transfer in Network.
It shows the way of signals act in transmission medium.
A logical topology is not necessarily the same as it’s physical topology.
4. 1.1 Types of Topology
There are main 6(six) topologies.
1) Bus
2) STAR
3) Ring
4) Mesh
5) Tree
6) Hybrid
5. 1) Bus Topology
A bus network topology is a network architecture in which a set of clients are
connected via a shared communications line which connect with Terminator on both
side, called a bus topology. The more PCs on a bus, the more likely you’ll have a
communication traffic jam. It may have problems when two clients want to transmit at
the same time on the same bus. Central cable known as BACKBONE of the Network.
Fig (1). Bus Topology
How to connect PC’s:-
The type of wires used for Bus Networks in the 80’s was called Thicknet and Thinnet .A
Thicknet cable (very large about 1 inch in diameter usually yellow was hung around a
room).Thinnet cables were connected to the PC’s NIC and a Transceiver. The Transceiver
was tapped into the Thicknet cable.To stop the message from bouncing back and forward
down the wire (known as signal bounce) both ends of the network are terminated with
50Ω resistors.
How data is transferred:-
All computers on a network have a distinct address just like your house does.A message
would be send from one computer with the address of another computer attached to the
message.The message is broadcasted to all the computers on the network until the
addressed PC accepts the message.
Characteristics:-
1. It transmits data only in one direction.
2. Every device is connected to a single cable.
Advantages:-
Easy to implement and extend.
less expensive than other topologies
Cost effective; only a single cable is used.
Easy identification of cable faults.
6. Dis-advantages:-
If there is a problem with central cable, the entire network
breaks down.
Maintenance costs may be higher in the long run.
Performance degrades as additional computers are added.
Commonly has a slower data transfer rate
2) STAR Topology
A star network consists of one central switch, hub or computer, which acts as a
conduit to transmit messages. The star topology reduces the chance of network failure
by connecting all of the systems to a central node. Data on a star network passes
through the hub, switch, or concentrator before continuing to its destination. The hub,
switch, or concentrator manages and controls all functions of the network. It also acts
as a repeater for the data flow.
Fig (2). STAR Topology
Characteristics:-
1. Every node has its own dedicated connection to the hub.
2. Acts as a repeater for data flow.
7. 3. Can be used with twisted pair,Optical Fibre or Coaxial cable.
Advantages:-
Star topology prevents the passing of data packets through an
excessive number of nodes.
Each device is inherently isolated by the link that connects it to
the hub.
As the central hub is the bottleneck, increasing its capacity, or
connecting additional devices to it, increases the size of the
network very easily.
Dis-Advantages:-
High dependence of the system on the functioning of the
central hub
Failure of the central hub fails the whole network.
3) Ring Topology:-
A ring network is a network topology in which each node connects to exactly
two other nodes; Data travels from node to node, with each node along the way
handling every packet. Because a ring topology provides only one pathway between
any two nodes, ring networks may be disrupted by the failure of a single link. A node
failure or cable break might isolate every node attached to the ring.
8. Fig (3). Ring Topology
Advantages:-
Performs better than a bus topology under heavy network load
Does not require a central node to manage the connectivity
between the computers
Dis-advantages:-
One malfunctioning workstation can create problems for the
entire network
Moves, adds and changes of devices can affect the network
Bandwidth is shared on all links between devices
4) Mesh Topology:-
Mesh networking (topology) is a type of networking where each node must
not only capture its own data, but also collaborate the data in the network of other
nodes. A mesh network can be designed using a flooding technique or
a routing technique. When using a routing technique, the message propagates along a
path, by hopping from node to node until the destination is reached.
9. Fig (4). Mesh Topology
Advantages:-
No-traffic between computers
Failure of one node not affects rest of the network.
Dis-advantages:-
Due to the amount of cabling and number of input output ports,
it is expensive.
Large space requires torunning cables.
5) Tree Topology:-
The type of network topology in which a central 'root' node is connected to
one or more other nodes that are one level lower in the hierarchy with a point-to-point
link between each of the second level nodes and the top level central 'root' node, while
each of the second level nodes that are connected to the top level central 'root' node
will also have one or more other nodes that are one level lower in the hierarchy
10. connected to it, also with a point-to-point link, the top level central 'root' node being
the only node that has no other node above it in the hierarchy. Tree topology is a
combination of Bus and Star topology.
Fig (5). Tree Topology
Advantages:-
A point to point connection is possible with Tree Networks.
All the computers have access to the larger and their immediate
networks.
Dis-advantages:-
In a Network Topology the length of the network depends on the type
of cable that is being used.
It is difficult to configure and can get complicated after a certain point.
6) Hybrid Topology:-
Hybrid networks use a combination of any two or more topologies in such a
way that the resulting network does not exhibit one of the standard topologies. It
consist all advantages and Dis-advantages of topologies which include in it.
11. Fig (6.1). Ring + Bus Topology
Fig (6.2).STAR + BUS Topology
Troubleshooting:-
One of the main problems with the BUS TOPOLOGY is that it is not very
fault tolerant, a break or defect in the bus would affect the whole network. In
STAR TOPOLOGY,as each computer is connected to a central device (Hub)
the location of the Hub must be made as central as possible, so as to reduce
cable lengths.The drawback to this type of topology is if a central device was
12. to fail then all computers connected to that device would not be able to see
the network.
Acknowledgement:-
In performing our project, we had to take the help and guideline of some respected persons,
who deserve our greatest gratitude. The completion of this assignment gives us much
Pleasure. We would like to show our gratitude Ms.Mariam Ehsan, Course Instructor,
University Of Gujrat for giving us a good guideline for project throughout numerous
consultations. We would also like to expand our deepest gratitude to all those who have
directly and indirectly guided us in writing this assignment.
In addition, a thank you to Professor Muzaffar, who introduced us to the Methodology of
work, and whose passion for the “network topology” had lasting effect..
Many people, especially our classmates and team members itself, have made valuable
comment suggestions on this proposal which gave us an inspiration to improve our project.
We thank all the people for their help directly and indirectly to complete our assignment.
References:-
Web Reference
http://en.wikipedia.org
http://en.google
http://en.wikipedia.org/wiki/Network_Topology
http://en.Computerline.com
Books
Networking topologies-E.Balguruswamy
A text book of computers-Andrew Symonds
