Computer Fundamentals

1. Network Topology
Network topologies describe the ways in which the elements of a network are
connected. They describe the physical and logical arrangement of network nodes.
There are two types of network topologies
1. Physical topology
2. Logical topology
Physical Topology
Physical topology is the physical layout of nodes, workstations and cables in the
network. It is the arrangements of various elements (or components) of a network,
include device location and cable installation.
Logical Topology
Logical topology means how information is passed between two nodes in a network.
This topology is bound to the network protocol and define how data is moved
through out the network.
Types of Physical Topology
1. Bus topology
2. Star topology
3. Ring topology
4. Mesh topology
5. Tree topology

2. Bus Topology
 In bus topology, all the nodes (computers, servers, printers etc) are connected
to the single cable.
 This is known as a BUS and acts as the backbone of the network, which joins
every computer and peripheral in the network.
 Both ends of the shared channel have line terminator. The data is sent in only
one direction and as soon as it reaches the extreme and the terminator removes
the data from the line.
Advantages of Bus Topology
 Bus network are useful in small networks like setup in a small office.
 Require less cable length compared to other topologies.
 Easy to connect a computer.
 Easy to understand.
 Cost very less.
Disadvantages of Bus Topology
 Entire network shuts down, if there is any break in the main cable.
 Cable has a limited length,
 It is slow when more devices are added into the network.
 It is slower than ring topology.

3. Star Topology
 In star topology, every node is connected to central node, which is called hub
or switch.
 The central node (hub or switch) is the server and other node are clients.
 In this topology, data from source node is first delivered to the hub and then
transferred to the destination nodes.
 It is easy to add or remove nodes in this topology.
 Star topology gives better performance because data does not pass through
every node unlike bus topology.
 So if a particular workstation (or a node) gets an error then the entire network
is not affected. But if the central workstation (hub/switch) goes down, then
the entire network collapses.
Advantages of Star Topology
 Easy to install and modify.
 Hub can be upgraded easily.
 Easy to troubleshoot.
 New nodes can be added easily without affection the other nodes.
 If any of the local computers fails, the remaining portion of the network is
unaffected.
Disadvantages of Star Topology
 Whole network is depend on the central device so if the central device is failed
than whole network is stopped.
 It is slower than the ring topology.

4. Ring Topology
 In ring topology, all the computers (nodes) are connected in a closed loop.
 This topology works on the token based system and token travels in the loop.
 If the token is free, then the node can capture the token and attach the data and
destination address to the token, and then leaves the token.
 When token reaches at the destination node, the data is removed by the
destination node and token is free to carry the next data.
 The transmission is unidirectional, but it can be made bidirectional by having
connections between each Network Node, it is called Dual Ring Topology.
 In Dual Ring Topology, two ring networks are formed, and data flow is in
opposite direction in them. Also, if one ring fails, the second ring can act as a
backup, to keep the network up.
Advantages of Ring Topology
 Additional components do not affect the performance of network.
 Cheap to install and expand
Disadvantages of Ring Topology
 Troubleshooting is difficult in ring topology.
 Adding or deleting the computers disturbs the network activity.
 Failure of one computer disturbs the whole network.

5. Mesh Topology
 In mesh topology, each of the nodes are interconnected with one another.
 Every node sends its own signals and also relay data from other nodes.
 Mesh topology network can be formed by using the formula:
Number of cables = ( n ( n – 1 ) / 2 )
If 4 pc, then ( 4 ( 4 – 1 ) / 2 ) = 6 cables
 There are two types of mesh topology:
1. Full mesh topology
2. Partial mesh topology
 In full mesh topology, each node is connected to every other node in the
network.
 In partial mesh topology, some nodes are not connected to every node.
Advantages of Mesh Topology
 If one of the device (node) fails, then there is always an alternative present.
 Expansion and modification can be done without disrupting other nodes.

6.  Communication is very fast between two nodes.
 It is robust.
 Fault is diagnosed easily.
 Provides security and privacy.
Disadvantages of Mesh Topology
 It is quite expensive because a higher length of cable is required.
 Installation and maintenance is very difficult.
Tree Topology
 Tree topology is the combination of Bus and Star topology.
 A tree topology is also known as a star bus topology.
 The whole network is divided into segments, which can be easily managed
and maintained.
Advantages of Tree Topology
 Extension of bus and star topologies.
 Expansion of nodes is possible and easy.
 Easily managed and maintained.
 Error detection is easily done.

7. Disadvantages of Tree Topology
 Heavily cabled.
 Costly.
 If more nodes are added maintenance is difficult.
 Central hub fails, network fails.
Hybrid Topology
 It is a combination of two or topologies
 Inherits the advantages and disadvantages of the topologies included
Advantages of Hybrid Topology
 Reliable as Error detecting and trouble shooting is easy.
 Effective.
 Scalable as size can be increased easily.

8.  Flexible.
Disadvantages of Hybrid Topology
 Complex in design.
 Costly.