February 16, 2020
Amitraj
What is Topology ?
Topology defines the structure of the network of how all the components are interconnected to each other. There are two types of topology: physical and logical topology.
Physical topology is the geometric representation of all the nodes in a network.
OR
The way in which devices are interconnected to form a network is called network topology.
1. Bus Topology
Bus topology is a network type in which every computer and network device is connected to single cable. It transmits the data from one end to another in single direction. No bi-directional feature is in bus topology.
->The bus topology is designed in such a way that all the stations are connected through a single cable known as a backbone cable.
->The nodes are connected to the channel via drop lines.
->The bus topology is mainly used in 802.3 (ethernet) and 802.4 standard networks.
->The most common access method of the bus topologies is CSMA (Carrier Sense Multiple Access).
Advantages of Bus topology -
1. Low-cost cable: In bus topology, nodes are directly connected to the cable without passing through a hub. Therefore, the initial cost of installation is low.
2. Easy to install and maintain
3. Can be extended easily
Disadvantages of Bus topology -
1. If the common cable fails, then the whole system will crash down.
2. Extensive cabling: A bus topology is quite simpler, but still it requires a lot of cabling.
2. Ring Topology
In ring topology each terminal is connected to exactly two nodes, giving the network a circular shape. Data travels in only one pre-determined direction.
Topology defines the structure of the network of how all the components are interconnected to each other. There are two types of topology: physical and logical topology.
Physical topology is the geometric representation of all the nodes in a network.
OR
The way in which devices are interconnected to form a network is called network topology.
1. Bus Topology
Bus topology is a network type in which every computer and network device is connected to single cable. It transmits the data from one end to another in single direction. No bi-directional feature is in bus topology.
->The bus topology is designed in such a way that all the stations are connected through a single cable known as a backbone cable.
->The nodes are connected to the channel via drop lines.
->The bus topology is mainly used in 802.3 (ethernet) and 802.4 standard networks.
->The most common access method of the bus topologies is CSMA (Carrier Sense Multiple Access).
Advantages of Bus topology -
2. Easy to install and maintain
3. Can be extended easily
Disadvantages of Bus topology -
1. If the common cable fails, then the whole system will crash down.
2. Extensive cabling: A bus topology is quite simpler, but still it requires a lot of cabling.
2. Ring Topology
In ring topology each terminal is connected to exactly two nodes, giving the network a circular shape. Data travels in only one pre-determined direction.
fig: A ring topology comprises of 4 stations connected with each forming a ring..
The following operations takes place in ring topology are :
->One station is known as monitor station which takes all the responsibility to perform the operations.
->To transmit the data, station has to hold the token. After the transmission is done, the token is to be released for other stations to use.
->When no station is transmitting the data, then the token will circulate in the ring.
->There are two types of token release techniques : Early token release releases the token just after the transmitting the data and Delay token release releases the token after the acknowledgement is received from the receiver.
Advantages of Ring Topology
1. Very high transmission speeds possible
2. It is a more reliable network because the communication system is not dependent on the single host computer.
3. The possibility of collision is minimum in this type of topology.
Disadvantages of Ring Topology
1. Troubleshooting is difficult in this topology.
2. Failure of single node brings down the whole network
3. Star Topology
In star topology, all the devices are connected to a single hub through a cable. This hub is the central node and all others nodes are connected to the central node. The hub can be passive in nature i.e. not intelligent hub such as broadcasting devices, at the same time the hub can be intelligent known as active hubs. Active hubs have repeaters in them.
Advantages of Star topology
1. If N devices are connected to each other in star topology, then the number of cables required to connect them is N. So, it is easy to set up.
2. Each device require only 1 port i.e. to connect to the hub.
Disadvantages of Star topology
1. Failure of central node brings down the whole network.
2. Cost of installation is high.
4. Tree Topology
-> Tree topology combines the characteristics of bus topology and star topology.
-> A tree topology is a type of structure in which all the computers are connected with each other in hierarchical fashion.
-> The top-most node in tree topology is known as a root node, and all other nodes are the descendants of the root node.
-> There is only one path exists between two nodes for the data transmission. Thus, it forms a parent-child hierarchy.
Advantages of Tree Topology
1. Existing network can be easily expanded
2. Error detection: Error detection and error correction are very easy in a tree topology.
3. Limited failure: The breakdown in one station does not affect the entire network.
4. Point-to-point wiring: It has point-to-point wiring for individual segments.
Disadvantages of Tree Topology
1. Difficult troubleshooting: If any fault occurs in the node, then it becomes difficult to troubleshoot the problem.
2. High cost: Devices required for broadband transmission are very costly.
3. Insecure network.
5. Mesh Topology
-> In mesh topology, every device is connected to another device via particular channel.
-> It does not contain the switch, hub or any central computer which acts as a central point of communication.
-> The Internet is an example of the mesh topology.
-> Mesh topology is mainly used for wireless networks.
-> Mesh topology can be formed by using the formula:
Number of cables = (n*(n-1))/2;
Where n is the number of nodes that represents the network.
fig: Every device is connected with another via dedicated channels. These channels are known as links.
1. If suppose, N number of devices are connected with each other in mesh topology, then total number of ports that is required by each device is N-1. In the Figure 1, there are 5 devices connected to each other, hence total number of ports required is 4.
2. If suppose, N number of devices are connected with each other in mesh topology, then total number of dedicated links required to connect them is NC2 i.e. N(N-1)/2. In the Figure 1, there are 5 devices connected to each other, hence total number of links required is 5*4/2 = 10.
Advantages of Mesh Topology
1. It is robust.
2. Provides security and privacy.
3. Communication is very fast between the nodes.
Disadvantages of Mesh Topology
1. Installation and configuration is difficult.
2. Cost of maintenance is high.
6. Hybrid Topology
-> The combination of various different topologies is known as Hybrid topology.
-> A Hybrid topology is a connection between different links and nodes to transfer the data.
-> When two or more different topologies are combined together is termed as Hybrid topology and if similar topologies are connected with each other will not result in Hybrid topology. For example, if there exist a ring topology in one branch of ICICI bank and bus topology in another branch of ICICI bank, connecting these two topologies will result in Hybrid topology.
Advantages of Hybrid Topology
1. Reliable
2. Flexible
3. Effective
Disadvantages of Hybrid Topology
1. Costly Hub
2. Complex Design
