Computer Network : Star Network Topology

All hosts in star topology are connected to a central device, known as Hub device, using a point-to-point connection. That is, there exists a point to point connection between hosts and Hub. 
Many home networks use the star topology. A star network features a central connection point called a "hub node". 
Devices typically connect to the hub with Unshielded Twisted Pair (UTP) Ethernet.
Compared to the bus topology, a star network generally requires more cable, but a failure in any star network cable will only take down one computer's network access and not the entire LAN. (If the hub fails, however, the entire network also fails.)

Computer Network : Ring Network Topology

In a ring network, every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction (either "clockwise" or "counterclockwise"). A failure in any cable or device breaks the loop and can take down the entire network.  
Local-area network (LAN) topology is a ring. All of the nodes are connected in a closed loop. Messages travel around the ring, with each node reading those messages addressed to it. One main advantage to a ring network is that it can span larger distances than other types of networks, such as bus networks, because each node regenerates messages as they pass through it. Ring topologies are found in some office buildings or school campuses.

Computer Network : Bus Network Topology

A computer network topology is the physical communication scheme used by connected devices. 

Bus Topology is a very simple network topology. All the nodes are connected to the single cable called bus, by the help of interface connectors. This central cable is the backbone of the network and is known as Bus Every workstation communicates with the other device through this Bus. 
It is easy to set-up and extend bus network. Bus topology costs very less. Linear Bus network is mostly used in small networks and it is useful for LAN.
There is a limit on central cable length and number of nodes that can be connected. There is always a Dependency on central cable in this topology. If the main cable (i.e. bus ) encounters any problem, whole network breaks down. This network topology is not suitable for networks with heavy traffic. And Security is very low because all the computers receive the sent signal from the source.