Topology refers to the layout of the network i.e. the arrangement in which all the 
  computers and other networking devices are physically wired. In nutshell, network 
  topology is the shape of the network.
  The characteristics of a network depend upon the type of topology selected for 
  designing that network. There are five basic network topologies:-
  1) Star Topology
  2) Ring Topology
  3) Bus Topology
  4) Tree Topology, and
  5) Mesh Topology
                 STAR TOPOLOGY
 In star connection (also known as Hub-and-
 spoken topology), all the computers are 
 connected with a central hub. All the data 
 communication in the network takes place 
 through the hub only. If a computer, say 
 computer 1, sends data to another computer, 
 say computer 2, the data sent by computer 1 
 will first go to the central hub and then the 
 hub will send the data to computer 2.
 In a star topology, all the work stations are 
 directly connected to central hub with the help 
 of cables. No two workstations are connected 
 directly to each other.
 Advantages of Star Topology:-
 1) Establishing a network using star topology is easy to install and wire.
 2) Failure or removal of one nod (computer, printer, etc.) doesn’t effect the working of other 
 nodes.
 3) In star connection faulty parts can be detected and removed with case without affecting 
 working of other systems.
 4) Star topology allows a better management of LAN as, if one of the cables turns faulty only that 
 cable attached workstation turns faulty and rest workstations remain working as usual.
 Disadvantages of Star Topology:-
 1) Since, every workstation is directly linked with the central hub, the longer length of cable is 
 required for networking.
 2) The functioning of the entire network  depends upon the central hub. If the hub fails, the 
 entire network fails.
 3) It is a costlier method of establishing LAN as compared to ring or bus topology as the cost 
 required for purchasing the longer length of the cable and the hub is very high.
                 RING TOPOLOGY
 In the ring topology, all the nodes(computers) are connected to 
 each other in a manner that the last computer connected to 
 the network is connected to the first computer and hence, it 
 forms a ring. 
 For example, if node C2 sends a message to node C5 as 
 shown in figure, first the data or message will be received
 by the in-between nodes i.e. C3 and C4. The signals sent by
 C2 will be received by the repeater of C3, which will 
 regenerate and amplify the signals and forward it to node C4.
 Ultimately node C5 will receive the message sent by node C2.
  
 Advantages of Ring Topology:-
 1) Since each computer is connected to the next computer, short cable length is required for 
 networking.
 2) Low cost is required to set up a ring network than star network for two reasons one, cable 
 length required is shorter and two, the central hub is not required.
 3) In the Ring network, each computer has equal access to the ring and there is no monopoly of 
 any single computer.
 4) Ring network can be easily installed and configured.
 Disadvantages of Ring Topology:-
 1) Failure of one computer affects the whole network.
 2) If any fault develops in the cable, it is very difficult to locate and remove the fault.
 3) Adding and removing one computer to/from the network is very difficult as it affects the 
 whole network.