Classifying Networks by Topology

Bus Topology:

It is commonly used in early ethernet networks, 50 ohm coaxial cable used in it. 

Let me show you bus topology:

The problem with the bus topology is that every client wants to send data but they don't take turns as in token ring topology everybody had turns.

If client A wants to communicate with client B, A will whether there is traffic on the network or not, if there is no traffic then A will transmit, and if other client B is watching at the same time when traffic is not present now they both A and B conclude that cost is clear and they both send data, when they both send data, the packets from both of them collide that's called collision.

Now client A knows that collision occurs and it will retransmit and also client B will retransmit, now they both are going to get random timer to avoide collision, they both will send data in different time.

• Bus topology is used in early ethernet networks
• Typical speed is of 10Mbps 
• Distance limitation is 185m(10BASE2) or 500m(10BASE5)

Collision:

It occurs when two stations simultaneously transmit data on a network and results in data corruption.

CSMA/CD (Carrier Sense Multiple Access with Collision Detection):

It is used to remove collisions or to detect collisions. 

• Carrier sense means we are able to sense that we have a connection with media we have multiple stations that access the media at any time and if a collision occurs we are able to detect that collision