In a multi-drop network, any node can communicate with any other node on the bus. However, because the bus is only two wires, collisions can occur if two or more nodes access the bus at the same time. Carrier sense multiple access/collision detection (CSMA-CD) is an older method for collision avoidance. The way CSMA-CD works is if there is a collision, the nodes involved in the collision will recognize there is a collision and enter a random wait time before trying to access the bus again. Probability says each random wait time will be different for each node, so when each node tries to access the bus again, statistically there is a strong probability the bus will be free.