Consider a network layer that

Delegating the retransmission decisions to the network layer might be appropriate in many settings.In a congested system,immediate retransmissions might increase the congestion in the system,resulting in more collisions and lower throughput.Instead,the decision of when to retransmit could be left to the upper layers,w hich could delay the retransmission by a period of time that is proportional to the current congestion in the system.An exponential backoff strategy is the most commonly used strategy to avoid over-congesting a system.