Deadlock of avoidance backoff schemes in policing mechanisms

Backoff time computations are widely used in order to avoid the impact on the network performance whenever the increment of offered load arises. The fluctuation of the offered load causes congestion at the waiting room. Furthermore it leads to or be close to a deadlock situation as many attempts are made to relieve the busy service center. The backoff computation helps reduce the repetition of I/O cycles (required to switch the task from waiting room to service center) and prevent repeated attempts to reach off due to the congested traffic at the waiting room. Backoff time computation schemes proposed in this paper are pseudorandom backoff (PB) time, exponential backoff (EB) time and random backoff (RB) time. In pseudorandom backoff (PB) scheme, none of the computations is applicable except the queue discipline. In this paper, the FIFO and the maximum queue size are preset. In exponential backoff (EB) scheme, each node doubles the backoff time interval up to the maximum backoff time after each attempt. On the other hand, it decreases the backoff interval time to the minimum value after a successful attempt. In random backoff (RB) scheme, the delay in queue is computed randomly, meaning that all frames are to wait in queue until the next attempt is made during for any random period of time. The performance of the three backoff schemes has been investigated by the fluctuation of telecommunication traffic stream (ON/OFF stream). Simulation results indicate that EB and PB help improve the performance of the network depending on maximum waiting time in queue. Moreover, RB is found to be better regardless of QoS and especially if the required bandwidth are substantial