Blocking Probability and the Right Size Buffer

• So in the finite buffer case,

  

• Note that is the probability that the buffer is full at an arbitrary point in time.

• Since arrivals are independent of buffer state, we have = = probability an arriving packet is turned away due to a full buffer.

• is called the blocking probability.

• is very important!
• We can use to choose the correct buffer size.

• Example: For , for N=18, while for N=19.

• Thus, if we desire a blocking probability less than , we need a buffer capable of holding 19 packets.