Expelling policies for shared memory fast packet switches with variable size packets of multiple priority

In this paper we study the efficient design of buffer management policies for QOS efficient shared memory based fast packet switches. There are two aspects that are of interest. First is the packet size: whether all packets have same or different sizes. Second aspect is the value or space priority of the packets, do all packets have the same space priority or different packets have different space priorities. We present two types of policies to achieve QOS goals for packets with different priorities: the push out scheme and the expelling scheme. For this paper we consider the case of packets of variable length with two space priorities and our goal is to minimize the total weighted packet loss. Simulation studies show that, expelling policies can outperform the push out policies when it comes to offering variable QOS for packets of two different priorities and expelling policies also help improve the amount of admissible load. Some other comparisons of push out and expelling policies are also presented using simulations.