Competitive buffer management for shared-memory switches

We consider buffer management policies for shared memory packet switches supporting Quality of Service (QoS). There are two interesting dimensions in which the setting may different. The first is the packet size, whether all the packets of the same fixed size or do packets have variable length. The second is the value of the packets, do all the packets have the same value or do different packets have different values. The goal of the buffer management policy is to maximize the total value of packets transmitted. Our main result is to show that the well-known Longest Queue Drop (LQD) policy is 2-competitive and at least √2-competitive for the case of fixed size and value packets. We also show a 4/3 general lower bound on the competitiveness in this case. We extend the results to the case of variable size fixed value packets, and derive a slightly worse bound. For the case of variable value we derive randomized policy whose competitive ratio is logarithmic on the ratio of the maximal to minimal value .