Optimal Buffer Sharing
نویسندگان
چکیده
Absfract-We a d h the pmblem of designing optimal bufYer management policies in shared memory switches when packets already accepted in the switcb can be dropped (pushed*ut). Our goal is to maximize the overall throughput, or equivalently to d n h h e the overall loss probability in the system. For a system with two output ports, we prove that the optimal policy is of push-out with threshold type (POT). The same result holds if the optimality criterion is the weighted sum of the port loss probabilities. For this system, we also give an approximate method for the calculation of the optimal threshold, which we conjecture to be asymptatdadiy correct. For the N-ported system, the optimal policy is not kwm in general, but we show that for a symmetric system (equal traf6c on all ports) it consists of always accepting arrivals when the b d e r is not full, and dropping one h m the longest queue to aecollLmodpte the new arrival when the buffer is full. Numerical rpsolts are provided which reveal an interesting and somewhat unexpected phenomenon. While the overall improvement in loss probability of the optimal POT policy over the optimal eoordinate-convex policy is not very significant, the loss probability of an individrral output port lplllsins approximately constant as the load on the other port varies and the optimal POT policy i s applied, a property not shared by the optimal coordinate-convex policy.
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