OPTIMAL QUEUING POLICIES FOR FAST PACKET SWITCHING OF MIXED TRAFFIC

The power of ATM (asynchronous transfer mode) is its ability to provide bandwidth on demand: different sources can have different bandwidth requirements. Sources also differ in performance requirements: some ask for minimal delay variations whereas others must have extremely low cell loss probabilities. This paper shows how these complementary performance requirements can be exploited with an LDOLL (low delay or low loss) queue, where sources get either service priority or storage priority. The space of possible LDOLL queueing policies is very large: even after a justified reduction, the size is still of order O(2Q2), Q being the maximum number of ATM cells in the LDOLL queue. Using Markov decision theory and concepts of linear programming, we arrive at only Q so-called efficient solutions. These are the LDOLL threshold policies, which are conceptually appealing, robust in performance, and practical from the implementation viewpoint.