Routing on Input Queued Buffered Sparse-Crossbar Packet Concentrators

In this paper we characterize the features of good packet routing schemes for input queued sparse crossbar based packet concentrators and propose a polling based routing algorithm which achieves near optimal performance. It has been shown by the authors of this paper that the performance of an input queued packet concentrator with different input and output packet rates can be modeled by a GI/D/c queueing system. This result was shown to give the least packet loss for i.i.d batch arrivals for fixed length packets. We now address the issue of finding a routing scheme which tries to achieve this best possible performance specifically on a particular type of packet concentrator, the sparse crossbar concentrator with a crosspoint structure based on the buffered network model construction proposed by Oruç and Gündüzhan. We identify the constraints imposed on routing by the asymmetric crosspoint fabric of the sparse crossbar concentrator and the difference in input and output packet rates. A round-robin polling based heuristic algorithm is then proposed which is shown via simulation to achieve very good performance. In particular, we also show that when inputs are saturated this algorithm emulates the GI/D/c system, i.e., achieves the best possible performance.