NETp1-02: Providing QoS Guarantees in Buffered Crossbars with Space-Division Multiplexing Expansion

Though output-queued (OQ) switch can provide quality-of-service (QoS) guarantees, the high-speed memory requirements limit its use for large capacity switching architecture. A recent result indicates that a buffered crossbar switch with three times speedup can perfectly emulate an OQ switch. However, to achieve a speedup factor of three, a conventional buffered crossbar switch requires the switch fabric and the memory to operate three times faster than the line rate. In this paper, we propose a buffered crossbar switch with space- division multiplexing expansion (denoted as SDM CICOQ switch) which only requires the switch fabric and the memory to operate at the line rate. Using fluid model, we prove that an SDM CICOQ switch with an expansion factor 2 can achieve 100% throughput for any admissible traffic. It is also proved that an SDM CICOQ switch with an expansion factor 2 can exactly emulate an OQ switch. All the scheduling algorithms used in emulating OQ switch are distributed, thus are practical. Finally, for the simplicity of implementation, we present a hierarchical priority scheduling (HPS) scheme for the SDM CICOQ switch. Simulation results show that the SDM CICOQ switch operating under the HPS scheduling scheme can obtain good performance.