Packet scheduling in a combined input and output queued switch using virtual time reference system

There i s an increasing demand for Internet core nodes to have (I) quality-of-service (QoS) guarantees and (2) higher switching capacity. The combined input and output queued (CiOQ) switching has been shown to be a promising solution to meet such demand. However, many of the proposed scheduling algorithms fo r a CIOQ switch cannot be practically implemented due to problems from scalability and complexity. This paper shows how the virtual t ime reference system ( V T R S ) proposed in [15] can be applied to packet scheduling in a CIOQ switch. The V T R S is a unifying scheduling framework to provide scalable support f o r guaranteed services. i n the context of packet scheduling fo r a CIOQ switch, we show that the use of V T R S can eliminates both the scalabili t y and complexity problems associated with many of the scheduling algorithms proposed in the literature. More important, we show that in term of of providing end-toend guaranteed service, packet scheduling using V T R S for a CIOQ switch has the same performance as an output queued (OQ) switch employing weighted fair queueing (WFQ) scheduler.