A New Service Guaranteed Scheduling Policy for Buffered Crossbar Switches

Fast scheduler with service guarantee performance is preferred in high speed switching networks. Based on the features of EPFTS (Ethernet-oriented physical frame timeslot switching) and CICQ (combined input-crosspoint-queued), a new scheduling policy called timeslot reservation weighted fair scheduling (TRWFS) is introduced. In order to provide bandwidth guarantee service to guarantee-required (GR) traffic, TRWFS takes the total reserved timeslots of aggregated GR traffic on each I/O port pair as the basic scheduling weight and forwards traffic according to the following principles: 1) Giving dispatching priority to GR traffic and 2) Trying to balance the surplus timeslots (defined as service discrepancy between the actual packetized system and the idealized fluid system) for GR-traffic on each I/O port pair. In order to apply TRWFS and decrease the implementation complexity of TRWFS to constant time complexity O(1), two scheduling algorithms—TRWFS_I and TRWFS_II are further presented. Analysis and simulation results demonstrate that the two TRWFS algorithms both reach the design objective. Moreover, simulation results show that TRWFS/round-robin combined scheduling scheme in CICQ switches require fewer crosspoint buffer compared with other schemes.