The paper describes SR/sup 3/ (synchronous round robin with reservations) a collision-free medium access control protocol for all-optical slotted packet networks based on WDM multi-channel ring topologies where the nodes are equipped with one fixed-wavelength receiver and one wavelength-tunable transmitter. SR/sup 3/ is derived from the SRR and MMR protocols previously proposed by the authors for the same class of all-optical networks. SRR and MMR already achieve an efficient exploitation of the available bandwidth, while guaranteeing a throughput-fair access to each node. SR/sup 3/, in addition, allows the nodes to reserve slots, thereby achieving a stronger control on access delays; it is thus well suited to meet tight delay requirements, as is the case for multimedia applications. Simulation results show that SR/sup 3/ provides very good performance to guaranteed quality traffic, but also brings significant performance improvements for best-effort traffic.