Collision reduction schemes for class-based traffic in OPS networks

Optical packet switching (OPS) is the promising switching technique to employ the huge bandwidth that is offered by all-optical networks under dense wavelength division multiplexing (DWDM) technology. However, optical packet collision is the major problem in an OPS network. Collision resolution and reduction are two schemes to deal with the optical packet collision problem. A resolution scheme used in OPS core switches deals with resolving arisen collisions, while a reduction scheme tries to reduce the number of collision events in OPS network. Collision reduction schemes must also be used in OPS ingress switches in order to help to reduce optical packet loss rate and/or also to reduce the number of contention resolution hardware required in OPS core switches. Since future OPS networks should support different levels of QoS (quality of service) required for newer applications, in this paper, we review the recent collision reduction schemes proposed for QoS-capable OPS networks.