Scheduling Algorithms for Optical Packet Fabrics

Abstract

Utilizing optical technologies to build packet fabrics for high-capacity switches and routers has several advantages in terms of scalability, power consumption, and cost. However, several technology related problems have to be overcome to be able to use such an approach. The reconfiguration times of optical crossbars are longer than those of electronic fabrics and end-to-end clock recovery in such systems add to the reconfiguration overheads. Both these problems can limit the efficiency of optical packet fabrics. In addition, existing work on input-buffered switches mostly assumes fixed size packets (referred as envelopes in this paper). When fixed size switching is used for Internet protocol networks where packets are of variable size, the incoming packets need to be fragmented to fit the fixed size envelopes. This fragmentation can lead to, possibly large loss of bandwidth and even instability. This paper addresses all of the above issues by presenting packetization and scheduling techniques that allow optical packet fabrics to be used within switches and routers. The proposed scheme aggregates multiple packets in a single envelope and when used in combination with proper scheduling algorithms, it can provide system stability as well as bandwidth and delay guarantees. As a result of the aggregation method, the reconfiguration frequency required from the optics is reduced, facilitating the use of optical technologies in implementing packet switch fabrics.