Rate-based pacing for small buffered optical packet-switched networks

Onur Alparslan, Shin'ichi Arakawa, Masayuki Murata
2007 Journal of Optical Networking  
Preface Recent advances in the optical networks like dense wavelength division multiplexing (DWDM), which combines and transmits multiple signals simultaneously at different wavelengths on the same fiber, allow achieving ultra high data transmission rates in optical networks. While optical transmission rates were getting faster and faster, electronic components in routers like electronic RAM could not pace due to high costs and electronic limitations and became a bottleneck. Therefore, it
more » ... necessary to do some basic operations like buffering and switching in the optical domain without converting packets to electronic domain. However, the lack of high capacity optical RAM makes it difficult to buffer optical packets in optical packet switched (OPS) networks. According to a rule-of-thumb, buffer size of each output link of a router must be B = RT T × BW , where RT T is the average round trip time of flows and BW is the bandwidth of output link, in order to achieve high utilization with TCP flows. However it requires a huge memory size due to high speed of optical links, so it is currently unfeasible. Currently, the only available solution that can be used for buffering in the optical domain is using FDLs. Contended packets are switched to FDLs in order to be delayed. However, FDLs have important limitations. First of all, FDLs require very long fiber lines that cause signal attenuation inside the routers. There can be a limited number of FDLs in a router due to space considerations, so they can provide a small amount of buffering. Second, FDLs provide only a fixed amount of delay. FDL buffering is possible with today's technology, so many researchers consider FDL buffers to resolve contentions in optical networks. On the other hand, optical RAM is under research and it may be available in the near future.
doi:10.1364/jon.6.001116 fatcat:uh5b4asrtff2xmgpbkhh7t77tq