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Lightpath communications: A novel approach to optical WANs
Abstract
This dissertation presents a new approach, the Lightnet architecture, addressing the substantial mismatch between optical transmission bandwidth and electronic switching speeds. The Lightnet is a wide area network that proposes to take advantage of the convenient topologies available in the local and metropolitan area domain. By establishing lightpaths, direct optical communication paths, it implements the virtual links required to implement regular virtual topologies. The fixed allocation of transmission bandwidths to certain paths (establishing the lightpaths) creates a tradeoff between transmission and processing bandwidth. By sacrificing some of the ample transmission bandwidth, both the number of switching instances a packet incurs in an end-to-end transmission, and the amount of processing required at each switching instance are decreased. Thus, less processing is required per packet delivery or alternatively, more packets may be delivered using the same limited processing resources, resulting in increased user-available throughput. In terms of performance, the Lightnet is shown to increase user available throughput by up to almost an order of magnitude for the sample networks and virtual topologies studied. In terms of buffering requirements at intermediate nodes, it is shown that the Lightnet can carry the same load as a conventional store and forward network using less than half the number of buffers, or alternatively, carrying substantially higher load using approximately the same number of buffers. In terms of hardware requirements, by using the virtual topology embedding, lightpath routing, and wavelength assignment algorithms presented in the dissertation, the Lightnet is shown to be implementable using a moderate number of wavelengths (e.g. 14 wavelengths were required to establish a 32 node hypercube virtual topology over a sample Arpanet-like physical network) and photonic switch sizes. ftn*This work was funded under DARPA grant number NAG-2-578
Subject Area
Electrical engineering|Computer science
Recommended Citation
Karmi, Gadi, "Lightpath communications: A novel approach to optical WANs" (1990). Doctoral Dissertations Available from Proquest. AAI9110161.
https://scholarworks.umass.edu/dissertations/AAI9110161