Efficient verification algorithm for topology and quality of optical fibers in optical-circuit-switched data center networks

The introduction of optical circuit switches (OCSs) has enabled the implementation of capacity- and energy-efficient networks in production data centers. To correctly operate optical-circuit-switched data center networks (OCS DCNs), fibers between pairs of terminals (e.g., servers or top-of-rack switches) and OCSs should be verified before starting operations; otherwise, unexpected failures during operations could occur. However, this task is difficult because OCSs cannot use topology discovery or link-monitoring functions, which are only available on electrical packet switches. We thus studied a fiber-topology and quality verification (FTQV) problem for OCS DCNs. Though a previous study inspected fibers between pairs of OCSs in hierarchical OCS DCNs using only one dedicated tester for fiber probing, making the process time-consuming, we consider verifying fibers between pairs of terminals and OCSs by using the digital diagnostic monitoring (DDM) function at multiple terminals. We thus developed new theories, to the best of our knowledge, for correctly carrying out FTQV even when parallel probes are sent and then designed an algorithm that efficiently solves the FTQV problem with near-optimal inspection steps. We also theoretically analyzed the conditions of detectable and undetectable malfunctioning fibers given the maximum measurement error of the DDM function. Experimental results indicate the correctness of our theoretical analysis and superior performance of our algorithm; it completes FTQV at most 93.0 times faster than a baseline algorithm. The feasibility of our algorithm was also demonstrated through evaluations on an actual network.