Dynamic Protection of Optical Networks

Publication: ResearchPh.D. thesis – Annual report year: 2008

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This thesis deals with making optical networks resilient to failures. The recovery performance of path, segment and span restoration is evaluated in a network with limited wavelength conversion capability using both standard and enhanced wavelength assignment schemes. The enhanced wavelength assignment scheme is based on the Suggested Vector (SV), which is a Generalized Multi-Protocol Label Switching (GMPLS) compliant signalling extension aiming at wavelength conversion minimization. To increase the recovery percentage, two modifcations of the signalling session are proposed and evaluated through simulation. By resolving wavelength contention, the blocking reduction scheme reduces the number of necessary recovery retries and thereby the restoration time and control plane load. The stub-awareness schemes avoids wavelength conversions when merging the restoration segment to the connection stubs at the failure adjacent nodes. Both modifcations have a positive influence on the recovery percentage. The recovery enhancements are applicable in both single and multi-domain network environments. Stub release, where the still working parts of a failure affected connection are released prior to recovery initiation, has shown to increase the recovery percentage. If the lack of span resources limits successful connection recovery, both span and node resources (i.e., Wavelength Converters (WCs)) should be released, while it is suffcient to release the WCs if they are the limiting factor. The effect of the modularity of capacity units is investigated for resilient network design. Different span upgrading strategies and algorithms for finding restoration paths are evaluated. Furthermore, the capacity effciency of constraining restoration requests for the same destination node to the same restoration path is evaluated
Original languageEnglish
Publication dateSep 2008
Number of pages208
StatePublished
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