Three Shades of Partial Protection in Elastic Optical Networks
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Partial protection strategies based on the observation that in failure events, a service can tolerate a certain amount of degradation and therefore by reducing the protection traffic in the network, better spectrum utilization could be attained. Such concept has been widely studied in the traditional WDM context and yet has been somehow faded due to the fact that fixed transmission technologies allow small room for spectral improvement. This paper aims to renew the interest in partial protection and re-adapt it to the context of elastic optical networks. The evolutionary perspective we lay out in this paper identifies a new route for achieving greater spectral efficiency in a pragmatic way by simply differentiating the protection services for each demand rather than the uniform treatment for all demands. In doing so, we present a new research problem entitled, routing, modulation level, spectrum and protection service assignment which is an extension of the well-established one, that is, routing, modulation level, and spectrum assignment as the (partial) protection service for each demand is taken into account and optimized. Three variants of that problem reflecting shades of applying partial protection are covered in details. Specifically, the first one considers the intuitive case as the relative amount of protection traffic for each demand is given as the input to the network planning process while the second one is dedicated to the special case of enforcing the same figure of partial protection for all demands. More interesting is brought in the third variant where given the service level agreement for the total network traffic, we provide the optimal solution that determine the protection service for each individual demand so as to minimize the spectral occupancy.
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