Fragmentation-aware survivable Routing and Spectrum Assignment in elastic optical networks

Transparent elastic optical networks (EON) allow provisioning connections with different bandwidth requirements in an efficient way. To achieve the high spectrum efficiency under dynamic traffic scenario, fragmentation-aware Routing, Modulation and Spectrum Assignment (RMSA) decisions is essential. Since fiber cuts are common, resiliency against single-link failures is another important topic. This can be provided efficiently through shared-path protection, which in turn complicates the connection provisioning problem. Unlike existing algorithms that decide first the primary and then the backup path, we introduce an algorithm in this paper that considers pairs of primary and backup paths. To select a candidate pair, we use a hybrid cost function that combines three different objectives: (1) the separation of primary and backup connections to different ends of the spectrum; (2) fragmentation-awareness as a pro-active provisioning objective trying to avoid fragmentation especially among primary resources and (3) maximization of shareability of backup resources among primary paths of link-disjoint connections. Using network level simulations in a scaled-down sample US network with load values of 190-240 Erlang, and bandwidth requests corresponding to 1% blocking probability, an average improvement of 79% compared to a recently presented reference algorithm is shown.