Abstract. The problem of minimizing the number of optical nodes with signal regeneration capability can be constrained to guarantee a desired degree of end-to-end connectivity in the all-optical transport network. The problem can be formulated using a k-connected, k-dominating node set, which is a known approach in mobile ad hoc wireless networks. This paper presents a preliminary study aimed at establishing whether efficient centralized solutions to this problem in optical networking ought to be investigated to improve the decentralized solutions already available for wireless networks.

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Optical signal regenerators (3R) are required to overcome the adverse effect of fiber and other transmission impairments. 3R units may be placed either at every node (full placement) or at some selected nodes (sparse placement) of the optical network. It has been argued [1] that while the latter placement strategy may not be optimal in terms of the total number of 3R units required to support a given set of static traffic demands, it offers a number of practical advantages over the former, e.g., a contained complexity of network management in terms of signaling overhead.In this paper the full and sparse placement strategies are compared in a dynamic optical network, whereby Iightpaths are set up and tom down to best fit the offered changing demands. The study shows that the blocking probability due to the lack of available 3R units achieved by the sparse placement strategy may be comparable to the one achieved by the full placement strategy. Surprisingly, it may even be lower in some cases, thus providing an additional motivation in favor of the sparse placement strategy. The study also shows that the algorithm used to choose the nodes where to place the 3R units must be designed carefully. Two placement algorithms are compared, reporting differences in signaling overhead level as high as 6 times (when achieving a desired level of Iightpath connectivity) and differences in blocking probabilities as high as two orders of magnitude (when using the same level of signaling overhead).

In this paper we incorporate the rerouting of backup paths to the Call Admission Control algorithm of Sub-Graph Routing Protection (SGRP). Sub-Graph Routing Protection with On-Arrival Planning (SGRP-OAP) has the twofold benefit of strongly reducing the blocking probability of the protected system while eliminating the physical rerouting of established connections, which is a major drawback of the original proposal of SGRP. The new scheme is so capacity-efficient that, for all investigated topologies, at low traffic intensity the blocking probability of the system protected against single link failures is the same as the blocking probability of the unprotected system. This is possible because the new protection scheme is extremely effective in using the idle network capacity to provide backup paths.