We present a novel architecture for strictly non-blocking multistage photonic switches implemented using tunable wavelength converters and arrayed waveguide gratings. Clos networks, studied mostly in electronic domain, are required when the physical switching needs exceed the capacity of the largest feasible single crossbar switch. Unfortunately, straightforward extensions of these networks to the photonic domain show that the switch size has to be severely limited by the coherent crosstalk in each of the AWGs. We describe how recursive Clos networks free of coherent crosstalk can be built taking into account the current physical limitations of arrayed waveguide gratings.

Protection techniques for optical networks mainly rely on preallocated backup bandwidth, which may not be able to provide full protection guarantee when multiple failures occur in a network. To protect against multiple concurrent potential failures and to utilize the available resources more efficiently, strategies such as backup reprovisioning (BR) rearrange backups of protected connections after one failure occurs or, more generally, whenever the network state changes, e.g., when a new request arrives or terminates. Recently, new solutions for automatized management in optical networks promise to allow customers to specify on-demand the terms of the service level agreement (SLA) to be guaranteed by the service provider. In this paper, we study different backup reprovisioning techniques able to further reduce the capacity requirements exploiting the knowledge, among the other service level specifications (SLSs), of the connection holding time.

In this paper we provide a mathematical ILP model for the Regeneration Placement Problem (RPP) which minimizes the total number of regeneration nodes allocated in a translucent optical network ensuring that all the node pairs can always reach one another via two link-disjoint lightpaths under physical-impairment constraints. Since RPP is NP-complete, large-site design problem can not be solved relying upon exact approaches. We then propose a game-theoretic approach to model RPP as a non-cooperative game and solve it applying the best response dynamic concept. Finally, we evaluate the performance of the proposed approach in terms of closeness of the obtained results to these provided by ILP: a MILP formulation is given in order to study the quality of the Nash equilibria by comparison to Price-of-Anarchy and Price-of-Stability bounds.

Recently, new solutions for automatized management in optical networks promise to allow customers to specify on-demand the terms of the service level agreement (SLA) to be guaranteed by the service provider. In this paper we show that is possible to design a highly efficient load balancing algorithm, called RABBIT, for the dynamic provisioning of connections exploiting the knowledge, among the other service level specifications (SLS), of the connections duration. The core idea of RABBIT consists in routing connections based on the transient probability of future-link congestion, that can be estimated with higher precision when the knowledge of connections durations is given. So, we introduce a time-dependent link-weight assignment that evaluates future link congestions probability based on the transient analysis of the Markovian model of the link, making it computationally feasible by means of an effective approximation technique. By means of an extensive set of simulative experiments, we compare our approach to other traditional holding-time agnostic, yet efficient, dynamic routing algorithms. We consider different performance metrics, among which the blocking probability (BP), in a wavelength-convertible WDM mesh network scenario. For a typical US nationwide network, RABBIT obtains savings on BP of up to 20% for practical scenarios.

In this paper we devise an highly-efficient load balancing algorithm, called LB-HTA, for the dynamic provisioning of connections with known duration in WDM networks. We introduce a time-dependent link-weight assignment that captures future congestion of links, leveraging the knowledge of connection durations. By means of an extensive set of simulative experiments, we compare our approach to other traditional, yet holding-time agnostic, dynamic routing algorithms. For a typical US nationwide network, LB-HTA obtains significant saving in blocking probability for practical scenarios. Moreover, we address two key-questions regarding holding-time-aware dynamic routing. Three main traffic models are considered here, namely i) dynamic traffic, ii) dynamic traffic with known durations and iii) scheduled traffic: how much the knowledge of connection durations improves the performance with respect of a holding- time-agnostic solution? Is the obtained solution close to the most effective solution provided by scheduled traffic? In order to exhaustively evaluate the performance of LB-HTA, we consider as benchmark the solution obtained under the well-known Scheduled Traffic model (TI-ST) and also under an approximated, but more effective, approach for traffic scheduling, called Time- Variant Scheduled Traffic (TV-ST). For both TI-ST and TV-ST, Integer Linear Program (ILP) formulations are proposed and results compared with dynamic routing algorithms.

In a wavelength-division-multiplexing (WDM) optical network, backup reprovisioning (BR) provides a means to improve survivability (by protecting against multiple concurrent potential failures) and to utilize the available resources more efficiently. In particular, global backup reprovisioning (GBR), i.e. the reprovisioning involving the totality of the backup capacity has been demonstrated to be almost as capacity-effective as other re-optimization techniques involving primary paths. Unfortunately, existing ILP and heuristic solutions for the GBR problem are very time consuming and unsuitable to be adopted in time-sensitive network scenarios (e.g., subject to frequent network-status changes and/or connection-provisioning setup- time constraints). In this paper, we first analytically evaluate how the GBR computational time may impact on the connection provisioning process. Then, we propose a fast BR procedure based on simulated annealing (SA) which significantly decreases the computational time with respect to existing heuristics while still achieving very high resource efficiency.

Protection techniques for optical networks mainly rely on pre-allocated backup bandwidth, which may not be able to provide full protection guarantee when multiple failures occur in a network. To protect against multiple concurrent potential failures and to utilize the available resources more efficiently, strategies such as backup reprovisioning rearrange backups of protected connections after one failure occurs or, more generally, whenever the network state changes, e.g., when a new request arrives or terminates. Recently, new solutions for automatized management in Optical networks promise to allow customers to specify on-demand the terms of the service level agreement (SLA) to be guaranteed by the service provider. In this paper we show that is possible to further reduce the capacity requirements of backup reprovisioning techniques exploiting the knowledge, among the other service level specifications (SLS), of the connection holding-time. Our main contributions are as follows. First, we prove that the problem of backup reprovisioning for all the lightpaths requiring shared-path protection under a current network state is NP-complete. Second, we provide a mathematical ILP model of the reprovisioning problem considering the additional holding-time information. Third, since the problem is NP-complete and we can not efficiently rely on exact approaches, a new global reprovisioning algorithm called Ph-GBR is proposed which can significantly reduce the resource overbuild exploiting the information about connection durations. By means of simulative experiments, we compare capacity requirement and computational complexity of Ph-GBR to those of another holding-time unaware, yet efficient algorithm, called GBR, considering a dynamic traffic in a wavelength-convertible WDM mesh network scenario.