We consider virtual optical network (VON) provisioning over a flexible-grid multi-domain optical network with the objective of minimizing total network cost, including the cost of transponders, regenerators, and spectrum. We propose a three-step heuristic algorithm that addresses the issues of domain selection, topology aggregation, and routing, modulation format, and spectrum assignment (RMSA) when mapping virtual optical links onto multi-domain physical optical links. We propose a domain selection technique that attempts to minimize the number of inter- domain virtual optical links. We then suggest a topology aggregation (TA) technique to exchange intra and inter-domain information between domains, and propose a method for RMSA over the aggregated topology. Numerical results show that our heuristic approach is effective in reducing total network cost.

In this paper, we study a new optical network paradigm, where statistical sharing is supported in optical networks. This new paradigm is motivated by the recent revolution of Software Defined Optics (SDO). Software defined variable-bandwidth transponders can support variable data rates for a single connection, i.e. base rates and peak rates. Guaranteeing the peak rates for all the connections simultaneously requires the spectrum for all circuits to be provisioned for peak rates, leading to a large amount of bandwidth usage with low utilization. However, if resources are provisioned for the base rate of each connection, with some shared spectrum resources set aside to allow a fraction of these connections to dynamically switch to their peak rates, then spectrum resources can be allocated more efficiently, allowing a greater number of connections to be accommodated. We reserve a fraction of the spectrum resources for provisioning of base rate of the dynamic traffic while the rest of the spectrum resources are reserved for peak rate, allowing statistical sharing. Our goal is to minimize the blocking of the arriving connection requests, while at the same time maximizing the chance that existing connection requests are able to switch from base rate to peak rate. These two goals conflict with each other; therefore, we need to find a trade-off based on the amount of spectrum resources set aside for the peak rate, and based on the routing, modulation format selection, and spectrum allocation (RMSA) scheme. Our evaluation can help network operators to determine the amount of spectrum that requires to be set aside for peak rates in order to maximize revenue.

In this paper, we consider the problem of routing, modulation, and spectrum assignment (RMSA) for data- flow transfers in elastic optical networks. We design a two-dimensional resource model, in which each data transfer with known data size can be assigned a rectangular block of resources that spans both the spectrum and time dimensions. Furthermore, the dynamic spectral resource allocation problem in elastic optical networks is simplified to the two-dimensional rectangle packing problem. We design a three-tuple for each rectangle placement, and develop a dynamic heuristic algorithm, Best Rectangle Fit (BRF), to efficiently schedule requests while minimizing fragmentation in both spectrum and time domains. We simulate the proposed algorithm, and the results show that the proposed RMSA algorithm (BRF) can greatly decrease blocking probability and increase spectrum utilization.

In this paper, we study a new paradigm in optical networking in which optical spectrum is allowed to be statistically shared between optical circuits, allowing the oversubscription of optical links. We propose a probabilistic model which estimates the capacity requirements for the optical networks under a certain density of statistical sharing. Simulation results indicate that our proposed model can help with network design decisions, such as admission control and capacity and bandwidth allocation in elastic optical networks.

In this paper, we aim to minimize the total network cost in flexible-grid optical networks with multiple line rates. Besides transponder cost, regenerator cost, and shared infrastructure cost, the cost of regenerator sites is also considered. We first provide the problem definition and formulate the problem as an integer linear program (ILP). We also propose a heuristic algorithm considering both selection and placement of equipment to minimize the total network cost. Simulation results show the heuristic algorithm results in up to 28% cost saving, with no significant increase in spectrum usage.

In this paper, we study the problem of regenerator pool site selection for mixed line rate optical networks (MLR-RPSS), with the objective of minimizing the number of regenerator pool sites for a given set of requests. We first provide the problem definition of MLR-RPSS and show that the MLR-RPSS problem is NP-complete. We then present four algorithms, named Independent algorithm, Sequential algorithm, MLR-combined algorithm, and Weighted MLR-combined algorithm. The performance of the algorithms is compared via simulation and results show that the Weighted MLR-combined algorithm has better performance in most cases. Also, when network load is high, the minimum number of regenerator pool sites will approach a certain limit, and some specific nodes will be more likely to be selected as regenerator pool sites.

This paper investigates the subject of reliability via two link-disjoint paths in mesh networks. We address the issues of how reliable two-path protection can be and how to achieve the maximum reliability. This work differs from traditional studies, such as MIN-SUM, MIN-MAX, and MIN-MIN, in that the objective in this paper is to maximize the reliability of the two-path connection given the link reliability, or equivalently, to minimize the end-to-end failure probability. We refer to this problem as MAX-REL. Solving MAX-REL provides 100% protection against a single failure while maximizing the reliability regardless of how many link failures occur in the network. We prove that this problem is NP-complete and derive a corresponding upper bound, which is the theoretical maximum reliability for a source-destination pair, and a lower bound, which is the worst case of the proposed algorithm. The time efficiency of the algorithms is analyzed, and the performance of the algorithms is evaluated through simulation. We demonstrate that our heuristic algorithms not only achieve a low computing complexity, but also achieve nearly equivalent performance to the upper bound.

Standard advance reservation (SAR) mechanisms have been proposed as a way to provision resources for high-bandwidth applications in order to provide QoS guarantees to users; however, variations in the available bandwidth on different links over time can lead to situations in which standard advance reservations must be pushed further into the future, leading to higher end-to-end delays. We introduce the concept of time-shift advance reservation (TSAR), which improves bandwidth utilization by making use of delay elements at intermediate nodes within the network. We describe the TSAR architecture and discuss various design and implementation issues. The routing and scheduling problem in TSAR networks is defined, and a routing and scheduling algorithm is proposed. We find that TSAR with the proposed algorithm minimizes latency for each request and reduces request blocking compared to standard advance reservation and immediate reservation approaches.

In this paper, we focus on the problem of effectively supporting a large number of small group multicasts in optical burst switched (OBS) networks. We first propose a multicast scheme for small group multicast in OBS networks. To reduce burst loss due to potential burst contentions, a deflection routing scheme for multicast is proposed. We then develop an analytical model to evaluate the performance of the multicast scheme and the deflection routing scheme. To the best of our knowledge, this is the first analytical model proposed for the problem of multicast with deflection routing. The model is very general in the sense that it can handle unicast traffic, multicast traffic, and the mixture of unicast and multicast traffic, with or without deflection routing. The analytical model is verified through simulations. Numerical results show that the analytical model is accurate, and that, under low or medium network load, deflection routing for multicasting can significantly reduce burst loss while slightly increasing burst delay.

In this paper, we investigate the problem of survivable grooming for anycasting over wavelength division multiplexing (WDM) networks. Anycasting is a communication paradigm in which a source node sends data to any one out of multiple candidate destinations. In WDM networks, the standard anycasting problem involves the establishment of a connection from the source to any one destination with the objective of minimizing the resources used. In order to provide survivability, the problem can be extended to find both a connection to a primary destination and a connection to a backup destination. The connections, which may require an amount of bandwidth that may be less than the bandwidth of an entire wavelength, can be groomed with other connections in the WDM network. We propose an auxiliary graph approach to solving the survivable grooming problem for anycasting in WDM networks, and we propose three different protection approaches for providing different degrees of survivability against link failures and destination failures. The effectiveness of the proposed schemes is verified through simulation.

In this paper, we discuss for the first time the issue of supporting manycasting service over optical burst- switched (OBS) networks. One of the primary challenges in providing manycasting service over OBS networks is to reduce data loss due to burst contentions. We propose two new schemes, static over-provisioning (SOP) and dynamic membership (DM), to alleviate this data loss problem. The proposed schemes take into consideration the specific properties of manycasting, and the schemes may complement existing contention resolution schemes. The effectiveness of the proposed schemes is verified through simulation.

This paper investigates the path protection problem in mesh networks under multiple generic risks. Disjoint logical links may fail simultaneously if they share the same components in the physical layer. Each component is associated with one or more risks, and each risk may involve more than one logical link. This property introduces failure dependence for different logical links in layered networks. In this paper, the network failure scenario is under multiple risks. Each risk is a generic failure event, which may result in single-link failure, multiple-link failure, or all-link failure associated with a node (node failure). The objective aims at minimizing the end-to-end failure probability, or equivalently, maximizing the survivability by using two disjoint paths under multiple generic risks. The problem is shown to be NP-complete, and a novel graph model and corresponding heuristic algorithm are proposed. The time efficiency of the algorithms is analyzed, and the simulation results show that, compared to some existing diverse routing algorithms, the proposed heuristic algorithm can significantly improve the survivability at the cost of higher hop distance.

We define and investigate the problem of multi-resource manycast over optical burst switched (OBS) networks for supporting distributed computing applications. In multi-resource manycast, each destination has multiple computing resources, and each source generates requests that require multiple resources. For a given request, the problem is to select a set of destinations that have the required available resources and to And routes to these destinations. This problem differs from the traditional manycast problem in that different destinations have different resource availability. The objective is to minimize the resource blocking rate, which results from burst contention in the OBS network and from resource unavailability at the destinations. We investigate various approaches to implement multi-resources manycast over OBS networks, and verify the effectiveness of the proposed schemes through simulation.

In this paper, we focus on the problem of effectively supporting a large number of small group multicasts in optical burst switched (OBS) networks. We first propose a multicast scheme for small group multicast in OBS networks. To reduce burst loss due to potential burst contentions, a deflection routing scheme for multicast is proposed. We then develop a generic analytical model to evaluate the performance of the multicast scheme and the deflection routing scheme. To the best of our knowledge, this is the first analytical model proposed for the problem of multicast with deflection routing. The analytical model is verified through simulations. Numerical results show that the analytical model is accurate and that deflection routing can significantly reduce burst loss probability while slightly increasing burst delay.

This paper investigates the problem of finding two link-disjoint paths in mesh networks. Different from traditional studies, such as MIN-SUM, MIN-MAX, and MIN-MIN, the objective in this paper is to minimize the end-to-end failure probability, or equivalently, maximize the survivability under multiple link failures. We refer to this problem as MAX-SURV. Solving MAX-SURV provides 100% protection against single failure while maximizing the survivability under multiple failures. We prove that this problem is NP-complete, and we propose a heuristic algorithm for finding a solution. The corresponding upper bound and lower bound for given networks are also found. The time efficiency of the algorithms is analyzed, and the performance of the algorithms is evaluated through simulation.