Efficient algorithms for fault-tolerant communication in optical WDM networks

We study the problem of providing real-time service to hard and soft real-time messages in wavelength division multiplexing (WDM) optical networks. We propose and evaluate a set of scheduling algorithms which schedule message transmissions in single-hop WDM passive star networks based on specific time constraints. We compare the performances of our algorithms with that of the typical WDM scheduling algorithm which does not consider the time constraint of the transmitted messages by discrete-event simulations and an analytical model. We find that the improvement on real-time performance can be attributed to our scheduling algorithms where the time constraint of messages has been taken into consideration. This study suggests that when scheduling real-time messages in WDM networks, one has to consider not only the problem of resources allocation in the network but also the problem of sequencing messages based on their time constraints.

To utilize the wavelength resources of Internet protocol (IP) over wavelength division multiplexing (WDM) optical networks, a multi-constrained multicast traffic grooming algorithm is proposed in this paper. This algorithm can achieve multicast traffic grooming in IP over WDM optical networks under multi-constraints, including the number of optical transceivers, wavelength conversion capability and wavelength splitting capability. We simulated the traffic grooming algorithm using the topology of GEANT. Emulation results show that our algorithm has a lower blocking proportion compared with the multi-hop traffic grooming algorithm, which can achieve multicast traffic grooming more effectively.

In a many-to-many session, a participant distributes and receives traffic flows to/from all others in the same session. It is desirable to achieve both high resource utilization and low power consumption when such sessions are provisioned. In wavelength division multiplexing (WDM) optical networks, traffic grooming has been widely applied as the key technology for aggregating sessions to improve resource utilization. However, the current many-to-many grooming approaches, the lightpath circle and hubbed light-tree, do not make an effort to reduce the power consumption of many-to-many sessions. In this paper, we formulate the green routing and aggregation of many-to-many sessions problem and prove its NP-completeness. For problem solving in WDM optical networks, we apply a rational combined method of lightpaths. Both an integer linear programming-based approach and a novel graph-based heuristic are devised. We further provide an illustrative comparison between our heuristic and the existing benchmarks in terms of power consumption. Extensive simulation results demonstrate that, compared with the benchmarks, our heuristic improves the average power efficiency in the range of 13-19%.

In this paper, we compare performance of fixed-grid Wavelength Division Multiplexing (WDM) and Elastic Optical Networks (EONs) in dynamic provisioning of many-to-many (m2m) flows. Currently, with a growth of services relying on many-to-many communication paradigm such as distributed computing, inter-Data Center communication, content delivery networking or other requiring high-bandwidth in group communication, it is vital to deliver new solutions facilitating these demanding transmissions. Therefore, the authors investigate provisioning of m2m traffic in high-performance optical networks. This work focuses on dynamic Routing and Wavelength Assignment (RWA) problem in WDM networks as well as Routing and Spectrum Allocation (RSA) problem in EONs for m2m flows using replicated communication through auxiliary rendezvous servers.

We address the issue of inapproximability of the wavelength assignment problem in wavelength division multiplexing (WDM) optical networks. We prove that in an n-node WDM optical network with m lightpaths and maximum load L, if NP ≠ ZPP, for any constant δ>0, no polynomial time algorithm can achieve approximation ratio n1/2−δ or m1−δ, where NP is the class of problems which can be solved by nondeterministic polynomial time algorithms, and ZPP is the class of problems that can be solved by polynomial randomized algorithms with zero probability of error. Furthermore, the above result still holds even when L=2. We also prove that no algorithm can guarantee the number of wavelengths to be less than $$(\sqrt{n}/2)L$$ or (m/2)L. This is the first time inapproximability results are established for the wavelength assignment problem in WDM optical networks. We also notice the following fact, namely, there is a polynomial time algorithm for wavelength assignment which achieves approximation ratio of O(m(log log m)2/(log m)3). Therefore, the above lower bound of m1−δ is nearly tight.

In optical wavelength-division multiplexing (WDM) networks, traffic can be very “bursty” at a fine time scale, even though it may seem to be smooth at coarser scales (e.g., Poisson or Poisson-related traffic). This paper analyzes the instantaneous characterization of Poisson traffic at a fine time scale. The analysis shows that the irregular oscillation of the instantaneous traffic load and the occurrence of blockings in a light-loaded network are highly correlated. Specifically, most blockings occur concentratively at the peaks of the instantaneous load. In some other time, network resources may not be sufficiently utilized. To make better utilization of network resources, a novel wavelength-buffering (WB) scheme is proposed for the first time in this paper. By reserving a portion of resources in a “wavelength buffer” under light loading and releasing them when the load goes up, a number of blockings brought by the oscillation of the traffic load can be avoided. Simulation results show that compared with other schemes such as adaptive routing, wavelength conversion (WC), and rerouting, the novel wavelength-buffering scheme achieves significantly better performance with respect to the network utilization and overall blocking probability.

In all-optical Wavelength Division Multiplexing (WDM) technique, data contention is an inevitable challenge. For reliable data transmission, contention resolution is very much essential. There are different contention resolution techniques that are used in optical WDM network. In this paper, wavelength converter is used for contention resolution in optical WDM network. Here Semiconductor Optical Amplifier (SOA) is used to implement wavelength converter based on a special third-order nonlinear susceptibility phenomenon of silica fiber, called Four-Wave Mixing (FWM) technique. Realization of wavelength converter is done for two different sets of WDM networks. Performance of the wavelength converter was estimated in terms of number frequencies generated, number of new wavelength generated, its corresponding power, etc. Result shows that four-wave mixing is a very effective technique to generate new wavelengths at the output to overcome the problems due to contention in an optical WDM network. OptiSystem of Optiwave is used to design schematic layout for the wavelength converter using SOA.

The widespread deployment of wireless telecommunication networks and growing Internet traffic globally leads to a substantial increase in signal traffic demands in fiber optic networks. This demand surge places significant pressure on the survivability of optical networks, specifically when faced with fiber cable failures that prevent failed optical fibers from satisfying connection requests. To address this challenge, in this paper, we consider integrated planning of regenerator installation, optical connection routing, and wavelength assignment (RWA) for wavelength division multiplexing (WDM) optical networks under link failures. To the best of our knowledge, we are the first to consider such an integrated problem. We minimize the number of backup regenerators required to fulfill all connection requests under all potential link failures while accounting for the wavelength and routing constraints. We formulate the problem as an integer program, while its size exponentially increases with the network size by nature. To solve large-scale instances for practical uses in the industry, we propose efficient algorithms to generate near-optimal solutions that are practically implementable. We perform extensive numerical experiments to demonstrate the effectiveness of our approach in solving real-world instances provided by our industry partners. The results show that our approach can efficiently obtain high-quality solutions while ensuring a minimal increase in backup regenerators as the network grows. Our solutions also offer valuable insights into planning a cost-effective and reliable fiber optic network for network operators.

In this paper, we investigate problems related to optical wavelength division multiplexing (WDM) networks that use the virtual concatenation (VCAT) mechanism of synchronous optical network (SONET) technology. VCAT, an end-to-end mechanism, allows SONET based optical WDM networks to carry traffic in

The manycast communication paradigm is becoming increasingly important in today’s optical networks, wherein connection requests from a source node can be routed to a subset of a candidate destination set. This flexibility in choosing different destinations from a larger candidate destination set helps improve the network performance. In this paper, we develop a new analytical model to compute the network-wide blocking performance for generalized manycast routing and wavelength assignment (MRWA) in optical wavelength division multiplexed (WDM) networks. Specifically, we calculate the request blocking on full-wavelength convertible optical networks based on Markov chains and conditional probability analysis. Performance results show that our model is accurate and is verified by extensive simulation results.

In anycast, connection requests are routed to one of multiple destination candidates, thus helping improve the overall acceptance of service requests in the network when compared to traditional unicast. In this paper we develop a new analytical model to compute the network-wide blocking performance for anycast routing and wavelength assignment (ARWA) in wavelength division multiplexing (WDM) optical networks using the reduced-load fixed-point approximation analysis. This model is based on conventional queuing theory for loss systems combined with a joint probability analysis of the anycast service alternatives. Performance results show that our model provides good accuracy compared to simulation results.

In order to provide good quality of survivability in the WDM (Wavelength Division Multiplexing) optical network and keep the network load in a good condition, a game based muti-domain protection scheme is proposed in this paper. Game theory, Nash equilibrium and Pareto Optimality of micro-economics are introduced in this scheme for considering benefits of both users and network providers to guarantee the reasonability of survivable routing and achieve all-win. Finally, the proposed protection scheme is implemented by simulation, and the experiment results show that the proposed scheme can reach these design goals.

This chapter discusses the causes of impairments in the optical network and how one takes them into account in the design, followed by the survivability issues in optical networks. It outlines the basic concepts of survivability and different protection and restoration schemes used in optical networks. Survivability can be provided in different layers in network: logical layers and optical layer. The fault‐management schemes in each layer have their own functionalities and characteristics. The chapter also discusses the survivability in the multilayer wavelength division multiplexing (WDM) optical networks. The protection techniques in the synchronous optical network and synchronous digital hierarchy networks are briefly described, which are still used in many of the current protocols in the WDM networks. It looks at protection functions in the optical layer and discusses how protection functions in the different layers of the network can work together.

Solving multi-objective routing and wavelength assignment in WDM network using hybrid evolutionary computation approach

As a result of the rise of Cloud and Grid computing, network operators are requested to improve their resource provisioning systems. In such scenarios, advance reservation (AR) and immediate reservation (IR) are gaining importance. While the former is capable of delivering low connection blocking for delay-tolerant applications, the latter is used by delay-sensitive ones. Even when both IR and AR requests share the same network substrate, service differentiation is needed. Additionally, under network resources partitioning, not only can the overall network capacity be under-utilized, but service differentiation can also be degraded. In this paper, we assess hybrid IR/AR sharing and partitioning mechanisms in optical wavelength-division multiplexing (WDM) networks, and propose efficient schemes for providing relative quality of service (QoS) differentiation among traffic classes. In order to overcome the poor resource utilization of strict partitioning, we develop and evaluate a preemption-based flexible partitioning framework aiming to provide relative QoS in hybrid IR/AR environments still supporting resource partitioning. Two preemption policies are proposed: switch first then preempt (SFTP) and preempt first then switch (PFTS). Through extensive simulations, we show that the proposed flexible partitioning framework can improve resource utilization, lower the overall blocking, and achieve well-differentiated relative QoS compared to strict partitioning.