Network protection is a key solution and an important component in the requirements of virtualization over elastic optical networks (EONs). In this paper, we examine the significance of network virtualization with survivability design against single-link failures and shared risk link groups (SRLG) under dedicated protection and bandwidth squeezing schemes. We study an optimization version of the routing, modulation and spectrum allocation (RMSA) problem with the goal of maximizing the revenue from the accommodated requests of the virtual optical networks (VONs) or slices. We present a Mixed Integer Linear Programming (MILP) formulation for the problem and evaluate some numerical results. We suggest a heuristic that utilizes techniques of decomposition of the problem, which can be employed to obtain a near optimal solution that has a per instance guarantee on the closeness to the optimal solution.

Elastic optical network (EON) is fast becoming a key solution for designing optical network with better usage of spectrum resources or other objectives of interest to tenant and/or operators. A primary concern of EONs is to protect the network against failures of its elements, because this kind of event can provoke the loss of substantial amount of traffic. In this paper, we propose a new mixed integer linear programming (MILP) formulation for protecting the network traffic against multiple link failures. The key idea is to use bandwidth squeezing together with grooming capability to provide few extra traffic for protection and guarantee a minimum bandwidth for each source-destination node pair under multiple failure events. The proposed formulation solves the virtual topology design problem jointly with the grooming, routing, modulation and spectrum allocation (RMSA) tasks. Due to the non-deterministic polynomial time (NP-hard) nature of the proposed MILP formulation, a heuristic strategy (referred to as two-step MILP) for large networks is also proposed. The solutions and performance of the proposed MILP formulation and two-step MILP analyzed through case studies in a small network. In addition, the performance of three large networks is assessed for cases scenarios where connections are under different service-level agreement (SLA). In view of proposed formulation and two-step MILP, it is possible to identify the configurations that ensure better usage of spectrum resources with different kinds of protection against single or multiple link failures.

Crankback re-routing extensions can offer significant improvements in the successful setup of Label Switched Paths (LSPs) by allowing new retries on alternate paths that circumvent blocked links or nodes. These extensions can be incorporated into a fully-distributed algorithm based on Ant Colony Optimization metaheuristics, taking advantage of its self-adapting, emergent behavior. By comparing with traditional fixed-alternate re-routing mechanisms, simulations have demonstrated that the proposed algorithm can efficiently mitigate lightpath blocking, both during normal operation and in case of network failure, by locally repairing failed LSP setups due to blocked/failed resources.

Most studies about Optical Burst Switched (OBS) networks have assumed availability of full wavelength conversion throughout the network. In an optical network with full wavelength conversion capability, every output on each node is provided with a wavelength converter, resulting in the lowest bound for blocking probability. However, full wavelength conversion capability requires a large number of wavelength converters, which is, and will remain, quite expensive in the foreseeable future. Therefore, it is expected that conversion capability will be limited and only sparsely deployed. In this work we apply to OBS networks the main architectures for wavelength conversion proposed for circuit switched networks. These architectures operate with limited wavelength conversion capability. We also investigate the cost benefit and the gain factor related to full complete wavelength conversion for each architecture. In addition, we propose a new methodology to define the number of wavelength converters in order to achieve the best cost benefit, regardless of the traffic load.

In this paper, we propose an ACO-based algorithm that can adaptively balance the network load to mitigate congestion, and hence reduce the overall loss of packets in an OPS network. In addition, the proposed algorithm is fault-tolerant, with the recovery from a failed link or node starting even before detection and localization of the failure event. Since both routing and restoration rely on pheromone levels laid by ant-like agents, any failure will be promptly perceived by some ants, which will then try to circumvent the affected part of the network, thus adapting the routing to the new topology.

The use of a manageable optical network is an important requirement for the new advanced data-intensive grid applications that begin to emerge on the e-Science field. In this paper, we propose an ACO-based algorithm that can provision on-demand and dynamically lightpaths on a grid system. Indeed, the proposed algorithm can schedule jobs by discovering processing and network resources on the grid, assigning the job to a specific system and executing the job. This is achieved with the help of an integrated GMPLS control plane, which allows both resource monitoring and management of networking resources.

In this paper we present a method for calculating the exact blocking probability in WDM rings with full, ubiquitous wavelength conversion under Poissonian, homogeneous traffic with any spatial profile. A new scalable procedure is presented to derive the normalization constant of the Erlang's classical model for ring networks. In the same analytical framework, formulas are derived for the utilization rate and blocking probability of the ring.

Physical layer impairments may require highly complex implementations of the control plane in dynamic networks with quality of service (QoS) constraints. In order to alleviate this problem, we propose that dynamic wavelength assignment should be based on the elementary first-fit (FF) algorithm using off-line optimized priority lists. It is shown that this may significantly reduce the effects of physical impairments with no additional computational cost for the control of dynamic networks. A simple metric is proposed to evaluate optical QoS taking the performance of the network as a whole. Different heuristics are presented and evaluated. Results show that there are particular lists capable of reducing in four orders of magnitude the probability of FWM impacting network performance.

In this paper we present an exact analytical model for the FIFO delay-line buffer in an asynchronous network scenario considering that packets arrive to the buffer following any inter-arrival time process. The model enables us to study the impact that different inter-arrival distributions have on the buffer performance and design process. The accuracy of the model is compared with simulations for deterministic, uniform, exponential and Weibull inter-arrival time distributions. Then, the effects of these distributions, input load and delay line spacings on the buffer performance are investigated.

In this paper we address the problem of providing delay-line buffers with the capability to differentiate services in optical packet switching networks. A simple and efficient policy for acceptance and discarding of optical packets is proposed and its analytical model is presented. The model enables the exact calculation of packet loss probability and average delay for Poisson arrivals and any packet length distribution. The buffer performance as predicted by the model is compared with simulations for Pareto packet length distribution.

The paper introduces a new analytical approach for estimating blocking probabilities in linear all-optical networks. The assumptions of the classical Lee approximation are discussed and their effects are evaluated. The paper proposes a better substitute for the independent link assumption. The new assumption takes all active paths, as well as all free links, as independent objects on the network topology. The new model is shown to generate estimates that exactly fit the blocking probabilities obtained through simulations on linear topologies using Poissonian, single-wavelength spatially homogeneous traffic. Finally, the independent wavelength assumption is also evaluated.

The performance improvements imparted by first-fit wavelength assignment algorithms on blocking WDM rings without wavelength conversions are investigated. Computationally inexpensive algorithms are derived for the minimization of: (a) the blocking probability immediately after each assignment; and (b) the increment of the channel blocking probability at the assigned wavelength. Their performance is evaluated by simulation and compared with the basic random and priority algorithms.

High-speed, photonically amplified digital links have their performance limited by a complex combination of intersymbol interference, laser nonlinearities, and signal-dependent noise. Determination of the worst case patterns cannot rely on the classical eye diagram anymore, but requires more sophisticated computational metrics, which are discussed. A new approach to performance evaluation of these systems is based on error-rate patterns that have been proposed before as a generalization of the classical eye-diagram concept in an experimental environment. We discuss the extension of this approach to the computer-aided modeling, analysis, and design (CAMAD) of these communication links.

Upper bounds on the rate of codes in DC-constrained spaces are derived for imbalances 3, 4, and 5. The new bounds are based on the identification and size calculation of the minimal Hamming spheres. A new combination of the Hamming and Plotkin (1960) bounds for constrained spaces is obtained.>

This paper makes a theoretical assessment of the performance impairments that may be caused on PCM lines by the use of different timing extraction bandwidths in tandem. Two basic situations are examined: 1) random transmitted pattern, and 2) transition between two repetitive patterns. In both cases, the analysis of jitter propagation and acceptance indicates that there is a limited degree of bandwidth inconsistency that may be tolerated. The amount of tolerable inconsistency is derived in both cases, according to different criteria that are established for convenience in each case. The effect of systematic line jitter on the correlation between a repeater performance in the field and in bench tests is also discussed. The study is based on a well-known model of jitter propagation introduced by Byrne et al. [1]. The general conclusion of the paper is thatQ-factor variations in a PCM line should be kept lower than a factor of two in order to avoid errors during pattern transitions and lower than 1.5 in order to avoid noise immunity loss.