Survivability of internet services is a significant and crucial challenge in designing optical networks. A robust infrastructure and transmission protocols are needed to maintain communication, despite the existence of one or more failed components on the system. Here, we present a generalized approach to tolerate any set of failure scenarios to the extent network users can still communicate with the remaining components, where a scenario is an arbitrary set of links in a non-operational state. We propose a joint solution to assess the survivability problem. The issues to be solve simultaneously are as follows: the set of primary routes, a collection of alternate routes associated with each failure scenario, and the capacity required on the network to allow communication between all users, in spite of any considered failure scenario, while satisfying for each user a specific predefined quality of service threshold, defined in the Service Level Agreement (SLA). Numerical results show that the proposed approach not only enjoys the advantages of low complexity and ease of implementation, but it is also able to achieve significant resource savings compared to existing methods. The savings are higher than 30% on single link failures and more than 100% on two simultaneous link failures cases or in more complex failure scenarios. INDEX TERMS Network capacity, optical networks, quality of service, routing, survivability.

Survivability of internet services is a significant and crucial challenge in designing future optical networks. A robust infrastructure and transmission protocols are needed to handle such a situation so that the network users can maintain communication despite the existence of one or more failed components on the network. For this reason, in this work, we present a generalized approach to tolerate any set of failure scenarios, to the extent the user can still communicate with the remaining components, where a scenario corresponds to an arbitrary set of links in a non-operational state. To assess the survivability problem, we propose a joint solution to the problems listed next. We show how to find: a set of primary routes, a set of alternate routes associated to each failure scenario, and the capacity required on the network to allow communication between all users, in spite of any failure scenario, while satisfying for each user a specific predefined quality of service threshold, defined in the Service Level Agreement (SLA). Numerical results show that the proposed approach not only enjoys the advantages of low complexity and ease of implementation but is also able to achieve significant resource savings compared to existing methods. The savings are higher than 30% on single link failures and more than a 100% on two simultaneous link failures scenarios and in more complex failure scenarios.

This article gives an insight on the importance to assign a different capacity to each network link and to tighten the Quality of Service (QoS) provision in the network, in dynamic WDM Optical Networks with wavelength continuity constraints. In the text, several examples illustrate the performance of different strategies. The usual procedure to compute the number of wavelengths of each network link consists of choosing the same capacity to each link on the network. This decision is selected, in most cases, by simplicity and simulation limitations. Notwithstanding, there are no technical motives to force a uniform capacity on the network. In consequence, we analyze the impact on the network capacity of designating the minimum amount of wavelengths to each network link, while satisfying each user QoS requirement. Moreover, despite the chosen dimensioning strategy, it is usual to offer a much better QoS than requested for some users, with the corresponding waste of resources. We can amend this issue by limiting which wavelengths are available to each user according to its particular QoS constraint. This technique, known as Wavelength Grouping, seeks to provide to each user a QoS level closer to the one defined in the Service Level Agreement. By doing so, it is possible to reduce the network capacity needed to allow communication to its user, or diminishing the network blocking probability for a given wavelength capacity. In spite of the usual approach, in this work, we demonstrate that a nonuniform dimensioning strategy and a tighten QoS provision allows to save significant networks capacity, while simultaneously provisioning to each user the QoS established in its Service Level Agreement. This fact is very relevant nowadays, where an impending capacity crunch in optical networks is an important issue.