Abstract—The two protection methods wrapping and steering used in IEEE 802.17 resilient packet ring (RPR) provide fast but very inefficient and limited network failure recovery. Due to the increased length of the backup path, RPR suffers from high traffic loss, a decreased throughput-delay performance, and the lack of resilience against multiple link and/or node failures. To achieve an improved resilience, interconnecting a subset of the ring nodes by means of a dark-fiber single-hop star wavelength division multi-plexing (WDM) network is proposed. In doing so, the ring network is divided into separate domains, each being fully recoverable from a single link or node failure without losing full network connectivity. A novel hybrid fault recovery technique, termed pro-tectoration, is proposed and examined by means of probabilistic analysis and simulation in terms of stability, channel utilization, and throughput-delay performance. The proposed protectoration technique 1) combines the fast recovery time of protection and the bandwidth efficiency of restoration, 2) provides full recovery from multiple link and node failures, 3) builds on both wrapping and steering protection methods of RPR and, thus, allows for an evolu-tionary upgrade of existing RPR networks, and 4) does not require the convergence of routing protocols in response to failures and, thus, improves the routing stability and network availability. Nu-merical investigations in this paper show that the location of fail-ures has a strong impact on the network performance. For a given failure location, the protectoration technique is able to accommo-date multiple ring failures without significant performance loss.

Abstract — As networks grow in size and complexity, both the probability and the impact of failures increase. The pre-allocated backup bandwidth, which has been widely investigated in the literature, may not be able to provide full protection guarantee when multiple failures occur in a network. In this study, we consider multiple concurrent failures where concurrent means that a new failure occurs before a previous failure is repaired. To combat the effect of multiple concurrent failures, new backups can be reprovisioned after one failure such that the next potential failure can be handled effectively and efficiently. We consider dynamic traffic where a pair of link-disjoint primary and backup paths is provisioned when a new connection request arrives. After a failure occurs, the affected connections switch traffic from their primary paths to backup paths. To protect against next potential failure, we reprovision new backups

Abstract—An evolutionary algorithm (EA) can be used to tune the control parameters of a construction heuristic to an optimization problem and generate a nearly optimal solution. This approach is in the spirit of indirect encoding EAs. Its performance relies on both the heuristic and the EA. This paper proposes a three-phase parameterized construction heuristic for the sharedpath protection problem in wavelength division multiplexing networks with shared-risk link group constraints and applies an EA for optimizing the control parameters of the proposed heuristics. The experimental results show that the proposed approach is effective on all the tested network instances. It was also demonstrated that an EA with guided mutation performs better than a conventional genetic algorithm for tuning the control parameters, which indicates that a combination of global statistical information extracted from the previous search and location information of the best solutions found so far could improve the performance of an algorithm. Index Terms—Estimation of distribution algorithms (EDAs), evolutionary algorithm (EA), guided mutation, hyperheuristics, memetic algorithm (MA), network protection, shared-risk link group (SRLG). I.

When reliability is a major concern in optical WDM networks, Shared Path Protection (SPP) schemes offer the potentially appealing feature of requiring fewer network resources than their counterpart Dedicated Path Protection (DPP) schemes. However, while sharing increases resource utilization, it reduces end-to-end reliability of connection demands. Moreover, the evaluation of connection demand reliability is easy with DPP: it depends only on the components used to route the connection demand. It is more complex with SPP, as sharing of protection resources introduces dependencies among different connection demands, and the reliability of a connection depends on the failure of components that are not used to route the connection demand as well. The possible occurrence of multiple failures exacerbates this problem significantly. For this reason, the simpler DPP schemes are often chosen, even though, as a result, network resources are not efficiently used.

This paper investigates the problem of dynamic survivable lightpath provisioning against single node/link failures in optical mesh networks employing wavelength-division multiplexing (WDM). We unify various forms of segment protection into generalized segment protection (GSP). In GSP, the working path of a lightpath is divided into multiple overlapping working segments, each of which is protected by a node/link disjoint backup segment. We design an efficient heuristic which, upon the arrival of a lightpath request, dynamically divides a judiciously-selected working path into multiple overlapping working segments and computes a backup segment for each working segment while accommodating backup sharing. Compared to the widely-considered share-path protection scheme, GSP achieves much lower blocking probability and shorter protection-switching time for a small sacrifice in control and management overhead. Based on generalized segment protection, we present a new approach to provisioning lightpath requests according to their differentiated quality-of-protection (QoP) requirements. We focus on one of the most important QoP parameters—namely, protection-switching time— since lightpath requests may have differentiated protectionswitching-time requirements. For example, lightpaths carrying voice traffic may require 50-ms protection-switching time while lightpaths carrying data traffic may have a wide range of protection-switching-time requirements. Numerical results show that our approach achieves significant performance gain which leads to a remarkable reduction in blocking probability. While our focus is on optical WDM network, the basic ideas of our approaches can be applied to Multi-Protocol Label Switching (MPLS) networks with appropriate adjustments, e.g., differentiated bandwidth granularities.

(Communicated by Yiju Wang) Abstract. As a generalization of the traditional path protection (PP) scheme in WDM networks where a backup path is needed for each active path, the partial path protection (PPP) scheme uses a collection of backup paths to protect an active path, where each backup path in the collection protects one or more links on the active path such that every link on the active path is protected by one of the backup paths. While there is no known polynomial time algorithm for computing an active path and a corresponding backup path using the PP scheme for a given source destination node pair, we show that an active path and a corresponding collection of backup paths using the PPP scheme can be computed in polynomial time, whenever they exist, under each of the following four network models: (a) dedicated protection in WDM networks without wavelength converters; (b) shared protection in WDM networks without wavelength converters; (c) dedicated protection in WDM networks with wavelength converters; and (d) shared protection in WDM networks with wavelength converters.

Abstract — Telecommunication networks have to deal with fiber cuts, hardware malfunctioning and other failures on a daily basis, events which are usually treated as isolated and unrelated. Efficient methods have been developed for coping with such common failures and hence users rarely notice them. Although less frequently, there also arise cases of multiple failures with catastrophic consequences. Multiple failures can occur for many reasons, for example, natural disasters, epidemic outbreaks affecting software compo-nents, or intentional attacks. This article investigates new methods for lessening the impact of such failures in terms of the number of connections affected. Two heuristic-based link prioritization strategies for improving network resilience are proposed. One strategy is built upon the concept of betweenness centrality, while the second is based on what we call the observed link criticality. Both strategies are evaluated through simulation on a large synthetic topology that represents a GMPLS-based transport network. The provisioning of connections in a dynamic traffic scenario as well as the occurrence of large-scale failures are simulated for the evaluation.

Abstract—The quality of service (QoS) is an important and considerable issue in designing survivable dense wavelength division multiplexing (DWDM) backbones for IP networks. This paper investigates the effect of network topology on QoS delivering in survivable DWDM optical transport networks using bandwidth/load ratio and design flexibility metrics. The dedicated path protection architecture is employed to establish diverse working and spare lightpaths between each node pair in demand matrix for covering a single link failure model. The simulation results, obtained for the Pan-European and ARPA2 test bench networks, demonstrate that the network topology has a great influence on QoS delivering by network at optical layer for different applications. The Pan-European network, a more connected network, displays better performance than ARPA2 network for both bandwidth/load ratio and design flexibility metrics.

Shared path protection has been demonstrated to be a very efficient survivability scheme for optical networking. In this scheme, multiple backup paths can share a given optical channel if their corresponding primary routes are not expected to fail simultaneously. The focus in this area has been the optimization of the total channels (i.e., bandwidth) provisioned in the network through the intelligent routing of primary and backup routes. In this work, we extend the current path protection sharing scheme and introduce the Generalized Sharing Concept. In this concept, we allow for additional sharing of important node devices. These node devices (e.g., optical–electronic–optical regenerators (OEOs), pure all-optical converters, etc.) constitute the dominant cost factor in an optical backbone network and the reduction of their number is of paramount importance. For demonstration purposes, we extend the concept of 1:N shared path protection to allow for the sharing

Abstract-New signaling suites for a distributed control plane in wavelength division multiplexing (WDM) networks, such as generalized multiprotocol label switching (GMPLS) and automatic switched optical networks (ASON), allow one to cope with the increasing variability of traffic patterns to be supported by operators by providing a means to dynamically set up and release connections. The dissemination of link-state information [usually provided by routing protocols such as open-shortest-path-first traffic engineering (OSPF-TE)] is essential in this kind of control-plane enabled network: in particular, this information has to be continuously updated to allow routing algorithms to efficiently carry out the path computation. Most of the studies on dynamic traffic routing tend to neglect the effect of delays in controlinformation distribution on routing performance: in particular, even when the control plane is considered as in testbeds, emulators, or some simulations, the analysis of the effects of control plane delays is limited to a small range of values, applicable to wellspecified contexts. Applying a very general controldelay representation, we are able to provide a widerange simulative study to quantify the effect of signaling on routing performance, mainly by using the blocking probability metric. We are able to evaluate the effect of outdated information (1) for a wide interval of control delay values, (2) for a large set of routing scenarios, considering, e.g., unprotected, dedicated, and shared path protection routing, and (3) quantifying the different delay effects in the absence or in the presence of wavelength conversion capabilities.