This article first presents a broad overview of the fault management mechanisms involved in deploying a survivable optical mesh network, employing optical crossconnects. We review various protection and restoration schemes, primary and backup route computation methods, sharability optimization, and dynamic restoration. Then we describe different parameters that can measure the quality of service provided by a WDM mesh network to upper protocol layers (e.g., IP network backbones, ATM network backbones, leased lines, virtual private networks), such as service availability, service reliability, restoration time, and service restorability. We review these concepts, the factors that affect them, and how to improve them. In particular, we present a framework for cost-effective availability-aware connection provisioning to provide differentiated services in WDM mesh networks. Through the framework, the more realistic scenario of multiple near-simultaneous failures can be handled. In addition, the emerging problem of protecting low-speed connections of different bandwidth granularities is also reviewed.

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on the number of unavailable minutes per year. The widespread belief is that networks with faster restoration times are more reliable, created by the assumption that fast restoration from a failure leads to smaller down time. This is not necessarily the case since it has been shown that reliability may have little to do with the restoration speed when the restoration time is small compared to the mean time to repair of the failed elements. In this paper, we compare the reliability of optical mesh networks with multi domain restoration and single domain restoration using both dedicated mesh protection and shared mesh restoration, and show that splitting a network into multiple domains increases the overall reliability. 1.

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.

Abstract: This paper investigates the problem of dynamic survivable lightpath provisioning against single node/link failures in optical mesh networks employing wavelengthdivision multiplexing (WDM). 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 protection-switching-time requirements. For example, lightpaths carrying voice traffic may require 50 ms protection while lightpaths carrying data traffic may have a wide range of protection-switching-time requirements. Numerical results show that, compared to shared-path protection, our approach achieves significant performance gain which leads to remarkable reduction in blocking probability. While our focus is on optical WDM network, the basic ideas of our approaches can be applied to multiprotocol label switching (MPLS) networks with appropriate variations, e.g., differentiated bandwidth granularities. Index Terms — Optical network, WDM, lightpath, survivability, quality of protection, protection-switching time.

Network survivability is becoming an important issue and a topical subject in WDM optical mesh networks. Many works have studied network survivability. However, few works have focused on survivability in multi-domain optical networks. This paper reviews the literature on survivability against failures in multi-domain optical networks. The main objective of this study is to evaluate and analyze existing solutions and to compare their performance in terms of different criteria: resource utilization, ratio of rejected connections and recovery time.

We investigate three restoration techniques (path, subpath, and link restoration) for fault management in an IP-over-WDM network. We have implemented all of these techniques on the ns-2 simulation platform using GMPLS control signaling. These techniques can handle practical situations such as simultaneous multiple fiber failures, which are difficult to design for and recover from by nonrestoration techniques. We then present performance measurement results for the three restoration techniques by applying them to a typical nationwide mesh network running IP over WDM. We investigate interesting trade-offs in the performance of the restoration techniques on restoration success rate, average restoration time, availability, and blocking probability.

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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

The Internet is supported by long haul WDM core networks. Reliability is a huge concern in WDM core networks since service disruption would carry significant revenue, reputation and prospect loss. In ensuring reliability to network services, two means of protection scheme are usually used in WDM core networks; dedicated path protection and shared path protection. A comprehensive comparison of dedicated and shared path protection is discussed in this study. Availability concerned path protection implemented in the study will be based on random dynamic arrival traffic with adaptive routing method. The comparison will be based on several quality benchmarks such as availability satisfaction ratio, blocking probability, link utilization, provisioning complexity and network utilization.