Journal of High Speed Networks

Transparent optical nodes (TONs), such as all‐optical switches and erbium‐doped fiber amplifiers, are an increasingly important part of wavelength‐division multiplexed (WDM) networks. Our goal in this paper is to consider how quality of service (QoS) may be monitored at such TONs. The question is particularly important as access to WDM networks, and associated security concerns, increase. Our paper has four parts. First, we present an overview of the vulnerabilities of TONs to QoS degradation for two main classes of TONs, namely all‐optical switching nodes and amplifiers in optical networks. Second, we discuss the applicability of traditional supervisory methods to such degradations. Third, we propose a novel approach to monitoring QoS degradations in TONs. Our approach works by comparing the input and output at a node and deciding whether unacceptable service degradation has occurred at that node. Finally, we analyze the performance, under simple attack scenarios, of our approach for jamming attacks at transparent optical switching nodes and amplifiers. We show that our method is several orders of magnitude faster than bit error rate testers in detecting QoS degradations.

Faults in the optical network environment propagate quickly to different parts of the network raising a large number of alarms. This paper describes two new fault diagnosis techniques for single fault diagnosis in an optical network. Both techniques operate under the same premises: when a fault occurs, a central manager detects the fault and through tests and correlation of information identifies the failure. The performance of the proposed schemes is compared both analytically and by simulation to each other and other proposed schemes for fault diagnosis in the optical network environment.

We investigate the problem of topology design of an optical network by bottleneck‐cut identification. For an optical network, the topology‐design problem can be viewed as a combined two‐layer design problem: physical‐topology design and virtual‐topology design. In this study, we present the definition of bottleneck cut of an optical network. A heuristic algorithm is proposed to find the bottleneck cut, and then we show how to apply this algorithm to an optical network for topology design and upgrade.

In the protection scheme of fault management in a WDM optical network, corresponding to every source‐destination path used for data transmission, a backup path is maintained in a stand‐by mode. In the case of a failure (either due to a fiber cut or due to equipment failure) in the primary path, data transmission is quickly switched to the backup path. In order to tolerate any single fault, the backup path must be edge (or node) disjoint from the primary path. Most often a shortest path between the source and the destination is chosen as the primary path. To obtain a link (node) disjoint backup (or secondary) path, the links (nodes) of the primary path are removed from the graph and then a shortest path in the modified graph is chosen as the backup path. The attractive feature of this scheme is its simplicity. However, the scheme has a severe drawback. Due to the choice of a shortest path as the primary path, the length of a link disjoint secondary path may be unacceptably large. In this paper, we propose a novel way of choosing the primary and the secondary paths so that the lengths of both the paths are small. Unfortunately, the problem of choosing primary and secondary paths in this way turns out to be NP‐complete. We provide the NP‐completeness proof of both the edge disjoint and the node disjoint version of the problem. We provide an approximation algorithm for the problem with a guaranteed performance bound of 2 and a mathematical programming formulation for the exact solution of the problem. Though the approximate solution provides a performance bound of 2, through extensive experimental evaluation, we find that the approximate solution is very close to the optimal solution and the ratio between the approximate to the optimal solution never exceeds 1.2. Although we discuss the single fault scenario in this paper, the algorithms discussed here, can be used equally effectively for the multiple fault scenario also. Finally, we discuss other variations of the disjoint path problem relevant to the lightwave networks.

In wavelength division multiplexed networks (WDM) with 1:1 path protection, a link‐disjoint protection (backup) path is also set up at the time of setting up a working (primary) path. Hence, the failure of a single fiber‐link does not cause huge data losses. This paper considers on‐line routing and wavelength assignment (RWA) of protection paths in such networks. In particular, we study two strategies based on the 1:1 path protection scheme. The Static strategy establishes protection paths such that once a route and wavelength have been chosen they are not allowed to change. On the other hand, the Dynamic strategy allows for re‐arrangement of protection paths, that is, both the route and wavelength chosen for a protection path can change so as to accommodate a new request. With either strategy, we assume that the working paths cannot be re‐arranged. This is to prevent the disruption of on‐going traffic. The two strategies are compared on the basis of the number of connections requests that can be satisfied for a given number of wavelengths, assuming that the requests come one at a time, and wavelengths are assigned according to the First‐Fit policy. One of the results of our study is that, contrary to intuition, the Static strategy performs better than the Dynamic strategy.