Simulation tools for multilayer fault restoration

The complexity of networks today makes it difficult to handle fault restoration by means of human intervention. Future network architectures are expected to be self-protecting and, more generally, self-organizing. In this article we describe the modeling methods and simulation tools we have used for the analysis of a new integrated restoration scheme operating at multiple layers/networks. The networks over which we have performed the analysis are ATM and SDH, but the methodology could be applied to other multilayer architectures too. A network model has been created that consists of both ATM and SDH layers. Using this network model, we have seen how the new scheme explores the free bandwidth over both layers. The multilayer bandwidth exploration was modeled using Microsoft Visual C++. Using OPNET Modeler, a node model was created to analyze the restoration message processing within it and the interaction with other nodes for the purpose of simulating the restoration delay. The article emphasizes the simulation methodology rather than the results of the simulation. Among others, we describe which additional functionalities a simulation tool is necessary to have in order to simulate multilayer networks. A comparison of OPNET and Microsoft Visual C++ is made, describing their advantages and the reasons we found it necessary to use both.