A multi-layer recovery strategy in FAN over WDM architectures

Network operators are migrating towards IP over WDM architectures. In such multi-layer networks, it is necessary to efficiently use the resources available from both layers in order to provide coordinated recovery strategies. Thanks to the development of the control plane (GMPLS and ASON), it is feasible to set up and tear down lightpaths automatically, so the WDM layer itself can support failure recovery. This paper describes a multi-layer recovery strategy in a FAN/WDM (Flow-Aware Networking/Wavelength Division Multiplexing) architecture. We propose using the EHOT (Enhanced Hold-Off Timer) algorithm to control network operation after link or node failure. Although FAN operates only on the IP level, the presented analysis shows that it is possible to ensure sufficiently low (less than 50 ms) recovery times in FAN working over an intelligent optical layer. Additionally, the paper shows the motivation for FAN networks and presents the results of carefully selected simulation experiments which allow for evaluating the duration of outages in data transmission under various conditions.