Preemption based lightpath restoration

Network element failure may occur due to natural disasters, malfunctioning components, or human errors. Ideally, network failure occurrence should not affect the network performance as it is experienced by the users. For this reason, robust protection mechanisms resort to standby network resources, which are readily available upon failure occurrence, e.g., dedicated path protection. In some network architectures and service models, a less ideal protection approach may still be applicable in exchange for a reduced network and service cost. Graceful degradation of performance upon failure occurrence may be acceptable in this case. The study in this paper explores preemption-based restoration mechanisms applied to optical connections (lightpaths) in Wavelength Division Multiplexing (WDM) networks. The rationale for preempting some of the still functioning lightpaths - while performing rerouting of the failing ones - is to avoid highly unfair scenarios in which some node pairs starve for lightpaths significantly more than other pairs do, as a consequence of a failing network element¹.