Network re-optimization is a process that must be triggered periodically in order to improve the inefficient resource allocation of online routing heuristics due to the uncertainty of online lightpath demand arrivals and departures. Network re-optimization involves two tasks: a) finding new lightpaths for a (sub)set of current demands, i.e. rerouting, and b) migrating the current traffic to the new configuration diminishing traffic disruptions, i.e. lightpath reconfiguration. If not controlled, excessive traffic disruptions may be a cause of violations of clients' Service Level Agreement, which should be compensated by the network operator with penalization fees.