A control scheme which is used to set up and tear down lightpaths, should not only be fast and efficient, must also be scalable, and should try to minimize the number of blocked connections; while satisfying the requested level of fault-tolerance. In this work we propose a distributed control scheme based on preferred link approach for establishing reliability-constrained least-cost lightpaths, by choosing the reliability of a lightpath to denote the level of fault-tolerance required by the connection request. Four heuristics are proposed and their performance is studied through extensive simulation experiments. The simulation results suggest that our heuristics provide better performance compared to other distributed protocols available, in terms of average call acceptance rate, average path cost, average routing distance, and average connection setup time; when the connection requests with different levels of fault-tolerance requirements arrive to and depart from the network randomly.