This paper describes migration strategies in optical networks. It is expected that the conversion of current transport networks (IP/MPLS over SDH) into more packet oriented (IP/MPLS over Ethernet) technologies will result in significant cost savings for network operators. The state space of a migrating network can be modeled as a directed graph. To find the optimal migration path within this state oriented graph, several approaches, such as the incremental migration and the all-period migration can be used. Current research results regarding cost development and resource utilization in layer 1 and layer 3 are presented in this work. The effects of several planning techniques within such uncertain environment, like routing and grooming, on the total cost development are discussed, too.