The process of computing routes that network traffic must follow throughout network has become much more complex in recent years. PCE (Path Computational Element) technology is emerging and gaining importance under the circumstances. In this paper, PCE architecture is outlined, and the impact of PCEs allocation decisions is discussed briefly. To track the problem of locating PCEs, an integer linear programming (ILP) model is presented to find the optimal PCEs allocation solution in multi-domain optical networks. The objective is to minimize average amount of time for sending a message to all nodes in the topology, i.e. message flooding cost. Then, two heuristics, LSPLP and TSPLP, are developed based on this model. Numerical results show that compared with traditional allocation strategies, the proposed algorithms can reduce the message flooding cost efficiently.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.