— A powerful path computation element is a must for the next-generation IP-over-Optical networks to support ondemand service provisioning crossing layers. The main purpose of path computation in multi-layer networks (MLN) is to enable traffic engineering (TE) under a multitude of constraints. A common objective of such traffic engineering is to minimize resource utilization while satisfying all the applicable constraints. In this study, we investigate a variety of MLN path computation methods based on real-world control plane implementations and network settings. We present some techniques for handling the specific TE constraints that concern the IP-over-Optical networks. Experimental results are presented for performance evaluation and comparison of the investigated multi-constraint path computation methods and techniques.