The operational model for large Internet service providers is moving to a multi-layer architecture consisting of IP/MPLS coupled with OTN/DWDM. While there has been significant work on multi-layer networks, the explicit modeling in IP/MPLS over OTN/DWDM has not been addressed before. In this paper, we present a detailed network optimization model for the operational planning of such an environment that considers OTN as a distinct layer with defined restrictions.