Agile all optical cross-connect (OXC) switches currently use an architecture in which regenerators and transceivers have pre-assigned and fixed directionality. However, technology is evolving to enable new OXC architectures in which the directionality of regenerators and transceivers can be dynamically assigned on demand for each connection that requires regeneration. We have performed detailed analytical and simulation studies to compare the two architectures. The analytical study is applicable to a single node and is very useful in providing intuitive insights into the two alternative architectures. The simulation study is based on a realistic network topology consisting of 53 nodes. The simulation study was carried out using NIST's updated GMPLS Lightwave Agile Switching Simulator (GLASS) tool. The GLASS tool was significantly enhanced over its previous version in the course of this study. We report extensive results on comparison of the two OXC architectures in a realistic network implementation in terms of connection blocking probability, efficiency of regenerator use, and carrier equipment costs. We show that fewer regenerators and transceivers need to be used with the new architecture because of sharing of resources across all directionality combinations. This translates to significant cost savings for the new architecture, especially as the traffic load in the network increases. © 2005 IEEE.