Disadvantages of Centralized Routing
If rapid restoration is required, it is not possible to rely on a centralized routing system to compute a recovery path for each failed lightpath on demand after a failure has been detected. The distributed model arguably will not have this problem.
The centralized approach is not consistent with the distributed routing philosophy prevalent in the Internet. The reasons which drove the Internet’s architecture – scalability, the inherent problems with hard state information, etc. – are largely relevant to optical networking.
A centralized approach would seem to preclude integrated routing across the IP and optical boundary.