11.6. Summary

Path computation algorithms play a key role in optical network routing [Ellinas+02]. While traditional shortest-path algorithms can be directly used in IP routing, additional constraints have to be considered in optical routing. Furthermore, finding physically diverse paths requires the application of new algorithms. Many vendors today use centralized path computation for provisioning connections. This is due to the need to optimize connection routing and also to reduce the complexity of implementations. Distributed path computation will be the norm with the newer control plane technologies [Bouillet+02c]. Some aspects of distributed path computation in large, multiarea networks were described in Chapter 10. The next chapter deals with routing in heterogeneous environments, where the challenge is to capture sufficient information about the structure of the network and available resources for efficient path computation.