An improved OSPF-TE in GMPLS-based optical networks

In GMPLS-based optical networks, when a lightpath is set up or torn down, all label switching routers (LSRs) on this lightpath need to advertise the changes of link states. Hence, in a dynamic environment, frequent changes of lightpaths causes heavy control overheads. Besides, the routing protocol for GMPLS, such as OSPF-TE or IS-IS-TE, doesn't disseminate wavelength availability information due to the consideration of control overhead. If optical networks have no wavelength converters, or only have wavelength converters at few LSRs, the routing and wavelength assignment (RWA) may suffer high blocking probability when wavelength availability information is not available. In this paper, an improved OSPF-TE protocol is proposed. The proposed protocol not only disseminates link state information very effectively, but also advertises wavelength availability information if necessary. Theoretical analyses and simulation results show that the OSPF-TE's control overheads can be reduced about 3-7 times in networks studied compared to the conventional flooding mechanism. Furthermore, blocking probability is also reduced, and the performance of optical networks is improved significantly.