Research And Implementation Of Graceful OSPF Restart

With the fast progress of telecommunication service, it calls for not only larger service capacity, but also better service quality. One of the urgent requests is how to maintain a router's data forwarding capability while the router's control software is restarted/reloaded which called "graceful restart" or "non-stop forwarding".After the analysis on the process of Graceful OSPF Restart described by RFC3623 and the Implementation of each IP network service vendor, it is found that these resolutions of Graceful OSPF Restart has some defaults that it can't restart gracefully in some cases in the application now. For this reason, in this page, the perhaps reason of graceful restart is all found out firstly. Based on the degree of urgency of going into Graceful OSPF Restart, the reason of Graceful OSPF Restart is divided into software-restart and hardware-restart, and the way of Graceful OSPF Restart is divided into pre-restart mode and post-restart mode accordingly. After the compare with the traditional OSPF realization method and the analysis on the mechanism of the trigger of Graceful OSPF Restart and synchronization of link state database and the exchanging with the route management module (RTM), it is figured out that how to choose the restart mode and how to switch from pre-restart mode to post-restart mode, and how to synchronize the link state database, and how to define the interface and process flow exchanging with protocol supporting module, and how to deal with the forwarding table on the condition of multiple route protocols who also have the capability of graceful restart. Finally, the idea of Graceful OSPF Restart with two modes above was realized in the T series routers that belong to a telecommunication corporation.Based on the Implementation of Graceful OSPF Restart consisting of pre-restart mode and post-restart mode, the performance experiments on the retransmission of the Grace-LSA and the Graceful OSPF Restart consisting of pre-restart mode and post-restart mode is carried through. The experimental...