As we have already seen that(OSPF High Availability with SSO,NSF and NSR) there are two different mechanism to prevent routing protocol re-convergence during a processor switch-over. One is Graceful Restart(Non Stop Forwarding) and another is Non Stop Routing(NSR). Graceful Restart and Non Stop Routing allows for the forwarding of data packets to continue along known routes. By using Graceful Restart routing protocol information is being restored while using Non Stop Routing, routing protocol information is being refreshed.