Research And Implementation Of OSPF Graceful Restart

As businesses become more dependent on IP networks, outages are more costly than ever and high availability in networks has become increasingly critical. This requirement for "five-nine" availability is more pressing at the network edge, where redundant user access links are scare.To help meet the goals of high availability, the Internet Engineering Task Force has built extensions to routing protocols such as BGP, OSPF, LDP that minimize the outage associated with a failed routing protocol. With OSPF Graceful Restart enabled on an edge device and its peer, the data plane can continue to process and forwarding packets even if the control plane fails. By also reducing routing flap, Graceful Restart stabilizes the network and reduces the consumption of control plane resources. Graceful Restart offers high availability for the network, which goes beyond high availability only for an individual router.This thesis focuses on the research and implementation of the OSPF Graceful Restart. During Graceful Restart, there are two roles being played by OSPF routers. First there is the router that is being restarted. Then there are the router's neighbors, which must cooperate in order for the restart to be graceful. The operations of the two roles are discussed. Additionally, the relationship between IGP and EGP Graceful Restart and the advantage as well as disadvantage of protocol Graceful Restart are analyzed.Based on the open source routing software Quagga, the OSPF Graceful Restart extension is designed and implemented. Grace lsas are sent several times to insure the reliable transmission of capacity advertisement. An adaptive topology change process is given in this thesis, which can increase the probability of the successful execution of Graceful Restart in large network where topology changes occur often. By extending the hello protocol in OSPF, the neighbor discovery and network convergence processes are quickened.A prototype is implemented to experiment the functionality and performance of our implementation of OSPF Graceful Restart. Our prototype has been considered to fulfill the basic functionality in RFC 3623, and the availability of our prototype has been improved.