Ip Fast Re-routing Technology Research

Currently, most large-scale ISP networks use link state protocol, ISIS or OSPF, as the intradomain routing protocol. To ensure the consistency of the link state data bases for all the nodes, typical link state protocols (ISIS and OSPF) need to flood the topology information to all nodes by link state advertisements strategy. So, when a failure of link or network equipment is detected, a re-convergence process is needed to notify the failure and make sure the link state data bases of all nodes keep the same topology information again. However, during the re-convergence process, packets may be lost or delayed.For traditional services, the problems caused by re-convergence process are tolerable. However, the large-scale deployments of delay and loss-sensitive applications in recent years have led to stringent demands on network performance. For the real time applications, such as voice over IP (VoIP), streaming media, gaming, and telecommuting/video conferencing, loss and delay of packets will cause significant performance degradation, sometimes even service disruption. So, how to reduce packet loss and delay has become a challenging problem that ISP has to face. Therefore, IP fast restoration technology becomes an active research area in the past few years.In this thesis, typical fast restoration technologies nowadays are firstly overviewed. After that, a detailed comparation is presented through simulation results in terms of some key performance metrics, such as like lost packet rates and the count of loops. In chapter 3, a performance optimization scheme of the loop free alternative technology based on a mathematical programming model, which is solved by a genetic algorithm based approach, is provided.The simulation results show that the optimization scheme can signicantly improve the performe of the loop free alternative scheme. A novel fast rerouting approach is proposed in chapter 4, called Unidirectional Forwarding Cycle (UFL). By embeding two unidirectional forwarding cycles in advance, the UFL can guarantee 100% single failure restoration without the need of inhibiting the re-convergence process. In chapter 5, the simulation platform used in this thesis is presented in detail. Finally, a summary of the whole paper is given in chapter 6 .