Multi-topology Routing Technology For The Rapid Recovery Of The Ip Network

In the early stage of Internet, the TCP/IP protocol suite was developed to ensure successful transmission and in-order delivery of packets, supplemented by the re-convergence process to update the network state and ensure robust routing after changes in the network topology. In the real network environment, failures in network equipments are inevitable. Before the re-convergence process triggered by the failures is fully completed, packet loss, loops, delay, congestion and other issues may occur since all routers haven't attached to a common network topology. More recently, new type of applications like IPTV, IP telephony and online games are being offered through the Internet. Re-convergence process does not operate in a time-scale that is compliant with the stringent requirements of these real time applications, so researching route schemes that offer fast failure handling does make sense to some extent.The main theme for this thesis is the Multi-topology Routing (MTR) technology, which has been proposed by the Internet Engineering Task Force (IETF). MTR is a scheme that can be used to achieve fast recovery path from transient failures in IP networks. Its basic principle is to build a certain number of logical topologies based on network physical graph, named as Multi-topology (MT) or backup topology. The router, which is responsible for initiating the recovery action, maps the failure scenario to its corresponding backup topology, finds the next hop in the associated routing table and marks the backup topology's identifier in the header of IP packets. Then other routers forward the packets by inspecting both the topology identifier and the destination address in the packet header. This thesis focuses on the technology, evaluates the relevant routing and forwarding schemes through simulation, studies and proposes algorithms for generating multi-topologies. Besides, optimization of weight is applied to settle the load balancing issue after redirecting traffic to an alternate route using MTR.The first chapter introduces the distribution characteristics of failures and the existing route recovery schemes in IP networks. Chapter II researches on the basic principles and technical specifications of MTR. Firstly, two types of multi-topology are introduced, which are used for protecting nodes and links respectively. Then focusing on the protection of the link failures, both global and local recovery strategies, as well as the single or sort ascending path redirecting schemes are compared and analyzed through simulation.Based on the existing technology, further researches and improvements are as follows: (1) Multi-topology design. The third chapter introduces three kinds of algorithms for building backup topologies. One MT generation algorithm is proposed, which has good performance on decreasing the traffic load that every topology required to carry under double-link failure scenarios. As performance metrics, path length and link load are calculated to evaluate those algorithms. (2) Link Weight Optimization. In Chapter IV, firstly an integer linear programming (ILP) model is formed, and then a solution is proposed combined with the Genetics Algorithm to optimize the link weight of multi-topologies. The maximum link utilization before and after link weight optimization has been tested and compared.The fifth chapter describes the simulation platform constructed by OPNET tools. Chapter VI summarizes the full text.