Research On Routing Oscillation Cased By BGP Routing Policy Conflicts

Internet is a large communication and resources network that is composed of thousands of autonomous systems(AS), called routing domain. These autonomous systems belong to different network service providers respectively. Routers inside the autonomous system exchange routing information through interior gateway protocol. Routers belonging to different autonomous system exchange routing information and select routes through exterior gateway protocol. The border gateway protocol(BGP) is the de fact exterior gateway protocol running in the Internet. The border gateway protocol selects the best routes to destination network according to the routing policies developed by the autonomous system itself. Due to the business interests, every autonomous system develops routing policies independently. The routing policies belonging to different autonomous systems usually exists conflicts. Study shows that the routing policy conflictions between AS can cause BGP routing oscillation. The so called BGP routing oscillation is refer to the fact that routing information is exchanged continually among different AS. These autonomous systems can not have a stable route. BGP routing instability can affect the function of the Internet.In this paper, we firstly analyze the routing selection process in instance, and illustrate the route oscillation phenomenon. According to the route oscillation phenomenon, the cause of oscillation is analyzed in detail. Secondly, the problems related to the BGP route flapping inhibition appeared are studied and the analytical and methodological solutions are proposed in order to address the scope of research to use it in real networks. Moreover, the current resolve BGP fast convergence in case of to the problem is found out so as to allow the next optimization. After the analysis of border gateway routing oscillations, the route oscillation problem solving oscillations of BGP routing scheme is proposed which solves the BGP routing policy conflicts caused.Based on the simple path vector protocol proposed by Griffin T. G. a method to eliminate the route oscillation is given. In this method, the best route is marked when routing policy conflict is detected. When the same route is marked once again in the follow up route selection, it is demonstrated that there is a route oscillation caused by policy conflict. When route oscillation caused by policy conflict is detected, the marked route is no longer selected as the best route, and another route with short AS path is selected. Thus the route oscillation can be eliminated. In order to detect policy conflict and eliminate route oscillation, the BGP protocol is modify to carry information relation to policy conflict. The modified BGP is tested using network simulation software SSFNet. Simulation results confirm the validity of the method.