Abstract: BGP (border gateway protocol) allows each AS (autonomous system) in the network to set its own routing policy to choose or advertise routing. While BGP routing policy configuration becomes flexible for autonomy, the routing policy conflict may emerge, causing routing flapping and diverging with network performance reducing greatly. This paper proposes a flap damping mechanism to solve BGP routing policy conflict. In this mechanism, the flap paths are detected by analyzing routing advertisement messages, and the local preference attribute values of the paths are adjusted according to the flap times, making the local preference attribute values of stable paths be greater than those of the flap paths. Then, the stable paths are selected with higher priorities than the flap ones in routing decision phase. Thus, the flap paths are damped, helping to solve the BGP routing policy conflict. The proposed mechanism is implemented and deployed on prototype system, and its performance is evaluated. The results show that it has good performance.

Key words: border gateway protocol (BGP), inter-domain routing, routing convergence, policy conflict, flap damping

摘要： 边界网关协议（border gateway protocol，BGP）允许网络中的每个自治系统（autonomous system，AS）设定自己的路由策略来选择和通告路由。尽管这种自治性会使BGP路由策略的配置更加灵活，但有可能引发路由策略冲突，即路由振荡和发散，导致网络性能下降。为此，提出了振荡抑制机制以解决BGP路由策略冲突问题。该机制通过分析路由通告报文发现振荡路径，根据振荡次数修正路径的本地优先属性值，使稳定路径的本地优先属性值比振荡路径的大，从而使得稳定路径在路由决策阶段比振荡路径被选中的优先级高，达到抑制振荡路径进而解决路由策略冲突。在原型系统上实现并部署了所提出的机制，并对其进行了性能评价。结果表明，该机制具有较好的性能。

关键词: 边界网关协议（BGP）, 域间路由, 路由收敛, 策略冲突, 振荡抑制