Preventing the Unnecessary Propagation of BGP Withdraws

Virginie Van den Schrieck, Pierre Francois, Cristel Pelsser and Olivier Bonaventure

Due to the way BGP paths are distributed over iBGP sessions inside an Autonomous System (AS), a BGP withdraw that follows a failure may be propa- gated outside the AS although other routers of the AS know a valid alternate path. This causes transient losses of connectivity and contributes to the propagation of a large number of unnecessary BGP messages. In this paper, we show, based on RouteViews data, that a signi´Čücant number of BGP withdraws are propagated even though alternate paths exists in another border router of the same AS. We propose an incrementally deployable solution based on BGP communities that allows the BGP routers of an AS to suspend the propagation of BGP withdraws when an alternate path is available at the borders of their AS.

In Proceedings of IFIP Networking, 2009.

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