IETF RFC 2439 PDF

A usage of the BGP routing protocol is described which is capable of reducing the routing traffic passed on to routing peers and therefore the load on these peers without adversely affecting route convergence time for relatively stable routes. This technique has been implemented in commercial products supporting BGP. The technique is also applicable to IDRP.

The overall goals are:

o to provide a mechanism capable of reducing router processing load caused by instability

o in doing so prevent sustained routing oscillations

o to do so without sacrificing route convergence time for generally well behaved routes.

This must be accomplished keeping other goals of BGP in mind:

o pack changes into a small number of updates

o preserve consistent routing

o RFC 2439 BGP Route Flap Damping November 1998

o minimal addition space and computational overhead

An excessive rate of update to the advertised reachability of a subset of Internet prefixes has been widespread in the Internet. This observation was made in the early 1990s by many people involved in Internet operations and remains the case. These excessive updates are not necessarily periodic so route oscillation would be a misleading term. The informal term used to describe this effect is "route flap". The techniques described here are now widely deployed and are commonly referred to as "route flap damping".