9.2.3.1 Frequency of Route Advertisement

The parameter MinRouteAdvertisementInterval determines the minimum amount of time that must elapse between advertisement of routes to a particular destination from a single BGP speaker. This rate limiting procedure applies on a per-destination basis, although the value of MinRouteAdvertisementInterval is set on a per BGP peer basis.

Two UPDATE messages sent from a single BGP speaker that advertise feasible routes to some common set of destinations received from BGP speakers in neighboring autonomous systems must be separated by at least MinRouteAdvertisementInterval. Clearly, this can only be achieved precisely by keeping a separate timer for each common set of destinations. This would be unwarranted overhead. Any technique which ensures that the interval between two UPDATE messages sent from a single BGP speaker that advertise feasible routes to some common set of destinations received from BGP speakers in neighboring autonomous systems will be at least MinRouteAdvertisementInterval, and will also ensure a constant upper bound on the interval is acceptable.

Since fast convergence is needed within an autonomous system, this procedure does not apply for routes receives from other BGP speakers in the same autonomous system. To avoid long-lived black holes, the procedure does not apply to the explicit withdrawal of unfeasible routes (that is, routes whose destinations (expressed as IP prefixes) are listed in the WITHDRAWN ROUTES field of an UPDATE message).

This procedure does not limit the rate of route selection, but only the rate of route advertisement. If new routes are selected multiple times while awaiting the expiration of MinRouteAdvertisementInterval, the last route selected shall be advertised at the end of MinRouteAdvertisementInterval.