Advertisement of the best external route in BGP
Pedro Marques, Rex Fernando, Hannes Gredler, Prodosh Mohapatra, Enke Chen · 2012
The base BGP specifications prevent a BGP speaker from advertising any route that is not the for a BGP destination. This document specifies a modification of this rule. Routes are divided into two categories, and internal. A specification is provided for choosing a best external route (for a particular value of the Network Layer Reachability Information). A BGP speaker is then allowed to advertise its best external route to its internal BGP peers, even if that is not the for the destination. The document explains why advertising the external can improve convergence time without causing routing loops. Additional benefits include reduction of inter-domain churn and avoidance of permanent route oscillation. The document also generalizes the notions of internal and so that they can be applied to Route Reflector Clusters and Autonomous System Confederations.