A complete solution for iBGP stability

Abstract

BGP routers within an Autonomous System (AS) exchange their inter-AS routing information via the internal Border Gateway Protocol (iBGP). Within an AS, every BGP router needs to maintain an iBGP peering session with every border BGP router. This peering scheme fails to scale due to the large number of iBGP peering sessions required. Current solutions to this scalability limitation divide the AS into clusters, with a route reflector acting us a representative of the cluster. Clustering, however, introduces routing anomalies. Furthermore, BGP also uses a Multi-Exit Discriminator (MED) to differentiate multiple links connecting the same pair of AS'ms. However, clustering in combination with the use of MED values further aggravates routing anomalies. In this paper, we propose a complete solution that solves both clustering induced anomalies and MED induced anomalies in iBGP. Our solution requires multiple path disseminations between route reflectors and selective single-path dissemination from each route reflector to its client.