BGP route reflection revisited

The original BGP design requires that all BGP speakers within an autonomous system be directly connected with each other to create a full mesh, and BGP update messages be propagated to directly connected neighbors only. This requirement leads to BGP session scalability problems in networks with large numbers of BGP routers. Route reflection was proposed as a quick fix to address this BGP session scalability problem and has been widely deployed in the operational Internet without a thorough analysis of its pros and cons. In this article, we first provide an overview of the route reflection design, summarize the discoveries from published literature, and discuss the trade-offs in using route reflection as compared to using a fully connected i-BGP mesh. Then we show that well engineered route reflector placement can overcome certain drawbacks, and that a few issues remain open for future study.