Optimal Route Reflection Topology Design
Cristina Mayr, Eduardo Grampín, Claudio Risso · 2018
Autonomous Systems (ASes) exchange routing information about networks they can reach in the Internet, and the most widely extended way to connect them is by means of Border Gateway Protocol (BGP) sessions. ASes set up external BGP (eBGP) sessions between the AS border routers (ASBR) of neighboring ASes, and the routing information learned by ASBRs is then redistributed inside the AS through internal BGP (iBGP) sessions. In order to avoid loops, iBGP can not re-advertise prefixes learned from an iBGP neighbor to another iBGP neighbor. To have complete visibility, routers within the same AS are required to be connected in full-mesh. This causes scaling problems, since the number of required sessions grows quadratically with the number of routers involved. For large networks this can lead to administration issues, and therefore, in order to manage scalability, Route Reflection is generally accepted as an alternative to full-mesh. Even though Route Reflectors (RRs) simplify administration, they also introduce new problems such as: routing sub-optimality, increased probability of loops, poor route diversity, among others.