Towards a Systematic Understanding of Route Reflection

The original BGP design requires all BGP speakers within an au- tonomous network to be directly connected with each other to cre- ate a full mesh, and BGP update messages to be propagated to di- rectly connected neighbors only. This requirement leads to BGP sessionscalabilityconcernsinnetworkswithlargenumbersofBGP routers. Route reflection was proposed by the operational commu- nity as a solution to address this scalability problem and has been widely deployed for a long time. However, measurement and anal- ysis studies occurred only recently to understand its pros and cons. In this paper we provide an overview of route reflection, summa- rize the discoveries from published literature, and discuss the ad- vantages and disadvantages of using route reflection as compared to using a fully connected iBGP mesh. We also use the route reflec- tion deployment in a large ISP as a case study to show how one can use well engineered route reflector placement to overcome certain drawbacks as well as remaining issues for future study.