The Scope of the IBGP Routing Anomaly Problem

Correctness problems in the iBGP routing, the de-facto standard to spread global routing information in Autonomous Systems, are a well-known issue. Configurations may route cost-suboptimal, inconsistent, or even behave non-convergent and -deterministic. However, even if a lot of studies have shown many exemplary problematic configurations, the exact scope of the problem is largely unknown: Up to now, it is not clear which problems may appear under which iBGP architectures. The exact scope of the iBGP correctness problem is of high theoretical and practical interest. Knowledge on the resistance of specific architecture schemes against certain anomaly classes and the reasons may help to improve other iBGP schemes. Knowledge on the specific problems of the different schemes helps to identify the right scheme for an AS and develop workarounds.