While it is well-known that BGP is vulnerable to simple, accidental misconfigurations that can cause widespread loss of connectivity, most of the evidence is anecdotal. Routing configuration errors have received less attention than more popular threats to connectivity, such as denial-of-service, and CAIDA's BGP analyses and Merit's IPMA project provide some of the only data available.

We present initial results of a new study of BGP configuration errors based on publicly available routing table snapshots and looking glasses. We quantify the kind and extent of configuration errors, as well as their impact on backbone connectivity. In this talk, we focus on announcements with incorrect origin AS and partial connectivity.

We find that there are a significant number of questionable routing announcements, but the majority of these have only a slight impact on connectivity. Of the roughly 2% of the prefixes per day that are not announced with consistent origins, O(100) prefixes are subject to AS-path stripping and potential address space hijacks, while the other fluctuations are more benign. We also analyze partially connected address space (that is reachable only from some parts of the Internet) to expose route filtering and damping practices that are limiting connectivity. We find that 1-2% of the address space exists in a persistently partially reachable state at any given time.

About the Presenter
Ratul Mahajan works on Internet routing, router pushback for DDOS/flash crowds (aggregate congestion control), and identifying misbehaving flows (RED with preferential drop). He is a graduate student at the University of Washington.