In this presentation, I will describe what we have learned over time about inter-AS topology, long-term properties of routing policies, and challenges of inferring routing policies. I will further address transient behavior of interdomain routing. A graph theoretical model for charactering and analyzing the transient behavior of interdomain routing will be described. I will show what routing policy and topology can lead to transient end-to-end path failures and forwarding loops, and measurement results of the impact of routing dynamics on end-to-end performance.