Below is a plot of RTT versus time for the path from caida.mae.net to nms1.San-Francisco.t3.ans.net. This plot is for a particularly sour day; a configuration change made nms1.San-Francisco.t3.ans.net unreachable from caida.mae.net from around 06:30 to 09:45 UTC. When the reachability returned, we see a change in the forward path for a few hours, and eventually a return to the original forward path. However, there's an obvious step function in the RTT after the period of unreachability, indicating a change for the worse in the reverse path.