sorry if this seems so trivially obvious, but depending on what you are trying to measure, sources of significant signal noise *is* one thing to consider when doing an experimental design. using Pings to cisco routers produces a signal with a number of different components, some real signal, some noise, depending on what you you are trying to measure. so exactly what ARE we trying to measure??? I might have a suggestion if the problem was well-formed. for instance, if you want to measure "router busy-ness" then CPU load and SSE misses are probably good candidates. if you are trying to find out WHY the routers are busy, then you have to take more data (variables). If you are trying to establish how effectively (successfully?) the routers are forwarding packets across MAE-EAST, then I believe you need to do somethine more sophisticated than just ping routers. you could inject "dye" packets which get forwarded and then you monitor how many get across what paths and when. is this a lot me complex than just pinging routers? yes; knowning facts is often a lot more harder than handwaving. but the issue here *is* scientific experimental design. You have to define WHAT you want to measure before you can design an experiment to measure it. then you have to analyze the experiment to verify whether it actually measures what you want. then you run the experiment several times and analyze the output. and most importantly, if you do a good enough job of defining WHAT you want to measure, maybe some other enterprising folks will devise a different method to measure the same phenomenology and run independent experiments. this way you learn whether you are really measuring what you thought and can compare results. and if you do a good enough job of all this, you get to call it "science." otherwise, you are just collecting data and beating on graphing programs. And while I very much appreciate the intuitive bent which gets us all through the day, I haven't heard anything that looks like a definition of what we are trying to measure. -mo