lab testing results

layer 2 store-and-forward devices affect tools accuracy
not handled by pathchar, pchar, clink

C. Dovrolis, R.S. Prasad and B. Mah,
"the effect of layer-2 store-and-forward devices on per-hop capacity estimation"(ieee infocom 2003)

not all routers are created equal
internal switches
different buffer configurations
use of "slow path" for ICMP traffic

accuracy of tools deteriorates at high loads
we have shown that per-hop capacity estimation tools (pathchar, pchar, clink) produce consistent and significant errors when path includes layer-2 store-and-forward devices.
all paths we have experimented with include one or more such devices
real and important problem
paper available on const web page and at infocom 2003

upshot: testing bandwidth estimation tools is nontrivial