Changes in the RTT are usually and indication of configuration changes or changes in congestion levels. RTT variance Some applications are sensitive to variance in transit time. Video and audio application are particularly sensitive. At ANS, this kind of measurement is typically done in cooperation with a customer. ANS uses ICMP, but there may be other good methods using RMON probes.
Correlation can lead to the reasons for packet loss.
The Ideal end result will be the ability to predict this before it happens and act to prevent it. A large mix. There are gaps in the standards. LQM on ATM VCs is needed. Router logs Very useful when doing post-mortem, however router log formats are very vendor specific.