Modern networks can be programmed to change packet routing based on packet type, time of day, and activity intensity. The only way to really understand latency issues is to take a lot of samples, paste them into Excel, and create a scatter graph.

It is important that your sample latency packets look just like SQL*Net packets. One of the best ways to do this is to use Oracle's tnsping command, found in the $ORACLE_HOME/bin directory.7 While both the ping and tnsping commands provide network latency times, the classic ping command is not good enough. Sharp network administrators managing a complex network infrastructure could possibly delay a standard ping packet, stop it altogether, or route it around the world a few times. So simply avoid this trap by issuing the tnsping command.

Take hundreds or thousands of tnsping samples. Don't sample once every second, or you might have an unsavory encounter on your way home from work. Create a simple shell script that runs tnsping once every 30 or 60 seconds, directing the output to a text file. And let this run for a couple of days. Do some fancy awk'ing and grep'ing, and then drop the data into an Excel spreadsheet to get a good understanding of the situation.