If your version of IOS supports it, take a look at the ip sla feature on cisco routers. It will provide the most accurate packet loss, latency and jitter results.
Here is an introductory page.
Here's another similar <a href="http://itknowledgeexchange.techtarget.com/itanswers/ip-sla/">question/answer</a> with more details.
Last Wiki Answer Submitted: October 23, 2008 7:16 pm by Peterp270 pts.