WAN Monitoring

[Moose Magin]

Hiya people,   I'm looking for something (anything) that will monitor traffic on a frame relay link between 2 routers. Normally, between these 2 routers, we get pings on this link of 30-60, not a problem. At certain times however, the pings suddenly jump up to between 1000-2000 ms. Not good. Everything goes dreadfully slow across that link. We've stuck a couple of monitoring boxes on each side of the routers, and come up with nothing coming from our internal network that could account for it, so we are assuming it's on the frame relay itself, but we aren't sure. We need something that will help find the source of the problem, so we want something that will monitor and log everything going between the 2 interfaces. Did quite a lot of googling, and can't find a thing. Any suggestions?   Thanks, Matt.