[c0nsumer]

So... Changing the MTU didn't help. Even at the minimum of 1200 I still had issues. Sometimes pings (even small 60 byte ones) would be fast, other times they'd be upwards of one second. Not sure what's going on yet, as I've put working on this aside for now.

[ay]

Okay, if there is a jitter on individual pings, it is certainly not the PMTUD-related - and if there is no packet loss, then it is shaping - either intentional, or some middlebox can't cope with the load.

When using AICCU (sixxs) - were you using protocol 41 or the UDP-based encap ? if protocol 41, then experimenting with switching to UDP might be interesting.