BitTorrent download rate oscillating strangely
I'm observing some weird behavior in Azureus. My download rate is oscillating with a very definite, fixed period. It is synchronized with a similar oscillation in the swarm upload rate. I haven't spent any time getting to know the details of how BitTorrent works -- does anybody know why this is happening?
I'm not confused because it's oscillating -- I'm confused because it is oscillating with a VERY steady period. Look at this graph:
I'm connected to 2/12 seeds, 0/12 peers, in case that means anything. Has anybody else ever seen such a regular, oscillating graph? I'm baffled. What the heck could be causing it?