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:

http://www.codepsycho.org/brewbuck/bt.png

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?

is your upload limit big enough? For every 10 downloaded bytes using TCP protocol you sending 1 byte up for approving arrival...
So 256KBit/sec of download uses about 25kBit of upload...
If You do not have enough upload bandwidth - upload from any program can greatly decrease the download speed...

Also you may want to check the stability of the service provided by your internet provider - not always they give you constantly the paid bandwidth, sometimes it flowes due to other user usage sharing the same cabel/gateway

Quote:

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Originally Posted by vart

is your upload limit big enough? For every 10 downloaded bytes using TCP protocol you sending 1 byte up for approving arrival...
So 256KBit/sec of download uses about 25kBit of upload...
If You do not have enough upload bandwidth - upload from any program can greatly decrease the download speed...

Also you may want to check the stability of the service provided by your internet provider - not always they give you constantly the paid bandwidth, sometimes it flowes due to other user usage sharing the same cabel/gateway

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I understand that stuff. What I'm confused about is why the oscillation is so rock-steady. It's like a pacemaker. Did you look at the graph? That's doesn't look like random influences to me.

if you don't see correlations with some periodic uploads that happen in your system - you can try to use some sniffer like Ethereal to see some dependencies maybe...

Or you can switch temporary to another client - like mu-torrent to ensure that this is not your program problem (I really dobt that this is Bit-torrent issue - but to be sure is always nice)

Quote:

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Originally Posted by vart

if you don't see correlations with some periodic uploads that happen in your system - you can try to use some sniffer like Ethereal to see some dependencies maybe...

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But if you look at the graph, the "swarm rate" is oscillating too. The WHOLE SWARM is oscillating at a very steady rate. Very weird. There are not very many seeds available. I wonder if some seed host is oscillating because of something happening on THAT system...