Does anyone have any pointers on how other people have implemented tcp window adjustment to do bandwidth shaping?
Hmm....I _heard_ that Packeteer had patents on this and so nobody else was attempting to do it.
Possibly an incorrect rumor, but it made sense to me.
They say on their site that their algorithm is patented which could be a pain if it's the obvious solution.
The more I think about it (probably not enough yet), the more I think that just keeping state and depiggybacking acks could achieve much the same thing if your shaper is clever enough.
The worst senario for me is bittorrent, and if I could depiggyback the acks I don't see that playing with window size on top of that would be any better than keeping state so that I had an idea of how much was unstoppably on the way.
Closing the window down isn't going to stop what's allready left the sender and is sitting in a big modem buffer any quicker than me stopping sending acks. Just knowing how lagged out each connection is would be enough to allow me to change bandwidth more elegantly without too much buffer filling. Not with anything that exists in Linux now - but even just hacking HTB/HFSC so that a class could behave as full as soon as it sees traffic would be a start. I can allready sort of break slowstart by treating new connections harshly (short queue), though it would be nice in the case of bittorrent to be able to detect connections that go back into slowstart aswell - sfq sort of singles them out, but it's a bit late by the time it gets them.
I guess there are other things you could do aswell like trying to account for different rtts with the intention of avoiding bursts.
Andy.
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