On Tue, Apr 22, 2008 at 5:12 AM, Petri Helenius <petri@helenius.fi> wrote:
But there is another way. That is for software developers to build a modified client that depends on a topology guru for information on the network topology. This topology guru would be some software that is run number of total participants) I fail to figure out the necessary mathematics where topology information would bring superior results compared to the usual greedy algorithms where data is requested from the
michael.dillon@bt.com wrote: peers where it seems to be flowing at the best rates. If local peers with sufficient upstream bandwidth exist, majority of the data blocks are already retrieved from them.
You can think of the scheduling process as two independent problems: 1. Given a list of all the chunks that all the peers you're connected to have, select the chunks you think will help you complete the fastest. 2. Given a list of all peers in a cloud, select the peers you think will help you complete the fastest. Traditionally, peer scheduling (#2) has been to just connect to everyone you see and let network bottlenecks drive you toward efficiency, as you pointed out. However, as your chunk scheduling becomes more effective, it usually becomes more expensive. At some point, its increasing complexity will reverse the trend and start slowing down copies, as real-world clients begin to block making chunk requests waiting for CPU to make scheduling decisions. A more selective peer scheduler would allow you to reduce the inputs into the chunk scheduler (allowing it to do more complex things with the same cost). The idea is, doing more math on the best data will yield better overall results than doing less math on the best + the worse data, with the assumption that a good peer scheduler will help you find the best data. As seems to be a trend, Michael appears to be fixated on a specific implementation, and may end up driving many observers into thinking this idea is annoying :) However, there is a mathematical basis for including topology (and other nontraditional) information in scheduling decisions. _______________________________________________ NANOG mailing list NANOG@nanog.org http://mailman.nanog.org/mailman/listinfo/nanog