I'm actually quite sure -- the reaction time of the control unit should be less than the characteristic period of the controlled system. Think of it as a big pendulum which is subjected to rapid kicks -- by applying kicks at different directions you can keep pendulum at any angle. Try that if the pendulum swings faster than you can kick :) Not that it is very useful for updating metrics, but you can imagine a car radio which makes congestion announcements fast enough, so as to load 101 and 280 equally (car here, car there). Wait a second, that reminds me of something :) --vadim From: alex@relcom.eu.net Subject: Re: Why doesn't BGP... Vadim, are you shure about this? Withouth the friction - what would you got this case? Very big pendulum, isn't it?