dude it's called network priortising... and it'done by yur ISP.
They rout the available bandwith during bussiness hours to were business lives (Usually big cities) and choke home connections, then after the bussiness day finishes, they rout evrythng back to normal again, thus yu getting better speeds late at night.
I know this for a fact!
Now with Optus, they apper to have decded to permanantly rout my bandwithd and choke me down to about 500Kbls, and continue to charge me for a full 10Mbit connection.
This phenomenoun is also known as "GO AUSSIE GO! GO! GO!" or "Gullible Stupid Docile Ignorant Customer Syndrome".....
It's been reported at record levels as it would seem that ISP's in Aus can prett much do w00t evr the fuck hey want... that mainly been, advertising the moon but giving you a sewer view after moneis paid....
The icing on the cake of course is all these corporate smokers (I mean politicians in general), telling you how good you got it, so shut the fuck up and PAY!.... PAY!... PAY! All the way with the American way......
bravo... hurroooah... yehaaawww... yippeeeeee.......
....i just don't give a flying fuck anymore.......