Disclaimer (means of escaping if some wrong info is posted ):I just sat and read and these are my inferences, need not be 100% correct.

People using bsnl dataone will see 'ADSL' written on the modems, which stands for Asymmetric Digital Subscriber Line. This is the reason why we have great downloads speeds (its upto 2mbps, not 2 mbps, can b 128 kbps, 1 mbps anything), but our upload speeds are very very low. ADSL is transmitted thru copper wires, so thats why BSNL people din have to dig up roads to lay wires like the Ambani's did. The signal for our Internet transmission uses different frequencies compared to our normal voice calls. So we can make calls nd use net at the same time...if u think that is no big deal, that is cos u haven't used dial-up.
The signal does not travel long distances thru these lines, usually only till 5 kms, so thats why rural people don't get dataone. thats why sreedish dint get dataone until a few months back, wen the exchange near his house started giving connections.

Blue region shows transfer from BSNL(service provider) office to your house nd green region shows transfer from your house to BSNL office. So i assume that since the blue region (downstream) is bigger, we get higher download rate...nd since green region(upstream) is smaller,we get lower upload rates..
and the red area shows the one for our normal voice calls.
My modem says its ADSL ,so its maximum downstream rate is 8 Mbits/sec nd max upstream is 1Mbit/seconds

What not to forget :

• ADSL is Asymmetric not Asynchronous or Assymetric
• Downstream doesn't mean the stream is at lower frequencies, but it means 'download stream'
• When u say your connection speed is 2Mbps, its not 2 Mega Bytes per sec, but its 2 Mega bits per sec....and its the download speed nd not your upload speed..remember ASYMMETRIC.

• @dish : the modems that are kept in our houses are also called routers. And routers are just not the only things that costs 1.5lakhs, heard you talking about with tommy, thats why i mentioned it here

Reference : http://en.wikipedia.org/wiki/ADSL

nd wer da hell is comic sans :(..hope you have been enlitened

*-*PeAcE*-*