I'm not sure if that actually is the case, attainable rate is based on distance from box, among other parameters afaik. Coz, as distance increases attenuation should increase, and snr should go down, thereby affecting the line rate Many of the societies listed in the doc are not feasible for 8 mbit, this despite airtel usually terminating fiber within the societies via mini exchanges. It isn't available at my place. There seems to some other reason, not having enough capacity in a particular area perhaps.