Sonic.net leases the lines from AT&T. 40mbps as far as I remember is a bonded ADSL+ service requiring two phone lines. Even then 20mbps is a theoretical maximum which falls off the further you are from Sonic's DSLAM. The U-Verse boxes brings the DSLAM much closer. In my apartment's case, I can only get 5mbps from Sonic.net while AT&T is able to deliver over 20mbps.