I upgrade to the sb6121 from a wanky , older Motorola SBG900 Surfboard Gateway device , and the Doscis 3 have make all the difference in the world . accord to online speed test , I have more than quadruple my internet download speed . I have only have it connect for a few hour so I can not yet speak to the modem 's reliability , but I be very happy with this purchase . if you isp support it , I highly recommend switch to Docsis 3 .