Cable modem be not something for you to take care of in daily life . a good modem should be install and forget . it be the reason why I do not upgrade my modem from docsis-1 to docsis-2 until 2009 . I do not do it until I realize my internet speed be much slower than what Comcast promise then . that upgrade raise the average download throughput from 5 to 15mbp . I have be use the same internet service for more than one decade . the cable company promise 1.5 mbp at very begin . with the same monthly rate they push up they promise speed gradually . the speed be raise to 20mbp recently . but you can not enjoy the speed boost if you keep use you old hardware . my 3-year old Motorola sb5101 be also a good install and forget modem . but the connection speed can become very slow in evening , the rush hour of residential internet . docsis-3 provide the channel bonding feature which be better in retain bandwidth even in rush hour . you must contact the cable company to activate you new cable modem before use it . it be not a big deal for I because I do it twice in past decade , but I can not recall all the detail . the first Comcast specialist try to activate my sb6121 many time w\/o luck so that he transfer my call to a 2nd tier specialist . he ask I to power-cycle my modem -lrb- shut down then turn on again -rrb- , then it work flawlessly . yes , power-cycle be a necessary step in activation . the first specialist forget it and waste I almost one hour . my download speed be quite stable -lrb- 16 ~ 21mbp -rrb- now , even in evening . the throughput be only slightly faster but much more consistent than before . it work as promise . Internet technology keep evolve so that you can not always install and forget it . update -- I replace my old Linksys router with e3200 one month later . now the download speed be always fix at 25mbp , 24\/7 . look like 25mbp be the speed cap set by Comcast . the sb6121 + e3200 combo should be able to run even faster if I be willing to pay higher monthly rate . once again you need up-to-date gear in order to get full bandwidth from the internet connection you pay for .