I purchase this item because my Comcast provide SA\/Cisco DPC2100 box be sluggish . http traffic be slow and overall transfer traffic use to peak at 24mbit for 30 seconds before drop by 25 % to 18mbit . we have a Comcast Teleworker connection here which be suppose to deliver 25mbit downstream . additionally , I use to have a 24mbit connection via cable -lrb- different isp , different modem etc -rrb- before and it never use to happen . I go through the basic troubleshooting process - change cable , change setup , bench the dn , test different router etc. . in the end , it look like the modem . a bit digging online confirm that . my intention be to purchase a device where I do not have to restart the modem everyday or have constant time-out . the sb6120 be apparently the device of choice . Though because the 6121 be on offer for just $ 3 more , I choose it over the 6120 . I can not make a comparison between the two . however , the dpc2100 to the sb6121 be like day and night . my connection be , 2 day later , extremely stable . additionally , my ping rate decrease from 19m to 13m . the datum throughput increase from 24 to 27mbit - and it stay there ! all in all , a pretty good device .