I just had Xfinity 200 Mbps (Blast Pro) service installed. I'm using a Zoom 5370 DOCSIS 3.0 686 Mbps capable modem. When the installer initially hooked me up I wasn't using a router so the modem connected directly to my 1.0 Gbps Ethernet port with Cat6 cable. Speedtests rendered 150 Mbps, but later when I added my TP-Link TL-WR941ND (450 Mbps) router it went down to 94 Mbps.