Intermittent packet loss several times per day – XB10 / WAN-side drops

I'm experiencing intermittent packet loss several times per day on my Xfinity connection. The connection is generally fine between events, so automated health checks usually report that everything is healthy.

My setup is an Xfinity XB10 gateway connected to my own UniFi router. I've been monitoring directly from the UniFi router's WAN interface, so these tests are not dependent on Wi-Fi or an individual client.

During the problem, I have captured simultaneous packet loss to both 1.1.1.1 and 8.8.8.8 while the WAN Ethernet interface remains UP with carrier present and zero RX/TX errors, drops, missed packets, or carrier errors. The WAN IP and default route also remain present.

Examples from September 30:

• Around 1:43:54 PM EDT, both 1.1.1.1 and 8.8.8.8 were unreachable for several seconds. I also observed a streaming interruption at approximately this time.

• Around 2:02 PM EDT, the router recorded additional Internet packet loss while the WAN interface remained healthy.

• Around 6:16 PM EDT, both Internet targets dropped simultaneously.

• Around 6:38 PM EDT, there were multiple simultaneous drops to both targets within about 15 seconds.

• Around 7:18:06–7:18:16 PM EDT, both 1.1.1.1 and 8.8.8.8 were continuously unreachable for roughly 8 seconds. During the entire event, the router's WAN Ethernet link remained up and all interface error/drop counters remained at zero.

The XB10's normal DOCSIS signal levels look very good. Downstream power is roughly +2 to +3.5 dBmV with SNR around 47–48 dB, upstream power is roughly 37–42 dBmV, and the normal channels are locked. I have also noticed that downstream OFDM channel 194 at 1050 MHz intermittently appears and disappears from the XB10 status page. When it appears, the page reports it as Locked but shows approximately -18 dBmV power and 0.0 dB SNR. The XB10 page appears to duplicate some codeword counters, so I don't know whether those displayed values are reliable, but the changing channel state may be worth checking from the CMTS side.

Could an Xfinity employee please check the modem/CMTS historical telemetry at the timestamps above for things such as:

• partial-service events

• downstream OFDM profile or channel changes

• upstream OFDMA impairment/noise

• T3/T4 or ranging events

• modem flap history

• node/CMTS packet loss or impairment

I have the full timestamped WAN logs available if they would be useful.