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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.
user_lstern
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2 Messages
2 days ago
Update after leaving my WAN-side monitor running overnight:
I recorded 31 additional events between the evening of September 30 and the morning of October 1. Most were short packet-loss or latency events, but several were sustained complete outages to both 1.1.1.1 and 8.8.8.8 at the same time.
The clearest sustained outages were:
Sep 30, 10:06:22.716 PM EDT — both targets unreachable for approximately 6.8 seconds
Oct 1, 12:56:54.396 AM EDT — both targets unreachable for at least 14.2 seconds; the high-resolution capture ended before recovery
Oct 1, 2:20:02.836 AM EDT — both targets unreachable for approximately 11.9 seconds
Oct 1, 5:08:34.393 AM EDT — both targets unreachable for approximately 8.1 seconds
Oct 1, 7:16:17.446 AM EDT — both targets unreachable for approximately 12.0 seconds
Oct 1, 9:00:20.373 AM EDT — both targets unreachable for at least 14.2 seconds; the capture ended before recovery
Oct 1, 9:41:05.791 AM EDT — both targets unreachable for approximately 4.2 seconds
During all of these events, the UniFi router's WAN Ethernet interface remained UP, carrier remained present, the Comcast next-hop remained in the neighbor table, the WAN route remained installed, and the RX/TX error, drop, missed-packet, and carrier-error counters remained at zero.
One additional pattern I noticed during the longer outages is that the router continues transmitting packets while received traffic nearly stops until connectivity recovers.
This is occurring repeatedly throughout the night and morning, not just during peak evening usage, and the connection returns to normal between events. Because of that, a point-in-time automated Xfinity health check reports that everything is healthy.
I have the complete timestamped event logs available.
Could an Xfinity employee please correlate the exact timestamps above with the modem/CMTS historical telemetry and check for DOCSIS partial service, OFDM/OFDMA profile changes, upstream impairment or ingress, ranging/T3/T4 events, modem flap history, or CMTS/node-side packet loss?
I also previously observed downstream OFDM channel 194 at 1050 MHz intermittently appearing and disappearing from the XB10 status page, so it would be helpful to verify that channel's actual CMTS-side history as well.
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