Intermittent internet outages during video conferences, DOCSIS T3 timeouts and repeated DRW violations

I'm experiencing intermittent internet connectivity problems, particularly when two people in my household are participating in Zoom or Google Meet video conferences simultaneously.

When the issue occurs, both video calls freeze, and even basic web browsing stops working. Connectivity eventually recovers without rebooting any equipment, but the interruptions are disruptive enough that we've had to switch to cellular hotspots to continue our meetings.

I've performed extensive troubleshooting on my home network and would appreciate help investigating whether there is an underlying cable signal or DOCSIS connectivity problem.

Equipment and service

• ISP: Xfinity, 1 Gbps download plan

• Modem: Arris SURFboard SB8200 (DOCSIS 3.1)

• Router: Ubiquiti EdgeRouter 4

• Home network: Wired Ethernet and UniFi Wi-Fi access points

Modem errors

On November 4, 2026, at approximately 8:05 PM PST, my modem recorded the following events:

• T3 timeout: "No Ranging Response received"

• Downstream profile assignment change

These occurred shortly after we joined a video conference at approximately 8:03 PM, during which we experienced a connectivity interruption.

The modem's event log also contains:

• Repeated Dynamic Range Window violations, including "RNG-RSP CCAP Commanded Power Exceeds Value Corresponding to the Top of the DRW"

• Additional T3 ranging timeouts

• Historical T4 timeouts and synchronization failures

Signal levels and performance

The modem's current signal levels appear normal:

• Downstream power: approximately -3.6 to -1.8 dBmV

• Downstream SNR/MER: approximately 37.8–40.7 dB

• Upstream transmit power: 43–44 dBmV across six locked channels

• No downstream uncorrectable codewords reported in the captured status

Wired speed tests using the official Ookla CLI consistently achieve:

• Download: 929–940 Mbps

• Upload: approximately 42 Mbps

• Idle latency: approximately 10 ms

• Packet loss: 0% during testing

This appears to be an intermittent connectivity problem rather than a persistent bandwidth limitation.

I've also verified that the local wired network operates at gigabit speeds and have configured continuous monitoring of my router, cable modem, DNS server, and external internet connectivity.

Request for assistance

Could an Xfinity technician investigate the upstream signal quality and historical DOCSIS events associated with my modem?

Specifically, I'd appreciate checking:

1. Upstream receive MER/SNR and receive power at the CMTS.

2. Historical T3/T4 ranging failures, modem flaps, or re-registrations.

3. Whether upstream noise, ingress, or intermittent signal impairment is present.

4. Whether there were any network-side issues around November 4, 2026, at approximately 8:05 PM PST.

5. Whether other modems on the same node have experienced similar problems.

I understand that occasional T3 errors can occur without causing service interruptions, and I haven't conclusively established that these errors caused the video conference failures. However, their timing and the repeated Dynamic Range Window violations make me concerned about an intermittent upstream issue.

I'd appreciate having the connection's historical signal health reviewed rather than simply running another speed test, since throughput is excellent when the connection is functioning normally.

I can provide the modem's full event log and signal-level readings if helpful.

Thank you for your assistance.