Out-of-spec downstream power + documented 48hr degradation — requesting line technician

Good catch — let me give you the full version with everything Winter has gathered. This is the stronger post.

Category: Your Home Network Topic/sub-category: Internet (or "Connection Issues" if available)

Subject: Out-of-spec downstream power + documented 48hr degradation — requesting line technician

Body:

Service plan: Gigabit Extra (~941/43 Mbps) Modem: Arris Surfboard S33v2 (DOCSIS 3.1), firmware TB01.03.001.11 Location: Mount Laurel, NJ

I have 48 hours of continuous documented evidence showing intermittent service degradation with root cause on the plant side. Summary below; full diagnostic logs available via DM.

Modem signal readings (current):

• Downstream Signal Power: -11 dBmV (DOCSIS spec: -7 to +7 dBmV — out of spec by 4 dB)
• Downstream Signal SNR: 35 dB (minimum for QAM256: 36 dB — below spec)
• Downstream Frequency: 567 MHz

Throughput delivery (48hr continuous speedtest sampling, wired host):

• Measured: 512–704 Mbps down, 32–38 Mbps up
• Delivered: 54–75% of provisioned plan
• Consistent under-delivery across all sampling windows, not transient

Latency analysis (continuous ping monitoring, 5-second interval to 1.1.1.1 and 8.8.8.8):

• Idle baseline: 16–21ms
• Spikes to 244ms under load
• 9 of 10 recent 5-minute windows flagged with elevated latency (20–46ms average)

Traceroute analysis (every 2 hours):

• Hop 2 (Comcast CMTS): 14–29ms latency variance — modem-to-node segment
• Hop 9 (Newark peering): occasional packet loss
• Latency variance originates at Hop 2 = plant-side, not in-home

Bufferbloat testing (Waveform.com, wired):

• Current grade: A under controlled conditions (SQM on home router)
• Peak loaded latency observed: 244ms during degradation events
• Pattern: ~80% of time within spec, ~20% degraded — consistent with intermittent plant issue

In-home equipment ruled out:

• All tests run from wired host behind professional-grade gateway (Ubiquiti UDM Pro)
• Smart Queue Management (CAKE) enabled on WAN with confirmed correct algorithm
• DNS, switching, and WiFi all verified clean
• Throughput and latency degradation occur regardless of in-home load

Diagnosis: Downstream power 4 dB below DOCSIS spec, combined with SNR below QAM256 minimum, is consistent with attenuation on the drop or tap side. The intermittent nature of latency spikes and throughput drops, combined with Hop 2 variance, indicates plant-side instability — likely corroded F-connector, damaged drop, water-damaged tap port, or attenuation from upstream amplifier.

Request:

Please dispatch a line technician for plant-side signal investigation at the tap and amplifier serving my address.

I am specifically not requesting:

• A modem swap (modem is reporting accurately and functioning correctly given signal received)
• An in-home technician visit (issue is documented upstream of demarc)
• A modem reboot (already verified; signal levels persist)

Happy to provide full diagnostic logs (PDF report with continuous ping data, MTR traces, speedtest history, and bufferbloat measurements) via DM upon request.