One gig intranet service

Hello,

I’m contacting you regarding consistently lower-than-expected download speeds on my Xfinity Gigabit internet service. I have completed extensive troubleshooting to eliminate my home Wi-Fi/router as the cause.

I am using an ARRIS SURFboard S33 DOCSIS 3.1 modem. For testing, I completely bypassed my AmpliFi router and connected a Dell laptop directly to the S33 via Ethernet. Windows confirms that the Ethernet connection is negotiating at 1000/1000 Mbps.

I power-cycled the modem and performed multiple wired speed tests. Results have varied considerably, with download speeds generally around 300–590 Mbps, despite the Gigabit service. Upload speeds have generally been around 40–43 Mbps. For example, a recent Ookla test measured approximately 297 Mbps down / 41 Mbps up, while Fast.com tests have ranged from approximately 410–590 Mbps down.

I also checked the modem’s RF status. With the existing PPC CS9-860 cable simulator installed, the S33 reported approximately +2 dBmV downstream power and 43 dB SNR. I temporarily bypassed the CS9-860 for troubleshooting, which changed the readings to approximately +8 dBmV and 44 dB SNR, but download performance did not materially improve. I have therefore returned the coax configuration to its original setup.

Could you please:

• Verify that my S33 is provisioned with the correct Gigabit service boot/configuration file.
• Review the modem’s downstream and upstream channel levels, including the DOCSIS 3.1 OFDM channel.
• Check corrected/uncorrectable errors and upstream transmit levels.
• Check for any node, congestion, signal, or line issues that could explain the large variation and lower-than-expected wired download speeds.
• Re-provision the modem if appropriate.

Because these tests were performed with the computer directly connected to the modem, the results are not from Wi-Fi or my router.

I would appreciate having the connection investigated before considering a lower-speed plan, since I would first like to determine whether my current Gigabit service is performing as intended.

Thank you.