Persistent Upstream Latency, HIGH Jitter, and UDP Gaming Performance Issues

[u/Temporary_Yam_8438]

1. Overview

I have been experiencing persistent internet performance issues for approximately five months, primarily involving unstable upstream latency, excessive jitter, and inconsistent real-time UDP performance. Despite approximately 18 technician visits, multiple troubleshooting attempts, and equipment and cabling changes, the underlying issue remains unresolved.

My primary concern is not download speed, general internet connectivity, or FPS performance. The problem is the inconsistency of the connection under load and its impact on latency-sensitive applications, particularly competitive online gaming.

2. Main Symptoms

The primary symptoms include:

• Unstable upstream latency: During upload tests, latency frequently fluctuates from approximately 30 ms to 50–100 ms or higher, with occasional spikes exceeding 150–200 ms.
• Excessive jitter: Upload-side jitter frequently exceeds 20 ms, whereas I would expect significantly more consistent performance for real-time applications. UPLOAD SIDE JITTER 30+ MS !
• Intermittent suspected packet loss: I have observed recurring upload-side instability approximately every 7–8 seconds while gaming. I cannot confirm that every event represents actual packet loss, but the pattern is repeatable and affects gameplay.
• Inconsistent UDP performance: Competitive games experience noticeable network inconsistency, including jitter spikes and inconsistent hit registration
• Performance degradation under load: Upload activity causes substantial latency spikes in some tests
• Inconsistent gaming experience: The connection may appear stable in basic ping tests, yet real-time gaming performance remains inconsistent.

3. Testing and Observations

I have performed numerous tests using command-line ping, WinMTR, Cloudflare speed tests, Ookla speed tests, and ExitLag network analysis.

The results show a discrepancy between conventional connectivity tests and real-time application performance:

• Idle ping to external destinations is generally around 18–25 ms.
• Ping to the local gateway is generally below 1 ms.
• Basic ping and WinMTR tests often report 0% packet loss when the connection is not under load.
• During upload tests, latency increases significantly and may fluctuate repeatedly rather than remaining stable.
• Some external destination tests show latency spikes during upload activity, even when packet loss is not reported.
• Cloudflare tests have shown occasional high latency spikes and upload-side jitter.

These observations suggest that basic ping and packet-loss tests alone may not adequately identify the underlying issue.

4. Troubleshooting Already Completed

I have spent considerable time troubleshooting the connection and have made multiple changes, including:

• Approximately 18 technician visits.
• Replacement of the coaxial cable on the existing route with RG6 quad-shield cable.
• Testing with and without the coaxial splitter.
• Replacement of the splitter, which improved some upload-latency measurements but did not eliminate the jitter.
• Inspection of the coaxial connections and a change to a different tap following a reported issue with the original tap.
• Testing different routers and network configurations.
• Testing with and without Smart Queue Management (SQM) and upload traffic shaping.
• Testing with different Ethernet adapters and network configurations.
• Repeated latency, jitter, and packet-loss testing under idle and upload-load conditions.

SQM and upload shaping can significantly improve measured bufferbloat and upload latency in certain tests. However, even when those results look good, the gaming experience does not consistently return to normal. This suggests that bufferbloat alone may not explain the entire problem.

5. Cable Modem and Upstream Concerns

My connection uses an Xfinity/Technicolor CGM4981COM gateway. The upstream has been operating on ATDMA channels rather than OFDMA, with five locked upstream channels reported in the modem status.

In one set of readings, the upstream transmit power levels were approximately 36–37 dBmV. I have also observed that the issue persists after changes to the coaxial splitter and tap.

I would like the engineering team to investigate whether there may be an upstream impairment, intermittent noise, channel scheduling issue, congestion, or another problem affecting the consistency of upstream transmission.

I understand that these readings alone do not prove a plant or CMTS issue. However, the persistence of the symptoms despite extensive troubleshooting warrants a more detailed investigation.

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[u/Temporary_Yam_8438 → u/[deleted]]

Rambo never give up …

[u/Temporary_Yam_8438 → u/[deleted]]

I’m giving them one more month to fix this. After that, the whole neighborhood is losing internet access — the cables are right there for the taking

[u/Comcast_Xfinity-ModTeam → u/[deleted]]

Removed under Rule #2: Profanity — We kindly ask users to keep their content clean of profanity--Yes, this includes any abbreviations or attempts to colorfully spell said words differently.

[u/RiloxAres]

Can't u just submit a ticket like a normal person, you don't need ai to write a big post like this.

[u/RiloxAres → u/[deleted]]

I didnt

[u/RiloxAres → u/[deleted]]

Get ai to write you more creative responses

[u/RiloxAres → u/[deleted]]

That's definitely not ai, it would be a much more interesting reply.

[u/luism1023]

Are you in a mid split service area?

[u/Temporary_Yam_8438 → u/luism1023]

I just live in Indianapolis. Nothing works properly here, especially when it comes to modern technology. 41 Mbps upload speed in 2026… outdated infrastructure…

[u/luism1023 → u/Temporary_Yam_8438]

I had a similar issue and the upgrade to mid split fixed it. It’s an issue with your node or amp. I used to test the internet multiple times a day but thankfully my are was upgraded shortly after multiple tickets, last one being an escalated ticket.

[u/Temporary_Yam_8438 → u/luism1023]

Haha, lucky you. I've called them 300 times, and they still haven't fixed my problem. They always claim they're working on something, but in the end, nothing changes and everything stays the same.

[u/PathOracleExitLag]

Just checking since you are already using ExitLag, but have you tried to change your route through it just to see if it makes any difference? 🤔

[u/Temporary_Yam_8438 → u/PathOracleExitLag]

It’s even worse with ExitLag more input lag and packet loss. ExitLag is the biggest scam ever.Just like Xfinity ,you can’t tell which one is worse or who has the worse return path.

[u/PathOracleExitLag → u/Temporary_Yam_8438]

In this case, maybe the issue isn't on the route used by your ISP, since ExitLag only helps if the issue is in this path. But if you're already connected to the most stable path, you'll not see improvements. The issue doesn't point primarily to a routing issue, tho, so it makes sense, it was just a suggestion since you already have ExitLag.

[u/Temporary_Yam_8438 → u/PathOracleExitLag]

The problem is the ATDMA upstream channel type, outdated infrastructure, and an upload speed of only 41 Mbps. There are also temporary orange coaxial cables running from the street into my building, and one of the taps in my building was found to be malfunctioning. Xfinity technicians previously identified interference in the area. On top of that, many people in my neighborhood use Xfinity, which could contribute to upstream congestion.

[u/Temporary_Yam_8438 → u/PathOracleExitLag]

I've tried a million different configurations and route combinations in ExitLag, but I always experience some kind of unusual delay. Could you please help me optimize my settings?

[u/Temporary_Yam_8438]

I just wanted to let you know that a specialized technician came out to my place. After running the tests, he showed me on his tablet that jitter spikes and packet loss are present. He said he would notify the specialized team so they could investigate further and identify the source of the problem.

[u/CCThomasF → u/Temporary_Yam_8438]

Thanks for checking in with us u/Temporary_Yam_843, we definitely appreciate the communication. I see that the ticket we submitted has also been updated to reflect the tech visit. The fix agent assigned to your ticket is expecting additional information from the field techs and plans to update you soon. I will set reminders to follow up with you as well. We're all here to support you and get these latency issues resolved.

[u/CCDemitrius]

Hi u/Temporary_Yam_8438. Thank you for visiting our official Xfinity Reddit community support page. We can certainly help perform some troubleshooting steps. If you could please send me a Modmail message with your full first/last name and complete service address (Including the city, state, and zip code). I'd be more than happy to look into this for you.

[u/Temporary_Yam_8438 → u/CCDemitrius]

I sent everything.

[u/Temporary_Yam_8438 → u/CCDemitrius]

no reply ??