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Intermittent Long Periods of Packet Loss

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Official Employee

Re: Intermittent Long Periods of Packet Loss

Hi @ZoomEnhance


I can check the node to see if I'm able to see anything that is contributing to your issues. Can you please verify your first and last name, and the phone number or account number associated with your services in a private message? 


To send a private message click on my name "ComcastChe", then click private message me.


Re: Intermittent Long Periods of Packet Loss

Yes, your images are viewable, at least to me. The forums do some funky thing that does not let some users view images. ¯\_(ツ)_/¯

I am not a Comcast employee, just a moderator. Pls observe Wheaton's Law.
Regular Visitor

Re: Intermittent Long Periods of Packet Loss

Thank you very much for the quick response!

To make sure I'm providing as much info as possible, are the images I uploaded properly visible?

I noticed I cannot view them unless I am logged in to my account and wanted to make sure they weren't listed as private etc.


Re: Intermittent Long Periods of Packet Loss

Hi @ZoomEnhance,

Since you've already had techs out... I've asked an employee to review your account and check your node health. 

You should expect a reply in this thread. 


FYI: They owe you a $20 credit for every tech visit after the first for the same problem.You can also get a credit for your service from the time you first reported the issue until it is resolved.

I am not a Comcast employee, just a moderator. Pls observe Wheaton's Law.
Regular Visitor

Intermittent Long Periods of Packet Loss

For the past month, I have been experiencing intermittent periods of packet loss and high latency spikes. I first recorded the problem on March 2nd, however it is possible it began occurring before that. The issues have occurred at random periods of time ranging between around 4 hours and over 36 hours long since then. The packet loss may range from around 2% to 6% or higher across an average, with spikes of complete loss lasting a few seconds.

The issues affect all types of applications, with the effects most noticeable in real-time applications such as games and voice clients. The issue causes games that use lockstep netcode to be 'unplayable' with frequent complete losses of responsiveness, while other games experience large spikes of delay. The problems extend to normal browsing and streaming as well, with pages having a randomly delayed load time, and video occasionally freezing/buffering or reducing playback quality.


Download speeds do not seem to be reduced, however my upload speeds will jitter between 4Mbps and 25Mbps when tested on the Xfinity speed test.
Checking the logs on my current modem, I see over 100 T3 timeouts in a 24-hour period.

([Docsis][1001]: No Ranging Response received - T3 time-out)

The gateway is a Cisco DPC3941T XB3.


The issue comes and goes seemingly without reason or pattern.

My signal levels taken while the issue was occurring last are below:


On the initial support call I made, I asked for the Upstream Recieve power level and was told it was in the red at a reading of 10. (I believe they said +10 in specific.) Techs that were at the house did not seem to see this problem, however I am not sure if it those levels are visible to them.


My latency and packet loss over a typical route looks like this:

plotter_long.pngLong period of packet loss on original modem

plotter_close.pngCloser detail of latest period of packet loss on new modem


I have tested multiple addresses and all show packet loss originating by the first hop and continuing to the end. (Tested ping intervals between 0.5 seconds to 2.5 seconds and the results are the same.)

I have also tested the connection from other locations to mine. They show no packet loss until the last hop to my location, which closely matches the results I have been getting outbound.


Likewise, Smokeping produces similar results:



In-application latency monitors show the issue in the form of very high latency spikes which match up with packet loss readings on Pingplotter:




I have repeated my tests on multiple PCs using both hard-wired and Wi-Fi connections. All show the same results. The only splitter I am using is a single active return amplifier with the modem on the passive line.

Techs have checked my wiring and replaced my modem to troubleshoot the issue, but nothing so far has made any difference. I have been in contact with a tech supervisor as well, who has been helpful, however we have not yet been able to determine the cause of the issue.
I believe a line tech was supposed to come out at one point, however I have not heard anything from them.


Is there anything else I should test or information I could get to help finally resolve this issue?
Any assistance would be greatly appreciated.