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StefanB

join:2009-08-27

2 edits

Losing downstream channel.

Hello guys,

since the speed upgrade in March 21st I have been having some issues. My internet drops daily for a few seconds but without the modem (Motorola SB6120) losing any of his lights or going off completely, connections just drops and comes back in less than a minute... I have been checking my modem signals after this connection issue occurs and I keep seeing one of the 4 downstream disappearing every time. The 4 channels come back after I reset the modem but once the disconnection problem happens it goes back to 3.

Can you guys give me some advice before calling support?

Here's a line quality test: »/testhistory/1669893/9160d

I'm located in Miami, FL

Model Name: SB6120
Vendor Name: Motorola
Firmware Name: SB_KOMODO-1.0.6.10-SCM00-NOSH
Boot Version: PSPU-Boot 1.0.0.4m1
Hardware Version: 1.0
Serial Number: 186901917300810405030011
Firmware Build Time: Oct 29 2012 18:07:13




[att=3]


I'll appreciate any help. Thanks!

Stefan B.


pflog
Bueller? Bueller?
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join:2001-09-01
El Dorado Hills, CA
kudos:3

Can you post your line stats when the 4th channel is there as well?
--
"I drank what?" -Socrates


StefanB

join:2009-08-27
reply to StefanB

Sure




pflog
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join:2001-09-01
El Dorado Hills, CA
kudos:3

At face value, the 4th channel looks ok, but keep an eye on the total correctable and uncorrectable. If that channel's numbers are increasing an order of magnitude (or more) than the other three channels, you will be able to call them and tell them which channel/frequency is having trouble.

This may take some patience on your part (see: this thread for a similar situation with noise/interference on some channels).
--
"I drank what?" -Socrates


StefanB

join:2009-08-27

Thanks for your reply, pflog.!

So do you say that I just keep an eye on everything and then call them later with more information? I was about to call Comcast but I realized that it was better to post in here so I can have some advice.

Also, I see that the channel frequency that it is missing on the first image (3 channels) is the first channel on the second image I posted (Frequency 375000000 Hz Channel ID 112) does this means that I have to keep a look at the channel number one? I don't know if that made sense...



pflog
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join:2001-09-01
El Dorado Hills, CA
kudos:3

Yes, that's the channel to keep an eye on. The channel ID or number may change, so keep an eye on the frequency. If it's the same frequency that's there and then drops it could be an issue on that particular frequency. Most likely you'll see the error counts go up sharply, but it may be difficult to catch it before it drops the channel (I'm sure it varies quite a bit from modem to modem how many errors or how much noise they will take before dropping the channel).

How frequently is this occurring? Is it fairly regular? If, say, it happens every 4 hours, try checking the error counts after 1, 2 and 3 hours and see if it's going up a lot. It may not, which could indicate a brief period of extreme noise on the channel causing it to drop.
--
"I drank what?" -Socrates



gar187er
I do this for a living

join:2006-06-24
Dover, DE
kudos:4
reply to pflog

just like to point out the OPs channels are in the 350-400mhz where as the thread you mention his channels are in the LTE band (700-750).
--
I'm better than you!



pflog
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El Dorado Hills, CA
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said by gar187er:

just like to point out the OPs channels are in the 350-400mhz where as the thread you mention his channels are in the LTE band (700-750).

Yep, I was just saying that if there's noise/interference it could be a tough thing to track down. I wasn't implying it's the same issue, just that issues like this can require a lot of patience.
--
"I drank what?" -Socrates

StefanB

join:2009-08-27
reply to pflog

I'll keep an eye on that frequency, as you said it may be difficult to catch it before it happens but if I'm not mistaken it has been happening at night, after 10:00 PM so I'm going to be looking closely and see if I have any luck.

After reading that link you gave me I just wish that's not the issue I'm having. Sounds very complicated and I know I'll have to be very patient and make a lot of calls, it's stressing me just thinking about it heh.

Thanks once again for replying and taking the time to read this topic, guys.



pflog
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El Dorado Hills, CA
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Well as gar187er See Profile pointed out, the frequencies in the other thread were LTE band, so your issue is likely different (and hopefully less troublesome and drawn out). I didn't want to scare you, just wanted to give you a heads up that sometimes these kinds of issues are difficult to track down.

I had a similar issue to yours, but it was on my upstream channel (this was before DOCSIS 3.0 so I had only one upstream channel). Periodically, it would just drop off and lose sync. It took a tech sitting at the tap with a meter watching it for hours before he caught the problem and this was after 2 truck rolls and someone in business class escalations getting involved!

I hope your issue is more cut and dry, chances are it is.
--
"I drank what?" -Socrates



pflog
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join:2001-09-01
El Dorado Hills, CA
kudos:3
reply to StefanB

Granted, I'm basing this entirely on Wikipedia (:p) but it looks like 375 MHz doesn't have a whole lot of possible sources of EMI/RFI:

225–420 MHz: Government use, including meteorology, military aviation, and federal two-way use[3]

If the problem isn't from external EMI/RFI, I'm guessing it's easier to track down. Some HFC experts can probably confirm/deny.
--
"I drank what?" -Socrates

StefanB

join:2009-08-27
reply to pflog

Thank you! I really hope so too... I haven't had any problems with Comcast for a while, it has been working perfectly for a few years but I guess there's always something that could happen, it's weird that happened just after they upgraded the speeds .

Quick question, is there anything to worry about the FAIL status on the line quality test?



pflog
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join:2001-09-01
El Dorado Hills, CA
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In your case it looks like it's a specific route issue so I think you're ok.

The "Central - USA" test has no packet loss, but the West coast one does.

Could be related to your problem, but looks more like a routing issue between you and the west coast test server.
--
"I drank what?" -Socrates


StefanB

join:2009-08-27

Perfect, I'm not going to worry much about it then. Maybe it will get fixed whenever this issue I'm having is gone.

About the Wikipedia link, that's very interesting. Seems like there's not many sources that can possibly cause some issues as you said, that makes me feel more at ease .

You're awesome, pflog... I really appreciate your time helping me and quick replies.



pflog
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said by StefanB:

I really appreciate your time helping me and quick replies.

No problem, glad to try and help. Let us know how the monitoring of that channel goes and if you end up calling support have them send someone out. At least when the tech shows up you will be able to say "the channel on 375 MHz keeps dropping" and tell him if there are tons of errors or not. That should hopefully point them in a direction to investigate.
--
"I drank what?" -Socrates

n_w95482
Premium
join:2005-08-03
Ukiah, CA
reply to pflog

I'm not sure if the same servers are used for both, but when I ran a Smokeping test for a week a little while ago, the west coast server showed more jitter and packet loss. The Kansas server's results looked much better. I ended up using that one as its results coincided with my connectivity issues.
--
KI6RIT


StefanB

join:2009-08-27
reply to StefanB

So I haven't lost any bonding channel yet, I noticed a bit of slow speeds earlier but not much else... I just checked the stats and I don't know if the Total Uncorrectable Codewords is a bit too high compared to what I had before, can you guys tell me if this are normal numbers? The channel that I have been having issues is the one that has more Uncorrectable ones.




pflog
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El Dorado Hills, CA
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I don't think 1.5-2x the correctables is a big deal. I'd think if the channel had issues, then they'd be an order of magnitude higher (or more). But this is starting to look like a short period of severe noise/issues is the cause, not a persistent noise on the channel.
--
"I drank what?" -Socrates


StefanB

join:2009-08-27

Hello once again, pflog! Thanks for jumping in

Yeah I also think is something that only happens for a short period of time and that's when I start to have the issues mentioned above. What do you think I should do? Keep an eye on it or should I call and let them know? I think that even if a tech comes nothing is going to get fixed since this is an intermittent problem...



pflog
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join:2001-09-01
El Dorado Hills, CA
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Yeah this is going to be tough, especially if it occurs at night or out of normal tech business hours. The most you can do is call them and tell them which channel/frequency is failing intermittently and then when they send a tech make sure to tell them that info.
--
"I drank what?" -Socrates


StefanB

join:2009-08-27

I'm probably going to wait maybe a few more days and see how things go and if I keep getting issues I'll give them a call for sure.

Thank you, pflog .