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Intermittent connection loss, fluctuating upstream power

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Intermittent connection loss, fluctuating upstream power

I've been fighting intermittent connection loss for a few years, across multiple modems and configurations. The common theme seems to be upstream power levels which usually run around 49dBmV but sometimes jump into the high 50s - usually associated with quite a few rounds of the modem reboot/reconnect cycle. The current setup has an Arris SB8200, behind a two-way split from the incoming line, with a single MoCA filter just upstream of the splitter. Last week I thought I had finally narrowed down the issue to a bad splitter, which I replaced. This brought the upstream power seen on the modem from about 55 dBmV down to 49, and got us 4 locked channels instead of 1. Downstream power and SNR improved considerably as well.

We just got back from a short vacation, though, and the old problem seems to have returned. This afternoon we lost connection for about half an hour; at one point I saw a single-channel upstream connection at 59 dBmV. Now, the levels seem to have returned to "normal" but with a single upstream channel locked.

 

I've seen many different takes on how to resolve these (common?) issues, and I'd like to try to end the connection loss once and for all. I'll post the current modem status page as well as the recent error logs (showing the problem a couple of times) below.

 

Status Page:

Startup Procedure
ProcedureStatusComment
Acquire Downstream Channel597000000 HzLocked
Connectivity StateOKOperational
Boot StateOKOperational
Configuration FileOK 
SecurityEnabledBPI+
DOCSIS Network Access EnabledAllowed 

 

 
Downstream Bonded Channels
Channel IDLock StatusModulationFrequencyPowerSNR/MERCorrectedUncorrectables
25LockedQAM256597000000 Hz-2.9 dBmV38.0 dB246176585
1LockedQAM256453000000 Hz-2.5 dBmV38.8 dB3908718452
2LockedQAM256459000000 Hz-2.2 dBmV38.8 dB3654515980
3LockedQAM256465000000 Hz-2.1 dBmV38.8 dB3752017582
4LockedQAM256471000000 Hz-1.8 dBmV38.9 dB3795816435
5LockedQAM256477000000 Hz-1.8 dBmV38.9 dB3589414275
6LockedQAM256483000000 Hz-1.6 dBmV38.9 dB3636714840
7LockedQAM256489000000 Hz-2.0 dBmV38.6 dB253327867
8LockedQAM256495000000 Hz-2.0 dBmV38.6 dB275119118
9LockedQAM256501000000 Hz-2.3 dBmV38.3 dB2879610527
10LockedQAM256507000000 Hz-2.4 dBmV38.4 dB3970820704
11LockedQAM256513000000 Hz-2.9 dBmV38.3 dB4286425378
12LockedQAM256519000000 Hz-2.7 dBmV38.1 dB4843532119
13LockedQAM256525000000 Hz-3.0 dBmV38.2 dB4079119752
14LockedQAM256531000000 Hz-2.8 dBmV38.4 dB4112319256
15LockedQAM256537000000 Hz-3.1 dBmV38.2 dB4265022281
16LockedQAM256543000000 Hz-2.9 dBmV38.2 dB4387824541
17LockedQAM256549000000 Hz-3.0 dBmV38.4 dB4163822430
18LockedQAM256555000000 Hz-2.8 dBmV38.5 dB3863718582
19LockedQAM256561000000 Hz-2.9 dBmV38.4 dB3821717443
20LockedQAM256567000000 Hz-2.9 dBmV38.5 dB3843518730
21LockedQAM256573000000 Hz-2.7 dBmV38.5 dB3938820261
22LockedQAM256579000000 Hz-2.9 dBmV38.3 dB3760418799
23LockedQAM256585000000 Hz-3.0 dBmV38.2 dB3726417169
24LockedQAM256591000000 Hz-3.1 dBmV38.1 dB3733116551
26LockedQAM256603000000 Hz-3.0 dBmV38.0 dB3950518810
27LockedQAM256609000000 Hz-3.2 dBmV38.2 dB3934717957
28LockedQAM256615000000 Hz-2.9 dBmV38.2 dB3672115307
29LockedQAM256621000000 Hz-2.9 dBmV38.1 dB3643214659
30LockedQAM256627000000 Hz-2.8 dBmV38.3 dB3671215971
31LockedQAM256633000000 Hz-3.0 dBmV38.3 dB3648815094
32LockedQAM256639000000 Hz-2.8 dBmV38.4 dB3505612999
159LockedOther722000000 Hz0.2 dBmV37.2 dB179841997149


 

 
Upstream Bonded Channels
ChannelChannel IDLock StatusUS Channel TypeFrequencyWidthPower
11LockedSC-QAM Upstream36100000 Hz6400000 Hz49.0 dBmV


 

 

Current System Time: Mon Oct 19 12:54:32 2020

 

Event Log:

Date Time Event ID Event Level Description

10/19/2020 12:33840005003"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
01/01/1970 00:0724366940666"Honoring MDD; IP provisioning mode = IPv6"
01/01/1970 00:07840001003"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
01/01/1970 00:05820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
01/01/1970 00:01840001003"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
01/01/1970 00:00820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
01/01/1970 00:00840001003"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
10/19/2020 12:11820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/19/2020 12:07820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/19/2020 11:55820005003"Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:36840005003"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:23820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:23840001003"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:22820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:21840001003"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:20820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:18820005003"Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:18820002003"No Ranging Response received - T3 time-out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:18820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:16820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:15820002003"No Ranging Response received - T3 time-out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:15820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:15820002003"No Ranging Response received - T3 time-out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:14820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:14820004003"Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:14820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:08820004003"Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:08820002003"No Ranging Response received - T3 time-out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:08820004003"Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:08820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:01820004003"Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 15:01820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:44840001003"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:43820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:42840001003"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:41820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:39820005003"Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:37820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:32840001003"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:31820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:31840001003"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:29820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:25840001003"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:24820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:24840001003"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:23820007003"Unicast Ranging Received Abort Response - Re-initializing MAC;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:21820004003"Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:21820004003"Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:20820004003"Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
10/18/2020 14:20820004003"Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=d4:3f:cb:e6:05:31;CMTS-MAC=84:8a:8d:f0:d1:60;CM-QOS=1.1;CM-VER=3.1;"
Highlighted
Expert

Re: Intermittent connection loss, fluctuating upstream power

49 dB is almost out of spec and it doesn't allow much wiggle room for intermittent fluctuations.

 

If nothing below applies, you'll need to geta a tech out to investigate / correct the problem;

 

In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two way splitter connected directly off of the drop from the street/pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed, and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.

 

Also, bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home.
Good luck !



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I am a Customer Expert volunteering my time to help other customers here in the Forums.
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New Poster

Re: Intermittent connection loss, fluctuating upstream power

Thanks for the insight.

 

The "ideal" configuration described is exactly what we have currently (a single two-way splitter off the drop, with one leg directly to the modem and the other to the DVR etc.). I'm not sure exactly which brands of splitters are good quality - and I thought I had read somewhere that DOCSIS 3.1 might require a splitter rated for up to 1600MHz. In any case the current splitter is a GE rated for 5 - 2500 MHz. We've verified by connecting the modem directly without a splitter that the current splitter has about the expected 3 dBmV of loss.

We've also disconnected, reconnected, etc. everything a few times, usually with no result. I am wondering if there is something wrong at the tap or upstream - this neighborhood has grown quite a bit since we moved in and I suspect our configuration might be tuned for the mid 2000s rather than DOCSIS 3.1 and so on. I have noticed that sometimes it's possible to reach someone via the forums who has the ability to collect some additional diagnostics and was hoping we might learn something more specific to help out the technician(s) before making a service call.

Highlighted
Expert

Re: Intermittent connection loss, fluctuating upstream power


@dwt_ wrote:

Thanks for the insight.

 

I'm not sure exactly which brands of splitters are good quality -

 

Here are some quality brand splitters that Comcast actually uses in different market areas;

Antronix CMC2002H 2-Way Splitter: http://www.amazon.com/Antronix-CMC2002H-2-Way-Splitter/dp/B001E4OH1E

Regal 2 WAY 1 GHZ Splitter: http://www.amazon.com/DIG702867-Regal-WAY-GHZ-SPLITTER/dp/B0018BQMUM/ref=sr_1_2?s=electronics&ie=UTF...

Extreme Broadband BDS102H 2-Way Digital Coax Splitter: http://www.amazon.com/EXTREME-DIGITAL-PERFORMANCE-CABLE-SPLITTER/dp/B007YV0UQW

Holland 2-way horizontal splitter 5-1000 MHz with ground.http://www.3starinc.com/holland_2-way_horizontal_splitter_5-1000_mhz-w-ground.html

Sv-2g 2-way Splitter 5-1000mhz: http://www.amazon.com/Sv-2g-2-way-Splitter-5-1000mhz-Sv2g/dp/B003TH36CK

and I thought I had read somewhere that DOCSIS 3.1 might require a splitter rated for up to 1600MHz.

 

Nope. That is for MoCA band passing. Like this one;

 

http://www.amazon.com/Holland-Electronics-GHS-2Pro-M-Splitter-5-1675Mhz/dp/B00P6VHLP0?tag=ds0233-20 /www.amazon.com/Ohm-Terminator-4-Pack-Cable-Connections/dp/B0016A986K

 

In any case the current splitter is a GE rated for 5 - 2500 MHz. 

 

Be advised that this may or may not be the root cause of the problem, but you should swap out that splitter. It is engineered more for satellite systems, not cable systems. It can actually make performance worse by allowing line noise ingress at those higher frequencies that cable systems do not operate on.


So as I stated a couple of times, it may be tech time.  Bear in mind that if the premises facing techs can not find or fix a problem at your home, it is they who are responsible for escalating it to their line / network / maintenance dept. techs. The problem may lie beyond your home in the local neighborhood infrastructure somewhere but it is their S.O.P. to start at the home.
Good luck !



I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Mark the post as Best Answer!