Internet keeps dropping randomly through out the day - T3 time-out in Logs

[patelarpit]

Hello guys,

My internet keeps on dropping randomly throughout the day then it connects back up after 5 to 10 min later.  This had happened to me a few years ago and they had to put in a new cable in the back from the junction box to my house and it worked fine up to last week. I am having the same issue that I did, my speed has gone down and also the connection is also been flaky. I have troubleshot this with the best of my ability and it looks like there is some sort of signal issue from the junction box to my house or something. As I am seeing T3 time-out in my modem logs when the internet disconnects. We work from home and this is really affecting our productivity. Like the following:

Mon Apr 20 07:38:25 2020	Warning (5)	MDD message timeout;CM-MAC=xxxxxx;CMTS-MAC=xxxxxx;CM-QOS=1.1;CM-VER=3.0;
Mon Apr 20 07:38:25 2020	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=xxxxxx;CMTS-MAC=xxxxxx;CM-QOS=1.1;CM-VER=3.0;
Mon Apr 20 07:39:12 2020	Warning (5)	MDD message timeout;CM-MAC=xxxxxxCMTS-MAC=xxxxxx;CM-QOS=1.1;CM-VER=3.0;
Mon Apr 20 07:39:12 2020	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=xxxxxx;CMTS-MAC=xxxxxx;CM-QOS=1.1;CM-VER=3.0;
Mon Apr 20 07:40:23 2020	Warning (5)	MDD message timeout;CM-MAC=xxxxxx;CMTS-MAC=xxxxxx;CM-QOS=1.1;CM-VER=3.0;
Mon Apr 20 07:40:23 2020	Critical (3)	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=xxxxxx;CMTS-MAC=xxxxxx;CM-QOS=1.1;CM-VER=3.0;
Mon Apr 20 07:55:57 2020	Warning (5)	MDD message timeout;CM-MAC=xxxxxx;CMTS-MAC=xxxxxx;CM-QOS=1.1;CM-VER=3.0;

Also, my signal snapshot is here:

Downstream Bonded Channels
Channel	Lock Status	Modulation	Channel ID	Frequency	Power	SNR	Corrected	Uncorrectables
1	Locked	QAM256	17	621000000 Hz	5.0 dBmV	39.2 dB	71010864	38503806
2	Locked	QAM256	18	627000000 Hz	5.1 dBmV	35.3 dB	38274307	182122361
3	Locked	QAM256	19	633000000 Hz	5.2 dBmV	39.2 dB	41945168	200454010
4	Locked	QAM256	20	639000000 Hz	5.1 dBmV	29.8 dB	8847032	6099722
5	Locked	QAM256	21	645000000 Hz	5.0 dBmV	0.0 dB	786846	4276852
6	Locked	QAM256	22	651000000 Hz	4.9 dBmV	37.7 dB	33423600	17075206
7	Locked	QAM256	23	657000000 Hz	4.7 dBmV	41.4 dB	0	0
8	Locked	QAM256	24	663000000 Hz	4.4 dBmV	41.3 dB	0	0
9	Locked	QAM256	25	669000000 Hz	4.6 dBmV	41.6 dB	17	55
10	Locked	QAM256	26	675000000 Hz	4.4 dBmV	40.8 dB	21	69
11	Locked	QAM256	27	681000000 Hz	4.3 dBmV	41.6 dB	24	93
12	Locked	QAM256	28	687000000 Hz	4.2 dBmV	41.6 dB	22	71
13	Locked	QAM256	29	693000000 Hz	3.9 dBmV	41.4 dB	17	68
14	Locked	QAM256	30	699000000 Hz	3.9 dBmV	41.5 dB	6	43
15	Locked	QAM256	31	705000000 Hz	3.9 dBmV	41.6 dB	17	66
16	Locked	QAM256	32	711000000 Hz	4.1 dBmV	41.8 dB	15	79

Upstream Bonded Channels
Channel	Lock Status	US Channel Type	Channel ID	Symbol Rate	Frequency	Power
1	Locked	ATDMA	4	5120 Ksym/sec	16600000 Hz	41.0 dBmV
2	Locked	ATDMA	1	5120 Ksym/sec	35800000 Hz	39.5 dBmV
3	Locked	ATDMA	2	5120 Ksym/sec	29400000 Hz	40.5 dBmV
4	Locked	ATDMA	3	5120 Ksym/sec	23000000 Hz	40.3 dBmV

[EG]

The SNR is too low / out of spec on some of the downstream channels. Seems that there is some noise ingressing into the line(s) somewhere at those frequencies. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, and latency problems.

In a self troubleshooting effort to try to obtain better connectivity, 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.

[patelarpit]

Thank you for the reply, I have no splitters in my house. I went through this troubleshooting and learned my lesson a couple of years ago, so now I have a straight cable that comes into the modem from outside.  What is the range of ideal SNRs?

[EG]

Specification	Min	Max
Downstream Power Level
Cable Modems	-10dBmV	+10dBmV
Gateways and EMTAs	-7dBmV	+7dBmV
Downstream Signal to Noise Ratio	35dB	-
Upstream Power Level	+35dBmV	+50dBmV
Upstream Signal to Noise Ratio	31dB	-
Upstream Receive Power	-2dBmV	+2dBmV

Then you'll need a tech out to investigate. 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 with it !