SYNC Timing Synchronization failure

shayward · ‎09-28-2020

I have Xfinity 1Gb/s plan running with a Arris SB8200 modem. The rest of the network is a Unifi USG, 2x Unifi 8 POE switches and 2x Unifi AC-Pros. Most of my devices are connected via ethernet but every so often my internet just goes out; my wife and I work from home so this is not only embarrasing but incredibly depressing that moving is on the table just to no longer have to deal with Comcast as a whole. I've complained about these issues via their phone support at some point in the past three years and they sent a tech whom added a cap thats on the coax between the modem and the line running from outside the building which seemed to work but only for a very short amount of time. It dropped so frequently in the past that I had to buy a remote power IP switch that power cycles our modem whenever the device can no longer connect to the internet which is absolutely maddening. Below are the logs from the modem:

Downstream Bonded Channels
Channel ID	Lock Status	Modulation	Frequency	Power	SNR/MER	Corrected	Uncorrectables
1	Locked	QAM256	441000000 Hz	-4.2 dBmV	42.6 dB	0	0
2	Locked	QAM256	447000000 Hz	-3.5 dBmV	42.6 dB	0	0
3	Locked	QAM256	453000000 Hz	-3.6 dBmV	42.8 dB	0	0
4	Locked	QAM256	459000000 Hz	-3.5 dBmV	42.8 dB	0	0
5	Locked	QAM256	465000000 Hz	-3.3 dBmV	42.9 dB	0	0
6	Locked	QAM256	471000000 Hz	-3.7 dBmV	42.6 dB	0	0
7	Locked	QAM256	477000000 Hz	-2.9 dBmV	42.9 dB	0	0
8	Locked	QAM256	483000000 Hz	-3.3 dBmV	42.7 dB	0	0
9	Locked	QAM256	489000000 Hz	-3.0 dBmV	42.6 dB	0	0
10	Locked	QAM256	507000000 Hz	-2.5 dBmV	43.1 dB	0	0
11	Locked	QAM256	513000000 Hz	-2.9 dBmV	42.9 dB	0	0
12	Locked	QAM256	519000000 Hz	-2.7 dBmV	42.7 dB	0	0
13	Locked	QAM256	525000000 Hz	-2.4 dBmV	42.9 dB	0	0
14	Locked	QAM256	531000000 Hz	-2.4 dBmV	43.1 dB	0	0
15	Locked	QAM256	537000000 Hz	-2.1 dBmV	43.1 dB	0	0
16	Locked	QAM256	543000000 Hz	-2.1 dBmV	43.1 dB	0	0
17	Locked	QAM256	549000000 Hz	-2.1 dBmV	43.0 dB	0	0
18	Locked	QAM256	555000000 Hz	-1.8 dBmV	43.1 dB	0	0
19	Locked	QAM256	561000000 Hz	-1.7 dBmV	43.1 dB	0	0
20	Locked	QAM256	567000000 Hz	-1.9 dBmV	43.1 dB	0	0
21	Locked	QAM256	573000000 Hz	-1.7 dBmV	43.3 dB	0	0
22	Locked	QAM256	579000000 Hz	-1.9 dBmV	42.9 dB	0	0
23	Locked	QAM256	585000000 Hz	-1.9 dBmV	42.9 dB	0	0
24	Locked	QAM256	591000000 Hz	-2.0 dBmV	42.6 dB	0	0
25	Locked	Other	693000000 Hz	-1.7 dBmV	41.0 dB	25416696	0
26	Not Locked	QAM256	0 Hz	0.0 dBmV	41.4 dB	0	0
27	Locked	QAM256	597000000 Hz	-1.9 dBmV	41.8 dB	0	0
28	Locked	QAM256	603000000 Hz	-1.7 dBmV	42.8 dB	0	0
29	Locked	QAM256	609000000 Hz	-2.0 dBmV	43.1 dB	0	0
30	Locked	QAM256	615000000 Hz	-1.9 dBmV	43.0 dB	0	0
31	Locked	QAM256	621000000 Hz	-2.0 dBmV	42.4 dB	0	0
32	Locked	QAM256	627000000 Hz	-1.9 dBmV	42.8 dB	0	0

Upstream Bonded Channels
Channel	Channel ID	Lock Status	US Channel Type	Frequency	Width	Power
1	2	Locked	SC-QAM Upstream	30100000 Hz	6400000 Hz	59.0 dBmV
2	1	Locked	SC-QAM Upstream	36500000 Hz	6400000 Hz	59.0 dBmV
3	3	Locked	SC-QAM Upstream	23700000 Hz	6400000 Hz	59.0 dBmV
4	4	Locked	SC-QAM Upstream	17300000 Hz	6400000 Hz	59.0 dBmV

Event Log
Date Time	Event ID	Event Level	Description
9/28/2020 9:24	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
9/28/2020 9:24	67061600	6	"DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
9/28/2020 9:24	2436694066	6	"Honoring MDD; IP provisioning mode = IPv6"
9/28/2020 9:23	82000500	3	"Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
9/28/2020 9:22	67061600	6	"DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
9/28/2020 9:22	2436694066	6	"Honoring MDD; IP provisioning mode = IPv6"
9/28/2020 9:22	84000100	3	"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
9/28/2020 9:21	82000500	3	"Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
9/28/2020 9:20	67061600	6	"DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
1/1/1970 0:00	2436694066	6	"Honoring MDD; IP provisioning mode = IPv6"
1/1/1970 0:00	84000100	3	"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
8/17/2020 14:27	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/17/2020 14:27	82000200	3	"No Ranging Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/17/2020 14:27	84000100	3	"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/17/2020 14:26	84000100	3	"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
1/1/1970 0:02	84000100	3	"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 16:11	82000500	3	"Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 16:11	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
1/1/1970 0:01	84000100	3	"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
1/1/1970 0:01	84000100	3	"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 16:05	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 16:04	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 16:03	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:55	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
1/1/1970 0:01	82000500	3	"Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
1/1/1970 0:00	82000200	3	"No Ranging Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
1/1/1970 0:00	84000100	3	"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:34	82000200	3	"No Ranging Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:33	84000100	3	"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:33	82000200	3	"No Ranging Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:33	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:33	84000100	3	"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:33	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:32	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:32	82000200	3	"No Ranging Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:31	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:31	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:30	84000100	3	"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:29	84000100	3	"SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:26	82000200	3	"No Ranging Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:26	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/16/2020 9:25	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/14/2020 20:35	82000500	3	"Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/13/2020 9:37	84000500	3	"SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/7/2020 1:36	82000500	3	"Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/6/2020 20:03	82000800	3	"16 consecutive T3 timeouts while trying to range on upstream channel 2;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/6/2020 20:03	82000600	3	"Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/6/2020 20:03	82000500	3	"Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/6/2020 19:16	82000500	3	"Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"
8/6/2020 19:15	82000800	3	"16 consecutive T3 timeouts while trying to range on upstream channel 2;CM-MAC=90:9d:7d:2e:a6:45;CMTS-MAC=00:01:5c:6b:7a:56;CM-QOS=1.1;CM-VER=3.1;"

EG · ‎09-28-2020

The upstream power is WAY OUT OF SPEC !!! That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.

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 it's best to Get the techs involved again until it is fixed properly.

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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SYNC Timing Synchronization failure

Re: SYNC Timing Synchronization failure