SYNC Timing Synchronization failures

[karimkanji]

Hello,

We've been having intermittent connection problems with our Virgin Media broadband over the last few weeks. Before this, the connection was rock solid for a couple of years. 

We have a SH3 in modem mode connected to an Asus RT-AC68U router. The connection can be restored by powering off the SH3 for a good few minutes and then restarting it but the issue reappears any time between a couple of hours and a couple of days later.

I've checked the connections to the wall and the SH3 are all finger tight and the ASUS router and PC are hard-wired so it's not a Wifi problem.

Checking the Network logs, I noticed these errors at the time of the last disconnection (yesterday):

02/07/2021 16:04:32	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:32	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:31	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:31	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:30	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:29	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:27	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:27	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:25	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:25	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:23	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:23	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:22	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:22	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:21	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:21	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:19	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:19	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
02/07/2021 16:04:19	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;

[karimkanji]

and here is the rest of the info from the SH3:

Downstream bonded channels

Channel Frequency (Hz) Power (dBmV) SNR (dB) Modulation Channel ID

1	298750000	5.4	38	256 qam	21
2	138750000	5.5	40	256 qam	1
3	146750000	5.5	40	256 qam	2
4	154750000	5.5	40	256 qam	3
5	162750000	5.4	40	256 qam	4
6	170750000	5.4	40	256 qam	5
7	178750000	5.1	40	256 qam	6
8	186750000	5.3	38	256 qam	7
9	194750000	5.3	40	256 qam	8
10	202750000	5.1	40	256 qam	9
11	210750000	5.3	40	256 qam	10
12	218750000	5.3	40	256 qam	11
13	226750000	5.4	40	256 qam	12
14	234750000	5.4	40	256 qam	13
15	242750000	5	40	256 qam	14
16	250750000	5	40	256 qam	15
17	258750000	5.1	40	256 qam	16
18	266750000	5.5	40	256 qam	17
19	274750000	5.5	40	256 qam	18
20	282750000	5.5	40	256 qam	19
21	290750000	5.3	40	256 qam	20
22	306750000	5.4	40	256 qam	22
23	314750000	5.5	40	256 qam	23
24	322750000	5.8	40	256 qam	24

Downstream bonded channels

Channel Locked Status RxMER (dB) Pre RS Errors Post RS Errors

1	Locked	38.9	13	0
2	Locked	38.9	8	0
3	Locked	40.3	8	0
4	Locked	40.3	14	0
5	Locked	40.3	5	0
6	Locked	40.3	5	0
7	Locked	40.3	7	0
8	Locked	38.9	7	0
9	Locked	40.9	15	0
10	Locked	40.3	11	0
11	Locked	38.9	21	0
12	Locked	40.3	8	0
13	Locked	40.3	8	0
14	Locked	40.3	7	0
15	Locked	40.3	14	0
16	Locked	40.3	8	0
17	Locked	40.3	4	0
18	Locked	40.3	9	0
19	Locked	40.3	8	0
20	Locked	40.3	15	0
21	Locked	40.3	13	0
22	Locked	40.3	6	0
23	Locked	40.9	13	0
24	Locked	40.3	9	0

Upstream bonded channels

Channel Frequency (Hz) Power (dBmV) Symbol Rate (ksps) Modulation Channel ID

1	60300000	42	5120	64 qam	1
2	46200010	42.5	5120	64 qam	3
3	39400068	42.5	5120	64 qam	4
4	53700000	41.5	5120	32 qam	2

Upstream bonded channels

Channel Channel Type T1 Timeouts T2 Timeouts T3 Timeouts T4 Timeouts

1	ATDMA	0	0	0	0
2	ATDMA	0	0	1	0
3	ATDMA	0	0	0	0
4	ATDMA	0	0	0	0

and a link to the BQM I (only just) set up as requested in some of the other threads that I have read:

https://www.thinkbroadband.com/broadband/monitoring/quality/share/65a938ee5980a218e08cb30ba441eb9d4b2f06e7

 Would somebody be kind enough to have a look at this info and suggest steps to resolve the issues?

Thanks,

Karim

[jbrennand]

Hub stats look good. Logs are odd though - someone with more knowledge of logs needs to comment on them.

BQM only starting to build now will need 24h for a full picture. Meanwhile have you tried changing the ethernet cable from Hub to Asus to a new cat6 one ? I would also change your other ones just to be sure. A bad connection in one of the connectors could be the cause.

[karimkanji]

Thanks very much for taking the time to have a look John. I've switched out the cable between the hub and the router as you suggested, will see if that makes a difference.

[Zak_M]

Good afternoon @karimkanji 

Welcome back to the forums and thank you for taking the time to post. 

I am sorry to hear that you are having some issues with your services. 

I have taken a look over your account and there doesn't seem to be any issues of note, all the power levels are within spec.  I also checked the network and there is nothing there either, there is no utilisation work and no SNR issues. 

I would advise returning the hub into modem mode for 24 hours, monitor the BQM graph and see how we go from there. 

Kind regards,

Zak_M 

[karimkanji]

Hi Zak,

Thanks for taking a look. Unfortunately, having been ok all weekend, the connection has been up and down again today, starting i think just after your reply. Router logs below:

Downstream bonded channels

Channel Frequency (Hz) Power (dBmV) SNR (dB) Modulation Channel ID

1	298750000	5.4	38	256 qam	21
2	138750000	5.5	38	256 qam	1
3	146750000	5.5	38	256 qam	2
4	154750000	5.5	38	256 qam	3
5	162750000	5.3	40	256 qam	4
6	170750000	5.3	40	256 qam	5
7	178750000	5	38	256 qam	6
8	186750000	5.3	38	256 qam	7
9	194750000	5.1	40	256 qam	8
10	202750000	5	40	256 qam	9
11	210750000	5.1	38	256 qam	10
12	218750000	5.3	38	256 qam	11
13	226750000	5.3	38	256 qam	12
14	234750000	5.4	40	256 qam	13
15	242750000	5	38	256 qam	14
16	250750000	4.9	40	256 qam	15
17	258750000	5.1	38	256 qam	16
18	266750000	5.4	38	256 qam	17
19	274750000	5.4	40	256 qam	18
20	282750000	5.5	40	256 qam	19
21	290750000	5.1	38	256 qam	20
22	306750000	5.4	40	256 qam	22
23	314750000	5.5	40	256 qam	23
24	322750000	5.6	40	256 qam	24

Downstream bonded channels

Channel Locked Status RxMER (dB) Pre RS Errors Post RS Errors

1	Locked	38.6	4450	36735
2	Locked	38.9	4644	50043
3	Locked	38.9	4584	56404
4	Locked	38.9	4264	59344
5	Locked	40.3	4437	67802
6	Locked	40.3	4525	62940
7	Locked	38.9	4272	59932
8	Locked	38.9	3958	57398
9	Locked	40.3	4440	64604
10	Locked	40.3	4631	58810
11	Locked	38.9	4261	75552
12	Locked	38.9	4173	56964
13	Locked	38.9	4672	55395
14	Locked	40.3	4688	63544
15	Locked	38.6	4574	56955
16	Locked	40.3	4277	66579
17	Locked	38.9	1996	24192
18	Locked	38.9	4458	54141
19	Locked	40.3	4444	59898
20	Locked	40.3	4679	59498
21	Locked	38.9	4212	54707
22	Locked	40.3	4788	64047
23	Locked	40.3	4710	56076
24	Locked	40.3	3965	60339

Upstream bonded channels

Channel Frequency (Hz) Power (dBmV) Symbol Rate (ksps) Modulation Channel ID

1	60300000	42.3	5120	64 qam	1
2	46200108	42.5	5120	64 qam	3
3	39400076	42.5	5120	64 qam	4
4	53700000	42.5	5120	32 qam	2

Upstream bonded channels

Channel Channel Type T1 Timeouts T2 Timeouts T3 Timeouts T4 Timeouts

1	ATDMA	0	0	0	0
2	ATDMA	0	0	1	0
3	ATDMA	0	0	0	0
4	ATDMA	0	0	0	0

[karimkanji]

Network Log

Time Priority Description

05/07/2021 12:10:10	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:10:10	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:10:1	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:10:1	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:53	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:53	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:39	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:39	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:33	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:33	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:28	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:28	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:23	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:23	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:18	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:18	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:10	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:10	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:7	Warning!	RCS Partial Service;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;
05/07/2021 12:09:7	critical	SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.0;

and the BQM graph:

https://www.thinkbroadband.com/broadband/monitoring/quality/share/7104a1c80268b26cc64acc549baf2ac8f7869a11-05-07-2021

[lotharmat]

Yikes that is a lot of PostRS errors! - Looks like noise ingress somewhere in the circuit!

[jbrennand]

There have been a number of threads where the RS errors were due t the connection to the 3d party router.

First thing is to swap the ethernet cable (they do "fail") with a new and shielded Cat6 one. And see if clears it up.

If not - disconnect the Asus and use the Hub in router mode, reset the errors to 0 and check to see if the RS errors are still increasing over a few hours.

[karimkanji]

Thanks for the replies. I replaced the Cat 6 cable between SH3 and Asus router a couple of days ago after you suggested it initially but this doesn't seem to have made any difference.

Could the connection between the router and hub also cause the timing synchronisation errors that show up in the log?

Using the SH3 in router mode (instead of having the Asus do the routing) will be tricky especially because those errors only seem to show up when the connection fails which sometimes only happens every 2 or 3 days. The errors don't just tick up constantly. For example, when I checked last night (Sunday) there were still zero errors after I reset the hub on Friday lunchtime.