Periodic connection dropouts

[MattChapman]

Hi all,

I posted a while back when I had some problems with terrible packet loss, and while those problems were resolved by a Ziggo engineer at the wijkcabinet, I am now having issues with periodic connection drops.

Here is my connection log:

2021-06-15 12:56:31	notice	CM-STATUS message sent. Event Type Code: 5; Chan ID: 4 5 6 7 11 12 19 21 23 25 26 27 28 29 30 31 32 ; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 12:56:15	notice	CM-STATUS message sent. Event Type Code: 4; Chan ID: 29 30 31 32 ; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 12:56:02	warning	MDD message timeout;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 08:14:53	notice	DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3 .;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 08:14:17	notice	TLV-11 - unrecognized OID;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 08:14:15	error	Missing BP Configuration Setting TLV Type: 17.9;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 08:14:15	error	Missing BP Configuration Setting TLV Type: 17.8;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 08:14:15	error	Missing BP Configuration Setting TLV Type: 17.7;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 08:14:15	error	Missing BP Configuration Setting TLV Type: 17.6;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 08:14:15	error	Missing BP Configuration Setting TLV Type: 17.5;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 08:14:15	error	Missing BP Configuration Setting TLV Type: 17.4;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 08:14:15	error	Missing BP Configuration Setting TLV Type: 17.3;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 08:14:15	error	Missing BP Configuration Setting TLV Type: 17.2;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 08:14:15	error	Missing BP Configuration Setting TLV Type: 17.1;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
1970-01-01 00:00:30	warning	DHCP WARNING - Non-critical field invalid in response ;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
1970-01-01 00:00:28	notice	Honoring MDD; IP provisioning mode = IPv4
1970-01-01 00:00:21	critical	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:48:43	critical	No Ranging Response received - T3 time-out;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:48:19	critical	No Ranging Response received - T3 time-out;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:34:17	critical	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:34:13	critical	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:34:12	critical	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:34:11	critical	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:34:10	critical	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:34:10	critical	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:34:10	critical	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:34:09	critical	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:34:08	critical	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:34:08	critical	Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:33:56	critical	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:33:51	critical	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;
2021-06-15 01:33:47	critical	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=0c:b9:37:9a:32:bc;CMTS-MAC=00:17:10:93:e1:15;CM-QOS=1.1;CM-VER=3.1;

I see multiple sync failures, T3 & T4 timeouts and CM-STATUS messages 4 and 5 (Secondary Channel MDD Recovery and QAM/FEC Lock Recovery respectively). I also have seen messages like "CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW", but those (and others) get wiped on a modem power cycle.

Connection stats:

CM Downstream Channel Info

Channel	Lock Status	Channel Type	Channel ID	Frequency	Width	Power	SNR	Modulation Profile ID	Correctables	Uncorrectables
1	Locked	SC-QAM Downstream	3	618000000 Hz	8000000 Hz	11 dBmV	40.6 dB	QAM256	211	31
2	Locked	SC-QAM Downstream	1	602000000 Hz	8000000 Hz	12.4 dBmV	40.8 dB	QAM256	152	46
3	Locked	SC-QAM Downstream	2	610000000 Hz	8000000 Hz	12 dBmV	40.9 dB	QAM256	164	36
4	Locked	SC-QAM Downstream	4	626000000 Hz	8000000 Hz	10.6 dBmV	40.1 dB	QAM256	197	48
5	Locked	SC-QAM Downstream	5	634000000 Hz	8000000 Hz	10.4 dBmV	39.9 dB	QAM256	197	38
6	Locked	SC-QAM Downstream	6	642000000 Hz	8000000 Hz	10.6 dBmV	40 dB	QAM256	189	50
7	Locked	SC-QAM Downstream	7	650000000 Hz	8000000 Hz	10.8 dBmV	40 dB	QAM256	189	36
8	Locked	SC-QAM Downstream	8	658000000 Hz	8000000 Hz	11.4 dBmV	40.5 dB	QAM256	222	75
9	Locked	SC-QAM Downstream	9	666000000 Hz	8000000 Hz	12.1 dBmV	40.5 dB	QAM256	200	62
10	Locked	SC-QAM Downstream	10	674000000 Hz	8000000 Hz	12.4 dBmV	40.7 dB	QAM256	183	74
11	Locked	SC-QAM Downstream	11	682000000 Hz	8000000 Hz	12 dBmV	40.8 dB	QAM256	183	29
12	Locked	SC-QAM Downstream	12	690000000 Hz	8000000 Hz	12 dBmV	40.8 dB	QAM256	182	44
13	Locked	SC-QAM Downstream	13	698000000 Hz	8000000 Hz	12.4 dBmV	41 dB	QAM256	214	27
14	Locked	SC-QAM Downstream	14	706000000 Hz	8000000 Hz	12 dBmV	40.8 dB	QAM256	148	35
15	Locked	SC-QAM Downstream	15	714000000 Hz	8000000 Hz	11.5 dBmV	40.6 dB	QAM256	161	48
16	Locked	SC-QAM Downstream	16	722000000 Hz	8000000 Hz	11.4 dBmV	40.6 dB	QAM256	211	33
17	Locked	SC-QAM Downstream	17	730000000 Hz	8000000 Hz	11.4 dBmV	40.4 dB	QAM256	220	49
18	Locked	SC-QAM Downstream	18	738000000 Hz	8000000 Hz	11.3 dBmV	40 dB	QAM256	278	27
19	Locked	SC-QAM Downstream	19	746000000 Hz	8000000 Hz	11.4 dBmV	40.1 dB	QAM256	242	23
20	Locked	SC-QAM Downstream	20	754000000 Hz	8000000 Hz	11.2 dBmV	40 dB	QAM256	252	59
21	Locked	SC-QAM Downstream	21	762000000 Hz	8000000 Hz	11 dBmV	40.1 dB	QAM256	245	32
22	Locked	SC-QAM Downstream	22	770000000 Hz	8000000 Hz	10.5 dBmV	40.1 dB	QAM256	254	84
23	Locked	SC-QAM Downstream	23	778000000 Hz	8000000 Hz	10.4 dBmV	40.1 dB	QAM256	230	64
24	Locked	SC-QAM Downstream	24	786000000 Hz	8000000 Hz	10.6 dBmV	40 dB	QAM256	255	71
25	Locked	SC-QAM Downstream	25	794000000 Hz	8000000 Hz	10.2 dBmV	39.8 dB	QAM256	266	48
26	Locked	SC-QAM Downstream	26	802000000 Hz	8000000 Hz	10.3 dBmV	39.9 dB	QAM256	271	35
27	Locked	SC-QAM Downstream	27	810000000 Hz	8000000 Hz	10.5 dBmV	39.9 dB	QAM256	283	58
28	Locked	SC-QAM Downstream	28	818000000 Hz	8000000 Hz	10.3 dBmV	39.9 dB	QAM256	276	62
29	Locked	SC-QAM Downstream	29	826000000 Hz	8000000 Hz	9.5 dBmV	39.7 dB	QAM256	295	58
30	Locked	SC-QAM Downstream	30	834000000 Hz	8000000 Hz	8.8 dBmV	39.3 dB	QAM256	307	44
31	Locked	SC-QAM Downstream	31	842000000 Hz	8000000 Hz	8.4 dBmV	39 dB	QAM256	323	59
32	Locked	SC-QAM Downstream	32	850000000 Hz	8000000 Hz	8.4 dBmV	38.9 dB	QAM256	350	63
33	Locked	OFDM Downstream	33	883000000 Hz	93000 kHz	7.6 dBmV	38.1 dB	OFDM PLC	3440	0

CM Upstream Channel Info

Channel	Lock Status	Channel Type	Channel ID	Frequency	Width	Power	Modulation/Profile ID
1	Locked	ATDMA	1	58800000 Hz	6400000 Hz	41 dBmV	2
2	Locked	ATDMA	2	52000000 Hz	6400000 Hz	41 dBmV	2
3	Locked	ATDMA	3	45200000 Hz	6400000 Hz	41 dBmV	2
4	Locked	ATDMA	4	38400000 Hz	6400000 Hz	41 dBmV	2
5	Locked	ATDMA	5	33200000 Hz	3200000 Hz	40 dBmV	2
6	Locked	ATDMA	6	30000000 Hz	3200000 Hz	40 dBmV	2

Error numbers are fairly low, but this is after an uptime of only 5 hours. My understanding is that uncorrectable errors should be 0 across the board, and correctable errors are of no concern.

I have tried:

• Rebooting modem
• Replacing coax cable
• Removing splitter

All to no effect - it looks to me like I am having interference issues again.

Any help would be appreciated! Thanks in advance 🙂

[tobiastheebe]

Downstream power levels are quite high, perhaps due to the splitter being removed. The log indicates noise/stability issues in both downstream and upstream, which could be partially related to the uncorrectable errors. Correctable errors and T3 timeouts are acceptable to some extent. Looking at the (un)correctable errors, none of the channels stand out in particular, therefore I don't suspect an interference issue at this time.

Could you post one or more pictures of AOP (main socket inside utility closet ('meterkast') or in living room) and cables, plus splitter(s) and signal amplifier, as applicable?

[Mariska]

Hi @MattChapman, 

I'm sorry you're experiencing problems again! Luckily we're here to help. It would be great if you can post the pictures that tobiastheebe asked for so we can hopefully see what's causing the problems. Thanks in advance 🙂 

[MattChapman]

Hi @tobiastheebe and @Mariska , thanks for responding!

Photo of the AOP:

 

the cable connects directly into the Ubee modem:

No extra splitters or amplifiers involved, which keeps things nice and simple.

The AOP has been replaced twice - once by a Ziggo engineer, and then a second time by an engineer from BAM when the previous problem was suspected to be cable damage outside the property.

I'm not sure why the photos uploaded sideways, but oh well 😁  Cheers!

[tobiastheebe · Accepted solution]

The current AOP (X10DER) is a special one for cases where the green CAI cable is very short and does not allow for connecting a 'regular' AOP.

The splitter (which is only being used as a 4 dB attenuator here) makes the modem vulnerable to external noise and interference due to the unterminated output. You should replace the splitter with a dedicated attenuator, 6 dB should be good. This attenuator can be screwed onto the modem's coax connector directly.

[MattChapman]

Hi @tobiastheebe , the AOP makes sense - the green cable comes up the side of my apartment building in some conduit, and then comes straight through my wall and into the connector which is now there. My understanding from the Ziggo and BAM engineers that have been in the past is that there is essentially no slack for them to use. I would love for them to pull a new length of cable, but I get that it isn't the most practical option!

I didn't consider that the splitter could pick up interference - I'll for sure pick up an attenuator, from your link it seems they are only a couple of euros.

I'll report back once I try that out - I appreciate the advice!

[tobiastheebe]

Correct, no cable slack is very frustrating for technicians installing/replacing an AOP. When a new cable is pulled into a property, approximately 1 meter of service loop should be left to allow for retrofitting, this is however a 100% ideal situation that often does not exist. Installing an AOP like yours, with a special connector that 'bites' through the cable, is the best solution for a 'no-slack' situation.

I am using a 3 dB attenuator myself, my current + average DS/US power levels are 5/43 dBmV, compared to 8/41 dBmV on my previous modem (without the attenuator installed).

Do let me know if you have any further questions.

[MattChapman]

Hi @tobiastheebe , AlleKabels finally delivered my attenuator, and I fitted it yesterday afternoon. As a result my modem stats are much better. DS/US averages 7/43 dBmV.

I also received a firmware update when I rebooted the modem after installing the attenuator, so that could have reasonably had an effect too.

I have a constant stream of correctable errors on the OFDM channel 33, but from what I have read online, lots of correctable errors on an OFDM channel is quite normal. Either way, I'm happy to see I have no uncorrectables after 24 hours of uptime!

So I have learned:

• When dealing with DOCSIS there is such a thing as having too much signal.
• When dealing with cable connections, an unterminated output (like on a splitter) can cause more noise, and therefore connection dropouts.

Thanks very much for your advice!

[tobiastheebe]

Glad to read that the modem's power levels and uncorrectable errors have much improved after installing the attenuator.

Correctable errors on the OFDM channel are acceptable, since this channel is much wider than the SC-QAM channels and therefore much more susceptible to noise. As long as the uncorrectable errors remain 0, the correctable errors should have no noticeable impact on the internet connection's stability and speed.