Hi,At very random times I lose service for a few minutes. This doesnt happen everyday or every week, it happens very randomly. Looking at the hub 5 logs I see this message "16 consecutive T3 timeouts while trying to range on upstream channel 8". Looking closer it seems to be related to the docsis 3.1 upstream channel. For some unknown reason a large number of timeouts occur which takes the internet down for a few minutes. Ive been on the phone with CS who dont really have an idea of what I was talking about. I would like to know what causes these consecutive T3 timeouts and if anyone else with a hub 5 has similar issues?Reboots and factory resets dont work. Ive already had a few hub 5's and new cables, the issue still occurs. Neighbours that I talk to have hub 3's and they dont get these interruptions when I get mine and Im assuming this is because they're using docsis 3.0 channels?Any advise would be appreciated.Thanks

Imo, Martin should have said that there is noise on your upstream (which you at least have grasped) and as you neighbour has a similar symptom, there is likely to be an area fault. A repeated fault needs attention.The problem in getting this noise resolved is that the shifting QAM modulation is standard behaviour because the level is set to take noise into account. The Forum Team are thus not interested in changes of QAM modulation.Of course a more significant noise ingress can cause an upstream channel to fail. In your case, the keep-alive message on your then broken upstream channel failed 16x times and there would have bee a T4 event - modem reset.All that the Community can do is interpret what's going on. You really are in VM's hands here and until they recognise that your T4 events are a serious matter and that it affects neighbours, you're lumbered with the problem.

A little update for those watching this thread:So after raising a complaint I got a call back from the complaints team. I explained the issues and the representative raised it with the local networks team. I saw a networks engineer down my road on Thursday and I wanted to have a chat with him but he was busy on the phone. I then got a phone call on Friday morning, the complaints team called as they just received an email from the networks team with their findings. They found an issue with the power levels at the cab, which they have adjusted and bought in spec. So far, the modulation on the upstream channels have stayed at 64qam, even on the weekends (where previously they were dipping). So far I haven't had any "16 consecutive t3 timeouts" but its too early to tell. Ill be monitoring the connection for the next week or 2. Hoping its all fixed (fingers crossed).I did have a bit of packet loss (to virgin media's gateway) on Friday evening, Saturday evening and Sunday afternoon. These were very small but they have started to appear. Again Ill be keeping an eye and Ill update the complaints team when they call me in a weeks time.Thanks to all that have helped on this thread with advice and knowledge, really appreciate it.

All of the upstream power levels are half of what they should be. The BQM suggests some local congregation perhaps. I'd report it as a fault after checking for local faults on 0800 561 0061.

Each case is unique unless you are on the same network segment as someone else with the same issue.The Community here can help you pin this down if you post your upstream/downstream stats and the network log. If there is a line impairment, for whatever reason, you're well likely to get 16x T3 events followed by a Hub reset.The Hub 4 is orders of magnitude better than the Hub 3. Btw, the Forum Team , when they come to look at your circuit, are unlikely to find anything wrong unless they catch it at the right moment. These are difficult cases.

Another update:I had a networks engineer and normal engineer attend today. They finally looked at the correct cabinet and found some issues. As previous engineers stated, the cabinet was in a mess and the cable coming into the cab was damaged.The network engineer repaired the damaged cable coming into the cabinet, also repaired a few other cables within the cab and lastly found a splitter that was not working correctly. There was around an hour downtime this morning whilst he was working on the cab and after that all my power levels shot up to over 10. The engineer came back and added a different anntenuator on the coax cable to reduce the power. So now I will continue to monitor. Fingers crossed I hope everything's fixed. (after years of complaining about noise)

16 Consecutive T3 Timeouts Causing Internet Blips | Virgin Media Community

101 Replies

avi68

Superfast

6 months ago

3.0 Downstream channels

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

1	299000000	6.8	40	QAM 256	21
2	139000000	8.5	40	QAM 256	1
3	147000000	8.5	40	QAM 256	2
4	155000000	8.3	39	QAM 256	3
5	163000000	8.1	39	QAM 256	4
6	171000000	7.9	39	QAM 256	5
7	179000000	7.8	39	QAM 256	6
8	187000000	7.7	39	QAM 256	7
9	195000000	7.8	39	QAM 256	8
10	203000000	7.6	39	QAM 256	9
11	211000000	7.7	39	QAM 256	10
12	219000000	7.6	38	QAM 256	11
13	227000000	7.5	38	QAM 256	12
14	235000000	7.5	38	QAM 256	13
15	243000000	7.3	38	QAM 256	14
16	251000000	7	39	QAM 256	15
17	259000000	6.8	39	QAM 256	16
18	267000000	6.8	39	QAM 256	17
19	275000000	6.8	39	QAM 256	18
20	283000000	6.7	39	QAM 256	19
21	291000000	6.7	40	QAM 256	20
22	307000000	7.1	40	QAM 256	22
23	315000000	7.1	40	QAM 256	23
24	323000000	7.2	40	QAM 256	24
25	331000000	6.9	41	QAM 256	25
26	339000000	6.9	41	QAM 256	26
27	515000000	6.2	41	QAM 256	36
28	523000000	6.2	42	QAM 256	37
29	531000000	6.1	42	QAM 256	38
30	539000000	6.1	42	QAM 256	39
31	547000000	6.1	42	QAM 256	40

3.0 Downstream channels

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

1	Locked	40	187	0
2	Locked	40	110	0
3	Locked	40	101	0
4	Locked	39	110	0
5	Locked	39	103	0
6	Locked	39	98	0
7	Locked	39	124	0
8	Locked	39	118	0
9	Locked	39	134	0
10	Locked	39	126	1
11	Locked	39	138	0
12	Locked	38	203	0
13	Locked	38	188	0
14	Locked	38	203	0
15	Locked	38	181	0
16	Locked	39	186	4
17	Locked	39	171	0
18	Locked	39	157	0
19	Locked	39	161	0
20	Locked	39	169	0
21	Locked	40	185	0
22	Locked	40	187	0
23	Locked	40	222	0
24	Locked	40	279	1
25	Locked	41	216	0
26	Locked	41	282	2
27	Locked	41	344	0
28	Locked	42	298	0
29	Locked	42	330	0
30	Locked	42	359	0
31	Locked	42	354	0

3.1 Downstream channels

Channel Channel Width (MHz) FFT Type Number of Active Subcarriers Modulation (Active Profile) First Active Subcarrier (Hz)

1840

QAM 4096

1108

3.1 Downstream channels

Channel ID Locked Status RxMER Data (dB) PLC Power (dBmV) Corrected errors (Active Profile) Uncorrectable errors (Active Profile)

Locked

5.9

850381515

avi68
Superfast
6 months ago
3.0 Upstream channels
Channel Frequency (Hz) Power (dBmV) Symbol Rate (ksps) Modulation Channel ID
0 49600000 45.5 5120 QAM 64 1
1 43100000 45.3 5120 QAM 64 2
2 36600000 45.3 5120 QAM 64 3
3 30100000 45 5120 QAM 64 4
4 23600000 44.8 5120 QAM 64 5
3.0 Upstream channels
Channel Channel Type T1 Timeouts T2 Timeouts T3 Timeouts T4 Timeouts
0 ATDMA 0 0 0 0
1 ATDMA 0 0 2 0
2 ATDMA 0 0 0 0
3 ATDMA 0 0 0 0
4 ATDMA 0 0 0 0
3.1 Upstream channels
Channel Channel Width (MHz) Power (dBmV) FFT Type Modulation
6 10.4 40.5 2K QAM 256
3.1 Upstream channels
Channel Channel Type Number of Active Subcarriers First Active Subcarrier (Hz) T3 Timeouts T4 Timeouts
6 OFDMA 208 74000000 36 0

avi68

Superfast

6 months ago

Network Log

Time	Priority	Description
11-01-2025 12:34:40	critical	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 18:44:01	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 18:38:57	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 16:54:36	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 16:49:33	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 16:12:02	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 16:06:59	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 15:43:55	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 15:38:52	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 09:04:02	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 08:58:59	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 07:45:07	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 07:34:22	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 07:08:21	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 07:03:18	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 02:25:50	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
10-01-2025 02:20:47	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 23:35:55	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 23:30:52	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 22:21:02	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 22:15:59	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 22:02:49	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 21:57:46	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 21:55:28	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 21:50:25	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 21:12:36	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 21:07:33	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 21:04:35	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 20:59:32	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 20:33:31	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 20:28:28	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
09-01-2025 19:19:27	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;

Sephiroth
Alessandro Volta
5 months ago
The profile changes on the upstream are the clue to what's going on. The higher the two numbers, the poorer the upstream signal. The IUC value 13 is the fallback value (likely to be 16QAM) and is the value used for initialisation. The value 11 or 12 (going down to 9) is the higher modulation in data traffic. I don't know the VM configured settings but I surmise:
12 = 32QAM; 11 = 64QAM; 10 = 128QAM; 9 = 256QAM.
The CMTS performs the signal quality check periodically at the upstream line card, looking at your stats that seems to be a 5 minute period. The IUC change affects everyone in your segment who is on the same upstream channels (which might not be everyone).
Everything we can se in the logs, networks can see on the CMTS event logs and, I suspect, will receive alarms if the events occurrence exceeds a threshold (that I don't know).
So yes, the network log shows the upstream struggling at various times.
- avi68
  Superfast
  5 months ago
  This is really good to know. Ive always seen the profile changes spam my logs but had no idea what it meant. Thanks for the explanation.
  
  Now trying to get someone to look at the struggling upstream is another hurdle in itself.

avi68

Superfast

5 months ago

Rebooted Hub yesterday and the internet stopped today with the 16 timeouts.

Network Log

Time	Priority	Description
13-01-2025 14:48:50	critical	Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
13-01-2025 14:48:50	critical	16 consecutive T3 timeouts while trying to range on upstream channel 8;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
13-01-2025 14:47:42	critical	Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
13-01-2025 12:39:41	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
13-01-2025 12:29:35	notice	US profile assignment change. US Chan ID: 6; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
12-01-2025 16:24:00	notice	REGISTRATION COMPLETE - Waiting for Operational status
12-01-2025 16:23:55	warning	RNG-RSP CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
12-01-2025 16:23:48	notice	DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
12-01-2025 16:23:44	notice	TLV-11 - unrecognized OID;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
12-01-2025 16:23:42	warning	DHCP WARNING - Non-critical field invalid in response ;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
12-01-2025 16:23:40	notice	Honoring MDD; IP provisioning mode = IPv4
12-01-2025 16:23:37	critical	No Ranging Response received - T3 time-out;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
12-01-2025 16:23:30	critical	SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=-;CMTS-MAC=:::::;CM-QOS=1.1;CM-VER=3.1;
12-01-2025 16:23:29	critical	Cable Modem Reboot because of - Reboot UI

Nathan_B
Forum Team
5 months ago
Hi there avi68 👋 Welcome back to our forum and thanks for your post 😊

Sorry to see you're still seeing these drop outs. I've checked our system and can see that your Hub power levels are out of spec. This isn't something that can be fixed remotely so you will need an engineer to have this fixed.

I'll pop you a PM to confirm some details so this can be arranged.

Regards

Nathan
- avi68
  Superfast
  5 months ago
  I had an engineer attend on the 16th. He said that all my levels were within spec. Could you point out which levels you are referring to ? Downstream or upstream?
  Also had another blip today at 15:37. Again, network log shows 16 consecutive T3 timeouts

Sephiroth
Alessandro Volta
5 months ago
Those levels are fine. It's when the blackout occurs that matter. You should still be able to access the hub during the outage. If it's still the upstream profile changes in the network log, then it's what I described in an earlier post. Issues in the upstream.
- avi68
  Superfast
  5 months ago
  So when it happened today (as it was blacking out), I accessed the hub 5 but I could not see any issues with any of the levels on the upstream. I kept refreshing and then it finally showed the timeouts in the logs. This time I didnt see any upstream profile changes.
  
  Engineer attended on Thursday, could not see any issues with levels, we then reset the hub and since Thursday I havnt had any upstream profile changes.
avi68
Superfast
5 months ago
@sephiroth
Here is the hub 5 network log: (sorry about the formatting, the new forum wont let me paste as a table)
Network Log
Time      Priority Description
19-01-2025 15:38:56     critical   Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
19-01-2025 15:38:56     critical   16 consecutive T3 timeouts while trying to range on upstream channel 8;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
19-01-2025 15:37:48     critical   Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
19-01-2025 04:41:43     error      DHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
16-01-2025 11:02:44     notice    REGISTRATION COMPLETE - Waiting for Operational status
16-01-2025 11:02:39     warning                RNG-RSP CCAP Commanded Power in Excess of 6 dB Below the Value Corresponding to the Top of the DRW;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
16-01-2025 11:02:32     notice    DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
16-01-2025 11:02:29     notice    TLV-11 - unrecognized OID;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
16-01-2025 11:02:26     warning                DHCP WARNING - Non-critical field invalid in response ;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
16-01-2025 11:02:24     notice    Honoring MDD; IP provisioning mode = IPv4
16-01-2025 11:02:21     critical   No Ranging Response received - T3 time-out;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
16-01-2025 11:02:15     critical   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=-;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
16-01-2025 11:02:14     critical   Cable Modem Reboot because of - Erouter Mode Change
16-01-2025 10:28:15     critical   No Ranging Response received - T3 time-out;CM-MAC=-;CMTS-MAC=-;CM-QOS=1.1;CM-VER=3.1;
16-01-2025 10:28:10     critical   SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=-;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
16-01-2025 10:28:09     critical   Cable Modem Reboot because of - pin-reset
- Sephiroth
  Alessandro Volta
  5 months ago
  That looks like the Docsis 3.1 downstream giving problems. There may have been a largeish # of uncorrectables, but I couldn't distinguish the number from the rubbish formatting that those fools have enforced.
  - avi68
    Superfast
    5 months ago
    3.1 downstream is clean:

Forum Discussion

16 Consecutive T3 Timeouts Causing Internet Blips

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16 consecutive T3 timeouts outages and Code 16/24

0	49600000	45.5	5120	QAM 64	1
1	43100000	45.3	5120	QAM 64	2
2	36600000	45.3	5120	QAM 64	3
3	30100000	45	5120	QAM 64	4
4	23600000	44.8	5120	QAM 64	5

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