Internet keeps dropping out

[metalmatt]

For the last week my Internet has been dropping off for 30 seconds then it comes back on again. I have a hub 5 and keep getting 16 consecutive T3 timeouts plus US profile assignment change. I have had loads of these errors today. Can someone look onto this please? Thanks. 

[metalmatt]

Well I thought the issue was gone since the hub 5 reset however I got 16 consecutive T3 timeouts yesterday. My power levels are excellent, cables secured. I would say it's either the hub 5 that's the issue or a network issue. On a side note I didn't get this error on my hub 3.

[Sephiroth]

The T4 event that follows 16x T3s is not the result of a Hub fault unless it happens 100% of the time and the network itself is in good health.

The T3s occurred when you were not taking the stats and had you caught the events whilst taking stats, you would most probably have seen anomalies in the upstream such as QAM16 on one or more channels.  So, of your two choices, network issue (occasional) is more likely.

[metalmatt]

I had the following Yesterday at 6pm:

16 consecutive T3 timeouts while trying to range on upstream channel 2

QAM was not effected. all reading 64 on 3.0 upstream and 256 on 3.1. I'm going to put the hub in router mode for a week and see if I get any more T3 timeouts. Cheers.

[Sephiroth]

Just to say - the T3 timeouts are wholly independent of Router/Modem Mode.  The T3 events occur when the keep-alive data isn't received within the required period.  The mechanism is complex in that the upstream is sort of "invited" to send data along the shared resource (cable or fibre) according to opportunity (how busy the upstream is); the upstream is granted a mini-slot for each quantum of data (a number of symbols).  If the keep-alive data isn't received within the expected time, a T3 event occurs.  16x consecutively of those indicates an upstream issue, all within a very short space of time when you won't catch any QAM changes - which don't have to occur if there are other upstream issues.  HTH.

Router mode won't improve anything.

[Sephiroth]

Btw, if it's just one channel, then there is definitely an upstream issue.  Your data is split across all upstream channels and reassembled at the CMTS.  If just one channel is timing out then something's wrong - possible a laser issue, or noise.

[metalmatt]

Cheers for the info 🙂 Here are my current upstream stats:

3.0 Upstream channels
Channel Frequency (Hz) Power (dBmV) Symbol Rate (ksps) Modulation Channel ID
0 49600000 46 5120 QAM 64 1
1 43100000 45.8 5120 QAM 64 2
2 36600000 45.5 5120 QAM 64 3
3 30100000 45 5120 QAM 64 4
4 23600000 44.3 5120 QAM 64 9

3.0 Upstream channels
Channel Channel Type T1 Timeouts T2 Timeouts T3 Timeouts T4 Timeouts
0 ATDMA 0 1 4 0
1 ATDMA 0 1 6 0
2 ATDMA 0 1 0 0
3 ATDMA 0 1 42 0
4 ATDMA 0 1 1 0

3.1 Upstream channels
Channel Channel Width (MHz) Power (dBmV) FFT Type Modulation
10 10.4 41.5 2K QAM 256

3.1 Upstream channels
Channel Channel Type Number of Active Subcarriers First Active Subcarrier (Hz) T3 Timeouts T4 Timeouts
10 OFDMA 208 74000000 6 0

[metalmatt]

Here are my current downstream stats:

3.0 Downstream channels
Channel Frequency (Hz) Power (dBmV) SNR (dB) Modulation Channel ID
1 331000000 1.7 39 QAM 256 25
2 179000000 3.3 40 QAM 256 6
3 187000000 2.8 39 QAM 256 7
4 195000000 2.8 40 QAM 256 8
5 203000000 2.3 40 QAM 256 9
6 211000000 2.3 40 QAM 256 10
7 219000000 2 39 QAM 256 11
8 227000000 1.9 39 QAM 256 12
9 235000000 1.7 39 QAM 256 13
10 243000000 1.3 39 QAM 256 14
11 251000000 1 39 QAM 256 15
12 259000000 0.6 39 QAM 256 16
13 267000000 0.7 39 QAM 256 17
14 275000000 1.1 39 QAM 256 18
15 283000000 1.7 40 QAM 256 19
16 291000000 2.1 40 QAM 256 20
17 299000000 2.1 40 QAM 256 21
18 307000000 2.1 40 QAM 256 22
19 315000000 1.9 39 QAM 256 23
20 323000000 1.8 39 QAM 256 24
21 339000000 1.9 40 QAM 256 26
22 347000000 1.9 40 QAM 256 27
23 355000000 1.7 40 QAM 256 28
24 363000000 1.6 40 QAM 256 29
25 371000000 1.6 40 QAM 256 30
26 379000000 1.1 40 QAM 256 31
27 387000000 0.8 39 QAM 256 32
28 395000000 0.1 39 QAM 256 33
29 403000000 0 39 QAM 256 34
30 411000000 0.1 39 QAM 256 35
31 419000000 0 39 QAM 256 36

3.0 Downstream channels
Channel Locked Status RxMER (dB) Pre RS Errors Post RS Errors
1 Locked 39 127 23
2 Locked 40 137 116
3 Locked 39 122 0
4 Locked 40 105 20
5 Locked 40 99 0
6 Locked 40 104 10
7 Locked 39 111 60
8 Locked 39 116 67
9 Locked 39 90 11
10 Locked 39 97 0
11 Locked 39 111 9
12 Locked 39 135 12
13 Locked 39 162 23
14 Locked 39 126 77
15 Locked 40 108 78
16 Locked 40 102 71
17 Locked 40 123 72
18 Locked 40 107 13
19 Locked 39 122 118
20 Locked 39 128 115
21 Locked 40 166 67
22 Locked 40 136 65
23 Locked 40 142 13
24 Locked 40 152 11
25 Locked 40 153 122
26 Locked 40 175 20
27 Locked 39 127 0
28 Locked 39 233 67
29 Locked 39 226 0
30 Locked 39 249 12
31 Locked 39 221 0

3.1 Downstream channels
Channel Channel Width (MHz) FFT Type Number of Active Subcarriers Modulation (Active Profile) First Active Subcarrier (Hz)
37 94 4K 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)
37 Locked 37 -6.3 2079297869 104

[metalmatt]

Here is my log:

Time Priority Description
12-05-2024 20:17:34 critical Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
12-05-2024 18:00:51 critical Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
12-05-2024 18:00:51 critical 16 consecutive T3 timeouts while trying to range on upstream channel 2;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
12-05-2024 13:53:03 critical Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
11-05-2024 18:12:58 notice US profile assignment change. US Chan ID: 10; Previous Profile: 12 13; New Profile: 11 13.;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
11-05-2024 18:07:55 notice US profile assignment change. US Chan ID: 10; Previous Profile: 11 13; New Profile: 12 13.;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
11-05-2024 01:52:10 critical Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
10-05-2024 23:11:25 error DHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
10-05-2024 12:34:37 critical Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
10-05-2024 11:27:30 critical Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
10-05-2024 11:27:30 critical 16 consecutive T3 timeouts while trying to range on upstream channel 2;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
10-05-2024 04:03:20 critical Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
10-05-2024 00:43:51 critical No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
10-05-2024 00:43:27 critical No Ranging Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;
07-05-2024 13:09:02 critical Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=**:**:**:**:**:**;CMTS-MAC=**:**:**:**:**:**;CM-QOS=1.1;CM-VER=3.1;

[Sephiroth]

I take it that the downstream Uncorrectable errors are not rising.  Do please confirm.  What we're seeing now is most likely the result of the gibberish received while it's syncing after a reboot.  If the DS uncorrectables are rising, then that's a contributory factor because what the hub receives during ranging may be unintelligible.

I've noticed that the D3.1 downstream channel is at considerably lower power than the D3.0 channels and that the SNR (RxMER) is also poorer.  Something going on there perhaps.

Are your neighbours having a similar problem?  Worth reporting because an area fault gets their attention.

[metalmatt]

Its gone from 104 to 105. My next door neighbour has not reported anything. Its an error that's very random. The service does not go down just goes very slow for 25-30 seconds then back to normal only when I have 16 t3 timeouts in one go. I will turn off everything tomorrow and check connection and reboot.