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Huskion
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Intermittent connectivity and packet loss

For about 5 days now, I have been experiencing intermittent packet loss. Asking for support on Twitter and calling up doesn't seem to have helped - had an engineer come to the cabinet and got a text saying the issue was resolved, but it wasn't. The agent on the phone said there was a "high SNR on the fibre portion" of the connection, which didn't really make sense to me, because signal-to-noise ratio isn't something you can get on fibre optics, as far as I'm aware, and I believed the fault to be related to the DOCSIS (co-axial cable) portion of my connection between the street cabinet and my home.

stats.jpg

Displayed are the past 24 hours of ping statistics measured remotely (from thinkbroadband.com to my router), as well as statistics on the 8th, 9th and 12th of March (the weekend 10th-11th was okay). This means this is measuring my SH3's actual connectivity to the internet, not anything from any machine on my internal network.

The latency reports show as normal but between my installation last August up until 5 days ago, there were never any red marks from the top down (packet loss, disconnections). A total loss of service occurs for a whole minute when the red hits the bottom part of the graph, but even then, 20% loss occurring frequently is still very noticeable and frustrating, and any use of the service checker / diagnostics yields no detected fault.

I doubt it's the fault of the hub, because it's worked quite happily for months and months without a flaw or any of the other hiccups other customers have experienced. It's going to be something with the connectivity. I'm 20 metres from the street cabinet, I can see it through the front window of the house, so I have no idea what's going on between that and my router, but I'd like it fixed.

Here are the stats from the SH3's logs (with the MAC addresses removed for security). Aside this and the image above, I have no way to tell what's really wrong.

Cable Modem StatusItem Status Comments

Acquired Downstream Channel(Hz)
267000000
Locked
Ranged Upstream Channel(Hz)
53700000
Locked
Provisioning State
Online

 

Downstream bonded channelsChannel Frequency(Hz) Power(dBmV) SNR(dB) Modulation Channel ID

126700000014.340.9256 qam9
232300000013.940.9256 qam16
331500000013.940.3256 qam15
43070000001440.3256 qam14
529900000014.340.3256 qam13
62910000001440.3256 qam12
72830000001440.3256 qam11
82750000001440.3256 qam10
925900000014.440.3256 qam8
1025100000014.440.9256 qam7
1124300000014.540.9256 qam6
1223500000014.640.9256 qam5
1322700000014.840.3256 qam4
1421900000014.940.9256 qam3
152110000001540.9256 qam2
1620300000015.340.9256 qam1

 

Upstream bonded channelsChannel ID Frequency(Hz) Mode Power(dBmV) Modulation Channel Bandwidth(Hz) Symbol Rate (ksps)

553700000ATDMA31.864 qam64000005120
425800000ATDMA31.864 qam64000005120

 

Operational ConfigurationGeneral Configuration Value

Network access
Enabled
Maximum Number of CPEs
1
Baseline Privacy
Enabled
Docsis Mode
Docsis30
Config file
(redacted)
Primary Downstream Service Flow
SFID890
Max Traffic Rate230100000
Primary Upstream Service Flow
SFID889
Max Traffic Rate22000000

 

Network LogDate And Time Error Number Event Description

2018-03-12 03:32:27.0068010600DHCP Renew - lease parameters tftp file-V42997a858765887c.cm modified;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-12 10:05:21.0084000700RCS Partial Service;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-12 10:05:28.0084000500SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-12 10:05:28.0084000700RCS Partial Service;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-12 10:05:28.0084000500SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-12 10:05:34.0084020200Lost MDD Timeout;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-12 10:06:04.0082000400Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-12 11:05:29.0084020100Missing Mandatory MDD TLV on primary DS Channel;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-12 11:47:47.0068010100DHCP RENEW sent - No response for IPv4;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-12 11:59:05.0068010400DHCP REBIND WARNING - Field invalid in response;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-12 11:59:05.0068010600DHCP Renew - lease parameters tftp file-V42997a858765887c.cm modified;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-13 00:03:10.0082000200No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-13 14:04:40.0082000400Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-13 14:05:26.0082000200No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-13 14:06:42.0082000900B-INIT-RNG Failure - Retries exceeded;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-13 14:06:44.0082000200No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-13 14:07:44.0084000500SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-13 14:07:50.0084020200Lost MDD Timeout;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-13 14:07:54.0082000100No Maintenance Broadcasts for Ranging opportunities received - T2 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;
2018-03-13 14:09:10.0082000200No Ranging Response received - T3 time-out;CM-MAC=;CMTS-MAC=;CM-QOS=1.1;CM-VER=3.0;

 

I'm stumped. I hope someone out there can see something I can't and can help fix this.

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Superuser
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Re: Intermittent connectivity and packet loss

Your Downstream power levels are too high and out of spec, the Upstream power levels are a bit low which is normally OK due to the proximity of the cab, if  stable, but can cause issues if there is noise on the connection, which the logs are suggesting there is. The logs and BQM graph are showing your connection dropping

You will need to contact VM for resolution, either by waiting here about a week until a VM Forum Team Member picks up the thread, or give them a call on 150 from a VM line or 0345 454 1111 for a quicker response.

 

 

 

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Huskion
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Re: Intermittent connectivity and packet loss

I've called through - with the customer services agent, I performed another factory reset of the SH3 and after it started up, it wasn't locking onto the frequency it had been set to. The agent changed the frequency it locks onto and advised that I have engineers working in the area for the next 3 hours or so.

I was also advised that if by this evening there are ongoing issues that last longer than 5-10 mins at a time, to contact again.

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Huskion
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Re: Intermittent connectivity and packet loss

A week later, problems ongoing, an engineer visited in order to fix the fault.

They immediately noticed the power of the coax cable was far too high and sought to reduce it by going to the street cabinet but couldn't find my line there after 40 minutes of looking.

I was made aware that appointments are targeted to last 36 minutes on average but that a Virgin Media engineer cannot leave unless service is restored.

After adding a 10dBmV attenuator to the end of my line instead, the power was reduced, but because my SH3 had been slowly cooking for 9 months, the packet loss issue still occurred.

The engineer replaced the SH3 with a spare that he had, and was then on his way after sticking around 90 mins - and the issue appeared to have gone but was back within an hour.

After calling yet again, I was informed that there was a local incident that was affecting many customers and that the predicted resolution target date was the 28th. The only other new piece of information I got about my issue is that a traceroute started noticing a lack of response from the first hop beyond my router, and so the issue is likely with the CMTS.

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Forum Team
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Re: Intermittent connectivity and packet loss

Hello Huskion

Apologies for the poor connection, it would look to have been down to an area upstream noise issue F006100229 which was resolved yesterday. At the moment your hub and line levels are in spec so fingers crossed it has improved.

Thank you

Nicola

Virgin Media Forum Team
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