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Unstable/Intermittent Docsis Connection

Hi All,

I'm posting on here as I seem to be getting nowhere fast with this current fault.

I'm currently helping my parents troubleshoot their Virgin Media broadband connection. They are not very tech savvy and have had a pretty solid connection for the last 10 or so years, until recently.

The past few weeks the broadband connection has been dropping multiple times a day (more so at night), and also the Virgin set top boxes have been outputting very choppy/pixelated video albeit intermittently as well.

For reference, the setup is as follows in the house:
Incoming coax from street => RG6 coupler => Cable run to the side of the house => 3 way splitter => This goes to three locations:
1) Living room set top box
2) Kitchen (nothing is connected here)
3) Upstairs bedroom

From the upstairs bedroom, the cable goes into a 2 way splitter, one feeds to STB in that room, the other goes to the broadband modem.

There are no forward path attenuators, equalisers or simulators connected anywhere.

When the broadband connection drops, we seem to lose all upstream docsis channels and the logs are filled with "No Ranging Response received - T3 time-out" and "B-INIT-RNG Failure - Retries exceeded" errors.

So far we've had 3 engineer visits from VM engineers, which did the following;

Engineer 1: Came and replaced the set top box in the living room, checked all other connections around the property, said everything looked fine.

Engineer 2: Replaced the 3 way splitter outside the property, again checked all other connections around the property, said everything looked fine.

Engineer 3: Came and replaced our aging super hub 2 with a super hub 3 (really thankful for him doing this), replaced the set top box in the upstairs bedroom, rechecked all other connections and by the sounds of it went to the street cab to check and everything was fine.

It took me a good while before the person I spoke to in VM's support team to actually send engineer 3, as they basically told us to reboot the modem and call back if it happens again, which at this point was unacceptable.

After engineer 3's visit, I also noticed that whenever one of the set top boxes is powered on, that seems to cause the broadband connection to drop within a few minutes of it coming online.

Also I'm not sure what's different about today but the broadband connection has been down since about 2pm, rather than being intermittent.

Basically this is what the stats on the super hub 3 look like when the outage occurs:

Downstream bonded channels
Channel	Frequency (Hz)	Power (dBmV)	SNR (dB)	Modulation	Channel ID
1	283000000	-8.5	37	256 qam	19

Downstream bonded channels
Channel	Locked Status	RxMER (dB)	Pre RS Errors	Post RS Errors
1	Locked	37.6	12	0

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

Upstream bonded channels
Channel	Channel Type	T1 Timeouts	T2 Timeouts	T3 Timeouts	T4 Timeouts


When the connection is working it looks like this:

Channel	Frequency (Hz)	Power (dBmV)	SNR (dB)	Modulation	Channel ID
1	307000000	-0.5	38	256 qam	22
2	139000000	4.4	38	256 qam	1
3	147000000	3.7	40	256 qam	2
4	155000000	3.5	37	256 qam	3
5	163000000	1.9	38	256 qam	4
6	171000000	2.2	40	256 qam	5
7	179000000	2.2	40	256 qam	6
8	187000000	2	40	256 qam	7
9	195000000	2.2	40	256 qam	8
10	203000000	1.7	40	256 qam	9
11	211000000	1.4	40	256 qam	10
12	219000000	1.5	40	256 qam	11
13	227000000	1	40	256 qam	12
14	235000000	0.7	40	256 qam	13
15	243000000	0.4	40	256 qam	14
16	251000000	0	40	256 qam	15
17	259000000	0.5	40	256 qam	16
18	267000000	0	40	256 qam	17
19	275000000	0	40	256 qam	18
20	283000000	0.2	40	256 qam	19
21	291000000	-0.5	38	256 qam	20
22	299000000	-0.2	40	256 qam	21
23	315000000	-0.2	40	256 qam	23
24	323000000	-0.5	40	256 qam	24

Downstream bonded channels
Channel	Locked Status	RxMER (dB)	Pre RS Errors	Post RS Errors
1	Locked	38.9	104856	16837
2	Locked	38.9	112297	110543
3	Locked	40.3	92791	61870
4	Locked	37.3	62729664	55895
5	Locked	38.6	94092	53977
6	Locked	40.9	95765	50191
7	Locked	40.3	97550	45076
8	Locked	40.9	98402	43703
9	Locked	40.9	100085	40429
10	Locked	40.9	101079	37950
11	Locked	40.9	101087	38264
12	Locked	40.3	104385	30357
13	Locked	40.9	104651	28769
14	Locked	40.9	105525	26674
15	Locked	40.3	105007	25330
16	Locked	40.9	103295	28735
17	Locked	40.9	104351	22876
18	Locked	40.3	104884	23165
19	Locked	40.3	104990	21487
20	Locked	40.3	106030	17289
21	Locked	38.9	106238	19087
22	Locked	40.3	105436	18007
23	Locked	40.3	103854	16679
24	Locked	40.3	101031	12712

Channel	Frequency (Hz)	Power (dBmV)	Symbol Rate (ksps)	Modulation	Channel ID
1	46199998	5.1	5120	64 qam	1
2	25799983	4.95	5120	64 qam	4
3	32599988	4.95	5120	64 qam	3
4	39399976	5.1	5120	64 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	0	0
3	ATDMA	0	0	0	0
4	ATDMA	0	0	0	0


At this point i'm not sure where to turn as it seems that the only components in the setup we haven't replaced are the 2 way splitter, the internal cabling and the RG6 coupler to the street.
It's also possible there's an issue with the signal coming from the street cab.

Can anyone point me in the right direction with this please? Any help is greatly appeciated. Thanks.
Liam.

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Re: Unstable/Intermittent Docsis Connection

The feed to the kitchen, does it have a terminator on the cable end ?

Have you checked the 'Check Service Status' at the top of the page ?

If nothing is showing try phoning 0800 561 0061, this will tell you of more local issues that may be affecting the area. Be aware that it isn't a manned line.

Go round all the accessible co-ax connections and ensure that they are finger tight.

If everything above is OK we need do some more troubleshooting; to start with …

 

Can you set up a Broadband Quality Monitor (BQM) at thinkbroadband.com - this will give you an insight into what is happening with the signal at the other side of the Hub, it will take a few hours to get any kind of trend showing although you should post the link straight away.

Post a link to your BQM on here.

Instructions for posting BQM Link

Under your BQM graph are two links in red.

Click the lower link (Share Live Graph) then click generate.

Copy the text in the Direct Link box, beware, there may be more text than you can see.

On here click the Link icon (2 links chain to the left of the camera icon)

In the URL box paste the link you copied and in the ‘text to display’ box write My BQM then click OK - you can post the link straight away.

***********************************************************************************************************************************

Mike Robinson
Aircraft Engineer & Computer Based Training and Learning Designer for many of the world's Military Arms.


My Broadband Ping - 26_Aug_2020
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Re: Unstable/Intermittent Docsis Connection


@MikeRobbo wrote:

The feed to the kitchen, does it have a terminator on the cable end ?
It's got a standard VM wall/termination box on the end of it (e.g. it's not just a wire coming through the wall), but nothing is connected to its output.

Have you checked the 'Check Service Status' at the top of the page ?
Yes... There's never been an issue in the area when the connection has dropped.

Go round all the accessible co-ax connections and ensure that they are finger tight.
I have checked this recently. Everything checks out, you would also hope that the engineers who came to the house would have checked this.

If everything above is OK we need do some more troubleshooting; to start with …

Can you set up a Broadband Quality Monitor (BQM) at thinkbroadband.com - this will give you an insight into what is happening with the signal at the other side of the Hub, it will take a few hours to get any kind of trend showing although you should post the link straight away.

I've got an ICMP monitor graphing this connection on my own home server already, I don't see how setting up a ICMP test will show anything related to the "signal" of the connection.

Below is the ICMP test for the last 30 hours from my own server, the gaps in the graph are where the connection has dropped.

vm-home.PNG

Thanks,
Liam.

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Re: Unstable/Intermittent Docsis Connection

You also need to use the Think Broadband BQM, that is the one that VM recognise as evidence.

***********************************************************************************************************************************

Mike Robinson
Aircraft Engineer & Computer Based Training and Learning Designer for many of the world's Military Arms.


My Broadband Ping - 26_Aug_2020
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Re: Unstable/Intermittent Docsis Connection

Just noticed that two of the Upstream Power Levels are at max.

 

Channel Frequency (Hz) Power (dBmV) Symbol Rate (ksps) Modulation Channel ID
1 46199998 5.1 5120 64 qam 1
2 25799983 4.95 5120 64 qam 4
3 32599988 4.95 5120 64 qam 3
4 39399976 5.1 5120 64 qam 2

 These will need an engineer visit to get them to a more sensible level.

You can contact VM to report the problem using ...

Text service on 07533051809

150 from Virgin landline.

0345 454 1111 from any other UK  phone.

The best time to call is weekdays 08:00 to get a UK agent, anything after 10:00 you must realise that you are quite likely to get through to an offshore agent that doesn't speak English as a first language.

Or you can wait on here for one of the VM Staff to pick up the thread but this may take a few days.

***********************************************************************************************************************************

Mike Robinson
Aircraft Engineer & Computer Based Training and Learning Designer for many of the world's Military Arms.


My Broadband Ping - 26_Aug_2020
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