General : 50MB - Intermittent Fault

[chambohambo]

Originally Posted by vm_tech

Your upstream seems to constantly be around the 43 mark which is fine, has your issue gone away now or is the upstream fluctuating?

Thanks for taking the time to respond to my post.

At the minute both the TiVo box and Super Hub 2 are stable but that can all change. This is the intermittent problem, it can be stable for hours, then out of the blue I get the problem. Take a look up at my posts.

---------- Post added at 18:26 ---------- Previous post was at 18:23 ----------

Originally Posted by vm_tech

Your upstream seems to constantly be around the 43 mark which is fine, has your issue gone away now or is the upstream fluctuating?

Do you work for Virgin Media?

[MUD_Wizard]

[img][/img]

[img][/img]

[img][/img]

[img][/img]

[img][/img]

Don't have a lot of time to post.

Just looking at the BQM's the issue on the 16th between 1am and 10:30am definitely looks to me like an SNR fault. As does the period between 8pm and midnight, plus 3-6am on the 17th.

NOT a peak-time only issue.
NOT an afternoon issue caused by over-heating cabinet.
Seems to be random with plenty of packet loss on the BQM's at times that haven't been recorded.
SNR fault's are known to be intermittent and random.

[chambohambo]

Originally Posted by MUD_Wizard

Don't have a lot of time to post.

Just looking at the BQM's the issue on the 16th between 1am and 10:30am definitely looks to me like an SNR fault. As does the period between 8pm and midnight, plus 3-6am on the 17th.

NOT a peak-time only issue.
NOT an afternoon issue caused by over-heating cabinet.
Seems to be random with plenty of packet loss on the BQM's at times that haven't been recorded.
SNR fault's are known to be intermittent and random.

Thanks for taking the time to respond to my post.

Any idea how this would get fixed? I have technician coming out tomorrow. I don't want to be fobbed off saying everything is within spec.

[chambohambo]

Upstream power levels swinging around again 21:00.

Downstream Channels
Lock Status Channel ID Frequency Modulation Rx Power RxMER Pre RS Errors Post RS Errors
Locked 9 315000000 Hz 256 QAM 3.8 dBmV 37.9 dB 8168 1703
Locked 3 267000000 Hz 256 QAM 3.2 dBmV 37.1 dB 30525 2192
Locked 4 275000000 Hz 256 QAM 3.3 dBmV 37.4 dB 4922 1699
Locked 5 283000000 Hz 256 QAM 3.5 dBmV 37.4 dB 3368 1555
Locked 6 291000000 Hz 256 QAM 3.4 dBmV 37.9 dB 2260 1157
Locked 7 299000000 Hz 256 QAM 3.4 dBmV 38.3 dB 2404 1222
Locked 8 307000000 Hz 256 QAM 3.3 dBmV 38.3 dB 2736 1384
Locked 10 323000000 Hz 256 QAM 4.2 dBmV 39.0 dB 3130 1959

Upstream Channels
Lock Status Channel ID Frequency Modulation Tx Power Mode Channel Bandwidth Symbol Rate
Locked 34 35800000 Hz ATDMA 53.0 dBmV 64QAM 6400000 Hz 5120 Ksym/sec
NotLocked 0 0 Hz 0 dBmV 0 Ksym/sec
NotLocked 0 0 Hz 0 dBmV 0 Ksym/sec
Locked 35 27400000 Hz ATDMA 53.3 dBmV 64QAM 6400000 Hz 5120 Ksym/sec

[MUD_Wizard]

How did the tech visit go yesterday?

Originally Posted by chambohambo

How do you pin point the cause of this fault? I have a technician coming out in a few days from Virgin Media, knowing my luck when the technician arrives, all the power levels will be stable.

Tricky. Most of them won't look at your BQM if everything looks fine on their signal/power stats.

Just try to make the tech aware of the extent of the issues you're having with SNR (e.g. modulations changing) and power level problems on the upstream.

There's not a lot else you can do. You may need to go through a couple of tech's before things get escalated.

Like the General said, escalation can take time and a certain critical mass of customers complaining. Assuming other people are affected and not just you.

I often take the view with SNR fault's that reporting it then sitting back and let other people do the moaning can be the easier option.

Originally Posted by chambohambo

What do you think the technician will do to try and fix this intermittent fault? Like I have said knowing my luck, when the technician comes out everything will be stable.

Unfortunately tech's don't have any equipment for tracing SNR fault's, especially intermittent ones. It's just a case of trial and error, plus relying on what the stats on the CMTS say.

It may not be something they can do anything about anyway; Regular tech's can only deal with things from the hub to the local cabinet. If it's further upstream then a network tech/engineer will need to be called in.

At this stage you don't know where the issue lies.

[chambohambo]

Thanks for taking the time to respond to my post.

The technician changed the splitter and isolator and also put new connectors at the end of the cables. For the past few weeks it has been stable. So I am guessing the splitter or isolator was the cause of the problem.

How do these power levels look below?


Downstream Channels
Lock Status Channel ID Frequency Modulation Rx Power RxMER Pre RS Errors Post RS Errors
Locked 2 259000000 Hz 256 QAM 10.2 dBmV 39.0 dB 7515 578
Locked 1 251000000 Hz 256 QAM 10.0 dBmV 38.3 dB 29132 609
Locked 3 267000000 Hz 256 QAM 10.3 dBmV 38.6 dB 3899 580
Locked 4 275000000 Hz 256 QAM 10.3 dBmV 38.3 dB 2067 584
Locked 5 283000000 Hz 256 QAM 10.3 dBmV 39.4 dB 622 618
Locked 6 291000000 Hz 256 QAM 10.2 dBmV 39.4 dB 548 548
Locked 7 299000000 Hz 256 QAM 10.5 dBmV 39.4 dB 589 579
Locked 8 307000000 Hz 256 QAM 10.3 dBmV 39.4 dB 564 558


Upstream Channels
Lock Status Channel ID Frequency Modulation Tx Power Mode Channel Bandwidth Symbol Rate
Locked 35 27400000 Hz ATDMA 37.3 dBmV 64QAM 6400000 Hz 5120 Ksym/sec
NotLocked 0 0 Hz 0 dBmV 0 Ksym/sec
NotLocked 0 0 Hz 0 dBmV 0 Ksym/sec
Locked 33 45800000 Hz ATDMA 39.0 dBmV 64QAM 6400000 Hz 5120 Ksym/sec

Originally Posted by MUD_Wizard

How did the tech visit go yesterday?



Tricky. Most of them won't look at your BQM if everything looks fine on their signal/power stats.

Just try to make the tech aware of the extent of the issues you're having with SNR (e.g. modulations changing) and power level problems on the upstream.

There's not a lot else you can do. You may need to go through a couple of tech's before things get escalated.

Like the General said, escalation can take time and a certain critical mass of customers complaining. Assuming other people are affected and not just you.

I often take the view with SNR fault's that reporting it then sitting back and let other people do the moaning can be the easier option.




Unfortunately tech's don't have any equipment for tracing SNR fault's, especially intermittent ones. It's just a case of trial and error, plus relying on what the stats on the CMTS say.

It may not be something they can do anything about anyway; Regular tech's can only deal with things from the hub to the local cabinet. If it's further upstream then a network tech/engineer will need to be called in.

At this stage you don't know where the issue lies.

[vm_tech]

Originally Posted by chambohambo

Thanks for taking the time to respond to my post.

The technician changed the splitter and isolator and also put new connectors at the end of the cables. For the past few weeks it has been stable. So I am guessing the splitter or isolator was the cause of the problem.

How do these power levels look below?


Downstream Channels
Lock Status Channel ID Frequency Modulation Rx Power RxMER Pre RS Errors Post RS Errors
Locked 2 259000000 Hz 256 QAM 10.2 dBmV 39.0 dB 7515 578
Locked 1 251000000 Hz 256 QAM 10.0 dBmV 38.3 dB 29132 609
Locked 3 267000000 Hz 256 QAM 10.3 dBmV 38.6 dB 3899 580
Locked 4 275000000 Hz 256 QAM 10.3 dBmV 38.3 dB 2067 584
Locked 5 283000000 Hz 256 QAM 10.3 dBmV 39.4 dB 622 618
Locked 6 291000000 Hz 256 QAM 10.2 dBmV 39.4 dB 548 548
Locked 7 299000000 Hz 256 QAM 10.5 dBmV 39.4 dB 589 579
Locked 8 307000000 Hz 256 QAM 10.3 dBmV 39.4 dB 564 558


Upstream Channels
Lock Status Channel ID Frequency Modulation Tx Power Mode Channel Bandwidth Symbol Rate
Locked 35 27400000 Hz ATDMA 37.3 dBmV 64QAM 6400000 Hz 5120 Ksym/sec
NotLocked 0 0 Hz 0 dBmV 0 Ksym/sec
NotLocked 0 0 Hz 0 dBmV 0 Ksym/sec
Locked 33 45800000 Hz ATDMA 39.0 dBmV 64QAM 6400000 Hz 5120 Ksym/sec

Downstream is a little high but if it's not giving grief I wouldn't worry about it. I didn't think it was a network SNR fault (I used to be a VM network engineer). Seems like it was like you said a faulty splitter/Iso or maybe a bit of braiding around the "stinger" on the cable. If you get anymore grief first thing to try would be a 6db wideband attenuator to get your levels closer to spec, but upstream levels are much more important than downstream (for stability).