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Line disconnets and target SNR goes down !

yakzil
Grafter
Posts: 30
Registered: ‎16-08-2007

Line disconnets and target SNR goes down !

For the last 5 or six years my broadband connection has been very stable. Sync at around4,000kbps, SNR 6, download 3-3,300kbps, line attenuation 53-54. My local exchange was 21CN enabled and I was switched to 21CN early September. Whilst I am nominally on ADSL2+ my router (a Speedtouch 546) was reporting ADSL 2.  Initially sync went up to a bit over 5,000 and download speed improved to 4,000 kbps, SNR stayed at 6, upload speed improved as well to around 700 from 350kbps. Overall I was happy with the change. On Sep 30 I was struggling to get a connection. On checking the stats I saw my SNR was now set at 9,sync at 4119, my IP profile was 3.6. So far nothing too surprising. I assumed the SNR would in time go back to 6 with a lift in sync speed.
I had been thinking about changing the Speedtouch 546 it's quite old and they seem to have stopped updating the firmware and I wanted a wireless/wired router. Decided to get a Billion 7800N which I updated to the latest firmware. Sat 6 Oct I switched the router to the Bilion. Initially it synched at 3796 with an SNR of 9. I then switched on SRA and Phyr and rebooted to 4119 again SNR 9, router reports ADSL2 not 2+. Unfortunately we had a couple of power cuts, (the light flickering variety rather that the full blown jobs). So I guess the exchange saw a number of disconnects. Plus there was a total loss of ADSL connection for nearly an hour later in the evening. Not surprisingly sync fell to 3400, SNR 9.
Sorry it's taken so long to get to the point. I forgot to run routerstats overnight but when I switched it on in the morning sync had dropped to 3068, and SNR had also DROPPED to 3. I've had a number of crappy lines in my time but have never seen target SNR fall after interference/drop outs.  Does anyone have any idea what is going on. I was wondering about SRA and Phyr, there seem to be conflicting views as to whether these need to be supported at the exchange to function.
The only good news is that it has been running for close to 3 days at the 3 SNR margin, which suggests the line is reasonably stable. I rebooted yesterday (10th) still at 3068 and SNR 3. My IP profile is 2.7.
19 REPLIES
Plusnet Alumni (retired) orbrey
Plusnet Alumni (retired)
Posts: 10,540
Registered: ‎18-07-2007

Re: Line disconnets and target SNR goes down !

Hi,
Not sure if this will shed any light on the above but it does look like there have been a few disconnections on your line:
<img src="http://ccgi.psmith12.plus.com/visradius/generated/image13499639136818.png" />
That will most likely have caused the erratic speeds (though it does look like your line has been banded and won't sync above 3072kbps as things stand). If things settle down with the new router we'll be able to request an SNR reset on your line and let it retrain but we'd want to see three days or so of stability before we'd be happy to do that.
Best thing to do would be to keep an eye on it and raise a fault if it keeps dropping (you can do that at http://faults.plus.net) or let us know if it stays stable at the 3072 sync rate and we'll request the reset for you.
yakzil
Grafter
Posts: 30
Registered: ‎16-08-2007

Re: Line disconnets and target SNR goes down !

Thanks for that Matt. Somewhat confusing as I can't find the Monday drop on the routerstats numbers.  Tuesday I can find two drops
Tue 09 Oct 2012  02:11:31 Rx-Noise=2.4 Tx-Noise=4.3 Rx-Sync=3068 Tx-Sync=870
Tue 09 Oct 2012  02:11:51 Rx-Noise=2.3 Tx-Noise=4.2 Rx-Sync=3068 Tx-Sync=870
Tue 09 Oct 2012  02:12:11 Rx-Noise=2.4 Tx-Noise=4.2 Rx-Sync=3068 Tx-Sync=870
Tue 09 Oct 2012  02:12:31 Rx-Noise=0.0 Tx-Noise=0.0 Rx-Sync=0 Tx-Sync=0
Tue 09 Oct 2012  02:12:51 Rx-Noise=0.0 Tx-Noise=0.0 Rx-Sync=0 Tx-Sync=0
Tue 09 Oct 2012  02:13:11 Rx-Noise=4.6 Tx-Noise=18.7 Rx-Sync=3068 Tx-Sync=444

Tue 09 Oct 2012  02:50:52 Rx-Noise=4.7 Tx-Noise=18.6 Rx-Sync=3068 Tx-Sync=444
Tue 09 Oct 2012  09:01:48 Rx-Noise=0.0 Tx-Noise=0.0 Rx-Sync=0 Tx-Sync=0
Tue 09 Oct 2012  09:02:08 Rx-Noise=0.0 Tx-Noise=0.0 Rx-Sync=0 Tx-Sync=0
Tue 09 Oct 2012  09:01:48 Rx-Noise=0.0 Tx-Noise=0.0 Rx-Sync=0 Tx-Sync=0
Tue 09 Oct 2012  09:02:08 Rx-Noise=0.0 Tx-Noise=0.0 Rx-Sync=0 Tx-Sync=0
Tue 09 Oct 2012  09:02:28 Rx-Noise=5.1 Tx-Noise=18.1 Rx-Sync=3068 Tx-Sync=444
The first drop was when you capped my upload speed, hence the Tx noise increase.  For some reason the router stopped reporting after 2:50:52 and started up againat 09:01:48 at the second drop, I had assumed it was due the line capping process. The first drop on Wed was me rebooting.  The router was reporting at that time that the system up time was close to 2 days, so it seems to have ignored the drops on Tuesday.  I'm still confused as to why my SNR margin is so low, normally it is 6.  If I increase it to 6 via the router interface will the sync drop -  I'm not too sure how banding works.
Thanks
Plusnet Alumni (retired) orbrey
Plusnet Alumni (retired)
Posts: 10,540
Registered: ‎18-07-2007

Re: Line disconnets and target SNR goes down !

Usually a higher SNR means a more stable connection, so it shouldn't drop - I'm not sure if that means the router will resync though, if it does then yes you'll see a further drop there.
To be honest I think the best thing to do would be to leave it and see if it stays stable for three days now the router has changed, then we can reset things for you and let the line retrain. Manually tweaking settings like that, especially when a line is fluctuating like yours is/was really can mess up the settings that the exchange kit puts on the line - and those are all automated so there's very little we can do about it I'm afraid.
yakzil
Grafter
Posts: 30
Registered: ‎16-08-2007

Re: Line disconnets and target SNR goes down !

Thanks for that Matt, I'll take your advice.  I'm reasonably sure that the router will reboot if I increase the SNR margin to 6, and I don't want to knock my download speed any further.
yakzil
Grafter
Posts: 30
Registered: ‎16-08-2007

Re: Line disconnets and target SNR goes down !

Hi Matt
I was a bit concerned that I couldn't see some drops from my end.  Currently my router is showing
Model Name BiPAC 7800N 
Host Name home.gateway
System Up-Time 1 Day(s) 23 Hour(s)
Current Time Fri Oct 12 12:59:29 2012
Hardware Version Annex A
Software Version 1.06g
MAC Address 00:04:ed:c4:91:24
LAN IPv6 Address fe80::204:edff:fe0d:552c/64
There appeared to be two drops on router stats overnight one around 3 and the other about 7. I'm assuming that they are not drops but are routerstats anomalies. Looking at the router log for this time I see, I assume it was the DHCP request - don't know what that is about.
  Oct 12 07:02:07  daemon  DHCP SERVER: DHCPINFORM from 192.168.1.100
  Oct 12 07:04:32  daemon  DHCP SERVER: DHCP request from 00:27:0e:06:f6:71
  Oct 12 07:04:32  daemon  DHCP SERVER: DHCP ack to 00:27:0e:06:f6:71
  Oct 12 07:05:06  daemon  DHCP SERVER: DHCPINFORM from 192.168.1.100
  Oct 12 07:05:09  daemon  DHCP SERVER: DHCPINFORM from 192.168.1.100
Can you confirm that you have not seen any drops your end
Thanks
Plusnet Alumni (retired) orbrey
Plusnet Alumni (retired)
Posts: 10,540
Registered: ‎18-07-2007

Re: Line disconnets and target SNR goes down !

Nope, no drops seen here - latest connection currently ongoing over 49 hours Smiley
yakzil
Grafter
Posts: 30
Registered: ‎16-08-2007

Re: Line disconnets and target SNR goes down !

Thanks for that Matt
yakzil
Grafter
Posts: 30
Registered: ‎16-08-2007

Re: Line disconnets and target SNR goes down !

Hi Matt
According to my end my line has been stable for close to 5 days now. Sync 3068, SNR margin around 3.  Router says my max download sync is 5516.  Can you arrange for the banding to be removed.
Thanks
Plusnet Alumni (retired) chrispurvey
Plusnet Alumni (retired)
Posts: 5,369
Fixes: 1
Registered: ‎13-07-2012

Re: Line disconnets and target SNR goes down !

Hi yakzil,
I've placed the SNR reset for you, this usually takes around 4 hours but can take up-to 24 hours.
yakzil
Grafter
Posts: 30
Registered: ‎16-08-2007

Re: Line disconnets and target SNR goes down !

Thanks
Community Veteran
Posts: 19,102
Thanks: 443
Fixes: 21
Registered: ‎31-08-2007

Re: Line disconnets and target SNR goes down !

It will be interesting to see the new DSL stats, because I don't think the line was banded. You normally get a high SNRM when you are banded, Also when you look at the SNRM at anytime, say recently it was 3, that doesn't necessarily mean your Target SNRM is 3. Only immediately after a reboot/resync does the SNRM give an indication of what the Target may be. But if you have a lot of (varying) interference then you may not see the true value unless you are already monitoring the stats at the point of sync.
Well I hope the SNR reset works OK, but my suspicion is that you have a lot of noise developed for some reason. Can you hear any audible noise on the line when using the phone, or had any problems with incoming or outgoing calls? If so, confirm by plugging a known good corded phone direct into the test socket, and if still present, report to your Landline provider, get them to confirm they can hear the noise and log it as intermittent unless it's there continuously of course. Don't mention the Broadband otherwise you could get the run around. Get them to run a copper line test and call you back after.
yakzil
Grafter
Posts: 30
Registered: ‎16-08-2007

Re: Line disconnets and target SNR goes down !

The Router sync was 4419, SNR margin was 3.5 immediately after reboot, (see attachment).  Over the last 5 or 6 days or so the SNR margin has been between 3.5 and 2, the higher figure during the day and the lower figure after dark, there are no significant noise spikes (see second attachment which is pretty typical of night time) . The line doesn't sound noisy - the last time I had a noisy line which was some years ago they switched me to an aluminium line, don't want to go there again.  Currently the BT speed test gives me an IP profile of 3.9 which is 88% of the 4419 sync. It's over a day since the reset, and download speed seems stuck at around 2500, which is the same as the previous previous situation when I was syncing at 3068, SNR 3 ish.  Something somewhere seems to be throttling my download speed which historically has been 3500 ish. 
Community Veteran
Posts: 19,102
Thanks: 443
Fixes: 21
Registered: ‎31-08-2007

Re: Line disconnets and target SNR goes down !

It could be that your Plusnet Current Line speed (Login required) which needs to match the BT IP profile, hasn't yet updated. It should do within 12hrs. but sometimes fails to. Check it, and post on here, if required DCT can give it a kick.
As far as the Billion settings go, I would turn off the SRA, no BTw MSAN's or DSLAM's are set up to support it and this could be causing issues. You should be able to achieve your current sync speed with a higher SNRM.
Phyr can be supported, but it depends on the Chipset on the MSAN/DSLAM and AFAIK the setting has no detrimental effects.
yakzil
Grafter
Posts: 30
Registered: ‎16-08-2007

Re: Line disconnets and target SNR goes down !

Thanks for that, my current Plusnet line speed is 2.7, so you were right it doesn't match the BT IP profile, hadn't realised PN had to update their profile thought it was all driven by the MSAN setting.  SRA, I turned that off prior to the retrain. Phyr is on, whether it is supported is another matter, have a feeling my exchange has - Infineon gear (not sure about the spelling).