cancel
Showing results for 
Search instead for 
Did you mean: 

Line switch: re-train required?

Trevor
Grafter
Posts: 124
Thanks: 1
Registered: ‎06-01-2011

Line switch: re-train required?

We had a phone fault last Wednesday (no dial tone). BT attended on Thursday, diagnosed the fault to 'somewhere under the road' and switched us to another line. Having allowed the profiles to catch up etc., I still can't get a the sych speed up to where it was before the fault so was wondering whether an SNR reset / line re-train would help?
Prior to the fault the line had held a speed of 5888kb/s for over 72 days, giving a profile of 5000. Since the repair, it has been stable but at only 4704kb/s (profile of 4000). I have just tidied up the wiring in anticipation of the re-train but that has still only brought the synch rate up to 5056, still not enough to get my 5000 profile back.
Router stats now are as follows:
Link Information
Uptime: 0 days, 0:09:16
DSL Type: G.992.1 annex A
Bandwidth (Up/Down) [kbps/kbps]: 448 / 5,056
Data Transferred (Sent/Received) [kB/kB]: 0.00 / 0.00
Output Power (Up/Down) [dBm]: 12.0 / 19.5
Line Attenuation (Up/Down) [dB]: 22.0 / 39.0
SN Margin (Up/Down) [dB]: 22.0 / 15.5
Vendor ID (Local/Remote): TMMB / TSTC
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 0 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 0 / 0
FEC Errors (Up/Down): 0 / 0
CRC Errors (Up/Down): 0 / 0
HEC Errors (Up/Down): 0 / 0
FWIW, I have never seen any FEC errors so, in spite of the high SNR, have no evidence that interleaving is applied to my connection. I don't do online gaming so, if interleaving would boost the synch speed, I would be happy to have it on.
Any help greatly appreciated,
Trevor
65 REPLIES
Community Veteran
Posts: 26,720
Thanks: 934
Fixes: 10
Registered: ‎10-04-2007

Re: Line switch: re-train required?

Why are those stats showing only 9 minutes of up time - if that had been 3 days plus PN would have no hesitation doing the reset.
jelv (a.k.a Spoon Whittler)
   Why I have left Plusnet (warning: long post!)   
Broadband: Andrews & Arnold Home::1 (FTTC 80/20)
Line rental: Pulse 8 Home Line Rental (£13/month)
Mobile: iD mobile (£4/month)
Trevor
Grafter
Posts: 124
Thanks: 1
Registered: ‎06-01-2011

Re: Line switch: re-train required?

Because, I just did a manual disconnect while I tidied up the house wiring (the old fashioned equivalent of plugging into the test socket!) Here's the stats from before I did that (sorry the formatting is messy):
Uptime:
3 days, 21:58:51
DSL Type:
G.992.1 annex A
Bandwidth (Up/Down) [kbps/kbps]:
448 / 4,704
Data Transferred (Sent/Received) [kB/kB]:
0.00 / 0.00
Output Power (Up/Down) [dBm]:
12.0 / 19.5
Line Attenuation (Up/Down) [dB]:
22.0 / 40.0
SN Margin (Up/Down) [dB]:
17.0 / 13.5
Vendor ID (Local/Remote):
TMMB / TSTC
Loss of Framing (Local/Remote):
0 / 0
Loss of Signal (Local/Remote):
0 / 0
Loss of Power (Local/Remote):
0 / 0
Loss of Link (Remote):
0
Error Seconds (Local/Remote):
1 / 0
FEC Errors (Up/Down):
0 / 0
CRC Errors (Up/Down):
31 / 1,962
HEC Errors (Up/Down):
16 / 1,214
Trevor
Community Veteran
Posts: 26,720
Thanks: 934
Fixes: 10
Registered: ‎10-04-2007

Re: Line switch: re-train required?

That definitely looks good for a reset!
jelv (a.k.a Spoon Whittler)
   Why I have left Plusnet (warning: long post!)   
Broadband: Andrews & Arnold Home::1 (FTTC 80/20)
Line rental: Pulse 8 Home Line Rental (£13/month)
Mobile: iD mobile (£4/month)
Plusnet Alumni (retired) orbrey
Plusnet Alumni (retired)
Posts: 10,540
Registered: ‎18-07-2007

Re: Line switch: re-train required?

Hi Trevor,
Just requested an SNR reset on the line for you, that should reduce the SNR and get you syncing back within the 5000 profile range. It should take effect in the next couple of hours or so, but please bear in mind it'll reset your training period so if you do need to disconnect and reconnect please actually disconnect via the router's interface before powering off or unplugging the router.
I'm not sure interleaving would make much difference to be honest though you are currently on fastpath, it'd be worth looking at if the line starts to look dicey but I suspect you'll be fine.
Community Veteran
Posts: 26,720
Thanks: 934
Fixes: 10
Registered: ‎10-04-2007

Re: Line switch: re-train required?

Interleaving would drop the sync speed - it's only worth putting on if due to a lot of errors the DLM decides to increase the target SNR giving you a greater drop in sync speed than the drop you get due to interleaving. Monitor the error rates and if they stay low you will be better off without interleaving.
jelv (a.k.a Spoon Whittler)
   Why I have left Plusnet (warning: long post!)   
Broadband: Andrews & Arnold Home::1 (FTTC 80/20)
Line rental: Pulse 8 Home Line Rental (£13/month)
Mobile: iD mobile (£4/month)
Trevor
Grafter
Posts: 124
Thanks: 1
Registered: ‎06-01-2011

Re: Line switch: re-train required?

Thanks Matt - I'll try to leave things alone through the training period. I assume the re-synch will be triggered from your end and I don't need to do anything?
Thanks for the insight into interleaving Jelv. I will indeed monitor the errors. Past experience indicates that the DLM gets twitchy if the CRC errors get up to around 10,000 per day. We'll see.
jojopillo
Grafter
Posts: 9,786
Registered: ‎16-06-2010

Re: Line switch: re-train required?

Hi Trevor,
That seems to have done the trick. I've just checked you profile and it's now 6500. I've applied that to our side so you should see the change in the next 15 minutes.
Jojo Smiley
Trevor
Grafter
Posts: 124
Thanks: 1
Registered: ‎06-01-2011

Re: Line switch: re-train required?

Thanks Jojo. Looking promising so far:
Uptime: 0 days, 2:18:27
DSL Type: G.992.1 annex A
Bandwidth (Up/Down) [kbps/kbps]: 448 / 7,680
Data Transferred (Sent/Received) [kB/kB]: 0.00 / 0.00
Output Power (Up/Down) [dBm]: 12.0 / 19.5
Line Attenuation (Up/Down) [dB]: 22.0 / 39.0
SN Margin (Up/Down) [dB]: 22.0 / 6.0
Vendor ID (Local/Remote): TMMB / TSTC
Loss of Framing (Local/Remote): 12 / 0
Loss of Signal (Local/Remote): 2 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 3 / 0
FEC Errors (Up/Down): 0 / 0
CRC Errors (Up/Down): 4 / 199
HEC Errors (Up/Down): 1 / 123
jojopillo
Grafter
Posts: 9,786
Registered: ‎16-06-2010

Re: Line switch: re-train required?

Yes, it does look good from here too Smiley
Trevor
Grafter
Posts: 124
Thanks: 1
Registered: ‎06-01-2011

Re: Line switch: re-train required?

By 11:20 last evening, the SNR had dropped to 4.5 and the errors were mounting up:
Uptime:
0 days, 8:29:13
DSL Type:
G.992.1 annex A
Bandwidth (Up/Down) [kbps/kbps]:
448 / 7,680
Data Transferred (Sent/Received) [kB/kB]:
0.00 / 0.00
Output Power (Up/Down) [dBm]:
12.0 / 19.5
Line Attenuation (Up/Down) [dB]:
22.0 / 39.0
SN Margin (Up/Down) [dB]:
22.0 / 4.5
Vendor ID (Local/Remote):
TMMB / TSTC
Loss of Framing (Local/Remote):
12 / 0
Loss of Signal (Local/Remote):
2 / 0
Loss of Power (Local/Remote):
0 / 0
Loss of Link (Remote):
0
Error Seconds (Local/Remote):
7 / 0
FEC Errors (Up/Down):
0 / 0
CRC Errors (Up/Down):
459 / 14,225
HEC Errors (Up/Down):
83 / 10,010
So, no great surprise to find this morning that the target SNR had been ratcheted up and the synch rate dropped to 6272:
Uptime:
0 days, 2:36:03
DSL Type:
G.992.1 annex A
Bandwidth (Up/Down) [kbps/kbps]:
448 / 6,272
Data Transferred (Sent/Received) [kB/kB]:
0.00 / 0.00
Output Power (Up/Down) [dBm]:
12.0 / 19.5
Line Attenuation (Up/Down) [dB]:
22.0 / 39.0
SN Margin (Up/Down) [dB]:
22.0 / 10.5
Vendor ID (Local/Remote):
TMMB / TSTC
Loss of Framing (Local/Remote):
26 / 0
Loss of Signal (Local/Remote):
4 / 0
Loss of Power (Local/Remote):
0 / 0
Loss of Link (Remote):
0
Error Seconds (Local/Remote):
34 / 0
FEC Errors (Up/Down):
0 / 0
CRC Errors (Up/Down):
0 / 78
HEC Errors (Up/Down):
0 / 50
The last bit of our line is overhead and two of the four poles are shared with the power lines, one of which also has a street light screwed to it about 1.5m below the telephone line. Do you reckon that might be the reason the SNR sags during the hours of darkness, or is this a general phenomenon. Not that it makes any difference I suppose - I don't fancy my chances of getting the street light or power lines re-positioned!
Out of curiousity, I would like to monitor the SNR and error rates more closely but, as a Mac user, I'm not aware of a way of doing it - short of setting an hourly alarm and checking manually - and I'm not that curious!
Trevor
Trevor
Grafter
Posts: 124
Thanks: 1
Registered: ‎06-01-2011

Re: Line switch: re-train required?

I'm beginning to think my line really is afraid of the dark! It dropped further (apparently at around 4am) to 5984kbps - no obvious change to the target SNR though.
I don't really understand this. When I checked last night at 10pm, it had chalked up only 460CRC and 265HEC errors over a 17hr period and the SNR was at 8.5dB. Admittedly it hadn't been dark for long but I certainly wasn't expecting to see a speed drop again this morning.
Knowing that this line is capable of supporting a sych rate of over 7000 during the day (i.e. when I want to use it) only makes this DLM behaviour more frustrating - almost enough to tempt me to going back to the old practice of turning the router off overnight!
Trevor
Router stats as at 9am today:
Uptime: 0 days, 4:57:11
DSL Type: G.992.1 annex A
Bandwidth (Up/Down) [kbps/kbps]: 448 / 5,984
Data Transferred (Sent/Received) [kB/kB]: 0.00 / 0.00
Output Power (Up/Down) [dBm]: 12.0 / 19.5
Line Attenuation (Up/Down) [dB]: 22.0 / 39.0
SN Margin (Up/Down) [dB]: 23.0 / 11.0
Vendor ID (Local/Remote): TMMB / TSTC
Loss of Framing (Local/Remote): 28 / 0
Loss of Signal (Local/Remote): 5 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 58 / 0
FEC Errors (Up/Down): 0 / 0
CRC Errors (Up/Down): 0 / 85
HEC Errors (Up/Down): 0 / 51
jojopillo
Grafter
Posts: 9,786
Registered: ‎16-06-2010

Re: Line switch: re-train required?

Hi Trevor,
As your connection keeps dropping I would suggest you look here for some tips. If you feel that these have made no difference then I would raise a fault. The thing to consider is that currently interleaving is off, and once you raise a dropping connection fault an order to put interleaving on will automatically be placed.
Jojo Smiley
Trevor
Grafter
Posts: 124
Thanks: 1
Registered: ‎06-01-2011

Re: Line switch: re-train required?

Hello Jojo,
When you say 'the connection keeps dropping' are you seeing more disconnections than the two overnight ones that I reported? If raising a fault will help to get the line performing nearer to its potential then I will happily do it, but I am concerned that BT would dismiss two re-synchs during the training period as just the DLM doing its job.
Thanks for the troubleshooting link but, as I think you guessed, there is nothing there to help. If interleaving will improve the daytime throughput then I'd be inclined to go for it.
My other area of indecision relates to ADSL 2+.  I am aware that a few people have been disappointed after transferring so I have never followed it up. My gut feel is that if we could get this line performing (on ADSL 1)  reliably at a lower SNR margin (say synching reliably at around 6500) then it would be worth a go. I would very much appreciate your advice.
Trevor
jojopillo
Grafter
Posts: 9,786
Registered: ‎16-06-2010

Re: Line switch: re-train required?

HI Trevor,
I was actually going by what you were saying about it dropping. Looking at it, it doesn't seem that bad. As far as ADSL2+ goes, if the line stays steady I'd go for it.
Jojo Smiley