Noise Margin jumped up to 15dB today (Exchange enabled for 21CN)

[#1]

James,
When I last switched on my router (as you will see from the ticket I switched it off to see if the problem had been fixed) it sychronised at 15dB and about 6800kbps. I then telnetted my router to --snr 1 which dropped the snr down to about 9.2dB and put my speed back up to 8128kbps. This isn't what you have picked up is it?
I mention it as I have never seen my snr drop below 9.1dB after using the telnet command but it is solid at around 15.2dB with lower speed if I just leave it to BT.

[#2]

Quote from: Jameseh

I've now raised this request to BT for you.

Many thanks James.

[#3]

Hi Baldrick,
I'll have seen your enforced SNR
If you're using DMT, we won't be able to do anything until you turn it off.

[#4]

James,
I have rebooted my router. It is now running at the default 6656kbps with a 15.1 dB SNR. Thanks for looking at this for me.

[#5]

Thanks Baldrick,
Before I raise this, is there anything that you're aware of that will have caused your margin to have been increased?
Like a fault that's been fixed or something along those lines?

[#6]

I guess it's confessional time!
Yes I moved the socket into which I plug the router about the same time as this started. The full story is I used a roll of new cable that I had in stock. I didn't check the SNR before I did it but immediately after I checked to make sure that all was working and noted that the speed/SNR was less than 'normal'. As a result I removed the new cable and re-routed the old so I could use that. Before recabling I disconnected the extension wiring by unplugging the BT faceplate, so I was not doing anything silly on 'live' wiring.
As I said, I don't know for certain that this is exactly when it started, but... 

[#7]

It's quite likely
I've raised that as a fault to BT now.

[#8]

Thanks James

[#9]

Right.  I had been put on 9dB for a few days, today it is back to 12 for no reason.
BT have changed the DLM logic/software, do we know why or what it is doing now?
SW.

[#10]

Quote from: godsell4

today it is back to 12 for no reason.

Oh, there will be a reason, the challenge will be to identify it.
Firstly try asking PN if they can see anything logged.

[#11]

What are the reported errors like

[#12]

Possibly high, there is a just audible clicking on the phone line which may be the cause. I need to telent to my router to gets those numbers though, will take a look in a minute.
I thought the DLM went purely on sync speed?
Though I have maximum interleaving already I think.
SW.

[#13]

I think a big chunk of the algorithm is error rate as the router can hold synch while creating an enormous number of errors.
A good (well actually bad) example of this is the Speedtouch 546 with one of the earlier software which could ramp up the errors to the point where the traffic was essentially blocked but wouldn't resynch

[#14]

Quote from: godsell4

there is a just audible clicking on the phone line which may be the cause

Is it still there on a Quiet Line test?
(17070 option 2 using ONLY a corded unpowered phone in the Test Socket)

[#15]

Quote from: godsell4

I thought the DLM went purely on sync speed?

Error rates come into it too. There's useful background information here.