Ah, is it that 2nd line pwning it? Yeah, I was thinking of switching to Virgin Media if/when it comes here, but then I'd loose the interest DSL technology gives me.

Currently away and the FEC's are still accumulating at quite a high rate, so it's nothing in our house. Brilliant.

It's not an issue.

Stop trying to make it one.

In reply to a post by WilliamGrimsley:

Thanks for the explanation, David. I do understand how FEC's work and yes, I agree I shouldn't be concerned about them. But, I just want to find what's causing them early before it potentially causes an issue down the line.

I'm really not sure that you do understand how FEC works.

The whole point of Forward Error Correction is that you build sufficient redundancy into the bitstream not only to detect errors but to be able correct them in most cases. On your line, DLM has tuned the parameters to the point where, though FEC is coming into play a fair bit, almost all the errors are being dealt with by FEC and those that are not corrected by FEC are being dealt with by the higher level Reed Solomon and retransmission mechanisms.

Bitstream corruption is a fact of life for many real life DSL circuits, as they're using carriers way into HF (and, I believe, beyond 30MHz into VHF for G.FAST) on twisted pair cabling that was originally deployed for a few kHz of baseband voice. That DSL works so well in often hostile real life conditions on less than brilliant cabling is a testament to how well it is designed. Though you have told us several times how you think DLM is rubbish (or words to that effect), it's doing what it is supposed to on your circuit; had DLM not selected that level of FEC you would likely either have service affecting problems or would have to run at a lower sync speed.

The mechanisms employed by DLM and the DLM algorithm itself are not always going to succeed. Sometimes DLM will do something inappropriate. Sometimes there is a genuine fault in the cable plant or the RF environment is so hostile that the noise is service affecting. I'm not the only person in these forums and far from the only person in the country who holds a licence permitting me to put a 26dBW carrier with DSL hostile modulation applied into the feedpoint of an efficient directional antenna in various parts of the spectrum used by DSL (though, in my case, I only have equipment capable of 20dBW input to the feeder and do not have strongly directional antennas).

It can be difficult enough to track down a source of service affecting noise with a proper REIN meter or a spectrum analyser plus, in either case, the skills and experience to use these tools effectively. You might just succeed in finding something on your premises with a medium wave radio, but it may well prove a futile search - and, in any event, you do not have a service affecting issue. DLM has tuned your line parameters appropriately and the statistics show that the error correction and mitigating measures are working well.

Absent some major change in conditions, such as a line plant fault, it is unlikely that your increasing FEC count will turn into a service affecting fault, which is why so many posters are telling you to stop obsessing over the statistics from your router. If your line suffers at some point in the future from increased crosstalk, Openreach do not regard this as a fault; they have taken the perfectly reasonable business decision not to make a widespread roll-out of VDSL2 vectoring, but to put their investment into ultrafast roll-out (G.FAST, which always uses vectoring, and FTTP).

It can be difficult enough to track down a source of service affecting noise with a proper REIN meter or a spectrum analyser plus, in either case, the skills and experience to use these tools effectively.

Yep, lots of things produce noise audible on an medium wave radio, this does NOT mean they are service affecting.

I'm not making it an issue, why would I want to do that? Also, maybe try using "please"...

Edited by deleted (Thu 18-May-17 21:16:08)

Ok, thanks for the incredibly detailed explanation, David. I understand some of your points there, but most of it went straight over the top of my head! Makes me realise that I only have a basic understanding of DSL! I know I'm coming over that I'm obsessing, but honestly, I really am not, I'm just interested in what could be causing all these retransmissions, because if they don't need to be there, they shouldn't be. Anyway, when I return home, I'll try and find an AM radio and see if I can find anything that could be causing the problem. If I can't, fine. I would then presume it is a device that is in another property.

Edited by deleted (Fri 19-May-17 09:18:49)

I know that, but it would be interesting to see what is causing the FEC's.

I do understand FTTC users will try there best to reduce any internal noise getting into ones modem, now i think in the past we discussed the use of ethernet powerline adapter can increase this noise and see a increased in FEC errors on the modem well it did for me.

So if you could use X amount of LAN cable just as a trial and put the PLA's aside and monitor your stats for a few days or a week could help in ruling that out as a possible cause.

In reply to a post by WilliamGrimsley:

Ok, thanks for the incredibly detailed explanation, David. I understand some of your points there, but most of it went straight over the top of my head! makes me realise that I only have a basic understanding of DSL!

As you have been told by several people many times before you went on a short sabbatical, and as you yourself have said at least three times. What is it that makes you repeatedly "unrealise" it?

I know I'm coming over that I'm obsessing, but honestly, I really am not,

You really, really are.

I'm just interested in what could be causing all these retransmissions,

FECs are not retransmissions.

because if they don't need to be there, they shouldn't be.

They do need to be there. They need to be there precisely because they prevent excess retransmissions.

Anyway, when I return home, I'll try and find an AM radio and see if I can find anything that could be causing the problem. If I can't, fine. I would then presume it is a device that is in another property.

A better way of finding if there is anything in your property causing the errors that are corrected by the FEC system is to turn off at the mains so nothing left on standby everything else in the property powered by electricity. Not forgetting fridges, freezers and even a gas cooker if you have one. Nearly all modern gas cookers are kept alive by electricity.

As for finding the source by using an AM radio, it doesn't need to be in a property. A mild electric storm (or thunderstorm) miles away can send you enough electrostatic noise to cause your modem to re-sync at a ridiculously low speed because it hasn't got the processor power to do all the corrections or handle the resultant retransmissions.

Phone wires passing over electricity substations, passing within a few metres of a workshop with welding machines, dodgy street lights particularly the new LED ones, faulty traffic lights, road works anywhere between you and the cabinet on FTTC or you and the exchange on ADSLx, etc. etc.