In reply to a post by R0NSKI:

I'm not, I know you only get FEC errors with interleaving on, but what's that got to do with it?

You need Interleaving on already or the first error will cause a resync.

You really need to go back to basics! I'm on fast path, yet I have errors, but I haven't resynced for 4 days 15 hours! An error will not cause a resync!

Since the last resync I have:

6 SES error seconds (One error counter that considered to be watched by the DLM)
6057 error seconds
10062 CRC errors
55973 HEC errors
0 FEC erros.

I also have 28 upstream FEC errors on fast path

This really is the last post in this thread relating to this, you obviously can't do the decent thing and carry on in the thread I made relating to this, but I can.

I still haven't seen any current reference to this "Speed" profile in any BT Openreach or Wholesale documentation. Unless I've developed a blind spot somewhere in SIN 498. As I remember earlier versions of it, there were some profiles available, but not a "speed" one.

I think I have an earlier one with that information in it downloaded on an old computer. I shall go and switch it on, but it takes 25 minutes to boot, then there will be months of updates to apply. Plus I'm about to make my dinner.

One of my concerns is that Hoolay appears most of the time to be making making statements of fact. I believe he is making reasonable deductions from stuff he has found on the internet and in these forums - which as we know may not be totally reliable - but I'm not sure everything he says is correct.

Back later ....

Just because it isn't included in the Sin 498 doc doesn't mean that the 3 GEA DLM options are no longer available,Last year there are reports posts made by ISP reps on here and other forums regarding this very subject dated DEC 13 By a Plusnet rep
And if have linked to an what appears to be an upto date BT handbook that makes a reference to the said profiles

Maybe a rep from Plusnet or Zen may kindly provide upto date info ?

Edited by tommy45 (Mon 21-Apr-14 20:10:28)

In reply to a post by R0NSKI:

You really need to go back to basics! I'm on fast path, yet I have errors, but I haven't resynced for 4 days 15 hours! An error will not cause a resync!

It will to turn Interleaving on.

In reply to a post by R0NSKI:

Batboy, I'm 100% sure you have this wrong, and I'm sure someone like WWWombat will be along tomorrow to explain.

I'm afraid that Batboy has it wrong, and the others have it right.

Having a "stable" profile does not mean that you *must* have interleaving turned on. Instead it means that, when DLM monitors your line, it has a reduced threshold for deciding whether to turn on FEC/interleaving, and has further reduced thresholds for deciding whether to turn the settings for FEC/interleaving up.

In the end, what the situation comes down to is an error rate. A "stable" line is one with a very low tolerance for errors. If your line is so perfect, and suffers no errors, then it has every right to be considered stable with a fastpath.

Unfortunately I don't know (like most people) what the thresholds are for FTTC setups. But I have seen the tables that describe the settings for 21CN... and it is very clear that the difference is indeed in the thresholds.

21CN Thresholds

I'm also going to leave it as that.

I can understand that. I've just got one more post to make, then I'll do the same...

In reply to a post by BatBoy:

Everyone seems to be ignoring the fact that Forward Error Correction requires Interleaving to be already on.

Incorrect.

Interleaving certainly makes FEC more effective for protection against longer noise bursts. And when DLM intervenes, and asks for impulse noise protection for multiple symbols, modems turn on both the FEC (for protection) *and* interleaving (to extend the protection).

However, the FEC process can work perfectly without the presence of interleaving. It can protect against small, short, bursts of noise.

Right now, my Openreach FTTC modem is not required (by DLM) to introduce FEC or interleaving: both INP values are set to zero, and delay is set to zero. However, the modem has negotiated with the DSLAM to turn on FEC in the upstream direction, while leaving interleaving turned off. Other people have reported similar settings from the Openreach modem.

In the 64 days that my link has been synchronised, I have 117k upstream FEC errors, and 8k upstream CRC errors - so my upstream is being partially protected by FEC, but not fully. ES is at 6k.

So my modem is running FEC without interleaving, and it is working.

Downstream, DLM has placed the same requirements, and the modem has negotiated both FEC and interleaving to be off. On that link, I have 315k CRC errors, no FEC, and 33k ES.

From the requirements that SIN 498 places on modems, it can be seen that DLM monitors the rate of change to ES rather than the CRC.

In reply to a post by BatBoy:

You need Interleaving on already or the first error will cause a resync.

But with 64 days of connection time, and having lots of CRCs and ESs, it is clear that the first error does *not* cause a resync, and has not turned interleaving on.

It is when the number of ES's gets too high in a 24 hour period (or, in the terminology of my threshold table in my previous post, when the "mean time between errors", MTBE, gets too low) that DLM will intervene - which will cause a resync.

Interestingly, a change of "profile" from "stable" to "speed" is only a change to the way in which DLM looks at your line's statistics. Strictly, there is no need for your line to be forced to resync for that to happen... However, I bet that such a change will cause DLM to be reset back to scratch, so it starts all monitoring again. It seems that such a reset always triggers a resync anyway.

Edited by deleted (Tue 22-Apr-14 03:11:29)

In reply to a post by BatBoy:

I expect it is, as I'm on Fastpath.
If I was on a "stable" profile, I would expect to be on Interleaving.
If I was on "super-stable" I would expect to have a high level of Interleaving applied.

not quite.

as I understand it all 3 profiles will start you off the same, so fast path with no banding.

The difference is the latter 2 have lower thresholds that can be hit before action is taken, so eg. on speed 10 drops a day might be needed to be bumped to interleaving whilst on super stable it might just be 2. Similiar with errors required as well.

So a decent line probably wouldnt see a difference between speed and stable whilst a dodgy line might.

Thank you for clarifying that.

In reply to a post by Chrysalis:

In reply to a post by BatBoy:

I expect it is, as I'm on Fastpath.
If I was on a "stable" profile, I would expect to be on Interleaving.
If I was on "super-stable" I would expect to have a high level of Interleaving applied.

not quite.

as I understand it all 3 profiles will start you off the same, so fast path with no banding.

So at the first sign of errors a "super-stable" line will resync?

Not exactly my definition of "super-stable" TBH. I would expect no resyncs at all.