Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[youngsyp]

Hi,

I've been having some intermittent issues on my line for the last few years, essentially after moving to FTTC. This year I've had 5 separate OR visits and each time they 'fixed' a different issue. The last 3 changes were removing circa 80m of over head cable from my run from the cab, fixing a 'damp' joint in a footway box and performing a 'lift and shift' in the fibre cabinet. This latest fix took place on Thursday. I'm still not 100% sure whether the underlying issue has been fixed, as it's very intermittent however, I'm now concerned that as part of the lift and shift, they've banded my downstream rate. The reason for this that up until these changes, every re-sync has resulted in an increase in downstream rate, due to DLM reducing the SNRM target. The line has re-synced 3 or 4 times since Thursday, and assuming it's DLM as the line is perfectly stable, but, the SNRM target stays at circa 6dB. I've performed a BT speedtest, with further diagnosis and noted the IP Profile included in the results (attached).

Have I been banded?

Cheers,

Paul

[Alex Atkin UK]

Banding should be obvious as the SNRm would be higher than 6dB (usually by a couple of dB or more) immediately after a resync and the sync rate would remain exactly the same each time.

If you previously had a 3dB SNR and its now 6dB, that is a profile change not banding. DLM has decided 3dB is not stable and it may reduce it again later if your line is stable enough.

[youngsyp]

Yes agreed and on further thought and research, I don't think I have been banded. However, is it possible that a line can be set to always re-sync at 6dB, regardless of line conditions?

My experience of DLM differs somewhat as even with this intermittent issue, post DLM reset, it would quickly 'train' to speed the line up and it was sat with a 3dB SNRM target for years. As part of the issues I've had, at one point the line dropped and re-synced at 1.7dB and remained rock solid until the next re-sync. So the typical stability of my line is pretty exceptional. With all the changes to the line I've had these last visits (shortening the line by 86m (now circa 816m from cab), having new cable installed from the NTE to the DP in the street (circa 80m again I'd think), the joint fix and lift and shift), it is now even more stable with the downstream SNR trace pretty much being flat most of the time. As such, the current behaviour with the SNRM target staying at 6dB is unusual. Maybe I'm just being impatient and DLM will start to intervene in the near future.

When the engineer was here on Thursday, he mentioned that putting the line on a 'stability profile' could be worth a try, this is what's got me thinking, that maybe he requested it. Not that he said he'd done so but...

Paul

[Black Sheep]

A 'Lift & Shift' (performed by having a co-op call with <usually>, our partners in India) takes the circuit back to default settings .... as if it's your very fist time ever having FTTC.

Regarding 'Stability profile', he would then have to make a further co-op call to have these new settings applied.

There is one other issue that I have come across numerous times, when working on high repeat-report VDSL faults ... and that is not the profile, but rather the policy that was causing mayhem !!

There are three policies that your ISP can choose from (Speed, Stable, Standard) .... ok, there's a fourth (Custom), but I've never, ever seen that used in anger .... and if your line is susceptible to noise through whatever reason, like aluminium cable for example, then being on the wrong policy will cause problems.

Not necessarily aimed just at yourself, youngsyp, but for anyone else reading who may be experiencing similar ??. 

[mofa2020]

There are three policies that your ISP can choose from (Speed, Stable, Standard) .... ok, there's a fourth (Custom), but I've never, ever seen that used in anger .... and if your line is susceptible to noise through whatever reason, like aluminium cable for example, then being on the wrong policy will cause problems.

So the line is stuck with a certain policy till the ISP change it manually for some reason? do DLM action to apply interleave / fastpath or g.inp depend on the policy the ISP uses?

[kitz]

The ISP selects with Openreach which policy they prefer. That is then generally the default profile for all of their customers.
Very few ISPs will change it.   About the only one I've heard of doing so is BTr, because they use both profiles - supposedly depending upon if the customer has IPTV.
 
Good luck getting the likes of TT/Vodafone/Sky etc to change it.   1) CS probably wont know what you mean.  2). None of the will deviate from Standard.

See here
https://kitz.co.uk/adsl/DLM.htm#dlm_stability_level

do DLM action to apply interleave / fastpath or g.inp depend on the policy the ISP uses?

Yes - it can affect how soon DLM takes action..  and how long  it takes to reverse.   Each policy has a different MTBE figure, which will in turn affect your ILQ status.

See
https://kitz.co.uk/adsl/DLM.htm#DLM_categorising_the_line 

[youngsyp]

A 'Lift & Shift' (performed by having a co-op call with <usually>, our partners in India) takes the circuit back to default settings .... as if it's your very fist time ever having FTTC.

Regarding 'Stability profile', he would then have to make a further co-op call to have these new settings applied.

There is one other issue that I have come across numerous times, when working on high repeat-report VDSL faults ... and that is not the profile, but rather the policy that was causing mayhem !!

There are three policies that your ISP can choose from (Speed, Stable, Standard) .... ok, there's a fourth (Custom), but I've never, ever seen that used in anger .... and if your line is susceptible to noise through whatever reason, like aluminium cable for example, then being on the wrong policy will cause problems.

Not necessarily aimed just at yourself, youngsyp, but for anyone else reading who may be experiencing similar ??. 

Great post and very informative, thank you.

With regards your comments on the lift and shift, that would imply that DLM is 'reset', automatically, as a part of the process?! So maybe I am being inpatient as when I first moved to FTTC, I seem to recall it took longer to 'settle', than it did with a recent DLM reset.
Interestingly, G.INP was still applied post lift and shift. Is that just because it's applied by default now?

When the engineer came back from the cab, he made another call to India (he mentioned before he went to the cab that making a call was part of the lift and shift task, as you've stated) I assume, to ensure the line was on the 80/20 service I'm paying for. There was no mention, on his part, of it being set to a specific 'policy'.

My ISP is Andrews & Arnold, so I'll get onto them on Monday and ask some questions.

Paul

[youngsyp]

The ISP selects with Openreach which policy they prefer. That is then generally the default profile for all of their customers.
Very few ISPs will change it.   About the only one I've heard of doing so is BTr, because they use both profiles - supposedly depending upon if the customer has IPTV.
 
Good luck getting the likes of TT/Vodafone/Sky etc to change it.   1) CS probably wont know what you mean.  2). None of the will deviate from Standard.

See here
https://kitz.co.uk/adsl/DLM.htm#dlm_stability_level
Yes - it can affect how soon DLM takes action..  and how long  it takes to reverse.   Each policy has a different MTBE figure, which will in turn affect your ILQ status.

See
https://kitz.co.uk/adsl/DLM.htm#DLM_categorising_the_line

I can't believe I've never seen the page you've linked before. It answers so many questions. Thank you.

Quickly looking at the MTBE figures, my line would certainly be green. Figures for E/S per day, for the last four days are: 42, 300 (when OR were here), 104, 57 (yesterday). And the MTBR figures would be typically 1 per day, or less and a couple on Friday, when I updated the firmware on my gateway.

This gives me all the ammunition I should need to impress on AA how stable the line is.

Paul

[youngsyp]

Just noticed I've had a retrain in the last 40 minutes (reason 1) and the sync and attainable, on the downstream, have increased by about 2Mb/s. The SNRM target is the same at 6dB though.

Paul

[mofa2020]

It is normal to have such small fluctuation, as long as the SNRm is 6.xdb.

[Alex Atkin UK]

Its normal to have fluctuation, but any unexpected re-sync that doesn't seem to have changed anything else is something to keep an eye on.