Openreach FTTC with 3dB

MrSaffron

My parents has complaint about their FTTC has disconnected every days lately. They have no problem before Openreach has changed DLM on their line with 3dB SNR target.

I have a look at their plusnet hub one router with helpdesk and can see their line at 2.5dB downstream and 6.1dB upstream and check the logs as I can see everydays of DLM made change at their downstream SNR from 3.1dB to 4dB, 5dB and back to 3dB and so on.

I think the only way to stable their line is to request Plusnet to ask Openreach to DISABLED Target SNR 3dB and locked at 6dB default to keep their line stable.

Can Openreach do this or can't do it, up to DLM to do this way? My parents are getting fed up with it and want to stay stable as it was. Their line was stable from 2014 until few months ago when DLM kicked in 3dB and caused more problems.

No idea why you aim the question at MrS.
This is a community forum.

It can't be done though.

You could ask Plusnet to move your parents from the DLM Speed profile that Plusnet use to the Standard profile.
It would reset the DLM and be less likely to bounce between SNRM targets.

A bit of me thinks .. �it�s just desserts� after all those countless posts by the OP whining about DLM and speed caps etc in the past.

Speed is nothing without stability.

In reply to a post by j0hn83:

No idea why you aim the question at MrS.
This is a community forum.

It can't be done though.

You could ask Plusnet to move your parents from the DLM Speed profile that Plusnet use to the Standard profile.
It would reset the DLM and be less likely to bounce between SNRM targets.

It can be done by Openreach as part of a visit to the home, I�ve arranged that in the past and was told that it will stick until another DLM recalc is requested.

@j0hn83 I�m not sure how Plusnet would arrange that though, as they can�t do it themselves. They may have some kind of mechanism to request Openreach do this, but that request could be turned down.

Replying to Icaras but really a general question.

What is involved in a DLM re-calc? Is it so involved or so disruptive of the network that OR reserve the right to do it themselves to avoid excessive disruption? Or, with my cynical head on, is it a hangover from the old monopoly days and the remnants of the old Civil Service mentality still survive in some of the OR processes?

BT Wholesale have three stability options that correspond to the three Openreach ones, though confusingly differently named. (Or at least they used to be).

AIUI any CP can request a change of stability setting. For BT Wholesale based ones it would be by requesting a change to theirs, and hence through that route to the Openreach one. Sky, TalkTalk et al would do it directly to Openreach.

There's actually 4 DLM profiles.

Speed, Standard and Stable are the ones frequently discussed.
Speed and Standard are the most common.
I'm not aware of any residential ISP's using the Stable profile.

I've always understood that none of the 3 DLM profiles mentioned above can have any manual intervention. The DLM is entirely automated.
SNRM can't be fixed or changed manually.

There is a 4th DLM profile often overlooked or unknown to many.
This is named "Custom" and AIUI can be set to a fixed setting like you suggest.
Documentation for ISP's tells them the Custom DLM profile should only be used on test lines.
I've no doubt the OpenReach DCoE could set this up for unique troublesome lines and perhaps that's what was used in your example.

Would be interesting to find out if when this was done on the job you mentioned if you could see the DLM profile in use and if it was the Custom profile.

@j0hn83 I�m not sure how Plusnet would arrange that though, as they can�t do it themselves. They may have some kind of mechanism to request Openreach do this, but that request could be turned down.

OpenReach introduced a trial for ISP's to request DLM resets a while ago.
Plusnet are the most willing to to do this with many recent examples on their forums.
They request it from BT Wholesale who in turn pass that on to OpenReach.
It can and does get rejected on occasion.

Many ISP's won't request it at all.

I had a similar problem with TalkTalk. After several complaints someone called me, I explained the problem, He there and then put me on a fixed 6dB.

In reply to a post by Brunel:

I had a similar problem with TalkTalk. After several complaints someone called me, I explained the problem, He there and then put me on a fixed 6dB.

That's ADSL.

No ISP has DLM control on FTTC.

Icaras is an OpenReach engineer and was talking about something very out of the ordinary.

Thanks for the info.

Here is reply from PN Tech Staff

We can try changing the stability setting to Stable which should in theory influence DLM in its decision making stopping it moving the target the SNRM down to 3dB but it's not guaranteed

Quite.

Yes, my apologies I forgot about that, and I don�t think it�s a trial anymore. The way I understood that it works is that an ISP can request recalcs on a set number of lines per day, or per week. I can�t remember which.

However in my experience ISPs simply told us �we don�t get involved in DLM at all on FTTC, it�s all handled by Openreach�.

I often wondered if ISPs understood that they could now actually request it themselves under this new process. I actually don�t know much about the profiles that you speak of, never needed to get involved in that and no one ever mentioned it.

In reply to a post by Brunel:

I had a similar problem with TalkTalk. After several complaints someone called me, I explained the problem, He there and then put me on a fixed 6dB.

Not possible

Edited by deleted (Mon 07-Oct-19 15:39:27)

Definitely a trial, and not all ISP's choose to take part.

https://www.openreach.co.uk/orpg/home/updates/briefi...

https://www.openreach.co.uk/orpg/home/updates/briefi...

It was announced it was going to end in April but was announced to continue in May.
No updates since.

It is limited to 1000 lines per day.

edit: don't know how I just replied to your post but my reply is magically above yours.
ah, you double posted.

Edited by j0hn83 (Mon 07-Oct-19 17:38:58)

I don�t think that�s a trial anymore. The way I understood that it works is that an ISP can request recalcs on a set number of lines per day, or per week. I can�t remember which.

However in my experience ISPs simply told us �we don�t get involved in DLM at all on FTTC, it�s all handled by Openreach�.

I often wondered if ISPs understood that they could now actually request it themselves under this new process. I actually don�t know much about the profiles that you speak of, never needed to get involved in that and no one ever mentioned it.

This is exactly the problem I had as well!

In recent few years Openreach lowered the DLM down to 3dB which coincided with my daily internet disconnections. This is despite my line being EO.

With Sky this happened like 3-4 years ago. I had to call tech support, they sent a Sky Engineer back then and only gave me a new router. The problem did not solve.

It was only until I called again Sky and they manually set noise margin to 9dB and my disconnections stopped.

This same problem continued when last year I switched to Plusnet and in the same way it was disconnecting viciously for over a month. Regardless of how much the connection was dropping the noise margins would continue to return back to 3dB hence why the problem would never go away.

I contacted Plusnet forum for ADSL and upon capping the noise margin to 9dB immediately the problem went away.

This issue is not internal wiring in my property. It is because the Exchange Only line is over 1km long in length from exchange so there is extra noise on the line causing connection to drop out. 3dB is only suitable for rock solid lines that can maintain sync and usually when the copper line is short.

Anyway... I finally have FTTC upgraded with a cabinet that is 0.2 miles away from 1st of October. I will have to test in January after the end of my contract to see if when I switch to FTTC whether my line will cope under a 3dB noise margin profile. This is a headache that I still have as I outlined in a similar topic expressing my same concerns.

@adslmax: May I know how long your parents property is from the Fibre cabinet? This should give clues! If it is comparatively short then the problem is either line or issue with the parents property line. If it is long like 1km for example this will explain the reason for this vicious cycle of drop-outs...

In reply to a post by BLaZiNgSPEED:

@adslmax: May I know how long your parents property is from the Fibre cabinet?

Estimated Line Length In Metres 463.2 from PN GEA Test

In reply to a post by adslmax:

In reply to a post by BLaZiNgSPEED:

@adslmax: May I know how long your parents property is from the Fibre cabinet?

Estimated Line Length In Metres 463.2 from PN GEA Test

Right, there is some length. But it still shouldn't be a problem. Have you also checked here? https://www.dslchecker.bt.com/adsl/ADSLChecker.Addre...
What is the minimum speed on the Downstream Line Rate(Mbps) and Downstream Handback Threshold(Mbps) checker?

Have you also tried directly plugging in the telephone cable to the test socket by removing the master socket? https://uno.help/public/attachments/b974d2473f4eeda5...

Also have you taken a look at the miss calls on your phone? Sometimes if someone tries to call landline phone some routers cause the internet to disconnect. Make sure when there is a disconnection to dial 1471 and check for any miss calls and see if this coincides with the drop in connection.

Also make sure any wireless/ radio interference devices aren't placed near the router. I had an issue with a brand new Microwave recently which I only temporarily placed near the router before getting correct measurements for the brackets and when I was heating something on the microwave it immediately caused a connection drop-out. Moving it to the kitchen away from the router fixed this once I got the brackets measured to fit it in.

Now I know this may not be necessarily the same case. But there is this thing called REIN which can cause connection to drop out.

Also make sure to check your router up time. http://192.168.1.254/expert_user.html The expert user should show how long your router up time has lasted. If this Uptime is not maintained even after a disconnection then the problem is the router. If the Uptime continues to run then the fault is elsewhere.

Had that problem with my first Plusnet router and after a replacement the issue was fixed.

Telephone Number 01952****** on Exchange CUCKOO OAK is served by Cabinet 9

High Low High Low
VDSL Range A (Clean) 79.1 56.2 20 18.1 50.9 Available Available --
VDSL Range B (Impacted) 76.8 51.8 20 16.1 44 Available Available --

Observed Speeds

VDSL
Max Observed Downstream Speed (Mbps) 59.51
Max Upstream Observed Speed (Mbps) 17.05
Observed Date 2019-10-05

GEA Test:

Test Outcome Pass
Test Outcome Code GTC_FTTC_SERVICE_0000
Description GEA service test completed and no fault found .
Main Fault Location OK
Sync Status In Sync
Downstream Speed 59.4 Mbps
Upstream Speed 17.1 Mbps
Appointment Required N
Fault Report Advised N
NTE Power Status PowerOn
Voice Line Test Result Pass
Bridge Tap Not Detected
Radio Frequency Ingress Not Detected
Repetitive Electrical Impulse Noise Not Detected
Cross Talk Detected
Estimated Line Length In Metres 463.2
Upstream Rate Assessment Low
Downstream Rate Assessment Reasonable
Interference Pattern Not Detected
Service Impact No Impact Observed
Home Wiring Problem Not Detected
Downstream Policing Discard Rate 0.0
Customer Traffic Level Upstream and Downstream Traffic Detected
Technology VDSL
Current 15Min Bin Retrains 0
Last 15Min Bin Retrains 0
DP Type External
Profile Name 0.128M-80M Downstream 3dB, Retransmission Low - 0.128M-20M Upstream, Error Protection Off
Time Stamp 2019-09-19T16:30:00
Parameters MIN MAX AVG
Down Stream Line Rate 53.5 Mbps 59.5 Mbps 57.3 Mbps
Up Stream Line Rate 9.6 Mbps 17.4 Mbps 13.8 Mbps
Up Time 764.0 Sec 900.0 Sec 899.6 Sec
Retrains 0.0 2.0 0.0
Current and Last 15 Minute Bin Performance
Parameters Last Traffic Count(Upto 15 mins) Current Traffic Count(Upto 15 mins)
Start Time Stamp 2019-10-02T14:51:18Z 2019-10-02T15:06:18Z
Ingress Code Violation 2 3
Egress Code Violation 0 0
Errored Seconds 0 0
Severely Errored Seconds 0 0
Unavailable Seconds 0 0

Edited by adslmax (Tue 08-Oct-19 14:18:30)

There must be a fault in the line or somewhere! Do you know how long this has been persisting for? Was it recent or has it always been that way?

Downstream Speed 59.4 Mbps is at the bottom of your lowest speeds and this is not the kind of speed that is acceptable for a 3 dB noise margin. I would expect that to happen at 6 dB or 9 dB.

But at 3 dB I am expecting the speeds to be right up there in the 60s and 70s. Because imagine if now the noise margin were to be increased to 6 dB or 9 dB the speed will drop below 56.2 Mbps and may even drop below the Impacted level of 51.8 Mbps.

If the contract is already up with Plusnet, you could try changing provider. In case it is something to do with the router. If you're still in contract you could request a change of the router or if you have a spare router change it and see if this fixes the issue.

Replace the micro filter as well.

If none of this works or if this disconnection tendency always occurred under the 63 Mbps packages you may need to drop down to the 38 Mbps package. I know your parents probably won't want that, but it is highly likely that this will rectify the disconnection issue.

You can report it as a fault to Plusnet to send in an engineer. Also take a look at the rate of the disconnection and the timings. Does it happen at a particular moment in the time, or is it random? This could help you find clues on interference's.

Three is no 9dB noise margin target on FTTC.
The default is 6dB.
ECI cabinets are all stuck on 6dB at all times.
Huawei cabinets can lower the SNRM to 5, 4 or 3dB if a line is stable enough.

The line you're commenting on is within its estimates.
Everyone can't insist on getting the higher end of the estimates.

If/when you decide to place on FTTC order they will quote you a high and a low estimate and a minimum guarantee.
If the low estimate isn't good enough for you then don't order it.

My estimates climbed when the 3dB profiles were rolled out from a High/Clean of 40Mb up to 48Mb so the estimates already take in to account possible improvements by DLM.

The OP isn't complaining about low Speed but that DLM often changes between 3,4 and 5dB SNRM targets which initiates a resync.
This isn't my experience of DLM as it would always wait at least a few days before attempting to lower SNRM after it has increased it.

If the OP changes DLM policy/profile through Plusnet as advised their issues will likely go away.

Your over thinking and worrying too much about the stability and reliability of a technology millions use problem free everyday.

As previously mentioned my line is just over 1km long to the FTTC cabinet (1012m and 1024m quoted on separate line tests) and it runs perfectly stable on a 3dB SNRM target.
I get a very respectable 45Mb down 7.2Mb up at the moment.

If you order 40/10 you will get that easy with plenty SNRM to spare.

In all likelihood you'll sync at or near 80/20 if you go for that package.

In reply to a post by BLaZiNgSPEED:

In recent few years Openreach lowered the DLM down to 3dB which coincided with my daily internet disconnections. This is despite my line being EO.

With Sky this happened like 3-4 years ago. I had to call tech support, they sent a Sky Engineer back then and only gave me a new router. The problem did not solve.

It was only until I called again Sky and they manually set noise margin to 9dB and my disconnections stopped.

Openreach didn't introduce a 3 dB target 3-4 years ago.

Openreach DLM is nothing to do with any lines that aren't FTTC.

ADSL and VDSL are somewhat different things for many reasons - my own ADSL was unstable while the VDSL was fine.

I'm not sure of the relevance of any of this to the issue at hand.

Edited by CarlTSpeak (Tue 08-Oct-19 21:10:06)

In reply to a post by j0hn83:

Three is no 9dB noise margin target on FTTC.
The default is 6dB.
ECI cabinets are all stuck on 6dB at all times.
Huawei cabinets can lower the SNRM to 5, 4 or 3dB if a line is stable enough.

The OP isn't complaining about low Speed but that DLM often changes between 3,4 and 5dB SNRM targets which initiates a resync.
This isn't my experience of DLM as it would always wait at least a few days before attempting to lower SNRM after it has increased it.

As previously mentioned my line is just over 1km long to the FTTC cabinet (1012m and 1024m quoted on separate line tests) and it runs perfectly stable on a 3dB SNRM target.
I get a very respectable 45Mb down 7.2Mb up at the moment.

@j0hn83: I wasn't aware that on FTTC there's no 9dB noise margin target! I know I am probably worrying a little bit more than I should.

If 6dB is indeed the maximum cappable noise margin then I suppose the only way it will maintain stability is if the margin on FTTC does not drop down to 0dB. But it also depends on line quality and length. Each case is individual. I know you've told me in the past on these forums that you successfully achieve 45-55 Mbps on 1km line. But it is possible that you are fortunate to not have any issues with noise on the line!

Especially if we consider the length and location of the area. In a busy urban town/city with busy roads, noise traffic, industrialisation, neighbours that can cause REIN, the copper/aluminium line might not be stable. But in a rural area or less central towns and cities where there is large green fields the line is going to naturally be more stable.

The problem I had (it may be purely my experience) but on ADSL my noise margins at 9dB would drop down to 3dB. This can last anywhere between 10 minutes to 2 hours or so before the noise margin bounces back to 9dB. This has always been the case with Sky, Tiscali, Be Unlimited*, Plusnet, etc. Only under the 1Mbps package in 2005 my connection was stable.

Under ADSL my line will drop out with a 6dB profile! Because in my case there are 5-6dB points lost from observation and usually only in mornings. If the line holds to 1-3dB my line will be stable and the connection will remain in sync for at least 30-60 days at a time. But not always under 6dB my noise margin will drop only down to 1dB it sometimes completely goes to 0. But with 9dB my noise margin during a drop will at least not drop below 3dB.

If the OP changes DLM policy/profile through Plusnet as advised their issues will likely go away.

Your over thinking and worrying too much about the stability and reliability of a technology millions use problem free everyday.

This is why I cannot necessarily guarantee that the OP will have the line stable even under 6dB unless their noise margin only drops slightly and then bounces back to 6dB without it affecting the connection.

Millions of people don't have 1km copper lines under FTTC at least, this is why most people don't have problems! I never had problems in my other flat for 4 years where I lived in Shadwell connected to Stepney Green Exchange and that was only 0.3 miles to exchange and connection was always rock solid.

In my other property where I rent out in Shoreditch cabinet is only 32 meters to property no problem there. Of-course I'm going to see when I do order FTTC finally in January and hope my connection will not drop out with 3dB or 6dB. At least a large chunk of copper (over 600+ meters) will be reduced in my case.

Anyway, thank you for the reassurance, but I am still a little bit worried and I hope the OP solves his problem soon!

There are probably more serious issues than this facing us all. If you do have a need to worry and over-analyse things there might be better targets than an SNR margin.

Well said.

Updated: Engineer found no fault. SAying it was DLM trying to stable the line at 3dB and it moving around itself, nothing they can do about it. So, my parents has decided to downgraded to 40/10 instead of 80/20 and Plusnet offer them a goodwill gesture of having 40/10 unlimited fibre, line rental and anytime calls plan for just £20 a month for 12 months. (free of charge anytime calls plan for 12 month) so can't complaint.

In reply to a post by CarlTSpeak:

In reply to a post by BLaZiNgSPEED:

In recent few years Openreach lowered the DLM down to 3dB which coincided with my daily internet disconnections. This is despite my line being EO.

With Sky this happened like 3-4 years ago. I had to call tech support, they sent a Sky Engineer back then and only gave me a new router. The problem did not solve.

It was only until I called again Sky and they manually set noise margin to 9dB and my disconnections stopped.

Openreach didn't introduce a 3 dB target 3-4 years ago.

Openreach DLM is nothing to do with any lines that aren't FTTC.

ADSL and VDSL are somewhat different things for many reasons - my own ADSL was unstable while the VDSL was fine.

I'm not sure of the relevance of any of this to the issue at hand.

They didn�t introduce a 3dB default, but they introduced the possibility of a 3dB margin about 3 years ago in some cases. Why do you think they didn�t? I remember reading about it at the time.

But yes obviously only on DSLAMs controlled by Openreach, FTTC ones then.

Edited by deleted (Wed 09-Oct-19 19:16:55)

https://www.ispreview.co.uk/index.php/2016/11/speed-...

It was indeed being trialled on a small scale 3 years ago.

I didn't see any cases of sub 6dB lines till the trial was extended in early 2017. Though I say many who thought they were.
Full rollout began 20th March 2017.

I remember a very spirited debate at the time on the effect of lower target SNRM's on the reported max attainable rate

I argued you can use this to differentiate between lines on the trial and those that simply synced pre-crosstalk at a higher rate with a lower actual SNRM.

https://forums.thinkbroadband.com/fibre/t/4528246-op...

I'm still none the wiser on the effects of the SNRM target on the attainable rate on ADSL which obviously works in a different way.

WilliamGrimsley's line 1 of the the 1st I witnessed the 1dB incremental drops, with subsequent attainable increase, as we see in every line with XdB today.

I still frequently see users who randomly sync higher, with a current 3dB SNRM and assume it's a target SNRM set by DLM.
Still never seen DLM jump from 6dB to 3dB though, always in 1dB increments at least 24 hours apart.

I just read most of the trial thread I linked above.

Whatever happened to WWWombat? A great source of knowledge!

I think his solution is banding.

If I remember right when I read one of BT sin documents years ago in the early FTTC days was something in there that isps can request a line to be banded. This would artificially keep the SNRM high providing the capability of the line doesnt significantly regress.

In reply to a post by Chrysalis:

I think his solution is banding.

If I remember right when I read one of BT sin documents years ago in the early FTTC days was something in there that isps can request a line to be banded. This would artificially keep the SNRM high providing the capability of the line doesnt significantly regress.

Not in any SIN I've ever read. Confident that can't be done.

ISP's can request banding on a line but have no way to remove it or increase it? That would be silly.

The FTTC DLM is entirely automated. No ISP has any control of any specific settings other than to choose the policy (Speed, Standard or Stable).

Icaras is describing something very out of the ordinary, arranged for him (an OpenReach engineer) by the OpenReach DCoE for a problem line.

No way ISP's can do this kind of thing.
An ISP like AAISP would have been on this immediately if fixed profiles were possible.

To add to my comment to Icaras a few days ago

In reply to a post by j0hn83:

There is a 4th DLM profile often overlooked or unknown to many.
This is named "Custom" and AIUI can be set to a fixed setting like you suggest.
Documentation for ISP's tells them the Custom DLM profile should only be used on test lines.

This was introduced as a possibility in August 2018

https://www.openreach.co.uk/orpg/home/updates/briefi...

Where a CP utilises dedicated test lines the use of DLM may be inappropriate. We are therefore allowing CPs to request that DLM is deactivated and a fixed profile is placed on test lines.

I can't see why they would brief ISP's that they can now fix profiles on test lines if it was always possible on customer lines.

I'd be amazed if Icaras's example wasn't using the method described above which is supposed to be limited to test lines.

In reply to a post by j0hn83:

Still never seen DLM jump from 6dB to 3dB though, always in 1dB increments at least 24 hours apart.

We moved to IDNet on 11/09/18 and went to the no G.INP 6dB regime and a sync speed of 62459. On 13/09/18 G.INP was enabled and our sync went up to 72233. We had an uplift to on 20/09/18 to 75314 but my records don't show the SNR. The router was then powered down from 22/09/18 to 29/09/18 when it reconnected at 74917 - again no record of the SNR. We then saw a silent re-connect on 10/10/18 when the sync speed jumped to 79230 and my notes show a new SNR of ~3dB.

That looks a little different to a 6 > 5 > 4 > 3 progression but I haven't got any evidence to prove the case.

There is things that isp's miss tho. Also asking for manual banding on lines complicates things, its cheaper for an isp to not have that as part of their policy.

But with all that said I dont know if it still applies now, the sin document I read was in the first 1-2 years of FTTC rollout, and since those days a lot of things have changed.

In reply to a post by j0hn83:

In reply to a post by Chrysalis:

I think his solution is banding.

If I remember right when I read one of BT sin documents years ago in the early FTTC days was something in there that isps can request a line to be banded. This would artificially keep the SNRM high providing the capability of the line doesnt significantly regress.

Not in any SIN I've ever read. Confident that can't be done.

ISP's can request banding on a line but have no way to remove it or increase it? That would be silly.

The FTTC DLM is entirely automated. No ISP has any control of any specific settings other than to choose the policy (Speed, Standard or Stable).

Icaras is describing something very out of the ordinary, arranged for him (an OpenReach engineer) by the OpenReach DCoE for a problem line.

I was the Openreach engineer! I wasn�t the customer.

Isn't that what I said?

Icaras is describing something very out of the ordinary, arranged for him (an OpenReach engineer) by the OpenReach DCoE for a problem line.

Apologies! I read your post as �by an Openreach engineer�.

In reply to a post by Icaras:

They didn�t introduce a 3dB default, but they introduced the possibility of a 3dB margin about 3 years ago in some cases. Why do you think they didn�t? I remember reading about it at the time.

I stand corrected. Time flies.