Speed capped - out of the blue... again!

[#1]

I say again... it hasn't done it for over 2 years... but still!

Thursday 12 December 2024 around 05.30 my connection was brought down and reset remotely (ie not by me or my equipment). Prior to this reset my stats show no errors or errored seconds since around 22:30 the night before. My connection/synch was just under 10Mb/s with SNRM of around 10dB - I manage my connection to try to maintain around 10dB SNRM. The connection had been up for 4 days with quite normal looking errors (I think I was still trying to recover from a power outage that came at an inconvenient/noisy time of the day... usually the connection stays up for weeks at a time until I decide it's time to hard reset the modem).

When the connection returned after the remote reset it was sat at 6.6Mb/s with SNRM of 6dB (max line synch reported at 12+ Mb/s).

I tried a reset from my end at around 10.30 with no improvement. So I left it for the rest of the day. I got barely any errors.

This morning 13 December I powered down the modem around 10:00 and left it a few minutes. When I powered up, the connection returned with the same 6.6Mb/s (max 11.4Mb/s), SNRM 6.9dB.

Can I get a reset and removal of this cap please? The line has been fine (well, relatively... its a long, bad line!).

Thanks

[#2]

@Anywho What product and what router are you on?

[#3]

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@Anywho wrote:

My connection/synch was just under 10Mb/s with SNRM of around 10dB - I manage my connection to try to maintain around 10dB SNRM.

... I think I was still trying to recover from a power outage that came at an inconvenient/noisy time of the day... 

When the connection returned after the remote reset it was sat at 6.6Mb/s with SNRM of 6dB (max line synch reported at 12+ Mb/s).

I tried a reset from my end at around 10.30 with no improvement. So I left it for the rest of the day. I got barely any errors.

This morning 13 December I powered down the modem around 10:00 and left it a few minutes. When I powered up, the connection returned with the same 6.6Mb/s (max 11.4Mb/s), SNRM 6.9dB.

Can I get a reset and removal of this cap please? The line has been fine (well, relatively... its a long, bad line!).

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Sounds like you are not using a Plusnet supplier router and might be gaming the SNRM / DLM process - why?

There is zero merit in raising the SNRM (it simply reduces the sync speed) if the line can maintain a stable connection at 6dB or below.  There is limited merit in running with a 'gamed' SNRM in situations where there is significant intermittent REIN which you cannot manage out of your environment.  However, if it is that bad, the DLM will do that for you.

What noise are you referring to?  Audible noise or a known source of RFI?  If the latter, what has been done to locate it and eliminate it?

What do you mean by a "reset"?  Simply power cycling the router or something else?

What "cap" are you referring to?  A target SNRM of 6dB is the normal DLM setting; if its is higher, the sync will be slower; if the line is extremely stable, it might drop to 3dB in which case the sync will be faster.  There is an inverse relationship between TARGET SNRM (TS) and sync speed: if TS goes up, the sync speed will be lower.

It is a long bad line - how long?  Had any bad weather recently, high winds?  Is it possible that the marginal line has degraded further and what is really required is a fault report and line test?

Sight of your router stats would be helpful please.

[#4]

I appreciate the interest in my post, but I require a DLM reset to return my line to the same state I have been managing it in for years.

This used to be the best place to get Plusnet support - if this is no longer the case then please do let me know.

I am on ADSL2+ Unlimited Broadband, currently running a HH5a with OpenWRT (without any SNRM tweaks right now). But the result would be the same with any of the ADSL modems that I own, since this banding/cap has been placed on the line.

FYI I have several Plusnet supplied modems/routers that also allow me to tweak SNRM (old ones that work fine like the old Netgear DG834 for one - I have never been sent a newer one than that!! I had to buy my own HH5a!)... I just prefer to use the HH5a with Openwrt because the tweaks persist through a power cycle (and for other reasons like SQM).

I fully understand the benefits and pitfalls of tweaking the SNRM... no part of my post implied that I needed any help with any of this - I only mentioned it for completeness and perhaps to demonstrate that I know my way around a modem. DLM will happily manage my line down to an unusable level if I let it - and it has done so previously. If you would like to check my line history you will see I can manage this line quite happily at 8-9 Mbps with perfectly acceptable levels of errors and with no excess latency from BufferBloat. If your line has zero errors then you are leaving bandwidth on the table.

"There is an inverse relationship between TARGET SNRM (TS) and sync speed: if TS goes up, the sync speed will be lower"

But I explained my synch speed dropped AND my SNRM dropped (I am less interested in the target SNRM and more interested in the actual SNRM at a given time)? What does that tell you?

The reference to noise was merely part of a small explanation as to why there had been such a recent reset. It was in reference to the times of day when my line has reduced SNRM - I believe all ADSL lines experience a change in SNRM during a 24 hour period. I have learned that if I reset my line at a quieter time of day (21:00 - 22:00) and target a SNRM of 10dB my line will cope with the varying conditions just fine with an acceptable number of errors (usually not so many errors that DLM decides to increase my margins and reduce my bandwidth - or band my line).

So the noise I'm referring to is the same noise referenced by the noise denoted by "N" in "SNRM".

The resynch from 4 days earlier was related to a power outage. The power was lost at around 4am a few days before and when it returned it bounced a couple of times. When this happens I tend to wait a few days and then resynch at my usual time of day. Yes, I need to get this modem on a UPS - its awkward!

In the context of this post a reset is a complete resynch of the line. If I just say "reset" it usually means a soft resynch (usually an OpenWRT system reboot, but sometimes a stop/start of the modem service) without any power cycle of the whole device/router.

The "cap" is the DLM banding or whatever that has been applied to my line - I forget the correct terminology. The exact same bandwidth cap was imposed just over 2 years ago for no apparent reason... exactly 6.6 Mbps. And whilst 6dB might be a fine target for a nice new short line it would destroy my connection without this lowly DLM cap. Even with the cap, if I don't intervene here eventually the line will degrade to become unusable - ask me how I know.

It is entirely possible that the line has degraded further or a fault developed/worsened (I think a line test showed a fault on my line back at the end(!?) of COVID - but because my house has more than 1 vulnerable person I did not want an engineer to visit... the connection was functional enough). I never revisited this since the line performance was adequate.

Line attenuation still shows 40dB - this has not changed in 12 years.

I'm uncertain what stats you would need to prove that my line has been banded/capped? The first picture is a snapshot of the DSL line. The second is the line stats that I collected from the Thursday morning showing no errors at the time of the remote resynch (you can see the SNRM drop, the synch speed/bandwidth drop and of course the max bandwidth increase).

I think some of these errors are misnamed/mislabeled.

In order to get acceptable performance in the home (ie 2 standard definition streams and some internet browsing simultaneously) I like to synch at around 8Mbps or more with a SNRM target of around 10.5dB. This gives me some headroom to run SQM Cake at around 7Mbps and eliminate any unnecessary latency (BufferBloat).

This has been working fine for 2+ years - which is why I haven't been here whining until now!!

Again, I'm grateful for the interest, but I really need Plusnet to intervene here.

[#5]

BTW - I just started putting my lights up today (Humbug!)... so it wasn't that either!

[#6]

Something is very amiss here and I do not think this is speed banding (at least alone) - if it were you would be seeing a far higher SNRM.

A clean line having 40dB attenuation (circa 2.8kms) should deliver around 10mbps at a SNRM of 6dB.  Remember that SNRM is not an absolute metric, it is a margin over the background noise.

I would suspect that your line has deteriorated markedly, so that to attain the margin over the noise, the line needs to run much slower than normal.

Yes, ADSL lines do suffer NIGHT TIME interference from continental radio and the evening time slot you mention is the noisiest for such interference.  At worst (on a clean line) that is unlikely to deliver more than a -2dB variation. By the sounds of things, your variation is at least twice that and such would typically come to local equipment.  There was a recent case of such arising from GU10 kitchen light fittings.  That too was pursued as a DLM reset request initially.

If you wanted to reset your line for speed (at the risk of stability) your should do it at midday.

Have you checked the line for noise (dial17070 option 2)?

Have you considered running routerstats to plot the SNRM variability?

Have you invoked any of the fault reporting mechanisms?  Generally if the DLM has kicked in, to manage the line's stability, then there is little point seeking a reset of that intervention until the reason for the intervention has been identified and rectified.

@Marsh / @MatthewWheeler - any suggestions please?

[#7]

Hmmm - certainly some things there for me to think about.

FYI - I never sync lower than 9dB SNRM (sometimes DLM might kick in and move me from a 12dB target to 15dB target or vice versa messing with my offsets, but I always correct it with my tweaks that you dislike so much!) because I would get disconnects. And I always sync faster than 7Mbps usually 8-10. I have no real evidence to show though.

You may get the impression that I'm constantly tweaking, but the truth is I look at the stats every couple of weeks and just resynch if I feel like it and if it's convenient. Honest!! It can get fiddly when the electric bounces up and down, cos DLM gets upset... if I'm around then I just power down the modem when the power goes off and wait for it to return properly (same kind of problem with the pond pumps... but I digress).

The last stats that I screen dumped prior to this problem is from the week up to 13 May 2022 - the end of the last issue: Shows 8.6Mbps@10.8dB (though it does show fewer errors).

And before this latest "intervention" I was running at almost 10mbps@10dB - I had noticed my line stats had been improving lately, I just figured it was because everyone was on fibre and my cabinet was empty (no FTTC in my cab)!! (not the 40dB Line attenuation... that never changes).

The line was in use until midnight at least, with no errors after 22:30.

I've been mad busy the last few days, and I did not collect all of the stats before power cycling the modem... but I did take a copy of the last 24 hours (it doesnt have the errored seconds though).

The 7 day data for this event in my previous post makes it look like the  the datarates and SNR drops were gradual (prolly something to do with averaging). But the 24 hour data (below) shows it to be a single event - I'm sure Plusnets stats will show it as a single event as well?

This shows the 4 days up time, then a drop and a Last Uptime of 0.2 days (or 4.8 hours). Sadly it does not record the number of resynchs but I'm certain I checked the live stats and saw only 1 loss of signal for the whole 4+ days.

The synch speed and SNR changes look more precise/singular here (ie 1 event).

It does show that I was synching right on the limit of my lines capacity at 10dB and it shows a lot of errors (relative to what I usually see) over the busy evening period... I'm now thinking this was my fault for not leaving enough headroom. I probably intended to keep a closer eye on it - but life happens!

The resynch (that I initiated) from 4 days before this graph was done with a -2.0 Target SNRM. This implies DLM was targeting 12dB... why would it jump straight to banding without targeting 15dB first?

I haven't yet done any of the diagnostics you suggest.

I will definitely check the Quiet Line or whatever... I did introduce an extension to a telephone socket in the Kitchen a couple weeks back. But that socket doesn't carry digital/broadband (none of them do except the modem one!) so should not matter.

I may use routerstats again (although I think I had issues last time I tried on this HH5a, not sure. It worked a treat on the old Netgear) but OpenWRT is already recording this information so it is not a priority.

The GU10 bulb is a new one on me. I have a few of them, and I think a couple of them are real cheap and nasty too. They are rarely on, but I will keep it in mind.

If DLM was as conscientious about removing banding as it is about applying it then I would just wait it out... but I seem to remember that DLM will never remove banding once it is applied.

In the past Plusnet had no problem with requesting a DLM reset... has this all changed now?

Thanks again btw.

[#8]

Ah telephone extensions … that’s a whole challenging discipline in its own right. They might not “carry” the digital signal as you put it, except if they are connected to the filtered side of a faceplate. Even then if they are star wired with other extensions … there can be unwanted complications. Is the ring circuit connected?