Interleaving, banding/profile

[#1]

tl;dr - How do I request my line get (and keep) an increased target SNR margin of 12 dBm and also try the more stable connection with Fast Path (ie turn off interleaving)?

The story:

I have been managing my connection from my router for years now (all with plusnet).

By default the line will happily sync at 11+Mb/s but will regularly (almost daily I think... I forget) disconnect. I left it default like this for months, but DLM obviously considered the disconnects to be normal. (fwiw - I'm pretty sure this is external REIN... but it's too much hassle to progress and could just be crosstalk).

This was not acceptable for me... so, long ago I bought an old modem/router that allows me to tweak target SNR margins (at the expense of sync rate) and even allows me to specify ADSL 2 rather than ADSL 2+ (this appears to be more stable with very similar sync rates).

This means I can happily zip along with a rock solid 6-7Mb/s and 12ish dBm (obviously, this reduces over the life of the connection) snr margin for months at a time.

The problem:

Whenever there is a power outage/surge/blip (surprisingly regular where I live) the modem resets (and loses my tweaks) and defaults to a much lower target SNR (6 I think - I forget) so I must intervene to ensure stability - not ideal.

I would also like to see if I can reduce my latency a bit by removing interleaving. Originally interleaving was enabled at my request to attempt to make my connection more stable, but with an SNR margin of 12 dBm I see very few errors so I'm not sure it's still required. I know I'm probably only looking at 7-8ms, but every little counts when gaming - apparently!

My priority is always stability, I'm not too concerned about sync rates (although I would begin to struggle if it got much lower).

I don't want to cause much bother though... this is all just a stop gap until plusnet will offer me FTTP (there is a lovely bit of fibre right outside my gate!) as my cabinet is not getting fibre.

So, what do I need to do to action any of this?

[#2]

Thanks for your post @Anywho

I've placed an order to turn off interleaving and set a DLM threshold to try to stop it from making positive changes like reduce the SNRM target. This should take effect from tomorrow.

I've also emailed our suppliers to set the SNRM target to 12dB which should hopefully be done within a few days. Normally we can do this ourselves, but for some reason the change isn't going through. 

On the subject of FTTP, if you move to BT or EE for this we'll be happy to waive any termination fees though I appreciate you may want to stay with us. I can't say when we'll offer it but there's talk on the forums that it should be soon... If you do choose to move away I'd recommend calling our Customer Options Team on 0800 013 2632 to discuss and arrange.

Let me know how it goes.

[#3]

Just to follow up, the order I've placed is taking a little longer to complete than I thought but it should go through tomorrow.

[#4]

Thanks for doing this for me without any fuss.

Quick question... do you know if/when the DLM decides to apply interleaving (is there a CRC/Errored Seconds per period threshold?).

Don't worry about how long it takes... I'm still able to use it and I have seen a good 20ms improvement in latency... from around 45ms down to around 25ms - which is a huge percentage but I doubt my reaction times will do it justice!

I am seeing around 10 CRC errors per 15 minute period (with 14dB snrm) but I have not yet noticed the effects of these errors. If frames are skipping I'm not noticing!

I may increase the snrm some more and I assume I can just request it be raised even higher in the future? I will also play around with restricting it to ADSL2.

But I'm not going to fiddle with it until the snrm change has been done your end.

Thanks again... I really appreciate how quick and easy this was.

[#5]

Thanks for getting back to me @Anywho 

No problem at all

---

@Anywho wrote:

Quick question... do you know if/when the DLM decides to apply interleaving (is there a CRC/Errored Seconds per period threshold?).

---

Yeah there's a threshold and the one I've set which has completed today, along with turning interleaving off, is that DLM won't shouldn't make any positive changes unless there are zero errors. 

The Kitz website Here could likely explain it better than I can. 

I hadn't received a response from our suppliers yet about setting the SNRM target to 12dB but I've managed to do it so the full profile is "WBC 160K - 24M No delay (INP 0) 12dB Downstream, UC No delay (INP 0) 6dB Upstream (ADSL2+)". 

INP 0 means interleaving is off, INP 1 is interleaving in a low state and INP 2 interleaving in a high state. 

In theory we can increase the SNRM target to the highest of 15dB but I've never tried it so unsure if it works. I'm happy to give it a go though if you'd want as there's always a first time for everything 

How do things look your side now?

[#6]

Welp...

I think I will give a few days as things seemed to have all happened together;

- at 3.30am BT seem to have done the SNRM change and by this 9am morning my SNRM had dropped to around 10ish. Sync speed was a whopping 8+ Mbs!! CRC errors were now looking slightly worse and browsing was showing signs of problems... but this could all have been coincidental - too short of a timeframe to be sure.

- at 11:20am the router reported massive CRC errors and a resync occurred... resulting in SNRM of around 20!! Sync speed was around 5500 kbps. I assumed this was due to the constant errors, but it was probably just your changes!?

- I stupidly intervened almost immediately (SNRM of 20 is just silly!!)... and forced my router into ADSL2 mode. Sync speed of 6500 kbs and SNRM of 14. No CRC errors - them higher tones/frequencies are just no good to me at all!! I think ADSL2 with SNRM of 12 will be fine for me... I might have to get a modem that will remember my changes through power recycles.

So many reboots in so short a space of time are not going to have helped I'm sure.

I'll leave it for a bit and get back to you.

One observation I have made already though is that throughout this process I have been running speedtests (something I never normally do any more) and they always seem to return a result of 5.5 Mbps (all wired) - regardless of sync speed... which smells a lot like a cap!

I can see the data you posted suggesting no cap though... so I'm a bit confused but not that concerned right now... if you can think of anything though feel free to have a poke around!!

I know that before any of this when I have watched large downloads various download clients have reported speeds matching my sync rate... but I've never actually timed a download. So if there is a cap I would assume it is new?

[#7]

Hello @Anywho

Thanks a lot for reaching out, and I'm sorry to see that you're still experiencing issues on the line, despite the changes that @Gandalf has made to your connection profile. Tests on the line are still showing frequent errors, and I can see that the line has dropped out quite a few times today. It's still too soon to see what real impact the changes to the DLM profile will make just yet, so I'd hang fire for a few days for now and monitor your connection.

As he's already pointed out, we can always try a higher downstream SNRM if the problem continues.

Speeds are looking good for now though, coming through at 6.5Mbps, which is within your estimated speed range.

KBD

xDSL Status Check
Circuit ID:	CBUK90557799	Service ID:
Telephone NO.:	NA	Test Executed On:	12-11-2021 15:21:45

xDSL Status Test Summary
Sync Status:		Circuit In Sync
General Information
NTE Status:		NTE Power Status:	PowerOn	Bypass Status:

	Upstream DSL Link Information	Downstream DSL Link Information
Loop Loss:	20.6	35.5
SNR Margin:	6.5	14.1
Errored Seconds:	0	0
HEC Errors:	0
Cell Count:	1293677	3277361
Speed:	1127	6519

Maximum Stable Rate (KBPS):	6816	Fault Threshold Rate (KBPS):	5452
Mean Time Between Retrains (Seconds):	16145	Mean Time Between Errors Upstream (Seconds):	1345
Indicative Line Quality:	A	Mean Time Between Errors Downstream (Seconds):	317
Custom Thresholds
MTBR_RED:	MTBE_RED:
MTBR_GREEN:	MTBE_GREEN:

[#8]

Yes, I'm going to leave it a while - I dont want DLM to turn interleaving on again due to all the retraining!!

I was a bit worried when the internet went down about 15:23... but now I see you were testing the line... so no problem.

You should notice far fewer errors on my line when it is connected as ADSL2 (ie upto 1.1Mhz frequencies)... the errors start if I try and use any of the higher frequencies of ADSL2+ (ie 1.1Mhz - 2.2Mhz).

In a few days I should be able to lower my SNRM back down to 12 (on ADSL2) without seeing regular errors... the current  synced margin of 14 was just me playing safe.

It's still curious that all my speed tests are maxing out at 5.5Mbps (which matches the fault threshold rate!).

I tried using BTW speed test additional diagnostics... but it fails on my telephone number.

Can you provide my Broadband Service ID (BBEU) so that I can try and enter that? I tried using the circuit ID but that fails too!!

Thanks for all the help on this... all the time I have 6+ Mbps error free connection I'm contented! The latency is a nice bonus.

[#9]

Fair enough @Anywho

Reach out in a few days then and let us know whether you're still experiencing any issues, we'll be happy to look into them for you.

I'll send you a PM with your BBEU now.

[#10]

tl;dr Could the few errors that I get be causing the download limit I am seeing. If so, then please re-enable downstream interleaving at its lowest possible level. Also, please revert my SNRM/profile back to default/standard/aggressive if it is possible that this is causing my issue?

Okies... it's important to understand that I am not unhappy with my current download speeds of 5.5 Mbps (although in this new media age it is right on the limit of serviceable). An extra 1-2 Mbps is not going to be earth shattering at current levels - but would certainly provide some headroom.

That said, I'm curious to understand why my download speeds now appear to be capped at 5.5 Mbps. I'm not sure when the cap arrived (I think in the last few weeks, maybe even with the fast path/SNRM/profile change last week - but I can't be 100% certain). Perhaps it always existed and I didn't notice - but I'm fairly certain it's new.

This is not a problem that deserves any "man hours" being spent on it, but does anyone have a clue about why my downloads are maxing out at around 5.5 Mbps?

It doesn't appear to matter what my sync speeds are (anything from 6.5 - 11+ Mbps) various speed testing sites (including BTw) report 5.5 Mbps download.

Perhaps Plusnet/BT have a cap intended to prevent people running into trouble by downloading too fast?

If there are any settings intended for the users protection I would prefer them all to be turned off. If you can turn off the DLM, then turn it off too... I will manage my line just fine (with the exception of interleaving)!

If having the SNRM set to 12dB is the problem then remove that setting too - revert back to the normal/default aggressive/standard BT setting... I will manage my margins (I have been for years).

I did notice that last weeks change increased my Upstream bitrate. It was ALWAYS 888 kbps. The new rate of 1100+ kbps is most welcome... does that provide any clues?

I want a situation where I have the maximum control possible (I'm not a control freak honest - I just trust my judgement more than some generic software in this instance) with as little outside influence as possible.

You can see that I am not some speed freak... I have been operating my connection at between 60-80% RCO for many, many years. I have a reasonable grasp of the relationship between speed and stability on ADSL.

As a side note... the BTw additional diagnostics are still giving me an error - even with the BBEU number provided (thanks for that btw!).

[#11]

Hello @Anywho

Thanks a lot for getting back to us.

Yes, I'm going to leave it a while - I dont want DLM to turn interleaving on again due to all the retraining!

I wouldn't worry about this, @Gandalf has customised the DLM settings on your line so that it does not turn interleaving on regardless of how many retrains are seen.

Testing your line this afternoon definitely shows some improvements. The mean time between errors has decreased slightly, which initially had me worried, but I then took a look at the mean time between retrains, which looks a lot better than previously. I'll attach my KBD to this post so you can have a look.

You'll also see that the downstream SNR has decreased to 11.6, and your download speed has increased to 8.19Mbps. You are connected via L2TP though, which means your download speed is influenced by the connection profile on our end, which was capping it at 7.2Mbps when checking today.

I've increased this on our end, so you should see a slight bump in your download speed.

KBD

xDSL Status Check
Circuit ID:	CBUK90557799	Service ID:
Telephone NO.:	NA	Test Executed On:	15-11-2021 16:52:04

xDSL Status Test Summary
Sync Status:		Circuit In Sync
General Information
NTE Status:		NTE Power Status:	PowerOn	Bypass Status:

	Upstream DSL Link Information	Downstream DSL Link Information
Loop Loss:	20.6	38.5
SNR Margin:	6.0	11.6
Errored Seconds:	0	2
HEC Errors:	0
Cell Count:	1946849	5523660
Speed:	1127	8199

Maximum Stable Rate (KBPS):	6816	Fault Threshold Rate (KBPS):	5452
Mean Time Between Retrains (Seconds):	86400	Mean Time Between Errors Upstream (Seconds):	1449
Indicative Line Quality:	A	Mean Time Between Errors Downstream (Seconds):	203
Custom Thresholds
MTBR_RED:	MTBE_RED:
MTBR_GREEN:	MTBE_GREEN:

In regards to changing the DLM profile again, I'd edge on the side of caution of rocking the boat too much here, however the changes that @Gandalf has already made have been done to increase your line speed as much as possible. We can't turn the SNR off, but we'd be able to turn the target SNRM down incremently to see how your connection performs. At this stage, I'd be able to adjust it to 6dB?

Let me know if you'd be happy with that and I'll get it done.

[#12]

tl;dr - Thanks for the cap increase - it helps. Please DO NOT EVER reduce my target SNRM unless this parameter effects some other user parameter (ie my cap. Obviously, sync speed is a function of SNRM). Could you raise my Plusnet connection profile cap to something I can never achieve so that I can be sure it is not getting in the way, say 12Mbps - I am assuming bRAS will always restrict me to 88.2% of sync rate anyway.

The long story...

Perhaps I was unclear in my previous post, but you certainly have not understood me if you think I was asking for my SNRM to be adjusted.

I can change my SNRM at will - this has never been a problem.

I have always been able to sync at anything upto 11+ Mbps (inversely proportional to whatever SNRM I choose, obviously). Synchronisation is not the issue.

The problem is...

I have noticed recently that my actual throughput (download speed, or whatever it may be called... my actual utilisation) is capped regardless of sync speed... I am not getting my 88.2% of sync speed or whatever WBC21 says I should get.

I did not notice this until after I asked for changes - and I think that is when it started but I would be lying if I said that I was 100% certain.

What is the logic behind Plusnet profiling my connection as well as BTw bRAS? This seems to be asking for trouble.

Since I can easily sync at 11+ Mbps if I choose, perhaps Plusnet could increase the current CAP to something more like 11 Mbps? I will only ever achieve a download speed of 88.2% of my sync speed anyway... so this artificial cap seems pointless?

At the moment I cannot see my bRAS profile since the BT speed tester keeps getting an error when I ask for additional diagnostics. Maybe that is sticky too?

You say you have increased my cap, but you don't say what to? Is it a secret? I'm guessing you have capped me at 7.5 Mbps?

It does appear that whatever you did has improved my throughput situation (thankyou btw!!)... but the new download speed of 6.61 Mbps is not 88.2% of the 7.2 Mbps cap nor is it 88.2% of my current sync rate of 8011 Kbps - its in the middle!

I accept it is close enough to not matter (or be an environmental/load discrepancy).

Interestingly, 7.2 is roughly 88.2% of the download speed (I think you mean sync speed) you report as being 8.19.

As for turning SNR off... I'm guessing that is just a typo and you meant you can't turn the DLM off? Shame!

Please DO NOT change my target SNRM. If I ever request a change to this in the future it will be to raise it to 15 dBm for improved power-on stability. I will continue to manage this myself.

PS - I have recently manually re-sycned a couple of times as ADSL2+ was getting very noisy!

[#13]

If the connection profile at our end was 7.2mbps then this is correct for a sync speed of 8.2mbps if we base things on that the bRAS is 88.2%, because this profile should match the bRAS. Based on this you likely won't get a throughput of 88.2% of your sync speed as that's not realistic, because there are overheads of a connection.

While we can manually raise the connection profile up to a maximum of 21mbps for your package, this won't affect the bRAS profile and therefore if the bRAS profile is at 7.2mbps this wouldn't have improved your download speed. I'm glad though to see your throughput has increased following the increase Adam's done.

I'm not in the office to check but it absolutely won't be a secret. 

Why do you think though you should see higher than 7.5mbps for a sync speed of 8.2mbps? There's more information here https://kitz.co.uk/adsl/IPprofile.htm about the bRAS and overheads. The 88.2% percentage only applies to the bRAS profile of the sync speed, not to your throughput of the bRAS profile.

Also, we can't turn off DLM so even though I've made a modification to try to stop it from decreasing the SNRM target, ultimately we can't guarantee the automated software at the exchange may not change this. 

[#14]

Now I'm in the office.

I can see Adam changed the connection profile to the max at 21mbps, but last night we received a delta report update from suppliers to automatically change it to 5.6mbps matching the bRAS profile at that time.

This though is something you can see on your end by going to the Broadband tab in your account. 

[#15]

There seems to be much confusion here - probably because I write too much!

Is the Plusnet IP Profile additional to the BT IP Profile (bRAS profile?)? 

How long does the Plusnet profile take to respond to a change in sync?

Does my line have a banded profile preventing higher sync rates? (This is particularly unnecessary as I only ever sync at a max of 8ish Mbps despite being able to sync at 11+ Mbps@ 6dB SNRM prior to these changes)

Do you have any idea why I cannot get the additional diagnostics from BT (which I believe would show my BT IP profile)?

I'm just going to keep periodically tweaking for now - but I think the line is just too noisy in bursts especially in the evenings (crosstalk?)... so may well need interleaving back on in future to spread the data out more. Will this be a problem if I need it (not yet, just checking)?

Thanks for all your time and effort on this.