Fibre synch speed - lower than hoped for

[#1]

Hi
First a bit of background to set the context of my request for a GEA test:

My VDSL service was originally provide as 80/20 throttled to 40/20.
My synch speeds were until mid April around >70mbps down and 20mbps up.
The downstream synch speed was with the help of G.INP and a 3 dB margin.

This was modified to 55/10 synch speeds in mid April, which was easily achieved.
I was tempted to upgrade to Fibre Extra two weeks ago as PN has/had a promotional offer.

Since upgrading to 80/20 my upstream speed as returned to 20mbps but downstream has stubbornly stuck to 54mbps,
with interleaving, a 6 dB margin and no sign of G.INP.

Can I please request a GEA test to see if the line is banded etc?

Regards

Richard

[#2]

Hi @RichardB

Thanks for getting in touch.

I've checked for banding on this one and there's nothing obvious - everything is as it should be in terms of the speed profile etc.

Could you raise a fault here and I'll ask our suppliers to take a look for you?

Best wishes

Dave

[#3]

Hi @RandallFlagg 

Fault raised, ticket ID #190139460.

Regards

Richard

[#4]

@RichardB , @RandallFlagg 

Out of interest are you on a fixed IP address?

The reason I ask is because unless things have changed the fixed addresses use the old Plusnet servers. On this system the Plusnet profile works and needs to be raised. I understand that this is not the case on the new system.

This fact has been overlooked by Plusnet in the past on my connection where their profile was left.at 55Mbps with the same result.

[#5]

Hi @Baldrick1 

Yes I am on a static IP but my issue relates to my downstream synch speed and not throughput.

My download synch is 55194 kbps with a noise margin of 6.3 dB, an interleave depth of 1081 and 3 errored seconds in the last 24 hours.

Whereas my upstream is 20000 kbps with a noise margin of 6.2 dB, an interleave depth of 1 and 180 errored seconds in the last 24 hours.

These figures are typical values since I transferred to fibre extra, and I cannot understand why DLM has not tried to reduce the downstream interleaving...

When my line appeared to be reset a year or so ago (I assume as a transfer to the "new" PN network), DLM acted after two days and activated G.INP with an increase in sych speed of approx 10mbps.

Then progressively reduced the SNR margin to 3 dB, each step increasing the synch speed by approx 3 mbps. 

Regards

Richard

[#6]

Hi Richard,

I'm sorry to see your downstream speeds haven't increased by much.

I can see your order to fibre extra completed on the 29/04/2019. Since then the connection profile on your account has been set to 74000kbps and above, although that won't be making any difference anyway as your sync rate is at 55.2mbps.

Here's a copy of our testing:

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	55.2 Mbps
Upstream Speed	20.0 Mbps
Appointment Required	N
Fault Report Advised	N
NTE Power Status	PowerOn
Voice Line Test Result	Pass
Bridge Tap	Not Detected
Repetitive Electrical Impulse Noise	Not Detected
Estimated Line Length In Metres	534.9
Upstream Rate Assessment	Very Good
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
Profile Name	0.128M-80M Downstream, Interleaving Low - 0.128M-20M Upstream, Error Protection Off
Time Stamp	2019-05-01T11:45:00

Parameters	MIN	MAX	AVG
Down Stream Line Rate	54.6 Mbps	55.1 Mbps	54.8 Mbps
Up Stream Line Rate	19.9 Mbps	20.0 Mbps	19.9 Mbps
Up Time	842.0 Sec	900.0 Sec	899.9 Sec
Retrains	0.0	1.0	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	2019-05-14T10:17:31Z	2019-05-14T10:32:31Z
Ingress Code Violation	5	2
Egress Code Violation	0	0
Errored Seconds	0	0
Severely Errored Seconds	0	0
Unavailable Seconds	0	0

As there's no banding or any other issues showing and your line speeds are within estimates of between 50.5mbps to 73/5mbps, our suppliers likely wouldn't accept this as a fault unfortunately.

Downstream Line Rate(Mbps)		Upstream Line Rate(Mbps)
High	Low	High	Low
73.5	50.5	20	14.2

I'd recommend doing some troubleshooting next if you haven't already by plugging your router into the test socket as explained here: https://community.plus.net/t5/Library/Testing-From-The-Master-Socket/ba-p/1322242

As a side note and this won't be affecting your speeds at all but it doesn't look like you've been moved to the Dedicated network as you're still provisioned on Shared routing via L2TP although you'd route that way with a static IP regardless.

[#7]

Hi @Gandalf,

Thank you for posting the GEA test results and confirming the expected line speed rate limits from the ADSL availability checker.

I understand that OpenReach would not accept that there is a line fault.
I also do not believe there is a line fault.
The issue is, to me, the inexplicable DLM behaviour, or rather lack of DLM.
Given the low error rates why is the interleaving depth still set so high?

Is it possible to confirm the provisioned DLM stability level?
https://kitz.co.uk/adsl/DLM.htm#dlm_stability_level

I will move the modem to test socket (behind the faceplate filer) later this week, record the synch speeds and post the results here.

Regards

Richard

[#8]

No problem Richard.

We'd provision all fibre circuits on Standard stability profile by default which is the BT equivalent of Speed. 

It's difficult to say why interleaving is still switched on as the tests aren't finding any causes.

Let us know how your troubleshooting goes.

[#9]

Hi @Gandalf,

I connected the modem to the test socket (on Friday afternoon).

Attached are a couple of test files showing the modem stats at the test socket and the normal socket.

I believe the differences are negligible.

I have just checked the latest modem stats and since Friday afternoon, there have been 7 errored seconds on the downstream and yet DLM has not attempted to remove interleaving...

Is there any way for an ISP to question the DLM status of a line with BTW or Openreach?

Regards

Richard 

[#10]

Hi @RichardB
We can request our suppliers to take interleaving off your line but it may go back at some point as it is the nature of what it does.

Let us know if you would like us to request that for you.

[#11]

Hi @Beyhive 

My understanding, which my be wrong, is that ISPs cannot request that interleaving is removed from a VDSL line.

I believe that ISPs can request that the DLM "caution counters" are reset, then DLM should have more latitude to relax the lines settings?

As such I guess I would have nothing to lose by asking for a reset?

If so can I please request a DLM reset to see if it improves matters?

Regards

Richard

[#12]

Hi Richard.

Sorry for the previous advice you've been provided, I've arranged for feedback to be passed on as a heads up that we're unable to request interleaving to be removed from a fibre line.

We can only request a DLM reset to be carried out if your speeds are restricted by banding but the Profile Name "0.128M-80M Downstream, Interleaving Low - 0.128M-20M Upstream, Error Protection Off" shows it isn't. 

Apologies for any confusion this has caused.

[#13]

Hi @Gandalf 

My line has been in sync since I undertook the testing a week ago and there have only been 22 error-ed seconds on the downstream in these 6+ days. See attached.

Given that my line appears to have very low downstream error rates, is syncing towards the lower end of the downstream speed range and DLM appears to have taken a leave of absence...

Can I ask if there are any options available to kick start DLM into action?

Regards

Richard

[#14]

Hi Richard.

I'm afraid as we don't have any tools to adjust DLM on a fibre line, it seems that it may be a waiting game.

Sorry that we can't do more to influence your speeds.

[#15]

The good news is that, last night, G.INP was re-applied to my downstream.

My sync went from 56Mbps to 70Mbps and the error rates are still very low.

The latency almost halved from approx 20ms to 11ms.

I have no idea why DLM took approx 6 weeks to activate G.INP but what a difference in line performance when G.INP is active

Richard