This topic

VDSL rate reduction up and down

threetreesderek — Sat, 09 Jan 2021 08:48:41 GMT

Good morning,

I have two questions:

1/ We have seen a substantial reduction in VDSL connection rate. Typical rates at this property would be 35Mb/s, we are currently clocked in at 23.5Mb/s. (BT's "Stay fast guarantee" is at 26Mb/s here so there is definitely an issue to raise). Real download speeds reported from BT wholesale performance and ookla are 20Mb/s so this all ties up.

I have been tidying up wiring in an effort to improve speeds over the last few days so I suspect an automatic IP profile caused by some frequent disconnects, but I have not changed anything since we were happily clocked in at 35Mb/s. Will attach modem and cabinet stats below. Is is possible someone takes a look and identifies if this is likely a cap issue?

2/ In reality we are not seeing anything like the upstream rate the modem is clocked in at, currently 7Mb/s. BTW speed test shows a burst of 5Mb/s followed by a rapid throttling down to 2Mb/s stable upload rate. This is backed up by ookla.

I notice a big reduction in SNR during high downloads, so I wondered if the line was self-throttling (e.g. a crosstalk issue) for some reason. Alternatively, ts the throttling part of a customer profile? I understood a 2Mb/s cap used to be applied and am hoping that this might be a hangover of a previous contract (upload rate getting important with video calls etc being more prevalent). Obviously I am keen to improve real upload speeds to match what the line is capable of.

We are Fibre 1 subscribers.

Thank you in advance for your support.

BTW advanced diagnostic (this is what makes me think a profile has been applied):

Advance Test

Download Test

Download speed achieved during the test was 20.24 Mbps

For your connection, the acceptable range of speeds is 20 - 21.33 Mbps

IP Profile for your line is 21.33 Mbps

20.24 Mbps

21.33 Mbps

Upload Test

Upload speed achieved during the test was 5.96 Mbps

IP Profile for your line is 10 Mbps

5.96 Mbps

10 Mbps

Exchange checker results:

Exchange DIDMARTON is served by Cabinet E2

Featured Products Downstream Line Rate(Mbps) Upstream Line Rate (Mbps) Downstream HandbackThreshold(Mbps) WBC FTTC Availability Date WBC SOGEA Availability Date Left in JumperHigh Low High Low VDSL Range A (Clean)

VDSL Range B (Impacted)

40	25	7.9	6	20	Available	Available	--
39.1	21.4	7.8	5.7	17.7	Available	Available	--

Featured Products Downstream Line Rate(Mbps) Upstream Line Rate (Mbps) Downstream Range (Mbps) Availability Date FTTP Install ProcessFTTP on Demand

330

Available

ADSL Products Downstream Line Rate (Mbps) Upstream Line Rate (Mbps) Downstream Range(Mbps) ADSL Availability Date WBC SOADSL Availability Date Left in JumperWBC ADSL 2+WBC ADSL2+ Annex MADSL MaxWBC Fixed RateFixed Rate

Up to 2	--	1 to 3.5	Available	Available	--
Up to 2	Up to 0.5	1 to 3.5	Available	Available	--
Up to 1.5	--	1 to 2.5	Available	Available	Yes
0.5	--	--	Available	Available	--
0.5	--	--	Available	--	Yes

Observed Speeds VDSLMax Observed Downstream SpeedMax Observed Upstream SpeedObserved Date

34.99

6.89

2021-01-04

Other Offerings Availability DateVDSL MulticastADSL Multicast

Available

Premise Environment StatusBridge TapVRINTE FacePlateLast Test Date

28-12-2020

Exchange Product Restrictions StatusFTTP Priority ExchangeWLR WithdrawalSOADSL Restriction

Modem stats (Billion 8800NL though I do have a HH4b here if required for testing)

xDSL
Mode	VDSL2
Traffic Type	PTM
Status	Up
Link Power State	L0

	Downstream	Upstream
Line Coding (Trellis)	On	On
SNR Margin (dB)	5.1	5.9
Attenuation (dB)	26.2	0.0
Output Power (dBm)	10.1	2.9
Attainable Rate (Kbps)	22674	7027

Rate (Kbps)	23465	7027

B (# of bytes in Mux Data Frame)	227	207
M (# of Mux Data Frames in an RS codeword)	1	1
T (# of Mux Data Frames in an OH sub-frame)	0	38
R (# of redundancy bytes in the RS codeword)	10	8
S (# of data symbols over which the RS code word spans)	0.3090	0.9396
L (# of bits transmitted in each data symbol)	6161	1839
D (interleaver depth)	4	1
I (interleaver block size in bytes)	238	108
N (RS codeword size)	238	216
Delay (msec)	0	0
INP (DMT symbol)	53.00	0.00

OH Frames	0	0
OH Frame Errors	0	11
RS Words	34823760	11495532
RS Correctable Errors	153568	8
RS Uncorrectable Errors	0	0

HEC Errors	0	0
OCD Errors	0	0
LCD Errors	0	0
Total Cells	121843526	0
Data Cells	1716968	0
Bit Errors	0	0

Total ES	0	10
Total SES	0	0
Total UAS	0	0

Re: VDSL rate reduction up and down

imjolly — Sat, 09 Jan 2021 10:18:31 GMT

looking at the information you have posted you had a 34.99mb connection speed on 4/1/21 but now you are down to 23.4mb and more concerning is attainable is 22.6mb. not sure what you have changed in you wiring tidy up but something has changed. if you were being restricted by DLM due to disconnections that would affect your connection speed but not your attainable speed

are you able to connect to the test socket with a filter and repost router stats. when in test socket check for line noise dial 17070 option 2 should be silent and best with corded phone

you up speed according to stats is as expected at 7mb

Re: VDSL rate reduction up and down

pippincp — Sat, 09 Jan 2021 12:38:03 GMT

Also worth noting G.INP appears inactive, this could be due to the disconnects while sorting the wiring. This should return with about 10 days stable connection and deliver a speed boost.

Re: VDSL rate reduction up and down

threetreesderek — Sat, 09 Jan 2021 15:27:18 GMT

Thanks for your message, I'm blown away by the patience of those on this forum.

I think it is embarrassment time for me though as the stats from the spare cable + test socket + separate filter are looking in line with what I had expected (for completeness, results are below). I thought I had already ruled out an internal issue.

There is a small impact which I need to investigate when I connect the MK3 filtered faceplate (and the phone extension wiring which is hardwired into it), but we are back in the 35Mb/s realm.

Will leave it like this overnight as this looks like similar conditions to how I thought I had left it after doing the tidy-up. Thank you for the guidance and apologies for wasting your time on something I should have spotted for myself. If all good then it is time to make up a new connection cable for the modem...

xDSL
Mode	VDSL2
Traffic Type	PTM
Status	Up
Link Power State	L0

	Downstream	Upstream
Line Coding (Trellis)	On	On
SNR Margin (dB)	6.0	6.0
Attenuation (dB)	25.9	0.0
Output Power (dBm)	12.1	2.9
Attainable Rate (Kbps)	38042	6878

Rate (Kbps)	35000	6878

B (# of bytes in Mux Data Frame)	73	207
M (# of Mux Data Frames in an RS codeword)	1	1
T (# of Mux Data Frames in an OH sub-frame)	0	37
R (# of redundancy bytes in the RS codeword)	6	8
S (# of data symbols over which the RS code word spans)	0.0666	0.9600
L (# of bits transmitted in each data symbol)	9610	1800
D (interleaver depth)	8	1
I (interleaver block size in bytes)	80	108
N (RS codeword size)	80	216
Delay (msec)	0	0
INP (DMT symbol)	58.00	0.00

OH Frames	0	0
OH Frame Errors	0	0
RS Words	59824	0
RS Correctable Errors	174	0
RS Uncorrectable Errors	0	0

HEC Errors	0	0
OCD Errors	0	0
LCD Errors	0	0
Total Cells	131055	0
Data Cells	2	0
Bit Errors	0	0

Total ES	0	0
Total SES	0	0
Total UAS	116	116

Re: VDSL rate reduction up and down

threetreesderek — Sat, 09 Jan 2021 15:29:19 GMT

Thanks for that comment. Out of interest, how would one spot if G.INP was active from those numbers? There are plenty of stats about it on the router so I have to admit I assumed it was operating as expected.

Re: VDSL rate reduction up and down

pippincp — Sat, 09 Jan 2021 15:35:44 GMT

Downstream SNR would drop to 3dB. Looking at your stats now though it doesn't look as if it's needed.