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Author Topic: Fibre speed won't adjust  (Read 3685 times)

v0x

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Fibre speed won't adjust
« on: September 24, 2021, 12:44:55 PM »

Hello all, my fibre keeps repeatedly getting stuck at 62 even though it can (and has) achieved higher speeds. When I report as a fault the DLM gets reset which puts the speed at 79 but at some point the speed will drop back to 62 again and never appears to target and speeds between 63-78

Line State: Showtime with TC-Layer sync
Line Mode: G.993.2 (VDSL2, Profile 17a)
Line Uptime: 1d 12h 59m 15s
Annex: B
Data Rate: 62.675 Mb/s / 19.999 Mb/s
Max. Attainable Data Rate (ATTNDR): 91.812 Mb/s / 24.913 Mb/s
Latency: 7.00 ms / 6.00 ms
Line Attenuation (LATN): 12.1 dB / 10.6 dB
Signal Attenuation (SATN): 12.1 dB / 10.5 dB
Noise Margin (SNR): 9.0 dB / 6.4 dB
Aggregate Transmit Power (ACTATP): 0.0 dB / -0.1 dB
Forward Error Correction Seconds (FECS): 146 / 77865
Errored seconds (ES): 0 / 2887
Severely Errored Seconds (SES): 0 / 111
Loss of Signal Seconds (LOSS): 0 / 2082
Unavailable Seconds (UAS): 83 / 83
Header Error Code Errors (HEC): 0 / 0
Non Pre-emptive CRC errors (CRC_P): 0 / 0
Pre-emptive CRC errors (CRCP_P): 0 / 0
ATU-C System Vendor ID: Infineon 178.6
Power Management Mode: L0 - Synchronized

If I connect my old Sky router it will connect at 79 too, but the two Talktalk routers I used to have both had the same problem as my current BT Home Hub 5A (openwrt), is this a stuck profile or something else?

Thanks
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broadstairs

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Re: Fibre speed won't adjust
« Reply #1 on: September 24, 2021, 01:48:15 PM »

I suspect this is a result of contention with other users, this happens frequently.

Regards   Stuart
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licquorice

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Re: Fibre speed won't adjust
« Reply #2 on: September 24, 2021, 01:56:23 PM »

There is no contention at the DSL layer.

You have a line fault that needs to be fixed before you will see any improvement. A DLM reset is pointless unless the underlying fault that is causing DLM to intervene is fixed.
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meritez

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Re: Fibre speed won't adjust
« Reply #3 on: September 24, 2021, 02:24:13 PM »

Hello all, my fibre keeps repeatedly getting stuck at 62 even though it can (and has) achieved higher speeds. When I report as a fault the DLM gets reset which puts the speed at 79 but at some point the speed will drop back to 62 again and never appears to target and speeds between 63-78


If I connect my old Sky router it will connect at 79 too, but the two Talktalk routers I used to have both had the same problem as my current BT Home Hub 5A (openwrt), is this a stuck profile or something else?

Thanks

which lantiq dsl driver are you using on your BT Home Hub 5A?
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v0x

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Re: Fibre speed won't adjust
« Reply #4 on: September 24, 2021, 03:54:18 PM »

Firmware for my Home Hub 5A is 5.8.1.8.1.6

I forgot to mention when the speed lowers, the transmit power shoots up to around 2db; also I found the line coming in is made of aluminium/tin/or something because it's silver. 
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Alex Atkin UK

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Re: Fibre speed won't adjust
« Reply #5 on: September 24, 2021, 05:02:52 PM »

That's strange, as at least from what you posted there isn't a lot of errors so not sure why it would keep pulling the stats down.  Though aluminium lines are never a good thing.
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Ixel

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Re: Fibre speed won't adjust
« Reply #6 on: September 24, 2021, 06:32:25 PM »

Data Rate: 62.675 Mb/s / 19.999 Mb/s
Max. Attainable Data Rate (ATTNDR): 91.812 Mb/s / 24.913 Mb/s
Latency: 7.00 ms / 6.00 ms
Noise Margin (SNR): 9.0 dB / 6.4 dB

Something has caught my attention. I'm wondering... assuming your line supports G.INP if, perhaps, the modem in question doesn't support G.INP and is falling back to a 'compatibility state'... that being traditional interleaving (INP/delay). I say this because I assume that your latency values are 'delay' values, typically seen on traditional interleaving, although odd values I must admit but that could be down to the modem. This is speculation though as I don't know what your other modem reports, and I could be wrong about the 'latency' values. Even so it's odd that it won't go higher than 62Mbit~ downstream given the spare noise margin. Assuming you go back to the other modem, am I right in understanding that it resyncs at full speed without a DLM reset?
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meritez

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Re: Fibre speed won't adjust
« Reply #7 on: September 24, 2021, 06:45:19 PM »

Firmware for my Home Hub 5A is 5.8.1.8.1.6

I forgot to mention when the speed lowers, the transmit power shoots up to around 2db; also I found the line coming in is made of aluminium/tin/or something because it's silver.

Your firmware doesn't support vectoring according to xdarklight https://xdarklight.github.io/lantiq-xdsl-firmware-info/

Please may you try a lantiq firmware with vectoring support
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v0x

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Re: Fibre speed won't adjust
« Reply #8 on: September 24, 2021, 08:08:00 PM »

Something has caught my attention. I'm wondering... assuming your line supports G.INP if, perhaps, the modem in question doesn't support G.INP and is falling back to a 'compatibility state'... that being traditional interleaving (INP/delay). I say this because I assume that your latency values are 'delay' values, typically seen on traditional interleaving, although odd values I must admit but that could be down to the modem. This is speculation though as I don't know what your other modem reports, and I could be wrong about the 'latency' values. Even so it's odd that it won't go higher than 62Mbit~ downstream given the spare noise margin. Assuming you go back to the other modem, am I right in understanding that it resyncs at full speed without a DLM reset?

The Sky router (ER110) will sync at the same speed but normally (overnight) it will then sync back at 79, just tried the Annex B vectoring firmware and the max attainable rate has dropped

Line State: Showtime with TC-Layer sync
Line Mode: G.993.2 (VDSL2, Profile 17a)
Line Uptime: 0h 0m 43s
Annex: B
Data Rate: 62.675 Mb/s / 20.000 Mb/s
Max. Attainable Data Rate (ATTNDR): 62.910 Mb/s / 25.317 Mb/s
Latency: 7.00 ms / 6.00 ms
Line Attenuation (LATN): 12.3 dB / 10.7 dB
Signal Attenuation (SATN): 12.3 dB / 10.6 dB
Noise Margin (SNR): 9.2 dB / 6.6 dB
Aggregate Transmit Power (ACTATP): 0.6 dB / 0.6 dB
Forward Error Correction Seconds (FECS): 184 / 77917
Errored seconds (ES): 0 / 2887
Severely Errored Seconds (SES): 0 / 111
Loss of Signal Seconds (LOSS): 0 / 2088
Unavailable Seconds (UAS): 127 / 127
Header Error Code Errors (HEC): 0 / 0
Non Pre-emptive CRC errors (CRC_P): 1 / 0
Pre-emptive CRC errors (CRCP_P): 0 / 0
ATU-C System Vendor ID: Infineon 178.6
Power Management Mode: L0 - Synchronized

I assume the right firmware is VDSL over ISDN Annex B firmware, which is confusing as I thought ISDN was dead

Here is the router stats from the Sky router, which I just plugged in and is syncing at the same speed, no idea why there's DS1, 2 and 3
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mofa2020

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Re: Fibre speed won't adjust
« Reply #9 on: September 24, 2021, 08:56:09 PM »

I assume the right firmware is VDSL over ISDN Annex B firmware, which is confusing as I thought ISDN was dead

UK uses POTS not ISDN.
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g3uiss

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Re: Fibre speed won't adjust
« Reply #10 on: September 24, 2021, 09:20:27 PM »

DS1 2 3 are the download bands of the VDSL2 spectrum
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v0x

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Re: Fibre speed won't adjust
« Reply #11 on: September 24, 2021, 10:19:04 PM »

UK uses POTS not ISDN.
Guess this could be the reason since all the firmware I've got all says VDSL over ISDN (including the original firmware), I'll see if I can get different firmware for VDSL over POTS instead, thanks.
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meritez

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Re: Fibre speed won't adjust
« Reply #12 on: September 24, 2021, 11:24:28 PM »

UK uses POTS not ISDN.

Er no, vdsl in the UK is annex b which is correctly termed as vdsl over ISDN, but Openreach uses an Annex B bandplan (tone set) from the VDSL2 spec (G.993.2) over Annex A physical infrastructure. So for the UK, the modem hardware/firmware needs to be Annex A, but it will sync using Annex B.

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mofa2020

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Re: Fibre speed won't adjust
« Reply #13 on: September 25, 2021, 12:39:02 AM »

Guess this could be the reason since all the firmware I've got all says VDSL over ISDN (including the original firmware), I'll see if I can get different firmware for VDSL over POTS instead, thanks.

Anytime  ;) I think that may make a difference.

Er no, vdsl in the UK is annex b which is correctly termed as vdsl over ISDN, but Openreach uses an Annex B bandplan (tone set) from the VDSL2 spec (G.993.2) over Annex A physical infrastructure. So for the UK, the modem hardware/firmware needs to be Annex A, but it will sync using Annex B.

There seems to be some confusion about what is meant by Annex A/B. 'Annex' in this context is a Euro word meaning 'Appendix'. It refers to an appendix to an official document. There are two relevant documents being mixed up here, one describing the hardware for a DSL service and one describing the band plan configuration. A modem described as Annex A means that its hardware supports xDSL over POTS (the UK system) and Annex B means that its hardware supports xDSL over ISDN (the German system) Some modems may support both, but most don't. An Annex B modem is no use in the UK.
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Alex Atkin UK

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Re: Fibre speed won't adjust
« Reply #14 on: September 25, 2021, 10:00:15 AM »

Guess this could be the reason since all the firmware I've got all says VDSL over ISDN (including the original firmware), I'll see if I can get different firmware for VDSL over POTS instead, thanks.

When I looked at the unofficial Lantiq firmware site, there is no mention of VDSL over POTS on ANY firmware.

VDSL over POTS seems to be included in the VDSL over ISDN firmware.  This makes sense as the only difference is likely to be the band plan.

There's nothing wrong with the OpenWRT Lantiq firmware, its rock-solid stable for me and syncs higher than any other device I've tried.
The only possible exception is as mentioned above, it doesn't include vectoring support, but swapping out the firmware is very easy.
« Last Edit: September 25, 2021, 10:09:03 AM by Alex Atkin UK »
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