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Author Topic: is there any chance to improve vdsl2 stability ?  (Read 1694 times)

esso

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is there any chance to improve vdsl2 stability ?
« on: June 10, 2022, 07:58:22 PM »

hello,

is it possible to measure stability for this router zte h168n ?
and what are the best values that determine the optimal connection i mean snr and line attenation
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gt94sss2

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Re: is there any chance to improve vdsl2 stability ?
« Reply #1 on: June 12, 2022, 10:22:45 PM »

What speed service have you purchased?
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esso

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Re: is there any chance to improve vdsl2 stability ?
« Reply #2 on: June 12, 2022, 10:28:45 PM »

70 mbit
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Alex Atkin UK

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Re: is there any chance to improve vdsl2 stability ?
« Reply #3 on: June 12, 2022, 11:00:10 PM »

hello,

is it possible to measure stability for this router zte h168n ?
and what are the best values that determine the optimal connection i mean snr and line attenation

Attenuation is a product of the quality/length of the line.  SNRm is merely how close to the maximum "theoretical" maximum you are getting out of the line.

You don't have control over either, they just tell you roughly how well your line is performing.

From that screenshot something does appear off as you should easily be syncing at or above 70Mbit but instead are at 42Mbit.

My gut instinct would be if this was recently connected/upgraded, the ISP is capping the service at 40/2, do they have a lower package around that perhaps they incorrectly provisioned you on?
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Weaver

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Re: is there any chance to improve vdsl2 stability ?
« Reply #4 on: June 13, 2022, 02:52:22 PM »

To answer your original question; a better modem may help, otherwise moan at your ISP.

About SNRM:

The SNRM is a measurement of the robustness vs speed tradeoff of the connection. It’s not a property of the line itself but is in your case chosen by BT’s DLM (dynamic line management) software which controls the settings in the two modems.

A higher SNRM means ‘more robust’ ie better error correction/error protection or less ambitious communication techniques, but slower speed. Higher SNRM is better, but you might prefer a lower SNRM for more unreliability and more speed.

A lower SNRM value means ‘fast, but less reliable’.

In your case your downstream SNRM will be either 6dB (slower, more reliable) or 3dB (faster, less reliable). I’m not sure what the story is regarding your upstream SNRM.

If your line is very short or very high quality or both, or interference is very low, or your line is ‘capped’ (ie speed limited) then you may get the max speed permitted and your SNRM may be at higher values than the usual 3dB/6dB downstream; not sure about upstream. This is a very good thing and you could go faster if only you were allowed to.

People who have G.INP have a second layer of powerful error correction/protection which allows you to have a lower SNRM and so go very fast without as much unreliability as normal. If you have G.INP and downstream 3dB SNRM this is a very high performance setting which should be ok for reliability for many people.

For most people, there will be a chosen ‘target SNRM’ set at the time of connection set-up, and the SNR will go up and down depending on the level of interference, throughout the day, usually being somewhat lower at night.

If the SNRM gets too low, then the modems will drop the connection and reconnect at lower speed, employing extra robustness.

People who have ADSL1/ADSL2/ADSL2+ can either change their target SNRM for both downstream and upstream themselves or ask their ISP to do it for them. People with FTTC/VDSL2 have no control over target SNRM, nor do their ISPs.

If you have G.FAST, which you don’t, then you will iirc have ‘SRA’ (seamless rate adaptation) ie. variable sync rate ie. variable speed and the modems will pick an SNRM and vary the speed according to the conditions. This means that you always get the maximum speed possible at all times. I’m slightly concerned about what this means for applications that measure initial speed and make decisions about service given the verdict. Mind you, effective speed could vary anyway because of variations in competing traffic or congestion, so my reservations must surely be illogical.
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gt94sss2

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Re: is there any chance to improve vdsl2 stability ?
« Reply #5 on: June 13, 2022, 05:07:28 PM »

I'm pretty sure that @esso is not based in the UK..
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burakkucat

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Re: is there any chance to improve vdsl2 stability ?
« Reply #6 on: June 13, 2022, 05:35:53 PM »

I'm pretty sure that @esso is not based in the UK..

I cannot, obviously, confirm or deny that statement but, from what esso has previously posted, there is a distinctly high probability of truth (in the statement).  ;)
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Weaver

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Re: is there any chance to improve vdsl2 stability ?
« Reply #7 on: June 14, 2022, 01:23:44 AM »

Having now looked at the stats I see that the noise margin figures are very very high; this is causing a lot of slowness, unless one or the other of the sync rates so capped ie limited, but the sync rates are not significant round-number multiples of 10 Mbps.

Since the OP is not in the UK, disregard the parts in my earlier post that refer to BT DLM and those that quote particular SNRM values.
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RealAleMadrid

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Re: is there any chance to improve vdsl2 stability ?
« Reply #8 on: June 18, 2022, 08:14:38 AM »

@Alex_Atkin I think you have been mixing up the actual and attainable speeds. The actual sync speeds are 2.047Mbps up and 18.431Mbps down. The attenuation figures show it a fairly short line so speeds should be much higher, the SNRM figures are ridiculously high.

@burakkucat @Weaver I would say not in the UK, the link encapsulation G.993.2_Annex_K_PTM is unusual.

Maybe the OP has got the problem fixed by the ISP , as there have, so far been no responses in this thread
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Alex Atkin UK

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Re: is there any chance to improve vdsl2 stability ?
« Reply #9 on: June 18, 2022, 09:23:39 AM »

@Alex_Atkin I think you have been mixing up the actual and attainable speeds. The actual sync speeds are 2.047Mbps up and 18.431Mbps down. The attenuation figures show it a fairly short line so speeds should be much higher, the SNRM figures are ridiculously high.

No, my point was as its not in the UK we do not know how they provision their services.  The SNRm being high only means its not syncing as fast as theoretically possible, but if the ISP has mistakenly capped the sync rates then that would be expected.

With both sync rates seeming to have a pattern to them (42097 and 2047) that screams ISP banding to me.

Either way, its something the ISP needs to look into.
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burakkucat

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Re: is there any chance to improve vdsl2 stability ?
« Reply #10 on: June 18, 2022, 10:36:49 AM »

@burakkucat @Weaver I would say not in the UK, the link encapsulation G.993.2_Annex_K_PTM is unusual.

Yes, indeed. That is another indicator.
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RealAleMadrid

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Re: is there any chance to improve vdsl2 stability ?
« Reply #11 on: June 18, 2022, 04:06:50 PM »

@Alex Atkin  Have a closer look at the router stats, the actual data rates are 2.047Mbps up and 18.431Mbps down, I don't  know why you keep quoting 42097Kbps as a sync rate, it is the Upstream attainable rate so hardly relevant.

I agree that the Upstream may well be capped at around 2Mbps but the Downstream doesn't look like a sensible capped speed and the OP is expecting 70Mbps
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Alex Atkin UK

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Re: is there any chance to improve vdsl2 stability ?
« Reply #12 on: June 18, 2022, 06:50:18 PM »

@Alex Atkin  Have a closer look at the router stats, the actual data rates are 2.047Mbps up and 18.431Mbps down, I don't  know why you keep quoting 42097Kbps as a sync rate, it is the Upstream attainable rate so hardly relevant.

I agree that the Upstream may well be capped at around 2Mbps but the Downstream doesn't look like a sensible capped speed and the OP is expecting 70Mbps

Crap, you're right.  I don't know why I kept thinking upstream and downstream are on different lines.  I looked at that image three or four times and still misread it somehow.
« Last Edit: June 18, 2022, 06:52:21 PM by Alex Atkin UK »
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