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Author Topic: Loop loss (attenuation) question  (Read 15873 times)

toulouse

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Re: Loop loss (attenuation) question
« Reply #75 on: June 18, 2012, 10:16:33 AM »

Ok, then - it's Monday morning and it's time for a quick update.

It looks as if at around 2:55 this morning my Upstream Attenuation was uncapped, and is now showing as 888. This appears to have had the effect of increasing both Down and Upstream speeds by a small amount. The annoying thing about these changes of speed, is that the line had become completely unusable, at least no access to any browser pages or email accounts. I wish I knew what caused this problem each time there is a change of speed / IP address, from which the only way to recover is a router reboot. Said operation carried out just before 6:00 this morning. The current stats from the router, some 4 hours after the reboot, are

          Down                              Up
         11641 Connection speed    888
           36.0     Attenuation        17.2
            4.1     Noise Margin        14.8

.....so as far as I can see this whole exercise has resulted in a minor change in connection speed, slightly higher than before. There has also been an approximate halving of the Upstream Noise Margin and roughly a doubling of the Upstream connection speed.

From this I conclude that I just ain't gonna get it much better than this which is a little disappointing.

 
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c6em

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Re: Loop loss (attenuation) question
« Reply #76 on: June 18, 2012, 12:33:04 PM »


I recall that an upstream sync of 888 is the standard upstream interleaved uncapped sync speed figure on 21CN.
(interleaving can be applied quite separately and selectively on either/or downstream and upstream)
 
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Re: Loop loss (attenuation) question
« Reply #77 on: June 20, 2012, 01:28:22 PM »

It doesn't look "uncapped" to me. Looks like a load of INP applied to upstream.

He should get over 1.1Mbps even with some INP applied. The Be upstream will be fastpath, it always is unless the line is dreadful.

Were it me I'd ask for DLM to be reset/restarted, or a manual reconfigure on the line - assuming those are possible on 21CN?

Is the line any more stable?
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coolsnakeman

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Re: Loop loss (attenuation) question
« Reply #78 on: June 20, 2012, 03:58:21 PM »

I apologise first hand if anyone has asked this question but is the router your using compatable with ADSL2+???? If it wasn't that most certainly would give you disconnections on your broadband. Although your router may not beable to sync past 8Mb if it was just ADSL compatable but stranger things have happened on ADSL services! Just food for thought really. Only thing i would suggest if at all possible is to get this into the test socket. Although you may not have internal wiring that doesn't mean to say you don't have a faulty NTE5 front faceplate that could be causing these problems.

Gary
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toulouse

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Re: Loop loss (attenuation) question
« Reply #79 on: June 20, 2012, 07:27:48 PM »

Thanks for the further input, but I think there's no more to be got from this line. It was very good on ADSLMax, but it's CARP for the current ADSL2+ product. Whether that is caused by the line or the ADSL2+ product I wouldn't like to hazard a guess. But with all this talk of DLM (that dark mysterious Black Box) that seems to have limitless powers to screw up an end users broadband experience, probably the best I can do is to stop using that line and stick with the O2 LLU line instead.

@coolsnakeman - yes, of course the router is compatible with ADSL2+, it's a Netgear 834G v4, and I have it set to adsl2+ under Dsl Mode, under ADSL Settings. I'd have to be a bit of a numpty to start this thread if I hadn't done most of the obvious things and then ask for peoples views on this situation, wouldn't I ? As for the test socket, been there, done that, seen the video and I've got the t-shirt in all the available colours.

@rizla - I'm inclined to agree with you about the upstream rate, my O2 Upstream rate is currently at 1256kbps, but I think the default upstream rate on Plusnet is 888. You can request them to crank it up a bit, but as I said before I don't need more Upstream, but I could definitely do with a bit more on the Downstream. It seems to me that this just ain't gonna happen - I have a line which is not performing as I was told it was going to (even after tidying up my internal wiring), so I feel totally justified in cancelling the Plusnet services. I suppose I could ask them to put line into training again, and see what happens, but I think I'd just be delaying the inevitable.

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c6em

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Re: Loop loss (attenuation) question
« Reply #80 on: June 20, 2012, 08:30:50 PM »


The capped upstream on Plusnet is around 443 or 440kbps sync
If they uncap it - it is 888kbps fixed interleaved
If the DLM switches off interleaving upstream it's whatever the target upstream SNR margin of 6 on the line will give - usually around 1000kbps.

I've had all three setting as above on my line.
Originally fixed at 888kbps always at an interleaver depth of 8.
The the DLM changed D from 8 to 4 and the sync ran free at whatever SNR it found - in my case around 1181kbps
Then during a mega fault the upstream was capped and its now at 440 at D=8  ie capped interleaved
Havent yet got round to ask PN for it to be uncapped again.................
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coolsnakeman

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Re: Loop loss (attenuation) question
« Reply #81 on: June 21, 2012, 08:33:58 AM »

@coolsnakeman - yes, of course the router is compatible with ADSL2+, it's a Netgear 834G v4, and I have it set to adsl2+ under Dsl Mode, under ADSL Settings. I'd have to be a bit of a numpty to start this thread if I hadn't done most of the obvious things and then ask for peoples views on this situation, wouldn't I ? As for the test socket, been there, done that, seen the video and I've got the t-shirt in all the available colours.

Some of the basics are usually the most common to be missed so that is why i make it a point to suggesting them. I have spoken to microsoft and cisco certified engineers who still can't get it right and tend to miss some of the most obvious causes of the problem. Only reason being is they get to smug and dive in with all there technical knowledge but seem to forget that troubleshooting is like climbing a ladder. So you can imagine how stupid they feel when i ask them to change the filter and it works. Anyhow it is fairly clear to me that you have your sights set on this issue not being resolved so good luck with cancelling with plusnet cause the next step would be fighting with them not to charge you early cancellation fees if you still in contract. Off course if your out of contract then that part should be easy enough  ;D

Gary
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kitz

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Re: Loop loss (attenuation) question
« Reply #82 on: June 21, 2012, 09:39:17 AM »

gary's mention of adsl2+ router had just made me think of something.

You mention that the line performed well on adsl1 but not adsl2+...  so something you could perhaps try as an experiment and thats using adsl2.

On some lines adsl2 works better since it uses the better algorithms and modulation of adsl 2+ but without opening up the addional frequencies which can cause instability for longer lines.  Ideally looking at an DMT graph to see which tones you currently use would be a useful before performing this step to view how many of the adsl2+ tones you currently use.   Since you dont seem to be hitting 12Mbps, then yours could be an ideal line to play with adsl2 mode and youve nothing much to lose anyhow if that lines going to be got rid of.

Like I say its just an experimental thing that may or may not work, but it does seem to benefit some lines which sync at <12Mbps.  I cant recall off the top of my head if the the dg834v4 has the option to change the setting yourself in the GUI, but I think it may.


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coolsnakeman

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Re: Loop loss (attenuation) question
« Reply #83 on: June 21, 2012, 10:45:01 AM »

gary's mention of adsl2+ router had just made me think of something.

So there you have every suggestion brings a new idea  :lol:

Gary
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toulouse

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Re: Loop loss (attenuation) question
« Reply #84 on: June 21, 2012, 12:06:00 PM »

@kitz & @coolsnakeman - I guess what I have been trying to establish since starting this thread is whether a line like mine, i.e. 36dB attenuation should be able to sync and remain relatively stable at the rate that Plusnet told me I could expect in their email of a couple of years ago. They told me Up to 14Mbps, but the line has never achieved anywhere near that, it's currently struggling to get to 12Mbps, let alone 14Mbps.

I would be quite happy to try selecting ADSL2 in ADSL settings, as opposed to Auto or ADSL2+ which is currently selected, just to see what happens. Just out of interest, how might that affect the achievable sync speed ? It looks as if my Plusnet profile is hard coded at 11; now whether that is down to recent intervention by Plusnet support or the STUPID DLM system I don't know - prior to the most recent problem with the line, the profile seemed to be stuck at 10 (or some strange variation of that) for months at a time. This is also quite different from 14Mbps, isn't it.
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coolsnakeman

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Re: Loop loss (attenuation) question
« Reply #85 on: June 21, 2012, 12:32:07 PM »

They told me Up to 14Mbps

It seems to me plusnet have there backs covered then if they told you "up to 14Mbps" so 11Mb or 12Mb to them is perfectly fine. I would of thought however that on a 36db line attenuation you may have been able to achieve more but that is all down to certain factors that i am sure both me and you know what those factors are.

Gary
« Last Edit: June 21, 2012, 12:38:49 PM by coolsnakeman »
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kitz

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Re: Loop loss (attenuation) question
« Reply #86 on: June 21, 2012, 01:09:40 PM »

>>> Just out of interest, how might that affect the achievable sync speed ?

Would need to see a DMT graph to see which bits are loaded in what bins to get a better idea...  and of course its something that no-one can really predict, but on some lines adsl2 is more stable because its takes out the higher frequencies where most instability occurs.  If you currently have a lot of bits loaded above tone 255 then its probably not for you as you may likely end up losing some sync speed. :/
A bit loading graph either from DMTtool or Routerstats should give us a fair idea though.

>> It looks as if my Plusnet profile is hard coded at 11;

It wont affect your max throughput then, but results may be seen in the sync speed but it may help stability.
Because you already sync at 11Mbps, your line is 'borderline' as to whether or not it could benefit in adsl2 mode and its just an experiment.
I guess you could look at it 2 ways:- either (1)that line is going to go anyhow so Im not bothered about messing around an leave it until it goes, or (2) that line is going to go anyhow, so Im not bothered if I do mess things further, but at least I tried.
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burakkucat

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Re: Loop loss (attenuation) question
« Reply #87 on: June 21, 2012, 01:38:32 PM »

From what I recall of the DG834G, one can select Auto, ADSL2+ or G.DMT but not ADSL2:(

Hence I was very pleased to see that when I changed to a 2Wire 2700HG, it automatically selected ADSL2 as most appropriate for my line.

Next week, i plan to perform some experiments with a Huawei HG612 as that device can be set to use G.DMT, ADSL2, ADSL2+ and VDSL2 to name but four modes . . .  :)
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toulouse

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Re: Loop loss (attenuation) question
« Reply #88 on: June 21, 2012, 01:58:49 PM »

Ok, I've just selected ADSL2 under DSL Type under ADSL Settings on my Netgear DG834G v4, followed by a router reboot. That gave me a sync of 8407 kbps on completion, which is really going in the wrong direction as far as I can see. I have now reselected ADSL2+ and now have a sync of 11378, down from earlier today, as I was connected at 11641 before trying these changes. 
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coolsnakeman

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Re: Loop loss (attenuation) question
« Reply #89 on: June 21, 2012, 03:46:53 PM »

Would you be willing to run the risk of an engineer visit from plusnet. At least that way you can show him the speed difference between the 02 connection and your plusnet connection and get a straight answer from him. If your planning on getting rid of the plusnet then i guess there ain't much point in that.

Gary
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