It's perfectly possible for a long line to have to run at 15dB Target SNR in order to run stably. After all, I've been doing so for a good many years now. Just because you yourself don't happen to have the same difficult line operating problems that I and some others have doesn't mean that I and those others are wrong in the way that we have to run our connections. Forgive me for my pique but all you are doing by making your assertions is that you're diverting attention from the real problem in hand.

I've been using DMT for several years now in order to promptly get the line to run at a slower rate and so remain stable when first commissioning the router or when very rarely needing to resync because of other reasons. It's worked wonderfully well in all that time. I brought the internal wiring, short and simple though it is, up to a very high standard a year ago. It's only been this last week or so when the phone suddenly went bananas and the ADSL connection started playing up that access to the Internet became randomly impossible. From what we now kniow, it seemed to have coincided with thieves having stolen BT cables in the neighbourhood and put the phone and Internet connections of hundreds of businesses and households on this exchange out of action. Even today, some phonelines around here haven't been restored yet.

Yes, my line is long, and it's spuriously very noisy as well. That's just the luck of the game, or rather the lack of it. Over the years it's become plain that some of the noise has exceeded 12dB. The source of the noise has been at some unknown point or points somewhere between my house and the exchange. Believe me, the electrical environment of my own and neighbouring properties is very clean, and in that I do know what I'm talking about! As I've already stated, my own internal phone/ADSL wiring is impeccably good and you'll just have to take my word for that.

At the moment, I'm doing just about the most sensible and logical thing I can do, namely swapping the router for a different one, so I can't see what you're complaining about. It takes time to organise these things. Over the last two weeks I've tried just about everything else that's possible.

I think that, although it certainly seemed at one point like this problem was down to my ISP's authentication of the connection, one or two of you who've still had reservations about the general integrity of my Netgear router could well be right. This is why I've gone to great pains to borrow a disused but thought-to-be-still-good router from a friend. But since, unlike with the Netgear, there's no means of user control over the line speed that it initially negotiates, I'll have to keep observing over many days now before I can come to any sort of conclusion. Clearly, if the temporary router in that time shows no sign of non-access and then when I swap back to using the Netgear the symptom quickly shows, then we'll have nailed it finally. So, I'll report back here in a few days time.

I've not heard from my ISP for three solid days now, so I've no idea what they've been doing, if anything. It's probably been all too much for them and they've probably quit the country. Heh, heh, heh!

No answers to my Qs then?

Still not clear on the symptoms.

In reply to a post by MrSaffron:

Here in may be the problem, you tweaked the old DG834 such that it was not following all the suggestions it would receive from the DSLAM.

Without you sniffing every command over the ADSL link, you don't know if the other modem was ignoring PPP drop requests. So that the modem sat there thinking it still had a good PPP session, when it had actually gone stale.

Indeed, my other thought was the router was simply ignoring or not timing out correctly. As it stands stale/dropped PPP sessions are not uncommon but a router should detect it within seconds and redial automatically. Every one of the symptoms can be explained by the OP's router not doing this.

Right, I'm back, y'all. Aside from needing to catch up on a host of other important non-IT jobs that have been neglected these last two weeks, I've been seeing how an alternative ADSL router has worked in my setup over the last three days or so.

The outcome is still quite difficult to fathom. On the one hand, the alternative router, an old Billion 5100, never once prevented access to the Internet. But on the other hand, the Billion never seemed to negotiate an SNR of anything higher than 6dB over those three days and the sync speed it reported was a constant 6.3M bps, which I know my line cannot support without falling over.

The Billion 5100 is really basic, ostensibly obsolete, and I highly suspect that it has some important firmware bugs, which might include an inability to collect the line statistics properly. This may be why the former owner dumped it after only about a year's use.

You can't use DMT with the Billion 5100, so I couldn't experiment with forcing different target SNRs. I found out that the 5100 has a CLI command set, usable from a Command Prompt, that includes one for setting the target SNR but when I tried it, it simply didn't work; there was no evidence that the command ever passed to the router. I of course checked that other things weren't blocking it.

Meanwhile, I tested the Netgear's little PSU. By all accounts, these are not very robust plugin power units. However, the measured off-load output voltage from the PSU looked perfectly okay.

When today I put back the Netgear router, it initially ran okay. But as soon as I re-sync'd the line with DMT to get a slower, more sensible speed, I got the non-access problem. Even with the SNR negotiated at 12dB I got the problem. I've left the SNR on 12dB and will see how things pan out for a day or two more.

Qasdfdsaq, you may have a point. In fact, more than one of you have summised of late that the DSLAM may have, for some time, been unable to cope with the way in which I've been operating the line. The only counter to that is that I've been using the line like this for several years and the DSLAM has always complied - until a week or so ago! That's to say, the DSLAM has always co-operated, whether I set the SNR to 15dB, 12dB or whatever. Mind you, during the use of DMT, the DSLAM has on occasions simply not responded to a re-sync at all, leaving the line in a sorta 'hung' state (even though the indicators on the Netgear show that the line is apparently still fully up and running). But a second attempt has then succeeded. Something else that's made me wonder is that, for as long as I can remember, the browser sometimes fails to reach a website from the URL in the browser's address-box and I have to try a second time. This kinda suggests that something has been edgey.

Looking at the bits-per-tone plot in DMT, the plot is very poor, in that the decline is rapid and there are many gaps as the tone frequencies increase. I don't recall the line looking quite that bad before. And yet the line at my end, in physical terms, is about as good as it gets.

For the present, what I'm concerned about is whether I have a damaged Netgear router. If the router's no longer physically working properly (due to, say, damaged line-drivers in the modem chip), then the router might not be handshaking the data transfers properly. Clearly, I'd want to avoid any downloads of important updates, etc. if the router were simply now unreliable as to its error-correcting capability.

It could transpire, though, that the problem all along has, as been suggested, been due to my pushing the DSLAM too far, in demanding that it negotiates at 14 or 15dB. It might be that I've just been lucky for several years. But that sort of SNR is barely sufficient to give me a stable line.

Maybe it's now time for me to seriously consider switching to FTTC, as I guess that then these tweaking requirements would disappear, a different DSLAM would be in use, and I'd have a less noisy line anyway? I began to consider it about six months ago but perhaps I should now do it in earnest. As I understand it, for that I'll need a new PPPoE router. But all queries over that are best left to a completely separate forum topic.

Edited by deleted (Sat 05-May-12 16:52:25)

In reply to a post by meditator:

the sync speed it reported was a constant 6.3M bps, which I know my line cannot support without falling over.

But has the Billion done so?

In reply to a post by meditator:

Something else that's made me wonder is that, for as long as I can remember, the browser sometimes fails to reach a website from the URL in the browser's address-box and I have to try a second time. This kinda suggests that something has been edgey.

That's not uncommon! Maybe the route or the end server is busy at that instant.

Router stats?

Yes, but I can't tell how many times it's done it, as I've not sat over it for the last 3 - 4 days, and the stats that the router gives you are absolutely minimal. You get little more than just the instantaneous sync speed and SNR. The Billion 5100 is a truly awful device by today's standards. It responsiveness is appalling, it taking about 3 secs typically to get a webpage. By comparison, my Netgear 834 is fast and slick.

I've been using the Netgear router quite a lot today, having set the target SNR to 12dB with DMT earlier this morning, and have been trying hard to make the connection block. But so far the connection to the Internet's been holding up. I need to give it a day or two more yet but I think we may finally, but finally, be on to something here.

Postscript: For some unknown reason I've not done this during these last two weeks but just now I pushed the target SNR down to around 9dB, and then as a separate exercise right down to 6dB. In both cases the Internet became inaccessible. Now surely that should not be happening?! As before, all visible aspects of the line remain up and running throughout and, again as before, the only way I can then regain access is to go into the router and re-apply my logon particulars.

So, one thing's for sure, this problem's not been happening because I've demanded too much of the DSLAM as regards negotiated SNR.

One thing I've just remembered is that following Skymarket's serious e-mail server failure a few weeks ago, I found that my line's sync had been affected (the line was down, with the Internet indicator permanently off but all others still up) and I'd lost the Interleaved status for my line. Normally, the extent of the noise on my line is such that, for the line to run at all stably I not only have to have a target SNR of between 12 and 15dB but also the line has to be run in Interleaved mode. Finding that its status was no longer Interleaved, I contacted Skymarket and asked them to arrange for it to be put back. This was duly done within 24 hrs. But I now wonder whether something else was done to change the DSLAM's mode of operation, something which perhaps might now account for all this strange non-access I've been getting.

Edited by deleted (Sat 05-May-12 22:57:00)

Buy yourself a cheap new (spare) Netgear DG834GT or DG834G v4, which can be tweaked even w/out DMT, on eBay and take the router out of the equation. Can be had for < £20.

Well, that's all academic now, as I've decided to go FTTC and to sign up with a different ISP to Skymarket (Skymarket can't offer FTTC at present, anyway). I'm simply not prepared to spend any more of my time on this problem. I've got too many other time-sapping and urgent things to do.

I remain of the view that the problem probably lies with either the DSLAM or with a Transport or Network level, further up toward Skymarket. Way back in the past the DSLAM was problematic and Skymarket had to send an engineer to the exchange to sort it out on one occasion. The engineer then came to mine to test the 'correction' and confirm that I was up and running fully again. It seems that these days that's no longer being done.

I think something was changed inadvertently when, some weeks ago after a Skymarket shutdown, they instructed an engineer to restore my Interleaved status, which had mysteriously disappeared.

Skymarket currently seem unwilling to discuss the problem any further with me. I think that says it all.

Well, we'll never know! You asked for help but never provided what was requested; instead launching into long verbose spiels about red herrings and grasping straws

Way back in the past the DSLAM was problematic and Skymarket had to send an engineer to the exchange to sort it out on one occasion. The engineer then came to mine to test the 'correction' and confirm that I was up and running fully again. It seems that these days that's no longer being done.

Some one is lying to you.
Engineers are tasked at the CP's request, to check and repair broadband problems every day.