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[cosrush]

I have looked on the internet and found several sites saying that 6db is a good noise margin to have and that this is normal as set by BT.

Mine is usually around 10-12 (although this drops off during peak times) but my ISP has said 12 is the best..............


Can anybody offer any advice as to what a good noise margin is?

[roseway]

There's no single answer to that question. It depends on the quality of your particular line. From the point of view of stability, a higher noise margin is better, but there's a trade-off between noise margin and connection speed. So when a line is first enabled for ADSL Max, a low target noise margin of 6 dB is applied to get the best speed, and if the connection proves to be stable it stays like that. But if the connection suffers from frequent disconnections the automatic DLM process increases the target noise margin in steps of 3 dB at a time until it stabilises the connection. Each increase in target noise margin reduces the connection speed.

In your case it appears that the target noise margin has been increased to 12 dB to make it stable.

[cosrush]

Thanks for the reply

So does that mean it is possible to adjust the noise margin and if it proves stable it could gain me a higher resync?

Who would have to do this BT or my Isp?

When I first went to my current Isp, during the 10 day training period I had several power cuts at home and ive always felt that this could have affected my rate. Despite conversations with my Isp about this they say they cannot re run the training period.

[roseway]

In theory, if your connection is now stable, the automatic process should reduce the target noise margin in steps over a period of weeks. However I'm not aware of any documentation which defines exactly how this works. It's certainly possible to get it manually reset, but you have to get your ISP to request BT Wholesale to do it. If your ISP is unwilling I don't think there's much you can do (apart from changing ISP of course).

[cosrush]

Thanks for the reply.

 

[DrTeeth]

Can anybody offer any advice as to what a good noise margin is?

It depends on your sync speed. If you sync at the max, the higher the SNRM the better. It means that your line will tolerate more noise before degrading the speed. If you don't sync at the max, it means that there has been some issue with your line. It could even be something as silly as you rebooting your router too many times. It should drop by 3dB every 14 days until it reaches 6dB. If the SNRM is 15, it will not drop on its own and you'll need your ISP to nag BT.

If you do tweak your SNRM, don't go crazy...bear in mind that it will drop by 3dB in the future if all is well.

[mr_chris]

It should drop by 3dB every 14 days until it reaches 6dB. If the SNRM is 15, it will not drop on its own and you'll need your ISP to nag BT.

Does it have to be 14 days constant sync, or just 14 days below a certain threshold of "dirty" resync counts?

Out of interest, where did you find that out ... coz I've never heard of any definitive schedule for automatic reduction of the target SNR before - and it certainly doesn't appear to happen in practise!!

[DrTeeth]

Does it have to be 14 days constant sync, or just 14 days below a certain threshold of "dirty" resync counts?

Out of interest, where did you find that out ... coz I've never heard of any definitive schedule for automatic reduction of the target SNR before - and it certainly doesn't appear to happen in practise!!

Tell me about it!

I heard it from several people who work in the business. It has happened to me, but more often than not, the damn thing does not work. One waits for 14 days, the 15 days then...phone ISP in the hope that they are half-decent and can get BT to fix it.

AIUI, it has to be 14 days with no syncs in a lower profile; no doubt the number of syncs will come into it.

That is why I have decided to take the plunge and give Be a try...none of this BT <insert word meaning male gonads>!

[mr_chris]

Yep, exactly the reason I went to Be. My SNR was up to 12dB with no sign of reducing - and my Netgear doesn't support DMT - and ... well I'm sure you can guess the rest.

After > 6 months of constant 8128kbps sync, it got to the stage that depending on time of day, I would sync at either > 7Mb or 4Mb - although it does look like my fluctuating SNR problem has gone away, coincidentally with the neighbours downstairs moving out??

The lower profile thing makes sense - too bad if you're on the borderline though. These IP profiles are one of the most stupid things I've ever encountered to be honest - why can't they just dynamically set an IP profile that is say 10% less than your connection speed at sync time, and have done with it.. I'm sure it would take much less processing power than all this complicated DLM stuff that doesn't work properly!

Btw, any questions about Be, ask away... although I shouldn't think there's that much to ask .. plug n go!

About the only thing I can think of is if you've opted for static IP? In which case if you don't receive your letter before you get switched over you'll have to phone the support desk to find what details you have to put into the router. It's not the same as BT - it's essentially a routed ethernet over ATM connection, no PPP involved. So you have to manually specify static IP, DNS servers etc in the router setup. But the support desk will give you the info straight away, or at least they did with me

[DrTeeth]

@mr chris

Thanks for the offer of help. I have indeed opted for a static IP. I'll use the Bebox for a short while [just to get stats; hope to cancel DLM and get fastpath ASAP] and I have just bought a new DG834GT which I hope to test with my current connection, just to check it works.

Funnily enough (cutting a longish story short), I'm going through a 12 dB phase. But after a year or so of 5500 profile sync speeds with a 6dB SNRM, using several routers; I got home today and found some strange stats. It looks like I should be able to comfortably get a 6000 profile with the standard 6dB - a too late present from BT wholesale methinks.

me/ Note to self...keep Be's phone number safe if I need to phone and have no connection.

[mr_chris]

> a too late present from BT wholesale methinks.

Typical Oh well, count yourself lucky, they didn't give me anything as a leaving present! Mind you, whatever's happened, perhaps they've fixed a bad joint at a cab / pole somewhere... it'll only serve to up your ADSL2+ speeds with Be

[Ezzer]

With the how many day's thing. the following may clear some stuff up


 The 10 day stabilisation period

What is the 10 day stabilisation period and what is it for?
The 10 day period is to allow DLM to re-profile the line, in order to stabilise it and to determine the MSR.

What actually happens during the 10 day period?

DLM collects performance data and determines the stability of the line. If the line is unstable, it re-profiles the line and then monitors it again. This process repeats until the line is stable and can take up to the 10 day to complete.
During the 10 day period, Max tracks the lowest BRAS rate and once the period is complete, the MSR is set accordingly.

What happens once the 10th day has passed and the MSR and FTR are set?

Max and DLM continue to work every day even after the MSR and FTR are set. If a line becomes unstable after the 10 day period DLM will still attempt to stabilise the line in the same way that MAX will continue to change the BRAS profile if the line rate fluctuates after the 10 day period.
The MSR and FTR are purely for reporting purpose as described below. The MSR and FTR are fixed after the 10 day period, unless a recalculation is triggered by BT Wholesale Broadband Assurance. This initiates a new 10 day period, purely for the MSR / FTR calculation.

What happens if I do not use my modem until (e.g.) the 7th day?

The MSR and FTR will be set after the 10th day using the data available since your first log-in. DLM will continue to try and stabilise the line as described above if necessary.

What happens if I’ve been on holiday and haven’t used the service in the first 10 days?

The MSR and FTR process uses a 10 day rolling window in order to capture circumstances like this. Stabilisation will occur as described in the answers above. See section 7.2.

Does this mean I’ll get the same Line Rate when I retrain the modem after the stabilisation period?

Not necessarily. Broadband Max is a rate adaptive service and will always try to sync up to the highest line rate your line can support reliably. When you sync on subsequent occasions you may experience different Line Rates. The Line Rate achieved is dependent on a number of factors including line conditions and any local sources of electrical interference (see the section on REIN). Line conditions can be affected by weather conditions such as rain or prolonged dry periods. Electrical storms can also have a significant impact on line rates you may achieve.

[roseway]

Thanks for that very clear description of the process, Ezzer. Very much appreciated.