Confusion - Sync Speed

For the first few weeks on my 4meg connection I synced very close to 4Meg consistently.

I am now out of my 10 day period.

However, this weekend (I was away) I had a few power cuts and my connection naturally dropped on each occasion.

Now I am syncing about 1/2 a meg lower.

So, yesterday afternoon I rebooted my router and rather than syncing higher, it dropped. I thought, ok I will try tomorrow (today) morning.

So this morning, I rebooted the router and lo and behold, I am syncing even lower.

This is odd as, if during the evening my sync dropped any, I would merely reboot the router the next day and it would increase again.

Obviously this has something to do with my understanding (or lack thereof) of the Max product, so, any pointers would be gratefully received.

What are your line stats?

Think the problem may lie here...

"However, this weekend (I was away) I had a few power cuts and my connection naturally dropped on each occasion. "

If you drop the connection without manually disconnecting the Modem connection (in the tray on your screen) the connection at your exchange thinks the connection is not working reliably at that speed, so it drops your speed in an attempt to supply a reliable speed.

You may have to ask your ISP to arrange another BT speed test over 10 days to reassess the speed.

Hope that helps,

Mike.

I am sure I read somewhere that if ones sync drops overnight, rebooting (rather than dropping the connection) will raise the sync speed due to a better SNR and this has worked in practice up until recently.

My line was stable at just under 4meg so it seems rather odd that a few blips should affect this but I guess I just need to make the case with the ISP?

Atten of 49.5, SNR between 5 and 9 depending of the time of day.

Stable at 3.9meg for quite some time.

Looks a fair speed for attenuation and SNR. Your SNR fluctuates, as you say between 9 and 5, but there is alevel below which the ADSL system will not let it go, possibly about 5 - after thsi, it just cuts speed to keep the SNR above a particular level

I think what I am getting at is, the behaviour yesterday was "abnormal" compared to previously where speed had increased after a daytime reboot of the router.

Oddly enough the router has never disconnected when the SNR has been in the 5-6 region.

In reply to:

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Oddly enough the router has never disconnected when the SNR has been in the 5-6 region.

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Sounds right. It reduces speed, by dropping frequency bins, to keep the SNR at or above a certain level. Yesterday for whatever reason, your noise environment was probably worse than normal, hence a significant slowdown

So, any idea how I get it back up again or is it a case of begging the ISP to retrain me?

...the connection at your exchange thinks the connection is not working reliably at that speed, so it drops your speed in an attempt to supply a reliable speed.

That's not how it works, at all.
The exchange has no say over your connection speed, other than by instructing the router to connect at a given noise margin (3,6,9,12 or 15db - the default being 6db).
The only thing that determines sync speed is the router.
As it would seem the OP has only suffered a few re-syncs, it seems unlikely the noise margin target increases each time he re-syncs. It takes a good many re-syncs to trigger an increase in the target margin (loads for the first increase, from 6 to 9db, but seems to be less for each subsequent increase).

Depends what your target noise margin is.
If the noise margin/SNR immediately after a re-sync is 9, 12 or 15db, then you've been subjected to an increase in the target margin, to increase stability.
If you stay connected (without any re-syncs at all) for more than 14 days, the system should, but probably won't, drop the target margin by 3db.
So, you should eventually get your speed back.
Never happened to me, I needed manual intervention.
If yours doesn't go back on it's own, you can ask your ISP to have your line re-trained, or your target noise margin reduced to 6db, but I doubt if it'll work.
The only sure way to get it fixed, is by regrading to a product that will force a line re-train (such as back to fixed speed, or from a home to office product).

Is there any way I can determine the required noise margin?

When I rebooted the router yesterday afternoon it was at 7.5 and dropped from something like 3.6meg to 3.2 meg, whereas before if I had been at say 3.2 meg and rebooted with a 6db SNR it rose to between 3.5 and 3.9.

The frustrating bit is that for the most part, it lingered at around 3.8 to 3.9meg in a relatively stable manner and I would like to get back to that.

Well I think the only option is for me to ask for a retrain or drop in target margin as from what I gather, Demon are not the most flexible when regrading products, especially in the first 12 months.

Is there an easy way to determine my target margin?

To be able to tell, you need to know the minimum SNR margin that your router will reliably operate at, then add the number of dB's fluctuation (i.e. if the minimum SNR is 2dB and your line fluctuates by 4dB, then the ideal setting will be 6dB). Unfortunately every make/model of modem has a minimum level, so generally it's a case of "suck it and see".

Is there an easy way to determine my target margin?

Based on the assumption your noise margin shouldn't shift too much, too quickly, the best way is to initiate a manual re-sync, and be very quick in checking the router web-page.
Check the noise margin straight away, and take a calculated guess.
The target margins go in 3db steps (the normal default being 6db), so if you end up with something like 5 or 7db (for example), there's a fair chance your target margin is 6db.
If you're still on a 6db target margin, you need to look elsewhere for the cause of the drop in sync speed.
Here is a good place to start.

Ok, yesterday I dropped my PPP then rebooted the modem in the afternoon and managed to get up to 3.4meg sync.

So this afternoon I thought I would give it a go again and it dropped to 3.3 so I tried again and it went right up to 3.8.

Unfortunately my up sync has now gone from around 800 to 320 LOL.

One step forward six steps back

Any ideas? I know I can handle 4meg down and 800 odd k up.