Sync speed drop on Haverhill exchange

Hi all,

I have been trying to find a solution to my problem and after finding this thread over at avforums....

http://tinyurl.com/mywpfm it pointed in think broadbands direction to find a resolution.

As per the avforums, I am on the haverhill exchange and until monday, synced at a stable 5Mb (sometimes 5.5Mb). After a day of slow and intermittent speeds I am now only connecting at 3712kbps.

The setup which has served me reliably for years has been a Draytek Vigor 100 acting as a PPPoA to PPPoE bridge, then an Airport Extreme connecting using PPPoE. To elimiate an internal hardware issue, I tried connecting an older Linksys AM200 which synced at over 5Mb but oddly wouldnt connect. This lead me to purchasing a bog standard Netgear DG834G which is what I am currently using and is connecting at the 3712kbps. I have also tried a selection of microfilters and different modem cables.

Interestingly, I temporarily reconnected the AM200 with no config changes and it synced at only 3.5Mb, and unlike the other day, connected just fine! VERY ODD!

We have a single master socket (non NTE5) with no extensions and no bell wire and the line stats from the Netgear are as follows:

Line Attenuation: 45.0db down / 31.5db up
Noise Margin: 14.7db down/ 19.0db up

Does anybody have any idea of what could be causing this problem, as the frustrating thing is the BT line checker says our line should only support 4Mb and I am worried that BT will say that our connection is fine.

Cheers,
Andrew

p.s. we are with fast.co.uk but they seem to be rather unusually un-proactive on helping us with this issue.

Looks like your Target SNR has been increased - this lowers your connection speed...

Do you monitor your line stats so you can compare things?


I'm also suffering from a deteriorating line and getting help isn't easy I'm afraid to say!

I don't monitor the line stats but I had an feeling that our target snr had been increased.

Interestingly, after a stack of disconnections and fiddling around with trying different modems, our speed suddenly dropped from 5Mb down to 3.5Mb.

Do you think that this will increase again after a few weeks of no disconnections? Is there anything I can do to get the target snr adjusted back again?

Your 'target' should reduce automatically after a few weeks if the line appears stable (sync/error count) to BT's systems.

This does work but you have to be patient and people aren't always successful.

You can try asking your ISP to intervene - some are better than others at facilitating this!

I would give it 3 or 4 weeks first to see what happens.
Start using RouterStats or similar to monitor your connection...

Just a quick update - our ISP is requesting a training period be rerun from monday (now that I have replaced all the internal equipment).

Hopefully if there was a temporary condition on the line or any of our previous equipment was wacky, the retraining will get our sync speed back.

Thanks for your help b4dger! fingers crossed

Edited by preppeller (Fri 31-Jul-09 10:47:02)

Good luck - remember to update us later...

Well the training period came and went, the modem didn't disconnect by itself once (I expected it to do so in trying to find the maximum achievable connection rate) and we are still connected at 3.5mb instead of 5+.

What would you expect to happen during retraining? What would you suggest our next step be? (I've already just popped an email over to our ISP).

It doesn't sound as if your Target SNR has changed.

Have you been monitoring your line stats since you last posted?

In theory you should have initially seen a default 6db Target when your 'retrain' started with this changing if required to stabilise your line.

I would restart your router and post your line stats immediately after the restart.

Thats what you expect from the training period, not all the myths that are passed around..

i.e. everytime an ADSL modem it connects at the best speed it can on a rate adaptive service, with the BT Wholesale services if disconnects and reconnects a lot they will raise a figure called the target noise margin to slow you down, i.e. trade speed for stability