DLM Logic

Does anyone know the precise circumstances that lead to DLM adjusting the target SNR margin on a line?

For example - does it monitor CRC errors on the line - if so, how many over what time period would cause DLM to adjust (upwards) the SNR target?

Similary - do DSL resyncs (perhaps caused by the end user powering on/off or otherwise disconnecting the router) casue DLM to adjust SNR? If so - how many over what period?

Thanks

I'm afraid BT haven't published those figures!
Sometimes just looking at your router in the wrong way can cause Target SNR issues!


The only thing they do mention is in their 'Myths and Legends' document (a few years old now) that restarting your router 10 times in an hour will cause the DLM problems:

BT:
How many times can my line retrain per day before DLM acts?
This is a BT Wholesale configurable parameter, but currently if a line retrains more than 10 times in any single hour period DLM will take action. It is therefore inadvisable to manually retrain a line more than 10 times in a single hour as DLM will interpret this as line instability.

EDIT: TBB link to BT's Myths and Legends http://forums.thinkbroadband.com/btsupplier/f/319138...

An update on this document would be good!

Edited by b4dger (Wed 06-Oct-10 16:23:36)

The ten still applies, I think the error rate varies, i.e. there was talk of if they saw large numbers of errors in an area for a short period they would not trigger margin rise, e.g. electrical storm.

I remember getting caught out in the past with storms racking up the errors and the TSNRM taking a hit - actually it was you who helped me out with this when my provider couldn't! So thanks again


It would be great if you could manage to get some updated docs from BT...

On Max I don't think much has changed.

WBC I need to dig through inbox, believe I have something somewhere.

Is it possible to force your SNR lower via telnet / DMT on ADSL2+ or is it overruled by the BT systems?

If you mean with things like DGTeam firmware on routers - not up to speed in that area, so best to wait on someone who is

In reply to a post by stephen79:

Is it possible to force your SNR lower via telnet / DMT on ADSL2+ or is it overruled by the BT systems?

Some O₂ LLU customers seem to try it out for a faster connection > link