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[adslgeek]

Hey there,

I was curious to hear feedback on how much of an impact Dynamic Line management was from a support perspective (I understand that BT had introduced it a while back?).

Did it make things faster and more stable? Was it worthwhile investing in, or was it a nice to have?
Also keen to hear feedback on virtual noise - did it make a big impact to helpdesk loads?

Cheers,

[sevenlayermuddle]

I suspect you'd rather hear from ISP support people (I'm not), but the following - which is just my own view - may be of interest...

One problem that I know to affect DLM, feeding thorough to ISPs and BT,  is that in can in some cases make an inappropriate decision to raise a target margin.   In that event, the only way to get the margin put back in any sensible time frame is for the consumer to ask his ISP to ask BTw to apply a manual override.  Many (not all) ISPs struggle with such a request as it's not in their script, and BTw don't seem to like it either.  I'm guessing BTw never anticipated it happening when they dreamed up DLM.

There are various scenarios for DLM making a bad judgement, including for example, transient electrical storms that cause temporary instability.  The one that I personally think should be taken more seriously however, is vulnerability to consumer-error, in the form of too many router resets in a given time, which DLM mistakes for major line instability.   I believe the threshold is ten resyncs in one hour.   This can happen quite innocently if, say, a consumer is trying out a new router, and may want to try a few different syncs with old and new router for comparative purposes.   BT's DLM, in this case, actually pushes the line up two notches on the target margin, e.g. from 9dB to 15dB.  But as stated in previous paragraph, the only official way of getting it fixed involved major hassle for all parties - consumer, ISP, and BTw alike.

In reality of course, many consumers faced with that scenario,  instead of approaching their ISP, find it easier to get hold of a router with a tweakable margin and so effectively bypass DLM.  For tech-savvy users that's not too bad, but I wonder how many ISP support people end up tearing their hair out when they find somebody tweaked the margin on a line that has genuine need for a higher target, and then face an uphill struggle asking the customer to undo the tweak?  And even for tech savvy users it's problematic, because one day in the distant future DLM may reduce the target again, and unless the user quickly notices the change,  and reduces the tweak to compensate,  they may be faced with an unstable line.

[general disquiet]

DLM is possibly (I remain to be convinced) useful in situations where there is constant, or near constant, instability on a line.  In that case, it might help establish a constant sync.  However, the other situation where it makes matters much worse than they need be is when a line is hit with a single burst of interference (eg REIN), perhaps on a daily basis, or a few (less than 10 say) times a day.  In these situations, no matter how high the SNR is set, nor how low the IP profile drops, routers will still lose sync when the REIN hits.  All the DLM achieves is a lower speed for the customer for the other 23 hours 59 minutes 59 seconds and a few hundred milliseconds a day when there is no problem with the line.

[waltergmw]

Sorry to be a bit of a long playing record but the following is AAISP's suggestion:- (Note they're suggesting Disabling 21CN BRAS as well.)
http://aaisp.blogspot.com/

Kind regards,
Walter

[sor] 11098 Control of MSAN profiles

Basically, we are asking BT to let us turn off their DLM (Dynamic Line Management) on any lines and give us direct control over the MSAN profile in use on a line.

Importantly, we need the control to be instant, or as close to instant as possible. It may go in a queue for BT to action, but we want it to happen promptly and not take a working day to change as now.

This would give us the same features as the competition we use, BE, as they let us change profiles whenever we like will immediate effect and we pass that control on to customers. We will do the same if BT offer this feature.

At the end of the day we expect most customers to be happy with the DLM. We know it can be a pain, but for most people it is probably fine. Its the exceptions we want to manage - where the DLM cannot cope, and where our customers want control themselves.

[kitz]

In the UK the BT Wholesale DLM is probably the most well known (and patented) but even the LLU providers here use some form or other of their own DLM.

On the whole it probably works very well for the inexperienced type user to keep their line stable, but as SLM says, it can sometimes be easily tricked into being increased and it can be a bit of a nighmare to get it reduced back.. probably because of the 3rd party problem and the ISP being in the middle.  A lot of more tech savy end up SNRM tweaking via the router.
I do see quite a lot of complaints from inexperienced users who complain that their router looses sync each night.  Once the DLM cuts in and increases their SNRM/interleaving etc, then they are happy that the line is stable. 

Personally I like the way that LLU provider Be let their users actually configure/over-ride via their user control panel.
There is talk of BTw eventually putting in basic user config over-rides into their 21CN network.