One of the main issues with doing a full DLM reset is that if a line does have underlying issues, you're essentially creating a period of instability while the line is reassessed.

A perfect example of this is someone with multicast service delivered over their FTTC line. A customer wouldn't be particularly happy if their line drops out multiple times during a football match or film because their line has been reset.

A valid point, though on the other hand it offers the opportunity to prove/show something may not be right. In my case I had excessive downstream error seconds at one point, in the many thousands within 24 hours. It was pretty much almost 1 error second every few seconds.

I've had some engineers who admit that interleaving is used as a method to mask a potential line fault even if the standard line diagnostics such as CIDT don't immediately show a problem, instead of the engineer being allowed to do a little further investigation. I realise there's time and resource constraints too, but yeah.

Probably a year or more ago now, I moved from a 40/10 service to an 80/20 knowing that my line was capable of syncing at over 50,000. I was willing to pay an extra couple of quid for a 10Mbps boost.

My connection speed, however, remained stuck at exactly 40,000. When speaking with my ISP, I was informed that an engineer visit would be required in order to reset this locked speed.

Fast forward to October 2017, and to my surprise one day my line was connecting at over 50,000 (currently over 54,000). My internet speed on speed tests also went up over 10Mbps to around 48Mbps. Clearly at some point the restriction on the line was removed - maybe as part of some upgrades to their FTTC equipment? Currently stable for over 60 days at the same line rate.

Whatever happened required no engineer visit to me and I am pleased with the increased speed. I guess that they do review or remove these things every so often whether automatically or manually.

jayteedc

This happened to me once, I think DLM can eventually decide to remove the banding but it takes a very long time to do so. The other possibility is a change in backhaul, this will effectively trigger some kind of DLM reset.

No disrespect to the engineers, but I've heard so many things over the years from engineers, that you have to sometimes take what they say with a pinch of salt.

DLM is a complex set of algorithmic rules. It acts on the side of caution and takes action based on the analysis of line performance from various factors. However, certain issues became apparent after Openreach were forced to re-write aspects of DLM due to losing the court case. My understanding is that one of the main things changed was the process in which people 'step up' a profile after a line is deemed to be stable.

The main reason for the introduction of a reset function was that one large ISP did some in depth research and found a small percentage of lines were stuck in sub-optimal profiles. Whilst the percentage was quite small, if you look at the cost of support for ISPs dealing with customers reporting speed issues and then the Openreach engineer attendance cost, we're talking hundreds of thousands if not millions a year.

I have had banding imposed and banding removed and all without contacting anyone, so yes it does happen.

Yes, DLM banding either ever relents, or takes a very long to...

Edited by deleted (Tue 06-Feb-18 13:03:48)

Constantly resetting might also mask an actual fault.