The guy who visited me was adamant that one ISP (in his case SKY) had done DLM resets in the past where perhaps it was inappropriate and caused him problems because the reset masked the issue and left him with no errors, he was also adamant that other ISPs could do resets but some may either deny this or be reluctant to either do it or admit it.
That sounds more like he was talking about an
LLU ADSL line. Sky have their own LLU DLM for ADSL2+ which they can change themselves.
It is the
only explanation why the OR engineer would say it masked the errors. OR engineers have no control over Skys LLU DLM.
This isn't the case with VDSL though as DLM is controlled by Openreach and can only be reset by Openreach.
The Openreach NGA DLM can be automatically 'reset' by a change of product. A change of product includes moving between an ISP that uses speed profile and one that uses standard profile and vice versa.
However that said, I suspect there may be 2 types of NGA DLM reset.
- The one done by OR engineers which take the account back to the Open profile.
- The one automatically done by a product change.
The later one does not always appear to be a full reset. Whilst it may clear things like G.INP/Interleaving.. it does not appear to remove any banding which may have been previously applied to the line.
Ive discussed this in more depth in another thread when I first made this observation... and its why I originally started another thread asking for those who appear to be stuck with a banded line as I wanted to see stats. I was hoping to take it further with someone at Openreach, but things have changed since I started that and its not anything I envisage taking up in the near future as Im afraid its had to go on the priority stack.