Some information about BTor's DLM

[andrue]

Two weeks ago a BT engineer tested my line. It was part of my ongoing problem and I don't think either myself nor IDNet wanted a line test but that's what I got. The only consequence was that I ended up with interleaving (1041) on my line and my speed dropped from 73Mb/s to 66Mb/s. It looks like the interleaving has been lifted - exactly 14 days later this morning at 5am. So that's something to think about perhaps for those trying to work out how the FTTC DLM works.

As for my ongoing problem - that's due on the 21st of April next. Unfortunately I think we have to get BTw involved and that seems to be difficult.

[Steve]

Mine normally resyncs a little later around 6am for Interleave changes, strangely mine's now back where it started from on install and it's taken 11 months for the DLM to say I can now keep it for awhile, usually it lasts for about 5 days and returns to a higher level but 6 weeks later still low latency.

[mervl]

I thought the current fault thresholds for FTTC are below 2Mbps download (presumably to allow FTTC to extend to as many as possible as BDUK rolls out to the rural areas), or a loss of line speed in excess of 25% over a period of 14 days. Does that imply that DLM should do its stuff where appropriate within 14 days - doesn't mean it will always take 14 days though. I also read, any my line seems to confirm this (and sorry to those that see a red flag), that BT seem to be adjusting DSLAMs to give priority to stability over peak speed. Seems sensible for the majority.

[mervl]

Addendum: for tech info on BT's implementation of VDSL (and those of us with more time than sense, perhaps) this might be a read of passing interest: https://www.btwholesale.com/shared/document/Products/Broadband/fibre_to_the_Connect/Handbook_and_Technical/WBC_FTTC_Handbook_Issue_8.pdf