In reply to a post by BatBoy:

Yes, DLM it is.

Actually, it looks like DLM has intervened upstream only (with INP=4.0 and delay=8). Downstream, both parameters look to be zero.

The modems have negotiated parameter R to be zero downstream, so none of the bandwidth has been stolen in that direction, whereas upstream, R/N = 16/64, showing that 25% is being used as the overhead for FEC in that direction. Luckily there is plenty of room.

Interleaving depth D is also set to 1 downstream, so it is turned off there.

Sometimes the modems negotiate upstream FEC to be turned on alone (ie without interleaving), even when DLM has not asked for intervention (ie delay=0 & INP=0.0);

DLM has capped the speed to raise the SNR margin.

In reply to a post by woodpeckerx:

Bipac 8800NL Hooked up on TT, think DLM is limiting as attainable shows 102084 but sync is 53980 19.8dB SNR Stats below,

Those numbers suggest that, on this occasion, the TT modem was originally synced while the BT modem was turned on (ie crosstalk was present at the time of sync).

Then the BT modem was turned off, but the TT modem was not re-synced, when the stats were read.

The result would be that the SNRM values jump a lot (19.8 is pretty high), and the calculated maximum speed would increase (as is 100Mbps+) as a consequence.

If this is NOT what happened - if the TT modem were synced while the BT modem was turned off - the it suggests DLM has intervened with banding. Your top speed has been limited "forever".

Maybe. Depends on circumstances, as described on other post.

But it is rare for DLM to intervene with banding alone.

Edit: and rare to use such a non-rounded number for the speed.

Edited by deleted (Sun 24-Aug-14 18:15:14)

The talktalk line will only sync to 53980 even when syncing with the BT modem off, the modems have been on and off so many times I guess the DLM has decided to join in, although the BT modem on its own will still sync at 79 but I think he reset the DLM on that line last Friday.

I'll be asking BTOR to reset both lines DLM when they've done what ever they plan next, hence I am keen to take all measurements and do whatever tests I can do before Tuesday.

In reply to a post by WWWombat:

Your top speed has been limited "forever".

Or 10 days, which can seem like "forever"

In reply to a post by WWWombat:

Edit: and rare to use such a non-rounded number for the speed.

I'm wrong on this, perhaps...

Looking in this NICC testing document, there are banded profiles with an upper bound of 54Mbps. The format of a profile is described on page 37; earlier on page 29 they happen to include one with an upper bound of 54Mbps (it is a re-transmission profile, so I guess it isn't active yet)

However, the profiles in that document suggest that banding of upstream happens at the same time as the downstream. If that suggestion is true, rather than being a small snapshot of a huge set of profiles, then 54/20 wouldn't be possible.

BT's own SIN 498 for testing show the same description for profiles, but don't happen to include one with 54Mbps.

Then it is indeed DLM banding ... and a new combination to chalk up to experience.

Perhaps this is indeed caused by the disconnection counter rather than the error trigger!

The simplest way to find out what is going on is to get TT/BT to do a GEA Circuit test (like here http://community.plus.net/forum/index.php?action=dla... which will show if there is any detected crosstalk or potential wiring issues.

The thresholds for DLM kicking in for retrains (disconnections/reconnections) alone are quite high, but it depends on which DLM profiles TT/BT are using:

Speed - 20 retrains in 24 hrs
Standard - 10 retrains in 24 hrs
Stable - 5 retrains in 24 hrs

If you're line is erroring also (beyond the thresholds), then the retrain count is lower:

Speed - 12.3 retrains in 24 hrs
Standard - 7.1 retrains in 24 hrs
Stable - 4.6 retrains in 24 hrs

TT line DLM seems to have rebanded overnight, now 73971/19999 SNR 13.9/15.7

BT modem has been left powered off.