I just read Kitz’s piece on BT
DLM "stability level" config options. Very useful. It is indeed confusing all the variation in naming for these and KITZ did a good job clearing all this up.
In earlier posts I have been moaning about the sporadic problems I have had with Zoom. I assume that now I’m using Zoom, I can not afford to have any CRC errors / ES at all. I mentioned earlier that my line 1 has been showing a modest number of ES, the other two lines are perfect, even on 3dB SNRM. To fix line 1 I had to raise the SNRM targets from 3 dB down / 6 dB up to 6 / 9 dB, but as I mentioned earlier for some bizarre reason, after a few days the settings revert back to 3 / 6 dB. I set these SNRM values in AA’s control server clueless.aa.net.uk and when they drop back the server still show the expected values (I think), not the true current ones - need to recheck that though. I asked AA why this strange reversion thing was happening, but they didn’t know.
I now wonder if this could be due to interference by DLM. Is that possible? We’re used to DLM interfering to slow things down, but does it do the reverse,
interfere to speed things up because the error rate is too low? Of course after a problem, when SNRM has been increased by DLM, DLM will improve speed later on after a sufficient period of time has elapsed with no errors, we’re all familiar with that, but does DLM not know that it is doing that
as a response to an earlier problem, ie. statefully rather than statelessly? Stateless design is cheaper/easier and less prone to bugs, so who knows? Actually Kitz knows, if anyone does.
I should have talked to AA about this, but it’s the weekend and I made a stupid mistake. In clueless there are two buttons, marked "Extra Stable" and "Super Stable". There is no documentation about these, nothing in the help pages. I should have asked AA exactly what they do. But anyway, stupidly, I hit the Extra button. I guessed that these might be something to do with DLM and also that "Extra" was in some way "less" than “Super". I had not yet read Kitz’ article. The sim was to reduce the level of activity of DLM and to make it aim for higher reliability, lower speed.
There is no "Normal" button, or "Standard" or "Speed" whatever it might be titled. I assume that appears when you are in one of the non-standard states. Clueless said it was putting in a change order with BT. I wasn’t expecting that. By the look of it this takes time. All the clueless buttons have vanished and it indicates that it is in a "changing option" state. The clueless log says ServOpt -2. This makes me think of option number 2 in Kitz’ table. Kitz remarks that AA uses "speed" DLM profile by default, option 1, so this would all fit. Surely it can’t require a
human with a spanner to make this happen? Is the ‘order’ and associated delay just because some service process only runs in the background once every so often? (Or maybe it has to synchronise with the timing of the internal operation of the boxes that go to make up DLM.)
Anyway, it was really stupid of me not to ask. Just have to wait now and see what the behaviour is. If all this theorising turns out to be correct, then this will be a good tip for AA Zoom users, a tip to go into the help wiki.