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However, this is the jist of it:-
DLM constantly monitors & manages connections for as long as the product exists in order to balance speed & stability.
When first installed, the connections starts on a wide open profile, allowing US & DS speeds to run at the chosen service's upper limit
DLM will intervene if severe instability is detected during the first day of service.
Otherwise, it will will wait until the 2nd before deciding if intervtion is necessary as long as the connection has been in sync for at least 15 minutes during the first day.
If DLM does intervene it will set a profile with a maximum rate and a minimum rate, where the minimum rate is set at approximately half of the maximum rate.
The reason for the minimum rate is to ensure that the line does not train at a rate significantly below the level the line should be able to achieve. If this happened, the line is likely to remain at a very low rate until a re-train is forced by the user by powering off the modem.
We have experienced 'stuck' profiles, sometimes for many weeks, even following engineering works where the source of the initial 'fault(s)' have been eliminated.
On these occasions, an engineer visit is required to check line conditions again & assuming everything is still O.K. a DLM reset (or re-calculation) can be requested by the engineer.
DLM sets the line profile, and this should not be interfered with by ISPs/users setting rates, SNR margins etc. at the modem.
Indeed, with only one exception that I am aware of, any attempts to tweak SNR and/or sync speeds via the modem have been unsuccessful.
Despite monitoring quite a number of connections, we still don't really know what is classed as instability severe enough to cause DLM to take corrective action on day one.
We are also unsure of the details of what causes DLM to take action at other times (usually between 04:00 & 06:00, when it is assumed a resync at a lower speed, possibly applying interleaving will have the least disruptive effect).
e.g. following a recent engineer's visit to investigate sustained lower speeds, DLM was reset/re-calculated at around 16:00 on this profile for my connection:-
0.128M-40M Downstream, Interleaving OFF - 0.128M-10M Upstream, Interleaving OFF
Actual sync speeds were only DS 20308 Kbps, US 4872 Kbps
According to my connection stats, DLM kicked in at 04:45 the following morning, setting this profile:-
12.5M-25 Downstream, Interleaving OFF - 3M-6M Upstream, Interleaving OFF
DLM then set a slightly lower profile at 06:15 the same morning, :-
12.5M-25 Downstream, Interleaving OFF - 2.5M-5M Upstream, Interleaving OFF, which Plusnet advise me is still active.
It is currently in sync at DS 19023 Kbps, US 4333 Kbps.
So, a few infrequent resyncs during day one will probably not have much of an effect & it would be 'useful' to grab some connection stats for baseline data, just in case.