Summary. While waiting for a DLM speed increase, reconnect the router each morning.
The IP profile reflects the synch speed, DLM influences the synch speed.
The sync speed is effectively controlled by DLM as part of the low level cabinet->modem connection. The IP/BRAS profile is established from the sync speed as others have said above.
However, this does not happen completely automatically, it only happens when the router establishes a new pppoe connection.
A change of sync speed always involves a new connection from cabinet->modem. Sometimes, as the connection is broken at the lower cabinet->modem level, the pppoe connection is lost at the higher (router->exchange) level. Once the lower level connection is reestablished at the new sync speed, the router makes a new pppoe connection and a new IP/BRAS profile is correctly established.
However, quite often the reconnection at the lower level happens so quickly that the higher level connection does not notice the drop. The pppoe connection is not broken and does not need to be reestablished, and the IP/BRAS profile remains at its previous level, matching the old sync speed. This can be resolved by manually disconnecting and reconnecting the router (not modem); preferably using the web interface, or alternatively by resetting or power cycling the router.
When hoping for a rise in speed, it is worth reconnecting the router each morning; DLM usually schedules sync speed increases overnight. The speed you see is effectively the lower of the sync speed and IP/BRAS profile. Where the new sync speed is faster than the old, you will be left with a lower IP profile which will artificially keep your speed down. Where the new sync speed is slower than the old, it will be the sync speed that limits you. Reconnection will lower the IP profile, but won't lower the speed you actually see.
There is never any harm disconnecting/reconnecting the router. The router reconnection is not seen by DLM; unlike power cycling the modem which can be seen as an error by DLM. As FTTC connections are often very stable for months at a time, you could suffer unnecessarily low IP profile and speeds for such periods after a DLM increase if you do not reconnect at the router level.
As also mentioned above, the DLM rise in speed can take two to three weeks; DLM is very keen on making sure of stability.
--
Moved (with trepidation turned relief) to BT Infinity 2 for upload speed. Happy BE user for several years.
Edited by StephenTodd (Tue 12-Feb-13 09:48:17)