Tweaks to the way the Dynamic Line Management (DLM) works for VDSL2 (Fibre to the Cabinet - FTTC) are on the way in 2017. It appears that those people with stable VDSL2 lines may be see an increase in speeds as lower target noise margins of 3dB, 4dB and 5dB will be made available.
The current minimum target noise margin is 6dB, thus allowing lower margins will potential give people a couple of extra Meg, and for those on the 1 to 1.5km type line lengths any extra speed will be welcome and it may bring some up from 22 Mbps to the 25 Mbps region. This is not a setting that you will be able to request but the DLM system will determine if a line appears stable enough and then try a lower margin and if the error rates don't increase the new setting will stick.
The information comes from a suppliers information note (SIN 498) which describes the Openreach VDSL2 service and March 2017 is the current date for when the DLM will change. For those who feel the need for speed, it should be pointed out that the lower margins are only going to be applied to those who see a stable connection at the existing 6dB margin, so if you are running on a 9dB margin currently the change will not impact you.
Myths around the Openreach DLM still persist, but the general rule is that the line starts off life at its fastest and the DLM will do most of its major changes in the first 48 hours of a VDSL2 line going live, but thereafter the DLM continues to run and will react to changes in conditions and while reactions to increase stability are generally fast, things like giving back speed after a period of instability can take a few weeks.