Last update 25 June 2011

BT Dynamic Line Management runs constantly on BT Wholesale based ADSLx.

It monitors connections and disconnections, error rates, and no doubt many other things as well, but those are what concern us.

The two main things it sets are the “target” noise margin and the IP Profile. Please see the links in the menu on the left for details.

Because of the DLM it is very important not to disconnect and reconnect frequently as it takes that as instability and increase the target Noise Margin. Even before it takes that step it will turn on Interleaving if that is set to Auto and the line is on Fast Path at the time.

It appears the number of disconnections/reconnections in an hour to trigger a target SNRM rise is still the original 10. I wouldn’t rely on this myself, and I wouldn’t be surprised if Interleaving switch-on were not more sensitive.

If the target noise margin gets raised above your normal figure for any reason, (the default value is 6dB), see Unstable lines and High Noise Margin in Troubleshooting.

If interleaving gets turned on and is normally off with no trouble then you need to contact your ISP’s support to have it reset. Unless you are an online gamer or normally connect at 8128kbps and are reduced to 7616kbps then I would leave it on as it can improve throughput.

Note: The DLM on 21CN WBC seems to have problems on some (ADSL2+) lines, reporting wierd and impossible IP Profile settings and other oddities.

Update: The oddities appearing on some ADSL2+ lines is apparently due to trialling of a new DLM system which it seems has much more rapid updating, (almost immediate), works on a straight percentage of connection speed instead of range banding, (possibly 88%), and is also more tolerant of noise margin changes.

Copyright © RobertoS 2009-2011

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