i was reading another forum and i saw this:

what is interleaving?
interleaving is part of dls and is a method used to maintain stability of the line if errors occur. in short it helps maintain service if your line develops issues. If interleaving is used it will increase your ping round trip time by 20ms-40ms. this is a setting made on the line card profile on the bt adsl equipment at your local exchange.

This profile can use one of three options:
auto: The line will run in "fast mode" (interleaving off) unless it sees an issue and will opt to interleave to try and keep the service going. If your line then stabilizes the line card profile it will then switch back to fast mode automatically.
on: The line will run with interleaving on all the time.
off: The line will run permanently in "fast mode" and will be unable to apply interleaving to maintain the service if errors should occur.



do nz isp's offer the 'auto' option? my understand is that if you have it in auto mode and something goes wrong it will automatically switch interleaving back on and then turn it off again.