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Author Topic: FTR in ADSL  (Read 215 times)


  • Senior Kitizen
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  • Posts: 11041
  • Retd s/w dev; A&A; 3x7km ADSL2 lines; Firebrick
« on: April 16, 2022, 05:34:40 PM »

On this page,, Kitz wrote:
Fault Threshold Rate.

Once your MSR has been set, BTw use this figure to calculate your Fault Threshold Rate which is in the region of 70% of your MSR. BTw will only investigate speed related faults if your speed drops to below the Fault Threshold Level.

I wonder why this says Ďin the region ofí ? Is it calculated as a variable fraction of some agreed max rate? I thought it was just 70% of the <whatever/> max, but I donít know where I got that from, probably from this page but I never noticed that imprecise wording.

AAís definition of FTR in their web pages seems to be just under 80% (~78% ?) of an older long-established max sync rate. They light up an FTR error message in a list of problem lines if a downstream synch rate goes too low, It could be based on the MLF (max load factor) as I term it, fraction of the max at which they drive the ingress into a link, and that is currently set to be 98% so if so that would explain the fact that it seems to be a bit lower, about 2%, than the round number of 80%. (That sounds like a bug to me.) I could ask them. Iím surprised that itís doesnít match BTís definition of 70%. Anyway, they consider downstream synch rates of around 78% below max sync rate to be a fault. They list all slow lines at the top of the main page in so you can see at a glance which are the problem lines if any.