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Author Topic: 20CN "Max" MSR/FTR Resets  (Read 1887 times)

aesmith

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20CN "Max" MSR/FTR Resets
« on: February 03, 2016, 12:58:45 PM »

Hi,

I was wondering how and when the MSR/FTR get set and reset, in the real world.  Just looking at my own line up until recently these were 2272/1817 which are definitely not the figures that would have been learned when the service was first installed, because at that time we only connected at 1.7meg courtesy of some rotten internal phone wiring.  I also noticed that the figures were date stamped about 7 days before our DSL actually went live, suggesting that these were some sort of placeholder figures intended to be over-written by the real ones.

More recently, during the course of an extended fault, the figures have been reset a few times.  Firstly to 3424/2739 which could in fact have been correct for the line in it's failed state at that time.   Later they changed to 288/288, and now they're showing 2272/1817 once again and again those figures don't actually correspond to real synch speeds.

Do they only get reset when specifically instructed by the ISP, or do they relearn themselves as a side effect of other action?

Tony S
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kitz

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Re: 20CN "Max" MSR/FTR Resets
« Reply #1 on: February 03, 2016, 01:31:11 PM »

2272 is the default MSR.   The FTR should be 70% of the MSR (or at least used to be at 1590)...  and the default BRAS was 2000

However its not the first time Ive seen 2272/1817  - One of weavers posts last year also showed 2272/1817.  :hmm:

The MSR is set during the 10 day training period, although your ISP can request a training reset.


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ETA

Here you go found his post.   - here.

Quote
BRAS=2000Kb/s FTR=1817Kb/s MSR=2272Kb/s ServOpt=1 I/L=I
« Last Edit: February 03, 2016, 01:35:20 PM by kitz »
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aesmith

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Re: 20CN "Max" MSR/FTR Resets
« Reply #2 on: February 03, 2016, 02:00:32 PM »

Just found an interesting note in the BT Best Practice Guide: Issue 2 ...
Quote
NB: ccSNR will initiate a new 10 stabilisation period but at the end of this the new MSR/FTR will be equal to or higher than the MSR/FTR prior to the ccSNR request. The ccSNR logic ensures it cannot be set lower than the previous MSR (Maximum Stable Rate) / FTR (Fault Threshold Rate).

This is interesting because it suggested that my changes to 288/288 and the final one back to 2272/1817 did not result from ccSNR requests, since these were reductions from the previous rates.   However there was also a case discussed on one ISP's BBS where the ISP had set the customer's line to re-learn MSR/FTR while it was in it's failed state, because they didn't believe the existing higher figures.   So maybe in spite of that note ccSNR can actually reduce the figures.
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kitz

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Re: 20CN "Max" MSR/FTR Resets
« Reply #3 on: February 03, 2016, 08:28:16 PM »

288/288 sounds like intervention on a very poor line.  In these cases the line is in effect forced into what appears to be equivalent to the old fixed rate and capped lines equivalent of 256 kbps.    The odd one used to crop up occasionally mostly on 20CN, and even the ISP wasnt aware that it had been capped.   TBH Ive not seen this happen recently, possibly because a lot of longer lines have now moved over to fttc if they can to get more speed from their line.    Unfortunately though you arent able to do that. 
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aesmith

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Re: 20CN "Max" MSR/FTR Resets
« Reply #4 on: February 03, 2016, 09:29:45 PM »

Our line has certainly never connected as slow as 288, not below 2700 or so even during the recent fault.
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aesmith

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Re: 20CN "Max" MSR/FTR Resets
« Reply #5 on: June 01, 2016, 04:27:06 PM »

Just to update this I went through the training process once onto A&A, before the process ...

  BT Test xDSL Status Check:Pass OK.pass OK. Circuit In Sync
  BRAS=3500Kb/s FTR=1817Kb/s MSR=2272Kb/s ServOpt=1 I/L=A
  THIS LINE IS STABLE AND WITHIN ERROR/RETRAIN LIMITS FOR THE CHOSEN SERVICE OPTION (ILQ=A)
  Up Sync=448Kb/s LoopLoss=30dB SNR=20dB HIGH ErrSec=0 HECErr=0 Cells=18409
  Down Sync=4480Kb/s LoopLoss=54.5dB SNR=4dB ErrSec=3 HECErr=0 Cells=46539


During the training period (the relevant line only) ..
  BRAS=3500Kb/s FTR=288Kb/s MSR=288Kb/s ServOpt=1 I/L=A

After training complete ...
  BRAS=3500Kb/s FTR=3200Kb/s MSR=4000Kb/s ServOpt=1 I/L=A

From that I'm not sure what Plusnet did, looks like the 288/288 was from a reset, but then it never completed and reverted to the default.

Also some blurb that I've seen says that on 20CN MSR gets rounded down to the nearest half meg, which matches what I see above, but does explain where the brief 3424/2739 came from.
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