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Author Topic: FTTC DLM - Change of MTBR  (Read 7898 times)

kitz

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FTTC DLM - Change of MTBR
« on: June 20, 2015, 01:05:42 PM »

Last night I saw a post by AndyH on the PN forums.

Credit to him for posting, I think there may be some fact in his statement and some misinterpretation as he's saying

Quote
Interestingly, there was a DLM change made on Tuesday to the MTBR threshold. It's basically been halved for all DLM profiles: 

                   Old Threshold           New Threshold   
Speed          8400                          4,200
Standard     16,800                        8,400
Stable          33,600                      16,800

I have asked for clarification and to check.  Whether he will respond or not is another matter because I believe the information should actually be interpreted as

Quote
               Green     Red
Speed       8,400     4,200
Standard   16,800    8,400
Stable       33,600   16,800

This would make far more sense as it brings speed profile nicely in line with the other figures which use half of red for green.
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kitz

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Re: FTTC DLM - Change of MTBR
« Reply #1 on: June 20, 2015, 01:12:03 PM »

Reasons why I suspect it should be  red/green and someone else has typed old/new above

- Posting one set of 'new' parameters is a bit useless without its opposing pair.
- What is said to be the old thresholds don't appear to be from the last figures we had.
- The new figures are very similar and only speed changed slightly


These were the previous figures that Ive quoted several times on this forum in the past - and theres even a copy of the NGA graphic I posted last year dotted around these forums in a few places and the ones Ive been using for about 10 months for the DLM calculator.

Green   Red

 8400   4320
16800   8400
33600   16800


Oh and in case anyone doubts me, the Zen training doc also confirms those old figures.   I think this may be another example of him getting some good info, yet unfortunately he's put his own interpretation on it and turned it into meaning something else...  because those dont appear to be the old thresholds... but green.

All the change has done is brought 'speed' into line with the other profiles in that Red is half of green and now makes 20 resyncs supposedly safe rather than the previous 19.
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kitz

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Re: FTTC DLM - Change of MTBR
« Reply #2 on: June 20, 2015, 01:14:33 PM »

What do the changes mean?     Aside from bringing speed in line with the other params, it just now means a rounded 20 per day for retrains.

I will change the MTBR RED figure in the DLM calculator but it doesnt make much difference as basically all the parameters are the same as the previous set we had. 
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les-70

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Re: FTTC DLM - Change of MTBR
« Reply #3 on: June 20, 2015, 03:14:00 PM »

   I do wonder over the MTBR figures.  To allow 20 a day even on a fast profile seems nuts to me.  I wonder who would accept say 10 resyncs a day as possibly OK???.  Most people get very upset at a few resyncs a day.

  I am with TTB and supposedly on the standard (middle profile) and I am definitely hit when/if I go over 5 resyncs a day. It has happened twice when I have been messing around while thinking it might be 10 a day.   For errors the limit is definitely a MTBE of 60 which is consistent with standard. I have got away with 50 and been DLM hit at 70.   Maybe TTB has an odd hybrid profile but I suspect not.
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kitz

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Re: FTTC DLM - Change of MTBR
« Reply #4 on: June 20, 2015, 05:06:50 PM »

We've discussed about this in the past and I agree with you that 20 doesnt always seem to fit with what we are seeing.  Each subsequent release of any MTBR figures always seems to be higher than what can sometimes happen in reality
 
I think I've also mentioned to you before about the little known or talked about 'Scarlet ILQ'.   I cant find much info about this other than what is on the Plusnet site where there is a very hard to see graphic



Note on there the mention of 10.  OK things may have changed but what I have found in BT documentation is classification of a 'Very Poor' status (separate from MBTR red) whereby DLM will react quicker if several retrains are detected in a short period.  I dont know what is classified as short period, but it leads me to believe that obviously its not over the usual MTBR daily period.       

Perhaps it could be something like 10 in an hour (or 2 hours?) for speed, and if they do half things like they usually do for standard then that would equal the 5 you mention you are seeing.   Can't find anything about this now and everything is locked down tight since ASSIA case :( 

Ive been asked a couple of times in the past week or so if I'd release what info I had got and although Ive always made the page available to members from here, Ive just never linked to it on the main site, because it was specifically the ILQ scarlet and steps to remove DLM where things had come to a halt and these I wasnt sure about.
I think the best thing to do is gloss over those 2 areas, because nothing new has come to light during the past 10 months and it seems stupid holding back on other info such as wide area events etc which I am certain about. 
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NewtronStar

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Re: FTTC DLM - Change of MTBR
« Reply #5 on: June 20, 2015, 05:45:22 PM »

Kitz how do we know which profile the ISP is using IE: Speed (1) Standard (2) Stable (3) at a guess this line has been moved from Standard to Stable but can't confirm this.
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kitz

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Re: FTTC DLM - Change of MTBR
« Reply #6 on: June 20, 2015, 05:49:40 PM »

I dont know what EE are using.

The only ones I know for sure are listed on the bottom of the DLM calculator.

BT is a weird one...  because someone said BT will change Speed/Standard upon request.    It is possible for the ISP to do that so Im not sure.
jid asked TT (his ISP)  which is how we know what they use.
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kitz

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Re: FTTC DLM - Change of MTBR
« Reply #7 on: June 20, 2015, 06:35:37 PM »

PS - afaik none of the ISPs are using stable.
Most supposedly use Speed, and TT is the only definite case we have of Standard.

You could try asking them?
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jid

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Re: FTTC DLM - Change of MTBR
« Reply #8 on: June 20, 2015, 08:22:28 PM »

All I can help you with in terms of EE, is that the TalkTalk rep passed on from the FTTC Product Manager that most ISPs use Standard as its the most popular profile, so you could assume you're on that?

Here's the info again for reference to the above fact:
Quote
"On Fibre, Openreach owns the DLM. They over several profiles (Speed, Standard, Stable). We use the Standard one as it's the one that delivers the best speeds with a good element of stability. I believe this is the one most used by ISPs but can't confirm what BT Retail uses."

Also this they stated:
Quote
CPs (ISPs) do not have any control over the DLM OR provide for FTTC other than to change the policy (speed/standard/stable).
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Terranova667

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Re: FTTC DLM - Change of MTBR
« Reply #9 on: June 20, 2015, 09:55:56 PM »

@kitz AndyH has responded in his typical manner.  ::)
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NewtronStar

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Re: FTTC DLM - Change of MTBR
« Reply #10 on: June 20, 2015, 11:20:38 PM »

Here's the info again for reference to the above fact:
Quote
"On Fibre, Openreach owns the DLM. They over several profiles (Speed, Standard, Stable). We use the Standard one as it's the one that delivers the best speeds with a good element of stability. I believe this is the one most used by ISPs but can't confirm what BT Retail uses."

Thats good and maybe i was moved from speed on BT to Standard on EE and this is what i seen 1500 errored seconds per day with maybe the odd 2200 on BT for months since DLM reset 13th of FEB once switched over to EE on the 13th of MAY the errored seconds got close to 2000 for one day and the DLM intervened.
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kitz

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Re: FTTC DLM - Change of MTBR
« Reply #11 on: June 20, 2015, 11:44:51 PM »

@kitz AndyH has responded in his typical manner.  ::)

Yep I saw and responded back. 
We know for a fact those figures were in use at an earlier time.    The only explanation is sometime between ASSIA/G.inp they changed them, and perhaps it was too high & caused issues, so now they are changing them back again.

@ Les I found this which supports the separate quick succession theory.  Its specifically about speed profile so presumably will be halved for Standard

Quote
A line would need 10 retrains or more in any rolling 1 hour period to be flagged. This process is independent from the daily DLM process.

Its not linkable Im afraid, but happy to send a screen grab via PM if in doubt... but it doesnt really give any more info than that.   
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les-70

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Re: FTTC DLM - Change of MTBR
« Reply #12 on: June 21, 2015, 07:21:22 AM »

@ Les I found this which supports the separate quick succession theory.  Its specifically about speed profile so presumably will be halved for Standard

Quote
A line would need 10 retrains or more in any rolling 1 hour period to be flagged. This process is independent from the daily DLM process.

  That would be sufficient to explain my events.   I will assume it is true ----- as testing the DLM can require more than my patience before normality returns.
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Mark07

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Re: FTTC DLM - Change of MTBR
« Reply #13 on: June 21, 2015, 03:33:43 PM »

SO kitz, in laymans terms what does this mean for us, the end user?  :)
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kitz

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Re: FTTC DLM - Change of MTBR
« Reply #14 on: June 21, 2015, 08:46:23 PM »

SO kitz, in laymans terms what does this mean for us, the end user?  :)

Not a lot really, just that if you are on 'speed' profile then the system should be able to cope with a full 20 resyncs per day without kicking in.
There still is the scarlet (very poor) process though which looks for 10 syncs within an hour (speed).  Im afraid I dont know what it is for standard.
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