Kitz ADSL Broadband Information
adsl spacer  
Support this site
Home Broadband ISPs Tech Routers Wiki Forum
 
     
   Compare ISP   Rate your ISP
 
Please login or register.

Login with username, password and session length
Advanced search  

News:

Author Topic: ISP's now using the 30 minute rule  (Read 1410 times)

NewtronStar

  • Kitizen
  • ****
  • Posts: 4395
ISP's now using the 30 minute rule
« on: November 03, 2016, 08:03:11 PM »

Have started to notice ISP forums adapting the rule to turn off VDSL modem for 30 minutes and do your stuff before switching it back on again which is what I do but who first discovered this procedure as I only first came across this on the Kitz forum some 2-3 years ago and it was suggested by burakkucat
Logged

burakkucat

  • Global Moderator
  • Senior Kitizen
  • *
  • Posts: 18953
  • Over the Rainbow
    • The ELRepo Project
Re: ISP's now using the 30 minute rule
« Reply #1 on: November 03, 2016, 09:00:23 PM »

I think it was a joint decision.  :-\

Kitz had researched the DLM process and showed the usage of the 15 minute time quantum for the circuit statistics. Not knowing when a 15 minute period begins or ends, the simplest solution was to double the time period to 30 minutes, thus ensuring that there is at least one full 15 minute period (and a power-fail "dying gasp") noted by the DLM process for the circuit in question.
Logged
:cat:  100% Linux and, previously, Unix. Co-founder of the ELRepo Project.

Please consider making a donation to support the running of this site.

NewtronStar

  • Kitizen
  • ****
  • Posts: 4395
Re: ISP's now using the 30 minute rule
« Reply #2 on: November 03, 2016, 09:19:29 PM »

Well done both of you those ISP help forums are now taking this on board while giving out broadband support advice you should be very proud that the Kitz site is helping those ISP's and their customers  :)
Logged

kitz

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 29867
  • Trinity: Most guys do.
    • http://www.kitz.co.uk
Re: ISP's now using the 30 minute rule
« Reply #3 on: November 03, 2016, 10:54:08 PM »

As b*cat mentioned, at the time I wasn't certain from the documentation when the 15 min period began. 
It is highly likely to co-incide with these figures reported by your modem

Code: [Select]
Latest 15 minutes time = 12 min 48 sec
FEC:            0               0
CRC:            2               0
ES:             1               0
SES:            0               0
UAS:            0               0
LOS:            0               0
LOF:            0               0
LOM:            0               0
Previous 15 minutes time = 15 min 0 sec
FEC:            0               0
CRC:            1               0
ES:             1               0
SES:            0               0
UAS:            0               0
LOS:            0               0
LOF:            0               0
LOM:            0               0

I think it may have been someone else (7LM?) /joint decision that 30 mins was to err on the side of caution so I cant claim full credit for that. 
iirc 7LM also found other documentation about BTs DLM but I cant recall now what that was, but in his credit he discovered a few things too which we were previously unaware of.   

Dying gasp is not used by DLM... but it is used for diagnostic purposes.   
Your ISP/BTw is able to see if your modem sends a dying gasp message.  The example used in the documentation was so that they could check if the EU has properly power cycled the modem if requested to do so by them.. and shows up in one of GEA tests available to the SP. 

Those were the days were if you had some key words you may fall lucky with a search and stumble across documentation.  Unfortunately everything since ASSIA is now locked down tight although the ISPs should be able to have access to this information.  Trouble is there is/was so much stuff there that it takes a lot of sifting though and piecing together various bits of info.  The info I got was double checked with one ISP rep before publication who kindly confirmed a few things as he too had been attempting to pull things together.  There was no big confidentiality thing at that time, just time consuming finding the bits we wanted to know and putting it all together.   

Logged
Please do not PM me with queries for broadband help as I may not be able to respond.
-----
How to get your router line stats :: ADSL Exchange Checker

sevenlayermuddle

  • Helpful
  • Kitizen
  • *
  • Posts: 3140
Re: ISP's now using the 30 minute rule
« Reply #4 on: November 04, 2016, 12:08:38 AM »

I think it may have been someone else (7LM?) /joint decision that 30 mins was to err on the side of caution so I cant claim full credit for that. 
iirc 7LM also found other documentation about BTs DLM but I cant recall now what that was, but in his credit he discovered a few things too which we were previously unaware of.   

I'm flattered that you remember that, my own investigations into DLM were around 8 years ago and these days I have trouble remembering 8 days ago.   :D

So far as I recall, what I found was some BT patents that described an implementation of a  DLM.  We might reasonably assume that they described BT's own DLM, but that is just an assumption.   ::)

These patents suggested that there might be different 'Penalties' for different degrees of instability.   Crossing the threshold of error rates might get your target margin reduced by 3dB, but extreme instability, defined in these patents as 10 retrains in one hour, got you an immediate 6dB reduction. 

The other interesting thing (to me) about these patents was there was an element of hysteresis.  Once you had been penalised for instability, in order to remove that penalty, you had to demonstrate significantly greater stability than had existed before the penalty.  Just reducing the error rate to previous levels wasn't enough, they had to be far before previous levels.

But that was all for the old 20cn DLM, I know very little at all about current DLM and above is probably of little relevance or interest, so I shall hush myself. ;)
Logged

Weaver

  • Kitizen
  • ****
  • Posts: 4004
  • Retd sw dev; A&A; 3 ◊ 7km ADSL2; IPv6; Firebrick
Re: ISP's now using the 30 minute rule
« Reply #5 on: November 04, 2016, 12:33:43 AM »

Is there any chance that dying gasp is now used by 21CN DLM?

I have a vague recollection of having seen dying gasp mentioned in some BT documents relating to 21CN but my memory fails me here.

I do try to follow the half hour rule, but in fact I don't seem to ever get penalised for doing a switch-off followed by an almost immediate switch-on these days. Not very scientific. I always power modems down first and don't ever just pull the DSL cable out.

I donít know about dying gasp support in my DLink DSL-320B-Z1 modems.

Confusion: I have seen dying gasp mentioned in documents about the various other older DLink modems called DSL-320B-*, which are not at all the same thing. There was a thread about the different devices. They look completely different, and might very well have different software (memory fails) or hardware. Basically they really should not have (partially) reused the model designation.
Logged

sevenlayermuddle

  • Helpful
  • Kitizen
  • *
  • Posts: 3140
Re: ISP's now using the 30 minute rule
« Reply #6 on: November 04, 2016, 12:44:52 AM »

Pretty sure, in the days I investigated, ITU recommendations mandated that all consumer modems would send dying gasp.

But... ITU recommendations are just that, 'recomendations'.  National implementations might override them, and allow kit that doesn't send dying gasp.   And even if dying gasp is sent, there would be no compulsion on BT's DLM to take any notice of it.
Logged

j0hn

  • Reg Member
  • ***
  • Posts: 663
Re: ISP's now using the 30 minute rule
« Reply #7 on: November 04, 2016, 02:55:55 AM »

Is there any chance that dying gasp is now used by 21CN DLM?
The fact that DLM will intervene after too many modem reboots on VDSL2 would suggest not. If it took the dying gasp into account it should only act when a line retrains itself.
I do try to follow the half hour rule, but in fact I don't seem to ever get penalised for doing a switch-off followed by an almost immediate switch-on these days. Not very scientific. I always power modems down first and don't ever just pull the DSL cable out.
That's because you use BT Wholesale DLM most likely provisioned on their Standard profile and that should allow up to 5 retrains in a 24 hour period and still be categorised as good/green. It's >10 retrains before the line is categorised red. Those figures are halved for the Stable profile. I wouldn't advise checking if that info is still accurate though.

I usually follow the 30 minute rule, especially if I need to reboot the modem multiple times. If I'm only needing to resync once I sometimes don't bother waiting. I've never been punished for a single resync.

My ES number for the past 24 hours has been too close to my limit, I've had to drop my sync a little to retain fastpath.
« Last Edit: November 04, 2016, 03:00:32 AM by j0hn »
Logged
BT FTTC 55/10 ECI Huawei Cab - Zyxel VMG8924 bridge mode + Asus RT-AC68U - minted on MDWS via DslStats

kitz

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 29867
  • Trinity: Most guys do.
    • http://www.kitz.co.uk
Re: ISP's now using the 30 minute rule
« Reply #8 on: November 04, 2016, 01:23:15 PM »

>>  Is there any chance that dying gasp is now used by 21CN DLM?

No.  They definitely use MTBR & 15 mins to detect unforced retrains on all 3 DLM systems. 
Even the old 20CN RAMBO works on 15 min periods and has a 'login event collector'.


See Detection of sync events
Quote
Ü Note on Dying Gasp - Whilst DLM may not make use of the dying gasp message, nor is it mandatory for MCT; modem manufacturers are encouraged to implement it's use for Openreach's Test and Diagnostic systems.  This allows ISPs to check EUs have performed a power cycle of the modem prior to a potential engineer visit.  See SIN 498 Section 3.2.5 R.OAM.4.
Logged
Please do not PM me with queries for broadband help as I may not be able to respond.
-----
How to get your router line stats :: ADSL Exchange Checker

kitz

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 29867
  • Trinity: Most guys do.
    • http://www.kitz.co.uk
Re: ISP's now using the 30 minute rule
« Reply #9 on: November 04, 2016, 01:35:51 PM »

The fact that DLM will intervene after too many modem reboots on VDSL2 would suggest not. If it took the dying gasp into account it should only act when a line retrains itself.That's because you use BT Wholesale DLM most likely provisioned on their Standard profile and that should allow up to 5 retrains in a 24 hour period and still be categorised as good/green. It's >10 retrains before the line is categorised red. Those figures are halved for the Stable profile. I wouldn't advise checking if that info is still accurate though.

I usually follow the 30 minute rule, especially if I need to reboot the modem multiple times. If I'm only needing to resync once I sometimes don't bother waiting. I've never been punished for a single resync.

My ES number for the past 24 hours has been too close to my limit, I've had to drop my sync a little to retain fastpath.

Same here, I dont bother for the odd one or two, but I will if I'm messing with a new router etc.

Its worthwhile noting that the NGA system has different MBTR params than the BTw 20/21CN DLM systems.  - see here
The early NGA MBTR params were quite harsh, but they relaxed them in May 2015.

At one point the BTw DLM dabbled with using an average over 48hrs rather than 24hrs, but I don't know what happened with that.

Logged
Please do not PM me with queries for broadband help as I may not be able to respond.
-----
How to get your router line stats :: ADSL Exchange Checker

Chrysalis

  • Content Team
  • Kitizen
  • *
  • Posts: 4429
Re: ISP's now using the 30 minute rule
« Reply #10 on: November 04, 2016, 04:21:38 PM »

I know a certain person who's name begins with 'a' rubbished the 30min reboot rule, but I still stick by it, I have seen a few people report DLM intervention after doing a quick reboot, whilst people doing 30 min reboots dont get intervention.
Logged
Sky Fiber Pro - Billion 8800NL bridge & PFSense BOX running PFSense 2.4 - ECI Cab

kitz

  • Administrator
  • Senior Kitizen
  • *
  • Posts: 29867
  • Trinity: Most guys do.
    • http://www.kitz.co.uk
Re: ISP's now using the 30 minute rule
« Reply #11 on: November 04, 2016, 04:42:33 PM »

That was because he found a document which talked about reboot time of 'x' seconds (sorry cant recall exactly what 'x' was now without looking)..   
but what that document was referring to was the amount of time needed by the RAP to pick up your sync speed for your IPprofile.

« Last Edit: November 06, 2016, 03:47:30 AM by kitz »
Logged
Please do not PM me with queries for broadband help as I may not be able to respond.
-----
How to get your router line stats :: ADSL Exchange Checker

NewtronStar

  • Kitizen
  • ****
  • Posts: 4395
Re: ISP's now using the 30 minute rule
« Reply #12 on: November 07, 2016, 09:25:08 PM »

Well done sevenlayermuddle most users will not be recording stats from the modem and don't even know about errored seconds but a modem off rule for 30 minutes is much better than the  DLM taking action
Logged

PhilipD

  • Reg Member
  • ***
  • Posts: 320
Re: ISP's now using the 30 minute rule
« Reply #13 on: November 16, 2016, 04:25:09 PM »

Hi

I tend not to worry about the 30 minute rule and haven't noticed anything change. 

If I need to disconnect to mess around or change things I always issue via telnet "xdslctl connection --down", which nicely terminates the VDSL session and puts the modem offline, before turning off or unplugging the modem.

I'm not sure if this means the DLM accepts the disconnect as user initiated and so ignores it, but it does carry across and the ISP knows about it, as on Xilo they have a control panel option to see the session times, and when I issue the above command their portal shows "User Request" under terminate reason, but hard yanking out the telephone cable or some other random disconnect registers as "Port error".

Regards

Phil



Logged