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

Login with username, password and session length
Advanced search  

News:

Pages: [1] 2

Author Topic: question about Modem & DSLAM pairing  (Read 4869 times)

snadge

  • Kitizen
  • ****
  • Posts: 1111
question about Modem & DSLAM pairing
« on: April 19, 2013, 11:18:12 PM »

hi all

I thought I read somewhere that where Huawei or ECI DSLAMs are installed in cabs for FTTC that the customers connected are supposed to get the modem made by same manufacturer?

that is too say if your cab has an ECI DSLAM then you would get an ECI Modem...well, thats what I read anyway - if I recall it was because the two were designed to work with each other and less chance of having conflicting issues that may arise if using mis-matched hardware?

its come to my attention that an engineer on here (im presuming Black Sheep) has said that engineers just grab whatever they have available? - so does this mean the "matching of hardware" is not true?  wished I could remember where I read it now, or, does it simply mean that if they dont have a matching modem they can simply use the other one..but matching them is preferred?


cheers
« Last Edit: April 19, 2013, 11:28:56 PM by snadge »
Logged
Zyxell VMG8924-B10A <-> PlusNET 80/20 <-> Eci DSLAM
SYNC: 79,000k - 20,000k - INP:off - INTERLEAVING:off
Raspberry Pi 3B+ running DSL-stats

Bald_Eagle1

  • Helpful
  • Kitizen
  • *
  • Posts: 2720
Re: question about Modem & DSLAM pairing
« Reply #1 on: April 19, 2013, 11:34:31 PM »


its come to my attention that an engineer on here (im presuming Black Sheep) has said that engineers just grab whatever they have available? - so does this mean the "matching of hardware" is not true?  wished I could remember where I read it now.



You did read it in the Kitz forum & it was indeed the said engineer that reported what he had been told by Openreach managers regarding which modem can be used (i.e. any could be used as it made no difference).

I can't quite recall in which thread BS informed us. perhaps he will be able to confirm if Openreach's position remains unchanged.
He did also inform us that despite the note from Openreach he personally tries to match the modem to the DSLAM wherever possible.

Our own various tests & quite long term 24/7 monitoring of other connections does suggest there is a difference on SOME longer and lower speed connections, the ECI tending to work at a faster sync speed (interleaving OFF) than the Huawei HG612 when connected to an ECI cabinet DSLAM.

Logged

Black Sheep

  • Helpful
  • Kitizen
  • *
  • Posts: 4941
Re: question about Modem & DSLAM pairing
« Reply #2 on: April 20, 2013, 07:38:37 AM »

Hi guys.

Initially, it was a complete and utter no-no to mismatch modem and vendor equipment. Then, we engineers were informed that we could interchange said equipment, but only if you didn't have the correct modem stocked on your van and it would only be a short-term measure until we could return back to the EU with the correct modem.
Then, (This is BT), we were told the two modems were totally interchangeable and it didn't really matter which modem was installed, but if possible, use the correct modem-vendor.

Today's decision ?? Well, I visited my stores earlier this week and tried to get my usual quota of Huawei modems, only to be told that they are running a trial and only issuing ECI modems ?? I've been on long enough to not even bother questioning this decision, it will probably change again next week ??

I posted somewhere on another thread that, with the advent of VDSL 'Self-install', the ISP's are (or indeed have) developing their own built in modem/routers, so all this will probably become a thing of the past as the years roll by ??
Logged

ryant704

  • Reg Member
  • ***
  • Posts: 318
Re: question about Modem & DSLAM pairing
« Reply #3 on: April 20, 2013, 11:44:51 AM »

They're meant to give you a matching modem but if they don't have one in there van any will do as stated...

Though might be worth noting a bit...

When I have an ECI modem in place (I have ECI cab) I can sync up to 27Mbps then swap it for HG612 and it will hold the speed. Though the HG612 will only sync up to 25Mbps... so if you aren't that bothered about line stats I would just keep with the matching pair.

It's rumored it's better as the firmware talk to each other but that is only rumors but seems true in my case and experience.
Logged

snadge

  • Kitizen
  • ****
  • Posts: 1111
Re: question about Modem & DSLAM pairing
« Reply #4 on: April 21, 2013, 02:26:23 AM »

thanks for clarification guys :)

i thought I read right about them having to use matched hardware initially

you know this "self install" thing... well we all know that internal wiring setups affected by REIN can have a massive impact on VDSL with the broader range of frequencies...also bridged taps etc... will the self install come with an SSFP and/or information about how it would be best using an SSFP if you have a multi-socket internal installation?  the thing with the engineer install is he can ensure there are no dodgy internal wiring installs thats going to affect the connection?

cheers
« Last Edit: April 21, 2013, 02:33:30 AM by snadge »
Logged
Zyxell VMG8924-B10A <-> PlusNET 80/20 <-> Eci DSLAM
SYNC: 79,000k - 20,000k - INP:off - INTERLEAVING:off
Raspberry Pi 3B+ running DSL-stats

Black Sheep

  • Helpful
  • Kitizen
  • *
  • Posts: 4941
Re: question about Modem & DSLAM pairing
« Reply #5 on: April 21, 2013, 11:14:00 AM »

Nope ....... no SSFP. Just re-use of the existing dongle MF's.

You are of course quite right, about the engineering visit being able to maximise performance, as opposed to the average layman blindly stumbling through what could be a star-wired (Bridged tap) circuit. 'Managed Installs' as they are called, will still be available to the punter though.
Logged

waltergmw

  • Content Team
  • Kitizen
  • *
  • Posts: 2764
Re: question about Modem & DSLAM pairing
« Reply #6 on: April 21, 2013, 02:12:33 PM »

@ Bs,

Perhaps we should add subcontractor without a JDSU or EXFO to the layman group too ?

Kind regards,
Walter
Logged

snadge

  • Kitizen
  • ****
  • Posts: 1111
Re: question about Modem & DSLAM pairing
« Reply #7 on: April 21, 2013, 09:07:29 PM »

thanks again for futher clarification BS :) as always much appreciated
Logged
Zyxell VMG8924-B10A <-> PlusNET 80/20 <-> Eci DSLAM
SYNC: 79,000k - 20,000k - INP:off - INTERLEAVING:off
Raspberry Pi 3B+ running DSL-stats

Black Sheep

  • Helpful
  • Kitizen
  • *
  • Posts: 4941
Re: question about Modem & DSLAM pairing
« Reply #8 on: April 22, 2013, 09:23:28 AM »

Ha ha, Walter, you could have a point. ;)  ;D
Happy to help, Snadge. :)
Logged

Chrysalis

  • Content Team
  • Addicted Kitizen
  • *
  • Posts: 5538
Re: question about Modem & DSLAM pairing
« Reply #9 on: April 30, 2013, 06:07:40 PM »

The mismatch affects error rates in my case.

Irocially on my ECI dslam a HG sync shigher by 2mbit on fast path and about 6-8mbit higher on interleaving.  However the ECI has much lower error rates.  So using the ECI on a ECI dslam could be the difference between a fast path and interleaved profile.
Logged
Sky Fiber Pro - Billion 8800NL bridge & PFSense BOX running PFSense 2.4 - ECI Cab - LINE STATISTICS CLICK HERE

snadge

  • Kitizen
  • ****
  • Posts: 1111
Re: question about Modem &amp; DSLAM pairing
« Reply #10 on: April 30, 2013, 08:04:33 PM »

I've noticed on my adsl connection I get higher error rates when I use router that gets higher sync rate, those that are slower get less errors, yup identical SNRM, inp & interleaving, my sagemcom 2504n gets avg of 10 crc's per hour,  my Netgear DG834N gets avg of 2 crc's per hour


Sent from my Sony Xperia Miro on Tapatalk

Logged
Zyxell VMG8924-B10A <-> PlusNET 80/20 <-> Eci DSLAM
SYNC: 79,000k - 20,000k - INP:off - INTERLEAVING:off
Raspberry Pi 3B+ running DSL-stats

Chrysalis

  • Content Team
  • Addicted Kitizen
  • *
  • Posts: 5538
Re: question about Modem & DSLAM pairing
« Reply #11 on: May 01, 2013, 01:05:34 AM »

yes a lower sync speed will drop error rates, but the difference was huge plus I have had the HG sync as low as the fritz 3370 did. (same chipset as ECI dslam).

I have also had the hg in use with high noise margins, eg. my line started out with over 15db margin on the downstream and the error rate with that buffer was still much higher than I seen on a ECI chipset.

The difference in sync speed eg. on fast path on my line is about 2mbit. on my line 3db gives about 15mbit sync speed so the 2mbit difference is like the equivelent of about an extra 0.3-0.4db noise margin.  On the hg I avg now about 700 a day, on the matching chipset it was well below 50.  An extra 0.4db snr on the hg doesnt drop the error rate by that magnitude.
Logged
Sky Fiber Pro - Billion 8800NL bridge & PFSense BOX running PFSense 2.4 - ECI Cab - LINE STATISTICS CLICK HERE

snadge

  • Kitizen
  • ****
  • Posts: 1111
Re: question about Modem & DSLAM pairing
« Reply #12 on: May 01, 2013, 03:58:27 PM »

The difference in sync speed eg. on fast path on my line is about 2mbit. on my line 3db gives about 15mbit sync speed so the 2mbit difference is like the equivelent of about an extra 0.3-0.4db noise margin.  On the hg I avg now about 700 a day, on the matching chipset it was well below 50.  An extra 0.4db snr on the hg doesnt drop the error rate by that magnitude.

totally lost me there lol... :)

how is SNRM relating to Fastpath here?

700 CRC's per day is a lot, does it affect your browsing and downloads much?

I do know that changing SNRM by 0.4db will have 'just about' zero impact on error rates... eg. whatever you get on 6db your likely to get very similar (if not almost the same) on 6.4db or 5.6db - it also depends on what the noise margin is at before adjusting it by 0.4db, the closer to 0db it is then the more the 0.4db difference would make...

might help me understand if you posted the speeds on each modem.
Logged
Zyxell VMG8924-B10A <-> PlusNET 80/20 <-> Eci DSLAM
SYNC: 79,000k - 20,000k - INP:off - INTERLEAVING:off
Raspberry Pi 3B+ running DSL-stats

Chrysalis

  • Content Team
  • Addicted Kitizen
  • *
  • Posts: 5538
Re: question about Modem & DSLAM pairing
« Reply #13 on: May 01, 2013, 04:09:29 PM »

700 a day pretty much has no affect and in itself isnt huge when spread out over a 24 hour period.

When I got interleaved was when I had bursts during the night eg. one night I had hundreds of thousands of crc errors in a 2 hour period.

but obviously on a line with more errors over the threshold matching the modem may then take it below the threshold.

The comment regarding snrm is to indicate to you that on a fttc line utilising the entire frequency 2mbit isnt a lot of sync speed, its only a small amount of total capacity so as such wont have a high bearing on error rate.

The last 24 hours is actually lower.

Previous 1 day time = 24 hours 0 sec
FEC:            0               0
CRC:            488             0
ES:             240             154
SES:            0               0
UAS:            0               0
LOS:            0               0
LOF:            0               0

key here is the 0 SES so I have never had a cluster of errors close together in last 24 hours.

Last 15minutes.

Previous 15 minutes time = 15 min 0 sec
FEC:            0               0
CRC:            6               0
ES:             4               2
SES:            0               0
UAS:            0               0
LOS:            0               0
LOF:            0               0

so 4 errored seconds in a 15 minute period, pretty much irrelevant.

Of course it may seem high because some people have near perfect lines where they get extremely low error counts in the single digits per day.  There is huge variances on BTs local loops.  On adsl I used to on fast path get 10s of thousands of crc errors per day and even then the connection was useable, as long as I didnt have severe errored seconds.  I think I have less crc errors now than I had on interleaving on adsl.  Some people on FTTC have much high error rates than me and are stuck on interleaving.

But the point of my post is to show the difference I got from matching the chipset on the error rates, even if we use the new value of just under 500 a day from my past 24 hours its still with the other chipset dropping it to below 10% of error rate, and if you look at the sync speed drop by using the other chipset its a lesser price than the speed lost on FEC.
« Last Edit: May 01, 2013, 04:19:37 PM by Chrysalis »
Logged
Sky Fiber Pro - Billion 8800NL bridge & PFSense BOX running PFSense 2.4 - ECI Cab - LINE STATISTICS CLICK HERE

guest

  • Guest
Re: question about Modem & DSLAM pairing
« Reply #14 on: May 01, 2013, 04:36:13 PM »

Snadge is talking about Sky ADSL CRC error rates, which apparently get logged twice a day.

There's a threshold which he's on the wrong side of - on the right side DLM switches you to 3dB and near as dammit fastpath (21ms ping). I get CRC error rates of about 1/GB transfer (or per hour); snadge gets rates 30 times mine with not dissimilar attenuation.

So somewhere in between 25 and 700 CRC errors per day is the threshold where the Sky DLM system will not reduce noise margin to 3dB. I appreciate that's overly simplistic (snadge's local D-side run isn't good) but I think that's why he's asking. I rather suspect its got more to do with severe impulse noise events (snadge has them, I fixed mine so I don't) but its a mildly interesting empirical observation.
Logged
Pages: [1] 2
 

anything