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Guru
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Message 11 of 18

Re: PPP drop vs resync and Infity 10 day Stabilisation Period

@sjtp

 

Typically ... A Multi-service access Node (MSAN) would normally be found in an exchange, as with 21CN the MSAN is capable of delivering various levels of DSL , as with dsl2 and dsl2+, or even Max.

 

Dslam is a term used to describe a service mux or multiplexer, that can distribute a core service to a number of end users. (digital subscriber line access multiplexer)

So in real terms Infinity uses street dslams, but there is a grey area by definition as a typical outdoor MSAN cabinet consists of narrowBand (POTS), broadBand (xDSL) services, batteries with rectifiers, optical transmission unit and copper distribution frame.

 

Both terms in effect are accurate within reason.

 

DLM does everything with regard to setting and monitoring line control using information from previous line profiles, the base algorithms for line negotiation and profile setting, and can be as attentive as needed, depending on the state of the connection. It basically runs a daily algorithm to check out the connection, pulsed at 24 hour intervals, and a continuous algorithm monitoring SNR and margins up and down the paths. DLM runs directly from mux control, and can be either exchange or roadside located depending on equipment specification and manufacturer. It's not only limited to UK use .... it's used similarly in other countries as well. Whereas Max sets its IP line profile from the RAS, 21CN connections and Infinity line profiles are set direct from MSAN/Mux control.

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Distinguished Expert
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Message 12 of 18

Re: PPP drop vs resync and Infity 10 day Stabilisation Period

vdsl2 doesnt use msan it uses dslam
this is a fibre forum not adsl
please try to stop the confusion
there are plenty of adsl forums for you to post in
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Guru
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Message 13 of 18

Re: PPP drop vs resync and Infity 10 day Stabilisation Period

This is a set of questions rather than a statement ....

 

1 - My reading of all that is that Just like ADSL2, if the hub is reset too often DLM senses "lineflap" mode, and puts the connection into a banded profile  was incorrect for VDSL?  

 

2 - True if the modem is reset too often, as we have all said many times.  But the hub cannot effect the modem/cabinet/DLM thing at all; it can only cause the sync speed resulting from modem/cabinet/DLM operation to be sensibly recorded in the BRAS/IP profile?

 

3- And banding applies only to DLM, and Openreach are the only people who will affect the banding?  

 

4 - Neither Openreach, the ISP, nor BTW will never explicitly band anyone?

 

5 - DLM may automatically band them because of line conditions?

 

6 - Openreach can remove the banding and free the DLM profile; but can't stop DLM putting it back again?

 

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Distinguished Expert
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Message 14 of 18

Re: PPP drop vs resync and Infity 10 day Stabilisation Period

the main purpose of a banded profile is to stop the modem syncing at a very low rate
dlm sets the maximum rate and the minimum rate to be half of the maximum rate
dlm checks the errors and retrains in the last 24 hours and adjusts the profile to increase interleave and inp
this can result in a resync to implement the changes
the ip profile may be reset if an engineer makes changes to the line but it is usually left alone
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GSB1
Contributor
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Message 15 of 18

Re: PPP drop vs resync and Infity 10 day Stabilisation Period


@Bullitt wrote:
the main purpose of a banded profile is to stop the modem syncing at a very low rate
dlm sets the maximum rate and the minimum rate to be half of the maximum rate
dlm checks the errors and retrains in the last 24 hours and adjusts the profile to increase interleave and inp
this can result in a resync to implement the changes
the ip profile may be reset if an engineer makes changes to the line but it is usually left alone

So a banded profile will become un-banded in time (if all is well)?

 

If the above describes a banded profile, in simple terms what describes a non-banded profile? A line that syncs at the best it can for the line and line conditions?

 

Keeping the technicalities not too heavy, can someone give me a summary of the purpose of the stabilisation period, why this is required if the line is dynamic and is there anything determined during the atabilisation period that will never change dynamically afterwards?

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Guru
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Message 16 of 18

Re: PPP drop vs resync and Infity 10 day Stabilisation Period

the main purpose of a banded profile is to stop the modem syncing at a very low rate  Why would the modem sync at a very low rate?  If the line is so terrible at sync time that only a low rate is possible, what will happen?

 

If the above describes a banded profile, in simple terms what describes a non-banded profile? A line that syncs at the best it can for the line and line conditions?  I think that is pretty much correct.  

 

can someone give me a summary of the purpose of the stabilisation period, why this is required if the line is dynamic

My understanding is  ... (awaiting correction)

 

When the line is installed, it goes into an 'unbanded' state, so typically gets a reasonably high sync, depending only on line conditions at sync time.  If it happens to sync at a good time, when a little extra noise occurs sync will probably be lost, so it will resync at a lower rate.  Over the first couple of days (not the 10 days often mentioned which was for ADSL) DLM monitors what is going on, but does not actually interfere.  Based on what DLM sees over that period it decides the most appropriate sync rate and interleaving (DLM profile), and forces a resync appropriately.

 

DLM then monitors the line continuously as mentioned in the other posts.  It may change the DLM profile as a result; it will enforce any new profile on a 24 hour schedule.  It will also use the profile if the modem has to resync for any other reason (burst of noise causes lost sync, power cut, user intervention, ...).

 

If Openreach 'resets the profile', that effectively goes back to the 'unbanded' state.

 

is there anything determined during the atabilisation period that will never change dynamically afterwards?  No.

 

~~~

I don't quite understand the banding, but approximately ...  Speeds are divided into bands of speeds.  When DLM is allowing your profile to rise, it will not immediately increase your sync to the max it things appropriate, but will play safe by moving it into the next higher band.  If it is ok there for a day or two, it will move it up one more band.  This will continue until DLM reckons it has got the right level.  That level will be within a band; you will effectively be banded but it won't matter as the band is the 'correct' band for your line.

 

For example, after I had a spot of bother, my sync went down to a very low value I didn't record.  After a couple of weeks it went up to 43999, then two days later to 59999, then tow more days to 73999.  It stayed there for some time, then crept to 74156, where it has stayed (give or take very small changes) for a couple of months.

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Highlighted
Distinguished Expert
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Message 17 of 18

Re: PPP drop vs resync and Infity 10 day Stabilisation Period


@sjtp wrote:

the main purpose of a banded profile is to stop the modem syncing at a very low rate  Why would the modem sync at a very low rate?  If the line is so terrible at sync time that only a low rate is possible, what will happen?


if a burst of noise causes the connection to be lost and the noise is still their when it retrains then it could connect at a very low rate

if this happened then the line would remain at a very low rate until a retrain was forced by the user powering off the modem

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Guru
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Message 18 of 18

Re: PPP drop vs resync and Infity 10 day Stabilisation Period

 

@GSB1

 

Banded profiling normally only happens after profound noise issues, or many interventions. It's DLM's way of reducing linespeed quickly in an effort to stabilise it .... but at the same time afford a higher and lower limit on which to modulate the connection.

Banding is automatically lifted after DLM sees certain criteria met ... all to do with timescales/ error rates and amount of shift the line has seen since it linetrained. The more profound the shift, the longer it takes.

 

An example would be if say, contractors were doing an extension next door and disturbed lines or caused massive impulse noise with contractors plant, for a week .... then they moved away. It was a passive event that DLM picked up on, but has gone .... once the source of influence has gone DLM will allow the line to start and resurrect, using pulse checks to test SNR and margins on the paths. Another example would be local storms, allbeit DLM can and does recover quite quickly from thunderstorms, over a short period.

 

Typically if a downstream noise margin on any xdsl connection exceeds 15db, BT have set their DLM to use profile banding, either shallow or deep banding with incremental bands between (likeADSL2) depending on the level of shift away from the previous set MSR. Anything up to 15db margin will be managed by a daily DLM algorithm, running 24/7

 

The stabilisastion period has really only one goal ... to give you the fastest possible connection whilst at the same time finding the MSR. It does so by running an algorithm that uses various modes, and those modes will run differing levels of error correction and levels of SNR (different to SNRm). After a time it decides (logically) how to run the line for the conditions it is "seeing"... and then settles down to finetune the connection using daily DLM.

The most important part of this is that line history is recorded from the outset, and used later on for reference by DLM, and so the connection must be left unhindered to do its work.

 

Changes do happen afterwards, environmental changes, so DLM is flexible enough to allow changes in noise margin and error correction levels if outside influences implicate the connection. It's the only way of running an automatic DSL system that caters for lines of varying lengths and quality on a national basis.

 

All because of the metallic path.

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