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Line conditions and clarification

plexy
Grafter
Posts: 38
Registered: 28-08-2013

Line conditions and clarification

Hi Plusnet support,
After careful monitoring of my line, some work with external VDSL experts and you support team, theres a few things I would like to ask for clarification on.

First thing is the FTTC DLM profiles available from BTOR. Your support team have stated (as have team members in this very forum) that you have only standard, stable and superstable available to select for DLM on FTTC, that standard is what everyone is on and that this is the same as 'speed'. However, those options appear to correlate to BTW (standard ADSL/2+) profiles, not BTOR FTTC DLM profiles. Can you confirm that you have not made the same mistake as Zen internet and confused the two different ranges of DLM profiles available from the two different BTW and BTOR products? And can you confirm that I am indeed on the BTOR FTTC DLM profile of 'speed' not 'standard' or 'stable'
BTW = Standard, Stable, Super Stable
BTOR FTTC = Speed, Standard, Stable
(for reference, here is where Zen made this mistake http://forums.thinkbroadband.com/zen/t/4252187-re-ip-profile-reset-on-fttc.html)

Second thing, my line has significant reduction in upstream (and sometimes downstream) SNRM when the phone is off hook (down to 0dB sometimes). I have attached a graph of this. I raised this issue with your support team who replied
Quote
this isn't something that I would be concerned over as on Fibre your connection isn't really affected by the SNR like it is on a copper connection.

Please can you confirm that plusnet stands by this statement, that your FTTC products are not really affected by SNRM and that reductions in SNRM (down to 0dB) when the phone is off hook are acceptable?

Third thing, my line is getting either REIN or crosstalk. The graph of errors shows a distinct correlationt o early morning, lunchtimes and evening times. The tests for crosstalk/noise ran by your support team were all at 3am and 7am which is bound to show up nothing. I have confirmed this is not wiring or equipment in my house (all extensions disconnected, and all electricals bar the router and modem isolated, errors remain). Is it possible for plusnet to re-run the same line tests, but at peak times when the errors are actually in full swing - we are talking nearly 1 million per day? Please see attached FEC graph for example.

Fourth thing is my upstream has around 1000 CRC errors per day, 500 error seconds per day (some of which are SES). This is despite FEC being on, so these are errors even FEC cannot correct.. Even with a sync rate of 20mbps, my line never exceeds 16mbps upload throughput. Can you confirm these errors and throughput vs sync is acceptable to you on your products.

Thanks for your help.
2 REPLIES
SuperZoom
Grafter
Posts: 353
Registered: 17-05-2013

Re: Line conditions and clarification

These things do pose a significant looming issue for ISPs like PlusNet, as self-install after-market VDSL modem-routers become available, don't they?
As things stand, the BT idea seems to be that FTTC has to just be left to do its own thing entirely automatically behind the scenes and almost whatever interleaving/SNRM/sync speed limitation solution the DLM comes up with ought to be fast enough for customers to get done whatever they need to get done online - so they shouldn't worry about the details. Since you're not supposed to be able to see the stats, there probably is no real procedure in place for PlusNet to even begin to properly address your concerns.
But as stats do become visible to more people, they will begin to expect more ADSL-style engagement.
Standard/Stable terminology confusion probably won't help with that!
Would your noise issues not be worse on a "Speed" DLM profile, then, or does it not work like that?
plexy
Grafter
Posts: 38
Registered: 28-08-2013

Re: Line conditions and clarification

Quote from: SuperZoom
These things do pose a significant looming issue for ISPs like PlusNet, as self-install after-market VDSL modem-routers become available, don't they?

indeed they do.
Quote
Since you're not supposed to be able to see the stats, there probably is no real procedure in place for PlusNet to even begin to properly address your concerns.
But as stats do become visible to more people, they will begin to expect more ADSL-style engagement.

Unfortunately, BT are currently doing cabinet updates to band plans and at the same time pushing firmware updates to modems - which disable monitoring ability of unlocked modems, so this kind of thing may become harder. Probably not for those of us that have access to a plethora of VDSL2 modems due to our line of work, but for most home users who like to get 'in the engine room' this could pose a problem  Wink
Quote
Would your noise issues not be worse on a "Speed" DLM profile, then, or does it not work like that?

Any noise would not be worse, but the errors will affect the connection more if interleaving is lowered. Its up to DLM how much interleaving it applies based on line conditions, that is a BTOR decision to prioritise stability and speed over latency - by first applying FEC and if that doesn't cut the mustard, going for interleaving. I'm already quite high at 1053 interleaving and 16ms latency added. For me its more about the ping than the throughput so seeing if there was truly a spped profile option was something I wanted to at least try - it may be the case that I simply get too many retransmissions that I end up with excessive packet loss (or even modem resyncs), in which case it would be back to the standard profile - assuming PN are indeed confusing BTW and BTOR DLM profiles. If they are not then this whole point is moot.
Its really been a disappointing experience moving from a cabled area to a non cabled area. I selected a house within a specific distance to a FTTC cabinet to try to get the best possible connection and even then it seems like there are problems. The service level on faults, support and understanding/diagnosing connectivity problems seems to be a whole different ballgame on FTTC - it seems to be a case of 'if it sort of works at a reduced level of service, then there's no problem'. The whole experience moving to FTTC and trying to get acknowledgement of issues makes the virgin media technical support look positively upper class.