Woah!
I'm with B*Cat here
A thoroughly confused b*cat
Me too, but I think this is a
very important discussion that we're starting here about the FTTC DLM.
OK A, so
That's the maximum downstream bit rate used in a handful of the ~200 banded* channel-profiles [1] that Openreach can bind to a VDSL2 subscriber port.
IIUI right, this means that there are ~200 variations on a capped IP profile (of one kind or another, i.e. the parameters involved are not just restricted to max line sync rate). Is there a list of them with the max sync rates anywhere? From BE's and my own experience (and I'm sure Chrysalis could add to this too) between us we have (it seems) observed in DS 80, 67, 54, 35, and 27 (I will ignore US for the moment).
Then there's Walter's helpful observation
I have observed two quite different situations almost as if the DLM has a blacklist of performance criteria,
A "Good" line will adjust around a set of different sync speeds presumably as line conditions vary with every power-reset.
A "bad" line, usually due to some execrable installation procedures remains capped
I'm sure both BE and I (and a lot of others no doubt) would like to know what those
performance criteria are that leaves us both unshakeably capped - and in BE's case it seems worse than that, in that it appears that he has a max capped value of 27 but still syncs >25% lower than that, which after 14 days, is by BTOR's definition a fault worthy of invesigation.
Without boring everyone with the details, my own experience is that my original profile was 80/20 with the attainables up around 92/33. Then one day some clod was messing about in the cabinet. Once at lunchtime when (s)he started on it, causing ~17 resyncs, and then at the end of the afternoon when (s)he finished, causing a further 9 resyncs. Totally anomalous. Didn't happen again.
Of course you (and I) would expect DLM to be upset by this, and it was. It capped it at 35. But as the 'fault' disappeared, it backed off to 54 3 days later, and to 67 a further 3 days later. But that's where it's stayed - over a month later, with absolutely negligible and totally recovered error rates on fastpath with no INP. Nothing it seems anymore will make it shift this cap. It's as if, as Walter says, a single anomalous day (wholely outwith my control), has caused it to consign me to the
bad boys list, even when attainables remain way above 80/20. The profile it seems to be using has 12dB DS and 15dB US SNRms. No wonder sync rates are suppressed.
Have you given the ECI a try?
No, but I do have one to hand. However do you seriously think that its potentially better performance will cause the DLM to remove the blacklisting? I'd be willing to try it, and if it worked (which I have to say I would doubt), then I would quite happily send mine to BE to let him try to, if he wants. Even now, if he wants - I can wait till later.
But if I have a reasoned complaint, it is this 'blacklisting' idea. I expect DLM to adjust down and hopefully back up again ain the light of transient conditions. That's what it's there for. The problem is that despite the line characteristics returning to normal (i.e. pre-incident) it does not seem to back off to where it was previously. If this hysteresis is displayed on every such occasion then we are all potentially consigned to a downward-spiral in our profiled rates.
Sorry BE if I've hijacked your problem, but I felt Asbo's and Walter's observations shouldn't be lost, as they are important to a lot of us, even though it doesn't of itself explain why you 25% below your profile.
[EDIT] Chrysalis observed earlier in the thread
What are you speaking of is probably line banding which the new DLM does instead of adjusting target noise margins (I assume so it cant be overriden by people tweaking the noise margin CPE side).
To some extent I believe that this is so, but not entirely, as BE has also had fastpath
removed. But is that a
temporary or a
permanent change e.g. have BTOR updated the profiles recently?
I don't know but it is suspicious.
Simply using banded profiles with max sync rates like that is a
very crude way of managing line conditions, but if they were doing that it might explain some things we are seeing e.g. reduced profile maxes while DLM still apparrently believes there is no need for either interleaving or INP.
The cynic in me wonders if BTOR are quietly banding everyone at the next nearest profile to the official BTOR 'Estimate'?
Author
Topic: My experience with the Huawei and ECI Modems (Read 32830 times)