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Migrated from Be/Sky to PlusNet - Lower than expected Sync

mdc
Grafter
Posts: 44
Registered: 15-02-2015

Migrated from Be/Sky to PlusNet - Lower than expected Sync

Howdy folks, I'm a recent migrée from Sky; having previously been a BeThere customer. After a year of hell on Sky's DSLAMs, I finally bit the bullet and switched over to a BTW-provided product with PlusNet.
I'm on a reasonably good line; no resistance bias, a high AC balance (~80),  and about 1.5km long. It's a direct-DP line, so no fibre for me unfortunately. During the heydays of Be, I was able to sync at a relatively stable 3dB (disconnections maybe once a day due to REIN spikes / crossing the CRC error threshold), at a lovely 21mbps. On Sky, I was lucky to sync at 18mbps for 15 minutes, after which it'd drop rapidly down to about 9mbps. OpenReach did a massive amount of work on the line; all in all, two full replacements, boosting my line quality up to what it is today; as far as they were concerned, the line was absolutely perfect.
So anyway, with Sky's misconfigured DSLAMs out of the picture, things should be rosy over here on PlusNet... and they are, on the stability front. No disconnections since switchover 33 hours ago, but I'm stuck at a somewhat mediocre 15641kbps with an IP profile of 13.8mbps. SNR is currently floating around 7.0dB, although its varied between 6.1 and 7 to date. BitSwaps are within tolerances, CRC errors are a little on the high side (~7000, although I'm not sure of the accuracy of that - could be much, much lower as I had problems with authentication at first which caused a few spikes - on average I'm getting ~40 per 15 minute interval) but hasn't tripped DLM yet by the looks of it.
Anyway, the point is, at a similar SNR on Be/Sky, I was getting a MUCH higher sync rate - somewhere in the region of 18mbps. A 3dB/fast profile put me closer to 21mbps. Is it typical for Sync rate to be artificially capped during the DLM training period? Or am I just missing something fundamental here?
Cheers,
Michael
59 REPLIES
Kremmen
Rising Star
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Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

I'm assuming that your previous ISP was one of the LLU boys. In my experience, under ADSL, BT's 21CN is often slower and we see many reports here that echo exactly what you are saying about migrating from LLU. In my case it was about 15% as I reduced from 6.5mbps to 5.5mbps.
Now I'm on fibre the engineer told me I should be able to get 20mbps when he did his initial field tests but I'm only getting 17 on a good day. I do think they reduce speed to minimise errors.
I'm happy with 17, does all I need of it and that coupled with PN support will do me fine.
Let's be careful out there !
Community Veteran
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Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

Hi there, I moved from Be to PlusNet, bailing out just before my contract would have transferred to Sky.
My speeds are similar to yours, similar line length, and yes now I'm on BT kit it's a somewhat slower sync both downstream and upstream.
After the initial period my line did reach a 3dB margin, same as I had on Be, but of course that's only downstream. Still 6dB upstream which is a bizarre BT limitation.  Crazy
It's difficult to exactly compare as with Be I used a non-standard level of interleaving to balance stability with speed, but I'd say I'm about 5% slower.
That said, apart from recent apparently DNS-related web performance issues, I'd say that speed of normal activities is generally better with PN.
In particular I notice that my email programs, syncing across 18 accounts, are much faster than they used to be.
mdc
Grafter
Posts: 44
Registered: 15-02-2015

Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

Well, it's been a couple of days and I'm still at 15641kbps; SNR currently sitting at 5.6dB.
Going to try swapping my MK3 VDSL faceplate with an older MK1 (without the RF3 inductor) to lower attenuation slightly, and will swap over to a DGN2200 (slightly newer chipset than the DG834v4) to see if that increases things at all.
I have a feeling a 3dB Target SNR might be in order soon though Tongue
mdc
Grafter
Posts: 44
Registered: 15-02-2015

Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

Well, the router swap made things worse.
I had a theory, and a quick call to support confirmed it; my exchange's MSANs are Huawei ones, which I gather are IFTN chipset rather than BDCM; can anyone here confirm this?
adslctl info --vendor returns blank fields for all three IDs.
If it IS in fact an Infineon chipset on the E-side, a new router purchase might be in order Smiley Any recommendations?
On another note, I'm now on a 3dB profile (with Interleaving enabled for some reason) and I'm currently at 17290 down, but only 888 up. Good stats, but still room for improvement I reckon Smiley
Community Veteran
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Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

Have you checked any internal wiring isn't causing an issue? Quite frankly (although you haven't posted full stats) I would have thought as you line is not that long, then the chipsets in use are going to make very little difference. Whatever issue has caused the Upstream to be capped at 888 (IIRC Interleaving depth is related to this) needs to be resolved. Changing to a Mk1 plate is not likely to improve things, you should be far better with the Mk3 and it's common-mode filter especially if you have any imbalance on the line.
mdc
Grafter
Posts: 44
Registered: 15-02-2015

Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

There's no internal wiring aside from the run from the DP downstairs to my flat; my setup consists of - in its entirety - my router directly into the master socket (via the VDSL faceplate). No phone, no extensions etc.  AC Balance on the line is > 75, no resistance bias, 250/250 each side, although I have a nasty feeling that an RF3 was added unnecessarily somewhere along the way at a previous OR visit. The MK3 faceplate adds a second RF3 inductor between the RJ45 port and the test socket; the MK1 plate is straight-through.
Upstream target SNR has been raised to 12dB from 6, which would account for the drop in upstream sync, interleaving depth up is only 8, downstream is 128 which is a bit overkill. If I had to specify a profile myself I'd say that based on the error rate I'm getting currently, a safe bet would be 3dB/6dB with interleaving at 32/16. Not sure if BTW offer that level of granularity at the moment though.
Still a bit unsure of the DSLAM chipset situation; I've got the "0.0dBm" transmit power bug, and the card isn't reporting its vendor ID correctly. I've yet to test with a TG585v7 to see if it shows on that, but I'm trying to avoid any additional resyncs today so as not to irritate DLM too much Tongue
As for a new modem, it looks like a Draytek Vigor 120 operating as a bridge, with the DGN2200 handling routing duties could be a viable combo.
dick:quote
Superuser
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Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

Mdc,
I note that no one has welcomed you to the forums - welcome!  Cheesy
You seem to have a venerable insight into how all this ADSL black magic works.  I do hope that you will stick around here and share it with others encountering issues.  I found your observations on Sky's abilities elsewhere most interesting.  Wink
Cheers,
Kevin
mdc
Grafter
Posts: 44
Registered: 15-02-2015

Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

Kevin,
Thanks Smiley I'm not going anywhere for the next 12 months at least, so I'm happy to help out where I can Smiley
- Michael
Community Veteran
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Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

I had meant to say welcome as well, but it got overlooked as I was "multi-tasking" at the time Embarrassed
Quote from: mdc
There's no internal wiring aside from the run from the DP downstairs to my flat; my setup consists of - in its entirety - my router directly into the master socket (via the VDSL faceplate). No phone, no extensions etc.  AC Balance on the line is > 75, no resistance bias, 250/250 each side,
although I have a nasty feeling that an RF3 was added unnecessarily somewhere along the way at a previous OR visit.

Thanks for that info, that all sounds quite good although I'm not sure why you feel an RF3 has been added unnecessarily, at some point presumably Openreach or Sky's own tech decided there was some interference that an RF3 may help with.
What's the standard of wiring/cable between the building DP and your NTE5? Is there possibly some other  "master socket" at the building DP?
Quote from: mdc
The MK3 faceplate adds a second RF3 inductor between the RJ45 port and the test socket; the MK1 plate is straight-through.

I'm well aware of that, I would have thought the phrasing of my comment made that obvious. But the introduction of a 2nd one might unnecessarily attenuate some of the higher tones, some daytime experimenting whilst looking at Bits/Tone plots would be a good idea.
Quote from: mdc
Upstream target SNR has been raised to 12dB from 6, which would account for the drop in upstream sync, interleaving depth up is only 8, downstream is 128 which is a bit overkill.

If the US Target SNRM is 12dB, that may be coincidental, but 888 is definitely a banded upstream speed by DLM due to the issues it's detected.
Quote from: mdc
If I had to specify a profile myself I'd say that based on the error rate I'm getting currently, a safe bet would be 3dB/6dB with interleaving at 32/16. Not sure if BTW offer that level of granularity at the moment though.

You could have a specific profile set, even have Interleaving turned off, but that would likely be at the expense of increased errors, and from what I've just quickly read elsewhere you have an ample number already!
Quote from: mdc
Still a bit unsure of the DSLAM chipset situation; I've got the "0.0dBm" transmit power bug, and the card isn't reporting its vendor ID correctly. I've yet to test with a TG585v7 to see if it shows on that, but I'm trying to avoid any additional resyncs today so as not to irritate DLM too much Tongue

I would normally say no more than 5 in an hour, staying off for at least 10 minutes each time, and then leave it for the day. And not just resyncing/rebooting either - doing a graceful disconnect each time - drop your PPP session first, wait about 30 seconds and then power off the modem and wait a minute before unplugging from the line if needed. But with the level of errors you seem to have, I think I would be even more cautious.
Quote from: mdc
As for a new modem, it looks like a Draytek Vigor 120 operating as a bridge, with the DGN2200 handling routing duties could be a viable combo.

You are obviously quite knowledgeable about your kit, so I'm not going to make any suggestions other than use a modem that will work with the full version of RouterStats unless you can Telnet the interface to get relevant data and process it into graphical form in other ways (Bits/Tone, SNRM, errors perhaps) and generally that would mean a broadcom chipset.
mdc
Grafter
Posts: 44
Registered: 15-02-2015

Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

Thanks Anotherone Smiley
The CRC errors I mentioned in another thread were specifically with an Interleaving depth of 1, rather than what I'm on currently. Until today (more on that in a second), I was getting a fraction of that, more like 200/day rather than 4000.
HOWEVER.
Enter the demon about an hour ago; no warning whatsoever, SNR starts to plummet down to 1.0dB, errors start piling up, before a complete desync. And then, 13 forced resyncs in the space of 20 minutes (verified by phone support). In addition to this, when it DID finally come back up (currently sitting at 11mbit with more gaps in my graph than a dentist-shy Haribo addict's mouth. This could be one for the REIN engineers, but since it's been stable until midday today, my suspicion is that it was a random event and not something continually present.
With that said, it's been escalated to Faults just to make sure there wasn't an outside environmental factor that OR are aware of that could have caused it, perhaps work on the exchange or something which affected other customers as well.
Router-wise, it doesn't look like the Draytek's going to be an option unless I pick up yet another router, as the DGN2200 doesn't offer PPPoE over LAN, just via ADSL WAN. The next-best contender looks to be the DGN3500, which uses the same chipset as the Draytek but in a full, Netgear-wrapped package with GbE, which is a nice bonus - something I've been after for a while.
Also managed to confirm (using a TG585v7) that the DSLAM chipset is indeed IFTN, for anyone else who was wondering Smiley PlusNet aren't able to see the chipset themselves, but they were able to confirm that the MSAN manufacturer is Huawei. Apparently ALL currently-used BTW MSANs use Infineon chipsets, with the exception of the older Marconi kit which use Texas Instruments. Most of these have now been phased out in favour of the Fujitsu/Huawei kit, both of which use Infineon, as part of the 21CN rollout.
As for the RF3 which was added previously, it was basically done just to prove to Sky that EVERYTHING possible had been done on the line by OR, in an attempt to get them to admit that the problem was at their end. There was no sign of any interference on any of the tests which were performed over the course of a year, it was literally just a "belts and braces" move on OR's part. It was suggested at the time that having one couldn't do any harm, and considering the service I was getting that was indeed true at the time.
mdc
Grafter
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Registered: 15-02-2015

Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

This is pretty indicative of what's going on right now (just happened again).
Community Veteran
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Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

Ah, ouch, an error pattern I have seen before the cause of which was never established IIRC, and oh DMT Wink  Which modem are you using?
I was about to post this -
Well 200 CRC errors is a bit more reasonable, but it will of course depend on what you want from your connection (gamer?).
Your recent SNR plummet and resyncs do sound like a one-off event, maybe someone from OR poking about in your building DP or Cab etc, but it suggests a not so solid connection wherever it was, which might be related to your current issues.
As for Faults finding out if OR were doing something or BTw doing some exchange work, I would be surprised frankly if they actually asked the questions, it depends a bit on who deals with it, but I wouldn't bank on answers either even if the questions are asked!
Whilst an RF3 shouldn't do any "harm", it may be doing some good, as there definitely seems to be something going on with your connection and considering you are in a block of flats, there could be all sorts of Interference at various times, hopefully not. But that was also a reason I asked about the cable standard between your building DP and you.
As for modems and routers whatever choice you think you might go for, I would google this forum about each. There is quite a lot of experience with a multitude of devices and various experiences, but my over-riding criteria would always be compatibility with the full version of RouterStats and also capable of being pingable if needed, so you can set up a TBB BQM if needed. With separate devices you shouldn't have an issue with being able to drop the PPP session separate from sync.
As you have RouterStats set up and running, and DMT as well,  you can really see what's going on. Set RS to sample every 10 seconds and 720 points per page. One thing to note a lot of modem/routers don't like 2 logins with the same user, so if you can create additional admin usernames for yours, use one for RouterStats and one for DMT although I'd avoid running the 2 side by side for lengthy periods.
On the Bits/Tone plot there will be 7 tone gaps that are standard with this combination (110, 127, 188, 191, 243, 291, 34Cool which can be ignored. However the rest of it is horrendous showing some not insignificant problems are present. It's looking to me like it could be something with a failing or very poor quality SMPS.
JayG
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Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

Quote from: Anotherone
Ah, ouch, an error pattern I have seen before the cause of which was never established IIRC, and oh DMT Wink  Which modem are you using?

You do 'RC', and on more than one occasion - literally millions of CRC errors in the space of a few hours, with the DLM throwing everything in its arsinal at the problem! The cause was indeed never established.
(I do know how to spell the word in italics correctly but the forum word censor thinks it's a bad word!  Cheesy)
mdc
Grafter
Posts: 44
Registered: 15-02-2015

Re: Migrated from Be/Sky to PlusNet - Lower than expected Sync

Quote from: Anotherone
Ah, ouch, an error pattern I have seen before the cause of which was never established IIRC, and oh DMT Wink  Which modem are you using?

DG834v4 currently, seems to be the best-performing out of the three I have to hand currently (TG585v7, DG834v4 and DGN2200), all of which are supported by both RouterStats and DMT (different versions of the latter, of course).
Quote from: Anotherone
I was about to post this -
Well 200 CRC errors is a bit more reasonable, but it will of course depend on what you want from your connection (gamer?).
Your recent SNR plummet and resyncs do sound like a one-off event, maybe someone from OR poking about in your building DP or Cab etc, but it suggests a not so solid connection wherever it was, which might be related to your current issues.
As for Faults finding out if OR were doing something or BTw doing some exchange work, I would be surprised frankly if they actually asked the questions, it depends a bit on who deals with it, but I wouldn't bank on answers either even if the questions are asked!

I do a variety of things with the line, but speed is my primary concern, within reason. Having daily connection drops isn't a problem for me, as usually I don't do anything where it's the end of the world if I'm cut-off midway though; most of the important stuff is remote administration, which I can just pick up again after resync. The main issue with Sky was that every resync would cause massive chunks of bins to be unusable until a complete power down, 5 minute wait, and then powering back on. I seem to be stuck with these unusable tones now, even after triggering a resync later. I had a few more of those CRC spikes throughout the afternoon but they seem to have stopped now. It'll be interesting to see if they flare up again tomorrow or if it's a one-off event.
Quote from: Anotherone
Whilst an RF3 shouldn't do any "harm", it may be doing some good, as there definitely seems to be something going on with your connection and considering you are in a block of flats, there could be all sorts of Interference at various times, hopefully not. But that was also a reason I asked about the cable standard between your building DP and you.

From what I was told, and what I've seen through poking around in the electrical cupboard downstairs, it's all pretty decently installed. Twisted pairs up to the connection blocks in the cupboard, and then again to the flats. I'm unsure of what point they actually installed the RF3 at, as it's not in the flat itself so will either be in the cupboard downstairs or in the DP which I don't have access to.
Quote from: Anotherone
As for modems and routers whatever choice you think you might go for, I would google this forum about each. There is quite a lot of experience with a multitude of devices and various experiences, but my over-riding criteria would always be compatibility with the full version of RouterStats and also capable of being pingable if needed, so you can set up a TBB BQM if needed. With separate devices you shouldn't have an issue with being able to drop the PPP session separate from sync.

From what I've read the DGN3500 works with RouterStats, although has limited Telnet feedback which is a bit of a pain.
Quote from: Anotherone
As you have RouterStats set up and running, and DMT as well,  you can really see what's going on. Set RS to sample every 10 seconds and 720 points per page. One thing to note a lot of modem/routers don't like 2 logins with the same user, so if you can create additional admin usernames for yours, use one for RouterStats and one for DMT although I'd avoid running the 2 side by side for lengthy periods.

Thanks for the pointers with RS, I've always just used DMT in the past; these days I leave RS running and just launch DMT if there's a specific issue I need to check, as I prefer the way it presents its tone graphs.
Quote from: Anotherone
On the Bits/Tone plot there will be 7 tone gaps that are standard with this combination (110, 127, 188, 191, 243, 291, 34Cool which can be ignored. However the rest of it is horrendous showing some not insignificant problems are present. It's looking to me like it could be something with a failing or very poor quality SMPS.

Ah, I did wonder about those gaps; they weren't present on Be/Sky, I guess it's just a BTW thing. The bitloading not recovering after a resync has me worried to be honest, it's very reminiscent of the problems I had with DPBO on Sky :-/