Sync speed drop after FritzBox replaced Zyxel

Hi all. I recently took up Zen's offer of rental reductions as part of the now-expired Big Deal, err, deal. They kindly sent me a new Fritx box router to replace the Zyxel VMG810 I had before. At the same time, I converted from Fibre 2 to Fibre 1 because I was getting sync around 38Mb/s from my line, so it wasn't really worth the extra cost for Fibre 2.

On installing the router, it wouldn't settle - was getting continuous DSL drops for about 3hrs. Putting the Zyxel back immediately stabilised the line. After a day or so, I put the Fritz back in and it dropped a couple of times, then stabilised. However, it was synching at about 35Mb/s. Since then, about 12 days ago, the DSL line has dropped once or twice each day, each time re-synching at a slightly lower speed. It's now settled at 32.4Mb/s, quite a bit down on what's been achievable prior, acknowledging the change to Fibre 1.

At the same time, the downstream SNR has increased from about 7/8dB to 11/12dB. I'm seeing occasional periods where a number of unrecoverable errors are detected on the line - not large numbers, the maximum was about 200 in an hour. Mostly, it's zero.

I've tried changing the line settings on the Fritzbox to favour stability, but that had little apparent effect so all of them are set to favour performance. Line stats, below:

Receive Send
Max. DSLAM throughput kbit/s 32400 10000
Min. DSLAM throughput kbit/s 128 128
Attainable throughput kbit/s 42259 9378
Current throughput kbit/s 32398 9378
Seamless rate adaptation off off

Latency fast fast
Impulse Noise Protection (INP) 43 0
G.INP on off

Signal-to-noise ratio dB 11 5
Bitswap on on
Line attenuation dB 23 37

Profile 17a
G.Vector off off

Carrier record A43 A43


Seconds With Not Remediable Errors (CRC)
Errors (ES) Many
Errors (SES) per
Minute Last
15 Minutes
FRITZ!Box 41 13 0.13 7
Central exchange 487 2 0.76 21

Before I awitch back to Zyxel, possbly resetting something, is there anything else I should try to speed things up? Would Zen be able to do anything to restore the lost capacity?

TIA,
PP

Edited by Pablo_Pablovski (Thu 14-Sep-17 19:31:36)

More stats stuff.

Online Time Data Volume (MB) Connections
(hh:mm) Total Sent Received
Today 19:32 1817 119 1699 1
Yesterday 24:00 870 78 792 1
Current week 91:29 7011 538 6472 4
Current month 276:15 25773 1483 24290 98
Previous month 0:00 0 0 0 0

I have used Fritz!boxes (7390/7490) on my Zen FTTC line for over 5 years without any major issues. Indeed, my stats show a constant 74.7/20 connection since mid July with a very low error rate. My downstream SNR is 5 on an ECI cabinet. I do set up my Fritz.boxes manually using the advanced settings menu.

AVM Berlin are extremely good are analysing the inbuilt diagnostics and the boxes do come with a 5 year warranty.

Somewhere in the settings on mine is a "slider" between speed and stability. Make sure it's set all the way to "speed" (or similar).

I got the 'free' Fritzbox with my upgrade to Fibre 1.

I eventually gave up with it and bought myself another DrayTek (my old Draytek 2600 was too old for fibre)

Edited by Sandgrounder (Sun 17-Sep-17 21:55:44)

Thanks, I'd done that after lowering the settings toward "stability'. Didn't make any difference as far as I could tell.

The sync speed has continued to drop, it got to 27Mb/s after the line re-sync'd today. I phoned Zen support who were very helpful though the issue persists. I swapped the Zyxel back in and it snyc'd at the same speed as the fritz so it look like the BT line management is keeping speeds lower than optimum. I'm told not much can be done since the speed is within the estimated range available. The fritz box is back in and I've to call again on Friday to see how it's been. If problems persist, Zen send out a replacement router. Bit of a faff, and disappointing because the router reports a max attainable speed of 43mb/s,so it should be able to support akt more than 27mb/s.

Thanks, I have the Zyxel that was very stable at 38mb/s since I upgraded to fibre in Feb. Sadly it's now synching at the same reduced speed that the fritz box has reduced the line to so I'll defer any purchases until I know the BT line management tool is allowing the line to synch at the highest rate possible. Appreciate the recommendation though, I'll look into Draytek.

During the call to Zen today, we reset the settings to default on the fritz.box, plus I'm now connected to the test socket. No improvement so far, but I'll give it a few days before calling back.

Well I have a FRITZ!Box 3390 (Modem / Router) and a FRITZ!Box 4040 (Router) and my brother also has a FRITZ!Box 3390 which he is still currently using on his Zen Unlimited Fibre 2 package and he hasn't had any issues at all.

My 3390 went faulty not long after I got it, couldn't be bothered to send it back so I repaired it myself, turned out there was a broken track under the isolation transformer for the DSL connection, this then went on to work great while on ADSL2+.

Upgraded to FTTP late last year, so I brought the 4040 which worked great for about 10 days where it then started to get huge packet loss every 6 hours, wasn't too sure if it was the 4040 or my line, so I brought a Linksys WRT 3200 ACM which has the odd issue with IPv6 which you have to faff about with to get working, but the line is great going by my BQM in my sig.

Not too sure on what Fritz Model you are using, I assume its the 3490, not used that model myself, but it looks exactly like the 3390 but with USB 3.0/2.0 ports.

I say give the Fritz a go, you have a free Static IP, so I would setup a BQM if you haven't already and let that run and just compare them when you get issues, that's what I have been doing and mines been clean and flat.

Paul

These are my stats with a stable connection 74.7/20 from the 27th July. Downstream SNR 5. All performance sliders to the right.



FRITZ!Box 4084 0 0.05 1
Central exchange 632 102 0 0

I am using a 7490. The 3490 is effectively the 7490 without the PABX functions. My connection is rock solid on Zen GEA backhaul.

In reply to a post by lexden16:

I am using a 7490. The 3490 is effectively the 7490 without the PABX functions.

Its not just PBX that is the difference between the two, the 3490 has no phone features at all.

Paul

Update. After the router reset and connection to the test socket, DSL has gone down a couple times in 5 days. Line speed is now down to 25Mb/s, from a high of 37Mb/s. Apparently, I should be receiving a minimum of 32Mb/s, but 25Mb/s is not enough of a drop below that minimum for BT to accept a performance fault. Interestingly, SNR has continued to increase - it's now at 16dB, from a low of 7dB. The router reports a max attainable speed of 43Mb/s.

Zen support have been very supportive, and agree the problem arose from whatever the FritzBox router was doing on the line when it wouldn't stay synch'd when originally plugged in, but aren't currently able to offer a fix. Plan is to leave it for another week to see if BT Line Management enables an increase in the line capacity again.

Huh.. I'm tempted to put the Zyxel back in to see if that helps speed that BT LM recovery process - it was perfectly stable, no drops, for 6 months before the FritzBox went in. I'm told there's no way to reset LM to what it was before the FritzBox was installed.

Frustrating, but I'm hopeful!

Oh yeah, I was wondering if the line regrade from Fibre 2 to Fibre 1 could be the root cause. Does anyone know if that change involves moving my cable to a different DSLAM port or even a different DSLAM? Zen believed it requires an exchange visit by BT but didn't know exactly what was done.

If a hard change is made, that would be an area for investigation. I might ask for a re-regrade to Fibre 2 to see what happens, presuming Zen would honour the Big Deal pricing.

This is probably completely irrelevant as everyone's line is different, but it improved things for me and at least one other user.

My line (with lots of patching) syncs consistently at about 15% below what the Fritz shows as attainable, due I suspect to BT's DLM settings. But the Fritz 7490 has been otherwise consistent on VDSL2 for me, except for one unique period when I suffered line drops, high latency and packet loss and a drop in synch progressively which reached over one-third. It was completely cured by using the Fritz advanced interface option under line management to roll back to the previous DSL firmware. Thereafter, no more such problems. (Do a back up though so you can revert, as there is no option to revert back to current firmware again).

In an earlier post, you indicated that the problem with dropouts and poor speeds ceased, after you had unplugged the FritzBox - and reverted to your previous Zyxel VMG810 router.

In that case, why don't you try the Zyxel VMG810 again? Leave it plugged in for 7 to 10 days, to allow DLM to respond. What is If the point of using the FritzBox, if the Zylex performs better?

In reply to a post by Pablo_Pablovski:

Update. After the router reset and connection to the test socket, DSL has gone down a couple times in 5 days. Line speed is now down to 25Mb/s, from a high of 37Mb/s. Apparently, I should be receiving a minimum of 32Mb/s, but 25Mb/s is not enough of a drop below that minimum for BT to accept a performance fault. Interestingly, SNR has continued to increase - it's now at 16dB, from a low of 7dB. The router reports a max attainable speed of 43Mb/s.

Zen support have been very supportive, and agree the problem arose from whatever the FritzBox router was doing on the line when it wouldn't stay synch'd when originally plugged in, but aren't currently able to offer a fix. Plan is to leave it for another week to see if BT Line Management enables an increase in the line capacity again.

Huh.. I'm tempted to put the Zyxel back in to see if that helps speed that BT LM recovery process - it was perfectly stable, no drops, for 6 months before the FritzBox went in. I'm told there's no way to reset LM to what it was before the FritzBox was installed.

Frustrating, but I'm hopeful!

There's only two certain ways to get a reset done.

1) A speed regrade will trigger a DLM reset, at least it has done in my case. Unfortunately this will start a new 12 month contract if you're not currently in one.

2) A broadband engineer or an engineer from Openreach who can perform a DLM reset if they choose to do so.

3) Changing you from their LLU backhaul to WBMC or vice versa should also trigger a DLM reset, it did do when it happened to me a long time ago. But this probably can't be requested just for the purpose of resetting DLM.

There's also one other option but will require a modem that is capable of allowing you to adjust the SNRM target or capping the sync rate, for example the HG612 can cap the sync rate. A high enough SNRM will cause very few errors and ideally over time DLM will recover, though banded lines generally rarely recover or take forever to do so (just error correction most of the time).

Edited by Ixel (Fri 22-Sep-17 15:04:16)

Thanks. I'd noticed the option to use older DSL firmware but I didn't try it because it's not clear exactly what it does. I'll mention to Zen when I next speak to them. I note the advice to backup the config first - thanks.

In reply to a post by bob_lucas:

In an earlier post, you indicated that the problem with dropouts and poor speeds ceased, after you had unplugged the FritzBox - and reverted to your previous Zyxel VMG810 router.

In that case, why don't you try the Zyxel VMG810 again? Leave it plugged in for 7 to 10 days, to allow DLM to respond. What is If the point of using the FritzBox, if the Zylex performs better?

Yep, good point and I'd suggested that to Zen. They were keen to keep the FritzBox in place to see if it would stabilise and DLM would reconfigure the profile and return the last bandwidth. However, if the current line speed persists, I think I'll restore the Zyxel, and pester Zen to refund the regrade cost they charged when I moved from Fibre 2 to Fibre 1.

In reply to a post by Ixel:

In reply to a post by Pablo_Pablovski:

Update. After the router reset and connection to the test socket, DSL has gone down a couple times in 5 days. Line speed is now down to 25Mb/s, from a high of 37Mb/s. Apparently, I should be receiving a minimum of 32Mb/s, but 25Mb/s is not enough of a drop below that minimum for BT to accept a performance fault. Interestingly, SNR has continued to increase - it's now at 16dB, from a low of 7dB. The router reports a max attainable speed of 43Mb/s.

Zen support have been very supportive, and agree the problem arose from whatever the FritzBox router was doing on the line when it wouldn't stay synch'd when originally plugged in, but aren't currently able to offer a fix. Plan is to leave it for another week to see if BT Line Management enables an increase in the line capacity again.

Huh.. I'm tempted to put the Zyxel back in to see if that helps speed that BT LM recovery process - it was perfectly stable, no drops, for 6 months before the FritzBox went in. I'm told there's no way to reset LM to what it was before the FritzBox was installed.

Frustrating, but I'm hopeful!

There's only two certain ways to get a reset done.

1) A speed regrade will trigger a DLM reset, at least it has done in my case. Unfortunately this will start a new 12 month contract if you're not currently in one.

2) A broadband engineer or an engineer from Openreach who can perform a DLM reset if they choose to do so.

3) Changing you from their LLU backhaul to WBMC or vice versa should also trigger a DLM reset, it did do when it happened to me a long time ago. But this probably can't be requested just for the purpose of resetting DLM.

There's also one other option but will require a modem that is capable of allowing you to adjust the SNRM target or capping the sync rate, for example the HG612 can cap the sync rate. A high enough SNRM will cause very few errors and ideally over time DLM will recover, though banded lines generally rarely recover or take forever to do so (just error correction most of the time).

Thanks Ixel, that's useful information. I'm, not sure how I can get Openreach to reset DLM - Zen tell me they (OR) wouldn't accept my current position as a line fault. But I will press this point.

If contracting to move back from Fibre 1 to Fibre 2 would trigger a reset, I'd be happy to try that to get back to where I was. A renewed contract wouldn't be a problem, given I'm only 3 weeks or so into the refreshed agreement that started on 1st Sept. The extra cost might be a negotiating point.

I fully intend to be a nuisance about this to Zen - their insistence on providing a new router when taking up the Big Deal offer has resulted in this issue. It's new to them, but it's still their responsibility to resolve. I've no intention of remaining on a limited capacity line, when I know it's capable of better, for the rest of a 2 year contract.

Thanks to everyone who's responded - I appreciate all your advice and info. Feel free to fire away with any other comments or suggestions. It's a small issue in the scheme of things but it's annoying to know that a service is being hobbled because of inflexibility.

You're welcome, and quite right, I would too if I was in your situation. I've been having problems for a while with packet loss/slow single threaded download speed (still am, pending a solution). There was a line fault underground which was apparently resolved but I'm still getting an abnormal amount of FEC errors (which if it wasn't for INP 4 delay 12ms it would be a continuous amount of CRC errors). However I can't push this matter any further sadly as it's a matter of "connection isn't re-syncing or hardly re-syncing at all, speed is fine and no line fault found by the voice engineer or WLR3 test or w/e it's called". This is why I've now ordered a second line with A&A, who have a reputation for getting on BT's back for the slightest problem and not letting go until it's sorted, so I'm kinda hoping the second line shows a problem which is related to the current line's poor error stats.

I had a problem when AVM released 6.80 of Fritz!OS, my line would keep erroring and DLM intervened dropping my banding level every couple of days. Over two weeks I lost more than half my downstream rate: 46 -> 20Mbps.

I enabled the option to use the previous modem firmware and my line immediately stabilised with no errors, and over about 2 months DLM allowed it to rise close to its previous speed. One other person here in the forum saw the same problem and solved it the same way, but others were unaffected (maybe the problem only triggers on lines with certain characteristics?). I reported the symptoms to AVM but haven't seen any movement.

AVM has since released 6.83, but I haven't been willing to risk the upgrade because the release notes don't mention modem firmware changes. If I did upgrade, I'd keep a copy of 6.80 handy in-case I need to rollback.

In reply to a post by DougM:

I had a problem when AVM released 6.80 of Fritz!OS, my line would keep erroring and DLM intervened dropping my banding level every couple of days. Over two weeks I lost more than half my downstream rate: 46 -> 20Mbps.

I enabled the option to use the previous modem firmware and my line immediately stabilised with no errors, and over about 2 months DLM allowed it to rise close to its previous speed. One other person here in the forum saw the same problem and solved it the same way, but others were unaffected (maybe the problem only triggers on lines with certain characteristics?). I reported the symptoms to AVM but haven't seen any movement.

AVM has since released 6.83, but I haven't been willing to risk the upgrade because the release notes don't mention modem firmware changes. If I did upgrade, I'd keep a copy of 6.80 handy in-case I need to rollback.

That's really interesting. Mine was running 6.80 on delivery, and I upgraded it to 6.83 shortly after (during one of the rare periods he line was stable enough to access the update...). I think I'll give that option a go. Shame it takes as long as 2 months (!) to return line speed to what it was before. You'd think there'd be an option to have the DLM reset by the ISP. [censored] Openreach...

In my earlier "dabbling" days, I too would have been tempted to hook up a new modem to see if it could squeeze a few extra mbps from the line. However, having read about the problems of Fritzbox on certain customers lines, I disciplined myself to leave my Zyxel SBG3300 connected and performing a rock solid 30mbps on a 1km line from the cab.

If it ain't broke, don't dabble!!

Edited by ToneDeaf (Sat 23-Sep-17 12:44:39)

I am using an Openreach-supplied Huawei modem. It works well.

If I use my Fritz.box 7390, it works, but the speed is about 10% slower.

I assume that the Huawei cabinet is happier talking to a Huawei modem than to a Fritz!

In reply to a post by ToneDeaf:

If it ain't broke, don't dabble!!

Amen to that, brother!

I didn't really want or need the Fritzbox router, but when Zen sent it anyway, I could hear it shouting at me from within the box and, well, the Devil makes work for idle hands.

The Zyxel is back in for now. Been stable (at the same low speed the Fritxbox was giving) for over a day, which is more stability than the Fritxbox was managing. I'll see how it behaves over the coming days.

Anyone know how DLM decides to allow line speed increases, and how long that takes. Someone further upthread reckoned a couple of months. Hope it's less than that.

In reply to a post by hoopla:

I am using an Openreach-supplied Huawei modem. It works well.

If I use my Fritz.box 7390, it works, but the speed is about 10% slower.

I assume that the Huawei cabinet is happier talking to a Huawei modem than to a Fritz!

I don't think this stuff is an exact science. Certainly, this experience has made me wary of trying different xDSL routers.

In reply to a post by Pablo_Pablovski:

Anyone know how DLM decides to allow line speed increases, and how long that takes. Someone further upthread reckoned a couple of months. Hope it's less than that.

Yep - anything up to a couple of months depending how its feeling..

Edited by IamQ (Sun 24-Sep-17 14:17:39)

In reply to a post by IamQ:

In reply to a post by Pablo_Pablovski:

Anyone know how DLM decides to allow line speed increases, and how long that takes. Someone further upthread reckoned a couple of months. Hope it's less than that.

Yep - anything up to a couple of months depending how its feeling..

Thanks. That's a disappointment. Patience is a virtue, but I might try the line regrade option to provoke things.

One other thing. I notice on the Zyxel that the line is running as VDSL Annex B. I'm pretty sure the default setting on the FritzBox was Annex A, and I hadn't changed it. Would that be something that could cause occasional line drops?



VDSL Training Status: Showtime
Mode: VDSL2 Annex B
VDSL Profile: Profile 17a
Traffic Type: PTM Mode
Link Uptime: 0 day: 11 hours: 33 minutes
============================================================================
VDSL Port Details Upstream Downstream
Line Rate: 9.999 Mbps 24.999 Mbps
Actual Net Data Rate: 10.000 Mbps 25.000 Mbps
Trellis Coding: ON ON
SNR Margin: 7.4 dB 14.1 dB
Actual Delay: 0 ms 0 ms
Transmit Power: 6.4 dBm 13.5 dBm
Receive Power: -8.8 dBm -6.5 dBm
Actual INP: 42.0 symbols 46.0 symbols
Total Attenuation: 15.2 dB 20.1 dB
Attainable Net Data Rate: 11.660 Mbps 41.559 Mbps
============================================================================
VDSL Band Status U0 U1 U2 U3 D1 D2 D3
Line Attenuation(dB): 9.2 40.6 59.9 N/A 18.1 48.6 74.6
Signal Attenuation(dB): 9.2 40.1 59.7 N/A 18.9 48.1 N/A
SNR Margin(dB): 7.5 7.4 7.4 N/A 14.1 14.2 N/A
Transmit Power(dBm): 0.3 - 2.4 4.3 N/A 12.3 7.5 N/A
============================================================================

My Fritzbox is set to annex A

In reply to a post by Pablo_Pablovski:

In reply to a post by IamQ:

In reply to a post by Pablo_Pablovski:

Anyone know how DLM decides to allow line speed increases, and how long that takes. Someone further upthread reckoned a couple of months. Hope it's less than that.

Yep - anything up to a couple of months depending how its feeling..

Thanks. That's a disappointment. Patience is a virtue, but I might try the line regrade option to provoke things.

One other thing. I notice on the Zyxel that the line is running as VDSL Annex B. I'm pretty sure the default setting on the FritzBox was Annex A, and I hadn't changed it. Would that be something that could cause occasional line drops?

So the Zyxel has been in and stable for a week now - zero errors in that time, would you believe.

The line resync'd this morning and speed increased from 25Mb/s to 35Mb/s Zen reckon it might increase a little more over time. They're going to send a replacement Fritz!Box, which I may or may not try. So, I'm happy again!

Thanks to all for the input - all appreciated.

.....I notice on the Zyxel that the line is running as VDSL Annex B....

My Zyxel SBG3300 also defaults to Annex B. There is no way of choosing Annex A in the setup menus.

This does not appear to affect any performance of the modem

VDSL Annex B is nothing to do with ADSL Annex A.

I wasn't considering ADSL

My thoughts were about the VDSL1 standard:-

Symmetric - Annex B
Asymmetric - Annex A

coupled with the fact that the Zyxel and Fritrizbox router/modems mentioned in the discussion were running selected to either standard.

You should check BT Sin 498

Better still, check Recommendation G.993.2 (2015) Amendment 2 (03/16) where Annex B is explained as containing European Band Plans. https://www.itu.int/rec/T-REC-G.993.2-201603-I!Amd2/en Page 315

Edited by deleted (Sun 01-Oct-17 20:41:51)