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Author Topic: High Interleaving  (Read 4230 times)

KingJ

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High Interleaving
« on: January 24, 2018, 08:23:11 PM »

Hi folks,

Around 4 months ago, I moved my FTTC line to a different property, sticking with Zen. My line is pretty stable but towards the lower end of the speed estimates.

I've been logging my stats up to MyDSLWebStats since the line went live and things generally seem OK;

  • SNR ranges from 5.8-6.2dB downstream and 6.1-7.4dB upstream
  • Errored Seconds per Hour tend to be 0-2
  • Attenuation constant 16.4dB
  • hlog shows a nice smooth exponential curve
  • Rarely resyncs - most resyncs have been because i've powercycled the modem and I rarely do this. There's only been one DLM initiated resync in the last few months (which I think was due to my SNR being above target)
  • Roughly 450m from the cabinet, by road rather than as the crow files

However, my actual sync speed is around 10-12mbit below the modem's 'attainable' speed stat and my interleaving is set at what seems to be weirdly high - 1,432 down and 363 up. It also seems a little odd that even though the line has been active for over 4 months and i'm connected to a Huawei cabinet i've not had G.INP applied or had the target SNR decreased from 6 dB. I know this can take a little bit of time to apply, but poking around a few other threads on here it seems most people have had it applied by the 4 month mark on a new line.

I'm not sure if i'm misreading the stats and my line is actually performing well, but the high interleaving seems a little off to me given the stability of the line. I would appreciate if anyone can offer any insight! I'm currently using a Zyxel VMG1312-B10D in bridge mode, having switched to that from a HG612 around 2 months ago. The modem is connected directly to the master socket, there's no internal phone wiring connected. I did try performing a quiet line test and I heard a bit of static, however this could be because i'm using a cheap Argos Value cordless phone - unfortunately I don't have any other phones to test with! I did ask Zen about this too, but they mentioned that things seem to be all OK from their side without elaborating exactly what they checked.

Stats are available on MyDSLWebStats under the same username I use here. There is a G next to my name, but that's from when I was uploading under this username from the previous property, whose FTTC line was G.INP enabled!

Many thanks  :)
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Ixel

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Re: High Interleaving
« Reply #1 on: January 24, 2018, 11:47:54 PM »

Although I can't really offer a comment on your situation, I just want to point out that interleaving depth isn't a measurement you can use to determine if interleaving is high or not. Interleaving depth varies on a number of factors, but most importantly the sync rate, delay and INP values will adjust the interleaving depth.

To determine if you have 'high interleaving' it would be more useful to know what your delay and INP values are instead.

From your stats on MDWS I can see that you have an INP of 3 and a delay of 8ms on the downstream and an INP of 4 and a delay of 8ms on the upstream.

The lowest INP and delay applied by DLM is 3 with 8ms. This means your upstream is slightly higher than the lowest possible 'interleaving' that DLM applies.

The only thing I can say is that you're getting a reasonable amount of FEC errors per minute. I don't really know if DLM uses this as a possible way to say "no the line can't support lower INP/delay or such" or not, but my gut feeling would say that somehow it does as you appear to have been stuck on interleaving for some time. I also notice you're on a Huawei DSLAM, these support G.INP and 3 dB. I'm surprised your connection hasn't been switched to G.INP but there must be a reason I suppose. In the past the only way I've managed to encourage DLM to take positive action is by temporarily capping the connection sync rate on the modem myself, then leave it for a week or two (or a little longer).
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j0hn

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Re: High Interleaving
« Reply #2 on: January 25, 2018, 12:37:10 AM »

My recommendation, if you can go a few days with a little less speed....

Cap the sync at 40Mb/14Mb
Leave it for a few days. Hopefully it will give DLM a kick and put the line on fastpath.
If there's high enough errors on fastpath it might apply G.INP.

I believe the command for your modem is..
adsl configure --maxDataRate 40000 14000 100000

It took 11 weeks for DLM to give me G.INP.
I was interleaved most of that time. A few days after I capped the line and shook interleaving I finally got G.INP

Or you can just wait patiently.
The default is that all lines with compatible modems should get G.INP but DLM seems to forget the odd few lines here and there.
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BT FTTC 55/10 ECI now Huawei cab
Zyxel VMG1312-B10A bridge mode with 1508 MTU + Asus RT-AC68U running Asuswrt-Merlin

KingJ

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Re: High Interleaving
« Reply #3 on: January 25, 2018, 02:19:04 PM »

Although I can't really offer a comment on your situation, I just want to point out that interleaving depth isn't a measurement you can use to determine if interleaving is high or not. Interleaving depth varies on a number of factors, but most importantly the sync rate, delay and INP values will adjust the interleaving depth.

Ah oops! I didn't realise that, thanks for the explanation!

From your stats on MDWS I can see that you have an INP of 3 and a delay of 8ms on the downstream and an INP of 4 and a delay of 8ms on the upstream.

The lowest INP and delay applied by DLM is 3 with 8ms. This means your upstream is slightly higher than the lowest possible 'interleaving' that DLM applies.

Interesting, so based off this DLM has applied interleaving, but at quite a low setting - so it's not quite as bad as I first thought.

My recommendation, if you can go a few days with a little less speed....

Cap the sync at 40Mb/14Mb
Leave it for a few days. Hopefully it will give DLM a kick and put the line on fastpath.
If there's high enough errors on fastpath it might apply G.INP.

I don't mind loosing a little bit of speed for a few days it it ultimately results in a long term gain. I've just run the command you've posted and it appears to have worked - the modem resynced and is currently connected at 40Mb/14Mb;

Code: [Select]
$ adsl info --state
adsl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    0
Last initialization procedure status:   0
Max:    Upstream rate = 21489 Kbps, Downstream rate = 69676 Kbps
Bearer: 0, Upstream rate = 14000 Kbps, Downstream rate = 39994 Kbps

If this does kick DLM in to gear, what should I expect to see in the next few days? Should DLM initate a resync and override the cap i've put on, or will I need to manually resync in a few days time to see if it's worked?

Thanks both for your help and explanations!
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j0hn

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Re: High Interleaving
« Reply #4 on: January 25, 2018, 03:00:41 PM »

DLM should resync the line. My guess would be 2-3 days time.
The stats would show: Last Retrain Reason: 1 RDI

It will resync with the cap still in place. You need to reboot the modem or send another command to remove the cap.
Watch for a change in INP/Delay.

I'm pretty confident it will put the line back on fastpath.
Since your resync with the cap FEC's have dropped from around 5000/hour to practically nil. ES should also be much lower but after only an hour that's harder to tell.

If DLM removes interleaving (I think it will) I recommend you then remove the cap. ES numbers should shoot up quite a bit.
Then hopefully within a couple weeks DLM will apply G.INP.
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BT FTTC 55/10 ECI now Huawei cab
Zyxel VMG1312-B10A bridge mode with 1508 MTU + Asus RT-AC68U running Asuswrt-Merlin

KingJ

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Re: High Interleaving
« Reply #5 on: January 25, 2018, 03:26:04 PM »

DLM should resync the line. My guess would be 2-3 days time.
The stats would show: Last Retrain Reason: 1 RDI

It will resync with the cap still in place. You need to reboot the modem or send another command to remove the cap.
Watch for a change in INP/Delay.

I'm pretty confident it will put the line back on fastpath.
Since your resync with the cap FEC's have dropped from around 5000/hour to practically nil. ES should also be much lower but after only an hour that's harder to tell.

If DLM removes interleaving (I think it will) I recommend you then remove the cap. ES numbers should shoot up quite a bit.
Then hopefully within a couple weeks DLM will apply G.INP.

Wow yeah, i've just had a look at the B0 FEC graph myself and I had no idea it was that high before. To see it come down so dramatically is quite impressive.

I'll keep an eye out for a resync and then try and remove the cap after that, thanks for the information.

What's the best way to tell what 'path' my line is currently on?
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ejs

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Re: High Interleaving
« Reply #6 on: January 25, 2018, 07:56:46 PM »

The max attainable rate calculated while FEC/interleaving is on tends to be higher than what's actually possible. If FEC/interleaving gets switched off, I don't think you'll get what's currently reported as the max attainable rate.
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KingJ

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Re: High Interleaving
« Reply #7 on: January 27, 2018, 08:28:10 PM »

DLM hasn't kicked in yet to resync the line, but it's only just been 2 days since I applied the cap so not expecting much yet!

Interestingly I had a huge burst in FEC errors over around 4 hours this afternoon, for no discernible reason. Things are back to normal now though with just a handful, odd all the same though!

Hoping DLM kicks in within the next couple of days and i'll update the thread when it does.
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jaydub

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Re: High Interleaving
« Reply #8 on: January 28, 2018, 12:00:17 AM »

The max attainable rate calculated while FEC/interleaving is on tends to be higher than what's actually possible. If FEC/interleaving gets switched off, I don't think you'll get what's currently reported as the max attainable rate.

Having just had almost two days of interleaving, that was my experience.

The max attainable was showing as higher with interleaving on than it was either before the interleaving kicked in or afterwards.
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KingJ

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Re: High Interleaving
« Reply #9 on: January 29, 2018, 08:35:18 PM »

So exactly 4 days and 49 minutes after I applied the cap, my line resynced during the day today with a reason of "1 Remote Defect Indicator/DLM"!

My downstream B0 INP value dropped from 3.5 to 0, so presumably that means Interleaving was removed? The upstream however has the same B0 INP value of 4. Tonight, I rebooted the modem to remove the cap and resync it and it resynced at 64mbit - a good 4mbit higher than before. As predicted by ejs too, now that interleaving has been removed the modem's predicted 'attainable' speed is now much closer to the actual sync speed (within 1mbit on the downstream).

So, everything's looking much better now! Hopefully within the next few days (upto 14?) DLM will kick in again and apply G.INP. My errored seconds have already shot up to 60.

Thanks everyone for your help so far, i'll keep this thread updated with how things go :)

I've also ordered a VMG1312-B10A to see if it performs any better on my line than my current VMG1312-B10D, but I won't swap it out until the line has stabilised so as not to be changing too many variables at once.
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j0hn

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Re: High Interleaving
« Reply #10 on: January 29, 2018, 10:40:00 PM »

Excellent news. The downstream has returned to fastpath (No INP/interleaving/delay). Unfortunately the upstream is still interleaved but I'm not too surprised at that as it had a higher level of INP than the downstream.

Hopefully G.INP won't be too far behind. Fastpath gives higher sync and lower pings so still better than it was.
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BT FTTC 55/10 ECI now Huawei cab
Zyxel VMG1312-B10A bridge mode with 1508 MTU + Asus RT-AC68U running Asuswrt-Merlin

KingJ

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Re: High Interleaving
« Reply #11 on: January 31, 2018, 03:23:33 PM »

Unfortunately, DLM has just resynced the line again and interleaving has been applied back to the downstream. Sync has dropped and B0 INP is now back to 3.5 again. This happened just over 48 hours after DLM resynced the line to remove interleaving.

I wonder why it reapplied it? Do you think perhaps the fact I still had upstream interleaving even when capped meant that DLM never really 'forgot' about interleaving my line as a whole?

I'm willing to try recapping my line again, but would be interested to hear any suggestions first!
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V_R

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Re: High Interleaving
« Reply #12 on: January 31, 2018, 03:52:05 PM »

As an amateur, I'd say it was due to the huge amount of ES on the line.
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Zen Internet (80/20) on a Huawei 288 cab, via HG612 and an Asus RT-AC86U running Merlin FW.

KingJ

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Re: High Interleaving
« Reply #13 on: February 04, 2018, 06:01:08 PM »

Before I had a chance to re-apply a cap, the VMG1312-B10A arrived and so last night I ended up swapping the VMG1312-B10D for the VMG1312-B10A to see if it makes much of a difference.

Although not without problems, overall i've gained ~1mbit of sync. Attenuation has jumped from 16.4dB to 17.2dB which I understand is to be expected given the extra filtering built in to the VMG1312-B10A.

Interestingly though, both the bitswaps/min and the B0 FEC count has significantly dropped by about 5-10x, which is unexpected. Nothing else has changed in the interim so presumably this is all down to the improved filtering and chipset.

I'm going to leave the line for a few days, and then if DLM hasn't taken positive action i'm going to retry putting on the cap again but at a slightly lower setting, especially on the upstream.
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KingJ

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Re: High Interleaving
« Reply #14 on: February 06, 2018, 01:29:21 PM »

I've just had DLM resync my line... and apply G.INP! Finally!

Sync has jumped up about 10mbit on the downstream to 69mbit, and up 3mbit on the upstream to 20mbit. With G.INP applied, interleaving has also gone away.

I'm wondering what ultimately made it happen? Was it the capping that partially removed interleaving for a few days? Or was it switching the modem from the VMG1312-B10D to the VMG1312-B10A and the susbsequent reduction in FEC error counts? Given the mystery around DLM i'm sure i'll never quite know what ultimately did it, but overall i'm very happy that i've finally had G.INP enabled, with the benefits to sync and latency reduction that it brings.

I'll keep an eye on things now to see if I get a reduced SNR applied too now that G.INP is enabled.

Thanks everyone here for their help!
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