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Author Topic: can roadworks mess with your line and the dslam?  (Read 7828 times)

arronlowley

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can roadworks mess with your line and the dslam?
« on: May 09, 2017, 04:44:50 PM »

reason im asking as ive been with sky since january, my connection was perfect up until the previous week.

my sync dropped from 70/20 to 49/20 so i rang sky would said they would send an engineer. after a couple of days my sync went up to bang on 60000/20000, meaning of course dlm capped, however i didnt have any interleaving applied which i thought was odd.

today an engineer came, reset dlm to tell me that it would not go back up to my original 70/20 or thereabouts and said the cab was fine and that no further action could be taken although he told me there is something wrong somewhere... why tell me there is something wrong if you cant or wont find the source and fix it.

anyway whats annoyed me is not the fact that my internet is still capped at 60, the issue is the dlm reset has caused interleaving... i thought a dlm reset got rid of interleaving not applied it.

i believe the dlm reset has turned off g.inp, my modem states bearer 0 and my errors are much much higher than before he reset dlm. if i had g.inp wouldnt it state bearer 1? my interleave depth on g.inp was 3 1 or 4 1 and now its 8 1. so im right in assuming the dlm reset has caused interleaving.

roadworks have been going on for the past 1-2 weeks, there are temp traffic lights been used etc close to the cab, could this also be an issue?
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burakkucat

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Re: can roadworks mess with your line and the dslam?
« Reply #1 on: May 09, 2017, 04:51:34 PM »

today an engineer came, reset dlm . . .

<snip>

i believe the dlm reset has turned off g.inp,

A full "circuit recalc" will leave it "wide open" on fast-path. Then, depending upon what the DLM process has noted, G.998.4 (a.k.a. G.Inp) will be re-applied. So, basically, a little patience will be required.

Quote
roadworks have been going on for the past 1-2 weeks, there are temp traffic lights been used etc close to the cab, could this also be an issue?

There is a possibility. But it would be rather difficult to quantify.
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arronlowley

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Re: can roadworks mess with your line and the dslam?
« Reply #2 on: May 09, 2017, 04:54:49 PM »

it just seems odd to me how i was synced at 70/20 since i joined with a noise margin of 6 and now im connected at 60/20 with the same noise margin...

if it was crosstalk it wouldnt say my max attainable is still 70, and surely the dlm reset should have put my sync back up, but it didnt. ive only had these issues since the roadworks began so im pointing the finger. pretty annoyed, when sky put their costs up, im leaving to go to vodafone as i will save £17 a month.

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burakkucat

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Re: can roadworks mess with your line and the dslam?
« Reply #3 on: May 09, 2017, 05:16:53 PM »

. . . im leaving to go to vodafone as i will save £17 a month.

  :swoon:  Are you sure you will be satisfied with Vodafone? Have you read the following three threads?

  :-X
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WWWombat

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Re: can roadworks mess with your line and the dslam?
« Reply #4 on: May 09, 2017, 06:03:37 PM »

it just seems odd to me how i was synced at 70/20 since i joined with a noise margin of 6 and now im connected at 60/20 with the same noise margin...

I don't think you are comparing full apples with full apples.

Right now, it looks like the DLM reset has been of the variety that starts out with interleaving, which may get removed in 2 days - and replaced with either an open profile, or a G.INP profile.

Speculation on here has been that there are 2 types of DLM reset, which behave differently. One of the differences is whether the starting position is "fully open" or "with FEC+interleaving". Another difference is whether existing "banding" (or, as you call it, "DLM capping") gets removed.

You said previously that you were now 60/20 with interleaving. But the act of adding interleaving also adds FEC, which in turn uses some of your bandwidth (10-15-20%). Because some of the bandwidth is used behind the scenes, your noise margins aren't directly comparable with times when there is little or no FEC.

i believe the dlm reset has turned off g.inp, my modem states bearer 0 and my errors are much much higher than before he reset dlm. if i had g.inp wouldnt it state bearer 1? my interleave depth on g.inp was 3 1 or 4 1 and now its 8 1. so im right in assuming the dlm reset has caused interleaving.

Hmm.

The best indication is to look at the "INP" and "delay" parameters, not the depth.

When INP is zero, then DLM has left things wide open.

When INP is in the region of 3-4, and delay is in the region of 8-16, then old-style DLM intervention has turned on FEC+interleaving - and you will get depths of around 1,000.

When INP is in the region of 30-50, and delay is still 0, the DLM has activated G.INP. We tend to see depths of 4 or 8, but other values have been seen - and differences might appear with ECI hardware.
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arronlowley

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Re: can roadworks mess with your line and the dslam?
« Reply #5 on: May 09, 2017, 06:20:47 PM »

Why hello wombat, I also posted on thinkbroadband lel.

Anyhow I've logged into the modem, I have an inp level of 3, delay of 8 and depth of 1181, so I'm guessing this means it's the old traditional Dlm.

Can you explain why the Dlm reset didn't increase my sync? I've had Dlm resets in the past and every time my sync went back to Max with no interleave, however this time it's the opposite and I have both.
« Last Edit: May 09, 2017, 06:29:20 PM by arronlowley »
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ejs

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Re: can roadworks mess with your line and the dslam?
« Reply #6 on: May 09, 2017, 06:43:12 PM »

Were those past DLM resets on FTTC?

The other issue with FEC+interleaving is that the max attainable rate reported tends to be a fair bit higher than the actual rate.
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arronlowley

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Re: can roadworks mess with your line and the dslam?
« Reply #7 on: May 09, 2017, 06:45:13 PM »

yes they were and thats not the case, i was with bt in 2015 and had a connection of 80/20 for the majority of the year and then it dropped to 70/20. i went to virgin media, then left and came to sky in january, had a sync of 70/20 until the roadworks started, my max attainable is still 70/20 as seen in the modem stats.
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ejs

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Re: can roadworks mess with your line and the dslam?
« Reply #8 on: May 09, 2017, 07:02:22 PM »

What I meant was, that with FEC+interleaving, the max attainable rate calculated will be very likely be a fair bit higher than what the line can now manage under its current state and environmental conditions.

So your max attainable is 70/20, and your actual downstream speed is currently lower than that, which is entirely to be expected with FEC+interleaving and how the max attainable rate is calculated.
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j0hn

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Re: can roadworks mess with your line and the dslam?
« Reply #9 on: May 09, 2017, 07:31:02 PM »

With FEC+ interleaving, a max attainable of 70mb and current sync of 60mb, I would estimate the line to get about 65-66mb without interleaving.

Something definitely changed on your line, as it likely won't reach the 70mb you had previously. As others have said the max attainable is over-estimated when FEC+interleaving is applied.

Quote
Can you explain why the Dlm reset didn't increase my sync? I've had Dlm resets in the past and every time my sync went back to Max with no interleave, however this time it's the opposite and I have both.
A DLM reset on an ECI DSLAM still puts the line on fastpath. An engineer ordered DLM reset on a Huawei DSLAM now tend to apply interleaving.
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WWWombat

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Re: can roadworks mess with your line and the dslam?
« Reply #10 on: May 09, 2017, 07:36:12 PM »

What I meant was, that with FEC+interleaving, the max attainable rate calculated will be very likely be a fair bit higher than what the line can now manage under its current state and environmental conditions.

So your max attainable is 70/20, and your actual downstream speed is currently lower than that, which is entirely to be expected with FEC+interleaving and how the max attainable rate is calculated.

As @ejs says ^^^

I'll just add that, if the FEC+interleaving gets removed by DLM, and the line switched to an "open" profile, the sync speed that results tends to be halfway between the current sync and attainable speeds being reported (ie while FEC+interleaving is in place). It would be likely that your line would swap to 65/20 - both in sync and attainable.

HOWEVER...

If your line swaps to a G.INP profile directly, then you might not see this stage. And it is possible that, with G.INP active, you could end up on the same (ie 65/20) speed or higher.

Can you explain why the Dlm reset didn't increase my sync? I've had Dlm resets in the past and every time my sync went back to Max with no interleave, however this time it's the opposite and I have both.

a) BT keep "playing" with DLM. They seem to add features, and change behaviour. At the very least, we've seen changes to cope with G.INP for the last 3 years, including attempts to cope with ECI incompatibilities/faults. We've also likely seen changes to cope with ASSIA patents claims.

b) Last year seemed to bring evidence that (i) DLM resets didn't always get rid of banding; (ii) DLM resets seemed to work in two different ways; (iii) banding was used more aggressively, and (iv) banding sometimes stuck.

I'm expecting DLM to change again this year - at minimum to cope with the 5-4-3dB targets, but likely for ECI G.INP too.

BT don't advertise the behaviour of DLM. All we can do is observe, watch for changes in that behaviour, and try to figure out the reasoning behind it. It is a war that we can only ever come second in.

Your line?
It seems likely that you've fallen foul of both some crosstalk changes and a DLM intervention ... potentially mixed up with the traffic works.
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WWWombat

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Re: can roadworks mess with your line and the dslam?
« Reply #11 on: May 09, 2017, 07:37:31 PM »

A DLM reset on an ECI DSLAM still puts the line on fastpath. An engineer ordered DLM reset on a Huawei DSLAM now tend to apply interleaving.

Oooh. I'd not seen the methods reported as an ECI/Huawei distinction before
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banger

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Re: can roadworks mess with your line and the dslam?
« Reply #12 on: May 09, 2017, 07:55:02 PM »

Indeed my line is now at a 4dB target again but I suspect some banding has been applied to keep sync to 71 as I am seeing lower errors. I think Openreach/BT are still playing with DLM.
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arronlowley

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Re: can roadworks mess with your line and the dslam?
« Reply #13 on: May 09, 2017, 09:02:43 PM »

im not too bothered if my sync doesnt go back up to the full 70 and i know the issue isnt crosstalk otherwise my max attainable wouldnt be the same...

im just bothered about the latency.
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ejs

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Re: can roadworks mess with your line and the dslam?
« Reply #14 on: May 10, 2017, 04:38:32 AM »

If and when the interleaving gets removed, perhaps replaced with retransmission (G.998.4 / G.INP), then the max attainable rate calculated will be lower.
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