ADSL2+ Reliability Problems

[JamesAllen]

Has your sync rate  dropped recently? You seem to have a margin of 6 currently .I wonder yesterday whether it was set at 3 and the MSAN has decided it was too low and upped it to 6.

I suppose it could have been 6 all along but a swing of 3db is not ideal

Aha I see. It certainly dropped from 6db to 3.2db at around 15:20 or so and has stayed low ever since.

The weird thing is that sync has actually gone up recently - downstream: 15755kbs, upstream: 1132kbs from about 14300kbs downstream.
Although that sync rate has been the same since the last reboot yesterday.

So this kind of noise margin drop could be a sign of potential problems or at least open up the possibility of it being related to my loss of routing every few days?

[Rik]

The only time that the noise margin relates to sync speed is immediately after connection, James. At that point, it tells us the best speed the router could manage for the noise levels around and the target noise margin setting. A lower NM is not a good thing at this time, but lower noise, which provides a higher NM, is.

After that, fluctuations in NM are just showing fluctuations in electrical noise. If the margin has gone up, noise has reduced and vice versa. An NM may, therefore, be at its highest in the morning and lowest through the evening and night hours. Two major sources of noise, and therefore lower NM, are greater propagation of MW radio signals, and greater use of the net as people come home from school or work. This will increase the noise on the line, and reduce the NM.

The use of Routerstats as a diagnostic tells us how much your line fluctuates and shows us a clear time line of the NM and any resyncs forced by it dropping too low.

[JamesAllen]

The only time that the noise margin relates to sync speed is immediately after connection, James. At that point, it tells us the best speed the router could manage for the noise levels around and the target noise margin setting. A lower NM is not a good thing at this time, but lower noise, which provides a higher NM, is.

After that, fluctuations in NM are just showing fluctuations in electrical noise. If the margin has gone up, noise has reduced and vice versa. An NM may, therefore, be at its highest in the morning and lowest through the evening and night hours. Two major sources of noise, and therefore lower NM, are greater propagation of MW radio signals, and greater use of the net as people come home from school or work. This will increase the noise on the line, and reduce the NM.

The use of Routerstats as a diagnostic tells us how much your line fluctuates and shows us a clear time line of the NM and any resyncs forced by it dropping too low.

Thanks for that Rik - perfectly explains it. I was confused by how NM worked but now I see that it's relative to the point at which sync was established. So yeah, the drop I've seen is due to increased noise at around the 15:20 point.

I'm trying to remember if my loss of routing incidents have been after this time - I'll keep an eye on it.

Could this kind of increase in noise (3db change in NM) lead to this kind of problem or is it more likely to lead to a loss of sync?

The strange part of this issue is that sync is not lost at all when I lose routing.

[JamesAllen]

Just to add, I've just noticed that the noise margin is now down to 2.6 / 2.7db.

[Rik]

The lower your noise margin drops, James, the higher the noise which your router is trying to pick out the ADSL signal from. Eventually, it reaches a point where it can't and so resyncs.

Loss of routing should be a completely separate issue, but it could be that, as noise increases you are getting packet loss due to a high error count. It's a bit of a grey area.

[JamesAllen]

The lower your noise margin drops, James, the higher the noise which your router is trying to pick out the ADSL signal from. Eventually, it reaches a point where it can't and so resyncs.

Loss of routing should be a completely separate issue, but it could be that, as noise increases you are getting packet loss due to a high error count. It's a bit of a grey area.

I can certainly see that there are many factors that could be at play here. Thanks again for the info on NM - it's helping a lot.

I think I will upgrade my router to the custom DGTeam firmware soon and see if that fixes the issue. It is very similar to the issue O2 users have experienced and I heard that the custom firmware had a fix in it for that.
Worth a try anyway. It's also possible to tweak the SNR percentage which might be useful.

[Steve]

I pretty certain on BT adsl2+ you cannot tweak the margin unlike o2 LLU implementation. I note of caution with DGTeam their firmware are getting a little long in the tooth compared to recent Netgear, no harm in trying though.

[JamesAllen]

I pretty certain on BT adsl2+ you cannot tweak the margin unlike o2 LLU implementation. I note of caution with DGTeam their firmware are getting a little long in the tooth compared to recent Netgear, no harm in trying though.

Thanks Steve - I'll bear that in mind. I had it in my head that the latest Netgear firmware for the DG834Gv4 was older than the latest DGTeam f/w so will make sure I look into it so I know the score.
I can always roll back if necessary though.

Just hoping I can identify where this loss of routing problem is coming from.

[spyro]

For what it's worth, most of this thread is too technical for me but my internet was enabled on the 11 Nov for ADSL 2+, and thus far the connection rate has been pitiful - under 1 meg. The internet is barely useable. My modem is a - Netgear DG834G v3, Firmware version 4.01.20 - and was provided by idnet.

Having three tabs open in Firefox basically kills the internet and nothing loads. Forget about downloading the latest version of itunes or playing PS3 online. I'm connecting wirelessly and there isn't a problem with the connection between the computer and modem but I'm just receiving barely-there speeds.

I understand that there were some exchange problems over the weekend in the north of England but I'm in Middlesex. Just wondering if anyone else has similar issues ?

I've sent an email to support which I'll be chasing up today but thought I'd throw this out there just incase. Can provide further info if required.....

Thanks

[Rik]

Have you upgraded your router firmware, the v3 is a bit long in the tooth for ADSL2+.

[spyro]

Thanks for the reply. I haven't yet but will do so this evening.

My wife spoke to idnet this morning and was told to make sure the modem is plugged in to the main telephone socket which I don't believe it is at the moment. So will do that too.....

Thanks

[Rik]

Better still, if you have an NTE5 master socket, the type where the bottom portion of the faceplate can be detached, do so and connect to the test socket revealed behind. Note that this will cut off any extensions you have.

[JamesAllen]

Thanks for the reply. I haven't yet but will do so this evening.

My wife spoke to idnet this morning and was told to make sure the modem is plugged in to the main telephone socket which I don't believe it is at the moment. So will do that too.....

Thanks

Hi Spyro,

Also bare in mind that it can take 10 days (I think) for the line to be fully 'trained' which can mean the speed will go up as the day's go by.

You can use the BT speed tester to find out what profile BT currently have to set to which is what could go up as the line trains.

http://speedtester.bt.com/

[spyro]

@ Rik, that is what support said to do so will have a look later on.

@ JamesAllen, thanks for the site, again will have a look this evening. Idnet support said that if necessary, they would ask BT to reset the line so we'll see.

Hopefully it's something simple like updating the firmware and plugging the modem in to the main socket.....

thanks for the feedback.

Alex

[Rik]

Also bare in mind that it can take 10 days (I think) for the line to be fully 'trained' which can mean the speed will go up as the day's go by.

Or down, James. It often starts at its fastest speed and then settles down to a stable speed.

[Rik]

thanks for the feedback.

NP, Alex, we'll be here if you need any help.

[JamesAllen]

Or down, James. It often starts at its fastest speed and then settles down to a stable speed.

Ah that's interesting. I always heard of people starting with slow speeds and then seeing them increase over the training period. Though perhaps that could be down to a previous IP profile being set which was lower than the new line speed or something.

[spyro]

well the speed can't do down any further for me at the moment. It's barely loading the BBC homepage as it is !

Will update later when I've moved the modem etc.

[Rik]

Ah that's interesting. I always heard of people starting with slow speeds and then seeing them increase over the training period. Though perhaps that could be down to a previous IP profile being set which was lower than the new line speed or something.

My current line started optimistically at 4.5M and gradually settled to a realistic 3.5M, James. It's the most common type of training pattern, BT will try to get the fastest speed it can from the line, then adjust down to stable. Sometimes, they adjust down to too stable.

[JamesAllen]

My current line started optimistically at 4.5M and gradually settled to a realistic 3.5M, James. It's the most common type of training pattern, BT will try to get the fastest speed it can from the line, then adjust down to stable. Sometimes, they adjust down to too stable.

LOL, yeah I hear you on that. Playing it a little bit too safe at times.

With my line it started lower but then rose quite quickly. It has over the past week jumped to the highest sync I've seen yet which is surprising. Some of this I think it down to my previous line being ADSL Max though.

[Rik]

Or improvements at the exchange, BT are doing a huge amount of work, I live in hope that some of it may actually benefit us.

[JamesAllen]

Or improvements at the exchange, BT are doing a huge amount of work, I live in hope that some of it may actually benefit us.

Yes that would actually be nice wouldn't it. I sometimes think they do this work just to pass the time or something.
Then again I suppose I can't really complain as it wasn't that long ago that my exchange got upgraded to ADSL2+ after being on Max for years.

[Rik]

Now wait for the fibre.

[spyro]

Morning All

Thought I'd update you on my speed issues. So last night I;

a) Updated the firmware on my modem
b) put a microfilter on the telephone socket where the phone is plugged into ( the modem is plugged into a different socket ). ( I have 3 phone sockets and the 3rd socket is unused ).
c) Moved the modem downstairs as opposed to upstairs.
d) I unscrewed the BT faceplate downstairs to look for the master socket and it wasn't there. Since my house is a new build I have one of those boxes on the outside ( see attached ) so couldn't plug the modem into the master socket ( because i don't have one ).

The end result is that my downloads were much faster. Stable at around 100kbs as opposed to about 3kbs. I didn't get a chance to play the PS3 online nor do a speedtest to get an idea if the overall download speed had increased.

I'll have to monitor it for a few days and see how it goes.... I'll drop a line to support aswell. How easy/hard is it to get BT to come out and check if the wiring is as it should be ? Suppose I'm just curious if the speeds I'm getting are as good as it's going to get ( distance to the exchange etc ) or if there is a fixable issue ( ie a bit of re-wiring ) that could be stopping me getting better speeds.....

Thanks

[Rik]

It's easy, spyro, but they'll bill you. The problem with these external master 'sockets' is that they remain the demarcation point, so no test socket, no ability to do real diagnostics. Contact a local company who offer phone/network wiring and have them check the circuit, it will be much cheaper. From what you say, you do have a wiring issue.