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[tnp]

Hi, I stumbled in here, and it looks like at last there is a place to ask questions and get straight answers.
I recently  upgraded to a repackaged ADSL MAX service with Clara net.

I expected issues during te 10 day 'adaptive learning' period, but now thats complete, I have a simple and very irritating problem.

Namely that whilst the BT profile and line are eminently reasonable, my router insists on connecting to the DSLAM at  a speed that is 50% higher than the BRAS is,and as a result the merest flicker of noise causes it to drop out.

Typically it connects at around 3.5dB SNR /5.8Mbps  - which is bleeding edge.

MSR is 4.5Mbps, and BRAS is adsl4000

Why is it connecting above MSR? I thought the point of that was to set an upper limit on connection speeds?

Educate me. I am going nuts.

The router is a lovely faithful old DLink DSL 504: I've got latest firmware and have even manged to poke around with Telnet and set RX gain higher and tune performance: But all that does s cause it to connect even FASTER - still at 3.5db SNR.!!!

I don't want any more speed than I can reliably get. One the few occasions its  trained below 5Mbps, I have got long periods of stability. But if it gets knocked out - and I am on a long line so the odd burst is always going to happen, it insists on starting at a much higher speed, and then I have to suffer intermittent connectivity till it randomly connects at a lower speed.

[roseway]

Hi and welcome.

The default noise margin at the time of making the connection is 6 dB; if the connection is unstable the DLM process should increase the initial noise margin in 3 dB steps up to a maximum of 15 dB. So I rather suspect that you have either a line fault or an intermittent noise source which is causing the noise margin to fall very shortly after syncing, because it shouldn't be less than 6 dB at the time of making the connection.

The other thing which comes to mind is that you say you have used telnet to tune performance. What did you tune? Is it possible that you have set the router to force a lower noise margin on connection? It might be worth doing a factory reset of the router to get it back in its default state.

For info on dealing with noise problems, have a look at http://www.kitz.co.uk/adsl/lowSNR.htm

[kitz]

The MSR doesnt actually do much in the day to day process and its only purpose really is to set your Fault Threshold Rate.  Your router will negotiate a new sync speed each time you connect based on the conditions at the time.
How dsl max works

Like eric, I suspect that you have changed something in the router settings which has amended your Target SNR.  You should be able to get a good indication of what your target SNR is by looking at your line stats immediately after a resync.  If its showing at 3.5db then the margin is probably not sufficient to keep the line stable.
Increasing the Target SNR back to the default value, will have the effect of slightly lowering the speed at which you connect, but give you a larger safety margin of noise before the line disconnects.

[tnp]

Ok, I think I found it, and this being a repository of knowledge and nice guys, here it is for others.

The ISP - Claranet - checked with BT and found that the DSLAM  SNR was maxed out at 15dB.

So that end had done its best.

They suggested that my router was not honoring the SNR negotiation, but in the same sentence almost, noted that 'my connections speeds had gone down as the system responded to lost synchs and increased the DSLAM SNR'.

Which, Mr Spock, does not compute..

So..I went back into the router at the telnet level looking or ANYTHING that would resemble a 'be cocky and aggressive and synch as high as you  dare' command.

Its always the last thing you try...

I upped RX gain but it doesn't make a load of difference..just boosts noise AND signal.

config save AND flashfs update needed to store the changes past a reboot and a power down respectively.

Now instead of synching at a flaky 5.8Mbps, its syncing below my FTR!!! Arrgh!

!!!!! Now I think I need BT to go back to 9dB or re-learn the router..is that possible if I ask awfully nicely? ;-)


This is the generation II D-Link DSL 504 with latest firmware

#telnet 192.168.0.254

Trying 192.168.0.254...
Connected to 192.168.0.254.
Escape character is '^]'.
password: <private>
logged on; type `@close' to close connection.
192.168.0.254> itex
192.168.0.254 itex> enhance 0
Change will have no permanent effect after restart unless you config save.
192.168.0.254 itex> home
192.168.0.254> config save
Saving configuration...Configuration saved.
192.168.0.254> itex line down
Deactivating line...
192.168.0.254> itex line up
192.168.0.254> itex rxgain 6
Change will have no permanent effect after restart unless you config save.
192.168.0.254> config save
Saving configuration...Configuration saved.
192.168.0.254> itex line down
Deactivating line...
192.168.0.254> itex line up
192.168.0.254> flashfs update
Updating Flash filing system ...
done
192.168.0.254> @close

I swear I  never had set flag on..the router came to me factory defaults. I never had occasion to use the telnet interface before now, so the conclusion is that the DSL-504 needs to be tuned to not be a bitch, reliability wise.

To my knowledge this information was not anywhere on the Internet till today.

[mr_chris]

Thanks for sharing that info

Looks like it's quite a configurable little devil really, and the BT DSLAM takes notice of it, perhaps too much so!

I'm sure Kitz will be interested in that info.

Now I think I need BT to go back to 9dB or re-learn the router..is that possible if I ask awfully nicely? ;-)

Well, your ISP should be able to get BT to do this, if you have no joy, Andrew from ThinkBroadband.com (he posts as MrSaffron) has volunteered to accept emails as he has the same kind of access to BT that the ISPs do. If you don't get any joy from Claranet, try emailing  andrew at thinkbroadband.com   (address slightly modified to be spam-proof)

[tnp]

Further update.

Finally having found the 'man who knows' at clara net, today they knocked the noise margin back to 9dB.  I am now connecting at the 'sweet spot' of about 4800 kbps.

But I THINK my BRAS profile is still set to 3000..does this automatically up itself?

Or is this the one where you switch the router off for a minute, and that causes  BRAS reset?

[roseway]

That sounds good. Your IP profile should rise to 4000 in the next couple of days or so. The time it takes is a little indeterminate and could in theory be up to 5 days. If it hasn't risen after that time you will need to contact your ISP to get it unstuck.

[tnp]

Thanks for that. It is consistent with othee comments received from elsewhere.

Oh and thumbs up to Mr Kitz whoever he is for this site.

[roseway]

Mr Kitz is a lady actually, but I'm sure she will be grateful for your comments.

[tnp]

Well that's even better.

[kitz]

thankyee 

[mr_chris]

* mr_chris changes kitz's display name to mr_kitz

* mr_chris runs away very quickly

[kitz]

I prefer sir_kitz

geddit? 

(say it out loud) 

[UncleUB]

Ub humbly kneels before 'The Great One'

[mr_chris]

heh @ sir_kitz

Pity you aren't known as "fitz" then you could be "miss_fitz"