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ADSL2+/ADSL2 - No Increase in Speed

Gigabit

ULTIMATE Member
I recently migrated to ADSL2+ from ADSL Max. My ADSL Max line could sync at 6816Kbps - 7000Kbps approximately and was nice and stable.

I am on a 40dB attenuated line (now 43.5dB with the move to ADSL2+) so I wasn't expecting a massive uplift with ADSL2+, but I have hardly received anything. Below are my current stats on ADSL2 (apparently this is better for my long line, ADSL2+ gives a 200Kbps increase - if that), could anybody help me?


15wb2ud.png
 
Who is the ISP?, there is no reason why you shouldnt be on a ADSL2+ modulation. A 40-45db (to cover everything in one hit) should yield you 8-10Mb (be it ADSL2 or 2+) so something is wrong.

Your upstream attenuation in that screen grab is also a slight (and only slight) concern. Upstream attenuation should be about half of what the downstream attenuation is. Yours at 23.3db may not seem far of but at 23.3db thats almost 15% higher than it should be. (IE around 20db).

Noise margin for your downstream is also a puzzle. I wonder why they have switched you to an ADSL2 modulation from ADSL2+ but left your noise margin at (what is probably a default) 9db? If they alter that (or rather if they can) to 6db i imagine that would yield somewhere in the region of 1.5Mb-2Mb more which would then put your line back in the 8-10Mb category it should be in.

If they can not alter it do it yourself in telnet...
Enable debug via the web interface, goto...
http://192.168.0.1/setup.cgi?todo=debug

Then open a command prompt and telnet into the router, type...
Telnet xxx.xxx.xxx.xxx (the xxxs being your routers IP address think its 192.168.0.1 by default on most netgears)
Enter login and password if asked.

when logged in type the following command
adslctl configure --snr 60

That should drop your downstream noise margin to around 6db, if it doesnt reduce to 6db decrease 60 figure by 10 (IE to 50) if it lowers it too much or the line becomes unstable increase it by 10 (IE to 70).

With a bit of luck im estimating you will be able to get a stable 8.5-9Mb.
 
Rather that post up how long your line actually is, which would enable identification (since there aren't all that many houses here) the line length to the cabinet near The Anchor/Husseys Lane is 2.5km, so add on the extra distance - it's nearly a straight line to you.

The figures you used to get with ADSL1 are a bit surprising at that length. I had ADSL1 with a brand new 400m line on a new estate once and even that only managed an IP profile of 7150kbps.

If you had the noise margin fixed at a lower level than the exchange kit preferred to set it at, did it used to produce errors (FEC errors, I think they're called) but were so minor that the increase in speed was worthwhile?

I'm not expert with things to do with ADSL but one comment I'd make is that the noise margins on the lines in the village are all very high - 15 is normal, and one especially noticeable aspect about the lines round here is that the upstream noise margins are also very high.

I'd put this down to aluminium in the circuits, but, your line was/remains the best performing one in the village (there's one other that's very close behind yours). There are also shorter lines with far worse performance.

Another line not far from you manages 5.2Mbps on ADSL1 and the data showed it should go to circa 6.5Mbps on ADSL2+ (without fiddling around with the noise margins and allowing the DLM to work by itself)

I thought when your migration was completed you were seeing 8Mbps with a fixed noise margin a little below what you have now. I can't help but think this all has to do with our noisy lines round here. If following truthforfree's advice if stable you should be able to nudge your speed up a bit.

This page:

http://www.kitz.co.uk/adsl/max_speed_calc.php

.. shows an expected IP profile of 7620kbps @ a noise margin of 6.0.
 
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Noise margin for your downstream is also a puzzle. I wonder why they have switched you to an ADSL2 modulation from ADSL2+ but left your noise margin at (what is probably a default) 9db? If they alter that (or rather if they can) to 6db i imagine that would yield somewhere in the region of 1.5Mb-2Mb more which would then put your line back in the 8-10Mb category it should be in.

I switched it to ADSL2 myself, it will run on ADSL2+ by default but I read on the internet that I would see no increase with ADSL2+ so that is why I set it to ADSL2. The line was reset by my ISP (Zen) to check for faults. I was running at a 3dB target for a day or so, but it errored a lot so it increased to 6dB, but with only a few resets (perhaps 5 maximum spread over a day) the margin has risen to 9dB.

Apparently DLM on 21CN quickly undoes any changes to SNRM and therefore slows the speeds further, so I am hesitant to do that. But, I won't completely rule this out.

I thought when your migration was completed you were seeing 8Mbps with a fixed noise margin a little below what you have now.

On migration to 21CN I was still on ADSL Max. The only thing that changed was the exchange chipset from ALCB (Alcatel) to IFTN (Infineon). I can only assume that I was able to sync at 8000Kbps was because of better compatibility with my line and/or the modem router I was using (it had a Broadcom chipset - I am using a different modem now but it still has a Broadcom chipset).

Thank you for the advice so far.
 
Stop resetting things your end (if you have been doing so) unless you need to and somewhere in the future switch it back to ADSL2+ altering it your end via the router may just confuse the BT DLM system even more (that will still think its an ADSL2+ line which it is and then wonder why the router your end steps down to ADSL2). Also dunno how long since you switched to this service but you shouldnt do anything (like tweaking or altering modulations) in the first 10 days of using. It sounds like you have had advice previously from elsewhere and it sounds like a fair chunk of it was probably wrong. I suggest you speak to Zen again who are a good ISP to put things as right as they can be.
 
To be honest your stats don't look too bad and a sync of around 7000Kbps isn't outside of normal operation for a 40db ADSL2+ connection. I'd even be worried that too much fiddling might end up doing more harm than good.

Certainly you could sync up to 8-9Mbps+ but all sorts of factors can prevent that from happening in the real-world. Still, do make sure you're using the correct modulation for the new line, and if necessary ask your ISP to run the line re-training period again for 10 days or so (leave your router connected during this period).

The biggest problem here is that ADSL2+ only really starts to make much of a difference at around your level of attenuation or less, which means that any small difference in your environment could easily hamper that. Never the less your speed isn't too bad, it's just right at the bottom of the best for what ADSL2+ can do for that line.
 
I am currently back in the 10 day training period. As previously mentioned, the target SNRM rose to 6dB from an initial 3dB, but with maybe 2 restarts over the course of 24 hours, I am now at 9dB.

I'll get in contact with Zen today and see what they say. I have a feeling that they are going to suggest an engineer as they believe that I am having REIN issues causing the line to error too much, disconnect a lot (although this has been better recently).

I'll keep you updated.
 
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Mark, I completely understand what you are saying, but shouldn't I see some sort of increase (maybe a meg or 2) rather than syncing lower than I was before? Granted, I am at a 9dB margin now. But, I should still see an increase, even at 9dB, and currently I am not.
 
You need to wait the FULL TEN DAYS...... Its called a training period because during that period it will try to find what is best for your line. It may right now be at 9db that doesnt mean its going to stay there. If you dont wait the full 10 days or play around with things during that period you are likely just gonna make things worse.
 
Right, I have been onto Zen this morning and they have told me the best I am going to get with a stable line is 6710Kbps DS. Slightly disappointed but what can you do.

Thanks for your help.
 
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Well, you retain your lead with the fastest fixed line broadband in the village - and you're getting better upstream now which does "feel" different when sending emails with attachments, it's noticeable. If you could get the noise margin at 6 and it was stable, it would be pretty much in line with the spec for a line of that length/attenuation as per the Kitz site estimate.

By the way, you don't have a "long" line (per your previous post), it's actually very near "average", it's just that phone lines are fairly useless for data. Once they're about 3km long the attainable rates start to drop sharply and the performance of all the lines in the village, almost all of which are over 3km long, is very sporadic, they are so very old.

Separately, but related, there's a team of people keying all the village surveys into an online portal I set up and we should be able to run the full analysis on it later this week when everyone's has been keyed in, I'll be interested to see what the answers to the broadband questions were as that's pivotal to our objective of getting a (fast) broadband network in the village.

You might be able to get faster speeds with 3G (as per below) but the performance of that is sporadic - 6Meg to 12Meg down, 1Meg to 3Meg up, so it won't always outperform what you have, and the jitter (variable latency) isn't good for gaming. That and you have to be careful what you use since it's not unlimited, and it takes a long time to fine tune it to get the best speeds. if we could get 6Mbps+ via our phone line I'd probably use that.

In the meantime if you didn't mind sacrificing your extra upstream, and you were seeing 8Meg down with ADSL1, could you not simply put the modem back in ADSL1 mode?
 
......
In the meantime if you didn't mind sacrificing your extra upstream, and you were seeing 8Meg down with ADSL1, could you not simply put the modem back in ADSL1 mode?

Id suggest if he is on any type of reset period or a training session to leave things well alone until thats over. Fiddling while the lines trying to find its best setting is just asking for more grief.
 
The really good thing is that I have a really great ISP, Zen, who are generally doing their best to help. If anybody from Zen is reading this, thank you for your help so far!
 
By the way, did this ever happen? Story below:

Internet providers that use BT Wholesale based broadband ADSL / ADSL2+ lines ( e.g. AAISP , Zen Internet , BT , PlusNet and many more) will soon gain direct control over their customers line speed settings (DSLAM profile).

The move could allow ISPs and, in some cases, customers more control to determine whether or not to get the best speed possible out of their broadband connection or to prioritise stability.

At present BT uses Dynamic Line Management (DLM) to determine the best speed as a balance between performance and stability, yet despite recent improvements (here) this solution doesn't always get it right. It can thus be beneficial for an ISP or end-user to have more control.

The Director of AAISP UK, Adrian Kennard, explained:

"In some cases the DLM makes matters a lot worse than simply picking some settings and leaving them. It is also impossible to properly tell the DLM what the customer wants - some people want the highest speed, but they know that the line will go off line at high speed every night and don't care as they are asleep! Some people must have a line that is reliable and really do not mind if it is set to only 500K if it works all the time.

These are extremes, but especially with reliability the DLM itself causes resyncs and changes in the name of keeping the service reliable! In some cases the line characteristics mean the DLM cycles through different settings over a period of several weeks - thinking it can do better and then finding it cannot over and over again."

A number of major unbundled ( LLU ) broadband platforms, such as those operated by BE Wholesale, have had this feature for years and AAISP claims that BT will now finally be introducing it onto their own network in December (date yet to be finalised).

In most cases ISPs will probably seek to retain control over this, although AAISP is already looking to give end-users the ability to adjust their line speed (i.e. turn DLM off) as and when required.
 
I don't know. But these people might. There's a thread very pertinent to your situation here:

http://forums.thinkbroadband.com/btsupplier/3610069-snr-margin-tweaking-on-wbc.html?fpart=all&vc=1

And, yes, Zen are very good. They were who we used when we had the 400m line, and also who we used here when we had our narrowband ADSL connection ;) and they delivered every bit of that 1750kbps the line could manage. Perhaps you could say that you're prepared to tolerate (possible) instability and want the speed increase, and, is it possible to fix the SNR @ 6.0?
 
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Good question. I assume that BT based ISPs now have that control as it was due to happen in December but we never saw another update. It's one of those changes that seems to happen behind closed doors. I'll ask AAISP as they're bound to know, unless somebody else responds first.
 
Ok the answer from AAISP's MD is:

"Well, not directly. We have more controls on an SNR reset which allows some settings to be pinned down. But the big issue is that these settings cannot then be changed for 10 days. This makes it very risky as it can leave a customer stuck with settings that don't work."
 
Perhaps you could say that you're prepared to tolerate (possible) instability and want the speed increase, and, is it possible to fix the SNR @ 6.0?

I did ask them and they said it wasn't possible. If one of their reps could come on here, e.g. LeeH (?) they could confirm this.

LeeH did PM me, but I can't respond as his inbox is full! Mark.J, could you tell him to clear his inbox if possible?
 
I did ask them and they said it wasn't possible. If one of their reps could come on here, e.g. LeeH (?) they could confirm this.

LeeH did PM me, but I can't respond as his inbox is full! Mark.J, could you tell him to clear his inbox if possible?

Sorry, I have made some space now
 
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