Kitz Forum
Broadband Related => ADSL Issues => Topic started by: holmbase on August 16, 2009, 09:57:39 AM
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I have not had to refer to Kitz for more than two years now as my line problems from 2002 - 2006 turned out to be a faulty line card in the exchange. Anyway, problems have returned.
My exchange was upgraded to 21CN 11 days ago. Almost immediately, it all went wrong.
On the old 20CN/ADSL1 my ST546v6 router reported attenuation of about 49db and SNR of around 13db. I have had a bras rate of either 2.5M or 3.0M for most of the last two years. My link was 'stuck' at a target SNR of 12 or 15db because of the previous problems on my line and my ISP seemed a bit reluctant to get it reset in case it caused problems.
21CN changed all that. My faithful Thomson ST546v6 held the 3,000kbits sync rate for about 12 hours, then it dropped to 1,495 kbits where it stayed. I then tried a Voyager 220V which also sync'd at 3,000kbits before being dumped back to 1,495k. My last throw of the dice was a Billion 7402R2 which also sync'd at the higher rate before being dumped down to - you've guessed it - 1,495 kbits. As you can imagine, my bras dropped to 1.25M.
At that point I raised a call with my ISP who started to chase BT and that's ongoing. After a lot of fiddling around, I've now got the Billion router syncing at 2,270 kbits which is only good enough for a 1.75M service, although this is below the FTR and MSR. WBC regularly reports a potential speed of 3.5M.
My question to you is what router could I try using to improve the compatibility with the exchange? (Assuming BT don't sort things out)
The old exchange equipment was alcatel (ALCB) and the Thomson seemed very happy with that (much better than my old DG834v2 or a Zyxel I had). The new equipment appears to be Texas Instruments (TSTC). Is anyone aware of a router chip, and therefore an adsl router, that is known to be good with TI exchange equipment?
I still have my old DG834 which is a TI AR7 chip but that doesn't seem to cut the mustard. Both my Broadcom routers seem to struggle to get beyond this mystical 1,495 kbits. The Billion is okay but it's still poor. What other routers might I try?
Of course it could be a line fault but as the problems started immediately after the 21CN exchange, I'm guessing it's an exchange related issue - which BT might solve........................or not.
Here are the figures from my router and from the adsl checker.
Connected as ADSL2A
Down sync 2270500
Up sync 447000
Attenuation down 45db
SNR down 17.5db
Attenuation up 28.5db
SNR up 23.5db
Distance from exchange direct - 1.43km
Distance by road - 3.06km
Max speed data from calculator
Line length 3.3km
dslmax 5,888 kbps
adsl21 21CN 7,200kbps
I have no phone extensions and the router is plugged directly into the socket at the moment, although I usually use an ADSLNation faceplate.
Any ideas welcomed.
Thanks
John
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Hi Holmbase and welcome,
On the basis that I think BT are still providing 2Wire 2700 HGV on their business broadband services and that is TI AR7 based, that might be one to try as it should hopefully compatible with any BT 21CN offerings ? Amazon seem to have the occasional new sealed boxes for sale.
However there do seem to be rumblings of various 21CN problems around so perhaps it would be worth waiting to see if a generic problem is eliminated first?
Over to the Gurus now !
Kind regards,
Walter
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Another option could be to use your current router and for the moment try forcing a different modulation (ADSL or ADSL2) rather than your current ADSL2+
I'm assuming this will be possible with the BT equipment - perhaps someone could clarify?
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Another option could be to use your current router and for the moment try forcing a different modulation (ADSL or ADSL2) rather than your current ADSL2+
I'm assuming this will be possible with the BT equipment - perhaps someone could clarify?
I've sort of done this - I'm currently using "ADSL2, auto-fallback" which is what got me the current speed. I couldn't find the equivalent option in the two other routers.
How does swapping to ADSL make a difference? (Excuse my ingorance)
John
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>> Texas Instruments (TSTC)
Indicates that you may possibly be on one of the Huawei MSANs... which from reports seem to be the most problematic for 21CN :(
>> I'm assuming this will be possible with the BT equipment
Should be - if the router allows.
>> Attenuation down 45db
Normally its most advantageous if the attenuation is 50dB+
adsl2+ uses some higher frequencies, which can attenuate the line more... there comes a point at around 55dB when adsl2+ doesnt seem to offer any benefit over adsl1.. and some users 'in the 50's' find adsl1 works best.
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When you tried your DG834Gv2 was it using the latest Netgear firmware version (3.01.38)?
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When you tried your DG834Gv2 was it using the latest Netgear firmware version (3.01.38)?
Yes - I had just upgraded it. The sync was around 3,000 kbits but performance was awful. Web pages taking 5 minutes to load or just stopping in the middle. Unusable. Moment I swapped back (to the Voyager 220v as it happens) sync dropped but I could now use the internet again. As I say, now on the Billion as best of bad bunch at the moment.
Will try going down the ADSL1 route but not sure when. I don't want to fiddle too much just yet in case BT are really on the case.
John
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Hi,
My DG834v2 3.01.38 also was not at all happy with the change to ADSL2+.
Now using ST546(i)v6 6.2.17.5 which is OK.
Vendor ID (Local/Remote): TMMB / TSTC
Maybe your DG834 performance hit due to lots of CRC errors.
Cheers,
Peter
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Hi All,
There is a large number of incompatible routers on the market at the moment and it seems there does not appear to be any solid answers as to why. I have noted it is not the AR7 only that is having issues, but more over it is the Broadcom chip that is having issues wth the Bit Swapping request. When i get 5mins, I'll sit down with Kitz and pick her brains.
We are currently performing testing on the 21cn lines, as we are slowly migrating our customers to the new MSANS capped @8mb due to other issues on the BT Side of the fence.
Once we have more information I will of course post it here, and please do keep posting your findings as this can only lead us to a resolution.
Kindest Regards,
Leo
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Oh BT take the biscuit.
They have lowered my FTR and MSR so that my now slowly connected line exceeds both those limits. So now BT can claim the line exceeds minimum thresholds so job done, fault cleared, move onto the next problem.
How can one challenge the FTR and MSR? Do you know?
John
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Hi Holmbase,
I think Azzaka will suggest you to politely but firmly refer BT to your "before and after" statistics and then escalate the problem.
Kind regards,
Walter
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Agreed Walter,
Your ISP will need to address this with the helpdesk and this will then be reversed. It is Unacceptable and Zen have addressed this issue and believe me it took awhile but we dont have the issue anymore and they should be aware of this and reverse it.
Any problems PM me and I will try and give you more advise.
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I have obtained a 2700 router from ebay and just set it up in the last couple of days. Strangley, whilst the noise margin is the same as my previous routers (around 16db), the attentuation has shot up from around 45db to 56.5 with this router.
What's with this change? Is there a reason why the 2700 would report a much higher attentuation?
Even so, the Kitz calculator suggests I should be getting 3M, which I'm not. Connection rates are no better and BT have resolutely left my MSR and FTR much lower than under ADSL1.
Openreach engineer arriving tomorrow although I don't know what use he'll be.
John
Hi Holmbase and welcome,
On the basis that I think BT are still providing 2Wire 2700 HGV on their business broadband services and that is TI AR7 based, that might be one to try as it should hopefully compatible with any BT 21CN offerings ? Amazon seem to have the occasional new sealed boxes for sale.
However there do seem to be rumblings of various 21CN problems around so perhaps it would be worth waiting to see if a generic problem is eliminated first?
Over to the Gurus now !
Kind regards,
Walter
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Ive no idea why the 2700 would report the attenuation as so much higher. Different routers can report across used/all available tones... but you wouldnt expect it to be that much. If you swap back to one of the others does it still report the lower figure?
There seems to be so many problems with 21cn that I see one very reputable ISP is giving up on 21cn an now looking at using LLU if available.
Ive just noticed that you with the same ISP.. and at least the only consolation that I can give is that they are one of those that will try their damnedest to get BTw to sort it.
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Update.
Openreach came Wednesday and we quickly agreed it was not a line fault. He went to the exchange and reported my connection rate of 2.2mbps was far too low to the BT people - who reset my line, after which, I immediately reconnected at 5.8mbps and 6db snr - per my 2700hgv.
Then lots of things went wrong.
The RAS failed for 5 hours, causing the router to continually try and get a login and failing - which caused lots of disconnects and slowly reducing speeds at constant 6db snr.
I didn't know the RAS had failed so tried three other routers which didn't help.
Once the RAS was up, the router (which I was monitoring with Routerstats Lite) lost both line speed and snr on a regular but random basis - sometimes every 30 minutes, others almost every other minute. I don't think this always meant a line down though as the router seemed to be having problems..........
.....latency started to follow a bizarre pattern. See the lcp chart which I have attached. The green bit is the lcp echo response chart provided by A&A.
Oh, and I seemed to have bucketloads of errors of all types randomly.
So all told the exchange got a bit upset and on Friday increased my snr to 9db and then 12db with the resulting drop in connection rate to 4.2mbps. But I was stiill seeming to have these complete drops of line speed and snr to zero and this odd latency problem.
So today, I put my trusty ST546 back on line. Although it only connected at 3.9mbps, it does not seem to have had these losses of line speed and snr (monitored with 'yet another modem tool'). The latency problem has gone, which must mean it's a 2700hgv router problem although I don't know quite how.
So where I am is that I am now about back to where I was prior to the 21CN upgrade. I guess once the line settles down, if it stays at 3.9mbps, I will get a bras rate of 3.5M (maybe 3.75M???). But no great shakes over ADSL 1.
The most amusing bit is that I have two openreach engineers out, neither of whom have had either training or new kit to help them deal with 21CN exchanges. Their brief is to test the line and walk away - presumably so that BT can get into a little tennis match "it's not the line, it must be the exhcange - oh no, it's not the exchange it must be CPE or wiring - no, it must be the line". I was lucky that engineer 2 went a bit beyond his remit.
BTW Kitz, on Wednesday, my billion router still reported 45db attentuation on Wednesday but today, the 546 is reporting 53db. Is attentuation somehow related to line speed/snr?? I'm not putting the Billion back on just yet as the line needs to calm down.
I also enclose a shot of the diagnostics page from the 2700hgv as it contains a bit loading chart. There is a dip about an inch in - is this the kind of thing that would have caused those snr dropouts? The ST546 has a similar chart. I know nothing about bitloading.
John
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>> my billion router still reported 45db attentuation on Wednesday but today, the 546 is reporting 53db.
attenuation (http://www.kitz.co.uk/adsl/linestats.htm#attenuation) normally relates to line length, but there are other things that can affect attenuation. Such as aluminium joints on the line.. or a HR fault.
Different routers can measure attenuation differently - depending whether its averaged.. or taken at a specific frequency.
ADSL2+ normally sees an increase in an attenuation over ADSL1 due to the fact that adsl2+ has a much larger frequency range in use.. and its not unusual to see an increase of around 3dB.
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>> I also enclose a shot of the diagnostics page from the 2700hgv as it contains a bit loading chart.
The graph seems to show some frequencies were the signal is poor.. theres a small gap at tone 160.. and some further on at around 205 - 215ish.
These dips will correlate to the SNR levels at those frequencies. One of the usual causes is some sort of ElectroMagnetic Interference.
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@ Holmbase,
When you mention the dip about an inch in, which I presume is the gap at tones 31 & 32, I suspect that is the gap between the upload and download portions of the tones used.
If so, it would not have any effects elsewhere ?
Kind regards,
Walter
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In the stats 2700HGV is showing a downstream attenuation of 48.6 dB @ 300 kHz - perhaps a bit more realistic?
I think that tone 160/161 is around the radio 5 frequency of 693 kHz.
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I think that tone 160/161 is around the radio 5 frequency of 693 kHz.
Yes, that one seems pretty common. I see it on my own connection. I guess that Radio 5 Live transmitters are all over the place and quite powerful.