2700HGV not offering the performance over long line

[shpub]

I live a long way from the exchange - 6km- and while switching to IDNET from Tiscali has helped a lot with speed - 750kb from 288kb - I am trying to get as much as possible. I was part of the long reach BT trial in 2003/2004 because of the length!

I've removed the internal telephone connections, used the ADSL face plate etc but the problem seems to be with ADSL2+ vs ADSL.
If I force ADSL with a 834G v5 I can get 890/608 connections. If I use a 2700 v6 it connects at ADSL2+ but only gives 596/500 which is slower.

I can't find a way of forcing the 2700 into a ADSL connection which I think will give a better performance over the long lines as with all my modems, using ADSL2+ decreases the connections speed.

Any ideas/solutions/tips?

[Steve]

 

I'm not a 2700 user . I'm sure you'll get an authoritative answer before too long.

[Simon]

 

And, what Steve said. 

[Ray]

 

[Rik]

Hi and welcome to the forum.

I'd suggest you have a word with support and get them to switch you to Max modulation, it's the easiest way.

[MisterW]

I can't find a way of forcing the 2700 into a ADSL connection which I think will give a better performance over the long lines as with all my modems,

Nope, AFAIK there is no way to force the ADSL modulation mode on a 2700. They usually give very good performance when left to their own devices
but are NOT very configurable. 

[shpub]

Thanks for the replies. I've contacted support re the modulation.

Interestingly enough I found that the ADSLNation face plate knocked about 150kbs off the sync rate compared to the standard BT one. This was on both the 834G with ADSL and the 2700 with ADSL2+.

The 2700 is the only router that connects with ADSL2+.

I'll do some MW radio noise checks and see if that explains the difference. 

[Tacitus]

Interestingly enough I found that the ADSLNation face plate knocked about 150kbs off the sync rate compared to the standard BT one. This was on both the 834G with ADSL and the 2700 with ADSL2+. 

TBH that doesn't surprise me since they contain more electronics than the BT (or Clarity) versions.  Technically I believe they are an 'active' filter rather than a 'passive' one, although someone more knowledgeable will probably correct me.

I've never really understood why people are so enamoured with the ADSLNation version over the BT (or Clarity since they are most likely both made by Pressac) model.  I'm not saying they are no good, but I'm not convinced that in practice they are 'better' in any significant way.  Each to their own I suppose 

[Den]

What time of day are you trying to re-sync? It's better to do it during the week and early in the morning IMO. If I tried at a weekend or later in the day I will always sync at a lower speed. I am about two mile from my exchange and sync at about 7349 at the moment (using a 2700hgv). By the way welcome to Idnetters    

[shpub]

As with a lot of things ADSL, there seems to be a bit of  black art to everything. I had seen good reports about the ADSLnation and thought it was worth a try. The fact that it doesn't work for me in this case doesn't mean that it is an awful product.

I usually resync early in the morning and the 834G seems to be solid at that time. I resynced a couple of times yesterday and it came up with 898/608 constantly.

I do cry a bit when I see comments of "I only synced at 7536" - as I am currently thinking that 750kbs is absolute luxury. To be honest as the 2700 was measuring 78db attenuation, I have to be thankful that it works at all!

I'll keep you updated.

[Rik]

Please do.

[Polchraine]

ADSL2+ will normally give slower speeds only longer (higher attenuation) lines - it is a known characteristic of the modulation.

As suggested, get Tech Support to sort it out and then see what you get from the line.  At a guess it will be better than the DG834 once sorted.

Out of interest, what are the full line stats from the 2700?   Can you post the data from:   http://192.168.1.254/xslt?PAGE=C_1_0

and the last line from Training History on:  http://192.168.1.254/xslt?PAGE=C_5_3

[shpub]

I've just been switched over and the 2700 is connecting in G.DMT mode and my sync speed has gone up. I'm just waiting for the training period/IP Profile to come up but it looks like I could be in the 1 Mbps range which I would have not believed!

There is no Radio MW noise at the master socket but quite a bit by the Mac where the modem is sitting next to several NAS drives. I'll move the 2700 to the master socket and either link wirelessly or by Ethernet cable.

The only other thing I am thinking of trying is a using a non switch mode PSU on the 2700 as I have seen that this can help things as well.

Current DSL Connection:
                     Down          Up
Rate:               1152 kbs   288 kbs
Max Rate:       1272 kbs   788 kbs
Noise Margin:   4.0 dB   19.0 dB
Attenuation:   63.0 dB   31.5 dB
Output Power:   15.9 dBm   12.2 dBm


Protocol:   G.DMT Annex A
Channel:   Fast
DSLAM Vendor Information   Country: {46336} Vendor: {TSTC} Specific: {4101 }
ATM PVC:   0/38

Rate Cap:   1272 kbs
Attenuation @ 300kHz:   63.0 dB
Uncanceled Echo:   -10.4 dB   Ok
VCXO Frequency Offset:   -6.0 ppm   Ok
Final Receive Gain:   34.5 dB   Ok
Impulse Noise Comp. Tones:   0   Ok
Excessive Impulse Noise:   0   Ok




Training data:

Time   Line      Rate   Max1   Max2   Max3   Mgn1   Mgn2   Attn   Pwr   CRCs   FECs   INP   DLY         
BST   1      1152   1280   1276   1276   4.4   4.0   73.0   16.0   1040   0   0.00   0.25   

Rate   Max   Mgn   Attn   Pwr  CRCs   FECs   
288   788   19.0   31.5   12.2   0        0

   Mode                 Vendor   State          Exit Code   Echo   VCXO    Rx Gain   INC Tones
   G.DMT Annex A   TI   236/104   N/A          -10.4   -6.0    34.5           0

[Rik]

My stats on ADSL2+ are 63db attenuation, 6.1db noise margin and 4269 sync, that's also from a 2700. The attenuation increased, inevitably, when I moved to ADSL2+ due to the higher frequencies used. Previously it was 56db. I think your line is clearly only going to support ADSL for the time being, so it might be worth trying a different router if you can to try and improve the sync speed - though the 2700 is particularly good on long lines. Other than that, if you use a DECT phone, it might be interesting to turn that off and see if speeds improve, similarly, disconnect any Sky box etc.

Sadly, I fear, your ultimate fate lays with BT.

[shpub]

I think you are right about my fate being with BT.

However Tiscali/TalkTalk/Opal were adamant that I could only get 288 which is one of the reasons I switched. On a more positive note, I now have several times the speed I had before and it is just about fast enough to watch iPlayer so I am very pleased.

I'll try the Dect phone idea.

Any other router you would suggest? Bear in mind the 2700 was only 99p + postage!

[Rik]

Draytek or Speedtouch, but the former, in particular, is not cheap. However, ask around your friends and see if they would let you try their routers - just don't change more than once a day.

[MisterW]

Rate:               1152 kbs   288 kbs

That looks like a fixed 1Mb connection to me, the 288 upstream is the giveaway!
But then again with only a 4db downstream SNR that's probably just as well, as a ADSL1 MAX may well synch slower.

[jameshurrell]

Yep, i'd agree MisterW... it's a fixed 1Mbps connection....

Also, although I love Drayteks (had several 2600s over the years), they are not fond of long lines (in my experience).

[Polchraine]

Sadly, I fear, your ultimate fate lays with BT.

A bit unfair - even the amount BT invests in R&D is not enough to change the laws of Physics!

[Polchraine]

shpub ...

Now you have an improved speed you should try to minimise resyncs whilst getting a reasonably high speed to ensure the system does not force a higher margin at sync.

I am purely on BT - but at present if I resync at around 20:30 to 21:00 I get 6350 (ish) which translates to a 5500 profile on BT.   That is with a 3dB margin.   As the evening goes on the margin drops to 0dB and occasionally to -0.5 but the line holds up.   During the day it will climb back up past 3 to 6, 7 or even 8dB but if I resync then it will drop out during the night and my sync speed will be under 6000  and a profile of 4500/5000.   

Try a late evening resync - say 20:00 / 20:30 and use RouterStats lite to monitor the connection and see if the line stays synced for 24 hours and what the lowest margin is.

[Rik]

Sound advice. 

[MisterW]

Now you have an improved speed you should try to minimise resyncs whilst getting a reasonably high speed to ensure the system does not force a higher margin at sync.

Hang on chaps... If its a fixed 1Mb connection its either going to synch at 1Mb or not at all! If it synchs then you will get whatever SNR margin the line is capable of at the time, higher in the morning and lower at night.

[Rik]

Good point. 

[Polchraine]

Hang on chaps... If its a fixed 1Mb connection its either going to synch at 1Mb or not at all! If it synchs then you will get whatever SNR margin the line is capable of at the time, higher in the morning and lower at night.

Is it?    In the original post it states:   

I've removed the internal telephone connections, used the ADSL face plate etc but the problem seems to be with ADSL2+ vs ADSL.
If I force ADSL with a 834G v5 I can get 890/608 connections. If I use a 2700 v6 it connects at ADSL2+ but only gives 596/500 which is slower.

That is not a fixed 1Mb  -   so unless the OP has now been put on a fixed connection rather than an ADSL2 he should be able to sync at the best possible rate.

[Rik]

I know, but at:

http://www.idnetters.co.uk/forums/index.php?topic=22013.msg530968#msg530968

the OP quotes 1152/288 as his sync speed, which would appear to be a fixed rate 1M service. 

[Polchraine]

I know, but at:

http://www.idnetters.co.uk/forums/index.php?topic=22013.msg530968#msg530968

the OP quotes 1152/288 as his sync speed, which would appear to be a fixed rate 1M service. 

If he has been moved to a fixed rate service then the OP should get reverted to an alternative as the line looks as though it will support more on the upstream.

[MisterW]

Yes, it will support more on the upstream but from these figures

Rate:               1152 kbs   288 kbs
Max Rate:       1272 kbs   788 kbs
Noise Margin:   4.0 dB   19.0 dB

The noise margin on the downstream is already below 6db. Reverting to a nonfixed connection will certainly increase the upstream but is just going to reduce the downstream since its going to try and maintain a 6db margin at least!.

[Polchraine]

Mine 2700 will sync at 3dB ... so choosing when to resync is vital.   It will drop overnight to around 0dB or maybe as low as -0.5 occasionally and then back up to 6, 7 or 8 dB during the day.     

On a non-fixed rate connection and at the speed the OP could now achieve, every dB or even 0.1dB can be vital in getting a few extra 10s of kbps.      Also, moving back would give a better upstream rate too.

[Rik]

Do you know if you have a 3db target noise margin?

[shpub]

I've been away for a couple of days but the experience with the new connection has not been good as the 2700 has been dropping the line a lot. Restarts every 45 minutes are not uncommon. The 2700 did a superb job of syncing onto the fixed rate but it is hanging on by the skin of its teeth. The amount of errors is high and the sync speeds have dropped significantly over the last few days. While downstream has dropped to 384, the upstream has gone to 484. 

I've tried all the normal tricks with test sockets etc and the conclusion I have come to is that for this particular line, ADSL Max with the NetGear forced into G.DMT mode gives the best combination of stability and speed so I've asked to go back to the original service. 

To be fair, and to quote IDNET... "the line is indeed very long - it is a miracle that it works at all!"

[Rik]

It's true to say that, for some people, ADSL2+ just doesn't work. Unfortunately, no-one can predict the results, it's a case of suck it and see. The good news is that you retain your ADSL2 bandwidth allowance when you re-modulate.

[shpub]

Just a quick update:

IDnet moved me to ADSLMax and the connection speeds with the 2700 went up. Unfortunately the 2700 decided to drop the SNR down to 3db to acheive them and the resulting errors etc caused the exchange to insist on a 15 db snr and a low sync rate: 288/288 was not uncommon.  Even leaving the 2700 connected for several days did nothing and the BT Speedtest results were very strange indeed. It often insisted that I had connected at 8k and my profile was 16k???

It seemed pretty obvious that I was in "BT Jail" without a get out of Jail card. I then got hold of a Billion 7300 which has the ability to override the exchange set SNR and that worked magic. 1024/488 at 7/11db SNR. Unfortunately the BT IP profile was still screwed up and I ended up with a 150k profile!

IDNet got BT to reset the line and the profile is now up at 750k which is what I expect for the sync rate. The line has been up for some 10 days now.


Conclusions:

• The 2700 is too good a modem in that it achieved sync rates that were frankly too high for the line. As a result, the link was not stable and I ended up with a 15db snr. There is no way of really controlling this from the 2700 which is a real pity.
• The 2700's insistence on syncing as high as possible when given a normal 6dB target really caused me problems as it seemed to throw the exchange into apoplexy!. 
• The 2700 data statistics are excellent and proved very useful.


• At 99p + postage of eBAY it certainly was worth trying. 


• If your line is bad - mine has measured 73db at best and 78 at worst attenuation - I think the 2700 is probably too good and without the control to rein it back, it can get you into a lot of trouble. I would suggest getting a modem with SNR control to force the situation into a known working sync rate and snr. I know this is supposed to happen but after my experiences it does appear that taking control from the modem end does provide a lot of benefit.

The end result is that I am reliably syncing at 1024/488, getting a good 750kb transfer rate which is at least 3 times the performance I was getting before. I am extremely happy. So thanks for everyone who guided me through this and I can't praise IDNet support high enough. 

For anyone else who has a really bad line... it does look like a bit of playing around with modems etc will reap benefits.

[Steve]

Whilst I understand overriding the dslam and setting your own margin, I'm still puzzled what happens with relationship between sync and IP profile when you've bypassed dslam margin control.

[Rik]

It's also perhaps worth mentioning that when the scheme to allow ISPs control of DLM parameters launches, you can get the best of both worlds, speed and stability.

[shpub]

Whilst I understand overriding the dslam and setting your own margin, I'm still puzzled what happens with relationship between sync and IP profile when you've bypassed dslam margin control.

So was I as the BT Speedtester results were all over the place. IDNet support were puzzled as well as their line stats were different to those reported by BTSpeedtest.

I think - and I am not totally sure of this - that the ip profile still gets adjusted to suit the sync rate but it doesn't necessarily get reported correctly. For some reason, the settings were screwed up as you can see from the Speedtest data.  It is very puzzling. I was very close to sacrificing a chicken or two over the modem as I could not make any sense of the BT figures I was seeing. Neither could James at IDNet so the chickens were saved. He suggested the reset.  Anyway the good thing is that it worked and I am enjoying a blissful and reliable 750k.

ISP control over the DSLAM... now there's an opportunity. I might just volunteer to try that out.


BT Speedtester results from 4th Sept when I first joined IDNET using Netgear 834G

Download speed achieved during the test was - 648 Kbps
The acceptable range of speeds is             200-1000 Kbps.
Your DSL Connection Rate :                    896 Kbps(DOWN-STREAM), 608 Kbps(UP-STREAM) Agrees with modem snr 6 db
IP Profile for your line is -                 750 Kbps
Best Efforts (BE) classes achieved during the test is - 14.42:23.82:61.76 (SBE:NBE:PBE)

BT Speedtester results from 18th Sept using Netgear 834G

Download speed achieved during the test was - 116 Kbps
The acceptable range of speeds is             1000-7150 Kbps.
Your DSL Connection Rate :                    256 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM) Agrees with modem but the snr was 15db not the normal 6db
IP Profile for your line is -                 3000 Kbps
Best Efforts (BE) classes achieved during the test is - 16.65:24.37:58.98 (SBE:NBE:PBE)
Upload speed  achieved during the test was -  364 Kbps
Upstream Rate IP profile on your line is -    448 Kbps

I could not get any higher sync rates. It was suggested that I used a modem that let me overide the target SNR, hence the change to the Billion.

BT Speed Tester from 21st Sept using  Billion 7300A with SNR overide on 

Download speed achieved during the test was - 119 Kbps
The acceptable range of speeds is             50-250 Kbps.
Your DSL Connection Rate :                    8124 Kbps(DOWN-STREAM), 888 Kbps(UP-STREAM) NB Modem reported 1024/448 snr 7db
IP Profile for your line is -                 274 Kbps
Best Efforts (BE) classes achieved during the test is - 11.95:35.68:52.38 (SBE:NBE:PBE)
Upload speed  achieved during the test was -  349 Kbps
Upstream Rate IP profile on your line is -    888 Kbps


BT Speedtester results from 22nd Sept using Billion 7300A with SNR overide on

Download speed achieved during the test was - 139 Kbps
The acceptable range of speeds is             1000-7150 Kbps.
Your DSL Connection Rate :                    1440 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM) NB Modem reported 1024/448 snr 6.5 db
IP Profile for your line is -                      2742 Kbps
Best Efforts (BE) classes achieved during the test is - 21.86:34.58:43.57 (SBE:NBE:PBE)
Upload speed  achieved during the test was -  363 Kbps
Upstream Rate IP profile on your line is -    448 Kbps

[Rik]

ISP control over the DSLAM... now there's an opportunity. I might just volunteer to try that out.

I already did.

[Tacitus]

It's also perhaps worth mentioning that when the scheme to allow ISPs control of DLM parameters launches, you can get the best of both worlds, speed and stability.

But does that apply both to 21CN AND Max?  My guess is that ISP control of DLM parameters won't apply to the 'old' system, but only to the new.....

[Rik]

It will, Tac, but it's a start. BT may be encouraged to spread it to 20CN if they are not upgrading.