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[Edinburgh2]

I am suffering very low throughput for download on my broadband line.  I have BT Option 3 with a good quality line which can synchronise at over 8Mbps.  

I have posted my problem on the BT Forum at:
http://www.beta.bt.com/bta/forums/thread.jspa?threadID=4626&tstart=0

But it appears to be defeating the best brains there, as well as the BT Help Desk.  One poster there suggested very helpfully that I ask this forum for help.  Any bright ideas here would be welcome.

My symptoms are:

*  Download speeds during the working day and evening vary:  (~300kbps - 2Mbps)
*  Download speeds at about 5am can reach ~5Mbps
*  Synchronisation speed is solid at over 6Mbps
*  IP profile is solid at 5500 kbps (was higher, but constantly restarting the hub has dropped it).
*  I have BT Vision.  The video-on-demand is jittery during the working day and evening, but I can get it to stream video successfuly at about 5am.

Suggestions?

[jid]

Firstly, could you post the stats from your Router?

Attenuation, SNR, Sync etc.

In my opinion, it seems like congestion, as in the mornings (out of peak), the speeds seem near enough to normal.

Other people on her may have a near enough idea! 

[jid]

P.s, from Edinburgh1's BT forum thread:-

DSL Connection

Link Information

Uptime: 3 days, 8:28:49

Modulation: G.992.1 annex A

Bandwidth (Up/Down) kbps/kbps: 448 / 6,144

Data Transferred (Sent/Received) MB/GB: 122.16 / 1.73

Output Power (Up/Down) dBm: 12.0 / 7.5

Line Attenuation (Up/Down) dB: 6.0 / 14.0

SN Margin (Up/Down) dB: 26.0 / 12.5

Vendor ID (Local/Remote): TMMB / TSTC

Loss of Framing (Local/Remote): 0 / 0

Loss of Signal (Local/Remote): 1 / 0

Loss of Power (Local/Remote): 0 / 0

Loss of Link (Remote): 0

Error Seconds (Local/Remote): 1 / 0

FEC Errors (Up/Down): 0 / 135

CRC Errors (Up/Down): 0 / 0

HEC Errors (Up/Down): 0 / 0

Line Profile: Interleaved

[kitz]

Thanks for the stats jid.

Hi and welcome Edinburgh2

Firstly I would expect a 14dB line to sync at the full 8Mb - or at least 7616 kbps if the line is interleaved.
Secondly the output power (received 7.5dB) is much lower than I would expect it to be, which could probably be why youre not syncing at the higher speeds.

Granted you from your stats you appear to be on a shortish line.. but why youre not getting a bit more power Ive no idea.
For eg Im on a very short line (was 7dB) and even when on only 2Mb my reciever power was more than that.. (shorter lines + lower speed need less power).. but even on when maxdsl my rec'd) output power was still around 17dB.
20dB is around the figure I would expect to see if you were connecting at your lines full capability, therefore your routers not even trying or being pushed to its full capability.

Even though rec'd output is from the dslam.. Have you another router that you can try.

Aside from the lower sync/low output things look fine and the line itself looks to be relatively stable.
An IPprofile of 5000 + 500 Qos is about right for a line syncing in the region of 6240 - 6784 kbps.

However that shouldnt account for low throughput.
Can do do a speedtest at this site please http://www.speedtest.bbmax.co.uk/ and paste the results please

[Edinburgh2]

Speedtest results (from the link you gave) at 22h30 tonight:
Download Speed: 929 kbps (116.1 KB/sec )   Upload Speed: 76 kbps (9.5 KB/sec )

I noticed that the download was very erratic during the test.  I use WinBar and I can see the traffic speed, fluctuating from near zero to 400 kByte/s (i.e. about 3.2Mbps peak). But the average over the test was 929 kbps.

My hub restarted again tonight after BT did another line test.  So it has only been up for three hours.  But the stats are pasted below.  BT's speedtester site confirms my IP profile as 5500 kbps.
 
Uptime: 0 days, 3:10:53
Modulation: G.992.1 annex A
Bandwidth (Up/Down) [kbps/kbps]: 448 / 6,656
Data Transferred (Sent/Received) [MB/MB]: 12.73 / 155.61
Output Power (Up/Down) [dBm]: 12.0 / 7.5
Line Attenuation (Up/Down) [dB]: 6.0 / 14.0
SN Margin (Up/Down) [dB]: 25.0 / 10.0
Vendor ID (Local/Remote): TMMB / TSTC
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 7 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 7 / 0
FEC Errors (Up/Down): 0 / 0
CRC Errors (Up/Down): 0 / 8
HEC Errors (Up/Down): 0 / 7
Line Profile: Fast

[kitz]

OK I'm going to stick my neck on the line with this one..  but my instincts are telling me that theres a fault with the line card you are connected to on the DSLAM at the exchange.

To make sure though you would first need to test another router, just to make sure its not the home hub thats misreporting. 
However if it is the line card and youre not getting enough power then its possible that it could well be doing some weird and wonderful things with your data transmission which is making it slower than what it should be.

That output power is definitely wrong and is way too low... I have NEVER seen such a low power output. The problem is going to be convincing the BTBroadband Indian Help Desk what your problem is, and you may well have to push to speak to 2nd or 3rd line support in order to get an adsl Openreach engineer to look at the line. properly.

Under normal circumstances I would expect a line that was syncing at under 8128/7616 to have power output in the region of the high 19dB (eg 19.8dB).  On top of that a 14dB attenuation line should sync at either 7616/8128.  If you can get through to someone at BT Broadband who knows how to read line stats properly, they should also be able to see that something is blatently wrong with the output power.

To make sure that you dont get landed with a £150 Openreach bill also make sure that you have done all the usual stuff like ensuring you are connected from the test socket behind the master socket and have tried a different router and filters.

PS
I just noticed you are now on FAST mode...  earlier you were on interleaved??

[Edinburgh2]

Many thanks Kitz.

Just as a check, I tested the BT Vision VOD at 05.30 this morning.  It works fine.  And the speedtest from the bbmax site gives:
Download Speed: 5316 kbps (664.5 KB/sec )   Upload Speed: 365 kbps (45.6 KB/sec )

So the problem clearly does vary with the time of day.

I am intrigued by your diagnosis, and very grateful for your time.  Can you enlighten me a little bit more on the technology and the reported 7.5 dBm downstream output power.  Of what is that the power?  And do you think my line attenuation is unusually low?  If so, would you not expect that to require only a low power?  And how can that make the throughput (or contention) vary with the time of day?

I will indeed quote your diagnosis to the help desk when I call this evening.  But I share your scepticism that they will understand what I am talking about.

Many thanks indeed for your interest and support.  I will take your advice and connect my old Netgear router over the weekend and capture the stats from that.

(And changing the line from Interleaved to Fast is one of the many things that BT have tried in response to my calls.  But it has made no difference.)

[kitz]

You appear to have 2 problems and they are possibly related

1)

The received (downstream) output power is the amount of power transmitted from the DSLAM.
As you rightly say, the closer you are to the exchange then the less power required to transmit the adsl signal.  However, not that low.

>>  And do you think my line attenuation is unusually low?

No its fine - Attenuation is in relation to the length of your line, and the lower the figure the better. A line attenuation of 14dB at a rough guess equates to approximately 1km from the exchange line length (obviously line length will always be more than direct distance) - See here

A 14dB attenuation line is very good and as you can see from the calculator shows that your line is capable of high speeds and it should sync at the full 8128.
So why isn't it?

Back to the power...  the dslam is supposed to adjust the power output strength so that its strong enough to transmit the signal.. but not too much power so that it causes crosstalk on the line (NExT and FExT).

If a line is running at its full strength and using all the available frequencies (maximum speed) then the output power is normally in the region of just under 20dB.  If a line can achieve the maximum sync of the adsl limitation, but is capable of more, it doesnt need as much power and then the dslam reduces the output power so that the signal doesnt drown out neighbouring lines and increase the risk of crosstalk.

Your line is NOT attaining the max sync of 8128... nor is it showing lots of spare SNR.. therefore the power output for some reason is too low and the dslam should have automatically adjusted the signal strength - but it hasnt... and its way too low.


-------------------------

For example I'm on a 7dB line (which is approx half the length of yours and I can look out of the window and see my exchange) yet these are my stats when I was on fixed 2Mb

                Down            Up
SNR (dB):       30.5            27.0
Attn(dB):       7.0             7.0
Pwr(dBm):       15.0            11.9
Max(Kbps):      10624           1144
Rate (Kbps):    2272            288

When I went to maxdsl dsl my sync was 8128 and my power 17dB. 
When I went to adsl2+ my sync was 24574 and output power 18.5dB

See how even on a very short line I needed more power to be able to sync at the higher speeds.

Obviously different routers will show slightly different figures as they allocate the frequency bins slightly differently..  but if you get the point that output power increases the higher frequencies (which give the higher speed) that you use.

Hope this helpfs to clarify whats going on with the power situation. 
I dont know if its a problem with the home hub mis reporting or with the dslam...  however due to the fact that you cant sync at the speed you should be..  to me it appears that it is the transmit power that is being set too low.

[kitz]

2)

The other problem (slow throughput) is typical symptoms congestion/contention.  Either at the exchange or the ISP.  Contention occurs when everyone is using their line all at once and everyones speed starts to slow down during peak times.

However, the amount of your slow down is far slower than what I would expect to see for contention, and something just "doesnt seem quite right".

Now I'm speculating here, because I'm not sure of how it would work..  or even if Im correct because Im not an expert in crosstalk...   BUT... if your output power is too low, then come peak time when loads of other people are using their connections... then your signal is going to be weaker than theirs.. and my theory is that your line would be experiencing a higher amount of crosstalk than it possibly should.  This could well cause slower throughput.  NExT normally occurs close to the linecard at the exchange.

[Edinburgh2]

Many thanks indeed Kitz.  Your diagnosis is the first I have heard that matches all my symptoms.  That makes a lot of sense to me.  However, I notice that I am not alone in having low throughput with a high sync speed.  This chap also has this problem:
http://www.beta.bt.com/bta/forums/thread.jspa?threadID=5915&tstart=30
 and he has a downstream power of 19.5 dBm.

I tried my old router, which is a Netgear DG814.  It synchronised at 6368kbps and the speedtest results were very similar to those I get from the BT Home Hub.  Unfortunately, I cannot get the line stats from that router to show me what the downstream power is.  (Your own website here confirmed that about the DG814, after I had tried for some time to find the stats.)

I will go into bat with BT this week about the low power and see where I get to.

Many thanks again for your very helpful explanation and suggestions.

[kitz]

>> notice that I am not alone in having low throughput with a high sync speed.

Having just had a look at the thread, his symptoms arent the same as yours, and he's syncing at the full 8Mb as would be expected for a 31dB attenuation line and the power output on his stats is correct for the line length and sync speed.

Your line is less than half the length of his, and your sync speed is much lower.

Funny enough I recall reading something somewhere else over the past few days about the poplar exchange which hes on and it appears to be having congestion problems. 
Ive just checked on the usertools site and although the VP is currently showing as green, its been swinging in and out of red for a while now.  Ive also just checked on the BTw database and there are capacity problems at Poplar which appears to have been running out of "Frame space" since late last year and is now blocked

[Edinburgh2]

I am pleased to report that BT has now solved the problem for me.  It required an e-mail to the CEO but then, within 48 hours, I received extremely attentive and helpful attention and the problem was resolved.  I was told that mine was an unusual (but not unique) problem. 

The downstream output power (7.5dBm) was a red herring.  That is unchanged, but the broadband speed and BT Vision VOD are now fine.  It is possible the power is still not right, but it was not the root cause of my problem.

I had a "misaligned virtual path profile".  This virtual path profile is not visible to the first line support people so they would never have been able to diagnose this.  Apparently the 'virtual path profile' should be set automatically by software to match my IP profile but that had not happened on my line.

BT's 'executive complaints team' has been excellent and I am very impressed with their manner, technical competence and personal attention.  But I have told them it is a great pity that the first line service does not have a process that escalates long-term problems to this team itself, without requiring the customer to contact the Chief Executive.

I hope my experiences here may help some others who have similar symptoms.

[roseway]

That's good news, and thanks for letting us know. Your comment about escalation is spot on.

[orainsear]

You could almost end up in an infinite loop with the first tier support with no apparent means to break out of it.  It will be interesting to see if they take on your feedback and make any adjustments to their processes, particularly for slightly unusual situations such as you have experienced.

It certainly is very useful to know that an 'executive complaints team' exists though.

[kitz]

Thanks for getting back to us and letting us know.
Glad that you have got it sorted.

Out of interest what are your line stats now?