Very slow upstream

BT business broadband, dedicated line - the router is the only device attached

I have tried 2 different routers both with the same result - slow upstream sync

Type Fastpath

Downstream is 6652, attenuation 35db, output power 123, Noise Margin 10

Upstream is 183 attenuation 44db, output power 183, Noise Margin 5

Exchange: http://www.samknows.com/broadband/exchange/WWBRIX

Any ideas?

TIA

Can you tell which ADSL Mode you are on, G.DMT, ADSL2, ADSL2+?

V. slow downstream too, if ADSL2+. Should get 11-12 Meg.

Those figures are all over the place. Please could we have a screen shot of the actual data, as with some routers it is easy to misread what they say. (You have to upload it somewhere and give us a link).

What does the Quiet line test (dial 17070 option 2) give? Is it silent or do you get crackles or hisses? Preferably use a corded phone, not a cordless one.

Which socket are you using, and are you using a plug-in phone extension to reach the router. What are the stats like with the router >> short ADSL cable >> filter >> test socket? (The one on the wall at the back in this pic).

As you are a BT Business customer you may have a 2 wire 2700. If you do, then you can access the Bit Loading graphs which will show which Bins are used and to what density. It will then show which are not being used which might suggest low frequency noise on the line.

Can you access the 2700 and grab a screen shot?

Second thought on it.

When you say ONLY device attached, does that mean no phones and no filter/splitter.

I have seen something similar - about 10 years back where the a phone was plugged in to the filter and all was fine, but unplug the phone and upstream almost disappeared. If a filter is faulty and offers a low impedance path to the ADSL frequencies then it will look like significantly additional attenuation adding an extra 10, 20, 30 dB to the loss.

So, if you have a filter can you remove that from the connection and plug straight into the test socket behind the master.

Thanks a lot for all the replies

I am doing this this to help out a friend and will be going to the site again next Monday

Here is a screenshot - I don't know what happened to the 2701!

Belkin N+

The problem is almost certainly with the attenuation level ... with a downstream of 34dB, I would expect the upstream to be somewhere around 15 to 20 dB. Whether that is a faulty filter, wiring or the main BT pair it is difficult to say, But if it was the BT pair or wiring, I would expect to see downstream affected as well. It could be a faulty filter or linecard at the exchange too.


Just another comment; Belkin are wrong with the power levels: those figures on the screen shot are cB - centiBels and to convert to dB just divide by 10 which would give 12.3 and 18.3 - it does not matter at those levels but if the power was down at say 1.2 dBm and the Belkin reported that as 12 then there would be total confusion as 12 is a realistic number.

123dBm is 2 GW yes Giga Watts !

Thanks. You got the figures right, but as MHC says, the attenuations are very strange indeed. That's why I wanted confirmation.

The downstream sync is low as well, and I doubt if that is fully accounted for by the 10dB (high) noise margin. You should be on a solid 8Mbps, (or 7616kbps), with paradoxically an even higher noise margin. Explanations of different aspects of noise margin here and here.

Yesterday I saw a new "record" of noise swing! It was an office above a factory and the night processes and equipment was different to day time. The 2700 would resync in the early hours at 3dB but during the day that would increase to 12dB and on one day 14dB.

Solving the OPs upstream will be the start then tweaking to improve downstream and if he can find the 2700 it would be very useful as it hold historic sync data - speeds, atten, SNR

Edited by MHC (Fri 02-Nov-12 14:14:00)

Post deleted by RobertoS

An update (I went to site today)

From the master socket (phone socket only) the cable went: ADSL filter - RJ11 - RJ11 Router

I replaced that with a cable that went direct from the router RJ11 to Phone socket

The wire at the back of the master socket is a drop cable which exits through the wall, goes up the side of the building and onto a wire support

I also tried the router directly into the test socket (since there was one unused internal extension)

Results now are

Downstream Sync 6652 Noise margin 8 Attenuation 31
Upstream Sync 259 Noise margin 6 Attenuation 41

A massive improvement, but still not enough!

Upstream attenuation is still high - but if you were direct into the socket there is very little you could do.

Next time, try plugging in and unplugging a few times to remove any corrosion that may have built up. Also, are you able to see which colour wires are connected to the face plate? And are they good connections - tightly screwed down?

The next hurdle will be persuading BT that there is a potential fault - somewhere on their network. Have proof you have tried 2 routers and with no phones or filters attached and then hope you get an agent who really understands.

In reply to a post by MHC:

Next time, try plugging in and unplugging a few times to remove any corrosion that may have built up.

I suggest that is done using just the cable, or if the router is on the other end of it then with that powered off.

Good point ...

Another update!

Have now examined the wiring. There are a lot of cables inside the external black drop cable connected to the socket - the orange and the white are connected

Master socket wiring

Then there is a white cable which runs to an extension

Nothing obvious - the dropwire is four pair with Or/Wh, R/Gy, Bl/Bn, Gn/Bk so you have a pair allocated. the extension looks as though it uses Bl & Bl/W on 2 & 5 with Or/Wh on 3 for the ringer. Technically those are wrong but it does not matter.

Did you carry out the tests with the small lower front face plate removed and into the socket on the remain back back of the socket - that removes the extension wiring completely.

There's a ring wire (isnt there).

Is the extension filtered? Is it used? If not disconnect it!

Yes I carried out the tests with the faceplate removed and into the test socket (hence not too worried about the extension wiring)

The extension will be used in the near future

Seeing the stats from the second router would help to confirm that is not an oddity of the Belkin in the displaying of the attenuation figure.

The upstream may stay slow if there is some bandwidth banding going on possibly.

Would this help?

I could configure my Billion 7800N and leave it running at the site for a couple of hours. The advantage would be that it works with Routerstats and gives a lot more info including Bits, tone and SNR graphs

Yes it certainly would - configure RSL to give the UPSTREAM SNR and Attenuation on a single graph. When you host the image and provide a link, can you also add the full stats for the router.

Even just a single snapshot view of the attenuation and noise margin and connection speed data would help.

On site again today

I plugged in a D834GT and rang the BT business helpdesk

They tested the line got me to a speedtest (expected 5-6MB)and would not entertain ANY notion that the 0.2 upload was slow

Confirmed it is an ADSL2+ line and Samknows suggests 16Mb download ??

Pics:

Speedtest

Detailed telnet stats

Bits tone first

Bits tone second

The bin plot suggests something is wrong, but not seen an issue like this often enough for my brain to recall a reason why.

The plot confirms that the downstream attenuation looks sensible, as still seeing bits used in the high frequency bins, it is the bits for the upstream that look wrong.

http://www.thinkbroadband.com/images/reviews/fritzbo... shows a longer line with the attenuation causing higher frequencies to fade away. Notice how the green upstream is a tidy shape, rather than sawtooth you have.

The 42dB attenuation for upstream also points to there being a low frequency issue. Given unlimited resources it would be send someone to the street cabinet and test the line from there.

Alas BT Retail and BT Wholesale tend to take the view that almost any connection is a good connection. Rather than the unquisitive try to understand why your line is different to the norm.

17 errored seconds in 15 minutes isn't great.

Is there anywhere that confirms it's ADSL2+ on the router lke G992.5 etc, not familiar with the bit plots (though look like a few bits per bin over many tones - rate capped perhaps ?)

I would be asking for a lift and shift in case it's the line card. As it's a Market 3 exchange you have LLU as the ultimate sanction to threaten, or a more motivated ISP.

26dB downstream attenuation and only 6Mb ... and 42dB upstream.

Are you 100% certain that those have not been transposed by the router or software. Do you have a BT 2700/2701 to try - the stats on those are certainly the right way round.

If the attenuations are correct 26dB would normally give a lot better than 6Mb and 42 dB upstream is way higher than I would expect to see - somewhere from 12 to 18 dB upstream would be more in keeping. So it points to a fault somewhere.

Also, upstream SNR is 5.7 dB and that will be the reason the upstream sync is only 320k and 0.2Mb which could be 250kb ties in so BT are "correct"


You need to find out what is causing the upstream attenuation ... Have you tested the connection without filters and no phones connected?

On the first page had a Belkin N+ plugged and that reported similar attentuations

No phone

an yes have already tried just the master socket

In reply to a post by MHC:

26dB downstream attenuation and only 6Mb ... and 42dB upstream.

Are you 100% certain that those have not been transposed by the router or software.

If the attenuations are correct 26dB would normally give a lot better than 6Mb and 42 dB upstream is way higher than I would expect to see - somewhere from 12 to 18 dB upstream would be more in keeping. So it points to a fault somewhere.

Also, upstream SNR is 5.7 dB and that will be the reason the upstream sync is only 320k and 0.2Mb which could be 250kb ties in so BT are "correct"


You need to find out what is causing the upstream attenuation ... Have you tested the connection without filters and no phones connected?

So, assuming the attenuation figures are correct.

Downstream is lower than expected for the attenuation but the 7.4 dB SNR indicates it is about right for the line. It points to the line being very noisy. Is it in an industrial environment? Close to factories &c?

The Upstream attenuation is well above what should be expected with 30dB of excess attenuation and that suggests almost a short circuit or very low impedance path at some point. That is what you have got to find - or get BT to find for you. Provided you have tested everything cleanly (no filters, phones, excess cable, extension wiring) then it has to be outside your facility. Unfortunately getting this across to a BT Technician* or Tech Support agent will be very difficult.


Looking at both points together does suggest that the noise cause the low downstream is being picked up close to you and not the exchange.


* One reason why I differentiate between Technicians (or engineering Technicians) and Engineers.

Thanks for all the pointers

Environment is a garage in an otherwise residential area

Both routers used on site have been tested at my home and give the normally expected upstream

I have now got they're account managers details and am formulating an email - watch this space!

By Garage do you mean a petrol station and car repair type facility?

If so, there is likely to be a lot of RFI (noise) floating around from petrol pumps, control links and other equipment. Is there a time when everything is off and you could try again to see if the Downstream SNR changes or it resyncs higher.

You will still need to look at the Upstream attenuation.

Have you followed the wires all the way back from the master to the incoming location to make sure there is not a device hanging off it somewhere - a modem or alarm?

Car repairs only

Have worked on it after hours - no difference

There is an external drop wire which goes direct to the master socket

There is wiring for one unused extension from the master

External

Internal

In reply to a post by MHC:

By Garage do you mean a petrol station and car repair type facility?

If so, there is likely to be a lot of RFI (noise) floating around from petrol pumps, control links and other equipment. Is there a time when everything is off and you could try again to see if the Downstream SNR changes or it resyncs higher.

You will still need to look at the Upstream attenuation.

Have you followed the wires all the way back from the master to the incoming location to make sure there is not a device hanging off it somewhere - a modem or alarm?

The internal picture looks like mains cable to me and a power socket.

As Andrew has said that pic does make it look like the mains socket is very close to the master but in the same breath it would seem there is a wall in front of the master socket so how was it put there, the pic makes it look like you would struggle to get a screwdriver in front of it giving me the idea that the setup is not so great.

Any reason why the drop wire is capped outside the masker socket?

Can you physically disconnect the unused extension wiring?

As Mr S has said - a little close to the mains wiring - can you get a picture from further back and also one of the inside of the master.

Not sure what you mean by capped ?

Pic showing layout internally

Inside master socket

WRT to disconnecting the extension wiring I thought plugging in to the test socket had the same effect ?

You are not meant to take it apart that far, just the half plate on the front, and a picture of the wiring on the back of that are needed

At the back of the socket the incoming dropwire has a black cap over the end with the internal conductors protruding. The cap is normally there to help with weather proofing. I would expect the drop wire to go inside the master ...

I can see a pair Or & Wh has been used.

As for the extension, I wanted to be 100% sure it was but if, as your picture shows it is on the faceplate then it will be disconnected. Unfortunately some people will wire the extension to the A&B terminals.

I am starting to run out of ideas ...

Is that a consumer unit just to the right? Can you kill everything except the one socket used for the router/hub?

Back on site again today

No possibility of power off (maybe another time)

Some further info: site is 181M from exchange (as crow flies) and the estimators say about 16MB down

BT insisted I go back to site "for further testing" then did nothing (apart from a line test)

"Line looks perfect"

"5-6MB down is normal and expected"

"40-50db attenuation upstream is normal"

they then closed the call

I see two plug in power supplies in the mains socket - one for the router presumably, can you turn the other one off in case it's an RFI problem then restart the router and recheck upstream speed.

I'm inclined to think it's the exchange end personally. Have you used the line test facility at bt.com or had your ISP run diagnostics on it ? wire issues on the line should be picked up by the copper test.

Please can I ask for the correct capitalisation. It can remove a lot of confusion at times.

b - bit; B - Byte; m - milli; M - Mega.

so the line speed will be given as 6Mbps (6Mb - albeit incorrect still has the right M)

And attenuation/SNR are in dB (deciBel)


5-6Mb may be reasonable for teh line speed with the noise, if you cannot sort it.

But 40-50dB of upstream attenuation is not normal. Upstream should be lower than downstream and typically half the number plus or minus a few is a good start. So a 30dB down would have 12 to 18 dB upstream. 40dB downstream would have 16 to 24dB upstream ...

The two plugs are both for routers when I used a D834GT for testing - the other Belkin was switched off

I started out by using the online fault report - it started testing then automatically generated a call reference. BT have run diag several times

Sorry about the nomenclature (I cannot edit the post now)

I am amazed at how little troubleshooting (none!) BT have asked

I get used to people using b/B in the wrong places and some times it is possible to guess and other times not. effectively b * 8 = B so you can see what a difference it would make.

Right just to put the distance into context

Site to exchange 200m

The downstream attenuation of around 30dB suggests a line length of about 2Km

You are right about the attenuation and approx length - at worst the line could go a little round the houses and be maybe 800m long or possibly 1km which would still give an attenuation in the low 20s.

You will not get much joy pushing on the downstream attenuation front but need to focus on the upstream which should be lower that downstream. If you can get that sorted, gut feel says that any problem on downstream will also be resolved.

Have you managed to speak with a Coach or Manager on Tech support? If not insist on it and then use that as the escalation path.


Do you know which call centre you are dealing with?

Have you tried asking for/insisting on a BT Business Broadband Boost task to be raised ? Get and engineer out, and show them the issue. If the lines as short as you reckon, they will see that something is wrong.. I'd agree it sounds like an exchange equipment fault.

The number I rang was 0845 600 70 20

Have not escalated.

They have point blank refused to send an engineer so far and will not entertain any discussion about the upstream apart from admitting it's slow. There is no SLA at all with regard to the upstream.

I am going back to the account manager with a very long email

You seem to have an impasse ... somehow you have to break through the wall. Zarjaz's comment is one worth pursuing - I think he knows what he is on about!

Heard nothing since 10th December having been promised a call I sent an Email to Mr Livingston today

Received a reply within 2 minutes - escalated to High level complaints team

Several calls today:

They have identified a Network fault
The line is capped
Engineer on site next Tuesday

Engineer pitched up at 10am - was not able to make it on site

He fixed a cable fault at the top of the pole

Downstream attenuation 10dB, sync 18617

Upstream attenuation 5.7dB , sync 1252


Months of misery and frustration are over with no thanks to the BT Business Helpdesk