Does anyone understand how ADSL broadband actually works?

[ProDave]

Related of course to an ongoing fault that we have.

 

We are 3 miles as the crow flies from the exchange, no doubt further by the route that a collection of tatty thin bits of twisted copper wire wind their way from the exchange to our house.  But when it is working properly it delivers our ADSL broadband at a speed of 3MBPS.  although slow it is is usually dependable, usually works, and can even stream tv over the internet.

 

But for 2 weeks now it has been acting up.  Instead of being the reliable dependable connection the speed has been all over the place, often dropping out completely (the logs show it was dropping out 9 times per day roughly)

 

So the fault has been reported to BT and so far we have had 2 Open Reach visits, both declare the connection from our house to the exchange "good" and leave saying it is "an equipment fault"  but 2 weeks on, the fault is still open and not fixed.  so I am trying to understand how this actually works.

 

The symptoms are quite simple, you can run a speed test (I have become familliar with several different ones over the last couple of weeks) and you can get anything from just over 3MBPS to 0.  For most of the last 2 weeks it has mostly been hovering just under 1MBPS,  Oddly quite often when testing it reports the upload speed as 0 even if the download is working.

 

The router reports it is synced at a line speed of 3.769 MBPS.  Now in simple terms I see that as a constant "carrier" over which data can be sent up to somewhere close to that bit rate.  So how, if that connection remains there, can the actual speed drop so low so often?

 

Any insights into how it actually works and in particular how it connects at the exchange?

 

The fact the fault is still open after nearly 2 weeks suggests BT don't know much more than me about how to fix it?

[ToughButterCup]

27 minutes ago, ProDave said:

...

but 2 weeks on, the fault is still open and not fixed.  so I am trying to understand how this actually works.

...

 

Dave, I think you are trying too hard. The job's getting them to take the fault seriously..... We had a similar issue - several vans and several blokes later; deadlock. Cue some fairly straight talking -  followed by another van and another - new - OR guy.

 

Twenty minutes later he'd found the problem , half a day later all sorted. 

The 'fault' ? The signal by-passed our house, went half a mile down the road and came back to us - often as not scrambled.

[ProDave]

You are right about getting the fault taken seriously.

 

When the line was first connected about 5 years ago, we had a very poor speed, less than 1MBPS but at least it was consistent. I knew we should get better and on that occasion on the second OR visit the guy checked all the connections in the street and found 2 adjacent connection pits full of water with corroded connections sitting under water.  He re made those connections and got us up to just over 3MBPS.  

 

So first OR visit this time I encouraged him to go and look, and he found the same thing, full of water, and connections under water.  He did not mention if he actually re made the connections or not but he did bale out the water.

 

Second OR engineer was having none of that, "the line tests fine" so would not even investigate further.

[SarahG]

Definitely just need to keep on at them. From my experience working in a NOC quite a few years ago now intermittent faults like these were often fixed by either replacing or resetting the line card in the local exchange.

[Pocster]

@ProDave you need to use the magic word …. “ compensation “ .

Our ‘install’ was due October 2021 . Now scheduled for July 2022 😂

I get £5.20 per day 🤣

You are probably being too nice I suspect to BT . Man who shouts loudest gets sorted first . Sometimes you’ve just got to kick up a storm .

[JohnMo]

We had a similar issue at or old house, speed all over the place.  Took them lots of visits to identify the issue.

 

We call them they would test while I was in the phone and mostly they would identify an issue.  Send engineer out, he would find nothing.

 

Issue was finally found as a broken wire on a pole down the road.

 

[Bitpipe]

22 minutes ago, JohnMo said:

We had a similar issue at or old house, speed all over the place.  Took them lots of visits to identify the issue.

 

We call them they would test while I was in the phone and mostly they would identify an issue.  Send engineer out, he would find nothing.

 

Issue was finally found as a broken wire on a pole down the road.

 

 

Exactly the same issue we had - broken wire in the pair at the pole where it joined the run to the house. However was not a clean break so the connection on that wire would come and go so the fault was intermittent. 

 

You just need to keep pestering BT who will keep pestering OR and eventually it will get sorted. Maybe ask them for an EE router (if your EE signal is any good).

 

On a related note... we have two circuits in the house, so two master sockets. One was voice only and the other voice and business broadband. Neither were on BT but both had started out as BT contracts.

 

Anyway, we decided to consolidate them so in Jan this year we ported the voice only line back to BT and added broadband plus the WiFi discs, EE back up router etc.

 

On activation day, could not get it to work so logged a fault. Engineer came out and realised that the voice only master socket had the wrong face plate so he swapped it over and job done.

 

This month my BT bill has a £245 engineer charge! I get into a chat support call and, after checking engineer notes and the voice recording of my original call, they say it was because the problem was at the master socket it counts as my responsibility and I'd agreed to the fee if the fault was found on my part of the network.

 

I pushed backed hard and they were not budging until after two more go arounds, they acknowledged that the line had never carried data since install so it was an install fault. Got the fee removed but how many people would have had the technical knowledge to put up the fight?

 

 

[ProDave]

14 minutes ago, Bitpipe said:

Exactly the same issue we had - broken wire in the pair at the pole where it joined the run to the house. However was not a clean break so the connection on that wire would come and go so the fault was intermittent. 

 

You just need to keep pestering BT who will keep pestering OR and eventually it will get sorted. Maybe ask them for an EE router (if your EE signal is any good).

Yes that is my belief.  A dodgy connection in that underwater connection pit.  but an intermittent connection, and annoyingly, on the 2 occasions so far an OR engineer has visited, it has been working fine, and half an hour after they have gone, it is back to rubbish.  Now I have found the BY wholesale speed tester has the ability to download and save a log of a test result, I have a load of saved rubbish test results.

 

Right at the start when we had the poor connection when the line was new, BT sent me an EE 4G router (and we know we get a good EE signal here) I could not get it to work.  Each time you complained about that, it was a multi day turn around while they adjusted something before you could report a failure again, the hard wired line was fixed before we got the 4G router ever working.

[ProDave]

Well I just received a message from BT telling me the fault has been resolved.  A quick speed test shows that it most certainly has not been fixed.

 

So i have now raised it as a "complaint" that that fault has not been fixed in spite of what they think.

[MikeSharp01]

In answer to you original question - Yes, and this is about the best explanation, I found way back when, as helps you in gently.

[Temp]

It doesnt really help to know how ADSL works but...

 

ADSL assumes a phone line has a bandwidth of about 1Mz. It divides that up into a bunch of 4khz wide channels. I think 196 channels are used for download and 64 for upload. I think a few are unused/guards between voice and data. It's a bit like having a whole bunch of individual modems in parallel. The data rate for each channel depends on the signal to noise ratio for that channel. Or in short.. a noisy line is slower. 

 

Most ADSL modems have the ability to tell you what the noise margin on the line is like. Typically you have to log in to the Admin page in the modem and drill down to a status page. I've long since forgotten what acceptable noise values are so I had to Google this..

 

https://help.keenetic.com/hc/en-us/articles/360002830880-ADSL-line-parameters

 

Quote

 

 Noise margin (also known as Signal-to-noise ratio margin, SNR) — is used to measure line quality and defines a minimum limit at which the signal level is above the noise level. The limit value of noise resistance for data transmission is 6 dB, a value below which the ADSL connection is not guaranteed at all. If the noise resistance is lower than 6 dB, the communication may be interrupted frequently.

 

If the noise resistance is higher than 10 dB, the line has good parameters for data transmission. The higher the value, the better the line quality. The 'Noise margin' value should be 6 dB and higher. It can reach values up to 30 dB if a short wire is used.

 

The field 'Noise margin' displays two values - the first number for the direction to the subscriber (downstream), and the second number for the direction from the subscriber (upstream).

 

'Noise margin' parameter value [dB]:

up to 6 dB is a bad line, and there are synchronization problems;

7 dB to 10 dB failures are possible;

11 dB to 20 dB is a good line, no problems with synchronization;

21 dB to 28 dB is a very good line;

29 dB and above is a perfect line

 

 

Sometimes the noise margin varies with time of day.

 

One tip I was told... Apparently OR are better at dealing with complaints about noise/crackling on calls than they are about complaints of slow ADSL. However fixing noise/crackling on the phone line can sometimes fix ADSL issues as well. So one thing you can try is doing the Quiet Line test which suppresses the dial tone so you can listen to what should be a quiet line. If its crackling away then complain about that first. Once that's sorted then see if ADSL improves.

 

 

[SteamyTea]

7 hours ago, Temp said:

Quiet Line test

17070

Option 2

[joe90]

The problem is that the old voice network was never designed for data, I worked on the original roll out of ADSL, being rural like me can be a real issue with lots of cable joints and cables not in straight lines to the exchange. Fibre is the only way forward but unlikely in the near future fir remote users. Yes, complain like mad and become a pain in the ass!!

[joth]

The problem is 30 years ago the government decided to sell off BT so they could profit from it, rather than invest in making it ready for a digital future

https://www.techradar.com/uk/news/world-of-tech/how-the-uk-lost-the-broadband-race-in-1990-1224784

[Bitpipe]

We currently have a City Fibre rollout ongoing - they have been in town for over a year, every side of every residential street has (or is in the process of) being dug, ducted and covered and then fibre pulled through. The crews work super fast, they can be here and gone off to the next street in a matter of hours.

 

They seem to be using the same distribution as OR, poles where overhead wire is used and up to the house boundary where OR is ducted. I'll need to catch them in the act as we have a one off duct from the pole opposite, every other house has overhead.

 

Nice to see a bit of competition to OR and VM though, no idea what the service pricing is like but my BT contract will be up in 18 months so I'll be checking it out for sure.

[SteamyTea]

12 minutes ago, Bitpipe said:

We currently have a City Fibre rollout ongoing - they have been in town for over a year, every side of every residential street has (or is in the process of) being dug, ducted and covered and then fibre pulled through. The crews work super fast, they can be here and gone off to the next street in a matter of hours.

Didn't NTL do exactly the same, but with wires.

There was a company that ran new data cables in Aylesbury in the 1990's.  Then went bust.  I assume the dark wires/fibre is still there.

[Bitpipe]

7 minutes ago, SteamyTea said:

Didn't NTL do exactly the same, but with wires.

There was a company that ran new data cables in Aylesbury in the 1990's.  Then went bust.  I assume the dark wires/fibre is still there.

 

From memory most of the new cabling back in 80's and 90's was CATV, most of which is now Virgin Media.

 

Quality of that street work was quite shoddy, especially in areas that had traditional paving slabs vs the more common tarmac paths today. Killed a lot of trees also by digging through their root systems.

 

The guys on the street today are surgical by comparison - dual disc cutter to make the 6" wide slot, narrow excavator to get depth, grab loader to remove spoil duct laid and a finishing crew behind  - all moving in convoy.

[SteamyTea]

10 minutes ago, Bitpipe said:

most of which is now Virgin Media

So that is really where RB lost my pension, not on 'the turmoil of 9/11'.

Bastard still, in my eyes, owes me £70k, plus 20 odd years of growth.

Edited May 17, 2022 by SteamyTea

[gc100]

Do what @Temp said - this will be the best way to prove the issue as this is your issue - loosing network packets due to bad line 

[Post and beam]

In case it is still of interest. The other thing to consider is that xDSL (aDSL) is a shared service. You will share a common link back to the telephone exchange with a number of your neighbours. This might be 2 and it might be many more. How many have been added and how many people are online right now is out of your control or knowledge.

The technical issues like crap wires and connections etc are just a part of the potential issues

 

[joth]

45 minutes ago, Post and beam said:

In case it is still of interest. The other thing to consider is that xDSL (aDSL) is a shared service. You will share a common link back to the telephone exchange with a number of your neighbours. This might be 2 and it might be many more. How many have been added and how many people are online right now is out of your control or knowledge.

The technical issues like crap wires and connections etc are just a part of the potential issues

 

Nit: that's not actually true for traditional ADSL (as the DSLAM is generally in what we call the exchange),  but yes it is for any FTTC product like VDSL.

But it's moot as with *any* internet connection if you go far enough upstream there will always be a shared link that may be a bottle neck. That's the whole premise of packet switched networks.

[Adrian Walker]

The best solution is new copper directly from your house to the box.  The problem is that years ago a BT accountant found out that aluminium also conducts electricity so a lot of cables are not copper and this causes lots of problems, particularly joining or terminating cables.  

[joe90]

23 minutes ago, Adrian Walker said:

The best solution is new copper directly from your house to the box.  The problem is that years ago a BT accountant found out that aluminium also conducts electricity so a lot of cables are not copper and this causes lots of problems, particularly joining or terminating cables.  

Not quite true, aluminium started being used when copper became really expensive after a worldwide shortage. When ADSL started to be rolled out I worked for BT and anomalies were noticed and it then became obvious that aluminium cables were causing some problems, also no records were kept where these aluminium cables were used. Because of difficulty jointing aluminium cables, copper tails were used so identifying these cables was difficult. The main problem is that historically the copper network was designed for speech only, yes clever people enabled data to be sent over copper but the length of cables and the numbers of joints in that cable restrict how data can be delivered.

[SteamyTea]

When you think of all the different types of cables used, how they are installed, when they are installed, then add in all the 'devices' connected to them, and the difference in business plans that run all the worlds servers and internet services, it is amazing any of it works at all.

[ProDave]

Since this thread has been woken up, I can report we have made the decision to dump BT and go with the local wireless broadband provider.

 

It is wasn't an easy decision.  In some respects I wish they did not exist.  But the fact they do exist is responsible for BT/OR not making any more investment in the cable network, so if we stick with BT it would appear we will not in the forseeable future get anything better.

 

But on the other hand, the wireless offering will give us broadband at 30mbps.  Now that is 10 times as fast as we get at the moment, but I honestly don't think that fits the category of "super fast" broadband?

 

So it is this or the rubbish (both in terms of performance and customer service) we get from BT.

 

But it is not as simple to switch as you might think.  I still want a "landline" (mobile is too unreliable here to rely on 100%)  There is no way I want to keep any service with BT after the switch, so the "landline" will become a VOIP service by the same provider and they claim they will port our existing landline number.

 

I am now awaiting the paperwork and a connection date before I can finally tell BT where to go.