How do isp increase bandwidth

As above, with cable & wirless adsl2+ asked the isp to increase my bandwidth as not getting what i have been promised but now looked at stats and all they have done is lowered the snr margin from 9db to 6 db but my upload speed has gone down from 1023mb to 0.4mb on router stat can they not increase download speed and also keep upload same....i think they are trying to cheat with me, just by lowering the snr margin with slight increase in download speed....old stat said 6.1 mb d/l 1mb u/l snr margin 9-10db but getting 5.4mb thru speed NOW 6.8mb d/l 0.4u/l 4-6db snr margin getting 5.6- 5.7mb thru speed....why cant they increase my actual bandwidth instead of tweaking the snr margin.

What are the current upstream and downstream attenuations?

Your 6.8Mbps downstream sync would be about right on an ADSL2+ 49dB attenuation with a 6dB SNRM...

Your bandwidth on ADSL is dependent on your distance from the exchange. Might be able to increase if you have FTTC available.

What they have done is a small tweak to use some "spare" SNR. However, the SNR may have been high to give a stable connection so you may have traded some stability for speed. It also sounds like they may have moved you from ADSL2+ to ADSL which is what has dropped the upstream (EDITED to correct error) speed lower.

You need to get them to move you back to ADSL2+ and you are not going to get anymore speed really unless you can change technology (or move your house closer to the exchange).

Can you post full stats (attenuation, speeds, SNR) straight from the router? Then we may be able to comment further.

Edited by ian72 (Sun 18-Aug-13 16:10:10)

In reply to a post by ian72:

It also sounds like they may have moved you from ADSL2+ to ADSL which is what has dropped the down speed lower.

Good point about the possible change from ADSL2+ to ADSL1, but as a consequence did you mean that the upstream sync speed is now lower?

Indeed I did.

Current figures
DSL Type: ITU-T G.992.5
Bandwidth (Up/Down) [kbps/kbps]: 509 / 6.998
Output Power (Up/Down) [dBm]: 12,4 / 18,0
Line Attenuation (Up/Down) [dB]: 24,2 / 42,0
SN Margin (Up/Down) [dB]: 24,3 / 4,3
through speed 5.2-5.5mb ish.

Before figures
DSL Type: ITU-T G.992.5
Bandwidth (Up/Down) [kbps/kbps]: 1.023 / 6.300
Output Power (Up/Down) [dBm]: 12,6 / 18,5
Line Attenuation (Up/Down) [dB]: 23,0 / 40,0
SN Margin (Up/Down) [dB]: 6,7 / 8,8
through speed around 5.4-5.7 ish.

I see the sn margin has changed and download not improved that much.

Edited by deleted (Sun 18-Aug-13 16:10:49)

The upstream speed is still there just for some reason the SNR has shot up - have you tried restarting the modem to see if it clears it. If not the ISP might be able to release whatever is holding the upstream back as there is SNR to spare.

Yes you are still on ADSL2+ but for some reason the upstream SNRM is now 24.3dB which has reduced the upstream sync to 509Kbps.

For example, a 42dB downstream attenuation on a 6dB SNRM with ADSL2+ should give a sync speed in the region of 7200Kbps. So your downstream sync is looking reasonably OK

no not restarted as i have been told not to touch router as they are still trying to resolve my problem had constant dropout after 4-5 hrs so they changed linecard its now stabalised but why instead of tweaking snr margin cant they up my download sync speed to 11mb then tweak snrm....previusly getting 7mb actual download speed with old isp been informed differnt technology WHY they both use adsl2+ i.e 992.5 so whats different....can anyone tell me from my stats if they are trying to cap me from the info.

What makes you think your line can do 11Mb/s? Has it done that speed before? It could just be as good as it is going to get.

originally i had 39db 992.5 annex a from old isp using adsl2+, then got 40db from current supplier then changed router and change linecard now 42db....strange how from 39db now have 42db.

Difficult to say what might have affected attenuation. Could just be the router as different routers can calculate it differently.

It does look like in an ideal world you would get more. Have you been able to run the router from the test socket to rule out any internal cabling issues?

It might just be the cable between you and the exchange is not top notch - and with it running within reasonable parameters BT won't do anything to change it unless you have significant issues. If they found a problem on the line causing your instability then you might get a bonus speed improvement but with the cost of replacing cable BT will only do it as a last resort.

sorry what i meant was if it sync higher i can get what i originally from my old isp i had was around 7mb download speed

Different providers configure their exchange hardware and DLM systems slightly differently

C&W is often not the fastest LLU provider to go with, so asking for 11 Mbps outright is probably not going to help them understand you.

it is a case of now sit and wait for their DLM to be happy with your line, and then gently coax them to do one thing at a time, e.g. sort out the upstream.

Possibly attenuation has increased due to work done on your line and/or you are in a stabilization period. If you were getting 7Mbps throughput previously on ADSL2+ then sync speed would have probably been more than 8000Kbps.

Or your line was performing really well on an ADSL2+ 42db attenuation with a 9dB SNRM to achieve 7Mbps throughput speeds.

Edit: Sorry just noticed that you were on an ADSL2+ 39dB downstream attenuation sometime ago

Edited by 4M2 (Sun 18-Aug-13 16:43:41)

Uptime: 0 days, 0:00:49

DSL Type: G.992.5 annex A

Maximum Bandwidth (Up/Down) [kbps/kbps]: 1,209 / 9,384

Bandwidth (Up/Down) [kbps/kbps]: 1,213 / 7,838

Data Transferred (Sent/Received) [kB/kB]: 0.00 / 0.00

Output Power (Up/Down) [dBm]: 12.0 / 19.0

Line Attenuation (Up/Down) [dB]: 22.5 / 38.5

SN Margin (Up/Down) [dB]: 7.0 / 6.5

my old isp stats

Looks pretty good for the attenuation then. Are you looking to try and squeeze more?

Yep, attenuation has gone from 38.5dB to 42dB so that may account for your reduced sync speed with the same SNRM of 6dB.

to be honest im trying to get what i had with my previous isp i.e 7mb current isp is only offering 5.5-5.7mb which they say its due to different technology. if the only way they want to increase it by tweaking snr then thats not good enough....i still think they are capping people and messing with my line to get attenuation higher.

Edited by deleted (Sun 18-Aug-13 16:56:35)

In reply to a post by candy123:

to be honest im trying to get what i had with my previous isp i.e 7mb current isp is only offering 5.5-5.7mb which they say its due to different technology. if the only way they want to increase it by tweaking snr then thats not good enough....i still think they are capping people and messing with my line to get attenuation higher.

Different technology? Guess there may be some differences between 21CN and LLU though, if relevant in your case. However the older router stats, when you were with a previous ISP, indicate that you were on ADSL2+ then also.

Unlikely that an ISP would mess with your line to get the attenuation higher...

What about the bottom line of the post?

Evening Candy123

The Line Attenuations are basically a natural result of the quality and length of the line; and in general terms, the ISP and BT Openreach have no control over those aspects, other than by, say, replacing the whole line or parts of it, at generally relatively high cost, because it would involve replacing multi-way cables, with possibly 400 customers on the end.

BT Openreach legally is only required to maintain it to a standard suitable for land-line phones, not any other function, unless with a very specific contract.

In part, those attenuations can be affected by the state of the (many) joints in each line, particularly if significant noise can be heard when using a simple, directly connected phone - specifically not any form of cordless phone.

Additionally, the attenuations can vary with the weather, particularly when used for the higher-than-audio frequencies involved in Broadband.

The basic telephone wiring system was only expected to handle from about 40 Hertz to about 4,500 Hertz, a restricted part of the audio-frequency range, which depending on one's hearing ability can range from about 25 Hertz to 20,000 Hertz, BB being even higher.

I am constantly amazed that Broadband signals are bring transmitted through the phone system, in some cases on wiring installed 100 years back. My own line is "only" 46 years old; and I remember in the 1970s, GPO Telephones (BT's predecessor) replacing phone poles and wiring in Birmingham when they were about 110 years old.

All else being equal, the higher the line attenuations, the slower your Broadband will be.

They are not capping you. With them this is the best you can get.

Attenuation is just a measure of line distance. So the ISP will not come out, dig up all of the roads and replace your line with a longer one.

The attenuation can go up when you change routers (some measure it differently). Also when you switch ISP you can connect to equipment in the telephone exchange which is further away. Say your old ISP had 50m of cable in the exchange. Your new one may be 150m of cabling away. So this can change things a little. It's not a case of the ISP capping you, it's a case of this is where the available space was in the exchange when the ISP arrived and this amount of cabling was needed to get there. This generally doesn't affect things much though.

Overall your lines perfect, it's not under performing. You did get a little better on the previous ISP but you are not with them anymore. It's different equipment, different provider (so backhaul can be better or worse) & there's been a time lapse. So it's possible that overtime due to work at the exchange etc that your lines been made slightly longer hence a slower speed.

Taking the previous ISP out of the equation and the previous stats out of this... Based on what we see today there is nothing wrong at all. It's performing as it should, within the estimated speed etc. This is the viewpoint any ISP will take.

Sorry i dont agree with your last paragraph as my minimum speed is 6.5mb-14mb with estimate of 8mb whilst checking most sites including BT and the current provider, so you cant say its normal.

In reply to a post by candy123:

why cant they increase my actual bandwidth instead of tweaking the snr margin.

Cuz, on a particular line, they are intimately related. The lower the Target NM the higher the sync speed and v.v. Most ISPs allow the Down Target NM to do down to 6dB or even 3dB on stable lines. The up stats are generally independent of the down ones.

Your current down sync is reasonable for your attenuation; maybe 1 Meg shy of what it could get but acceptable.

Your up sync is being damped by the high 24dB up NM. Best try rebooting the router to see if it will improve (despite what ISP tells you the odd resync wont harm).

That's only an estimate. Your actual 7 Meg sync speed is within that range:

In reply to a post by candy123:

my minimum speed is 6.5mb-14mb with estimate of 8mb

Not the best but acceptable.

Edited by XRaySpeX (Sun 18-Aug-13 19:50:16)

In reply to a post by candy123:

Sorry i dont agree with your last paragraph as my minimum speed is 6.5mb-14mb with estimate of 8mb whilst checking most sites including BT and the current provider, so you cant say its normal.

Believe what you like. Based on the stats you posted here...
"Current figures
DSL Type: ITU-T G.992.5
Bandwidth (Up/Down) [kbps/kbps]: 509 / 6.998
Output Power (Up/Down) [dBm]: 12,4 / 18,0
Line Attenuation (Up/Down) [dB]: 24,2 / 42,0
SN Margin (Up/Down) [dB]: 24,3 / 4,3
through speed 5.2-5.5mb ish."

SN margin of 4.3 is already very low for a 42db line. If you lower this much further the line will just keep dropping out. The only way you can get more speed is if the SNR is lowered, but then you will probably see instability. Even short lines normally have a 6db noise margin target, you are already below this indicating your lines being squeezed for speed.
You can get more upstream speed but not more downstream.

The BT estimates are just that, estimates. BT only guarantee you a voice line. They are not under an obligation to give you x speed... If you got a new line you would prob see higher, you might not though. On your CURRENT line it's behaving okay. In an ideal would I would expect a sync around 8000kbps, you have a sync of 6998. It's slightly below my ideal world figure, but then the worlds not ideal. There's external interference, theres crosstalk from neighbours lines, theres poor internal wiring, the cabling to the exchange is worse than perfect, there's aluminium in the lines, some new lamp posts are installed near to the BT lines (hence more interference), etc etc.

A line which was capable of extra speed would be like this

Current figures
DSL Type: ITU-T G.992.5
Bandwidth (Up/Down) [kbps/kbps]: 509 / 6.998
Output Power (Up/Down) [dBm]: 12,4 / 18,0
Line Attenuation (Up/Down) [dB]: 24,2 / 42,0
SN Margin (Up/Down) [dB]: 24,3 / 15.0
through speed 5.2-5.5mb ish.

If your stats were like this above, with a noise margin of 15, then it indicates there's plenty of extra speed that can be provisioned on that line. As your stats ARE NOT like this and the SNR is 4db, it indicates very little, if any extra speed can be provisioned before instability sets in.

Edited by ukhardy07 (Sun 18-Aug-13 19:56:15)

In reply to a post by candy123:

Bandwidth (Up/Down) [kbps/kbps]: 1,213 / 7,838
Line Attenuation (Up/Down) [dB]: 22.5 / 38.5
SN Margin (Up/Down) [dB]: 7.0 / 6.5

You weren't even getting the best from your old ISP. That line with that attenuation should be getting about 10 Meg. So you were even then over 2 Meg shy.

You line must be below average par quality and this is similarly degrading your speed now on your current ISP.

In reply to a post by candy123:

Sorry i dont agree with your last paragraph as my minimum speed is 6.5mb-14mb with estimate of 8mb whilst checking most sites including BT and the current provider, so you cant say its normal.

ISP sets the SNR target margin, DSLAM and modem do the best they can in terms of speed to meet it. There's no manual intervention beyond setting the target margin. Their action in your OP was correct.

You can try different ADSL flavours, different kit, resync at favourable times or tweak the SNR margin with some modems etc. These can affect the sync speed somewhat.

http://www.coolwebhome.co.uk/calc/calculator.php

Downstream Connection Speed(Kbps) 6300
Downstream Attenuation(dB) 40
Downstream Noise Margin/SNR (dB) 9

i get following results
Target Margin: Estimate
9dB : 6300
6dB : 6990
3dB : 7756

Normal speed range at 40dB attenuation is 8000 Kbps to 11200 Kbps

BUT AFTER UPGRADE OF LINE CARD AND THE NEW ROUTER THEY SENT ITS:

Downstream Connection Speed(Kbps) 6990
Downstream Attenuation(dB) 42
Downstream Noise Margin/SNR (dB) 6

i get following results
Target Margin Estimate
9dB 6299
6dB 6990
3dB 7755

Normal speed range at 42dB attenuation is 6500 Kbps to 10000 Kbps

so same results but at 42 db its 6.5-10mb and 40db its 8mb to 11mb...so i cant ask them to put me to 3 db as it may dropout.

just checked my router stats and its snr margin now midnight is 1.7db still holding sync.

I would think you are on a 3dB sync time SNRM - during the daytime you had some spare margin, i.e. 4.3dB, but tonight the margin has reduced to 1.7dB due to noise.

Note that you get the RED traffic light showing line is underperforming now as it was on old ISP.

Sync speed is determined by the Target NM at time of sync, not by the ongoing NM. Your current Target NM was more likely 3dB, not 6dB.

In reply to a post by XRaySpeX:

Note that you get the RED traffic light showing line is underperforming now as it was on old ISP.

Sync speed is determined by the Target NM at time of sync, not by the ongoing NM. Your current Target NM was more likely 3dB, not 6dB.

Why is it in the red and how can i make in the green is the fact the line is rubbish or is it isp side, capping me.

You are not being capped.

It's not this ISP as it was much the same with old ISP.

As I keep indicating your line looks substandard but acceptable.

You could try forcing ADSL2 only mode in your router.

Have you tried from hidden test socket?

Edited by XRaySpeX (Mon 19-Aug-13 12:15:55)

just checked my router stats and its snr margin now midnight is 1.7db still holding sync.

Doubt that will last long, the line will probably drop out. With an SNR this low you risk error build up. Here's an example.

Line 1)A line with a 4.5 Mbps sync and a noise margin of 9db
Little error build up, extremely stable
Line 2)A line with a 6Mbps sync and a noise margin of 1db.
Lots of error build up, lots of potential to drop out.

With line 1, you will likely be able to stream and browse nicely. It will work as expected upto around 720p stream.

Line 2, due to error build up may struggle to stream at all, even though the sync is higher. It may also become extremely slow at loading websites and may eventually drop out and resync slower / DLM will eventually limit it to 6 / 9db noise margin so it behaves ok.

Most lines at 3db are extremely stable and not long lines without too much error build up, Your line could be one of these although I doubt it.

In reply to a post by XRaySpeX:

You are not being capped.

It's not this ISP as it was much the same with old ISP.

As I keep indicating your line looks substandard but acceptable.

You could try forcing ADSL2 only mode in your router.

Have you tried from hidden test socket?

Yes all reading from hidden socket got some more info after reboot.
i checked after rebbot what target snrm been set and its 6db but still slow upload speed however now i swapped my friends router the attenuation has lowerd to 39.3db and getting around 6mb speed, can someone tell me what the difference between max rate and data rate please as below.

Downstream Upstream

SNR Margin 6.1 21.6 db
Line Attenuation: 39.3 24.0 db
Data Rate: 7000 508 kbps
Max Rate 8400 903 kbps
crc 0 0

Data Rate is your actual speed
Max Rate is the theoretical top speed you could get if the DSLAM was not controlling it. like without any NM.