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[Cecil_rfc]

Hi all,

New to the forums and have done lots of (very interesting!) reading about FTTC and how it all works.

I've just moved from EE to a new ISP, as EE said my line couldn't go any faster than being banded at 40/10.  Since I've moved to my new provider, my speed has increased slightly but still not to what I expecting.

Currently my download speed is like this from Speedtest:

Download = 39.66 Mbps  (this has been around 41Mbps over the last 24 hours)
Upload = 13.12 Mbps

When I type my address into https://www.broadbandchecker.btwholesale.com/#/ADSL/AddressFeatureProduct I can see that my figures are as follows:

                                             Downstream Line Rate         Upstream Line Rate            Downstream Handback threshold
                                        High       Low                         High     Low
VDSL Range A (Clean)             59.3     40.7                    13.3        8.5                         35   
VDSL Range B (Impacted)        57.8     35                            13        7.8                      30.7   


Then when I check my router stats:

                              Upstream   Downstream
Current Rate (kbps)   14156   47901
Max Rate (kbps)   14085   64083
SNR Margin (dB)   6.2           6.1
Line Attenuation (dB)   4.9           13.9
Errors (pkts)           24            0

Should I be getting faster speeds than I am getting?  I'm using a wired connection so not connecting to wireless.

Also, my next door neighbour (semi detached) is with Sky and showed me a screenshot of his speedtest on his phone which showed his download as 59Mbps.  We are both using the same exchange, and actually when you put his address into the bb checker, his speeds are LOWER than what mine are.  This all makes no sense to me.

Would any of you kind people care to help an old man out and tell me if I should raise this with my provider, or accept it as the way it is.

[Weaver]

Welcome to the Forum, from another Cecil! 

The sync rate shown by your modem is the critical thing and I think you should disregard everything else as speedtesters are often very unreliable when they are tests of TCP’s performance as they test the whole TCP system including the boxes at the two ends, not the line. The 41 Mbps speedtest you quoted is 87% of the downstream sync rate, which is a bit slow, but not unreasonable as it could be that the speedtester is a bit slow or you are using G.INP with the L2 retx system set to "high" which has quite an associated overhead, about 6% which would mean that you would expect to see IP throughput at around 91% of the sync rate. So 91% - 87 % = 4% unaccounted for, which is not outrageous. Without the L2 retx system on the "high" setting we expect to see an IP throughput downstream of around 97% of sync rate. The overhead of TCP and either IPv4 or IPv6 is either 40 bytes or 60 bytes and in a 1500 byte total length IP packet the inefficiency is then either 40/1500 (IPv4) = 2.67% or 60/1500 (IPv6) = 4%. So your speedtester results will depend on which IP protocol you use, with IPv6 being slower. Notice that that’s where your missing 4% could well be gone. So in fact we have one unproven story that would account for your numbers. However that was all guesswork as we don’t even know if you have G.INP never mind L2 retx="high". If that isn’t true then your TCP payload throughput should be about (97% - 2.67%) * sync rate (IPv4) or ( 97% - 4% ) * sync rate (IPv6).

The sync rate is what it is. Your noise levels, your crosstalk, line length and copper thickness which controls signal attenuation, all these factors affect the sync rate which, after overheads have been subtracted, as above, is the absolute limit to the speed you can get. You can’t change the sync rate much as BT won’t allow ISPs much control in FTTC systems. Putting your downstream SNRM down to 3 dB instead of your current 6 dB would speed up downloads a fair bit, but your ISP would have to tell you if that’s possible with your cabinet and with the error rate on your line, as reducing the downstream SNRM will reduce reliability.

I wouldn’t worry about it. Your speed is not fantastic but that’s just your line. Changing things like house-internal DSL wiring, having a good quality master socket and high quality lead from the master socket to your modem might make a tiny bit of difference but I’m sceptical.

My best DSL line achieves a sync rate of about 3 Mbps downstream, and 0.6 Mbps upstream. I have four copper lines combined to give me four times the speed in both directions, although for reasons unknown the upstream combined total isn’t quite * 4. So think about it, you could be me!

[burakkucat]

New to the forums and have done lots of (very interesting!) reading about FTTC and how it all works.

Welcome to the Kitz forum. 

I've just moved from EE to a new ISP,

Who is your new provider, please?

Currently my download speed is like this from Speedtest:

Download = 39.66 Mbps  (this has been around 41Mbps over the last 24 hours)
Upload = 13.12 Mbps

. . .

Then when I check my router stats:

                              Upstream   Downstream
Current Rate (kbps)   14156   47901
Max Rate (kbps)   14085   64083
SNR Margin (dB)   6.2           6.1
Line Attenuation (dB)   4.9           13.9
Errors (pkts)           24            0

I always look at the synchronisation speed and SNRm first of all. You have 47.9/14.2 Mbps DS/US. That tells me your new service has been provisioned on the Openreach 80/20 Mbps product. It doesn't look like banding has been applied by the DLM.

The current SNRm of 6.1/6.2 dB is the default target for a new service. Depending upon the manufacturer of the cabinet DSLAM it is possible that G.Inp could be active. If that is the case then the target SNRm could be reduced, stepwise by 1 dB over a number of days, to a minimum of 3 dB. The DLM will be checking the stability of the service and will settle on a target SNRm which is found to be the most stable. A reduction of the target SNRm to 3 dB will give an increase in the synchronisation speed.

With the limited amount of data visible, it appears that service is currently operating as well as I would expect. However let's see what other members have to say . . .

[Cecil_rfc]

Thanks for the replies.

New provider is Poptelecom. 

I just don't understand my speeds compared to next door.  These are my neighbours stats from the bb checker website.  Bear in mind he's sent me a screenshot of speed test from his mobile phone connected via wifi which had a 59MBps download speed:


                                             Downstream Line Rate         Upstream Line Rate            Downstream Handback threshold
                                        High       Low                         High     Low
VDSL Range A (Clean)             47.2     35                         8.4        6.3                         30   
VDSL Range B (Impacted)       45.8     30                          8.3        6                           25   


I just can't get my head round why his speeds are higher, going by these stats, compared to mine and I'm getting lower speeds.

Is it worth me buying a new router that is capable of lowering the SNR margin (again, I've read that some routers can do this, my TP-Link cannot).

[meritez]

Welcome to the Kitz forum.

How long has the line been live with Pop?

[tubaman]

There are many reasons why your speed can be different from your neighbour's, such as bridge taps outside or unfiltered extensions inside your house, especially star wired ones. Crosstalk can also cause speed losses and sometimes it's just the luck of the draw that a neighbour gets a better pair of wires than you. Frustrating as that can be there is little that you can do about it. The estimates given by the Openreach checker are just that, and real life speeds can vary considerably from them.
As it's a new service I would certainly wait for a week or so to see if G.INP lowers the SNRm (assuming you are connected to a Huawei cabinet) before thinking about other possible measures.

[Cecil_rfc]

Yea it's only been 3 days so I'll wait a little longer to see if anything changes.

[meritez]

Yea it's only been 3 days so I'll wait a little longer to see if anything changes.

Your snr is at 6db, if pop still use talktalk wholesale for their backhaul it may not drop to 3db.
Sky do support the 3db snr but I have no idea if pop have a 3db profile.

[g3uiss]

I wouldn’t even consider trying to change the SNRM using a Lantiq based router. Unfortunately comparison with neighbours is usually fruitless. Every pair is different.

[tubaman]

Your snr is at 6db, if pop still use talktalk wholesale for their backhaul it may not drop to 3db.
Sky do support the 3db snr but I have no idea if pop have a 3db profile.

I'm confused - surely if the connection is via an Openreach cabinet it'll be using Openreach's DLM process irrespective of the backhaul connection?

[Chrysalis]

I wouldn’t even consider trying to change the SNRM using a Lantiq based router. Unfortunately comparison with neighbours is usually fruitless. Every pair is different.

To add to this I have done this 3 times with lantiq based routers, to move the SNRM downwards and on all 3 occasions I got banded (quickly as well I might add), so fairly confident that is one of the triggers for DLM to band your line.

[meritez]

I'm confused - surely if the connection is via an Openreach cabinet it'll be using Openreach's DLM process irrespective of the backhaul connection?

Different carriers use different NGA profiles:
https://kitz.co.uk/adsl/DLM.htm

ISP's known to use NGA Speed Profile: AAISP, BT, Plusnet, Zen.
ISP's known to use NGA Standard Profile: EE, Sky, TalkTalk, Vodafone.

[Alex Atkin UK]

To add to this I have done this 3 times with lantiq based routers, to move the SNRM downwards and on all 3 occasions I got banded (quickly as well I might add), so fairly confident that is one of the triggers for DLM to band your line.

I didn't get banded doing it until my drop wire went bad, so as you'd expect it really depends on the line quality if fiddling with SNRm triggers banding or not, at least on an ISP using the Speed profile on an ECI cab anyway.

I certainly wouldn't do it until you've had the service a while to see what DLM does on its own though and probably not on a Hauwei cab as if DLM is not aiming for 3dB on its own, it has its reasons.

[Chrysalis]

I think you didnt need to go as extreme as me to hit your target sync rate? so the extremity of the adjustment might be a factor as well, but I do think the coincidence is too much to ignore, I have only been banded 3 times, and all 3 times was shortly after I manipulated the SNRM downwards on a lantiq modem.

[j0hn]

Different carriers use different NGA profiles:
https://kitz.co.uk/adsl/DLM.htm

They all use the exact same Openreach DLM.
Each NGA policy has the exact same profiles available.
Only the trigger thresholds differ.
Every single Talktalk line connected to a Huawei DSLAM is capable of a 3dB SNR target if the line is clean enough.