Just had FTTC installed. Interpreting line stats

So upgraded from ADSL to FTTC. 38/10 service. These are my line stats which i expect

Connection Speed 39994 kbps 9997 kbps

Just not sure what these mean:

Noise Margin D0( 9.6) D1( 9.6) D2( 9.6) dB U0( 12.9) U1( 10.2) U2( 10.3) U3(N/A) U4(N/A) dB

On ADSL you had 1 noise margin, now i have multiple ones. So what do they all mean?

Also these are my results - https://www.thinkbroadband.com/speedtest/16933011327...

Upload seems a abit slow for the sync speed? Or is that normal? Im guessing download is normal as you never get the full sync speed due to overheads etc

Edited by bobble_bob (Tue 29-Aug-23 10:29:12)

You've only given a snippet of the stats, a full set might be more helpful.

Sync speeds are good, full speed for your service. Upload throughput a bit low.

The noise margins you have shown are split into the various Downstream and Upstream frequency bands and look good, (N/A) means the band is not in use which is normal for the higher upstream bands.

The router stats may also show single average values for DS and US margins.

Thats the only line stats available on the D6400 Netgear router that i know of

Any reason the upstream would be slightly low? Not much of an issue i dont really upload much anyway

In reply to a post by bobble_bob:

Any reason the upstream would be slightly low? Not much of an issue i dont really upload much anyway

What was you expecting?

Edit: OK I just looked at the speed results it may be congestion.

Edited by deleted (Tue 29-Aug-23 10:54:48)

Well syncing at 9997 kbps i was expecting maybe 7Mbps at least

Maybe im wrong?

Edited by bobble_bob (Tue 29-Aug-23 10:54:27)

In reply to a post by bobble_bob:

Well syncing at 9997 kbps i was expecting maybe 7Mbps at least

Maybe im wrong?

Just updated my last post after looking at speed results. Test at various times of the day to get a better overview.

Yea will do. What speeds would you expect to see for that sync? Its still 5 times fast than what i was on before so cant really complain.

Downstream seems spot on which is the main thing

Edited by bobble_bob (Tue 29-Aug-23 11:01:43)

The SNRs look good - tyically 9 on the Down and 12 UP. Ypu are hitting max - almost on down, but up is definitely a little low especially with 12dB..

Keep doing wired tests and various times of te day and see if it is stuck fast!

I decided to use the pre-existing Cat5 extension cable i had with ADSL. It adds about an extra 12m of internal wiring so i can have the router where i want it. Perhaps that is causing the slowness, although i would have thought it would have effected download too which it isnt.

I will try with a smaller cable see if that helps

Try that ...


It is always worth having a decent cable, but my brain has gone dead, and cannot remember if FTTC is an RJ11/12 output - I think it is. If so, have a look at Kenable for their ADSL+ cables made with 2 pair Cat5e:

https://www.kenable.co.uk/en/107-adsl-rj11-cables?le... other lengths available, the ones at £3.10 / £3.26 depending on colour.

I installed a 2m one for someone to replace their ISP supplied one and immediatley the speed jumped bu about !0Mbps (down) not pronisig it in your case, but decent cables are worth it - especially at those prices.

Yea cheers i always pay abit extra for decent cables

Well this is bizarre. Testing on ethernet gets those results i posted. Testing on wifi gets my 8Mbps upload (same download)

Its a short Ethernet cable from the router to the PC so not sure why wifi would be giving faster results?

Edited by bobble_bob (Tue 29-Aug-23 11:31:02)

So at least the link is fine.


Also, the cable I linked to is quick small and discreet - not as chunky as full Cat5/5E.

Yea will look into that cheers.

Doing multiple tests on multiple devices, download is fine and consistent. Upload that is odd. I think the upload is an issue with the thinkbroadband test when on ethernet

PC wired - thinkbroadband i get 5-5.5mbps. On the OOkla speedtest (single thread same as thinkbroadband) i get 9mbps

PS5 reporting 8-8.5mbps
Iphone and Android on thinkbroadband (wifi) get 8-9mbps

So the only anomaly is thethinkbroadband test wired

@realalemadrid, found some other stats that may help.

Connection Speed 39994 kbps 9997 kbps
Line Attenuation D0( 12.5) D1( 31.6) D2( 50.1) dB U0( 4.1) U1( 25.3) U2( 39.1) U3(N/A) U4(N/A) dB
Noise Margin D0( 9.5) D1( 9.4) D2( 9.4) dB U0( 12.5) U1( 10.2) U2( 10.3) U3(N/A) U4(N/A) dB

Thats all the D6400 lists. Overall those now i know the upstream is getting full speeds despite what the speedtest wired suggests, im happy

If the cabling were causing slowness, then it would show in the sync speed.

Yea i thought that, but as i mentioned further down i dont think the speed is being effected. All tests ive done apart from the thinkbroadband wired test show a upstream speed in excess of 8Mbps

That is what I always believed - but I can remember changing the cable for someone with a downstream issue and whilst sync remained much the same, throughput improved. Cannot explain exactly why, it just did and replacing the original dropped throughput.

I think if there is interference caused by a poor cable it might. There could be enough that the data isnt getting through and you have dropped packets, but not enough to lose sync.

So since getting connected on Tues morning my connection been flawless. Syncing a max rate for a 38/10 service and speedtest maxing out (apart from the thinkbroadband wired on the upstream but wifi its fine)

I did read that the DLM sets your profile to open for a few days, and on the 2nd night it then tinkers will your line depending on how its behaving. So checked this morning of the 2nd night and indeed got a resync around 1.30am. My new line stats:

Speed40000 kbps9997 kbps
Line AttenuationD0( 12.5) D1( 31.6) D2( 49.9) dBU0( 4.1) U1( 25.3) U2( 39.0) U3(N/A) U4(N/A) dB
Noise MarginD0( 12.8) D1( 12.8) D2( 12.8) dBU0( 9.9) U1( 10.1) U2( 10.1) U3(N/A) U4(N/A) dB

So pretty much identical from my last stats apart from the SNR on the downstream has jumped up 3db roughly. Speedtests still all showing max speed. I thought maybe has the DLM turned interleaving on, but pings are now 7ms compared to 14ms before the resync

Unfortunately the D6400 router doesnt display errored seconds etc. So is a resync on the 2nd night normal, and what's the DLM actually done?

Edited by bobble_bob (Thu 31-Aug-23 06:56:32)

Which ISP is it?

The resync on your line may have caused your PPPoE session to reconnect and terminate on a different BRAS at the ISP.

Pulse8 (they use TTB)

A different BRAS wouldnt improve my SNR tho while still maintaining the same sync speed i would have thought

Edited by bobble_bob (Thu 31-Aug-23 09:00:21)

Netgear block the telnet access needed to obtain the full DSL stats.

There's a post on the kitz forum showing how to enable it if you're technical enough

https://forum.kitz.co.uk/index.php/topic,15306.msg28...

It's a Broadcom chipset so very detailed stats available over telnet.

It's currently showing you the noise margin for each of the downstream/upstream bands and not the lines overall noise margin.

Edited by j0hn83 (Fri 01-Sep-23 04:54:47)

Thanks will look into that.

Oddly my noise margin increases during the night by 0.5db. Which is strange as noise margin usually decreases slightly at night

In reply to a post by bobble_bob:

Pulse8 (they use TTB)

A different BRAS wouldnt improve my SNR tho while still maintaining the same sync speed i would have thought

No, but it could affect the routing of your traffic, which could affect your measured upload throughput.

Note that an *improved* SNR implies a *lower* sync speed, if the line conditions are the same. This might be an artefact of how it's measured, or it could be an environmental change (e.g. a source of interference has gone away)

In reply to a post by bobble_bob:

Thanks will look into that.

Oddly my noise margin increases during the night by 0.5db. Which is strange as noise margin usually decreases slightly at night

In the old days on ADSL noise was often seen to increase at night. Kitz have an article on this that states

During the hours of darkness there is increased radio frequency interference in the atmosphere which all broadband lines will pick up to some extent. During the evening/night the SNR trace becomes jittery and the SNR Margin falls, but the line will recover the next morning.

Yea which seems odds mine is the opposite. I get a better SNR at night

In reply to a post by bobble_bob:

Yea which seems odds mine is the opposite. I get a better SNR at night

It's very difficult to predict interference levels... too close to a radio transmitter and it will probably increase at night, but if that transmitter is a taxi firm it may get worse during the day. Too close to the wrong sort of factory (eg one that does a lot of arc welding) and it may get worse during the day, and vary depending whether they work shifts or not. All sorts of possibilities, you just have to live with what you've got.

My line goes through a small industrial estate and was quietist between about 11am and 1pm (lunch hour?), so that's when I tried to do forced re-syncs if I wanted to try for a better sync speed . Even then it didn't always work

Edited by billford (Fri 01-Sep-23 10:40:50)

In reply to a post by bobble_bob:

Well syncing at 9997 kbps i was expecting maybe 7Mbps at least

Maybe im wrong?

9997kbps is the equivalent of 10Mbps, so that's actually higher than 7Mbps.
If this was 7000kbps then that would be 7Mbps.

Now if you're saying that you're only getting 7Mbps in a speed test with a sync speed of 10Mbps that's pretty normal too. Not all speed test servers will give you exactly the same upload speed as what your router is syncing to. This will also apply to download speeds as well.

I believe there is always some speed lost from what your router syncs at due to overheads etc

So 1 week since i got FTTC installed

Ive had 3 disconnects during that time (1 was a power cut so not counting that). So im averaging 2-2.5 days synced before a resync

Both resyncs have happened during the night - 1 at 1.30am the other last night at 12.20am. Could that be the DLM?

The odd thing is the resync syncs at the same speed (40000kbps/9999 kbps) so getting full speeds for my service and the pings improved so no interleaving. The down snr gone from 10db to around 12.5-13db at the same sync speed. Upstream remained roughly the same at 10db give or take.

The disconnect last night lastes 5 mins which suggests something more than DLM just resyncing the line.

Guess i need to use the Netgear telnet hack to see my full stats

Edited by bobble_bob (Tue 05-Sep-23 06:55:51)

Yes, it could be DLM. DLM usually happens first 10 days after switching. Now some people report that they don't experience this when switching FTTC providers.

I however, have experienced it on 3 occasions thus far. When I was with Plusnet ADSL and then when I switched to TalkTalk FTTC in February 2020 for 10 days it occurred before it stabilized.

Then I switched to BT FTTC just over a year ago and the same experience occurred for me again.

10 days hasn't yet passed for you to test. But the fact that this is happening at night time is a typical indicator that it is DLM. Because my experience was exactly like yours between 1 to 1:30am.

Your SNR is very good. If you're getting 10-13dB I'd believe there's little line interference. But of-course DLM can also increase the SNR if it detects that your sync is not being maintained at lower dB.

I sync at 3dB but I'm on 80/20. It is possible that if I downgraded to 40/10 then I'll sync at higher than 3dB because lower speeds usually produces higher SNR and higher speeds reduces SNR.

Also keep an eye on router firmware update. In your router stats it should show the date for the last firmware update. During this time at night router firmware updates can also occur.

4 days ago my BT Smarthub 2 restarted and I checked the Firmware updated:Fri Sep 1 01:03:13 2023. I knew this was router firmware upgrade.

When you switch to a new ISP your router may be upgraded multiple times for the latest router firmware since your stock router that is shipped is outdated. You can't disable ISP router from updating firmware automatically. The only way is to have your own third party router.

Also during the first 10 days when switching you must not turn your router off. I know some people do that and that can mess up with DLM finding a stable line in which, DLM will continue past 10 days until it finds a comfortable spot where it no longer resyncs. Power outages can also trigger DLM as DLM interprets this as a line fault, it can't distinguish between a connection loss due to power cut or due to line noise interference.

Thank you. Yea this is a 3rd part router and firmware up to date so nothing going on there.

If its DLM im not sure what its actually doing. The 1st resync lowered by pings by half (16 to 6ms i believe) so maybe it turned interleaving or some error detection off i dont know.

But considering all resync events have meant i have resynced at full 40/10 then its not banded me or anything on a lower profile. If anything its the opposite as SNR is getting better while maintaining the same sync speed.

Interestingly Talk Talk (who Pulse8 use) downdetector did register a mini spike of people report issues around the same time mine went down last night, so maybe it was something else that triggered it