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Fibre35 Slowing Daily

First Timer
Message 27 of 27

Notice my Broadband speed is getting slower by the day. This is measured at the router by the router so has nothing to do with Wi-Fi or internal network.


Router is Fast5364 running latest firmware *******2816t

Router is plugged into master diagnostic socket.

I have reset the router but still the speeds are slowly going down.


My guaranteed min speed is 25.2Mb as per my order confirmation, it has always run around 26 - 29Mb. Past seven days it has been 21Mb as measured by TT and today it is 20Mb.


I have noticed the SNR is rising on the down link 10.4db to 13.3db over night correlating with the drop in download speed from 21 to 20Mb.


Up link SNR is also up slightly from 6db to 6.20db, strange thing is an increase also increase my upload speed from 7Mb to 8.6Mb.


Not sure what else to do, have changed the micro filter.

The only thing that coincided with the slowing down of service was the router for some reason spat the dummy and reset itself loosing all the settings.

Faulty router?


Community Star
Message 1 of 27

SNR changing by small increments like that is totally normal, that is nothing to do with DLM, it is just the characteristics of the phone line. SNR (Signal to Noise Ratio) is a measurement of how loud the broadband signal is compared to the background noise on the phone line, it is normal for the background noise on the phone line to vary slightly throughout the day, so when this happens the SNR reported by your router will change by these small increments.


On Fibre connections DLM will only make changes once a day (in the early hours of the morning), so any changes to SNR at other times will be caused by other things. DLM monitors the quality of your connection for every 24 hour period, and if anything has happened in that 24 hour period that DLM needs to act upon it will make the required changes in the early hours of the next morning, when DLM makes a change it will cause your router to drop and reconnect.


Message 2 of 27

Hello @Skynet_TX 

Thank you very much for taking the time to give an explanation of what is/could be happening. I appreciate the time you have spent writing this up.

Strange I had read the SNR increases in 3db increments too, however mine went up in much smaller numbers sometimes .1 or .2db.

I will keep an eye on it as suggested and hopefully it is resolved now.

Thank you, everyone.

Community Star
Message 3 of 27

Excellent, just be aware that if your router has more than around 5 or so drops (for any reason) in a 24 hour period then this will likely trigger DLM to make an adjustment in the early hours of the following morning (the exception being a shutdown of the router for over 30 minutes which will not count towards one of those drops).


The 'standard' target SNR for TalkTalk is 6dB, however if DLM wants to adjust your profile to try to make your line more stable it can alter that target SNR to a higher number, this forces your router to connect at a slower speed (as it has to connect at a speed that will allow it to achieve that target SNR), DLM tends to increase the target SNR in 3dB jumps, so an SNR of around 9, 12, 15 etc. may well be an indication that DLM has been involved.


SNR won't be an exact static number, it will move around a bit, as the background noise on phone lines changes during the day (i.e. it is worse at peak times), so you will see the SNR move around a bit, but large jumps can often be an indication of DLM getting involved.


Keep a close eye on your sync speed and SNR over the coming days, if Openreach have fixed some issue today then they may have performed a DLM Reset on your line, this will basically set the target SNR back to 6dB and allow your router to connect at the fastest speed it thinks your line can support, however if your router starts to experience drops, or there are lots of errors in the data transfer, then DLM will kick back in again and will start to reduce your speed in the early hours over the coming days.


Note that DLM will also work in the other direction, so if it has reduced your speeds due to a problem, it will also automatically increase your speeds again once the problem has cleared and you have a stable connection. Openreach doing a DLM Reset will get things back to full speed immediately, but DLM would do it automatically over the course of 3 or 4 days anyway.


Message 4 of 27

Glad to hear your speed has recovered. It doesn't really say what the problem was but line test is now passing. You can leave the router off for 30 minutes if you like but it shouldn't really be necessary



Message 5 of 27


34.8Mb and 8.3Mb as tested on TT speed checker. Laptop wired > Router > New Microfilter > NTE Diagnostic socket.

Thank you all for your help.

Chris can you advise what was wrong, in case it happens again?


I will need to move the router to its normal location (not sat on the NTE diagnostic socket) should this be done the same as before leaving it off for more than 30 minutes?

Message 6 of 27

Message 7 of 27



I will do that now and update later.

Thank you all for your advise and help.


Message 8 of 27

Hi ItsBroke,


Current sync speed is 36.2Mbps so could you switch your router off and leave it off for at least 30 minutes then switch back on and retest 



Community Star
Message 9 of 27

What is the actual download sync speed reported by your router, is that only a little over the 18.1 that you get from your speed test, or is it now a much higher number?


If it is a much higher number then switching off your router for over 30 minutes may well help get the throughput speed up to something much closer to the sync speed.


Switching the router off for over 30 minutes should not get detected by DLM as a 'drop' as DLM is clever enough to assume that if it was disconnected for that long then it was an intentional power down.


Message 10 of 27

Hello @Chris-TalkTalk  Update


The router link was dropped at 00:30 last night and automatically re connected, ( not sure if this was a line reset by BT).


SNR is now 6db down from 15.2db on Down link  overnight.


The download speed is  still very low, a TT speed test on a device wired directly into the router = 18.1 down 8.1up.

Laptop > Router > New Microfilter > NTE Diagnostic socket. Nothing else connected no phones etc.


Message 11 of 27

Message 12 of 27

Thank you.


Message 13 of 27

Thanks for the update 


DLM hasn't changed your line profile since the 12th, current sync speed is 19.1Mbps down and 10Mbps up


Line test is now failing so I've logged this out to BT Openreach as a non-appointed task. Openreach will investigate over the next 72 hours and may contact you directly if they need to access your home. if you don't hear anything before Friday please bump the thread and we'll check for updates


Message 14 of 27

Hello @Chris-TalkTalk  Update


Yesterday I took the old TT Router offline at 17:45 the SNR was 13.4db.

There was NOTHING connected to the NTE socket for three hours.


I bought a new router, ArcherVR2100 and plugged it in to the diagnostic socket on the NTE.

At 20:45 the SNR was 14.1db.


After performing a firmware upgrade and a reboot at 20:55 the SNR was 14.7db.

My download speeds are now less than 20Mb measured at the router at the PC they are 16.8Mb. Ping varies from 75ms - 125ms.

During the three hours that NOTHING was connected to the NTE why did the DLM adjust my line?

The router is still plugged into the diagnostic NTE socket, there are no phones connected to the line.

Router > New Microfilter > NTE Diagnostic socket.


The Router has not been off for 10 hours the SNR Down link is now 15.2 no errors reported by router.



Message 15 of 27

Hi ItsBroke,


OK thanks. It usually takes at least 48 hours for DLM to respond to any improvement by setting a faster line profile 





Message 16 of 27

Hello Chris,


I was told to move the router on Saturday by TT cust support and plug into the NTE test socket, so yes it was manually shut down.

OK I will install my new router into the test socket and see what happens.

How long do you think this will need to be left for it to make a difference?


Message 17 of 27

It would need an engineer visit to have DLM reset and if the connection then remains unstable DLM will just drop back to a slower profile again to stabalise the connection


It can be both, did you power the router off manually over the weekend


It's is worth testing with another router to see if the disconnections continue. If the connection is stable with the new router then DLM should move you back to a faster profile 




Message 18 of 27

So can it be reset?

"Reconnections" is this defined as the router dropping the connection and reconnecting or it being powered off manually, or both?

I have a new router I could test but there is no point if its going to be capped so low.

Is this a one way action by the DLM or can it automatically up the profile speed?


Message 19 of 27

Hi ItsBroke,


Reconnections will cause the line management system (DLM) to move to a slower profile in an attempt to stabalise the connect, this will increase the SNR


There were 13 reconnections on Saturday and 5 yesterday


DLM changed your line profile at 01:45 on the 12th


The climbing SNR is just a symptom of the profile change. The new profile is capping the speed at a lower speed which results in a higher SNR




Message 20 of 27

Hello Debbie,

How will reconnections increase my SNR? (curious)

SNR has a direct impact on speed.

How many reconnections are you seeing?

This has been happening since August you can see at your end the Router has not been switched off for ages and yet the SNR went up and the speed came down.

I contacted you guys after running several tests on your website which said I have a problem.

If the router had been on for over six weeks and I presented to TT with a download speed of 21Mb on Saturday why would any reconnections over the weekend suddenly make a difference? (curious)...

Are we not interested in the climbing SNR. Noticed the upload speed is bang on and the SNR is 6db (perfect).

Prior to moving the router to the NTE socket it had an SNR  or 10.4db and a download speed of 21Mb its now got an SNR of 13.4 and a Download speed of 20Mb