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Possible DLM has lowered my speed?

Message 13 of 13



After changing the talktalk modem I believe my line has come under the effect of DLM, meaning my speed has decreased by about 12mbits.


I've tried plugging back in the old Talktalk modem but the speed has stayed the same and not returned to previous speeds.


I have a VDSL connection and before this change I was getting 37mbits and currently get 24mbits after changing modems. During that change i didn't have my VDSL cable plugged in for around 15-20mins.


If someone could look into this and get back to me that would be great, thanks.


Message 1 of 13

Hi fffreedo


glad the speeds have improved.


I'm with Skynet_TX, and usually power down for 30 minutes when swapping routers as different chipsets may negotiate the connection in a slightly different speed / manner.





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Message 2 of 13

Hi @fffreedo,


Agree with Michelle that it should not be necessary to leave 30 minutes, however from my own experience I have found that the 'new' router often does not run at its full potential if it connects to a session that was originally created by a different router. When I've switched between the Huawei and Sagemcom TalkTalk routers the 'new' router has not synced at the full 40mbps I usually get when I've just quickly switched them, but after a +30 minute shutdown it has then synced at 40mbps.


Can't say I fully understand why, but I can only assume it is session related as the street cabinet will 'forget' the old session after 30 minutes, meaning you get a new one when you power back on.


Also in terms of DLM itself, if you switch routers quickly DLM will count that as a 'fault' as it will have seen the connection drop and them come back. One single drop won't do any harm, but if you have more than 5 or so drops in a 24 hour period then that is likely to trigger DLM to start adjusting your line profile. If you leave over 30 minutes between shutting down and powering back on then DLM is clever enough to assume that was a deliberate power down, and so it won't count that as a 'fault'.


Message 3 of 13



Thanks for the update and I'm glad to hear that the speed has increased. You shouldn't have to disconnect for 30 minutes before connecting your alternative router.





Message 4 of 13

Hi Michelle,


I turned off the router for about 1hour in the night and speeds came back to normal after reconnecting.


Does this mean if I want to connet my other router I should follow this same procedure? i.e. disconnecting for 30+minutes before connecting the other router.

Support Team
Message 5 of 13

Hi fffreedo,


How are you getting on?





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Message 6 of 13

It can't hurt to try, although do bear in mind that the staff here won't be able to test your connection until your router is powered back on again.

Message 7 of 13

Fair enough, thanks for the advice.


Perhaps a power down over the night would be sufficient?

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Message 8 of 13

Ok, the issue is unlikely to be DLM, as DLM would tend to affect the sync speed, and you say your router is still reporting 40mbps. Also for Fibre connections DLM will only make adjustments once a day, in the early hours of the morning. Quickly switching between different brands of router can often cause the throughput speed to drop as the 'new' router will be trying to use the session details that were created by the 'old' router, however powering down for over 30 minutes will usually resolve this as this will force a new session to be created for your connection in the street cabinet.


Staff here will be back tomorrow and will be able to do some further checks on your connection, but in the meantime all I could really suggest is try a slightly longer power down, although anything over 30 minutes should really have given you a brand new session.

Message 9 of 13

I've tested on both wireless and wired with the same result. Although there shouldn't be any problems with wifi as it's been working decently for the past year with speeds of around 36mbits.


The reason for the change was that I wanted a router that had the ability to QoS which for some reason isn't included in the default talktalk Router/Modem combo.


Currently I'm capped at 20mbits down/8mbits up no matter the type of connection but the admin interface of the router states otherwise.





  Actual Rate [Kbps]Maximum Rate [Kbps]Noise Margin [dB]Attenuation [dB]Power [dBm]

Line 1

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Message 10 of 13

Are you running the speed test on a wired or wireless device. If all is working well, with a sync speed of 40 you would hope to get a speed test result around 36 - 38 on a wired device, results on wireless devices could vary greatly depending on your local Wi-Fi environment.


Message 11 of 13

Hi Debbie thanks for the response.


I've just done that, powered off at 18:54 and powered back on at 19:30. While my modem is saying "40mbits down" within the interface, when speed testing on talktalks speedtester I'm only getting a speed of 20mbits.


Edit: this is using the talktalk provided router/modem combo


Support Team
Message 12 of 13

Hi fffreedo


I'm sorry to hear this.


I've completed a line test which hasn't detected any faults and your line is in sync at 39.2mb.


Please can you power down your router for a full 30 minutes and then run another speed test?