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Question about DLM & Reboots

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3 REPLIES 3
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Wise Owl

For those that don't know DLM (dynamic line management) is an Openreach system used to control speed and stability of your FTTC connection. It monitors the line and if a certain threshold of droppped lines or errors occurs it drops your speed and/ or applies error corrections (increases latency/ ping). If after a set period (I think 8 days) no further errors occur the DLM will increase the line speed again and resume monitoring. If after a further 8 days no errors occur it will again increase line speed and so on every 8 days until it reaches a point where the errors or dropped lines re-occur. The idea is basically to establish the fastest stable line speeds. I see lotsof posts from people bemoaning the DLM but it is actually your friend. A slower stable line is much better overvall than a  faster unstable line.

 

Anyway back to the point of this post.

 

Yesterday I switched from a dying HG635 to a FAST 5364.

 

The HG635 kept dropping the line and resetting itself so the DLM presumably quite correctly "saw" those as errors. In addition to that the line was dropped when I switched routers and again after I requested a firmware update that the OCE's sorted for me (thanks guys & gals). I then starting setting up the router to my liking and rebooted after each change. I also rebooted several times becasue I had an issue with a rogue IP address that I couldn't identify (I found out it was the Sky Q box after nmap'ing but that' a different story). The point is that the router must have been rebooted at least 20 times yesterday, which I suspect might also trigger the DLM to kick in but I don't know if the DLM can tell the difference between a dropped line/ error and a routine reboot.


When  I checked this morning the router had reset at around 3.00 a.m. (the DLM makes changes in the early hours of the morning) and my down and up speeds had reduced (by 2-3 Mbps on each) so it looks like the DLM is making changes but that could be due to the HG635 dropping rather than my reboots.

 

The thing is I've not finished tweaking yet and so they'll be a good few more reboots required.

 

Does anyone know if the DLM can differentiate between a routine reboot and a dropped line? If it can't then I don't really want it to "fix" my stability any further because remmeber it needs at least 8 days of a stable connection to increase speeds again. If it drops my speed again then i think I'm at least 16 days away from getting back to full speed. If it drops my speed a third time then that's 24 days.

 

Is there a way to force the DLM to recognise a routine reboot such as powering down for a while  and then switching back on?

 

Or is the best approach just to bite the bullet, make all the necessary changes and accept that I'll have a slightly reduced speed for a while?

 

Fritz

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Community Team - TT Staff

Hi Fritz,

 

I'm not entirely sure how the BT DLM system works regarding noticing disconnection but I know with our DLM (on our LLU circuits) it's best to avoid switching router off and immediately back on again as this could be seen has a dropped connection. It's generally best to leave the router switched off for at least 5 minutes (if you're only doing it once or twice in 24 hours, it's not really going to matter anyway)

 

Chris

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Wise Owl

Hi Chris

 

Thanks for the reply.

 

I think I'll just make all the changes I need then reboot once. I've backed up my config so far so if anything untoward happens I can always jump back to that point.

 

Fritz

Highlighted
Community Team - TT Staff

OK, just let us know if you need any further assistance 🙂

 

Chris