It doesn't really matter. If you find a cure, DLM will automatically raise the line profile within a few days. Are you load-balancing these 2 lines, or are they separate?

The DLM on FTTC is Openreach and cannot be removed. If it has imposed restrictions due to a fault it can be reset by the engineer after they (think they) have fixed it.

TalkTalk do not have control of the DLM, unlike their ADSL2+ LLU which is controlled by their own kit in the exchange.

The 2 lines go into a Prosafe SRX5308 Quad WAN VPN Firewall which load balances.

I should probably change both the supplied ISP modem/routers as neither can be put into modem bridge mode, so won't pass the WAN IPs through.

Before on ADSL I used to use 2 bipac modems in half bridge mode which worked a treat.

One presumes the drop wire to the home is twisted pair and not very very old untwisted.

The old non-twisted stuff was only ever single pair, so both lines cannot be through the same dropwire.

Another thought on DLM, for a few weeks the BT modem was reporting 57M sync but 69M max line rate, shouldn't DLM have raised the sync to nearer the max?

Before todays visit, the TT modem was synced at 78 with a max of 79 when the BT modem was on as well.

Sounds like your visitor has broken something. You'll probably need another visit.
The Openreach modem, plenty available on Ebay, will pass the WAN IP straight through. 2 of those perhaps? If you get the HG612 v3B, you can unlock it and configure it greatly.

Yes but I don't really know what he could have broken, he says he only re-terminated a couple of the junctions on the BT line and didn't touch the other.

I can only assume there is a chronic crosstalk problem in the drop wire but I can't work out how he's made it worse.

He is coming back Tuesday, think he said he would bring or talk to his "coach", think he was quite new to fibre but was doing his best.

At the start of the day we had syncs of 80 + 57, after the *fix* we had syncs of 56 + 53

Maybe he caused some instability during the fix and it's just DLM applying interleaving or capping? Can you get any stats from either modem?

Can't get any real stats, no telnet on the HG635 it seems well locked down, these are the basic stats with the Homehub switched off on the other line:-


DSL synchronization status:

Up

Connection status:

Showtime

Upstream line rate (kbit/s):

19999

Downstream line rate (kbit/s):

79987

Maximum upstream rate (kbit/s):

31084

Maximum downstream rate (kbit/s):

99391

Upstream noise safety coefficient (dB):

15.7

Downstream noise safety coefficient (dB):

11.5

Upstream interleave depth:

0

Downstream interleave depth:

0

Line standard:

VDSL

Upstream line attenuation (dB):

20.2

Downstream line attenuation (dB):

10.9

Upstream output power (dBm):

6.8

Downstream output power (dBm):

13.7

Channel type:

None

I've ordered a couple BiPac 8800NLs an a morning delivery tomorrow, should be able to get full stats from them.

No issues here - I have 2x 80/20 lines, one from Sky, and one via my work - both use the proper OR modem to terminate, both have no issue running at full 80/20.

I'd suggest the "all in one" routers those providers like aren't great... and aren't coping particularly well with the interference/crosstalk.