The reason that the IP Profile hasn't updated yet is because DLM doesn't work on the fly as it does on ADSL. It's important to remember that they do NOT work in the same way.
On this connection, there's a need for Interleaving to be switched off, perhaps that's for gaming, or for other services which requires low latency. The case here is that, the line errors with Interleaving Off, but with Interleaving on Low on the downstream direction, the line performs well and absolutely fine - DLM is doing exactly what it should do. Whether or not you want Interleaving on or off, isn't something we have any control over at present.
It's almost impossible to run a line at 80M with Interleaving on, which is why you'll find the circuits that have Interleaving on run at 74M. As Interleaving has been on this line before, a 'Caution Counters' have been set which means that the line status is likely to change depending on stability. I'll explain more about Caution Counters when I write documentation up on FTTC DLM.
A couple of questions that I'd like to ask the wider community regarding the speed on FTTC and please bear in mind that I appreciate that everyone uses their connection for different things, so I'd like to try and keep this as constructive as possible, whilst remaining realistic.
What can you do on a 74M line that you can't do on a 60M line?
Is the additional 8ms latency causing that much of a problem? If so, how and why?
I think FTTC is all about setting the right expectation, and it really doesn't matter what ISP you go to in essence, because any ISP that uses the same BT Network and infrastructure will use exactly the same DLM, exactly the same Cabinet, the only major difference may be, is the policy that you're put on by the ISP (Speed/Stable/Super Stable).
The right expectation is, that FTTC isn't a guaranteed 80M service, there are a lot of things that getting the perfect line depends on; Line Quality, External Interference, Crosstalk, D-side copper/aluminium quality - the list goes on. It's important to understand that whilst we want and aim to deliver the best possible service, that in realistic terms, you may not get the speeds and quality that you want. We'll do our best to ensure that any genuine faults are fixed, but if, for example an external third party source of REIN has caused Interleaving to go and your speeds should be 60M but have dipped to 40M this isn't indicative of a fault, it's indicative that there's an external interference issue, but is outside of both Plusnet's and BT Openreach's control. People may argue that more should be done, but nobody can be forced to remove their own electrical equipment if they don't want to.
If this line in particular continued to run without Interleaving on, the line would error and would be very vulnerable to poor performance. DLM puts Interleaving on, which add an extra 8ms (shouldn't be a problem) and the line will work fine from there. Perhaps the line experiences irregular amounts of REIN which we're not aware of? Something is causing the errors on the line. Interleaving on Low is enough to correct the amount of errors we've seen on this line, so DLM is happy and takes no further action.
Everybody uses their line for different things, so yes you may see a slightly lower speed when downloading, that's a valid point, but what would you prefer? A fast but unstable line, or would you prefer the full speeds and your connection dropping out when the errors become too much the line.
There are calls for ISP's to have more control over DLM so that we can do more - this, I agree. This isn't being ignored, it's very much being listened to by ISP's across the UK as well as our suppliers and BT Openreach. Discussions have taken place to find out what tools we all would find would be of benefit and things will progress from there.
Resetting DLM all the time for a quick fix, isn't the way forward; this will ultimately send you around in a big loop. It will remove Interleaving and your line will be operating at the maximum speeds the line can take, with errors. Once your line starts to error again, DLM will kick in, your line will be marked down on the Caution Counter and DLM will start to take the measures required to keep your line stable whilst trying to provide good speeds.
With regards to DLM itself; it actually hardly needs to touch that many lines, throughout the UK, it only touches around 2% of all lines. Lines that have never had DLM had to intervene don't get closely monitored by DLM. If your line has, a snapshot of your line is taken once per day and this uploaded through DLM and the DLM (usually around midnight) software will dictate what speed band/Interleaving level, if any is required to keep your line operating at it's optimum. Any changes that are made are made between 3am-5am to keep the impact it has on customers minimal. This will answer the question about why the IP Profile hasn't updated - the sync rate has changed but the data hasn't been collected and the next batch of changes will go through tonight. So if the line remains stable, the IP Profile will be updated when all the data is collected tonight and the change will be implemented between 3am-5am.
It would be great if DLM could update this on the fly, but it doesn't. BT Openreach are reviewing how the current DLM system works and they are aware that it's not most effective as it is, there are plans for this to be reviewed (ongoing). If you have any specific questions surrounding this or want to know more, I'll be writing up a guide soon which explains how FTTC DLM works and it will cover why it does what it does.
We're by no means saying that most issues aren't issues, that's really not the case, but it's absolutely key that we set an expectation of what FTTC DLM is doing and why.
and the plusnet profile was changed(lowered) which i complained about in another thread 
