This topic

Broadband restricted speed?

pddco — Mon, 28 Mar 2022 14:22:31 GMT

Hello. I’ve got BT Fibre 2. Had it for years. No issues. Until recently. Up until about a month ago I was consistently getting 75Mbps down and 18 Mbps up. As reported by my Sam Knows Whitebox and an occasional test through MyBT. Now it’s 60Mbps down and 18 up. Not a dramatic decrease but just wondering why? Quiet line test fine. The only thing I can think of is that I’ve just been doing some decorating in the hall and perhaps unplugging the hub probably more than I should. Could it’ve upset DLM - Or whatever it is that monitors the connection. If that’s the case how long must I wait for my normal service to be resumed. I’ve looked at the hub admin and it shows a possible 75Mbps. Can I ask the 150 team to restore it? Realising of course that a refusal often offends. Thanks

Re: Broadband restricted speed?

imjolly — Mon, 28 Mar 2022 15:08:54 GMT

If you have been switching the hub off and on a few times a day for a few days then I expect the DLM to have seen your line as unstable and increased noise margin resulting in drop in connection speed. A stable connection for a few weeks and your noise margin should start to reduce and speed increase

Re: Broadband restricted speed?

pddco — Mon, 28 Mar 2022 15:51:32 GMT

Thanks @imjolly Hmmm, I wonder what it’s metric is. Clearly it doesn’t take years of previous good behaviour, or current line conditions, into account. Or perhaps a 15Mbps cut is quite generous as it’s a first offence. But weeks seems a bit harsh…. Oh well, meanwhile can I see the noise margin figure that’s been set and compare with what it should ideally be?

Re: Broadband restricted speed?

imjolly — Mon, 28 Mar 2022 15:59:48 GMT

You need to go to hub manager the advanced setting then technical log information. The normal noise margin should be about 6db and I expect yours to be higher

Re: Broadband restricted speed?

licquorice — Mon, 28 Mar 2022 16:01:30 GMT

Yes, your hub stats should show the current value and target will be either 6dB or 3dB depending on cabinet type you are connected to.

Re: Broadband restricted speed?

pddco — Mon, 28 Mar 2022 16:14:57 GMT

Well, I had a look and indeed noise margin is up.

Just curious, but if I restart the hub will I it retrain and perhaps reduce the margin? How dynamic is DLM?

Re: Broadband restricted speed?

imjolly — Mon, 28 Mar 2022 16:32:18 GMT

You need a stable connection for noise margin to reduce. Resetting hub will not help and could make matters worse with higher noise margin and lower speed

Re: Broadband restricted speed?

licquorice — Mon, 28 Mar 2022 16:33:46 GMT

Do not be tempted to restart the hub, that will just make things worse.

https://kitz.co.uk/adsl/DLM_system.htm is quite an old description of DLM but gives you an idea of how it works.

Re: Broadband restricted speed?

pddco — Thu, 31 Mar 2022 10:13:47 GMT

Well @licquorice it may not have been me unplugging the hub a few times after all. That all happened over 4 weeks ago. And today I’ve noticed the noise margin has actually increased. My download speed has reduced to 52 Mbps (from 75 originally). I had to do the 17070 quiet line just to check again (from the test socket) But there’s no obvious crackling / noise. Looking at the logs after about 9 days of DSL uptime the hub had a soft restart around 1 am. Anyway. I’ve raised a fault but seems odd. Like I say, I’ve had years of stable 75/19Mbps but over the past month or so it’s gradually got worse.

Re: Broadband restricted speed?

imjolly — Thu, 31 Mar 2022 11:21:51 GMT

your connection speed is 67mb just as it was when you previously posted hub stats so the recent drop in connection has not change that but your noise margin has increased slightly. download speed can fluctuate and is not guaranteed

Re: Broadband restricted speed?

pddco — Thu, 31 Mar 2022 12:20:39 GMT

Granted that Download speed can fluctuate. But I’m only getting 52Mbps on a connection that I’m told should expect to see somewhere between 63 to 76Mbps. And it’s been 75Mbps for years previously. That little SamKnows box is quite handy in that respect . Something’s changed. It’s not the end of the world but I’m curious.

And another thing, that’s odd. When I disconnected the line to do the quiet line test and reconnected, the hub connected again no problem, but the speeds via WiFi were rubbish. Like 3Mbps. It took a soft restart of the hub to get them back up to the dsl speeds. Perhaps that firmware update in February didn’t help.

Re: Broadband restricted speed?

licquorice — Thu, 31 Mar 2022 12:29:18 GMT

The speeds you are told to expect are sync speeds not download speeds and you are currently getting 67M.

However, at some point DLM has taken umbrage and has banded your line at that speed. It can take several weeks for DLM to release it.

Re: Broadband restricted speed?

imjolly — Thu, 31 Mar 2022 12:31:40 GMT

the 2 restarts are not helping your line improve as you need a stable connection with no manual resets

Re: Broadband restricted speed?

pddco — Wed, 27 Apr 2022 07:02:38 GMT

Got it sorted. Have to say it all went rather well. Reported the problem. BT said there may be an issue. Openreach engineer came out when he said he would. He was rather puzzled as to why it should have dropped suddenly. And things tested okay - no errors. But he replaced the screw terminals in the box in the hall coming in from the UG feed, with tool-less ones. And redid the jumpers in the cabinet. And now all seems to be fine. Noise margin at 6.3dB and 73/19Mbps speeds.