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Author Topic: Old fashioned ADSL possible DLM whinge  (Read 503 times)

Weaver

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Old fashioned ADSL possible DLM whinge
« on: May 28, 2018, 04:35:40 PM »

Mrs Weaver accidentally pulled the mains out of my modem this morning, as mentioned in another thread. ( I may have mistakenly said it was the phone line getting pulled out.) Then I lost ~120 kbps downstream, now around ~2.9 Mbps downstream sync rate on line cwcc@a.1 which is a ZyXEL VMG 1312-B10A ADSL2 BT 21CN. And it has remained ‘lost’, despite all my efforts, including trying a target SNR margin reset, I can't get it back.

Assuming this is BT DLM at work, any idea how long before I am forgiven by DLM (21CN) ? Am I correct in my understanding of this, that DLM might sulk and decrease the speed across multiple resyncs because of a power cut?
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ejs

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Re: Old fashioned ADSL possible DLM whinge
« Reply #1 on: May 28, 2018, 06:50:20 PM »

Not DLM. Maybe due to slightly different positioning of the power cable?
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re0

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Re: Old fashioned ADSL possible DLM whinge
« Reply #2 on: May 29, 2018, 02:05:09 AM »

I was just thinking about 120 kbps not being a big deal, but for your connection that's about 4%.

I agree with ejs in reference to the DLM... I do not think this is at play. The difference is too insignificant and small variances in background noise would be my guess. Maybe you had some bolts in the sky around that time? ;)
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aesmith

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Re: Old fashioned ADSL possible DLM whinge
« Reply #3 on: May 30, 2018, 04:57:22 PM »

My experience is that it would take more than one disconnection for DLM to kick in.  When I've had high errors or disconnections it's only acted after a couple of days, then every two days from that point onwards.   What's the actual noise margin reported ("Synch Status" on the A&A control page)?   Just wondering if you have variable conditions around the day, and the disconnection (or rather reconnection) happened at an unfortunate time.
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Weaver

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Re: Old fashioned ADSL possible DLM whinge
« Reply #4 on: May 31, 2018, 03:50:46 PM »

The actual current downstream sync rate is 3.1 dB and the target is 3 dB. The modems have been resynched several time since, but no joy.

I am starting to think that perhaps Mrs Weaver has put the AC mains right next to the modems or next to their DC leads. If so that would explain the sudden onset when this had never happened before, and the fact that it won't go away.

Also the old modems had dc blocks with ferrites fitted onto their 12V DC leads but the new modems do not as yet have them, so not a level playing field, if the ferrites even do any good that is.
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