BT DLM nightmare

After over 6 days online with no disconnections i reboot the router and BTs DLM decides its going to raise my snr from 9 to 12 for no apparent reason, I have been told by my ISP i now have to wait 72 hours for it to be reset
This is a joke

Edited by deleted (Tue 18-Jan-11 10:58:01)

Single resync should not do that, possibly you were not seeing lots of other resyncs, or the number of errors that the error correction was masking was very high.

In reply to a post by MrSaffron:

or the number of errors that the error correction was masking was very high.

That's one of my beefs with the DLM- if an "error" is correctable and corrected, it's not really an error is it?

Certainly hard errors should be taken into account in determining the target SNRM, but I don't see why corrected ones should.

ISp said my line had been up for a good 6 and a half days before my resync
10697 crc in that time

In reply to a post by iwish:

10697 crc in that time

I can't remember what my CRC error rate was when I was on ADSL, but that sounds rather high... though I'm quite prepared to be contradicted!

The masking can often mean, not a corrected packet, but a retransmit of a data cell, thus reducing your actual bandwidth.

The ISP has it wrong. If you'd suffered an IP profile change then that might get corrected in 3 days but a change in noise margin will take at least 14 (unless things have altered from when I was on ADSL).

High error counts and noise margins are more often problems with the internal wiring than the line itself. Have you read any of the guides on ring wire removal/isolation?

Unless they've requested a reset, and are saying three days to allow system to kick in.

Anyway IP Profile is upto five days

In reply to a post by MrSaffron:

The masking can often mean, not a corrected packet, but a retransmit of a data cell, thus reducing your actual bandwidth.

I'd count that as a "hard" error... perhaps I should have qualified what I said with "assuming interleave is on" so that there's a better chance that an error can be corrected locally and not require a re-transmit.

In reply to a post by iwish:

10697 crc in that time

I can't remember what my CRC error rate was when I was on ADSL, but that sounds rather high... though I'm quite prepared to be contradicted!

It's possible to get rather higher and still have a usable link.

I have a long line - attenuation approx 62dB but relatively stable noise levels so I force the connect SNRM down from its 9dB default to around 3dB (probably drops to 2dB or just under at its worst point in the day). However that does produce some frightening figures.

Current uptime just over a month (2835457 secs) ES: 55687, SES: 1888; HEC errors: 151046

Generally 3-5% of packets need error correction, about 0.01%-0.05% are uncorrectable but TBH the wider Internet probably looses more than this.

I'm afraid my philosophy is rather that if you're getting few errors then FEC is a waste of bandwidth and I don't really have it to waste (sync ~3600Kbps even @ 3dB SNRM). I do realise that I' failrly lucky in having a line with a stable noise profile so that playing this sort of game is feasible.