DLM reset request (ADSL2+)

[#1]

TM: fairly sure I have already posted this but attenuation has always been c.15 which I reckon is too high.

On boot on Wednesday it was 15/16, after midnight it was 16, yesterday it was 17 and is now 17.5.

[#2]

I will raise a ticket on Monday.

[#3]

---

@Mardler wrote:

TM: fairly sure I have already posted this but attenuation has always been c.15 which I reckon is too high.

On boot on Wednesday it was 15/16, after midnight it was 16, yesterday it was 17 and is now 17.5.

---

That figure should be a constant - so you have a problem.

[#4]

Attenuation is what it is. It’s a characteristic of the line length and short of moving home closer to the exchange, it is not changeable.

That said some routers measure it slightly differently and it can be skewed by the number of bit buckets in use. The better the line, the more bit buckets available. Therefore sometimes there can be slight variations due to bad joints.

That attenuation confirms the line length to be circa 1.1km and should deliver 22mbps with a SNRM of 6dB. See https://kitz.co.uk/adsl/max_speed_calc.php

NB: this is a switching from ADSL to ADSL2 service and the attenuation (a factor of the number of available bit buckets) is measured differently between the two. For a fair estimate take 2 off the ADSL2 attenuation figure.

If you are getting significantly below 22mbps without the router being gamed, then there is probably a fault.

[#5]

Thanks, John. I agree.

Just for info (mainly for PN when ticket is raised, everyone else must be bored stiff!) I have just set the router to Auto which turns off tweaking.

Interestingly, this instantly changed a couple of stats, new figs first (previous in brackets, target SNRM = 4):-

Reported SNRM = 9 (9)

Attenuation = 17 (17.5) - down 0.5

Sync = 12079 (10803) - up a bit but still way too low not helped by the highish SNR.

[#6]

Great, now we can get a clear view on the issue.  Please leave the router well alone now, no more reboots.

If we determine that ADSL2 attenuation of 17dB would be 15dB for ADSL(1) then that suggests a line length of 1.1km and an expected sync of 22mbps.  Only a 2dB difference would be pessimistic so in ideal conditions you ought to be doing better.

The 9dB SNRM is a characteristic of the line quality; it is a symptom of the slower sync speed, not the cause.  The cause is the line fault.

Is the reported SNRM the same as the negotiated SNRM during the initial connection?  Many routers record the initial SNRM in the log file.  If there was noise on the line at the time of the connection negotiation, the current SNRM could be higher than that on first connection.

That considered, if optimistically a 3dB change in SNRM might deliver a 4mbps difference, you would only be seeing 16mbps which is way lower than than that which might be expected from your reported line attenuation.  Does the Billion router detail the tone bin utilisation?

[#7]

Yes, TM, I am aware of all of that. 

Yesterday I ran 2 checks. The upshot is that the attenuation suggests to the models that we're c.1.25+km from the exchange. According to Openreach the line is 0.7km.

Anyway, all tweaking is now off and will remain so for 48hrs after which I will try one more time to use my normal setting (used for 3+ years nigh faultlessly) to see if it reverts to Wednesdays excellent connection if not tweaking will be switched off and after another 48hrs of DLM settling I will raise the ticket..

[#8]

TM, so far as I can see the SNRM isn't logged during the reconnect process however the sync rate is and that's the same as now reported so the SNRM can reasonably be deduced to also be the same.

There's no tone bin data available.

It will be interesting to see how stable the line is now.

Next report Monday.

[#9]

Curiouser and curiouser.

As planned, I tried an SNR tweak. Attn 17.5; sync 13139.

Immediate disconnect.

Reset SNR to Auto i.e. handoff to exchange dlm. Attn 17.5; sync 18839!

Immediate disconnect.

Automatic reconnect. Attn 16; sync 19167.

Almost immediate disconnect. Reconnected at similar sync.

Flummoxed.

Have to go out: will the dlm settle?

[#10]

A PN staffer is kindly looking into this.

[#11]

Several disconnects from dusk and a slow return to the bad connection: Attn: 17.5, sync 10191.

PN have been asked to escalate from Thursday latest.

[#12]

TBH this is exact what you need - lots of disconnections. That drives the issues register metrics.

[#13]

Indeed, TM.

[#14]

Another exchange disconnect.

ADSL2+ reconnected. Two minutes later the Internet disappeared but connection still up. That's still the case!

PN please sort this asap!

Sent via phone data usage.

[#15]

Disconnect at 11:45 was PN resetting DLM. 

Router rebooted: DSL up, internet down.

Message via phone data usage.