BT profiles (again)

[esh]

Hi guys,

Sorry to bother you again.
Had a fab 4 months or so at 8Mbit with idnet, but noticed over the past month I'm shoved back on a 6500 profile instead of the previous 8000. Could this be due to a severe bout of brownouts (power 'flickers') over the past week or two? Electricity is so bad here we absolutely have to have everything on UPS devices but I guess something might have given way. I think there was one reset of the network services due to BT maintenance but nothing to suggest to me that a degradation was required to maintain line stability.

I'm sure this has come up before, but I'm just really asking:
a) Is power flickers in the area the likely culprit, despite my devices being on UPS terminals?
b) Any advice? 6500 isn't slow, so shall I leave things be?

Cheers.

[Sebby]

The fact you've got a UPS means that the router should receive a continuous level of power, so I wouldn't have thought that would do it, though of course it could.

Could you post your router stats? I'd like to see what sync and SNRM looks like.

[esh]

G.DMT/Interleave, trellis off
ES=9, SES=0, UAS=27
SNR Margin (dB): 9.8 D / 14. 0 U
Attenuation (dB): 27.0 D / 16.0 U
Output Power (dBm): 11.9 D / 19.7 U
Attainable Rate (Kbps): 9344 D / 1180 U
Rate (Kbps): 7616 D / 832 U
Super frame errors: 14/4592891 D / 38/4592889 U
Interleaver depth: 16 D / 2 U
RS Uncorrectable errors: 204
HEC errors: 12
No OCD/LCD/ES errors

[Sebby]

Ah, interleaving has been enabled on your line, which obviously wasn't enabled previously. The maximum sync for an interleaved line is 7616k (although, to confuse matters, some exchanges allow sync of 8096k). I believe that with 8096k sync you get a 7000k profile and a 6500k profile with 7616k sync. So that explains your new profile.

Have a word with IDNet and see what they think, as it's possible to have interleaving disabled again, which would almost certainly bring your sync back up to 8128k (you have enough margin), giving you a profile of 7150k. The issue is that if errors are high, it can impact throughput (as packets have to be re-sent), but assuming the cause of interleaving being enabled was temporary/a one-off, you should be okay. Ultimately, you've got nothing to lose as it can always be enabled again if need be.

[esh]

Okay thanks, I did wonder about that. Can't explain why interleaving might have got turned on. The network services are up 24/7, and only one hard reset of the router required in 5-6 months. Fairly odd. I'll drop them a line and see what's going on, but I imagine it's BT as usual.

Many thanks again!

[Sebby]

Interleaving would be switched on due to high errors, which is a bit different to having your target SNRM pushed up (more to do with instability).

[esh]

Oh dear I have a horrid suspicion that I might have caused some errors a while back. It turned out that my router, despite not being cheap, is rather old and is completely incompatible with gigabit. When I plugged in a gigabit system, it could send packets but not receive, and then the MAC tables proceeded to go haywire until I removed the system again. I spent a long time trying to solve that one, until I just plugged the system into another switch and it ran perfectly.

Not that that should have any effect on the DSL line, but my trust in the router was slightly eroded after that fiasco.

I've fired off a query all the same. Really must cough up the funds to replace that router, I did the switches a couple months ago.

[Sebby]

I wouldn't have thought that would cause it, but as always with computers, anything's possible.

IDNet should get this sorted for you.

[esh]

IDNet replied to me this morning and offered to request the interleaving to be removed which I agreed to. The router went down a couple hours ago, I assume this was related, so I brought it back up but everything is the same. Hmm.

IDNet did say it would take 24 hours but I have to wonder if anything happened at all here.

[Rik]

I do know that BT have been kicking the tyres round here, Esh, so the same may have happened to you (I gained 300k in the process, so I'm not complaining ).

[Sebby]

It could just be coincidence that the router lost sync, esh.

[esh]

Must have been. Either that or BT running tests as they like to

Back on G.DMT/Fast now with 8k sync rate. Same router stats as before, so all is well.

Thanks all! (and IDNet!)

[Rik]

Phew.

[Sebby]

Back on G.DMT/Fast now with 8k sync rate. Same router stats as before, so all is well.

Good news.