Sudden change in sync speed?

I have a 21CN line with AAISP. The last month or so it's sat happily sync'd at around 10.8mbps with a 9mbps BRAS.

This morning at around 4.30 the connection reset and is now sync'd at "only" around 9.2mbps with an instant drop in BRAS to 8mbps.

Stats:

ADSL Link Downstream Upstream
Connection Speed 9237 kbps 882 kbps
Line Attenuation 45.5 db 23.0 db
Noise Margin 8.75 db 7.0 db

Off memory, the attenuation is the same as it has always been, but the downstream noise looks wrong and if I leave my router stats page open it's fluctuating between around 8.5 and 9.0 db.

Edited by hutchingsp (Sun 20-Jun-10 11:13:57)

was the noise margin 6 dB before ?

That is a brilliant sync for 45.5db.

Far as I can remember, yes. I tried rebooting the router a couple of times but no change - it's as if it's bricked itself at 4.30am this morning.

Apparently so, but the fact it's dropped to that by 1.5mbps overnight for no good reason is a little odd to say the least.

I think my Netgear is a bit pessimistic on what it reports too - the older Zyxel sync'd slower, but reported 39db attenuation.

Edited by hutchingsp (Sun 20-Jun-10 12:05:22)

In reply to a post by hutchingsp:

for no good reason

As good a description I've seen of the way BT's latest DLM works

On my line it forces a resync every 10-14 days just to see what happens, regardless of the SNR at the time

is it not just an increase in target margin to 9 dB that has dropped the speed ?

I'm afraid that's gone over my head - all I know is my line was stable/at 10.5-10.9mbps for a month then bricked itself at 4.30am and the stats have changed all by themselves.

Why would the target margin increase for no reason or is that another BT joy?

it wouldn't increase the target noise margin for no reason, but DLM may have increased it based on errors or stability. Its definition of stability may not be yours and it may be better at record keeping

I'll see if AAISP can shed any light. I usually keep a pretty close eye on their graphs and the router stats and don't recall seeing anything in the ways of errors - assuming the Netgear reports them.

Funny thing is I wouldn't have complained at that sync but when you feel you've had something taken away from you...