Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length

[broadstairs]

Around 12:30 yesterday, just after we had gone out till around 18:00, my line went berserk with snrm dropping to silly negative levels (nearly -2) and DLM intervening as well with some silly speed negotiations giving 403kbps upstream and less than 40000kbps down. DLM intervened several times yesterday and once again this morning around 7:30 which has put me back approximately to where I was before.

My problem is trying to determine what happened as we were not here when it all kicked off. I checked the phone which does cause snrm drops but there were no calls during the afternoon when it was going really crazy. Something must have happened but I dont know what. I checked on possible thunderstorms but the nearest were 50+ miles away and besides we have had them recently almost overhead and had nowhere near this kind of grief. There are no obvious signs of roadworks near here or the cabinet (about 300yards away). This morning it seems to have calmed down.

By the way I did check the other day to see what happens if the line is called with all internal wiring to the master socket disconnected and the snrm does indeed drop although not as much as when the phone is connected and nowhere near the drop yesterday.

Long shot but any suggestions?

Stuart

[WWWombat]

I just wandered through some of the MDWS graphs.

I note that your attenuation increased in a couple of steps, while your SNRM decreased crazily. Rather like @daveesh1's line, in this thread going on at present.

Your Hlog graph also shows some glitches at different times; Using the "Historic" option, compare the one on "24th May 00:00" (smooth) with the one on "23rd May 18:00". It isn't as dramatic as @daveesh1's, but it does seem to indicate a physical problem with the line that triggers intermittently.

[broadstairs]

Just had another hit by DLM when it came back my upstream speed has dropped to 788kbps with downtream being just over 41000kbps and snrms being both around 5db.

Stuart

Just raised a thread on the TT forums about this but I wont hold my breath....

[WWWombat]

Just had another hit by DLM when it came back my upstream speed has dropped to 788kbps with downtream being just over 41000kbps and snrms being both around 5db.

DLM isn't doing anything. You are staying at INP=3, delay=8 all the way through this.

Your attenuation just increased again, and your Hlog has gone funny. The resulting changes to SNRM is what is causing your speeds to drop.

That change to the upstream speed is pretty extreme, and I haven't figured exactly why. However, when things happened yesterday, you can see the outcome in the "bits/tone" graph. Using the "Historic" setting again, you can compare the tones used for upstream at 1pm, 2pm and 3pm yesterday ... as I've added to this post.

[broadstairs]

So what is causing the resyncs then if not DLM trying to stabilise the line?

Stuart

Just checked DSLStats and the SNRM upstream is going up and down like the proverbial person of the night's undergarments!

[WWWombat]

The regular behaviour of a DSL modem. It is the normal behaviour of DSL to trigger a resync to stabilise the line too.

A resync will happen if SNRM goes out of bounds; while we don't know what the bounds are, the values are defined as part of the line profile. It wouldn't be a surprise if the threshold was set to 0dB.

A resync will also occur if one ends loses track of the framing data that surrounds the user-data. If the modem loses confidence that it can even work out where the start and end of the user data lies in the bitstream, it will give up and force a resync.

When lines are being problematic, these types of resync are *much* more likely than a DLM intervention. Oh, somewhere in amongst the sequence of resyncs, you might *also* see a DLM-induced resync - as it tries to stop all the other ones from happening. I don't think your line has seen one yet - you would see INP/delay value changes.

People have a habit of looking at the resync reason code, seeing a value of 1, and assuming it means DLM. Unfortunately, it really signifies "RDI", or "remote defect indicator" ... which tells you that the DSLAM didn't like the bitstream it was receiving from you.

[broadstairs]

Thanks for the explanation, you you are right some of the indications can be a trifle misleading initially.

Stuart

[daveesh1]

Least I am not the only one with crazy going things going on.

[WWWombat]

Just checked DSLStats and the SNRM upstream is going up and down like the proverbial person of the night's undergarments!

Its still doing it.

Do you hear any audible noise on the line at all?

I think it is worth doing the same step as @daveesh1 - get onto support, to log a fault. Doing so while it is happening is probably worthwhile too.

[Chrysalis]

wow the line looks whacked, I checked the snrm per tone graph and there is almost nothing there on the US channels, and the line is still hanging on with sub 4db snrm on both up/down right now.  Get an engineer sharpish.

I think the extremely low US speed alone will get openreach's attention.

Also ask your isp to do a GEA test, if the rules havent changed then your line should fail due to a loss of speed of over 25% in one go.

[broadstairs]

I have opened a thread with their Community forum, I just dont want to call their support as it is usually useless.

Stuart

[burakkucat]

I have recently made a post in daveesh1's thread . . .

Series capacitive effect, maybe? 

b*cat wonders what WWWombat thinks?

[broadstairs]

I just read your post b*cat, possible although our road is comparatively quiet so not much traffic to shake it, however it is a good catch and certainly will keep it in mind. As yet no response from TT community ...

Stuart

[burakkucat]

I wonder if both daveesh1 and yourself have unmodified, newish, pole-top "coffins" . . .

[broadstairs]

Not sure - how would I tell since I can see the pole top from the window infront of me here at my desk. On this side I can see 3 boxes, on looks like about 10-12 inches long, not able to see width clearly from here. One about6inches by 3 inches and a smaller one which might be 3 inches square. The other pole is across the raod, not sure which one is the master of the two as I need to go take a look outside later.

Stuart