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[Mick]

Hi All,

After a  couple of months with a stable 7616 sync speed I have had two retraining events and lower sync speeds/IP Profile over the last 4 days.  I thought that the first one was a coincidence, but now I noticed a second occurence.  I resync'ed at around 6.7Mbps which is quite a drop.  Both retraining events happened around 10:30 to 11:00 at night.  No known noise sources at that time of the night.  No audible noise on the line when the last resync occured.

I am thinking that this could be because the nights are drawing in and atmosperic conditions are changing too.  Have you noticed anything similar before I start replacing filters all around?

(PS. The router log shows LOS due to high error count).

[kitz]

High error count is normally an early warning before loss of sync and normally occur when the SNR starts to drop.

It could be burst noise at a particular time or it could gradually build up.   Have you tried monitoring your SNR with routerstats to see whats happening?

[Mick]

Thanks Kitz,

I have a rather convoluted set up of gear and have not yet set up anything to monitor the modem.  I have a longer term goal of setting up mrtg, but I have found it somewhat difficult because the modem only has http/s access (no SNMP or telnet) and my perl skills are non-existent.  However, I kept an eye on the SNRM and from six o'clock in the evening starts to gradually reduce.  By nine it is down to 1-2.  It usually holds onto that (it has been for a couple of months) but twice so far I had a resync.  This is why I am thinking that winter is around the corner.   

[kitz]

Sorry mick - refresh my memory which router?

[Mick]

Hmm, strange.  I didn't get a notification that this thread got a response.

I am running a 2WIRE 1800HG as a modem (same hardware like the early 2700HG routers) in a fully bridged mode.  The drop outs are now normal occurence every night.  The retraining will happen due to the number/rate of errors increasing beyond what the exchange considers normal/acceptable.  The resync under such conditions will of course be lower and this has dropped my IP profile down to 5500. 

A resync in the morning (when I discover that the line was dropped again) invariably gets me 7616kbps, but unless I can hold onto it continuously my IP profile won't increase.  From what I have observed the noise margin is dropping gradually throughout the night and the error counts have increased significantly (from an average of 9-11 per second to 28 per second).

[kitz]

I'm not sure what your current target SNR is set at on the DLM, but I wouldnt be too surprised if at some point the DLM decides to increase it if these drops become a regular occurance.  This will then have an impact on the maximum speed at which you can sync at. :/

Depending on your current target SNR it could be that that a "little extra" noise is just too much for the router to cope with and it does drop where previously it was able to hang on by the skin of its teeth.  Depends how much extra it is..  it is possible that a tiny bit may be due to weather/atmospheric conditions.  But its also possible that it could be something like lighting (street or neighbour) etc.. or even the very start of a line fault.  :/

[Mick]

Thankfully it's still at 6dB.

I managed to get a couple of traces (ignore the scale - I haven't managed to get that right yet . . .) 

The sync speed graph shows 7520 in green (the speed at which I initially sync'ed with the exchange) and in blue the current speed that I would sync at.

The SNRM graph starts at 6 dB, then drops down to 5dB at 20:00h, 4dB at 21:00h, comes back up to 6db at 5:30 in the morning and finally reaches 7dB at 6 o'clock in the morning.  No idea what time the street lights come on or if indeed this performance is related to them, but there's nothing else happening at home that I can think of which could have this impact.

EDIT:  Oops, forgot the snrm graph - now added.

[attachment deleted by admin]

[roseway]

That's a perfectly normal nighttime variation in noise margin.

[Mick]

After a rather unstable week I am back to holding onto a 6500 IP Profile for more than 8 days now.  I have sync'ed at 7520 (green trace on the graph) when the SNRM was a bit lower than 6dB and left it there, hopefully to give it some more tolerance.

I am not sure what caused the 4-5 days of low SNRM/resync's (did we have any solar storms perhaps?!)

The error counts almost double what I was getting in the middle of the summer.  I think that it is a matter of a marginal connection (long line) and longer nights.  Better get used to it. 

I also got hold of a Speedtouch 585v6, but it is locked onto AOL and I am not sure how I can place it in a fully bridged mode (which I need for my set up).  When I have some time to play around with the CLI I will see if it gives me any better performance.