Losing sync & jumpy noise margin = dodgy router?

InQ · 20 Dec 2009 at 22:35

Sorry for the long post, i just wanted to get in as much info as possible.

ops:

Up until a about 6 weeks ago i was on a 7150 BRAS profile and had been for a few years with no real problems.
Then this last couple of days my router (3COM Officeconnect) has been dropping sync at least once every hour, usually a couple of times though.
Resync had been coming in at 7000-8000 region, i had been on a 8128 sync for the last couple of years whenever i'd checked it.
I checked my Zen user profile and can see the connections/BRAS profile has started to steadily reduce from 7150 to 5000 over the past 6 weeks or so:-

At the sync i'm at now, 6208/BRAS 5000, i have not dropped sync in 9 hours, seems to be better and happy for now but at a lower speed.

Watching my router stats i noticed at one point my noise margin dropped by 7db in a flash (12db -> 5db) and then rose up to 9/10db...it has been around the 9-12db all night whenever i've looked at it. Note my downstream and upstream attenuation are reported the wrong way round on the router.
From 12db noise margin to:-

Then about 30 seconds later it was:-

I found an old post of my router stats and at sync of 8128 i had a noise margin of 3db, this has obviously been fine for me for so long, its been solid since 2007!
So, i've tested a replacement microfilter in the test port (i have an ADSL nation filtered face plate normally and a ADSLnation "PRO" low loss ADSL cable), a different ADSL cable and had my phone wiring disconnected and it was still dropping sync, no change. So only thing i havent changed is the router, other than that i can only expect it to by a BT issue.

Does this sound like a failing router in that it doesnt seem to want to hold sync at the lower noise margin it once did and this seems to be getting slowly worse looking at my stats?
Or would you guess at a BT line/equipment fault?

I've bought a 2nd hand Draytek Vigor 2800G from ebay to see if thats any better (hopefully deliver this side of xmas) and i may give my ISP, Zen, a phone tomorrow morn to ask if there is any known issues with my exchange and if they can do a line check...the couple of times i've used them in the past they've been total class.

InQ · 22 Dec 2009 at 00:18

I've read if you have an obvious noise issue ie you can hear it! then just log the fault with BT as a noise on the line issue and dont mention broadband...hopefully fixing your noise issue will sort the ADSL.
I assume however you have done all the obvious things eg. different filter, line to your router, disconnected your phone connections, tested it from the test socket.

I've managed to get Routerstats to plot my noise margin and sync rate over time, i have had instances in the space of 20 seconds were it drops from 13db to 4db...router not dropped though but i'm only conencted at 6240kbps currently. I think my target SNR is 9db as this is what i understand from my Zen profile page, it says i've had a "noise margin reset" this last day or so, i think the standard margin is 6db so i guess its now 9db due to the reset.

From tonight over approx 1 hour, stats taken at 10 second intervals:-

InQ · 22 Dec 2009 at 11:05

Is mine normal though or not, it doesnt look as bad as yours was? I know it gets worse at night when the street lights are on, thats normal.

This is from this morning although my router hasnt dropped in 14 hours:-

The 2 big drops arent exactly an hour apart which if they were would have suggested something was causing interference every hour, the previous one was about an hour before the ~9.36am drop however but before that there was no nearly hourly drop...i had a few within 10 minutes of each other to 5db.

The only thing i'm yet to try is another router, awaiting the Draytek to turn up.
I'll give Zen a ring, see if there is any known problems or if they can do a line test to see if anything shows up.

InQ · 22 Dec 2009 at 12:50

Well my first post shows my BRAS profile has been in a steady downward spiral since late November, the (LED) Xmas lights have been unplugged and i still got disconnected plus the above Routerstats i ran overnight since yesterday are with them off (they were only put up a week ago anyway).
The router is on top of my SkyHD box surrounded by my TV, amp, DVD player and PS3...its been that way for 2 years with no issues. I did move it away when i was testing it with a 1m extension cable and had this into the test socket with another filter (i have an ADSLnation filtered faceplate normally, best you can use) but i still got disconnected.
My house is detached and the nearest neighbours house is about 15m away from the router position through 2-3 walls.
The only new electrical items have been the xmas lights (my BRAS profile was dropping way before these were put up) and a new toaster which isnt in use 99% of the time.
Before i monitored it with Routerstats my own routers log stated it had dropped about 5 times through the night the other day.

InQ · 22 Dec 2009 at 14:18

Been on the phone to Zen and seems they cant pinpoint any particular fault yet but suggested i try another filter and just the ADSL line connected (i had already tried this).

Result after a number of minutes already looks "normal" (i'm set to a 9db margin due to the drops over the past 3 weeks):-

This is turning me into a liar! :rolleyes:

So if this stays as it is that means its either the ADSLnation faceplate filter or one of/both the phone lines or maybe even the splitter the phone lines are plugged into which then plugs in the phone socket on the filter at fault.....feels like i'm getting somewhere now.

InQ · 22 Dec 2009 at 18:03

Well the better performance didnt last, disconnected after 1 1/2 hours and reconnected at a lower speed and the see-saw nosie margin was back right away:-

Dropped again about an hour after this and reconnected a few 100 kbits lower.
(Note; this is in the test socket with another microfilter and no phone lines plugged in, just the ADSL).

1) make sure you got no extension line connected to your master socket

Yep as shown above.

2)change micro filter

Yep done as above (ADSLNation faceplate filter -> ADSLNation XF-1e Microfilter).

3)try use 3rd party firmware router (what router you got?)

Dont think there is any out for mine, its a 3COM Officeconnect model 3CRWDR100A-72. Its running the latest firmware and has been fine for 2 years.

4) change to different make/model router

Yep its the only part of my side of things i havent changed as i havent got another router.....although i have a 2nd hand Draytek Vigor 2800G on its way.

5) change phone line between router and test socket)

Tried this also plus the router plugged in a different power socket....still dropped within 20 minutes (or so).

6) unplug everything and plug in telephone and do the 'noise test', i cant remember which number to press for this test.

Cant hear any noise on the line for voice but i will look into this.

InQ · 23 Dec 2009 at 10:34

http://www.theregister.co.uk/2007/10/22/zen_ar7_infineon_bt_fault/

Interesting, my 3COM uses the same chip.....

InQ · 23 Dec 2009 at 14:53

Got the Draytek and trying it as we speak....pretty flat 9.5-10.5db nosie margin on a 6496 connection atm. Will report back as we head into the evening and the noise rises, see if it drops or i get the big noise swings....

InQ · 23 Dec 2009 at 20:21

OK looking good <touch wood>

Over 4 hours its been between 10.5db and 8.5db the whole time, my profile is set at 9db on the DSLAM.
(IGNORE THE DIP AS IT WAS ME MESSING WITH ROUTERSTATS!)

No major seesaw on the noise margin and no big dips (like 9db!!)...yet....

So assuming i dont incur anymore problems the fault led with the 3COM router..although i did read one instance of a faulty 3COM PSU causing noise on someones 3COM router but i dont have another to try this out and i aint paying £5-10 just to see!!

The Draytek isnt as intuitive as the 3COM, i have found a telnet command to access more line data;

LocalSNRMargin= 9.5 dB
LocalLineAttn= 30.5 dB
LocalTxPower= 12.1 dB
LocalInterleavedChannelRxRate= 6496000
LocalInterleavedChannelTxRate= 448000
LocalInterleavedChannelFEC= 28909
LocalInterleavedChannelCRC= 4
LocalInterleavedChannelHEC= 1
LocalInterleavedChannelNCD= 0
LocalInterleavedChannelOCD= 0
RemoteLineAttn= 17.0 dB
RemoteSNRMargin= 25 dB

So correct me if i'm wrong but thats showing;
Attenuation Downstream = 30.5db
Attenuation Upstream = 17.0db
Noise Margin Downstream = 9.5db (varying)
Noise Margin Upstream = 25db

This compares to my 3COM reporting;
Attenuation Downstream = 33db
Attenuation Upstream = 38db*
Noise Margin Downstream = 10db (varying...a lot!)
Noise Margin Upstream = 25db

* This should be lower than the downstream but it had always been reported like this, even on another (but exactly the same model) router. Maybe it should have been 18db? Someone in the past suggested maybe the Attenuation db figures were the reported the wrong way round (38db down, 33db up) but i think my previous long term sync of 8128kbps would prove this unlikely? Seems like the 30.5db of the Draytek is pretty good though, should get 8128kbps sync back once my profile resets to a 6db target?

InQ · 23 Dec 2009 at 22:25

Well it dropped....

Although slightly odd, my noise margin went to 100db?

Wed 23 Dec 2009 21:27:45 Rx-Noise=9.5 Rx-Sync=6496000
Wed 23 Dec 2009 21:27:55 Rx-Noise=9.5 Rx-Sync=6496000
Wed 23 Dec 2009 21:28:05 Rx-Noise=6.5 Rx-Sync=6496000
Wed 23 Dec 2009 21:28:15 Rx-Noise=9.5 Rx-Sync=6496000
Wed 23 Dec 2009 21:28:25 Rx-Noise=9 Rx-Sync=6496000
Wed 23 Dec 2009 21:28:35 Rx-Noise=9 Rx-Sync=6496000
Wed 23 Dec 2009 21:28:45 Rx-Noise=9 Rx-Sync=6496000
Wed 23 Dec 2009 21:28:55 Rx-Noise=7 Rx-Sync=6496000
Wed 23 Dec 2009 21:29:05 Rx-Noise=6 Rx-Sync=6496000
Wed 23 Dec 2009 21:29:15 Rx-Noise=6.5 Rx-Sync=6496000
Wed 23 Dec 2009 21:29:25 Rx-Noise=100 Rx-Sync=
Wed 23 Dec 2009 21:29:35 Rx-Noise=100 Rx-Sync=
Wed 23 Dec 2009 21:29:45 Rx-Noise=0 Rx-Sync=30.5
Wed 23 Dec 2009 21:29:55 Rx-Noise=0 Rx-Sync=30.5
Wed 23 Dec 2009 21:30:05 Rx-Noise=0 Rx-Sync=30.5
Wed 23 Dec 2009 21:30:15 Rx-Noise=13.5 Rx-Sync=5312000
Wed 23 Dec 2009 21:30:25 Rx-Noise=14 Rx-Sync=5312000
Wed 23 Dec 2009 21:30:35 Rx-Noise=14 Rx-Sync=5312000
Wed 23 Dec 2009 21:30:45 Rx-Noise=14 Rx-Sync=5312000
Wed 23 Dec 2009 21:30:55 Rx-Noise=14 Rx-Sync=5312000
Wed 23 Dec 2009 21:31:05 Rx-Noise=14 Rx-Sync=5312000

InQ · 24 Dec 2009 at 01:48

Dropped again.....BRAS profile reduced again to 4500. :mad:

This with a different; router (Draytek), ADSL cable, filter, no internal wiring connected and plugged in the test port plus the router PSU plugged into a different socekt and a different ethernet cable connecting me to the PC (i'm normally connected to the router via homeplugs).

Really starting to be sure it cant be me causing the problems.

InQ · 24 Dec 2009 at 08:17

Well thats what it reported, maybe it reports negative SNR as 100db?

Current 5mbit sync seems to be stable atm.
Cant hear anything on the line, listened on a number of occasions.

Although check this out from this morning, a dip every 1 hour 8 minutes:-

InQ · 24 Dec 2009 at 12:35

Anyone know what the hell this is all about, sync dropping to 448kbps (same as upstream rate) then going back up but the connection to my ISP doesnt drop?

InQ · 28 Dec 2009 at 10:08

Well it seems i can keep a connection, just needs to be lower sync speed so the noise margin is bumped up so high the nightly blips dont affect it. I'm now using a Netgear DG834GT on the line and last night i ran it without any phones connected, straight into the test socket with a different filter and a different ADSL lead and with the router plugged into a different power socket than normal. I also unplugged a lot of stuff like TV's, Sky boxes, amps, powered sub etc around the house and no change.

Ignore the blip at ~22:50 hours, it was me causing the router to not reply, i did get a re-sync early on with a steady nosie margin all of a sudden it just dipped and disconnected.

Netgear overnight results

Guess i'm going to have to get onto Zen to get them to investigate it further.

Also i did a quiet line test (17070 option 2) and i was doing it when a blip occured, didnt hear any noise on the line however (phones are cordless though).

InQ · 28 Dec 2009 at 10:49

Morning Wesley,

I took my 3COM router to my parents house yesterday and set that going, they are on the same exchange as me (as well as with Zen) and a couple of hundred yards up the same road nearer the exchange.
Results were fine, usual up down the 3COM seems to give but it didnt drop even though the SNR margin was pretty low at some points:-

(the red sync line blip again wasnt a drop)

http://www.duckworth.myzen.co.uk/router/mumdad

One of my brothers shut the PC down though later on even though i told them not to.... :rolleyes:

The actual LOG file though goes to 23:30 and its no different to the above graphs, no drops similar and SNR margin.

InQ · 28 Dec 2009 at 11:39

Well its only happening at night when there is more noise in general on the phone lines, maybe the DSLAM is going dicky, cant hold the SNR margin properly? It doesnt happen during the day so leads me to think its not a dodgy connection somewhere? But then again what do i know.. lol
I've tried the following and some in combination and mostly in the test socket with any other phones/Sky boxes not connected;

3 routers - 3COM Officeconnect, Draytek Vigor 2800, Netgear DG834GT
4 ADSL filters - ADSLNation faceplate, ADSLNation XF-1e filter, BT MF50, some other i dont recall.
4 ADSL phone lines - ADSLnation "PRO" cable, 3 various standard ADSL phone cables

And it looks like Zen arent in today as its a bank holiday.