DSLAM problems? ADSL interruptions - mystery pls help

Hello,

I have been having an odd problem for about two weeks and while our ADSL provider has been working with us all this time, they aren't finding anything on their end. We are in a country where the telco used to have a monopoly, France. This is important to know because the former monopoly hates all the DSL providers and the competition. The telco will eventually have to cooperate, but for now they are not helping us.

The problem: Every 8 minutes, and you can set your watch by this interval (actually 242.8 seconds) we have an interruption of about 10 seconds on average. By interruption, I mean traffic no longer moves from my modem/router to the ISP's. Then flow comes back to normal until the next, totally predictable interruption in 8min+.

Here is what I've done on our end (with no change).

1) Swapped out the modem/router for a different one of a different brand. 2) changed the DSL filter, turned off all connected PC, removed phone equipt 3) used different power outlet 4) powered everything down for 5 minutes, then started the router alone and pinged it from another cèonnection. The 8 minutes remain "on schedule".

The interruptions pick up at their predictable time no matter what we do!

Am I wrong in thinking that the above more or less eliminates our end? If no compueters at all are running, nothing is connected to the router and the router is configured to allow pings, the ping from outside to the router stops at the usual times.

Outgoing pings to totally unrelated networks from both a Windows PC or a linux one connected to the router give the same results, 8min3sec, interruption 6-20sec. (usually about 10)

Pinging the first router I see towards the ISP shows likewise, 8 min interrupts.

At the low freq (analog) level, the phone works fine, no loss of dialtone, connection or noise of any kind.

Any ideas, theories?

It most certainly could be that, especially if the teleco feed is aerial. It might also be some antiquated telco equipment that counts "tics" for local call usage billing. Any sort of coil adds inductance across the loop and will soak up DSL signals. They'll take a few seconds to re-establish (TCP windows) from even a very momentary disruption.

-- Robert

Quoting Neil W Rickert:

I'll look into that - I was a ham radio operator from the age of 13 :) Wonder where I can find a radio though?

This said, the connection has been fine for a few years (of course maybe the interference just started) and I also neglected to mention that we have DSL connections on both of our phone lines, and the other connection suffers no such interruptions. We are in Paris, and the phone lines arrive in the normal copper.

I'm still guessing it's on their end, but I'll pursue this.

Heh, age creeps on the multiplication tables... about 482.8 seconds (8m 2.8s) calculated as an average over a few hours. To the human sensibility, it's 8 minutes. I have to watch my ping graphs when speaking over voIP!

Good point though about the periodicity of interference, thanks to both of you.

See if a firmware upgrade to your router is available. Use a browser to go to the mfgr's site and see if there's a download for your model router. Flash with new firmware if so, and try again. Who to call? Probably call your ISP and ask them to roll a truck to troubleshoot your DSL. Ping is just an indicator. Your ISP should be able to do more substantial line testing from their end without rolling a truck (mine runs a 15..30 minute test from their end). If they do send a technician he should have a meter to look at the DSL spectrum on your line, which may be G.lite or G.dmt if you have ADSL. You may end up having to have a clean line installed rather than one that also carries your voice, but you should have a technician try to troubleshoot the line first.

Regards, Scott

Hello again,

None of the investigations of the phone company or the ISP or their upstream have found anything, but we still have the interruption every 8 minutes.

Acting on the suggestions about RFI:

Who can I call to get some kind of testing of our phone line (I'm thinking a scope might show the noise if there is any) and the electrical wiring in our building? Who can trace down problems like this?

Although I'm in France, I'm sure if someone gives me some idea of what kind of speacialist to call, I can find someone.

tia

I have the latest firmware but I have swapped in THREE different routers. I have two DSL connections on two phone lines that arrive in the same cable

The ISP says they have done everything they can. I think this is true and it's at the DSMAL

Yes, but the fact that all traffic on this connection stops for ten seconds every 8 minutes (ping is just an easy way to test) is significant.

The phone co came here twice and did this and found nothing unusual. They also claim they actually reconnected the line at the DSLAM.

To me this is either RFI or electrical interference or a subtle problem at the DSLAM - so subtle their engineers can't find it!

How much checking did they do on your line?

Did they just check the signal in the house? At the Network Interface Device or whatever you have there?

Did they do a full test checking for load coils, bridge taps, balanced line tests? Impedence, etc. Usually when they do that, they will usually find something.

If you still have a problem, do you have another modem? What kind of modem is it? Do you know by chance the DSLAM type ?

"Amanda Reck>

Alright, one other really simple test. Since you seem to be able to set your watch by the outage every

8 minutes, please come up with the router and start running ping, then at 6 minutes after the outage reboot the router. Does the outage continue in about another 2 minutes, or does the outage happen in 8 minutes? I'm trying to get a feel if rebooting the router affects the period of the outages. Maybe the signal degrades over time to the point where at 8 minutes the G.dmt has to retrain, causing a 10 second outage. If you reboot at 6 minutes and the outage happens in another 2 minutes, then the modem isn't retraining due to degradation over time. Hence, I'd have a pretty good feeling that the data transmission protocols themselves aren't a part of it.

Let's suppose it's RFI or EMI. I'll probably be flamed for this, but rig up an adapter so you can hook your DSL wall line to the antenna terminals of a cheap AM radio. (The DSL line has high-pass filters on it so your AM radio shouldn't see

48V ringing on it, but I did say cheap AM radio just in case.) You're testing for a spark-gap type of interference. Tune to an unused part of the band. Do you hear static crackling every 8 minutes?

This next question is a WAG. Do you have a plywood manufacturing plant within five or so miles of you? There is a plant in Mexico that uses a large RF oven to dry their plywood. The combination of wet glue and dry wood acts as a big capacitor, tuning their oven. Every few minutes one can hear the static of the oven sweep across the spectrum, from

30MHz downward, as the plywood dries and de-tunes the oven. They aren't 8 minutes; more like 2 minutes or less. I'm 150 miles from them and I can hear it on scanners and shortwave radios but it's too weak to wipe out DSL for sure.

Do you have an UPS separating your computer and the router from your electrical socket? Also, do you have a good ground (earth) for the socket you're plugged into?

Regards, Scott

Consider also this article on dimmer switches:

This is France. The telco hates people with DSL that aren't paying *them* for the service. They didn't do shit, they just had a box that talked to the other end. Further, their tests reveal a weird impedance that no one can explain, yet they do'bt do anying about it.

I think I mentioned, I tried three different modem/routers (common here):

Linksys WAG54G, Alcatel Speedtouch 510, and a French made one I can't remember the name of (it's not here).

I also have two phone lines in that same cable, both have DSL connection and filters. The other line has no problem (which would seem to eliminate the router and RFI entirely). The same routers work on the other phone line. (Indeed one of them is always on that other line, I switched just for testing.

Quoting Scott Packard:

Did it the first day. The 8 minutes (+about 2.5 seconds) is stable I can do a printout of the times (I actually made a web page to do this, enter the time of the first outage and it prints the "schedule" for the day!) I turn all the equipment in the whole office off, all PC, routers, remove everything from the phone. I can turn on just a PC on the other side of the room on the other DSL connection and connect just the router to the faulty line. The router is set to allow pings. Pinging the connection from a distance shows the cutoffs on sched every 8 minutes.

Heh, you're gonna laugh but I'm still trying to find a radio :)

Nothing like that, but I did turn on an AM radio in the cellar (not far from the router) and heard nothing at the appointed time.

No UPS but a good ground. Again, there are two DSL connections coming in on the same cable and the same 3 routers work on one but have the problem on the other. I am considering a UPS anyway so I'll eventually be able to make this test.

Speaking of RFI, we have two small fridges downstairs, so I obviously turned them off one by one and saw no change.

I'm getting more and more sure it's something the telco is responsible for, yet it was hard to get them to act at all.

Actually, if I understand the mentality of the "fonctionaire francais", they actually rather like having someone else provide service. It gives them someone else to blame.

That would be _work_! Horreurs!

I think the most you will get from them would be to switch you to a different pair. Even this would be work, because they'd have to punch new jumpers at the CO and wherever your house drop splits from their large multipair line.

But be very sure it's none of your premise equipment (cable box, electric/gas/water meter, alarm ) by completely disconnecting everything by the DSL modem at whatevery you have that passes for an NID.

-- Robert

Sounds like NEXT (Near End(DSLAM side) Cross Talk).. is causing your DSL modem to retrain every 8 minutes. It's your unlucky day/week/month.. Probably caused by the wire pair in relation to some other wire pair in the same cable (all the way back to Co office DSLAM).

Note: Teleco's are simply not equipped to deal these type of problems.

Does this occur 24x7?... It might be something as simple as the local Alarm co. using out of band polling, to the check status of customer alarm systems (via telephone line,every 8 minutes).

Hi Amanda,

Do you know if both your phone lines go to the same exchange, IE are the Telephone no.'s on those lines similar? It may be interesting to see if both lines report the ATM parameters as similar or not.

One other possibility from your first post struck me -

I remember a similar type of issue many years ago on a plain old POTS line when using standard Modem calls, the modem would either drop the call after EXACTLY nnn seconds, or go into a retrain from which it rarely recovered. The problem was tracked down to a specific brand of telephone in use in the users house that used the line voltage present to re-charge its stored number memory, and when it turned that on, the line would die. If a voice call was in progress on the telephone, it would not re-charge its capacitor, making the issue invisible to voice calls, but because the phone was still "on-hook" at the time the modem was in use, the phone assumed it could take control of the line and do this. Removing that Phone removed the problem.

So disconnect ALL OTHER devices on the line for a while and see if the ADSL link pauses for those 10 seconds the same as before.

I hope this helps..................pk.

You say you have two DSL lines coming in, one has an interruption every

8 minutes and the other has no interruptions. Well, that pretty much eliminates external RFI/EMI, since there's a 99% change the cable pairs travel in the same jacket from your neighborhood concentrator to the telco. There's a small chance that they're running in two separate bundles, and one bundle is introducing enough noise to knock out your DSL. I find that hard to believe. That would be alot of noise, enough it seems to cause more than one complaint. There's a small chance that the one cable is running on a split-pair, where somebody accidentally uses the "tip" of one cable pair and the "ring" of another cable pair. Google on split-pair for symptoms, but if your wire maintenance man was decent he'd catch that. Also, you'd occasionally hear voice conversations on the line. A good DSL line that's also carrying your voice traffic will be very quiet with respect to echo, crosstalk, and external RF interference.

Your routers misbehave on one line and work fine on the other, so they won't really be to blame. Only thing left is either the telco, or spurs on the last hundred meters or so of your line. You said you had line maintenance out a few times, and they should have eliminated the spurs during their troubleshooting.

I hate to mention this, but maybe it's time for legal assistance.

Regards, Scott

Crosstalk can occur between specific pairs within a cable..

Check out page 12...

Pair to Pair Cross talk variances within a 50 pair Binder group can be as high as 15dB/1000ft..

Quoting Tim Keating:

Especially when they love to be uncooperative after losing decades of monopoly.

Yes, it began in April and has been ongoing since.

Wouldn't there be a loss of sync at this point? Also, there are no errors in the Linksys log, except an occasional warning about an incomplete packet or something.

We may consider adding a DSL only line and changing our connection. It's a real waste of time in the meantime, especially since out other DSL connection does not provide a fixed ip.