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Please help me with THG-540 and my provider

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Please help me with THG-540 and my provider

I have following problem:

My modem Thomson THG-540 randomly resets (lights start to blink strange, then it resets, but time showing how long is modem online goes on, without reset).

Here is recording of my modem during one of this problematic resets:

When this occurs, log shows following:

10/23/2008 21.57 68000300 03 DHCP WARNING - Non-critical field invalid in response.
10/23/2008 21.57 82000200 03 No Ranging Response received - T3 time-out

Technicians exchanged already modem, splitters etc. in my house, but the problem remains. I also connected modem to car battery to exclude power supply problem. So there must be problem at providers side. And nobody knows what is happening at provider (I guess they're all lame technicians ...)

Here are my cable modem signal levels:

Signal to Noise Ratio 35 dB
Power -5 dBmV
Power 46 dBmV

as far as I know they are ok.

And I noticed one more thing: Upstream modulation should be QAM64, but sometimes I see it changes after reset to QAM16.

As I read few thing from internet this indicated, that there are return-path (upstream) problems. Am I correct?

Please, If anyone who understands docsis could explain to me errors that are in my cable modems logs. Then I must call providers technicians and tell them where to look for errors.

Best regards from Slovenia, and thanks in advance for help!

Levels seem fine

Those levels look normal. Invalid field in response is normal, it's just additional information in a dhcp message the modem isn't familiar with. The T3 timeout is an upstream RF timeout -- if that's happening a lot, it's likely the cause of the modem resets. Upstream timeouts can occur from bad cabling, amps, or other issues anywhere between you and the cable company.

Today I got new error, with

Today I got new error, with modem reset:

ToD request sent- No Response received

and then I looked at modem and it resets again, so twice in a roll ...

I must keep calling cable company, they must repair my line ...

10/23/2008 21.57 68000300 03

10/23/2008 21.57 68000300 03 DHCP WARNING - Non-critical field invalid in response.
this is mean you lost some field in dhcp server

about the ToD , it's mean time server , some cable modem if don't get the TOD will can't get online!

What do you mean by: " you

What do you mean by: " you lost some field in dhcp server"?

Is there problem with DHCP server on my line?

Get a new modem

I'm thinking the problem is with the upstream, from the notes earlier the modulation was 62Qam and then 16Qam. I don't think the modem you have supports docsis 2.0. docsis 1.1 yes, but 2.0 I'm not sure. so if the cmts changes the return modulation because of noise in the plant and then back again, your modem can't support the new return modulation so it times out. could be old modem firmware as well.
I recommend you go and buy a new modem, best buy, office max, etc...
that way it's new and you don't have to lease it from your provider.
please let me know how you make out


Hm ...

Thanks for answer, but I can't just go and buy new modem, I have also telephony over this modem ... Provider leases this Thompson modems (and they exchanged me already 3 modems which were all new), and I can't buy any new cable modem here in Slovenia, as far as I know ...

And modem is Docsis 2.0 capable (This is from modem's data sheet:"euro-Docsis approved Design. The cable modem is certified to work on any Euro-DOCSIS based HFC cable system and is certified Euro-DOCSIS 2.0 by Excentis")

And the qam64 is there most of the time but now and then I see after reset it's back to qam16, until the next reset, then is back to qam64 ...

Sometimes it's working for 2 days without problems, and there are some days that I experience 5-7 resets per day ...

Don't worry about "DHCP WARNING"

Don't worry about "DHCP WARNING - Non-critical field invalid in response". I'm willing to bet it's the tftp options. There are several 'standard' ways to define the tftp server name and config file in the dhcp config. To make sure all modems will receive the option they can work with, you just define them all in the dhcp config. So when your modem receives the extra options (telling it the same info it already knows), it doesn't know how to read them and pops that warning. Not a big deal at all. Modem flapping would be an RF issue anyway. I can't think of any reason why a bad DHCP server would make a modem do that. It could prevent it from fully registering, but not flap.

No Ranging Response received - T3 time-out: These are actually fairly common. Don't worry about the occasional one. Only worry if you start to see a bunch of them. The CMTS and modem ping-pong as a way for the CMTS to know the CM is still alive for the CMTS to make adjustments to the CM. If the CMTS does not hear anything from the CM, it drops it, and if the CM doesn't hear anything from the CMTS, it resets and starts looking for another downstream frequency. It requires a number of misses before either happens. That T-3 timeout is the CM not hearing back from the CMTS when it should.

Typically flapping (constant cycling) is a downstream power issue. At -5 dB it 'should' be fine, but I've seen weirder stuff. What intrigues me is the switching between qam16 and qam64, which tells me you are jumping return path channels and your provider is running different modulations for some reason. Are you able to see the return path and downstream frequencies? Can you tell if the modem is frequency hopping? Does it always acquire the same downstream channel? Do you get cable TV through this connection? Any snow or audio distortion especially on the low channels? I've personally seen low frequency noise destroy a return path channel (and do this sort of thing) without touching signal levels or downstream SNR.

Now I finally got some

Now I finally got some useful answer from provider. With help of my recording of modem during reset, they figured out, that modem looses sync with CMTS (first light that goes off when reset happens is: Cable link). So they will forward this info to technicians for my area, and hopefully they will repair this issue soon ...

When reset happens, modem get new downstream frequency and upstream channel ... (now is DS freq.: 410Mhz and US channel: 2, and when reset will happen, DS freq. will be: 406Mhz (or something like that), and different US channel).

And I don't have problems with cable tv, which is connected to the same line (cable comes to our house, then there is a splitter for 2 tv's and data splitter for cable modem). Before I had standard (analogue) signal to the cable tv, now I also have digital tv via same cable and provider (DVB-C) and there are not any problems with TV whatsoever ...

At last my provider after a

At last my provider after a lot of mails, calls, faxes, etc ... managed to get my line straight. Now it's working without a problem for aprx. 10 days. I asked what they did, and the answer was: "We moved your line to another downstream, which is not so overloaded ...". So I know nothing exactly what they did, and If this is true ... But I'm happy for now, that is working. I'll keep my fingers crossed. :)

DHCP WARNING - Non-critical

DHCP WARNING - Non-critical field invalid in response.

you miss some Non critical field in dhcp response. but i think it's ok.

i think you can try
to get more current information in the cable modem .

by the way THG-540 is EMTA?

I tried ...

I don't know really if modem is EMTA ... because I don't know what EMTA stands for...

I tried docsdiag, but I can't connect to modem, my ISP has disabled SNMP ...

I'm more worried about T3 problems, it seems that there's a problem ...

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