New Problems

[dawmdt]

Hi All,

About two weeks ago my 50mb service started to play up with random drop-outs (lasting anything from 15mins to a couple of hours) and, rarely, a connection with an unusably slow speed (usually it's either just connected or it's not). When it goes down that blue tick icon on the front panel goes out.

It's very sporadic eg last weekend it stayed up all weekend but last night and today it's been up and down more times than a trampolining rubber yo-yo.

I phoned tech support who asked me to connect to the modem (192.168.1.100) and he asked for a few numbers - these numbers told him there were definite problems on my line. They managed to get an engineer to me the same day who plugged in some test equipment to line (normally where the modem is, ie at the end of the chain) and declared "the signal is too strong" and he went back to the van and "turned down the signal". He was probably here for about 10 minutes in total. It stayed up and stable for about 3-4 hours (and actually seemed much faster than it was before!) before it went down for two hours. When it came back up it was unusable and slow, although it then went down again for a few mins and came back up at a good speed.

Here are the numbers from my modem:

Cable Modem Downstream
DS-1 DS-2 DS-3 DS-4
Frequency 298750000 306750000 314750000 N/A
Lock Status
(QAM Lock/FEC Sync/MPEG Lock) Y/Y/Y Y/Y/Y Y/Y/Y N/N/N
Channel Id 48 49 50 N/A
Modulation 256QAM 256QAM 256QAM N/A
Symbol Rate
(Msym/sec) 6.952 6.952 6.952 N/A
Interleave Depth I=12
J=17 I=12
J=17 I=12
J=17 N/A
Power Level
(dBmV) 2.52 2.42 2.68 N/A
RxMER
(dB) 35.25 35.25 35.42 N/A
Correctable
Codewords 547346 964295 828866 N/A
Uncorrectable
Codewords 383 405 380 N/A

Cable Modem Upstream
US-1 US-2 US-3 US-4
Channel Type 1.0 N/A N/A N/A
Channel ID 4 N/A N/A N/A
Frequency
(Hz) 45800000 N/A N/A N/A
Ranging Status Success N/A N/A N/A
Modulation 16QAM N/A N/A N/A
Symbol Rate
(KSym/sec) 2560 N/A N/A N/A
Mini-Slot Size 2 N/A N/A N/A
Power Level
(dBmV) 55.25 N/A N/A N/A
T1 Timeouts 0
T2 Timeouts 0 0 0 0
T3 Timeouts 38 0 0 0
T4 Timeouts 5 0 0 0

It was the "codewords" and "Timeouts" numbers that particularly troubled the person on the phone - the above are with the modem being on for about an hour and has just dropped again (thank goodness for mobile broadband!).

My postcode is DA15 and I'm not sure if this is ex Telewest or NTL as I'm a new cable customer and it's always just been "Virgin". Cable modem is a VMNG300 plugged into a D-Link DIR-615 as supplied by Virgin.

I have another engineer coming tomorrow afternoon - what should I ask him specifically to check and\or test? Is there any clue in the numbers above as to what the problem might be?

Thanks,

Darren

[Ben B]

:welcome: to the forum,

Looking at this post http://www.cableforum.co.uk/board/34896851-post3.html your Upstream power level is at max so that could be causing the T3 timeouts on your connection but I could be wrong. Someone should be here soon to provide further assistance.

Ben :)

[Sephiroth]

We didn't see your event log but it'll likely be full of T3s. Tomorrow's engineer really needs to have Networks or someone check the upstream SNR estimated at the CMTS end.

Could we see the event log (REMOVE YOUR CM-MAC ADDRESS) and tell us what time the engineer was here so we can see whether the T3 spanned before/after

Did you look at stats before he came and can you remember your downstream power level? Also what attenuator did he put on - it should be sticking out of your modem?

Cheers

[dawmdt]

We didn't see your event log but it'll likely be full of T3s. Tomorrow's engineer really needs to have Networks or someone check the upstream SNR estimated at the CMTS end.

Could we see the event log (REMOVE YOUR CM-MAC ADDRESS) and tell us what time the engineer was here so we can see whether the T3 spanned before/after

Did you look at stats before he came and can you remember your downstream power level? Also what attenuator did he put on - it should be sticking out of your modem?

Cheers

The modem's been switched off\on so the event log is empty from that time but yes I do recall there being T3 timeout events ("No Ranging Response received" or something) and they did stop immediately after he'd been. He'd also pointed at the upstream powerlevel onscreen as being 49.25 which he said was correct (and it's now gone back up to that 58ish); I don't recall the downstreams unfortunately.

Attenuator says Forward Path Attenuator 6dB.

Thanks for all of your assistance on this!

Cheers,

D

---------- Post added at 19:43 ---------- Previous post was at 19:40 ----------

I'm also getting these in the log:

Unicast Maintenance Ranging attempted - No response - Retries exhausted;CM-MAC=xxxxx;CMTS-MAC=00:23:5e:6f:be:9c;CM-QOS=1.1;CM-VER=3.0;

Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=xxxxx;CMTS-MAC=00:23:5e:6f:be:9c;CM-QOS=1.1;CM-VER=3.0;

I don't know if this helps but when it disconnects I can't actually access the Modem page on 192.168.100.1...?

Darren

[Sephiroth]

If your pC is directly connected to the CM you should be able to do the login at any time. The upstream power at 58 dBmv is at the modem's limit so there's an upstream problem withoubt doubt.

So keep a copy of the modem stats and tomorrow's engineer really needs to have Networks or someone check the upstream SNR estimated at the CMTS end.

[dawmdt]

If your pC is directly connected to the CM you should be able to do the login at any time. The upstream power at 58 dBmv is at the modem's limit so there's an upstream problem withoubt doubt.

So keep a copy of the modem stats and tomorrow's engineer really needs to have Networks or someone check the upstream SNR estimated at the CMTS end.

OK thanks I'll pass on that advice to the engineer - the one today didn't know what "all those numbers meant" apart from the from the power one so hopefully tomorrow's will have more of a clue.

PC is connected via the DIR-615 - I would have thought it could route between the .100.x subnet the modem is on and the .0.x subnet my LAN is on regardless of whether or not the modem is connected? So perhaps that's a symptom of a faulty modem as well\instead of?

Cheers,

D

[Sephiroth]

Only way to find out is to be directly connected to the modem. If you can log into it then, that aspect of the modem is not faulty.

[dawmdt]

Just had a phone call from the engineer, he reckons they've fixed something in the exchange this morning that's been causing intermittent issues over the last few weeks for several people in my local area. He's going to telephone me as the last job of the day to see if it's working OK and if it is he'll assume it's fixed.

It's been on for about 45 minutes now and is fine - funnily enough, and it actually seems faster than it's ever been for me.

The upstream power level has been stable at 44.50 since it's been switched on although I have had two T3 timeouts when I was doing some heavy downloading (no speed loss during though). I'm still getting some correctable codewords on the downstream side but no uncorrectables (is this normal?)

So, does the above indicate to you all that this is probably fixed as he's suggesting or are these numbers still of concern?

Thanks,

Darren

[Sephiroth]

You shouldn't het any correcables (let alone uncorrectables). Up to 3% correctable vs total transferred downstream is considered acceptable. You could test this by a controlled download, noting correctable before/after.

Let us know.