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GMCinema
04-11-2009, 18:51
I have more and more T3 timouts logged with my 50MBit service and experience dropouts. Network Engineer was booked already on installation and my Upstream level was reduced from 56 to 52 subsequently a few days later. I get about 4-5 T3 timeouts per day. Is this normal?

GMCinema
04-11-2009, 22:02
I have more and more T3 timouts logged with my 50MBit service and experience dropouts. Network Engineer was booked already on installation and my Upstream level was reduced from 56 to 52 subsequently a few days later. I get about 4-5 T3 timeouts per day. Is this normal?

In fact today it is already at 8 occurances of T3 timeouts recorded within 9 hours .....

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) 25800000 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) 51.25 N/A N/A N/A
T1 Timeouts 0
T2 Timeouts 0 0 0 0
T3 Timeouts 8 0 0 0
T4 Timeouts 0 0 0 0

Cable Modem Downstream
DS-1 DS-2 DS-3 DS-4
Frequency 299000000 307000000 315000000 323000000
Lock Status
(QAM Lock/FEC Sync/MPEG Lock) Y/Y/Y Y/Y/Y Y/Y/Y Y/Y/Y
Channel Id 17 18 19 20
Modulation 256QAM 256QAM 256QAM 256QAM
Symbol Rate
(Msym/sec) 6.952 6.952 6.952 6.952
Interleave Depth I=12
J=17 I=12
J=17 I=12
J=17 I=12
J=17
Power Level
(dBmV) 11.99 11.78 11.98 12.02
RxMER
(dB) 33.83 34.21 34.63 34.63
Correctable
Codewords 9164132 4005460 2436312 2119279
Uncorrectable
Codewords 375 337 404 488

Peter_
04-11-2009, 22:51
Cable Modem Downstream

Power Level
(dBmV) 11.99 11.78 11.98 12.02

You need to call the 50Mb Support team on 0800 052 0431 as those power levels are to high, call tomorrow as soon after 0800 in the morning.

Sephiroth
04-11-2009, 23:19
Here goes for an attempted explanation. What Moldova says is, of course, your only way forward.

There are a number of timers (T1 through T4). In this case, the T3 timer covers what is known as a "ranging request" sent to the CMTS (head end). After each unsuccessful attempt (i.e. no reply), the upstream power is increased until it reaches its maximum - whereupon a T3 timeout occurs.

When you are connected to the internet, then I would expect to see the upstream power level rather lower (let us know please).

To my mind, the modem is behaving properly but somewhere in the circuit on the other side of the modem, there is a problem. It starts with the coax cable needing to be properly screwed in both ends, goes on to noise anywhere on the line between your gaff and the CMTS.

So, if it's not a loose cable, an engineer it has to be and I suspect some street or cabinet work.

GMCinema
04-11-2009, 23:23
You need to call the 50Mb Support team on 0800 052 0431 as those power levels are to high, call tomorrow as soon after 0800 in the morning.

Can you elaborate a little on this. The levels you are referring to are my downstream receive levels and I have no problems with that. I get my full 50Mbit Bandwith. The T3 errors relate to my Upstream channel.

---------- Post added at 22:23 ---------- Previous post was at 22:19 ----------

Here goes for an attempted explanation. What Moldova says is, of course, your only way forward.

There are a number of timers (T1 through T4). In this case, the T3 timer covers what is known as a "ranging request" sent to the CMTS (head end). After each unsuccessful attempt (i.e. no reply), the upstream power is increased until it reaches its maximum - whereupon a T3 timeout occurs.

When you are connected to the internet, then I would expect to see the upstream power level rather lower (let us know please).

To my mind, the modem is behaving properly but somewhere in the circuit on the other side of the modem, there is a problem. It starts with the coax cable needing to be properly screwed in both ends, goes on to noise anywhere on the line between your gaff and the CMTS.

So, if it's not a loose cable, an engineer it has to be and I suspect some street or cabinet work.

The installation Engineer already checked my path from outside the house to the modem and all was good. He raised a NETwork work request when he determined the Upstream power level was too high and a few days later they did some wk somewhere in the street dropping it by about 4dB. But I get these T3 timeouts pretetty bad. SO should that level be even lower?

Sephiroth
04-11-2009, 23:34
Can you elaborate a little on this. The levels you are referring to are my downstream receive levels and I have no problems with that. I get my full 50Mbit Bandwith. The T3 errors relate to my Upstream channel.

---------- Post added at 22:23 ---------- Previous post was at 22:19 ----------



The installation Engineer already checked my path from outside the house to the modem and all was good. He raised a NETwork work request when he determined the Upstream power level was too high and a few days later they did some wk somewhere in the street dropping it by about 4dB. But I get these T3 timeouts pretetty bad. SO should that level be even lower?

Well, I've explained the T3 timeouts. Looks like the engineer came close to the same diagnosis. You'll feel the modem fairly warm if the upstream dBmv is always arpund the 50 mark. 40dBmv is comfortable.

What are your normal levels?

Ignitionnet
04-11-2009, 23:51
50-52dBmV upstream transmit power is absolutely fine. Due to variations in distance from amplification, etc, it's not possible to have all modems at 40dBmV.

Quick FYI:

T3s usually don't cause transmit power to increase, the only time transmit power is increased due to CMTS not responding is during initial ranging, after this every time the modem transmits a range request and doesn't get a response back within 200ms the T3 counter is incremented but the modem does not increase transmit power. Once the modem has ranged and come online this only happens when the modem is told to in the range-response from the CMTS.

Here check this out:

http://www.dslreports.com/faq/comcast/2.1_Modems

Scroll to the bottom for the timeouts.

Also

http://bradyvolpe.com/2009/03/03/docsis101_station-maintenance/

GMCinema
05-11-2009, 00:17
Well, I've explained the T3 timeouts. Looks like the engineer came close to the same diagnosis. You'll feel the modem fairly warm if the upstream dBmv is always arpund the 50 mark. 40dBmv is comfortable.

What are your normal levels?

Wed Nov 4 13:08:23 2009 Wed Nov 4 21:09:53 2009 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=00:xx:xx:xx:xx:xx;CMTS-MAC=00:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.0;
Wed Nov 4 22:18:58 2009 Wed Nov 4 22:43:46 2009 Critical (3) SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=00:xx:xx:xx:xx:xx;CMTS-MAC=00:xx:xx:xx:xx:xx;CM-QOS=1.1;CM-VER=3.0;

I also get the Timing Synchronization failures since this morning when a new config file was downloaded to the modem: Mod Edit.
I had to manually restart the modem this morning since it hung with that.

---------- Post added at 23:17 ---------- Previous post was at 22:57 ----------

50-52dBmV upstream transmit power is absolutely fine. Due to variations in distance from amplification, etc, it's not possible to have all modems at 40dBmV.

Quick FYI:

T3s usually don't cause transmit power to increase, the only time transmit power is increased due to CMTS not responding is during initial ranging, after this every time the modem transmits a range request and doesn't get a response back within 200ms the T3 counter is incremented but the modem does not increase transmit power. Once the modem has ranged and come online this only happens when the modem is told to in the range-response from the CMTS.

Here check this out:

http://www.dslreports.com/faq/comcast/2.1_Modems

Scroll to the bottom for the timeouts.

Also

http://bradyvolpe.com/2009/03/03/docsis101_station-maintenance/

Thanks for this, how about the 12dB incoming, is that too high in your view?
So if the errors logged are not due to level missmatch how can they be sorted out?

Peter_
05-11-2009, 07:19
Can you elaborate a little on this. The levels you are referring to are my downstream receive levels and I have no problems with that. I get my full 50Mbit Bandwith. The T3 errors relate to my Upstream channel.

---------- Post added at 22:23 ---------- Previous post was at 22:19 ----------



The installation Engineer already checked my path from outside the house to the modem and all was good. He raised a NETwork work request when he determined the Upstream power level was too high and a few days later they did some wk somewhere in the street dropping it by about 4dB. But I get these T3 timeouts pretetty bad. SO should that level be even lower?
Yes you are getting T3 timeouts and both sephiroth and broadbandings have given a thorough explanation of reasons why, but your downstream is to high and requires adjustment as per this sticky http://www.cableforum.co.uk/board/34896851-post3.html

Ignitionnet
05-11-2009, 11:19
Thanks for this, how about the 12dB incoming, is that too high in your view?
So if the errors logged are not due to level missmatch how can they be sorted out?

Yes it's too high, going by this:

Correctable
Codewords 9164132 4005460 2436312 2119279

A 12dB 'forward path equalizer' installable by a service engineer will bring your power levels back to a comfortable range.

GMCinema
05-11-2009, 11:34
Yes it's too high, going by this:

Correctable
Codewords 9164132 4005460 2436312 2119279

A 12dB 'forward path equalizer' installable by a service engineer will bring your power levels back to a comfortable range.

Ok Thanks for this. Is the equalizer installable by the modem or outside my home?

Ignitionnet
05-11-2009, 11:39
Modem, in between coaxial feed and the modem itself.

GMCinema
05-11-2009, 11:46
Modem, in between coaxial feed and the modem itself.

Does it need a PSU, is is a passive equalizer and will they send it to me for a self install?

Sephiroth
05-11-2009, 11:50
Yes it's too high, going by this:

Correctable
Codewords 9164132 4005460 2436312 2119279

A 12dB 'forward path equalizer' installable by a service engineer will bring your power levels back to a comfortable range.
I'll translate that for you!

The forward path equaliser will discriminate between upstream and downstream and in this case would reduce the downstream input power to settle it at around 0dBmv. The equaliser, not being an attenuator, will not affect upstream power.

Ignitionnet
05-11-2009, 12:27
Does it need a PSU, is is a passive equalizer and will they send it to me for a self install?

Passive and sadly no they won't.

GMCinema
05-11-2009, 13:15
I'll translate that for you!

The forward path equaliser will discriminate between upstream and downstream and in this case would reduce the downstream input power to settle it at around 0dBmv. The equaliser, not being an attenuator, will not affect upstream power.

As with all passive equalizers, even the best ones, there will be some degree of insertion loss. This is why I was hoping they would use an active equalizer.

---------- Post added at 12:15 ---------- Previous post was at 12:14 ----------

I only took me 2 hours! on the phone (mostly on hold) to get a engineer sorted .....

Ignitionnet
05-11-2009, 14:39
Yes - insertion loss is approximately 0.5dBmV I'm afraid.

That 2 hour wait is ridiculous.

Peter_
05-11-2009, 19:58
I only took me 2 hours! on the phone (mostly on hold) to get a engineer sorted .....
This was on 0800 052 0431 you waited for that time on hold.:confused:

GMCinema
06-11-2009, 00:10
This was on 0800 052 0431 you waited for that time on hold.:confused:

Yes on that number, and that number is NOT! a dedicated 50Mb service line. I was reffered to a specialist 50Mb Agent twice ............

Peter_
06-11-2009, 00:16
Yes on that number, and that number is NOT! a dedicated 50Mb service line. I was reffered to a specialist 50Mb Agent twice ............
It should only come through to us no other department and it is best to call between 0800 and 2000 as it may be redirected to elsewhere as we are UK based and work those hours.

GMCinema
06-11-2009, 22:45
Service tech has been, used two 8dB + 4dB = 12dB inline passive forward path equalizers. Here are my levels now: are they acceptable?

Cable Modem Downstream
DS-1 DS-2 DS-3 DS-4
Frequency 299000000 307000000 315000000 323000000
Lock Status
(QAM Lock/FEC Sync/MPEG Lock) Y/Y/Y Y/Y/Y Y/Y/Y Y/Y/Y
Channel Id 17 18 19 20
Modulation 256QAM 256QAM 256QAM 256QAM
Symbol Rate
(Msym/sec) 6.952 6.952 6.952 6.952
Interleave Depth I=12
J=17 I=12
J=17 I=12
J=17 I=12
J=17
Power Level
(dBmV) 4.70 4.74 4.88 4.05
RxMER
(dB) 34.63 34.77 34.93 34.93
Correctable
Codewords 31851 11561 6738 10429
Uncorrectable
Codewords 291 283 274 285


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) 25800000 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) 52.25 N/A N/A N/A
T1 Timeouts 0
T2 Timeouts 0 0 0 0
T3 Timeouts 3 0 0 0
T4 Timeouts 0 0 0 0

Sephiroth
06-11-2009, 23:13
Is your service acceptable now?

We can argue about the levels forever! If your service is naff, then there is an ostensible explanation.