50MB - T3 timeouts logged

[GMCinema]

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]

Originally Posted by GMCinema

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_]

Originally Posted by GMCinema

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]

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]

Originally Posted by Moldova

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 ----------

Originally Posted by Sephiroth

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]

Originally Posted by GMCinema

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]

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/doc...n-maintenance/

[GMCinema]

Originally Posted by Sephiroth

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 ----------

Originally Posted by Broadbandings

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/doc...n-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_]

Originally Posted by GMCinema

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]

Originally Posted by GMCinema

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]

Originally Posted by Broadbandings

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]

Modem, in between coaxial feed and the modem itself.

[GMCinema]

Originally Posted by Broadbandings

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]

Originally Posted by Broadbandings

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]

Originally Posted by GMCinema

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.