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NOCTech75
Premium
join:2009-06-29
Marietta, GA
Reviews:
·Comcast

[Connectivity] Packet loss, one upstream channel w/T4 Timeout

OK, after having loads of issues with packet loss in iRacing I finally noticed something, first here are the modem logs:

Oct 09 2012 21:04:11 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=3c:75:4a:74:d0:e0;CMTS-MAC=00:01:5c:22:6c:d1;CM-QOS=1.1;CM-VER=3.0;
Oct 09 2012 17:22:31 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=3c:75:4a:74:d0:e0;CMTS-MAC=00:01:5c:22:6c:d1;CM-QOS=1.1;CM-VER=3.0;
Oct 09 2012 17:22:11 3-Critical R04.0 Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=3c:75:4a:74:d0:e0;CMTS-MAC=00:01:5c:22:6c:d1;CM-QOS=1.1;CM-VER=3.0;
Oct 09 2012 15:13:56 4-Error D103.0 DHCP RENEW WARNING - Field invalid in response v4 option;CM-MAC=3c:75:4a:74:d0:e0;CMTS-MAC=00:01:5c:22:6c:d1;CM-QOS=1.1;CM-VER=3.0;

Basically the entire log is a wash, rinse and repeat of above... then I looked at the signal levels:

Downstream Bonding Channel Value
Channel ID 2 1 3 4
Frequency 579000000 Hz 573000000 Hz 585000000 Hz 591000000 Hz
Signal to Noise Ratio 36 dB 36 dB 36 dB 36 dB
Downstream Modulation QAM256 QAM256 QAM256 QAM256
Power Level
The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading
-2 dBmV -1 dBmV -2 dBmV -2 dBmV

Upstream Bonding Channel Value
Channel ID 1 2 3
Frequency 34800000 Hz 27900000 Hz 22600000 Hz
Ranging Service ID 3435 3435 3435
Symbol Rate 5.120 Msym/sec 5.120 Msym/sec 2.560 Msym/sec
Power Level 47 dBmV 47 dBmV 49 dBmV
Upstream Modulation [3] QPSK
[3] 64QAM
[3] QPSK
[3] 64QAM
[3] QPSK
[2] 16QAM

Ranging Status Success T4 TimeOut Success

Channel 2 upstream is T4 TimeOut, Channel 3 is only 16QAM. Is this something I need to call support about for a truck roll?


pclover

join:2008-08-02
Santa Cruz, CA

Re: [Connectivity] Packet loss, one upstream channel w/T4 Timeou

I would say a truck roll isn't a bad idea. They can come out and check your line for noise, ingress, or other problems.


EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:10

1 edit
reply to NOCTech75
What does the uSNR (upstream Signal to Noise Ratio) figure look like ? You will have to call in for this.

dorkino
Premium
join:2004-02-22
Atlanta, GA
said by EG:

What does the uSNR (upstream Signal to Noise Ratio) figure look like ? You will have to call in for this.

Do you know exactly what we should ask for when calling in for the uSNR? Each time I've called in for this in the past, it's been very difficult to get the rep to understand exactly what I'm asking for. They usually start by giving me the upstream power level, followed by the downstream SNR, and then maybe later if I'm lucky, they eventually find the upstream SNR - but not always. Are there certain screens we can tell them to check, or a program they should run... commands to run... what to look for on the screen, etc.

TIA

andyross
Premium,MVM
join:2003-05-04
Schaumburg, IL
reply to NOCTech75
Most areas seem to have a 64/64/16 QAM setup. The lowest frequency will typically be the 16QAM as it tends to be noisier and 16QAM is more tolerant of noise.

Also, with the SB6120/21/41, it always seems to be the middle channel that T4's out, even when it's not the middle frequency (I think I've seen one posted that was not sequential.) I still think there is a bug somewhere in the modem or CMTS or even the standards.

rendrenner

join:2005-09-03
Grandville, MI
reply to NOCTech75
Do you actually have a SB modem?
There is a new firmware set supposed to be rolling out. 1.0.6.8 I believe. Im still waiting for it here. I no longer have the T4 issues with my SBb6121 since they have disabled UCB in this area.


NOCTech75
Premium
join:2009-06-29
Marietta, GA
Reviews:
·Comcast
rend... I do have the 6120. This actually started when we went to bonding channels. Problem is it the modem and Comcast think the channel is up so they try to send data on it... and it results in packet loss. Instead of just marking it out of service like should be done.

travelguy

join:1999-09-03
Santa Fe, NM
reply to andyross
That's what is happening with me - even with 1068. Two of the three channels (1 and 3) sync up with 64QAM with no problem. The middle channel (2) gets a T3 error on startup regardless of power level (even at night when its colder and the power is down around 47) and doesn't connect.

Unfortunately, that means my upstream speed is limited to about 1.5MBps - a pain for doing cloud backups.

rendrenner

join:2005-09-03
Grandville, MI
reply to NOCTech75
Yeah the heavy T4 count was common for the 612x's with a bad upstream channel. The white pages for the new firmware is in this thread

* »[Connectivity] New SB6120/6121 Firmware Released *

A truck roll wont fix that part, The new stuff is not fully rolled out yet. No idea on how that process works. You do have a bit of a signal issue that could use a look at tho. Could be something in house could be something on the network a tech could at least get the ball rolling on. Its not super bad, but it could be better.

The IFCR on your 34MHz is off slightly.


NOCTech75
Premium
join:2009-06-29
Marietta, GA
So the question becomes with obviously broken firmware when are they going to get it out to the rest of the world?

rody_44
Premium
join:2004-02-20
Quakertown, PA
Motorola writes it than sends it to comcast. Comcast tests it with part of the world and if all goes well they send it out to all of the world. I suppose we are between part of the world and all of the world.