Topic 'Modem developing an affinity for 1 of 4 downstream channels' in forum 'Comcast HSI' - dslreports.com

Re: Modem developing an affinity for 1 of 4 downstream channels

Sun, 27 Jan 2013 21:02:53 EDT

PGHammer posted : It's not unique to a specific modem brand; I have a different ARRIS cable modem (WBM-760A) than plencnerb and it has a similar-though-different affinity; if anything, I suspect CMTS differences AND modem chipset differences are in play.

Re: Modem developing an affinity for 1 of 4 downstream channels

Sun, 27 Jan 2013 14:26:24 EDT

owlyn posted :

said by plencnerb:

said by EG:

said by plencnerb:

Am I to take it that having none at all is a very good thing?

I'd say so unless the modem's measuring mechanism is defective. For the halibut, have you tried clicking on that "Reset FEC Counters" button ?

I have not done so.

And, I think Murphy's law is in play here. I re-loaded my modem's config screen to go ahead and click the link "Reset FEC Counters", and now I have non-zero values in the "Correcteds" column. :o I had to go and say something about it and then jinxed myself! :)

New pic is attached for reference. By the way, I did not click the Reset FEC Counters link yet. I'll wait and see how things go.

--Brian

And don't be alarmed, but your downstream power levels are on the high edge of acceptable.

Re: Modem developing an affinity for 1 of 4 downstream channels

Sun, 27 Jan 2013 12:48:52 EDT

plencnerb posted :

said by EG:

said by plencnerb:

Am I to take it that having none at all is a very good thing?

I'd say so unless the modem's measuring mechanism is defective. For the halibut, have you tried clicking on that "Reset FEC Counters" button ?

Re: Modem developing an affinity for 1 of 4 downstream channels

Sun, 27 Jan 2013 12:13:53 EDT

EG posted :

said by plencnerb:

Am I to take it that having none at all is a very good thing?

I'd say so unless the modem's measuring mechanism is defective. For the halibut, have you tried clicking on that "Reset FEC Counters" button ?

Re: Modem developing an affinity for 1 of 4 downstream channels

Sun, 27 Jan 2013 11:49:47 EDT

plencnerb posted : If I'm reading my status screen right, my modem, which is an Arris TM722G, appears to favor my first downstream channel (DCID #3).

For reference, my modem has an up-time of 20 d: 14 h: 00 m at the time the picture was taken.

Also noted that I do not have any "Correcteds" or "Uncorrectables" listed. From looking at other screen pictures, most people have numbers listed in both of these columns for at least one of their downstream channels. Am I to take it that having none at all is a very good thing?

--Brian

Re: Modem developing an affinity for 1 of 4 downstream channels

Sun, 27 Jan 2013 10:24:20 EDT

IowaCowboy posted : My modem (a rented Arris TM820a) is about even on codewords. I have 8x4 channel bonding and the numbers seem about even among the 8 downstream channels.

Re: Modem developing an affinity for 1 of 4 downstream channels

Sat, 26 Jan 2013 00:08:33 EDT

n_w95482 posted : My current SB6121 is even on all four channels, but I frequently noticed one being higher than the rest on my previous SB6120.
--
KI6RIT

Re: Modem developing an affinity for 1 of 4 downstream channels

Fri, 25 Jan 2013 21:52:18 EDT

NetFixer posted : FWIW, for about the past week, my SB6121 has been showing a preference for the highest frequency channel (not the "Favorite Frequency"). I suspect that it is just random chance based on how busy each channel is.

[att=1]

Re: Modem developing an affinity for 1 of 4 downstream channels

Fri, 25 Jan 2013 21:32:21 EDT

dorkino posted : Come to think of it, I don't recall ever seeing this happen prior to the most recent firmware push that I received a few months ago. Maybe it's related; maybe not.

Model Name: SB6121
Vendor Name: Motorola
Firmware Name: SB_KOMODO-1.0.6.8-SCM01-NOSH
Boot Version: PSPU-Boot(25CLK) 1.0.12.18m3
Hardware Version: 5.0
Serial Number: (redacted)
Firmware Build Time: Aug 30 2012 15:35:46

But, yeah, you're right. I'm not really concerned about this... just curious is all. Thanks everyone for your input.

Re: Modem developing an affinity for 1 of 4 downstream channels

Fri, 25 Jan 2013 16:27:08 EDT

telcodad posted : Yeah, with the Motorola SB61XX modems, it's typical that they display about several hundred to a thousand Uncorrectable Codewords for each channel right after it boots up. After that, the Correctable and Uncorrectable errored codeword counts will normally slowly increment if you're getting good downstream signals.

On my SB6121 modem, the Total Unerrored Codewords counts are roughly the same, as well as for many of the SB61XX signal page screenshoots I've seen posted in this forum, though a few of them have shown one channel having a count of up to twice as much as the others.

As the errored codeword counts for your modem look good, and you say it's operating OK, I wouldn't worry about that anomaly.

Re: Modem developing an affinity for 1 of 4 downstream channels

Fri, 25 Jan 2013 15:57:57 EDT

dorkino posted : Well the errored codeword count happened directly after reboot. I don't think they've increased at all in the 13 days the modem's been online.

Favorite frequency is, in fact, 669000000Hz.

Re: Modem developing an affinity for 1 of 4 downstream channels

Fri, 25 Jan 2013 15:37:16 EDT

telcodad posted : What's also strange is that, while the Total Unerrored Codewords shown for that one channel is over 50 times greater than the others, the Correctable and Uncorrectable codeword counts are not that much different from the other channels.

That would indicate that the error rate is therefore about 50 times less than the other 3 channels, yet the estimated SNR (which, I believe, is calculated from the error rate) for that channel is shown as being the same (37 dB) as the others.

To me, it seems that there is some problem with the display of the Total Unerrored Codewords count for that first channel/column.

Re: Modem developing an affinity for 1 of 4 downstream channels

Fri, 25 Jan 2013 14:16:01 EDT

EG posted : FWIW, the UCD (Upstream Channel Descriptor) information that the modem needs to know in order to establish the frequency of the return / upstream channel to talk back to the CMTS on is contained on that favorite channel. It is my understanding the the UCD data is not present on all the forward / downstream channels on a system, just certain ones.

Re: Modem developing an affinity for 1 of 4 downstream channels

Fri, 25 Jan 2013 13:52:00 EDT

andyross posted : My 6120 is evenly split between the channels. I think that 'favorite frequency' just means the first one it tries on a reboot. Just like a non-D3 modem, it just remember that last one used. Once it makes the connection, it is then assigned the other channels.

I wonder if the 6121 is counting ARP traffic or whatever that may only travel over the primary channel, but the 6120 isn't.

Re: Modem developing an affinity for 1 of 4 downstream channels

Fri, 25 Jan 2013 13:38:40 EDT

NetFixer posted : If you look at the Configuration tab in the modem admin pages, you will see a category called "Favorite Frequency", and most likely that "Favorite Frequency" will be the one that you see being given preference.

[att=1]

I suspect that the phrase "Favorite Frequency" was not a random selection. ;)
--
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Re: Modem developing an affinity for 1 of 4 downstream channels

Fri, 25 Jan 2013 13:33:27 EDT

ExoticFish posted : Not seeing this on my SB6120.

Re: Modem developing an affinity for 1 of 4 downstream channels

Fri, 25 Jan 2013 13:25:16 EDT

anon posted : I also have the first channel bearing the higher amount of usage, and my SB6121 has been working without problems for the last 3 months. I get the provisioned speeds when I speed test. Perhaps the modem uses the first channel as the default channel and if a small file is being downloaded, the modem doesn't have a chance to send much on the other channels.

Modem developing an affinity for 1 of 4 downstream channels

Fri, 25 Jan 2013 12:45:02 EDT

dorkino posted : My SB6121 has been online for 13 days now, and I've noticed that it develops an affinity for one of the four bonded downstream channels. After a reboot, all four channels seem to be used equally, but eventually the 1st channel listed from the left (channel ID 2) seems to bear the brunt of the traffic. All 4 channels' codeword count continually increase, but this one channel increases at a rate far faster than the other three.

Example numbers - this is after 13 days:

Channel ID 2 1 3 8
Total Unerrored Codewords 54081190386 1018690810 1018689582 1018685906
Total Correctable Codewords 106 65 67 47
Total Uncorrectable Codewords 7713 7838 9139 1288

Note channel 2 has 54 billion codewords, while the other 3 channels have only 1 billion. Interestingly enough, my downstream speed seems to be unaffected. I can get approx 25Mbps down, which is the same speed I can get even after a fresh reboot.

The log shows the usual T3 timeouts that are always there. No idea of their frequency though since it only keeps the most recent one. Also I see this message 3 days ago: SYNC Timing Synchronization failure - Loss of Sync.

Is this anything that I should be concerned about?

Thanks