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volgon4

join:2010-10-19

1 edit

[LA] SB6120 T3 Timeouts

Hey folks. I've been having Cox issues for years now. Most of the time they're infrequent enough that I can just suck it up for the week or so I'm having problems, but my modem is having T3 reset spouts every 2-3 days. During one of these events, the internet will sort of work, as it's not a complete disconnect or modem reset. All of the modem lights stay on. The internet is extremely slow during one of these events. The problem will resolved itself within a half hour or so.

Every time I've called support or had a tech come out they never find anything and so I have just about come to accept that my internet will never be stable. Hopefully someone with experience with this problem can point me in the right direction: it seems as though T3 timeouts are usually related to upstream issues but I'm always told all my signals look great.

Signal Levels:




Error from modem log:
Sep 30 2012 20:52:43 3-Critical R02.0 No Ranging Response received - T3 time-out

Modem Info:
Model Name: SB6120
Vendor Name: Motorola
Firmware Name: SB612X-1.0.5.1-SCM00-NOSH
Boot Version: PSPU-Boot 1.0.0.4m1
Hardware Version: 3.0

Thanks, any help would be greatly appreciated.

EDIT: forgot to mention a few things:

This is the second modem I've tried and I still have issues. My original SB5120 started having resetting fits every few days. I bought an SB6120 hoping it would solve the issue but to no avail.

I'm hooked up through a router: the issue occurs with both the old D-Link DI-524 and new Linksys E1200.

I will get T3 timeouts even if hooked directly from wall to modem.

Yes, I use a splitter to have TV and internet in my room. It's been changed out twice and the issue never went away.

SlashG42

join:2002-02-13
Metairie, LA
Reviews:
·AT&T Southeast
·Cox HSI

You might want to delete your cable modem's MAC since it's unique and individually identifiable.

What zip code in LA? I'm in 70002. Was having the random T3 timeouts with my SB6120. Signal levels looked fine. After about 5 tech visits with no solution, I bought a SB6180 off eBay. That mostly fixed it. Went from 2-3x per day to once per month.

Cox changed something in their system in this area. There have been a few users posting in the past 6 months or so about T3's in LA with a SB6120. In my case, the modem would stay online for weeks at a time with no problems. Absolutely stable.

I would get so ticked off when I would hear, "Your signal levels are fine." Of course they appear fine! You can only view the signal page when the modem is connected. When a noise spike kicks the modem offline, you cannot load the signal page, therefore if you can see the signals, they are fine. It's the stupidest diagnostic tool ever.

The one oddity I see in your case is that your 2 higher rate (Msym/sec) upstream channels cannot do 16QPSK, and your other 2 can do it, but they have been reduced to a lower rate of only 2.560 instead of the optimum 5.120Msym/sec. The fact that modulation modes and higher symbol rates are unavailable does indicate an upstream problem.

What has been replaced so far? Every connector and splitter between the pole and your modem?

Might be new modem time.


volgon4

join:2010-10-19
reply to volgon4

I'm in 70520, Carencro.

I honestly couldn't tell you exactly what has been replaced: I've had these problems over a span of 3-4 years, 2 modems, and a dozen or so tech visits. I know they replaced the cables going from the attic into my room's wall, the cables going from my wall to the modem and some cables in the attic as well. Other than that I couldn't really tell you what they've changed (or if they've switched out anything at all outside of the house).

Forgive me, but I don't know what Symbol Rate and Modulation specifically are. Since I've never researched what they should be I never knew if there was an issue related with them. Should all 4 channels be at 5.120 msym/sec? And should they all have 16QAM?

I had called up Motorola to see if they had heard of any issues with Cox and the 6120. They said no (which I expected). I still have a few months left on the warranty so I could send it in for a 6121 but I don't know if that would fix the issue (I thought I read they are essentially the same except for aesthetics or something). I might have to look at a 6180.

Thanks for the response and help.


SlashG42

join:2002-02-13
Metairie, LA
Reviews:
·AT&T Southeast
·Cox HSI

It's odd that your upstream channels aren't the same rates and modulation settings. They should all be 16/64 at 5.120Msym/sec. Anything else means that the modem is backing off on the settings as an effort to help improve stability over a less than ideal signal path.

Symbol rate is how many modulations per second. Modulation type defines how much data is in each symbol. Think of it as buckets per second, and bucket size.



bbeesley
VIP
join:2003-08-07
Richardson, TX
kudos:5
reply to volgon4

said by volgon4:

but my modem is having T3 reset spouts every 2-3 days.

when you say "T3 reset spouts" do you mean the modem is resetting or that it is logging a T3 timeout "every 2-3 days"

The modem shouldn't reset due to T3s...it will reset if it gets more than the configured number of T4s - the default is 16

If you are getting T3 timeouts every 2-3 days in your modem logs, then that is not bad.

A T3 is logged when the modem doesn't receive a response to an upstream ranging request. This does happen for various valid reasons but if it is happening frequently, like every few minutes, it can point to issues such as return path impairments

A T3 in and of itself is not a problem but lots of T3s correlated with packet loss or latency can help lead to the possible cause...certainly a T3 every 2-3 days by itself is not indicative of any service issue

I would look elsewhere as to the root cause of the slowdowns - might want to send a PM to one of the Cox techs here and have them look at Edgehealth or Proviso logs to see if they see anything.


bbeesley
VIP
join:2003-08-07
Richardson, TX
kudos:5
reply to SlashG42

said by SlashG42:

YOf course they appear fine! You can only view the signal page when the modem is connected.

They don't look at the modem, they look at tools that have collected SNMP data from the modem.

This data is polled pretty frequently and then displayed to the Cox reps as a web page containing information about levels, SNR, errors, etc over time as well as reference to other modems in the same service group.

they can see if the modem signals varied over days, weeks or even months

SlashG42

join:2002-02-13
Metairie, LA
Reviews:
·AT&T Southeast
·Cox HSI

The field techs here always log into the modem page from a local computer. I do not know if its poor training or ignorance, but I have never once had a field tech look at SNMP data. The general impression I got was most of them do not know what they are looking at in the first place. "Signals look good." Is usually enough to get the customer to sign off on the work order so they can be done with the job.


volgon4

join:2010-10-19
reply to volgon4

What I was saying is that the modem will start logging lots of T3 timeouts for a short duration and this happens every 2-3 days. While it is happening, my internet connection, while still somewhat functional, is going to be dropping out constantly. The modem doesn't reset, essentially what will happen is that I can browse for a bit, then get a T3 timeout (so nothing will load, I can't go to any webpages), then the internet will work again for a bit. Then I'll get another T3 timeout and no websites will load. This doesn't just affect my browser either, online gaming is affected as well.

Another way for me to describe it. I can take a speedtest when the timeouts start occurring. Since it's not a consistent thing, my speed will be normal, so about 20-25mbps. Then, if I have a timeout during the test, the speed will plummet. After the timeout error is corrected, the speed will shoot back up to 20-25mbps.

If it's not clear, I'm not getting one or two timeouts every 2-3 days. I could handle that. What I'm getting is a T3 timeout every 2-3 minutes. These timeouts occur for between 15-30 minutes every 2-3 days.

I'm actually having T3 timeouts at this very moment, very frustrating to have to deal with this constantly.



bbeesley
VIP
join:2003-08-07
Richardson, TX
kudos:5
reply to SlashG42

said by SlashG42:

The field techs here always log into the modem page from a local computer.

I wonder why they use the modem signal levels instead of just getting that from their DSAM?

If it were me, I would ask the tech to pull out their meter to verify levels and not just use the modem.


bbeesley
VIP
join:2003-08-07
Richardson, TX
kudos:5
reply to volgon4

said by volgon4:

What I'm getting is a T3 timeout every 2-3 minutes. These timeouts occur for between 15-30 minutes every 2-3 days.

What you are describing is symptomatic of a return path impairment.

I would go through all the cabling in the house, making sure nothing is kinked, all fittings are tight and secure, and remove and/or terminate any unused outlets.

If the issue still occurs, a tech needs to come out and do further troubleshooting to make sure there aren't any issues with the drop or feeder.

Suggest you PM one of the Cox reps here and ask them to take a look in Edgehealth and Proviso for uncorrectable errors on the modem and the upstream carrier(s) at the CMTS at or around the times you were experiencing the issue. If the uncorrectables are above .1% then it is a pretty safe bet there is a noise issue somewhere in the plant

volgon4

join:2010-10-19

1 edit
reply to volgon4

Had a tech come out but he didn't really find anything. My modem was showing packet loss on Edgehealth when he tested it and not on the modem he brought with him.

He said the symbol rates weren't supposed to be the same, I still have two channels at 5.120 and two at 2.560. He did say that the frequencies of my 4 upstream channels weren't frequencies that Cox uses. That doesn't make much sense to me since my internet works fine the majority of the time and the four upstream frequencies don't ever seem to change.

He put in a ticket to have a main line tech to come out but said it's possible they won't even bother. Not sure what I can do at this point, I've switched modems and still have problems. I might try to rent a Cisco modem from Cox for a month to see if I still have the same problems. First I think I'll reprovision my 5120 and see what the modem log says when I get errors with it.

EDIT: So I have my 5120 running now and I'm getting short lag spikes when gaming/surfing. Apparently they occur when I have a dynamic channel change which I've never seen in the modem log of my 6120. Is that because it's a Doc2 modem with only 1 upstream channel? My modem log is filled with messages about this channel changing. Could this be related to the issue with my 6120?


SlashG42

join:2002-02-13
Metairie, LA
Reviews:
·AT&T Southeast
·Cox HSI

Dynamic channel change is typically a provider-side load balancing feature. The channel you were on was seeing higher traffic than the one you were pushed to. It should not cause any loss of connectivity when it is properly implemented.

You are correct that D2 modems being single-channel will do DCC, while a bonded D3 modem will not need to DCC.


volgon4

join:2010-10-19
reply to volgon4

It doesn't cause me to lose connectivity (as in the modem restarts) but I do notice the change happening. My game will lag for a few seconds and when I check the log I see a channel change.



JeffinKenner

@cox.net
reply to volgon4

Sometimes it may help to reset the modem to defaults, then turn if off for 5 to 30 minutes. I can't guarantee it, but it seemed to help for for a little while.


volgon4

join:2010-10-19
reply to volgon4

I've scheduled a "second trip" tech visit as they called it on the phone. I called Motorola and got my power levels from Sept 26 when I called their support and they are a LOT different than what I was getting in the OP or now. My down power levels on the 26th were -1 -2 -3 -5, in the OP (4 days later) they're 1 1 0 0, they were 5 5 6 6 a few minutes ago and after I removed my splitter now they're 8 8 8 8 (which doesn't make any sense). Sounds like there is some major signal corruption going on somewhere.



digiblur
Premium
join:2002-06-03
Louisiana
reply to SlashG42

said by SlashG42:

It's odd that your upstream channels aren't the same rates and modulation settings. They should all be 16/64 at 5.120Msym/sec. Anything else means that the modem is backing off on the settings as an effort to help improve stability over a less than ideal signal path.

Symbol rate is how many modulations per second. Modulation type defines how much data is in each symbol. Think of it as buckets per second, and bucket size.

I'm not in the same market as the OP, but all the modems I've seen in my area have the same oddness in the upstream bonding.

Here's mine:
Channel ID 1  2  3  4 
Frequency 37600000 Hz 31200000 Hz 25400000 Hz 22200000 Hz 
Ranging Service ID 7077 7077 7077 7077 
Symbol Rate 5.120 Msym/sec 5.120 Msym/sec 2.560 Msym/sec 2.560 Msym/sec 
Power Level 45 dBmV 45 dBmV 43 dBmV 43 dBmV 
Upstream Modulation [3] QPSK
[3] 64QAM
 [3] QPSK
[3] 64QAM
 [3] QPSK
[2] 16QAM
[3] 64QAM
 [3] QPSK
[2] 16QAM
[3] 64QAM
 
 

volgon4

join:2010-10-19

It's strange, the technician that came out yesterday said those frequencies are not ones that Cox uses here, but we both have the same ones. Sounds like he was pretty misinformed.



JeffinKenner

@cox.net
reply to volgon4

Download Speed: 20522 kbps (2565.3 KB/sec transfer rate)
Upload Speed: 176 kbps (22 KB/sec transfer rate)
Latency: 7 ms
Thursday, October 25, 2012 1:29:45 AM


volgon4

join:2010-10-19
reply to volgon4

Tech just left. He said there was ingress from the modem in the line so he put a filter or something in the attic to cut it off. He mentioned that there was another case yesterday on the same node (different area though) with the same issues. Called up his supervisor and chatted with him about it, looks like they might be looking into a network issue. The tech put in a ticket (I guess a main line tech or something), hopefully someone will finally get this resolved soon.



JeffinKenner

@cox.net
reply to volgon4

I'm getting a lot of upstream noise causing T3 timesouts when the modem reboots. I'm havnig a tech look at it Saturday afternoon. Download is fine, upload is iffy.


volgon4

join:2010-10-19
reply to volgon4

Seems as though the problems I'm having are coming from packet loss. Even when I'm not getting T3 timeouts I have between 2-8% packet loss. I ordered some RG6 cables to replace all of the old ones we have connecting TVs to the walls. I'm not sure if there's any ingress coming from those cables but they're probably 15+ years old so I might as well switch them out to see if it helps. Might also call up support to see if they can drop new wall wires (those are probably 20+ years old).

I managed to catch what I assume to be a line tech checking out our box by the street. Really, really nice guy (Thanks Clint! Doubt you will see this). He said that the issues I'm having could be from all over the node and it's hard to pinpoint the exact issue. Said he would put a ping plotter test on my modem (hopefully he does do that). I guess all I can really do is wait and see.


volgon4

join:2010-10-19

2 edits
reply to volgon4

I went into the attic to look at the wiring, I thought maybe we had some old wires that could be causing the packet loss. It looked like all of the cables were either RG6s or RG59s. The coax cables feeding into the attic (the point of entry cable I guess you could say) from the outside and the one down the wall into the room with the modem were both RG6s so I think I'm okay there.

The tech that came out last Friday also put a filter in the attic to prevent the modem from pushing noise into the line. What cable is the filter supposed to be on, the cable that leads to my room (which contains the modem) or the cable leading to all the other rooms (which only have TV)?

An update: I provisioned the 5120 again so I could do some ping tests with it. I've had good results: 0-1% packet loss (the 1% is fairly uncommon and to be expected from time to time), normal ping and low jitter (most of the time). Before the switch my 6120 was getting anywhere from 2-8% packet loss, normal ping and high jitter (20-40ms). This seems to point to my issues being related to the modem. I'm going to keep the 5120 running for a while; I had separate issues with that modem (it rebooted randomly) so I'll keep an eye on the modem logs.