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pathpingpong
join:2011-12-15

pathpingpong

Member

[AZ] modem frequently restarting because of UDP cap?

PROBLEM:
My modem frequently disconnects and reconnects with log message seen below.
This usually happens when I am using a BitTorrent client to get & share the latest nix distros, or when I am using Skype to video chat with family, or when I am playing online Quake3-engine video games.
I can reproduce the problem with 100% success by starting my BitTorrent client with uncapped uploading and also starting one of the games and joining a very active server.
The BitTorrent connections cause the problem anywhere from 60-1500KBps. The faster the connection, the more likely the modem will restart.
The game connections cause the problem at 25-35KBps with 25-90 datagrams per second.
I have also been able to reproduce the problem using Java speed tests that send UDP instead of TCP.
The games always use UDP. The UDP speed tests always use UDP. The BitTorrent client frequently uses UDP. Skype frequently uses UDP.
This leads me to believe either that COX is controlling UDP traffic by sending kill signals to the modems, or that my modem suddenly has developed a phobia of UDP traffic after 7 years of solid performance.

I am confident that my wireless router is not to blame.
I connected to the modem directly and the problem still occurred with the same frequency.
WIRELESS ROUTER: Linksys WRT54G2

PACKAGE: Residential Premier

MODEM: Terayon TJ715x

I have been recording the modem logs for over 2 months. This has added up to nearly 2000 lines, so I think an example is better than posting all of that.
I believe this is what is known as a T4 error.
LOG Example:
16:56:19 Error DCC-ACK not received
16:57:09 Critical Received Response to Broadcast Maintenance Request, But no Unicast Maintenance
16:57:09 Notice SNMP Poll - Mac Link Down.
16:57:09 Notice SNMP Poll - DS Link Down.
16:57:09 Notice SNMP Poll - US Link Down.
16:57:43 Critical DHCP FAILED - Request sent, no response
16:57:43 Notice TLV-11 - unrecognized OID
16:57:45 Notice SNMP Poll - Mac Link Up.
16:57:45 Notice SNMP Poll - DS Link Up.
16:57:45 Notice SNMP Poll - US Link Up.
16:57:45 Notice SNMP_AGENT_COLD_START

I normally connect to the shortest coaxial line from the source and get the best signals, but sometimes I add a 4-way splitter and get the worst signals. The problem still occurs frequently either way.
SIGNALS:
Tx Power 41.7 ~ 44.7 dBmV or with 4-way splitter 43.7 ~ 50.7 dBmV
Rx Power -3.7 ~ 0.2 dBmV or with 4-way splitter -11.1 ~ -6.0 dBmV
Downstream SNR 31.8 ~ 33.8 dB or with 4-way splitter 23.1 ~ 34.9 dB
Downstream MER 31.8 ~ 32.6 dB or with 4-way splitter 30.7 ~ 32.6 dB
Tx Frequency 29600000 ~ 36100000 Hz or with 4-way splitter 29600000 ~ 36100000 Hz
Rx Frequency 579000000 ~ 843000000 Hz or with 4-way splitter 579000000 ~ 855000000 Hz

I have read from 10 other people on this forum with a similar or identical problem.
2 of 10 had this problem with the same Terayon modem
3 of 10 had this problem with the Motorola SB5101 modem
1 of 10 had this problem with the Linksys CM100 modem
2 of 10 called out Cox and they were unable to fix the problem
3 of 10 fixed the problem with an unspecified DOCSIS3 modem
1 of 10 fixed the problem with a Motorola SB5101

I would rather not spend $70+ to get a new DOCSIS3 modem and still have the problem.
I would rather not spend $40+ to get Cox to replace a bunch of lines and still have the problem.
Should I purchase a new DOCSIS3 modem? Which one?
Should I call Cox out first and pray that I don't get charged?
m8trix
join:2003-12-24
Chandler, AZ

m8trix

Member

first issue is your using a non supported modem on the cox network and its well beyond its avg life span,dont recommend the 4 way as its throwing your signal off
pathpingpong
join:2011-12-15

2 edits

pathpingpong

Member

Reply to m8trix
That is why I mentioned that there are other, nearly identical cases that occurred with Cox compatible modems.
The 4-way splitter did not change my speeds and it did not change the occurrence of the problem. I mentioned it specifically to point out its irrelevance in the equation.

Do you think I require a DOCSIS3 modem to solve this problem, or would a different DOCSIS2 modem solve this problem?
Do you have a suggestion for a modem that has solved this problem in the past?
ultim_8
join:2002-07-30
Byron, GA

ultim_8 to pathpingpong

Member

to pathpingpong
That's a neat error. DCC is dynamic channel change. So from what I see DCC - Acknowledgement not received... Are you using 100% of your rated bandwidth?

I will say that a 7 year old modem is getting quite old. There have been lots of updates with the new docsis 3 modems. I'm very happy with my DPC3010. I've had it "burst" at 130/10. Of course you'll have to bypass a 10/100 router to see those speeds.

I do know that if you're at 100% upload the modem will drop packets. Some of that traffic might be "maintenance"...

I use Bittorrents to redistribute Ubuntu and I've seen it moving plenty of traffic and the modem hasn't rebooted.

Your signal levels without the 4 way are fine, I'm a little concerned with your SNR, do you have any packet loss normally? You might IM some of the cox techs and see what insight they may have.

I would start with the modem. No guarantees though...

Good luck
lilstone87
join:2009-04-09
Chesapeake, VA

1 edit

lilstone87 to pathpingpong

Member

to pathpingpong
said by pathpingpong:

Reply to m8trix
That is why I mentioned that there are other, nearly identical cases that occurred with Cox compatible modems.
The 4-way splitter did not change my speeds and it did not change the occurrence of the problem. I mentioned it specifically to point out its irrelevance in the equation.

Do you think I require a DOCSIS3 modem to solve this problem, or would a different DOCSIS2 modem solve this problem?
Do you have a suggestion for a modem that has solved this problem in the past?

I will save you from the modem questions, simple answer is go ahead and buy a D3 modem. As m8trix See Profile said your modem is way old, and most likely your source of your troubles. The reason I say go ahead and get a D3 modem. Is because sooner rather then later cox will stop supporting all D2 modems. Also a D3 modem will help stop slow speeds during prime time hours when everyone is using the internet. D2 modems can only connect to a single downstream channel, and a single upstream channel. D3 modems can bond multiple downstream channels, and upstream channels, and most cox area's have at least 4 available downstream channels to connect to. Plus that number is only gong up, since there are a few cox area's with 7-8 downstream channels available atm.

So save yourself the trouble and buy a D3 modem, and see how things are after that. Also if you live by a cox store, you can most likely save a few $$ buying a D3 modem from them. Since I have seen the going rate at around $80 for D3 modems from cox. Which retail stores like bestbuy, your gonna pay close to $100 for one. I know spending money sucks, but save yourself many of headaches, and get yourself a D3 modem.

Edit: as for a D3 modem of choice, if you buy one from cox. It will most likely be a Cisco DPC3010, or a Motorola SB6180. Both of these modems are 8x4, which means they can bond up to 8 downstream channels, and 4 upstream channels. Both are the latest D3 modems, which means there the best you can get right now.

dvd536
as Mr. Pink as they come
Premium Member
join:2001-04-27
Phoenix, AZ

dvd536 to pathpingpong

Premium Member

to pathpingpong
The terajets were good in their day but showing their age today.
looks like its time for a new D3 modem.
pathpingpong
join:2011-12-15

pathpingpong to ultim_8

Member

to ultim_8
said by ultim_8 :
...I do know that if you're at 100% upload the modem will drop packets. Some of that traffic might be "maintenance"...

I like that idea and wish it were that simple, but the Terayon restarted even with low bandwidth connections.
said by lilstone87 :
...save yourself the trouble and buy a D3 modem...
...as for a D3 modem of choice, if you buy one from cox. It will most likely be a Cisco DPC3010...

Purchased a new DPC3010 from the Cox store today.
I am disappointed that its firmware doesn't allow customers to see the log or other diagnostic information, but so far it has not restarted.

Hopefully I won't see this problem again for another 7 years.

Thank you for your opinions on this matter.

dvd536
as Mr. Pink as they come
Premium Member
join:2001-04-27
Phoenix, AZ

dvd536

Premium Member

Good choice in modem. the cisco is a fine modem.
its COX not cisco thats locking it down.

DocDrew
How can I help?
Premium Member
join:2009-01-28
SoCal
Ubee E31U2V1
Technicolor TC4400
Linksys EA6900

2 edits

DocDrew

Premium Member

said by dvd536:

Good choice in modem. the cisco is a fine modem.
its COX not cisco thats locking it down.

It's actually the default modem settings from Cisco that locks the modem down. The SA modems before Cisco bought the company did the same, as did the original Linksys modems which were based on the same hardware as the SA modems. Google "webstar feature is not enabled" for examples.

The modem has 3 levels of diagnostic screen access, by default it's set to the middle level, limited diagnostics. There's also a wide open setting and a locked out setting.

Cox can fix it by sending specific codes in the config file for those modems, but most other modems don't need them as they're wide open by default.

dvd536
as Mr. Pink as they come
Premium Member
join:2001-04-27
Phoenix, AZ

dvd536

Premium Member

said by DocDrew:

said by dvd536:

Good choice in modem. the cisco is a fine modem.
its COX not cisco thats locking it down.

It's actually the default modem settings from Cisco that locks the modem down. The SA modems before Cisco bought the company did the same, as did the original Linksys modems which were based on the same hardware as the SA modems. Google "webstar feature is not enabled" for examples.

The modem has 3 levels of diagnostic screen access, by default it's set to the middle level, limited diagnostics. There's also a wide open setting and a locked out setting.

Cox can fix it by sending specific codes in the config file for those modems, but most other modems don't need them as they're wide open by default.

I had it the day i got my modem. I could see the frequencies the modem was using and there was an option to select what upstream freq i wanted to use. that all went away at midnight when the modem got the cox firmware.

DocDrew
How can I help?
Premium Member
join:2009-01-28
SoCal
Ubee E31U2V1
Technicolor TC4400
Linksys EA6900

DocDrew

Premium Member

said by dvd536:

I had it the day i got my modem. I could see the frequencies the modem was using and there was an option to select what upstream freq i wanted to use. that all went away at midnight when the modem got the cox firmware.

I've been using SA, now Cisco, modems since about 2000 and it's been pretty consistent in that lock down most of that time, no matter which provider I've been on; Adelphia, Comcast, Charter, or TWC. It's also a very common complaint about SA modems across all providers.

I used to have a PDF file from SA that explained it all. Can't find it now.
pathpingpong
join:2011-12-15

2 edits

pathpingpong

Member

Oh ****! ****! ****! ****!!!!!
I'm thinking now that I just wasted $80+.
I am still getting modem restarts from leaving my *nix torrents running.

The new DPC3010 restarted about 8 times today just like the old TJ715X.
The new DPC3010 takes 4-12 minutes to restart where as the old TJ715X took only 2 minutes to restart.
The new DPC3010 is getting slower speeds (22Mbps down & 12Mbps up) than the old TJ715X (27Mbps down & 15Mbps up).
The new DPC3010 is displaying lower signal strengths (RX:-11 to -15 & TX:44 to 48 & SNR:35 to 38) than the old TJ715X (RX:-6 to -11 & TX:44 to 50 & SNR:23 to 35).

The only positive of the new modem is that so far it has not restarted during low bandwidth connections such as online games.
The new DPC3010 restarts with speeds as low as 250KBps where as the old TJ715X would restart with speeds as low as 35KBps.

Starting tonight, I will move the modem from its desired location (my home office) to the location closest to the source (my bedroom) and I will report on the results.

I am concerned by the fact that I have been getting much higher than advertised upload speeds. Could that be related to this problem?
m8trix
join:2003-12-24
Chandler, AZ

m8trix

Member

right now you signal levels are out of spec, your rx should be +10 to -10 close to 0 as possible,sof if any splitters try removing otherwise you may need a tech to resolved, cause you d3 modem is going to lock on to different freq then your old modem did and each freq has its own power levels.
pathpingpong
join:2011-12-15

pathpingpong

Member

I moved the modem into the bedroom, which is the closest branch to the source out of 4 total branches.
There are no splitters on this branch right now.

The new DPC3010 is reporting lower signal levels (RX: -4 to -7 & TX: 44 to 45 & SNR: 37 to 39) than the old TJ715X (RX: 0 to -4 & TX: 41 to 45 & SNR: 31 to 34).

Those levels for the old and new modems are for identical setups.
AZHSISUPPRT2
join:2007-11-01
Glendale, AZ

AZHSISUPPRT2 to pathpingpong

Member

to pathpingpong
pathpingpong,

PM me your cable modem's MAC address and I'll take a look for you.

Thanks,
pathpingpong
join:2011-12-15

pathpingpong

Member

Moving the modem seems to have reduced the problem. Looks like I only had 1 restart today according to my torrent client. Without access to modem logs, I do not know if this is correct.

I will continue recording diagnostic info manually.
Will wait and see if AZHSISUPPRT2 has time to dig up any dirt on my modem to know what is really going on.
pathpingpong

pathpingpong

Member

It has been one month since AZHSISUPPRT2 took a look and said that I was "losing QAM lock" and that I had "T3 and T4 timeouts". AZHSISUPPRT2 said that a ticket was opened for a potential problem in the local node.

I do know that the restarts are still occurring, but I still have no accurate means of recording the number of restarts on the DPC3010 each day. So, I will be writing a simple program to query the modem diagnostic page and log the details on frequent intervals.

I have moved the modem into yet another room. I have an amp on the line into the room and then a dc tap sending the out to the modem. The amp introduces more noise and more upload power but this seems to be the best configuration that does not require me to disconnect other TVs. (RX: -0.5 to 5.2 & TX: 49 to 54 & SNR: 32 to 37.9)
No matter where I put it, the DPC3010 seems to report lower RX and higher TX than the TJ715X did.

dvd536
as Mr. Pink as they come
Premium Member
join:2001-04-27
Phoenix, AZ

dvd536 to pathpingpong

Premium Member

to pathpingpong
said by pathpingpong:

I am concerned by the fact that I have been getting much higher than advertised upload speeds. Could that be related to this problem?

Thats just upload powerboost poisoning test results. nothing to be concerned about.
pathpingpong
join:2011-12-15

pathpingpong

Member

Another update just to let any onlookers know that this problem is not yet solved...

AZHSISUPPRT2 pm'd me about filing another ticket since apparently techs came out to the node and thought the problem was fixed but it is still occurring.

I finished writing my little logging program last week and have been running it nearly 24/7 ever since. It simply requests the status page of the modem every 10 seconds and records the signal levels reported.

Graphs of this data are pretty fun to look at. I noticed that high TX is much more detrimental to my connection than anything else. While amped, the TX would frequently spike to 57 dBmV under load, the SNR would fluctuate wildly from 28 to 36, and I would get 8+ restarts per day. After removing the amp, the TX now seems to stay down at 48-50 dBmV with infrequent spikes up to 56 dBmV, the SNR fluctuates slowly from 32 to 38, and I get at most 1 or 2 restarts a day if any at all. The downside of no amp is that the RX drops from about +1 dBmV to about -15dBmV, but I haven't really noticed any problems with this.

I just wish there was something I could do on my end to keep my TX consistently under 50 dBmV...
DarkPhantom
Premium Member
join:2008-09-13
Destin, FL

DarkPhantom

Premium Member

Path

You are not alone...I have a similar problem where my modem seems to just decide it will restart ( based on the log ) this happens nearly every 15 minutes.

What is weird is it started in Feb, didn't happen for nearly 60 days, and only happens at certain times.

I really don't want to call and have a tech waste my time with pointless things plus I live in an apartment.
mcowen
join:2001-12-05
Tempe, AZ

mcowen to pathpingpong

Member

to pathpingpong
One thing to be aware of is how modems balance power levels. The HIGHER the RX level, the LOWER the TX level and vice versa.

The reasoning is if your RX is low, the modem needs to output MORE signal to get back to the headend.

Just an FYI as many users don't realize the "balancing act" is taking place. I've stumped plenty of techs with this in the past.

dvd536
as Mr. Pink as they come
Premium Member
join:2001-04-27
Phoenix, AZ

dvd536

Premium Member

said by mcowen:

One thing to be aware of is how modems balance power levels. The HIGHER the RX level, the LOWER the TX level and vice versa.

The reasoning is if your RX is low, the modem needs to output MORE signal to get back to the headend.

Just an FYI as many users don't realize the "balancing act" is taking place. I've stumped plenty of techs with this in the past.

LOL thats a good one. actually its the CMTS that determines the power level for a given modem because it wants to hear all the modems at the same level. modem will then adjust its power level according to what the CMTS wants. there is no "balancing act"
mcowen
join:2001-12-05
Tempe, AZ

mcowen

Member

I'd warmly welcome pointers to some official documentation corroborating your claim.

While I'm told "my version" is how Cox internal techs are currently being trained, I can't prove it true. Where the CMTS can set the general power levels, the instant-by-instant levels are controlled by the modem. You can verify this with a variable pad inline with the modem. You can watch the levels change as fast as you can refresh your browser while you turn the knob. The CMTS does not respond -that- quickly.

AnonPhx
@cox.net

AnonPhx

Anon

»www.cablelabs.com/cablem ··· cations/

Your welcomed to read though the official documentation, there is too much there to search though.

The TX strength is set by the CMTS to have the return carrier hit the node at about the same strength as everyone else. The instant the signal is out of range it will request the modem to raise or lower depending on what the CMTS sees it at. Yes it responds that quickly, it's critical to the function of your cable modem. If you're using a variable pad on the modem, the modem doesn't know such a pad is in place and is merely responding to powerlevel change requests from the CMTS because the CMTS sees the TX coming in too low now.

While there should be a general correlation between having a high RX and a low TX, and a high TX and low RX there is no balancing act....merely signal attenuation and plant design.
AnonPhx

AnonPhx to pathpingpong

Anon

to pathpingpong
More to the original poster's concerns or at least what was reported on about the TX levels. The TX level on your modem should really never spike up and down....ever. This is normally due to ingress on the line in the form of cable damage or a some kind of backfeed from TV/VCR/etc. Nothing short of actually repairing the source of the ingress will fix the problem. There could be other problems at hand but I wouldn't think it's a bad idea to have a tech come out and make sure there isn't an ingress issue.

dvd536
as Mr. Pink as they come
Premium Member
join:2001-04-27
Phoenix, AZ

dvd536 to mcowen

Premium Member

to mcowen
said by mcowen:

I'd warmly welcome pointers to some official documentation corroborating your claim.

While I'm told "my version" is how Cox internal techs are currently being trained, I can't prove it true. Where the CMTS can set the general power levels, the instant-by-instant levels are controlled by the modem. You can verify this with a variable pad inline with the modem. You can watch the levels change as fast as you can refresh your browser while you turn the knob. The CMTS does not respond -that- quickly.

because the modem *knows* what the cmts wants and at any time can adjust its levels to maintain that.
thats why if a burst of noise hits, it adjusts it.
mcowen
join:2001-12-05
Tempe, AZ

mcowen

Member

Now that makes more sense, if the CMTS sets a range, and the modem adjusts itself within that range. Seems more likely than the CMTS diddling my power levels hundreds of times a second.

I'd also add my agreement that power levels should never have any spikes.