[AZ] Ton of weird errors.

[AZ] Ton of weird errors.
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anon @ 29th Oct 02:23PM:
[AZ] Ton of weird errors.

Hello guys, I've had Cox HSI for over a year and a half now. Have never had any problems other than the occasional T3 timeout.

Today, my wife is unable to load any page and she says the Cable light on the modem is blinking. I will call Cox once I'm off from work, but I just wanted to see if anyone understood any of these errors so I can have a starting point.

Time Level Description
Thu Oct 29 10:55:12 2009 Critical (3) No Ranging Response received - T3 time-out

Thu Oct 29 10:54:49 2009 Critical (3) No UCD's Received - Timeout

Thu Oct 29 10:54:16 2009 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...

Thu Oct 29 10:53:46 2009 Notice (6) TLV-11 - unrecognized OID

Thu Oct 29 10:53:37 2009 Error (4) ToD request sent- No Response received

Thu Oct 29 10:53:34 2009 Critical (3) DHCP WARNING - Non-critical field invalid in response.

Thu Oct 29 10:53:15 2009 Critical (3) No UCD's Received - Timeout

Thu Oct 29 10:54:50 2009 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/Q...

Thu Oct 29 10:52:09 2009 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...

Thu Oct 29 10:51:37 2009 Notice (6) TLV-11 - unrecognized OID

Thu Oct 29 10:51:28 2009 Error (4) ToD request sent- No Response received

Thu Oct 29 10:51:25 2009 Critical (3) DHCP WARNING - Non-critical field invalid in response.

Thu Oct 29 10:51:14 2009 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...

Thu Oct 29 10:50:43 2009 Notice (6) TLV-11 - unrecognized OID Time Not Established Error (4) ToD request sent- No Response received

Thanks so much!
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madden2k5 @ 29th Oct 03:02PM:
Re: [AZ] Ton of weird errors.

What kind of modem do you have?
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anon @ 29th Oct 03:24PM:
Re: [AZ] Ton of weird errors.

Oops, that would help right? Haha, sorry here it is:

Scientific-Atlanta Webstar 2100

It's a cheap modem, so perhaps it's time to replace it.
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madden2k5 @ 29th Oct 03:31PM:
Re: [AZ] Ton of weird errors.

Well i would def get a new modem webstar are known to be crap, and i would replace it. it is however a supported modem still, here is list of cox supported modems. Motorola seems to have the best modems imo. Also can you pull up signal levels on that modem?

Ambit 60678EU
U10C018

Cisco
DPC3000

D-Link
DCM-202

Joohong SL2810

Linksys
BEFCMU10 v3
BEFCMU10 v4
WCG200
WCG200 v2
CM100

Motorola SB5100
SB5101
SB5120
SBG900
SB6120

RCA DCM315R
DCM425

Scientific Atlanta DPX2100
DPC2100

SMC SMC8004
SMC8013

Terayon TJ715
TJ715x

Toshiba PCX2600

Zoom 5241
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AZHSISUPPRT2 @ 1st Nov 10:51AM:
Re: [AZ] Ton of weird errors.

twittledee,

Looking at the logs you posted I'll try to explain each one for you.

T3's normally occur on the downstream path after the modem has established communication with the CMTS (Cable Modem Termination System) during what is called station maintenance. The modem negotiates it's upstream power levels (transmit levels) and waits for a response from the CMTS. After 200ms if the modem has not received a response the modem encounters a T3 timeout. The modem then boosts its transmit levels again thinking that the CMTS cannot "hear" it until it can receive a response.

UCD's are Upstream Channel Descriptor. These messages are sent from the CMTS on the downstream path basically telling a modem what upstream frequency it needs to be on.

The next error "Received Response to Broadcast Maintenance Request,..." is known as a T4 timeout. This sort of timeout can sometimes indicate possible upstream issues such as contention (competition for bandwidth with other modems). Periodically, the CMTS will send out "keep-alive" messages to the modems during their maintenance cycles. The error indicates that it received that broadcast packet, but due to unknown reasons it was not able to transmit a response (But no Unicast opportunity received). Sometimes this can be due to the amount of traffic on the upstream channel, upstream utilization, things of that nature. There are numerous possibilities as to why the modem was not able to transmit back. Once a modem encounters 16 T4 timeouts in a row the modem will reset its connection.

The next message is a normal message regarding the Organizaional Identifier (OID).

ToD stands for Time of Day. When the modem has established communication with the CMTS it accesses a TFTP server (Trivial File Transfer Protocol server) where it will obtain an IP address from the DHCP (Dynamic Host Configuration Protocol) server and syncs its time with the CMTS, hence the Time of Day request.

The next log entry "DHCP WARNING - Non-critical field invalid response," sometimes will occur during a DHCP lease cycle. DHCP clients request an address on startup and when they are approaching the end of their address lease period. When a client does not have a current lease, it broadcasts a DHCP discover message on its local network segment. All DHCP servers on the network segment copy this message, and respond with a broadcast message announcing that they have an address available. The requesting client chooses one of these offers, usually the first one it receives, and broadcasts a DHCP request message indicating that it has selected that server's offer. While a server is awaiting the client's selection, it can (and should) reserve the offered address so that it is not offered to another client in the meantime. The DHCP server then replies to the request message with a DHCP acknowledgement message which includes the client's IP address, subnet mask, default gateway, and other configuration information.

DHCP provides option fields to allow the client to request and obtain vendor-specific configuration information from the server. This error indicates that one of those options fields were invalid.

The last log entry to address is the "SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing and FEC Synchronization Framing. The CMTS periodically broadcasts a basic set of instructions used by all modems. This instruction set must be used by the modem to enable any further communication with the CMTS. QAM (Quadrature Amplitude Modulation) is the form of digital modulation used primarily in transmitting downstream data signals. During its scan, the modem must locate and synchronize with the QAM-64 or QAM-256 carrier that contains data necessary for modem operation. This synchronization is commonly referred to as QAM lock.

FEC (Forward Error Correction) places overheard or parity bits in the data stream to help identify and correct errors that may occur when data is transmitted through the network. During the modem's initialization process it must synchronize with these FEC protocols so that the FEC system can correct errors. Cable receivers also use this method of error correction. This can also be associated with PreFEC BER (Bit Error Rate[or Ratio]) and PostFEC BER.

So to sum up many of these errors are common which you will see frequently. The main errors to watch out for in my opinion would be the T3, T4, QAM/QPSK symbol timing and FEC synchronization framing. These could potential point to some signal issues which most likely need to be addressed by a technician.

Thanks,

Chris@Cox Communications Arizona
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Guzzler @ 1st Nov 11:06AM:
Re: [AZ] Ton of weird errors.

Wow! Finally a decent explanation of common modem errors, this should be put in a FAQ (if it isn't already).

Thanks!
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jsmiddleton4 @ 1st Nov 12:58PM:
Re: [AZ] Ton of weird errors.

"So to sum up many of these errors are common which you will see frequently."

While that is 100% true what I consistently point out is context. If I am having absolutely NO errors ever in my logs and have not routinely had any errors and then all of the sudden error messages start showing up, just because the error messages are generally common the fact that all the sudden I am having them is significant and can not be dismissed because they are "common".

Which is what is done all too often.

It is a sudden change that is worthy of investigation.

If I regularly have a few errors and I continue to regularly have the same few errors, that would be considered "normal".

I have almost no error messages and all of the sudden I start having "common" errors, well that does not mean it is ok.

Change means more than if the error messages are "common".

In my book a sudden change is enough to warrant further investigation and not be dismissed.

However that is not often the case according to the book of Cox nor some who frequent this forum.
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kv2009 @ 1st Nov 07:21PM:
Re: [AZ] Ton of weird errors.

Wow that was a great explanation. I always wondered about a few of those errors so this explains them quite well. Thanks for that! :)
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No_Strings @ 1st Nov 09:55PM:
Re: [AZ] Ton of weird errors.

said by Guzzler :

Wow! Finally a decent explanation of common modem errors, this should be put in a FAQ (if it isn't already).

Someone did.
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AZHSISUPPRT2 @ 2nd Nov 04:36AM:
Re: [AZ] Ton of weird errors.

jsmiddleton4,

I would just like to clarify; the statement about some errors being common. This was in reference to errors that are not critical to the current situation.

If you see errors that were mentioned, as the most critical, start popping up then it would warrant an investigation in relation to connectivity issues. In twittledee's case this issue is with connectivity.

The most critical errors will depend on the situation, but in twittledee's case, as was mentioned the most critical errors would be pertinent to this specific issue. There will never be a modem log (at least in my experience) that does not encounter some type of error frequently. If you have an example of a modem log with no errors I'd be interested to see it for learning purposes.

When reviewing modem logs you should look for things, such as the time stamp, to verify if the problem occurs at a certain time of the day or if it's constantly occurring, etc. There are many system errors that are not necessarily "life threatening" to a modem unless receiving them in an over-abundance then you may see some issues. In order to troubleshoot via modem logs you would need a longer time table of logs than the one posted. This would help determine if there is a pattern.

No where in the statement was there a comment made that just because the errors may be common that they shouldn't be looked into. It was simply a statement that many errors will be frequent, but this will not necessarily cause a modem to lose connection.

The suggestion I would recommend for twittledee would be for a technician to come out to the home, in order to troubleshoot the connectivity issues. We just can't look at a modem log and then pick a random place in the cable plant to start troubleshooting. We must start from the home and then track it back through the cable plant should the issue not reside at the home.

Hopefully this helps to clarify what was meant in the summary of twittledee's modem logs. Knowing what the errors mean is half the battle of knowing whether it would apply to the current situation.

Thanks,
--
Chris@Cox Communications Arizona
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jsmiddleton4 @ 3rd Nov 10:54AM:
Re: [AZ] Ton of weird errors.

"then it would warrant an investigation in relation to connectivity issues."

I agree. All I am saying is what happens in practice is folks post their logs, those errors are there, they are told there is no problem because those errors are "normal" or "expected" or "boot up noise".

When the only way one can judge if the log errors indicate something needs to be further investigated is to put the log in context by asking, "What do you usually see in your log?"

If usually the log is clean, or mostly clean as Billy what's his name said in the Princess Bride, then regardless of the errors being "benign", something is up. And the something needs to be checked.

The sudden change is the issue.

And around here, the m.o. is to dismiss the import of sudden change by tossing around "its normal" dismissively all too often.
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