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sortofageek
Premium,Mod
join:2001-08-19
Valhalla Dr
clubs:
 ·Comcast
Host:
Team Helix
Distributed Comput..
Linksys
Comcast HSI
Comcast Cable TV
1 edit | reply to TechnoScott
Re: 3 Years of Upload Dropping - Severe Packet Loss
Interesting. I have always seen the T3 timeout messages in my log, but haven't actually been able to associate them with any issues.
quote:
Time Priority Description
2008-09-22 15:59:55 critical SYNC Timing Synchronization failure - Failed to acquire FEC framing
2008-09-04 00:37:47 critical No Ranging Response received - T3 time-out
2008-09-04 00:37:35 critical SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing
2008-09-04 00:37:33 critical No UCD's Received - Timeout
2008-09-04 00:29:40 critical Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 timeout
2008-07-27 13:55:22 critical Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 timeout
2008-07-27 13:54:54 critical SYNC Timing Synchronization failure - Failed to receive MAC SYNC frame within time-out period
2008-07-03 10:31:51 critical No Ranging Response received - T3 time-out
2008-07-03 09:26:07 critical Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 timeout
2008-07-03 09:25:39 critical SYNC Timing Synchronization failure - Failed to receive MAC SYNC frame within time-out period
What problems do they cause and what is done to fix them? I'm obviously not asking for a detailed step by step how to ... just wondering, in general, what a tech needs to address to fix a T3 timeout. New cables? New modem? New splitters? Something beyond the drop to the house?
--
Join Team Helix * I am praying for these friends . | |
EG
Ho Ho Ho
Premium
join:2006-11-18
Union, NJ | Is that a Moto Surfboard sorto ?
They have a history of being quite the hypochondriac concerning the error entries that they log.. | |
sortofageek
Premium,Mod
join:2001-08-19
Valhalla Dr
clubs: | No, it is the Linksys BEFCMU10 Ver. 4. | |
netcool
@comcast.net
 from:
sortofageek 
| reply to sortofageek
Explanation: The cable modem sent a Ranging Request (RNG-REQ) message as part of its initial ranging process, but did not receive a Ranging Response (RNG-RSP) message from the CMTS within the T3 timeout period. The cable modem will adjust its upstream transmit power and send another RNG-REQ message, up to the maximum of 16 successive attempts, or until it reaches the maximum transmit power level. This error message is DOCSIS event message is R02.0, Ranging Request.
Recommended Action: No action is needed because it is normal for a cable system to occasionally lose MAC-layer messages, especially when multiple cable modems transmit RNG-REQ messages at the same time. | |
funchords
Hello
Premium,MVM
join:2001-03-11
Washington, DC | Why the "critical" label? | |
CUBS_FAN
Next Year Again..
join:2005-04-28
Chicago, IL | Just to keep you on the edge of yer seat or another scare tactic 
Well explained Netcool, makes me less worried about what unusual things I see in my modem logs. | |
EG
Ho Ho Ho
Premium
join:2006-11-18
Union, NJ
| reply to netcool
said by netcool :
Explanation: The cable modem sent a Ranging Request (RNG-REQ) message as part of its initial ranging process, but did not receive a Ranging Response (RNG-RSP) message from the CMTS within the T3 timeout period. The cable modem will adjust its upstream transmit power and send another RNG-REQ message, up to the maximum of 16 successive attempts, or until it reaches the maximum transmit power level. This error message is DOCSIS event message is R02.0, Ranging Request.
Recommended Action: No action is needed because it is normal for a cable system to occasionally lose MAC-layer messages, especially when multiple cable modems transmit RNG-REQ messages at the same time.
I've seen this "quote" before.... | |
netcool
@comcast.net | Yes, google is good. It's a quote I pulled from an old thread here but I have seen pretty much the same thing in Cisco's documentation. | |
netcool
@comcast.net
from:
sortofageek
| reply to funchords
said by funchords :Why the "critical" label? These are more akin to debug messages as I understand it.
»www.faqs.org/rfcs/rfc2669.html | |
Pingmeister
| reply to albie81
After reading all of this, I have no reason to think that the problem is not RF related. You say that connectivity is intermittent, and that when connectivity is OK, downstream speed is good, upstream is poor, and this with multiple cable modems. If you have disconnected the incoming cable at the house, connected the cable modem directly to that, and still had the problem, everything from that point inward has been eliminated.
Thinking about RF - in my case, my cable modem receives downstream at 723MHz, which will be far less susceptible to ingress, loss and other bad things than the return signal from the modem at 31MHz. Smaller packets such as ACKs returned during a download probably have better luck making it to the other end of your cable. If it would be me, I would want to know if there are any serious sources of noise (or legitimate RF) nearby causing ingress distress on your (I make the assumption that your return signal lies between ~25MHz and ~50MHz, check modem status page to see) 31MHz signal from your cable modem. Do you have any CBers (27MHz) nearby who may be running illegal amplification? Perhaps an old paging system or other transmitter (Fire, EMT, etc.) or harmonics from an HF ham operator? Or maybe, plain old noise that is loud enough at 31MHz to cause issues to you. As a ham operator, I have receivers that can help me pinpoint sources of noise. I realize that this may not be practical for you, but I'm just throwing ideas out there, so maybe you can come up with anything at all. My cable modem status page tells me what the basic downstream and upstream frequencies are.
Frequency 723000000 Hz Locked
Signal to Noise Ratio 35 dB
Power Level -13 dBmV
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
Upstream Value
Channel ID 2
Frequency 31000000 Hz Ranged
Power Level 52 dBmV
Your signal levels are reasonable, but the *quality* of your return signal is apparently very poor. Without actually being where you are, I would bet $$$ that your problem will end up being caused by a strong source of noise (or legitimate RF) from ~25MHz to ~50MHz or so, and/or less than optimal cabling.
In any case, these are just my thoughts, and good luck getting things fixed. | |
albie81
Premium
join:2005-01-04
Mount Laurel, NJ
| reply to albie81
UPDATE:
On Monday, Sept. 22nd a tech came out to do some investigation. (He brought another tech with him, and a 3rd tech showed up shortly after they arrived with a bucket-truck.)
I explained to the tech that the problem seems to be worse when the weather is bad. (very cold, or rainy, or snowing, or windy etc.) He said that was good information to have, because that could indicate that there is a cracked/damaged connection somewhere in the loop which is being affected by weather, and introducing noise to the system. The tech also said that he had been monitoring my connection, and has seen my problem happen, when my upload drops out, because the Signal-to-Noise ratio goes outside of operating limits.
The techs started at one end of my street and inspected each "ped"... The tech came back and said that he marked several nodes for repair the following day by line-crews, and they replaced a connection on an over-head line which is at the end of my street (which is past my connection point, but he said noise introduced there can loop through the system.)
The line-crew was scheduled for yesterday (Tuesday, Sept. 23rd) and I am assuming that they were out to fix was marked by the techs the previous day.
TODAY: the problem is still cranking strong. Connection is dropping pretty badly.
Left a voicemail for my contact at Exec. Support, who is out of the office today, so I assume I will hear from her tomorrow.
--
"What happens when the clock reaches 999?"........ "Nothing. You just suck." | |
TechnoScott
Premium
join:2003-03-25
00000
| reply to sortofageek
OK, I'm going to explain the T3 phenomenon in real English with phrases everyone can understand in an effort to help the original poster get this problem solved. Here goes:
Modems are in a sense, insecure devices. If you think about forward and reverse path stability, the forward path (going to the modems) is very robust. Even in the worst of the worst cable systems, average sweep techs can keep 256QAM channels running. Above 50MHz life is usually good in the cable system unless there is rampant ingress or damaged cable. There are obviously more problems out there than that but for the most part, with error correction, 256QAM is easy to maintain.
Now, onto the return path. There are many different issues that go on in the return path. Many of those issues are VERY different than what happens in the forward spectrum and many are VERY difficult to find. The way I train and teach technicians is to read between the lines when looking at return path. Packet testing, modem logs, and spectrum analyzers in the return path (or Pathtrak if you have it) are crucial. Some of us are using QAM generators in the return to look at return path quality too.
Return path problems can be broken down into a few different categories.
1. Return noise: noise that comes from homes, noise that comes from plant, and noise that comes from both. I'm talking about crud from tv's, splitters, and inside wiring. That stuff comes from homes. The noise that comes from the plant comes in the form of CPD, impulse noise, and another condition we refer to as elevated noise floor. Noise is a major issue as it causes lower signal to noise ratios in the return as well as bit errors. Elevated noise floor and CPD is nearly always a connector issue. It can be a severe kink in the cable but it is usually caused by corrosion, loose fittings, and or loose seizing mechanisms.
2. Attenuation problems and unity gain: cable systems must have their unity gain set in the return. This means that every amplifier station from the last active all the way into the node (in the reverse) needs to be set so that the amplification is the same at every station based on cable distance and loss. This keeps modem transmit powers at a predictable level and it also minimizes distortions. This is a crucial part of return setup as it really makes a huge impact on carrier to noise in the return path.
3. Timeouts and bit errors: Now we are getting into the meat of the T3 timeout issue. I will explain what a T3 timeout is in a minute but for now I need to go into the idea of bit errors in the return path. You can look at noise all you want but you can have a node that has NO noise in the return that has constant upstream problems. Not every impairment in the return is related to noise. Some are but some aren't. Many maintenance techs only look at noise and unity gain in the return but there is MUCH more to look at. If modems are sending traffic back to the CMTS in the return and something happens that causes the data to be lost, you may never get to see that... sometimes return impairments occur that cannot be seen. If the RF never makes it past an amp then you can't see it in a spectrum analyzer and the CMTS can't see it either. This is what I mean by reading between the lines. T3 error messages are one way to determine that this is happening. Especially when nothing else can be found.
Now that I have gone through all of that let me explain the T3 timeout to you and explain the repair procedures.
Modems are constantly being talked to by the CMTS. As I explained earlier, the forward traffic is very robust. Return traffic is not so robust. So, here goes. This is what the station maintenance messages roughly look like.
CMTS talks to modem and basically says, "hey, hows it going?"
Modem knows this. Modem attempts to reply, "pretty good"
CMTS THEN SAYS BACK TO THE MODEM, "OK, cool, talk to you later."
Modem then continues about its business. At this time, transmit power is being adjusted in .25 dBmV increments and some other maintenance actions are occurring.
IF the modem is interrogated, and replies BUT the CMTS does not reply back with the, "OK, cool, talk to you later." message then the modem says, "hey, that's wierd, the CMTS didn't hear me." AT THAT TIME THE MODEM LOGS A T3 EVENT in the modem log. If the modem goes 16 station message periods with a T3 timeout occurring then the modem WILL reset itself in hopes of finding a better upstream channel. I have seen this happen in virtually split nodes.
According to Cisco, the period of time (T3) is equal to 200ms. In computing, 200ms is A LONG TIME. An earlier poster said that nah, nothing's wrong with a few T3 timeouts. I would agree that 1 or 2 in a log is ok. A log full of them is a major problem.
Now, as for fixing them? You have to basically physically touch and or inspect every fitting from the affected modem back to the nearest amplifier and if that isn't enough, in some systems it may mean inspecting and tightening every fitting all the way back to the node. Obvious issues like noise and unity gain problems are the first place to start but tight connectors are key. When you have a 100% impedance matched, tight plant with minimal noise then you simply won't have any T3 timeouts. One more thing to note... T3 timeouts occur when a modem is registered, T4 timeouts occur when modems are trying to synchronize.
A really great descriptive technical document on this subject can be found at »www.cisco.com/en/US/tech/tk86/tk···b1.shtml
Hope this is clearer than mud for you all.
Scott  | |
netcool
@comcast.net
| said by TechnoScott : One more thing to note... T3 timeouts occur when a modem is registered, T4 timeouts occur when modems are trying to synchronize. A really great descriptive technical document on this subject can be found at » www.cisco.com/en/US/tech/tk86/tk···b1.shtml I think you have the T3's and T4's mixed up, per that website:
T3
200 msec
The time to wait for a RNG-RSP during ranging.
T4
30 sec
The time to wait for a station maintenance interval to perform station maintenance ranging.
So T3s would occur during the ranging process while the T4s would occur while the modem is sync'd. | |
TechnoScott
Premium
join:2003-03-25
00000
| I have been wrong before... but in this instance I think I am correct.
»www.cisco.com/en/US/docs/cable/c···k_a.html
The CMTS allocates two basic types of contention slots on the upstream:
•Initial ranging slots that CMs use during their initialization phase to join the network. When the CMTS receives an initial ranging request from a CM using this kind of slot, the CMTS subsequently polls the CM, and other operational CMs, in unicast, noncontention station maintenance slots. | |
funchords
Hello
Premium,MVM
join:2001-03-11
Washington, DC | reply to TechnoScott
This is the kind of stuff that makes DSLReports great! | |
albie81
Premium
join:2005-01-04
Mount Laurel, NJ
| reply to TechnoScott
While I understood only about 25% of that.... I know for a fact that the people I am working with in Executive Support are following this thread, (or were at some point) so maybe some of this info will get passed along to the techs? (without me having to murder the technical details by trying to recite it with my limited knowledge.)
I can't thank everyone who's provided input and support in this thread enough.
Hopefully Comcast will be able to resolve this issue soon.
--
"What happens when the clock reaches 999?"........ "Nothing. You just suck." | |
jammmin
join:2000-12-14
Upper Marlboro, MD
| reply to albie81
I had comcast for about 7 years with constant problems that were never totally resolved. I spend many hours over the phone with little resolution.
When FIOS came to my area recently, I switched in a heatbeat and all my 7 years of internet problems were gone immediately.
I am 100% happier now with FIOS internet
1. No throttling
2. No congestion
3. Faster internet
4. No downtime
5. No caps
Its simple folks. Switch to FIOS if you can get it. The years of Comcast being my only internet provider gave me heartburn | |
CUBS_FAN
Next Year Again..
join:2005-04-28
Chicago, IL | FIOS is impossible in the Chicago area.. Perhaps whenever U-Verse arrives and I decide to switch to them am I able to sing a happy song like you. | |
albie81
Premium
join:2005-01-04
Mount Laurel, NJ
3 edits | reply to jammmin
said by jammmin :I had comcast for about 7 years with constant problems that were never totally resolved. I spend many hours over the phone with little resolution. Well.... I lost track a LONG time ago, of how much time I have spent dealing with this problem. So, let's be conservative, and say, forget the last three years, and just focus on the last 4 months, when I have been pushing VERY hard to get this resolved...
In 4 months, I have probably averaged 2hrs a week in dealing with techs, support, emails, phone calls, detailing everything in this thread. (That is a conservative average, I am sure it's more, but I'll go on the low-end to be safe.)
Now, in my professional environment: I work for an Engineering firm, in which my time is billed at $90/hr. So... if we equate that, saying that my time is worth that much, to the amount of time I have WASTED dealing with Comcast.... 2hrs/week for 4 months = $2,880
That time/money value is equivalent to approximately FOUR AND A HALF YEARS of Comcast HSI service invoices.... in the space of four months time... which is especially ironic now... since I received a service bill in the mail yesterday.
said by jammmin :I am 100% happier now with FIOS If it were available in my area, I would have switched years ago. | |
albie81
Premium
join:2005-01-04
Mount Laurel, NJ
| Today, after having several attempts to contact Exec. Support go unanswered... I sent this to my County's newspaper:
said by EMAIL TO COUNTY TIMES :To Whom It May Concern, I am not sure if I am directing this to the appropriate place or not, so please bear with me, as I have a tendency to be long-winded. (That’s an understatement at best.) For the past 3 and a half years, I have been fighting a seemingly unending battle with Comcast over quality of service issues, as it directly relates to television and internet services. I am entirely at my wit’s end, and do not have the slightest idea where to turn to get some help in my struggle. (I know I am not alone in my quest to simply receive the service that I have gladly paid for, and haven’t yet received.) To make a VERY long story, VERY short, for whatever technical reasons, the broadband signal provided by Comcast within my development (I am unsure of how many residences are affected) is dirty. It had a major impact on television services which I eventually dropped for satellite. I had VoIP phone service which I had to cancel, as it was unusable. As it stands now, I can BARELY use my internet connection, because of the dirty signal. I cannot online game, chat, upload photos and many times cannot pay bills, etc. It’s especially heart-warming to sit at the computer with my 5yr old son, who is trying to play computer games on sites like Nick Jr. and Noggin, and have him ask me why the computer’s not working and “daddy” has to tell him that he can’t fix it. Access to the internet in our society is no longer a LUXURY. It’s a function of LIFE. A function which I am effectively robbed of by Comcast’s apparent ineptitude to resolve an ongoing, documented hardware issue. And to make matters better, I have no other viable, equal broadband option available to me. Instead of continuing to be extraordinarily long-winded, I will simply direct you to a thread, which has documented in great detail, both conversationally, and technically, the ongoing problem, which was posted on the internet community “BroadBandReports.com” which, whether you know or not, is a large, well-respected online tech community, that I have been a member of since 2005. This is actually not the first time I have posted on this site regarding my troubles, but it has received the most attention/feedback. This post originated on July 14th 2008, as of right now, it has been viewed by unique visitors 2,470 times. That is a lot of public interest in my own small, personal problem. » 3 Years of Upload Dropping - Severe Packet LossI have been informed by a member of that site, whose opinion I respect very much, that best course of action in my current situation, is to contact local news sources and local “Consumer Reports.” I don’t have the slightest idea where to begin, and if any local agencies or news sources really even care, or who/where is the most appropriate place to start. I would appreciate ANY input that you or colleagues have to offer, and I apologize again if this is directed to the wrong place/individuals, but I am at a total loss. We will see I suppose.......
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"What happens when the clock reaches 999?"........ "Nothing. You just suck." | |
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