Contributor
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25 Messages
Xfinity Internet Service Degraded, Unstable After "Network Enhancements In My Area" On March 30th
SUMMARY OF ISSUE:
(1) I had stable, error-free cable internet service until a recent "neighborhood upgrade" on March 30", when the "upgrade" work caused service to be out for a whole day.
(2) Now, our service logs tens of thousands of uncorrected errors per day across sixteen downstream channels, and is not stable, typically disconnecting several times in each 24 hour period.
(3) Neither our equipment or the single run of cable from the Xfinity demarcation point outside our home to the cable modem has been altered in any way from its formerly working (before "neighborhood upgrade") configuration to the current degraded, unstable configuration.
Given these facts, Xfinity's changes to their system during the "neighborhood upgrade" are very strongly implicated in the problems which I am now requesting they remedy. To convince Xfinity that there is a problem with their system and not mine, I have gathered and report here detailed evidence.
BACKGROUND:
I did not have any cable-based service at this property since I bought it decades ago, but in the last few years have needed additional bandwidth due to increased telework/telecommuting opportunities, as well as a virtually mandatory shift to streaming video services. So I reluctantly switched from my 100% reliable (but slow) DSL internet connection to "Xfinity" cable-based service a few years ago, at which time the company installed a new cable drop (since storms had long ago taken down the old one the previous owners used).
From the start my Xfinity internet service worked well, and was stable for months of up-time without interruption. I never had cable television service, so there are no complications to my internal connection: a single cable runs from the Xfinity connection point at the side of my home directly to a wall plate, connected to a Motorola MB-7420 cable modem.
There are no intervening splitters and/or additional cable runs or amplifiers, and none of my equipment or connections have been altered since the system was stable, (before the Xfinity upgrade work).
A note regarding my background is perhaps relevant: I have degrees in electrical engineering and computer science, and work as a consultant in the field of embedded systems, writing firmware for networking equipment and Ethernet switch gear.
So my complaint here comes from a fairly complete understanding of the basic operation of cable internet systems, having nothing to do with my internal network architecture, routers, switches, WiFi access points and WiFi signal conditions in my home, or anything else that lies beyond Xfinity's system and control.
It only regards Xfinity's responsibility to provide a stable, continuous connection at the cable modem itself.
As I did not change or alter the single cable that runs from Xfinity's feed to my cable modem, and the signal quality problems are all evident at the modem itself, the strongest possible indication that problems with my connection are related to recent changes made by Xfinity in my neighborhood exists.
I am bringing the problem to the attention of this forum because, although the connection still "works" and a cursory check with the Xfiniity "App" or web site will indicates that it is ostensibly "OK", it is no longer stable nor reliable - the connection quality has degraded.
An intermittent connection that drops out several times per day (or even per week) is simply not acceptable, given the nature of my work.
BRIEF HISTORY:
Initially, my Xfinity connection was as reliable as my former rock-solid DSL service was, which was an unexpected and pleasant surprise.
When I first subscribed to Xfinity Internet, I selected a Zoom 5341 cable modem specifically due to its reputation for stability, reliability and trouble-free operation. And both it and the Xfinity service were indeed reliable and trouble-free for a couple of years.
However in January, Xfinity notified me that I would be forced to replace my perfectly functional and trusted Zoom 5341 cable modem with something else by March 13, or I would lose my service, due to an "expired certificate" in the modem.
A brief digression: for those who don't know what a "certificate" is, it is just a cryptographic key set consisting of a "public" and "private" key ("keys" are just big numbers). "Certificates" have "expiration dates", but in a lot of contexts (like in a cable modem or gateway) those dates can be safely ignored, because numbers don't really "expire" and a certificate's date can't affect the security of a cryptographic exchange unless a certificate's private key was actually compromised. Expiration dates are only included in certificates as a caution, so that if a certificate is compromised, it will eventually "age out" of any systems that are unaware it has been compromised and/or "revoked."
At any rate, I selected another top-rated, Xfinity-approved modem - a Motorola MB-7420 - and installed and activated it around March 12 to avoid any service interruption. And initially, the connection to the new cable modem was as reliable as it had been with the previous Zoom unit.
However, I soon received yet another notice from Xfinity on March 29 that they would be "working to enhance the network in my area" starting March 30", and that the system outage would likely last all day.
The outage did indeed last all day, making it difficult to work, and when I got a message that my service should be back on-line at 7:43 PM, initially the connection quality looked OK. (I had to solve another problem caused by some unannounced changes to Xfinity's gateway servers, but that issue was on my side of the network downstream from the modem, and therefore my responsibility to troubleshoot and correct).
Unfortunately, over the last couple of weeks it has become clear that my connection was somehow degraded during the "upgrade", and it is no longer stable or reliable.
That fact is proven by examining the cable modem error logs, where connection problems are recorded and time-stamped. Here, the logs indicate several cable modem reboots (and commensurate internet connection interruptions) due to poor cable signal quality over a single weekend:
Thursday, April 20 8:30 PM
Friday, April 21 12:51 AM
Friday, April 21 5:57 AM
Friday, April 21 5:58 AM
Friday, April 21 6:09 AM
Friday, April 21 8:08 AM
Friday April 21 7:16 PM
Friday April 21 9:09 PM
Saturday April 22 4:04 PM
Saturday April 22 4:37 PM
Sunday April 23 3:37 AM
Sunday April 23 12:28 PM
Sunday April 23 12:31 PM
In addition, the modem status page shows 171,960 corrected and 105,762 total uncorrected errors on 16 downstream channels over 160 hours (9,600 minutes) of up-time, or approximately 11 uncorrected errors per minute. (Detailed error log messages follow).
Considering that all the easy remedies ("reboot/disconnect/power-cycle the modem) have already been done many times, and that:
-> Before Xfinity's changes to "enhance" the network in my neighborhood per their March 30th notice, my connection was stable and consistent.
-> After Xfinity's "enhancements", my connection is no longer stable or consistent.
Xfinity has clearly created a problem that must lie somewhere within Xfinity's system and/or its connection to my home, which only Xfinity can rectify. This assertion is strongly supported by the fact that neither my equipment or cable was changed when the quality of my formerly reliable service declined.
The ONLY changes made were Xfinity's, outside of my home and my control, and the degradation of my service exactly coincided with the date that Xfinity's "neighborhood system upgrade" was performed.
NEXT STEPS ?
Incidentally, I just received notice from Xfinity that there will be another service interruption tomorrow, Monday April 24th in my area, to "correct performance issues."
While by chance this maintenance operation may remedy the problems I've observed and documented here, I don't want to just rely on luck at this point. I've already wasted far too much time trying to obtain and keep basic, reliable Internet service from Xfinity.
So given the facts and history I have provided, how can I get Xfinity to restore my service to its former, reliable state without an endless argument about whose equipment is at fault, instructions to repeatedly reboot and/or re-purchase equipment, etc. ?
As a professional, any service that drops packets and disconnects several times per day or week like the service Xfinity is currently providing is simply unacceptable and useless to me. And dealing with the equipment changes, upgrades and other problems Xfinity caused has been incredibly time-consuming, costly and inconvenient as well.
I need a direct path forward to a solution, not more useless, scripted Tier 1 instructions from offshore customer service agents.
[ Modem error logs showing repeated T3/T4 time-outs and attendant connection losses (14 incidents) follow. ]
Thu Apr 20 20:29:01 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Thu Apr 20 20:30:06 2023 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Thu Apr 20 20:30:38 2023 Critical (3) No Ranging Response received - T3 time-out;
Thu Apr 20 20:31:11 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Fri Apr 21 00:50:22 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Fri Apr 21 00:51:27 2023 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Fri Apr 21 00:51:51 2023 Critical (3) No Ranging Response received - T3 time-out;
Fri Apr 21 00:51:59 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Fri Apr 21 05:57:24 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Fri Apr 21 05:57:24 2023 Critical (3) Unicast Maintenance Ranging attempted - No response - Retries exhausted;
Fri Apr 21 05:57:24 2023 Critical (3) 16 consecutive T3 timeouts while trying to range on upstream channel 1;
Fri Apr 21 05:57:24 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Fri Apr 21 05:57:24 2023 Critical (3) Unicast Maintenance Ranging attempted - No response - Retries exhausted;
Fri Apr 21 05:57:24 2023 Critical (3) 16 consecutive T3 timeouts while trying to range on upstream channel 3;
Fri Apr 21 05:57:36 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Fri Apr 21 05:58:14 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Fri Apr 21 05:58:15 2023 Critical (3) DHCP failed - DHCP Solicit sent, No DHCP Advertise received;
Fri Apr 21 05:58:33 2023 Critical (3) No Ranging Response received - T3 time-out;
Fri Apr 21 05:58:38 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Fri Apr 21 06:07:59 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Fri Apr 21 06:09:04 2023 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Fri Apr 21 06:09:19 2023 Critical (3) No Ranging Response received - T3 time-out;
Fri Apr 21 06:09:40 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Fri Apr 21 08:07:19 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Fri Apr 21 08:08:24 2023 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Fri Apr 21 08:08:36 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Fri Apr 21 12:12:44 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Fri Apr 21 12:12:58 2023 Warning (5) Dynamic Range Window violation
Fri Apr 21 12:13:20 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Fri Apr 21 19:14:31 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Fri Apr 21 19:15:36 2023 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Fri Apr 21 19:15:55 2023 Critical (3) No Ranging Response received - T3 time-out;
Fri Apr 21 19:16:10 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Fri Apr 21 21:07:52 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Fri Apr 21 21:08:57 2023 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Fri Apr 21 21:09:19 2023 Critical (3) No Ranging Response received - T3 time-out;
Fri Apr 21 21:09:26 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Sat Apr 22 16:03:02 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Sat Apr 22 16:04:07 2023 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Sat Apr 22 16:04:21 2023 Critical (3) No Ranging Response received - T3 time-out;
Sat Apr 22 16:04:45 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Sat Apr 22 16:35:57 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Sat Apr 22 16:37:02 2023 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Sat Apr 22 16:37:28 2023 Critical (3) No Ranging Response received - T3 time-out;
Sat Apr 22 16:37:35 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Sat Apr 22 16:37:51 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Sat Apr 22 16:37:52 2023 Critical (3) DHCP failed - RS sent, no RA received;
Sat Apr 22 16:38:04 2023 Critical (3) No Ranging Response received - T3 time-out;
Sat Apr 22 16:38:26 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Sun Apr 23 03:36:23 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Sun Apr 23 03:37:28 2023 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Sun Apr 23 03:37:46 2023 Critical (3) No Ranging Response received - T3 time-out;
Sun Apr 23 03:37:54 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Sun Apr 23 12:26:55 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Sun Apr 23 12:28:00 2023 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Sun Apr 23 12:28:12 2023 Critical (3) No Ranging Response received - T3 time-out;
Sun Apr 23 12:28:16 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Sun Apr 23 12:30:21 2023 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
Sun Apr 23 12:31:26 2023 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
Sun Apr 23 12:31:38 2023 Notice (6) Honoring MDD; IP provisioning mode = IPv6
[ END OF LOG ]
Accepted Solution
user_ata424
Contributor
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25 Messages
2 years ago
In the end, the root cause of the difficulty discussed in this topic was not caused by Xfinity or the new modem that replaced the one I was forced to retire, but by a short patch cable inside my office providing the coax cable feed from a wall jack to the modem.
It turned out that the previous Zoom 5341 8x4 channel DOCSIS 3.0 modem was much more resistant to out-of-band radio frequency and electromagnetic interference (RFI/EMI) than the new Motorola MB7420 must be, so the Zoom was able to work just fine with a short length of RG-59 patch cable (which does not provide as much protection against high-frequency interference as the other common type RG-6 does).
The new Motorola MB7420 modem (also a DOCSIS 3.0 device, but capable of 16x4 channel operation) simply wouldn't tolerate the same cable, or several other RG-59 types I tried. This is likely because the MB7420 has a different design that's more broadband and RFI/EMI sensitive.
Nonetheless, I didn't anticipate that a short length of RG-59 would cause a problem in any case, especially since I had originally tested a RG-6 type patch cable back when I first subscribed to cable internet to see if it improved signal conditions over RG-59, and it did not.
To summarize: replacing an RG-59 patch cable from wall to modem with an RG-6 type definitively solved my uncorrected error, T3/T4 timeout and dropped-connection problems.
So, other customers who recently upgraded or replaced their modems and use a patch cable to connect them to a wall jack, and are now experiencing high uncorrected error counts and/or connection drops may want to look and see what type of cable they have.
If the patch cable is the RG-59 type, they may try picking up a ready-made RG-6 type replacement at a local hardware, home or electronics store for a few dollars, and see if it will solve their problems.
Some DOCSIS 3.1 modems running the highest-rate plans may even benefit from an upgrade to RG-6 "quad-shielded" cable, which while very thick and somewhat awkward to work with, does provide the best protection against interference.
This closes this issue for me.
I provide a final capture of my line statistics as an example of what a solid, nearly-ideal connection typically looks like. There are no entries in the modem error logs, and up until a few minutes ago, there were no uncorrected errors on any downstream channels over almost three days of up-time, and only a handful of corrected errors.
Cable communication systems are design to correct occasional errors, so having a smattering of corrected errors (typically concentrated on a subset of the downstream channels) is fine. Clearly, some sort of radio interference burst recently (and briefly) managed to affect Channel 4, but that is also to be expected from time to time, and no indication of any malfunction.
As long as there are not regularly error messages indicating that the connection was dropped and re-started in the modem error logs, the line quality is fine. More proof is in a ping (ICMP Echo) test I ran over the last three days, in which only four out of 840,199 ping packets were "lost":
840,199/840,195 packets, 0% loss
(Especially since the "lost" packets could be due to any device on the path to the ping target: my PC, the target itself, or any router or switch in between - not necessarily the cable system at all.)
Also note that issues with WiFi or LAN connections to computers, phones etc. downstream from a cable modem (or from the cable modem portion of a combined modem/gateway/wireless access point) have nothing to do with the Xfinity cable network, and must typically be solved by troubleshooting the configuration and operation of the downstream system(s).
To anyone who has been following along, Cheers! I hope this information may somehow help you in solving any connection issues you may be experiencing. :)
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XfinityJessicaA
Official Employee
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330 Messages
2 years ago
Hello @atarascio We appreciate you taking the time to reach out to us today and I know how important it is to ensure you have a stable and reliable internet service. Thanks for all of the detailed information and we'd be happy to troubleshoot to get this resolved. Please send me a DM with your name and full address by doing the following:
Ensure you are first signed in, then you will see an icon at the top right of your page.
From there, click the 'New Message' icon. In the 'To' field, type 'Xfinity Support'.
Type your message in the text area that appears at the bottom of the window and hit enter to send. An official employee, such as myself or whoever is first available, will respond.
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user_ata424
Contributor
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25 Messages
2 years ago
Noted: another connectivity loss just occurred; Monday, April 24 8:02 AM EDST.
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user_ata424
Contributor
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25 Messages
2 years ago
Noted: another connectivity loss just occurred; Monday, April 24 9:08 AM EDST.
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user_ata424
Contributor
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25 Messages
2 years ago
Connection loss is now continuous since last report on Monday, April 24 9:08 AM EDST.
NO notice from Xfinity re: maintenance or outage at this time.
There are absolutely no words for how angry I am with this company and its employees at the moment.
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user_ata424
Contributor
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25 Messages
2 years ago
On the last failure, modem indicators showed down and upstream locks, but no network access.
Assuming that some aspect of the modem provisioning file may have been changed due to maintenance scheduled for this morning, it was power-cycled and connectivity has been restored, and stability monitoring has resumed.
Until the connection is proven stable over a course of days, no resolution is assumed.
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user_ata424
Contributor
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25 Messages
2 years ago
So far, one hour of uptime without errors, signal levels good (but they always were):
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user_ata424
Contributor
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25 Messages
2 years ago
The signal quality has remained good for three hours after presumed maintenance.
Zero errors, zero error log entries, and zero connection drops.
If the signal is now stable, the maintenance operation in the area this morning may have corrected the whole issue.
But I will continue to monitor signal conditions over the next few days, and post my findings (good or bad) here. If the signal remains clean for a few days, the matter can be considered closed.
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user_ata424
Contributor
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25 Messages
2 years ago
22 hours uptime and looking good! Still zero errors, zero error log entries, and zero connection drops - a solid, noise-free connection, so I'm very pleased so far. :)
Upstream transmit power does tend to slowly increase after a cold restart/power cycle, but as long as it doesn't climb too far above 45 dBmV I think it's OK.
Once the connection reaches seven days up-time with no major problems or disconnects, I think we can conclude that Xfinity proactively identified and corrected whatever issue was causing poor signal quality in the neighborhood.
For that I'll be thankful to both the company and their associates, as it demonstrates systems are being actively monitored to spare customers (and agents) the difficult process of reporting and troubleshooting degraded connections.
(Or, other people are much quicker to complain than I am.) :)
[ Current connection statistics follow ]
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user_ata424
Contributor
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25 Messages
2 years ago
There was a brief burst of uncorrectable errors this morning, and one T3 time-out. But that's not necessarily a problem; occasional errors are fine as long as they don't become chronic and there's no discontinuity in the connection.
Note the time logged is EST, there doesn't seem to be an adjustment for EDST so the actual local time was e.g. 10:30 AM.
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user_ata424
Contributor
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25 Messages
2 years ago
Downstream error counters are not logging any additional errors, and more importantly, no more T3/T4 timeouts or disconnects have been recorded in the modem error log. Open media streams, VPN adapters and other connections to the WAN interface the modem services remain connected.
This is what a good connection looks like, if it keeps operating like this day after day. :)
So, I continue to wait and see if the line will remain quiet and connected long-term...
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user_ata424
Contributor
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25 Messages
2 years ago
Good morning to anyone following along on our quest for reliable internet service over coaxial cable. It's definitely better than bongo drums: https://web.archive.org/web/20051228141940/http://eagle.auc.ca/~dreid/
(Courtesy of the Internet Archive). Also look for the autobiographical film "The Bit Player" about the life of Claude Shannon, without whose insights into the fundamental nature of information and logic, modern communications and computation would have probably taken a lot longer to arrive.
At any rate, my connection has been active since Wed Apr 26 6:14 AM EDST, so the total connection up-time since the last connection loss is about thirty hours (the reported modem up-time is not important).
Uncorrected Errors continue to slowly accrue, but since I've not been able to obtain a definitive answer from any source on the Web or within Xfinity as to when the number of uncorrectable errors on a connection constitutes a problem with that connection, all I can say is there has been no huge increase in the numbers; they rose about 33% overnight.
The important thing is that the connection's been maintained for a day so far without dropping, and seems to be providing good performance. A good connection should stay up continuously for long periods of time unless there's an outage or maintenance in the area; that's the baseline performance metric that must be satisfied first.
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user_ata424
Contributor
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25 Messages
2 years ago
OK, this is the kind of thing I can't tolerate - these connection drops. They interrupt any VPN connections or streams I have running, and are totally unacceptable.
The latest was this morning, on Friday April 28 at 4:19 AM EDST. I just happened to wake up right when the failure occurred.
(As noted earlier, the log times are in EST and so off by -1 hour).
Errors also continue to accumulate on all channels, standing at 27,316 as of this moment, a 60% increase in just 19 hours.
All the downstream signal levels, S/N ratios and upstream power levels are good, but the connection still can't go more than a day without dropping.
So something is wrong with the network in this neighborhood and someone from Xfinity needs to come out here and fix it.
Again, my setup hasn't been altered; it worked perfectly for two years until Xfinity came and changed something on the utility poles.
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user_ata424
Contributor
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25 Messages
2 years ago
OK, fellow cable internet fans, what I have discovered on my own and mostly by fortunate chance is that: the brand-new cable modem I purchased recently to replace the working one Xfinity forced me to retire is probably defective, in spite of being top-rated and carrying a two-year warranty.
Physically moving or disturbing the modem (for example, just tapping it) consistently causes the uncorrected error count to spike dramatically. In electronics, this is known as an "intermittent mechanical failure" (there are also "thermal intermittents" triggered by temperature).
Obviously, a problem that subtle is pure Heck for everyone trying to troubleshoot a complicated system.
So, it's my responsibility to replace the bad modem or any defective cabling before I can fault Xfinity, although I'm still not pleased they forced me to replace a working, trusted unit with a new one that could possibly be defective because of an "expired certificate".
Throughout this frustrating process, all the Xfinity people I had contact with were very understanding and helpful. They deserve a lot of credit for their patience in dealing with me and other customers that are unfortunate enough to encounter an intermittent connection problem of this nature.
Once I have procured a new, compatible working cable modem, I'll report the results here, and I'm fairly confident they'll be good. :)
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user_ata424
Contributor
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25 Messages
2 years ago
More information to pass along:
A short coaxial patch cable ran from the wall jack where my Xfinity feed is located to my former Zoom 5341 cable modem. The cable is in fine condition in a furnished area of the house, and never caused any problems, so I re-used it to connect the new Motorola MB7240 cable modem I purchased when Xfinity forced me to upgrade my equipment.
Once I discovered that the modem and/or cable were sensitive to mechanical disturbance, I suspected something might be wrong with the cable first, since it is much cheaper and more convenient to change than the modem. And upon careful inspection, I noticed that the old cable's center conductor or "stinger" was thinner (a smaller wire gauge) than that of several other coax patch cables I have.
[ I have a very large collection of cables and media of all types, as I have lived through many, many generations of technological change. It's quite annoying. But that's a rant for another time. :) ]
At any rate, after replacing the (now) suspect cable with the thin center conductor with another that had a slightly thicker conductor, the cable and modem assembly was no longer sensitive to mechanical disturbances, and seems to maintain a solid, error-free connection even when moved or tapped.
So the new modem is probably not defective, just incompatible with the old cable.
Apparently, the coaxial "F" connector on the Zoom 5341 cable modem maintained a tighter grip on the coaxial cable's center conductor than the newer Motorola MB7240 cable modem does, and so moving or tapping the new modem would cause the old cable's thinner center conductor to vibrate inside the "F" connector, interrupting the connection and causing errors.
This is why any unnecessary equipment change is risky and should never be forced. It's hard to predict how all the different components (including cables) in a complex system will interact, and even small details can cause big problems.
So, with the new patch cable in place, the modem has been cold-started and we are back to zero days, zero hours up-time.
I will continue to monitor the connection quality and report any issues here, but I suspect my intermittent connection problem may have finally been solved. If so, no doubt that will be a huge relief to me, Xfinity and you, patient reader. :)
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