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Re: Intermittent Download Speed, extremely slow upload speed

New Poster

Re: Intermittent Download Speed, extremely slow upload speed

Hi,
I have the same issue, upload is fine but my 10Mbps upload has been cut in half. I noticed this today and rebooted the modem. I’m also seeing t3 errors in my modem logs, cm600. I’m also including my signal levels. Nothing has changed on my lan in 2 years, except for firmware updates on the ubiquiti edgerouter-x running smart queue qos.

My conclusion in this thread at dsl reports in the xfinity subforum, https://www.dslreports.com/forum/r32245139-issue-with-uploads-on-comcast, is that my upload provisioning is 5Mbps rather than the 10Mbps I pay for!
Please help.

2019-01-06, 08:43:55 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=b0:7f:b9:6a:c6:b0;CMTS-MAC=00:01:5c:9e:dc:5f;CM-QOS=1.1;CM-VER=3.0;
2019-01-04, 10:53:35 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=b0:7f:b9:6a:c6:b0;CMTS-MAC=00:01:5c:9e:dc:5f;CM-QOS=1.1;CM-VER=3.0;
2019-01-04, 10:53:33 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=b0:7f:b9:6a:c6:b0;CMTS-MAC=00:01:5c:9e:dc:5f;CM-QOS=1.1;CM-VER=3.0;
2019-01-04, 10:53:30 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=b0:7f:b9:6a:c6:b0;CMTS-MAC=00:01:5c:9e:dc:5f;CM-QOS=1.1;CM-VER=3.0;
2019-01-04, 10:53:29 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=b0:7f:b9:6a:c6:b0;CMTS-MAC=00:01:5c:9e:dc:5f;CM-QOS=1.1;CM-VER=3.0;
2019-01-04, 10:53:26 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=b0:7f:b9:6a:c6:b0;CMTS-MAC=00:01:5c:9e:dc:5f;CM-QOS=1.1;CM-VER=3.0;
2019-01-04, 10:53:25 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=b0:7f:b9:6a:c6:b0;CMTS-MAC=00:01:5c:9e:dc:5f;CM-QOS=1.1;CM-VER=3.0;
2019-01-04, 10:53:24 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=b0:7f:b9:6a:c6:b0;CMTS-MAC=00:01:5c:9e:dc:5f;CM-QOS=1.1;CM-VER=3.0;

then some more of these sync errors going back into december. i have rebooted the modem a week ago because i noted a large number of correctable errors. here's the strengths and errors after rebooting a few minutes ago:
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 16 561000000 Hz 0.1 dBmV 38.5 dB 1 0
2 Locked QAM256 1 465000000 Hz 1.7 dBmV 39.7 dB 0 0
3 Locked QAM256 10 525000000 Hz 0.9 dBmV 39.3 dB 1 0
4 Locked QAM256 11 531000000 Hz 0.6 dBmV 39.1 dB 0 0
5 Locked QAM256 12 537000000 Hz 0.5 dBmV 39.0 dB 2 0
6 Locked QAM256 13 543000000 Hz 0.2 dBmV 38.7 dB 1 0
7 Locked QAM256 14 549000000 Hz 0.2 dBmV 38.7 dB 1 0
8 Locked QAM256 15 555000000 Hz 0.2 dBmV 38.7 dB 1 0
9 Locked QAM256 17 567000000 Hz -0.1 dBmV 38.5 dB 0 0
10 Locked QAM256 18 573000000 Hz -0.3 dBmV 38.4 dB 0 0
11 Locked QAM256 19 579000000 Hz -0.3 dBmV 38.3 dB 0 0
12 Locked QAM256 20 585000000 Hz -0.2 dBmV 38.4 dB 0 0
13 Locked QAM256 21 591000000 Hz -0.2 dBmV 38.4 dB 0 0
14 Locked QAM256 22 597000000 Hz -0.3 dBmV 38.3 dB 0 0
15 Locked QAM256 23 603000000 Hz -0.3 dBmV 38.2 dB 0 0
16 Locked QAM256 24 609000000 Hz -0.1 dBmV 38.4 dB 1 0
17 Locked QAM256 25 615000000 Hz 0.2 dBmV 38.2 dB 0 0
18 Locked QAM256 26 621000000 Hz 0.1 dBmV 38.2 dB 0 0
19 Locked QAM256 27 627000000 Hz -0.2 dBmV 38.2 dB 0 0
20 Locked QAM256 28 633000000 Hz -0.2 dBmV 37.9 dB 0 0
21 Locked QAM256 29 639000000 Hz -0.3 dBmV 37.9 dB 0 0
22 Locked QAM256 30 645000000 Hz -0.3 dBmV 37.8 dB 0 0
23 Locked QAM256 31 651000000 Hz -0.4 dBmV 37.8 dB 0 0
24 Locked QAM256 32 657000000 Hz -0.5 dBmV 37.8 dB 0 0

Expert

Re: Intermittent Download Speed, extremely slow upload speed

Also post the upstream power levels.



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New Poster

Re: Intermittent Download Speed, extremely slow upload speed

i'm sorry, here they are:

 

Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 3 5120 Ksym/sec 30300000 Hz 48.3 dBmV
2 Locked ATDMA 1 5120 Ksym/sec 17300000 Hz 49.3 dBmV
3 Locked ATDMA 2 5120 Ksym/sec 23700000 Hz 48.5 dBmV
4 Locked ATDMA 4 5120 Ksym/sec 36700000 Hz 48.8 dBmV
5 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
Expert

Re: Intermittent Download Speed, extremely slow upload speed

This may or may not be the root cause of the problem but the upstream power is approaching the high side and may be intermittently fluctuating even higher out of spec. T\If it does, that can cause random disconnects, spontaneous re-booting of the modem, and speed and latency problems.

In a self troubleshooting effort to try to obtain better connectivity / more wiggle room, check to see if there are there any excess/unneeded coax cable splitters in the line leading to the modem that can be eliminated/re-configured. Any splitters that remain should be high quality and cable rated for 5-1002 MHz, bi-directional, and no gold colored garbage types like GE, RadioShack, RCA, Philips, Leviton, Magnavox, and Rocketfish from big box stores like Home Depot, Lowes, Target, Wal-Mart etc. Splitters should be swapped with known to be good / new ones to test

If there aren't any unneeded splitters that can be eliminated and if your coax wiring setup can't be reconfigured so that there is a single two way splitter connected directly off of the drop from the street/pole with one port feeding the modem and the other port feeding the rest of the house/equipment with additional splits as needed, and you've checked all the wiring and fittings for integrity and tightness and refresh them by taking them apart then check for and clean off any corrosion / oxidation on the center wire and put them back together again, then perhaps it's best to book a tech visit to investigate and correct.




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New Poster

Re: Intermittent Download Speed, extremely slow upload speed

well after the service call, i still have an issue with uploads every few days to a week or so.  the only cure is a reboot.  i notice it because my lag when playing COD is horrible.  when it's messed up if i run a dslreports.com speed test, my bufferbloat is horrible b to f.  the ping on upload is from hundreds of milliseconds to thousands!  that's alot of lag.

 

i'm also noticing i'm not getting critical errors in the cm600 logs, but show lots of correctable and uncorrectable errors on the downstream channels.  upstream doesn't show any error accounting.

 

i'm not sure what to do now.

 

any ideas?

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Expert

Re: Intermittent Download Speed, extremely slow upload speed

Uh, Get them involved again until it is fixed right ????



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