Comcast XFINITY → [Speed] Download speeds are perfect, but Upload is horrid

I have been having a problem for about a week now, where my ping and download speeds are great, but the upload is terrible. Pingtest.net works flawlessly, and speedtest.net works great except when the upload test comes up. It takes several minutes to even start, and the speeds are running about 0.3Mbps when they should be around 7. I have tried several different sites to test, and upload is indeed crap everywhere.

I have a tech coming out on Friday, and I will post my modem (SB6120 w/ 1068 fw) readings when I get a chance.

Has anyone else had a problem like this?

I've had the same problem for over a year or more even. Comes and goes, usually "corrects" itself by the time a truck rolls around and the levels are always "great" Mean Time Between Failures is 25 Days.

I just cancel and reschedule when it happens.

A couple years ago one tech found some "noise" on the upload side and was to turn it into "plant maintenance" but not sure anything came of that.

I do know that my upload pseed is currently about 1 Mbps slower than normal and my Symbol rate dropped to 2.560 Msym/sec which is a precursor to the full on issue you are having.

Channel ID 222 221 223 224
Frequency 597000000 Hz 591000000 Hz 603000000 Hz 609000000 Hz
Signal to Noise Ratio 37 dB 36 dB 37 dB 37 dB
Downstream Modulation QAM256 QAM256 QAM256 QAM256
Power Level 4 dBmV 5 dBmV 5 dBmV 5 dBmV

Upstream

Bonding Channel Value

Channel ID 1
Frequency 29500000 Hz
Ranging Service ID 4328
Symbol Rate 2.560 Msym/sec
Power Level 43 dBmV
Upstream Modulation [3] QPSK
[2] 16QAM

Channel ID 4 6 7 8
Frequency 237000000 Hz 249000000 Hz 255000000 Hz 261000000 Hz
Signal to Noise Ratio 37 dB 38 dB 38 dB 38 dB
Downstream Modulation QAM256 QAM256 QAM256 QAM256
Power Level
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
-2 dBmV 0 dBmV -1 dBmV -1 dBmV

Channel ID 7 8
Frequency 26000000 Hz 32000000 Hz
Ranging Service ID 1249 1249
Symbol Rate 2.560 Msym/sec 5.120 Msym/sec
Power Level 46 dBmV 46 dBmV
Upstream Modulation [3] QPSK
[2] 16QAM
[3] 64QAM
[3] QPSK
[3] 64QAM

Ranging Status Success Success

Your signals look OK. How are you connected? Can you connect directly to the modem and see what happens?

Try a Visualware quality test. You must have Java installed and active in your browser.

Go to »myspeed.visualware.com
Click on the USA
Try to find the yellow pushpin closest to you (hover mouse over one to see the location) and click it.
After the regular speed test loads (yellow/green), click on 'Quality' in the list of tests on the upper right.
Wait for the quality test (red/blue) to load.
Start the test.
You will get additional details about lost or resent packets.

I have tried directly into the modem, and get the same results.

Using that site, I got download of 31Mbps, which is over what I have. The upload is only at .9-1.2Mbps when it should be about 6-7Mbps.

I will get a quality test reading later on today from that site.