I've noticed that my upstream data rate suddenly dropped by about 20% to 25%. My service is 50 /10. The downstream rate is OK. I first noticed it by periodically running speedtest. I confirmed by reviewing my results at Samknows (I have a Samknows / FCC router configured to test ISP performance). During March 2014, my upload speed was consistently 11.5 Mbit / sec. In April, the upload speed was down between 7 to 8 Mbit / sec. Modem signal is good, three bonded upstream channels between 41 & 43 dBmV. I haven't made any sytem changes that would explain the sudden drop.
Here are the comcast & speedtest results:
http://stage.results.speedtest.comcast.net/result/477453984.png
http://www.speedtest.net/my-result/3428737704
Any suggestions?