I have residential Comcast cable modem broadband internet with typically 6Mbs download and 300Kbs upload.
When i am uploading(FTP) a large file, download bandwidth drops to the 400-500Kbs range (less than 10% of upload-idle state).
My understanding was that a cable modem is full-duplex and can deliver (almost) full typical bandwidths simultaneously.
I do have a switch (1000T) in between, but i don't think this is the culprit since at no other file transfer time(combination of directions or traffic) just between computers in our office does any degradation happen that is not normal(explainable) "sharing" of bandwidth for the files being transferred.
Thus it's not related to processor speed (since 1 computer up and another computer down slows the download for the down) (Core 2 duo E6600)
Other observation: always when uploading anything to the internet (FTP), web radio hiccups every 2-3 seconds, thus indicating dropped packets due to download bandwidth
Any ideas? Of course Comcast just says it's my computer, or another time they said they do not guarantee bandwidths (which they do not).