Re: ADSL upload affecting download speed. Is bandwidth lost?

Your ADSL uses what is called full-duplex communication.  An easier 
analogy would be how a cellular telephone works vs a CB radio.  With a 
cellular telephone, any two parties can speak at the same time without any 
interruption in service or performance.  However, a CB radio operator must 
wait until the other party has finished speaking, or else, communication 
becomes cut-off.  This is because on a cellular telephone, when you speak 
into the handset, you are using one particular frequency while the 
listening part comes through a different frequency.  A CB radio uses only 
one frequency.  xDSL uses more than one frequency.

Therefore, when they rate your system at 256kbs/sec down & 128kbs/sec up, 
that means you have a "total" of 384kbs/sec "available", in essence. 

On a side note, when you do download files, there is some small amount of 
packet data sent back for control purposes, thus it does, theoretically, 
eat into your available upload bandwidth, but the amount of data sent is 
small, so in practice this would be hardly an issue except for unusual 
circumstances.  Same situation happens when you upload a file; packet data 
is sent back to your system, eating away at your d/l bandwidth.