I'm trying to understand how tor multiplexing work. I went through all their design documentation and original research paper, but there is very little mention of it. Examining Tor source code, didn't do much.
My main question, what is being multiplexed, where does it happen, and how is it happening?
Is it at Tor client? If so, what is being multiplexed? Is it the connections? or is it streams belonging to same circuit? is multiplexing always guaranteed? Or is it governed by some conditions?
I'm asking this, because as I far as I can see from the code, streams are being written to circuits as they are received from the browser.
Any help, clue or references is much appreciated.