I need help with understanding proxy chains fundamentals. I'm using them right now but I would like to know something about software and protocols implementation. So far I don't understand how exactly each hop in chain knows IP of next hop. I suppose that there's is a field in SOCKS frame to which client insert whole path and then each proxy server delete from this his own IP and send frame to next in the list. Could someone explain me how exactly this is implemented in SOCKS and HTTP?