I have only ever done this once and it wasn't so much about the dom/sub asepct of it. One good friend, almost a polymorous friend...when we got together it was always a mix of tantric type sex and animalistic sex. There was a lot of nuzzling and biting along with the normal vanilla stuff. She had been traumatized by a previous guy so any physical contact was initially very difficult...few days we got over that...anyways we shared a shower after being out all day exploring and we began to get physical. I had to stop her because I really had to take a piss, one bathroom hotel room...she said no dont leave and whispered in my ear "mark me, make me yours and protect me." Tough to give the impact of that act justice here but there is a connection there that will never go away.