Painfully, but not enough to make Ivan stop. It draws a small shiver from him, even, and there's a quick moment were Ivan pauses to let his breath out; this isn't about him, he never has this reaction to his clients anymore, he'll get over it -- he's sure. It doesn't last for anything longer than a half a second before he starts again, bobbing his head in shallow movements. It won't work, though, he can tell the other man wants to move.

Reluctantly, Ivan pulls his head away. Although not without dragging his tongue up David's cock one last time, or mouthing over the head of it. Right, time to refocus.

"If you want to move," Ivan starts, voice rough and low, "I can show you a way you can." It's a odd sort of shock to realize that he knows David won't purposefully try and choke him, or use this an excuse to get off and not learn something.