Some have suggested that DNS move to TCP, but I don't think that's proper. The nature of DNS lends itself to connectionless, lightweight communication. That said, could the next iteration of DNS implement application-level handshaking?

The reason not to do this at layer 4 is because I, in the several minutes of pondering it, think it could break lots of security devices that track connection state across lots of computers in a network. Make some kind of

  C -> S request  
  C <- S ack 
  C -> S yes  
  C <- S lots of data  
  done

  C -> S request  
  C <- S ack
  C -> S no  
  done