This document introduce the concept of quality of service in high performance networks like Myrinet, Infiniband or Quadrics. Indeed, thanks to the rise of cores in processor units, the multiplication of processors inside a computer and furthermore the growing number of flows generated by applications, communication libraries had to deal with numerous streams that need to be transfered. Moreover those streams had various requirements (latency, reactivity, priority, ...) that are not usually considered. That's why we propose to integrate in the communication library NewMadeleine, developed into the Runtime team, a strategy of quality of service, that directs flows and offer them a guarantee fitted to theirs needs.