Cisco Systems The offer/answer model for SDP assumes that endpoints establish, somehow, the QoS required for the media streams they establish. Endpoints in closed environments typically agree out of band (e.g., using configuration information) which QoS mechanism to use. However, on the Internet, there is more than one QoS service available. Consequently, there is a need for a mechanism to negotiate which QoS mechanism to use for a particular media stream. This document defines such a mechanism.