In this specification, we define a framework for identifying RTP Streams with the constraints on its payload format in the Session Description Protocol. This framework defines a new "rid" SDP attribute to: a) effectively identify the RID RTP Streams within a RTP Session, b) constrain their payload format parameters in a codec- agnostic way beyond what is provided with the regular Payload Types and c) enable unambiguous mapping between the RID RTP Streams to their media format specification in the SDP.