3.1.4.8.3 Media Flow

This section specifies the candidate pair that is used for media flow during processing, as designated by this protocol. Applications can begin sending media after the initial exchange of candidates is finished. Any media sent at this stage MUST be sent using the default candidate pair. However, there is no guarantee that the media will reach the peer at this stage. During the connectivity checks phase, media SHOULD be switched to use the first candidate pair that becomes "Recv-Valid" for User Datagram Protocol (UDP) or "Valid" for Transmission Control Protocol (TCP). This happens even if those candidates have not been exchanged through the signaling channel. After the final exchange of the candidates selected by the connectivity checks phase, media flow MUST be switched to use the best candidate pair exchanged. Endpoints that follow this protocol SHOULD be prepared to accept media on any of the published candidates' local transport addresses.