M. Makaraju Alcatel-Lucent Unaffiliated Unaffiliated This document specifies how the Message Session Relay Protocol (MSRP) can be instantiated as a data channel sub-protocol, using the the SDP offer/answer exchange-based external negotiation defined in [I-D.ejzak-mmusic-data-channel-sdpneg]. Two network configurations are documented: a WebRTC end-to-end configuration (connecting two MSRP over data channel endpoints), and a gateway configuration (connecting an MSRP over data channel endpoint with an MSRP over TCP endpoint).