The CLUE protocol is an application protocol conceived for the description and negotiation of a CLUE telepresence session. The design of the CLUE protocol takes into account the requirements and the framework defined, respectively, in [I-D.ietf-clue-framework] and [RFC7262]. The companion document [I-D.ietf-clue-signaling] delves into CLUE signaling details, as well as on the SIP/SDP session establishment phase. CLUE messages flow upon the CLUE data channel, based on reliable and ordered SCTP over DTLS transport, as described in [I-D.ietf-clue-datachannel]. Message details, together with the behavior of CLUE Participants acting as Media Providers and/or Media Consumers, are herein discussed.