Relay Extensions for the Message Sessions Relay Protocol (MSRP)
Two separate models for conveying instant messages have been defined. Page-mode messages stand alone and are not part of a SIP (Session Initiation Protocol) session, whereas Session-mode messages are set up as part of a session using the SIP protocol. MSRP (Message Session Relay Protocol) is a protocol for near real-time, peer-to- peer exchanges of binary content without intermediaries, which is designed to be signaled using a separate rendezvous protocol such as SIP. This document introduces the notion of message relay intermediaries to MSRP and describes the extensions necessary to use them.