href="http://scm.sipfoundry.org/rep/ietf-drafts/simple/draft-ietf-simple-msrp-relays-03.html"
target="NewWindow">draft-ietf-simple-msrp-relays-03

The SIMPLE Working Group uses two
separate models for conveying instant messages. Pager-mode messages stand alone
and are not part of a SIP (Session Initiation Protocol) session, whereas
Session-mode messages are setup as part of a session using the SIP protocol.
MSRP (Message Sessions Relay Protocol) is a protocol for near-real-time,
peer-to-peer exchange 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.