Methods for enhancing sdp preconditions signalling for ip multimedia sessions

摘要

This application describes how Session Description Protocol (SDP) preconditions signaling can be enhanced to support lead role negotiation, precondition capability exchange, premature precondition attempts, and concatenated preconditions processing. The application describes the use of send and receive tags (1004) in an SDP message (1012) for a given media line. In a given message, a success or failure tag (1018) may be associated with a send or receive tag in addition to an optional or mandatory condition indicator tag. A lead role indicator may also be associated with a send or receive tag to indicate a desired preference with regard to the sender or receiver taking the lead role.; These additions lead to a greater chance of successful session set-up completion, reduce the number of signaling exchanges in general, and enable precondition attempts to be started earlier and to be executed in parallel.