| Summary: |
This document describes a set of extensions to SIP which allow for
various call control services. Example services include blind
transfer, transfer with consultation, multi-party calls, bridged
conferences, and ad-hoc conferencing. The services are supported in a
fully distributed manner, so that they can be provided without a
central conference server. However, a SIP proxy can act as a
conference server to provide these services. For the various services
described here, we overview the requirements for the service, and
specify the protocol functions needed to support it. We then define a
basic set of SIP primitives which can be used to construct these
services, and others.
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