This document defines extends SIP with two header fields and associated
option tags that can be used in INVITE requests to convey the requester's
preference for user-interface handling related to answering of that
The first header, "Answer-Mode", expresses a preference as to whether the
target node's user interface waits for user input before accepting the
request or instead accepts the request without waiting on user input. The
second header, "Priv-Answer-Mode" is similar to the first, except that it
requests administrative-level access and has consequent additional
authentication and authorization requirements. These behaviors have
applicability to applications such as Push-to-Talk and to diagnostics
like loop-back. Usage of each header field in a response to indicate
how the request was handled is also defined.
Working Group Summary
There is consensus in the working group to publish this document. The
proposal was originally submitted as a P-header, but it was decided that
this aspect should be brought out and made generally applicable to all
SIP implementations. Early concerns about the possibility to use the
header as a means of eavesdropping have been addressed in the
There has been no indication of implementation. The document has been
required in support of the OMA PoC feature, and it can be assumed that
there have been implementations of the OMA work that have therefore
used this feature.
The document shepherd for this document was Keith Drage. The responsible
Area Director was Cullen Jennings.