Origin defines the structure for the “o=” field which provides the
originator of the session plus a session identifier and version number.
RepeatTime describes the “r=” fields of the session description which
represents the intervals and durations for repeated scheduled sessions.
SessionDescription is a a well-defined format for conveying sufficient
information to discover and participate in a multimedia session.
TimeDescription describes “t=”, “r=” fields of the session description
which are used to specify the start and stop times for a session as well as
repeat intervals and durations for the scheduled session.
TimeZone defines the structured object for “z=” line which describes
repeated sessions scheduling.
Timing defines the “t=” field’s structured representation for the start and
stop times.