The MRFC responds
to the S-CSCF with 100 Trying. The MRFC acts as a terminating user agent
in these scenarios. Conference identifiers are sent in a 200 OK response.
When granting control of the floor during a conference session, the MRFC sends a
???re-INVITE??? to the user being passed or granted control. Flooring is the function used
in conferences that allows another participant to control the application. This is commonly
used when showing presentations or sharing documents, for example. All of the
other participants then have the ability to see what is being shared, but they cannot
control the session until the host grants them the floor.
IMS Reference Points
The protocol used throughout the IMS is SIP; however, there are instances when
DIAMETER is used. Any instance when session control is needed, SIP is used. When
accessing subscriber data or charging data, DIAMETER is used. This would mean that
some devices must be able to communicate using both SIP and DIAMETER.
Figure 1.9 depicts the IMS reference points for both wireline and wireless. These are
defined by the 3GPP and represent the major interfaces. Additional views of these and
other reference points are provided here for clarity and to provide other views of how
IMS may be implemented (in an all-wireless network, for example).
Figure 1.10 depicts an all-wireless implementation.
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