Editing IP Multimedia Subsystem (section)

==== Media servers ====
The ''Media Resource Function'' (MRF) provides media related functions such as [[media manipulation]] (e.g. voice stream mixing) and playing of tones and announcements.

Each MRF is further divided into a ''media resource function controller'' (MRFC) and a ''media resource function processor'' (MRFP).

* The MRFC  is a signalling plane node that interprets information coming from an AS and S-CSCF to control the MRFP
* The MRFP is a media plane node used to mix, source or process media streams. It can also manage access right to shared resources.

The ''Media Resource Broker'' (MRB) is a functional entity that is responsible for both collection of appropriate published MRF information and supplying of appropriate MRF information to consuming entities such as the AS. MRB can be used in two modes:
* Query mode: AS queries the MRB for media and sets up the call using the response of MRB
* In-Line Mode: AS sends a SIP INVITE to the MRB. The MRB sets up the call