Over the Nb reference point the bearer control and transport are performed. The transport may be RTP/UDP/IP or AAL2 for transport of user data. Different options for user data transport and
bearer control shall be possible on Nb, for example: AAL2/Q.AAL2, STM/none, RTP/H.245, IPBC.
Over the Nc reference point, the Network-Network based call control is performed. Examples of this are ISUP or an
evolvement of ISUP for bearer independent call control (BICC). Different options for signalling transport on Nc shall be possible including IP.
The Np reference point enables transport of RAN User Plane Congestion Information (RUCI) sent from the RCAF to
the PCRF for all or selected subscribers, depending on the operator's congestion mitigation policy.
The Np reference point supports the following functions:
Reporting of RUCI from the RCAF to the PCRF.
Sending, updating and removal of the reporting restrictions from the PCRF to the RCAF.