ETSI TS 123 236 covers the details for the Intra Domain Connection of RAN Nodes to Multiple CN Nodes for GERAN and UTRAN based systems. In particular, it details the impacts to GSM and UMTS systems and the stage 2 procedures for the support of connecting a RNC or BSC to multiple MSC servers or SGSNs. The overall solution is described, and the detailed impacts on the existing specifications are identified. The description of a broadly similar concept for EUTRAN based systems is not described in the document: instead, it is described in TS 23.401 [22].

NOTE: The specified solution impacts RAN nodes. In case an upgrade of radio networks is not performed, the solutions for deploying NNSF functionality above RAN nodes described in TR 23.924 [23] may be used as a guideline for connecting RAN nodes to multiple MSC servers.

The reference model to which these procedures apply can be found within TS 23.002 [1]. Detailed architectural requirements within the subsystems are contained within the remainder of the 23 series of specifications e.g. the requirements for the Packet Switched (PS) domain are contained within TS 23.060 [2] and the requirements for the Bearer Independent CS Core Network are contained in TS 23.205 [14].