5.21.3.1 General

A Network Function instance can be deployed such that several network function instances are present within an NF Set to provide distribution, redundancy and scalability together as a Set of NF instances. The same is also supported for NF Services. This can be achieved when the equivalent NFs and NF Services share the same context data or by Network Function/NF Service Context Transfer procedures as specified in clause 4.26 of TS 23.502 [3].

NOTE: A NF can be replaced by an alternative NF within the same NF Set in the case of scenarios such as failure, load balancing, load re-balancing.

Such a network reliability design shall work in both communication modes, i.e. Direct Communication and Indirect Communication. In the Direct Communication mode, the NF Service consumer is involved in the reliability related procedures. In Indirect Communication mode, the SCP is involved in the reliability related procedures.