Section: 5.21.2.1 AMF Addition/Update
Content: The 5G System should support establishment of association between AMF and 5G-AN node. A new AMF can be added to an AMF set and association between AMF and GUAMI can be created and/or updated as follows: - AMF shall be able to dynamically update the NRF with the new or updated GUAMI(s) to provide mapping between GUAMI(s) and AMF information. Association between GUAMI(s) and AMF is published to NRF. In addition, to deal with planned maintenance and failure, an AMF may optionally provide backup AMF information, i.e. it act as a backup AMF if the indicated GUAMI associated AMF is unavailable. It is assumed that the backup AMF and the original AMF are in the same AMF set as they have access to the same UE context. Based on that information one GUAMI is associated with an AMF, optionally with a backup AMF used for planned removal and/or another (same or different) backup AMF used for failure. - Upon successful update, the NRF considers the new and/or updated GUAMI(s) for providing AMF discovery results to the requester. Requester can be other CP network functions. - The new AMF provides its GUAMI to 5G-AN and 5G-AN store this association. If the association between the same GUAMI and another AMF exists in the 5G-AN (e.g. due to AMF planned removal), the previously stored AMF is replaced by the new AMF for the corresponding GUAMI association. Information about new AMF should be published and available in the DNS system. It should allow 5G-AN to discover AMF and setup associations with the AMF required. N2 setup procedure should allow the possibility of AMFs within the AMF Set to advertise the same AMF Pointer and/or distinct AMF Pointer value(s) to the 5G-AN node. To support the legacy EPC core network entity (i.e. MME) to discover and communicate with the AMF, the information about the AMF should be published and available in the DNS system. Furthermore, GUMMEI and GUAMI encoding space should be partitioned to avoid overlapping values in order to enable MME discover an AMF without ambiguity.