Page 81 - ITU-T Focus Group IMT-2020 Deliverables

ITU-T Focus Group IMT-2020 Deliverables 3

b) If the UE does not have a PDU session established with this specific SM-NSSAI, the UE requests
a new PDU session with this SM-NSSAI and with the DNN that may be provided by the
application.
14) The CCNF selects an SMF in a network slice instance based on SM-NSSAI, DNN and other information
e.g. UE subscription and local operator policies. The selected SMF establishes a PDU session based
on SM-NSSAI and DNN.
15) For roaming scenarios, the slice specific network functions beyond CCNF in VPLMN and HPLMN are
selected based on the SM-NSSAI provided by the UE as following.
a) If standard SM-NSSAI is used, then selections of slice specific NF instances are done by each
PLMN based on the standard SM-NSSAI.
b) If non-standard SM-NSSAI is used, the VPLMN maps the SM-NSSAI of HPLMN to a SM-NSSAI of
VPLMN based on roaming agreement (including mapping to a default SM-NSSAI of VPLMN). The
selection of slice specific NF instance in VPLMN are done based on the SM-NSSAI of VPLMN,
and the selection of any slice specific NF instance in HPLMN are based on the SM-NSSAI of
HPLMN.
NOTE – whether the SM-NSSAI can be directly used as input to network function instance selection procedure
defined in KI 7# should be decided in normative phase.
Regarding support of network slicing, SA2 scope in TS phase 1 is only limited to NextGen Core Network.
Whether RAN is sliced is up to RAN WGs to determine.

Figure 6.1.1-1 – SA2 scope for support of network slicing in TS phase 1

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