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Content for  TS 23.502  Word version:  19.1.0

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1…   4.2.2.2.2   4.2.2.2.3…   4.2.2.3…   4.2.3…   4.2.3.3   4.2.4…   4.2.6   4.2.7…   4.2.9…   4.2.11…   4.2.11.5…   4.3…   4.3.2.2.2   4.3.2.2.3…   4.3.3…   4.3.3.3   4.3.4…   4.3.4.3   4.3.5…   4.3.5.2…   4.3.5.4…   4.3.5.6…   4.3.6…   4.4…   4.5…   4.9…   4.9.1.3…   4.9.2…   4.11…   4.11.1…   4.11.1.2.2   4.11.1.2.3   4.11.1.3…   4.11.1.3.3…   4.11.1.4…   4.11.1.5…   4.11.2…   4.11.3…   4.12…   4.12.6…   4.12a…   4.12b…   4.13…   4.13.4…   4.13.6…   4.14…   4.15…   4.15.3.2.5…   4.15.4…   4.15.6…   4.15.6.7…   4.15.6.13…   4.15.6.14…   4.15.9…   4.15.9.4…   4.15.13…   4.15.13.4…   4.16…   4.16.4…   4.16.8…   4.16.11…   4.16.14…   4.16.15…   4.17…   4.17.9…   4.18…   4.19…   4.22…   4.23…   4.23.7…   4.23.7.3.3   4.23.7.3.4…   4.23.9…   4.23.9.4…   4.23.11…   4.24…   4.25…   4.25.6…   4.26…   5…   5.2.3…   5.2.5…   5.2.6…   5.2.7…   5.2.8…   5.2.9…   5.2.12…   5.2.18…   A…   E…   F…   G   H… 
4.12.6 UE or Network Requested PDU Session Modification via Untrusted non-3GPP access  4.12.7 UE or network Requested PDU Session Release via Untrusted non-3GPP access  4.12.8 Mobility from a non-geographically selected AMF to a geographically selected AMF 
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4.12.6  UE or Network Requested PDU Session Modification via Untrusted non-3GPP access  p. 351

The UE or network requested PDU Session Modification procedure via untrusted non-3GPP access is depicted in Figure 4.12.6-1. The procedure applies in non-roaming, roaming with LBO as well as in home-routed roaming scenarios.
For non-roaming and LBO scenarios, the functional entities in the following procedures are located in the PLMN of the N3IWF.
The procedure below is based on the PDU Session Modification procedure specified in clause 4.3.3.2 (for non-roaming and roaming with LBO) and on the PDU Session Modification procedure specified in clause 4.3.3.3 (for home-routed roaming).
Reproduction of 3GPP TS 23.502, Fig. 4.12.6-1: UE or Network Requested PDU Session Modification via untrusted non-3GPP access
Figure 4.12.6-1: UE or Network Requested PDU Session Modification via untrusted non-3GPP access
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Step 1.
If the PDU Session Modification procedure is initiated by the UE, the UE shall send a PDU Session Modification Request message to AMF as specified in step 1 of clause 4.3.2.2. The message shall be sent to N3IWF via the established IPsec SA for NAS signalling. The N3IWF shall transparently forward the PDU Session Modification Request to AMF/SMF.
Step 2.
In the case of non-roaming or LBO, the steps 1a (from AMF) to 1e and steps 2-3 as per the PDU Session Modification procedure in clause 4.3.3.2 are executed.
In the case of home-routed, the steps 1a (from AMF) to 1d and steps 2-3 as per the PDU Session Modification procedure in clause 4.3.3.3 are executed.
Step 3.
The AMF sends N2 PDU Session Resource Modify Request (N2 SM information received from SMF, NAS message) message to the N3IWF. This step is the same as step 4 in clause 4.3.3.2 (for non-roaming and roaming with Local Breakout) and step 5 in clause 4.3.3.3 (for home-routed roaming).
Step 4.
The N3IWF may issue IKEv2 signalling exchange with the UE that is related with the information received from SMF according to the IKEv2 specification in RFC 7296 [3]. Based on the N2 SM information received from the SMF, the N3IWF may perform one of the following:
Step 4a.
The N3IWF may decide to create a new Child SA for the new QoS Flow(s). In this case, the N3IWF establishes a new Child SA by sending an IKE_CREATE_CHILD_SA request message, which includes the SA, the PDU Session ID, the QFI(s), optionally a DSCP value and optionally the Additional QoS Information specified in clause 4.12a.5. If the Additional QoS Information is received, the UE may reserve non-3GPP Access Network resources according to the Additional QoS Information.
Step 4b.
The N3IWF may decide to add or remove QoS Flow(s) to/from an existing Child SA. In this case, the N3WIF updates the QoS Flow and Child SA mapping information by sending an INFORMATIONAL request message, which includes the QFI(s) associated with the Child SA and optionally the Additional QoS Information specified in clause 4.12a.6, which contains the new QoS information that should be associated with the existing Child SA. If the Additional QoS Information is received, the UE may update the reserved non-3GPP Access Network resources for the existing Child SA according to the Additional QoS Information.
Step 4c.
The N3IWF may decide to delete an existing Child SA, e.g. when there is no QoS Flow mapped to this Child SA. In this case, the N3IWF deletes the existing Child SA by sending INFORMATIONAL request message, which includes a Delete payload.
Step 5.
The N3IWF acknowledges N2 PDU Session Request by sending a N2 PDU Session Response Message to the AMF to acknowledge the success or failure of the request.
Step 6.
In the case of non-roaming or LBO, step 7 as per the PDU Session Modification procedure in clause 4.3.3.2 is executed. In the case of home-routed, the steps 8-10 as per the PDU Session Modification procedure in clause 4.3.3.3 are executed.
Step 7.
The N3IWF sends the PDU Session Modification Command to UE (if received in step 3) and receives the response message from UE.
Steps 4a/4c and step 7 may happen consecutively. Steps 7b map happen before step 4b/4d.
Step 8.
The N3IWF forwards the NAS message to the AMF.
Step 9.
For non-roaming and roaming with LBO, all the steps after step 10 in clause 4.3.3.2 are executed according to the general PDU Session Modification procedure. For home-routed roaming, all steps after step 13 in clause 4.3.3.3 are executed according to the general PDU Session Modification procedure.
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4.12.7  UE or network Requested PDU Session Release via Untrusted non-3GPP access  p. 353

Clause 4.12.7 specifies how a UE or network can release a PDU Session via an untrusted non-3GPP Access Network. The UE requested PDU Session Release procedure via Untrusted non-3GPP access applies in non-roaming, roaming with LBO as well as in home-routed roaming scenarios.
For non-roaming and LBO scenarios, if the UE is simultaneously registered to a 3GPP access in a PLMN different from the PLMN of the N3IWF, the functional entities in the following procedures are located in the PLMN of the N3IWF. For home-routed roaming scenarios, the AMF, V-SMF and associated UPF in VPLMN in the following procedure is located in the PLMN of the N3IWF.
Reproduction of 3GPP TS 23.502, Fig. 4.12.7-1: UE Requested PDU Session Release via Untrusted non-3GPP access
Figure 4.12.7-1: UE Requested PDU Session Release via Untrusted non-3GPP access
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Step 1.
One or more PDU Sessions are already established for the UE using the procedure described in clause 4.12.2.
Step 2.
The UE sends a NAS message (N1 SM container (PDU Session Release Request), PDU Session ID) to the AMF via the N3IWF as defined in clause 4.3.4.
Step 3.
For non-roaming and roaming with LBO, the steps 1a (from AMF) to 4 according to the PDU Session Release procedure defined in clause 4.3.4.2 are executed. For home-routed roaming, the steps 1a (from AMF) to step 7 according to the PDU Session Release procedure defined in clause 4.3.4.3 are executed.
Step 4.
This step is the same as step 4 in clause 4.3.4.2 (non-roaming and LBO) and step 6 in clause 4.3.4.3 (home-routed roaming).
If the message received from the SMF does not include N2 SM Resource Release request, the AMF sends N2 Downlink NAS transport (N1 SM container (PDU Session Release Command), PDU Session ID, Cause) message to the N3IWF and steps 5 to 8 are skipped.
Step 5.
Upon receiving AN session release request message from the AMF, the N3IWF triggers the release of the corresponding Child SA by sending INFORMATIONAL EXCHANGE (Delete Payload) to the UE. Delete payload is included in the message listing the SPIs of the Child SAs to be deleted to this PDU Session as described in RFC 7296 [3].
Step 6.
The UE responds with INFORMATIONAL EXCHANGE (Delete Payload) message. Delete payload is included for the paired SAs going in the other direction as described in RFC 7296 [3].
Step 7.
This step is the same as step 6 in 4.3.4.2 (non-roaming and LBO) and step 8 in clause 4.3.4.3 (home-routed roaming).
Step 8.
For non-roaming and roaming with LBO, steps 7 according to the PDU Session Release procedure defined in clause 4.3.4.2 are executed. For home-routed roaming, step 9-10 according to the PDU Session Release procedure defined in clause 4.3.4.3 are executed.
Step 9.
The N3IWF delivers the NAS message (N1 SM container (PDU Session Release Command), PDU Session ID, Cause) to the UE.
Step 10.
The UE sends a NAS message (N1 SM container (PDU Session Release Ack), PDU Session ID) to the N3IWF.
Step 11.
This step is the same as step 9 in 4.3.4.2 (non-roaming and LBO) and step 11 in clause 4.3.4.3 (home-routed roaming).
Steps 5 and 9 may happen consecutively. Step 10 may happen before step 6.
Step 12.
For non-roaming and roaming with LBO, all steps after step 10 in the PDU Session Release procedure defined in clause 4.3.4.2 are executed. In the case of home-routed roaming, all steps after step 12 in the PDU Session Release procedure defined in clause 4.3.4.3 are executed.
The network requested PDU Session Release procedure via Untrusted non-3GPP access is the same as the network requested PDU Session Release Procedure specified in clause 4.3.4.2 (for Non-Roaming and Roaming with Local Breakout) with the following differences:
  • The (R)AN corresponds to an N3IWF.
  • In step 5 the N3IWF upon receiving N2 SM request to release the AN resources associated with the PDU Session from the AMF, the N3IWF triggers the release of the corresponding Child SA to the UE as specified in step 5 and 6, in Figure 4.12.7-1.
  • User Location Information is not included in the step 6, 7a, 9, 10a and 12 of the procedure.
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4.12.8  Mobility from a non-geographically selected AMF to a geographically selected AMF  p. 355

This procedure describes the AMF change that takes place when an UE initially served via non-3GPP access by an AMF selected based on non-geographical criteria (e.g. because the UE had no 3GPP access coverage or because only non-geographically selectable N3IWF are deployed) gets 3GPP access and is now to be served by an AMF selected in the same PLMN by the NG-RAN based on geographical criteria.
Reproduction of 3GPP TS 23.502, Fig. 4.12.8-1: Mobility from a non-geographically selected AMF to a geographically selected AMF
Figure 4.12.8-1: Mobility from a non-geographically selected AMF to a geographically selected AMF
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Step 1.
The UE registers over non-3GPP access, as described in clause 4.12.2. During this procedure:
  1. An AMF (source AMF) is selected by the N3IWF in step 6a, based on non-geographical criteria (e.g. because the UE has no 3GPP access coverage or because only non-geographically selectable N3IWF are deployed).
  2. The UE receives, within the Registration Accept message, a 5G-GUTI containing a GUAMI of the non-geographically selected AMF. The UE also receives an Allowed NSSAI and optionally Mapping Of Allowed NSSAI.
Step 2.
The UE may activate PDU Sessions over non-3GPP access, as described in clause 4.12.5.
Step 3.
The UE gets 3GPP access and issues a Registration Request over 3GPP access as defined in step 1 of Figure 4.2.2.2.2-1, providing its 5G-GUTI.
If the 5G-GUTI does not indicate an AMF of the same Region ID as that of the NG-RAN, the NG-RAN selects an AMF Set and an AMF in the AMF Set as described in clause 6.3.5 of TS 23.501.
Steps 3 to 22 of Figure 4.2.2.2.2-1 take place including following aspects:
  • step 4 of Figure 4.2.2.2.2-1 takes place i.e. the new AMF invokes the Namf_Communication_UEContextTransfer service operation on the old AMF to request the UE's SUPI and MM Context.
  • in step 5 of Figure 4.2.2.2.2-1, the old AMF includes information about active NGAP association to N3IWF.
  • in step 18 of Figure 4.2.2.2.2-1, the new AMF modifies the NGAP association toward N3IWF.
  • in step 21 of Figure 4.2.2.2.2-1, the Registration Accept message shall include the updated 5G-GUTI that the UE will use to update its 3GPP and non-3GPP registration contexts.
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