Content for  TS 23.548  Word version:  18.4.0

During the Registration procedure, the AMF receives the HR-SBO allowed indication per DNN/S-NSNAI from the UDM in the step 14b of the procedure in the clause 4.2.2.2.2 of TS 23.502.

During the PDU Session Establishment procedure for Home-routed roaming as in clause 4.3.2.2.2 of TS 23.502, if the UE is roaming and if the AMF had received in SMF Selection Subscription data from UDM the HR-SBO allowed indication for the DNN/S-NSSAI in the step 1, the AMF selects a V-SMF supporting HR-SBO and sends an HR-SBO allowed indication to the V-SMF in the step 2 and the step3a of the procedure in Figure 4.3.2.2.2-1 in clause 4.3.2.2.2 of TS 23.502. If the V-SMF supporting the HR-SBO receives the HR-SBO allowed indication from AMF, the V-SMF may:

• select UL CL/BP UPF and L-PSA UPF based on UE location information and this indication in the step 4 of the Figure 4.3.2.2.2-1 of TS 23.502.
• select a V-EASDF;
• obtain the V-EASDF IP address based on local configuration, or invoke Neasdf_DNSContext_Create Request including the DNN, S-NSSAI, HPLMN ID and the UE IP address set to unspecified address or to a mapped address as specified in clause 7.1.2.2 to obtain the V-EASDF IP address; and
• send the request for the establishment of the PDU Session supporting HR-SBO in VPLMN and optionally send the V-EASDF IP address to the H-SMF in the Nsmf_PDUSession_Create Request in the step 6 of the procedure in Figure 4.3.2.2.2-1 in clause 4.3.2.2.2 of TS 23.502.

The H-SMF authorizes the request for HR-SBO based on SM subscription data (i.e. HR-SBO authorization indication) in the step 7 of the procedure in the clause 4.3.2.2.2 of TS 23.502. Once the HR-SBO is authorized, the H-SMF requests and retrieves the optional VPLMN Specific Offloading Policy from H-PCF. The H-SMF generates VPLMN Specific Offloading Information (i.e. IP range(s) and/or FQDN(s) allowed to be routed to the local part of DN in VPLMN, and/or Authorized DL Session AMBR for Offloading) based on the VPLMN Specific Offloading Policy. If HR-SBO is authorized for the PDU session, the H-SMF provides in the Nsmf_PDUSession_Create Response in the step 13 of the procedure in Figure 4.3.2.2.2-1 in clause 4.3.2.2.2 of TS 23.502 with the following information:

• optionally, VPLMN Specific Offloading Information that may include FQDN range, IP range, session AMBR for the local part of DN and charging policy.
  The VPLMN specific Offloading Policy may refer to either allowed or not allowed traffic for HR-SBO (the latter is being used when the HPLMN would like to ensure that certain traffic are not allowed for HR-SBO). The VPLMN Specific Offloading Policy for the allowed and not allowed traffic should be mutually exclusive, i.e., either a list of allowed or a list of not allowed traffic descriptors should be sent, but not both. The VPLMN Specific Offloading Policy can be configured in the H-SMF and tagged with Offload Identifier(s), and which VPLMN Specific Offloading Information to be sent to V-SMF can be indicated by these Offload Identifier(s) received from UDM/H-PCF.
  Similarly, H-SMF may also sends the Offload Identifier(s) as labels of the VPLMN Specific Offloading Information together with the VPLMN Specific Offloading Information to be sent to V-SMF:
• If the given V-SMF has already received the VPLMN Specific Offloading Information corresponding to certain Offload Identifier(s), this could be indicated to the H-SMF in any subsequent request to another HR-PDU Session from the same V-SMF, and the H-SMF will in this case send only the Offload Identifier(s) as a response;
• If the VPLMN Specific Offloading Information for a given Offload Identifier is changed, for each V-SMF using the Offload Identifier, the H-SMF chooses one existing HR-SBO PDU Session using the Offload Identifier to update VPLMN Specific Offloading Information and corresponding Offload Identifier to the V-SMF via PDU Session Modification procedure as described in clause 4.3.3.3 of TS 23.502;
• During PDU Session Release procedure as described in clause 4.3.4.3 of TS 23.502, if the PDU Session is the last HR-SBO PDU Session using a given Offload Identifier on the V-SMF, the V-SMF may remove the Offload Identifier and corresponding VPLMN Specific Offloading Information based on roaming agreements.
• the V-EASDF IP address (corresponding to clause 6.7.2.3) or DNS server IP address of HPLMN (corresponding to clause 6.7.2.5) as DNS server address to be sent to the UE via PCO; and
• optionally, the DNS server address provided by HPLMN to be used for DNS requests related with traffic not to be subject to HR-SBO, including to configure V-EASDF corresponding to clause 6.7.2.3, or configure the UPF in VPLMN to perform IP replacement as described in clause 6.7.2.5;
• optionally, the HPLMN address information (e.g. H-UPF IP address on N6) to be used by V-EASDF to build EDNS Client Subnet option for target FQDN of the DNS query which is not authorized for HR-SBO as described in clause 6.7.2.3;
• the HR-SBO authorization result (i.e. whether HR-SBO request is authorized or not).

The H-SMF may indicate to the UE either that for the PDU Session the use of the EDC functionality is allowed or that for the PDU Session the use of the EDC functionality is required. If the request for HR-SBO is not authorized and DNS context has been created, the V-SMF delete the DNS context from the selected V-EASDF, and the subsequent steps related to the EASDF in this procedure are skipped. The detailed information of VPLMN Specific Offloading Policy is described in clause 6.4 of TS 23.503.

The V-SMF configures the V-EASDF with the DNS handling rules using the VPLMN Specific Offloading Information received from H-SMF or corresponding to Offload Identifier(s) received from H-SMF. The V-SMF optionally configures the V-EASDF with the DNS server address provided by the HPLMN as default DNS server (corresponding to clause 6.7.2.3), after the step 13 of the procedure in Figure 4.3.2.2.2-1 in clause 4.3.2.2.2 of TS 23.502 if they are received from H-SMF in the step 2. If V-SMF has not received the DNS server address provided by HPLMN from H-SMF in step 2, a default DNS server may be configured to V-EASDF. If HPLMN address information is received, the V-SMF may also configure the V-EASDF to build EDNS Client Subnet option based on this HPLMN address information for target FQDN of DNS query which is not authorized for HR-SBO. If the V-SMF has interacted with the V-EASDF in step 2, then the V-SMF invokes Neasdf_DNSContext_Update Request including UE IP address to complete the configuration of the context in the V-EASDF. The V-SMF configures the UL CL UPF and PSA UPF selected in the step 2 to forward DNS messages to V-EASDF. At N4 session establishment for a PDU Session working in HR SBO mode, the SMF in VPLMN provides to any UPF in VPLMN acting as (local) PSA for that PDU Session and capable of enforcing NAT on N6 traffic: the HPLMN ID of UE, andthe DNN/S-NSSAI of the PDU Session in HPLMN for the PDU Session.

EAS Discovery procedure with V-EASDF is performed as described in clause 6.7.2.3.

EAS Discovery procedure with Local DNS Server/Resolver is performed as described in clause 6.7.2.4.

EAS discovery procedure with V-EASDF using IP replacement mechanism as described in clause 6.7.2.5.

The DNS query sent by the UE reaches the V-EASDF via the UL CL UPF and PSA UPF in VPLMN selected in step 2 of Figure 6.7.2.2-1. If the target FQDN of the DNS query is not part of the FQDN authorized by the H-SMF in step 2 of Figure 6.7.2.2-1, the following a) or b) may be performed:

1. The V-EASDF proceeds to step 12 of Figure 6.2.3.2.2-1 where it sends the DNS query which may include the HPLMN address information as the EDNS Client Subnet option. The DNS query is sent to the DNS server address according to the DNS message handling rules provided by the V-SMF or to the default DNS server configured in the V-EASDF. Upon receiving the DNS response, the procedure proceeds immediately to step 5.
2. The UL CL/BP UPF sends the DNS query to the DNS server address provided by HPLMN via V-UPF (if exists) and H-UPF (through N9), by modifying the packet's destination IP address (corresponding to V-EASDF) to the DNS server address provided by HPLMN on UL CL or H-UPF. For the corresponding DNS response received by H-UPF, the H-UPF or UL CL modifies the packets' destination IP address to that of the V-EASDF.
   This assumes that the UL CL is able to detect FQDN(s) in traffic sent to the IP address of the EASDF. It is thus incompatible with usage of DoT (DNS over TLS) or DoH to protect the DNS traffic exchanged between the UE and the PLMN.

The rest of the procedure assumes the target FQDN of the DNS query is part of the FQDN authorized by the H-SMF in step 2 of Figure 6.7.2.2-1.

The steps 8 to 15 of the procedure in the Figure 6.2.3.2.2-1 by replacing SMF and EASDF with V-SMF and V-EASDF respectively. If VPLMN Specific Offloading Information does not include FQDN range and the EAS IP address of the DNS response is not part of the IP range(s) authorized in step 2 of Figure 6.7.2.2-1, the following may be performed:

• If the V-EASDF is not configured with the DNS server address provided by the HPLMN as default DNS server, The V-SMF indicates the V-EASDF to construct and to send another DNS query with the same FQDN and the HPLMN address information as the EDNS Client Subnet option, to the DNS server address as described in step 1) bullet a). Otherwise V-SMF indicates the V-EASDF to construct and send another DNS query with the same FQDN to the DNS server provided by HPLMN.

The V-SMF selects UL CL/BP and local PSA in VPLMN based on the V-EASDF notification, EAS Deployment Information in the VPLMN, VPLMN Specific Offloading Information and UE location. The V-SMF may perform insertion or change of UL CL/BP and local PSA in VPLMN. The V-SMF configures the UL CL/BP and local PSA for the traffic to be offloaded to the local part of DN based on the VPLMN Specific Offloading Information received from H-SMF. In the case of UL CL, the V-SMF configures the traffic detection rules and traffic routing rules on the UL CL UPF based on the EAS Deployment Information and the EAS addresses included in VPLMN Specific Offloading Information. If there is no other V-UPF between the selected UL CL/BP in this step and H-UPF, the V-SMF sets up user plane between this UL CL/BP and H-UPF via the interaction with H-SMF. Otherwise, the V-SMF sets up user plane between this ULCL/BP and the existing V-UPF. The V-SMF sets up user plane between the selected UL CL/BP in this step and RAN (if no other V-UPF exists between RAN and this UL CL/BP) or the V-UPF (if exists between this UL CL/BP and RAN).

The steps 17 to 18 of the procedure in clause 6.2.3.2.2 by replacing SMF and EASDF with V-SMF and V-EASDF respectively.

V-EASDF sends the DNS Response to the UE.

The HR-SBO PDU Session is established. See the procedure in clause 6.7.2.2.

UL CL/BP insertion. See the step 1 of the procedure in Figure 6.2.3.2.3-1.

After UL CL/BP insertion is performed, the V-SMF sends new local DNS server address to the UE by performing PDU Session Modification procedure as in clause 4.3.3.3 of TS 23.502 with following additions:

• V-SMF sends Local DNS Server/Resolver to the H-SMF in the step 1a of the procedure as in clause 4.3.3.3 of TS 23.502.
• H-SMF sends the Local DNS Server/Resolver to be sent to the UE via PCO to the V-SMF in the step 3 of the procedure in clause 4.3.3.3 of TS 23.502.

See the steps 4-6 of the procedure in Figure 6.2.3.2.3-1.

The Registration procedure is described in step 1 of clause 6.7.2.2.

The HR-SBO PDU Session Establishment is described in the step 2 of clause 6.7.2.2 with the following differences:

• After step 3 in clause 4.3.2.2.2 of TS 23.502, the V-SMF selects a UPF in VPLMN supporting UL CL/BP and PSA functionalities based on UE location information.
• The V-SMF sends the request for establishment of the PDU session supporting HR-SBO in VPLMN without the V-EASDF IP address in the step 6 of clause 4.3.2.2.2 of TS 23.502.
• If the Nsmf_PDUSession_Create Request received by the H-SMF does not include the V-EASDF IP address, the H-SMF constructs PCO with DNS server address field set to DNS server address provided by the HPLMN and sends the PCO to UE via V-SMF in the step 13 of clause 4.3.2.2.2 of TS 23.502.

The V-SMF configures the V-EASDF and the UPF in VPLMN as described in step 3 of clause 6.7.2.2 with the following differences:

• Based on the FQDN(s) received from the VPLMN Specific Offloading Information, the V-SMF indicates the UPF in VPLMN to route DNS queries for the FQDN (range) query to V-EASDF. In the case of UL CL, the V-SMF configures the UPF in VPLMN with IP replacement information (i.e. DNS server IP address and port number of HPLMN, V-EASDF IP address and port number). In uplink direction, UPF in VPLMN replaces the destination address of the DNS query targeting an FQDN eligible for HR-SBO related offload from DNS server IP address of HPLMN to V-EASDF IP address; In downlink direction, UPF in VPLMN replaces the source address of the DNS response targeting an FQDN eligible for HR-SBO related offload from V-EASDF IP address to DNS server IP address of HPLMN.

UE sends DNS query to DNS server of HPLMN.

If the DNS query does not match the FQDN range eligible for HR-SBO related offload, UPF in VPLMN delivers the DNS query via H-PSA through N9 and H-PSA delivers the DNS query to the DNS server of HPLMN.

If the DNS query matches the FQDN range eligible for HR-SBO related offload, the UPF in VPLMN delivers the DNS query to V-EASDF using IP replacement mechanism. The following EAS discovery procedure is based on step 4b.

The EAS discovery procedure described in steps 8-18 of clause 6.2.3.2.2 applies with the following differences:

• This EAS discovery procedure is implemented in the VPLMN.
• In step 16, the V-SMF may perform insertion or change of UL CL/BP and local PSA in VPLMN as described in the step 3 of clause 6.7.2.3.

The V-EASDF sends the DNS response including FQDN to the UPF in VPLMN. The UPF in VPLMN replaces the source address from V-EASDF to DNS server of HPLMN in the DNS response based on the V-SMF instructions and sends this DNS response to the UE directly or via UL CL/BP of VPLMN if existing in this PDU Session.

The AF may subscribe to H-SMF for the event related with a mobility of the PDU Session towards a serving PLMN where local traffic offload is possible, i.e. mobility of the PDU Session either towards HPLMN or towards a VPLMN where HR-SBO is possible i.e. supported and allowed.

Step 1 in Figure 4.23.7.3.2-1 of TS 23.502 (initiation of the N2-based handover). For an intra PLMN HO, the source AMF provides the target AMF with whether HR-SBO is allowed for each PDU Session of the UE. For an inter PLMN HO, the target T-AMF uses local policies related to the SLA with the HPLMN of the UE to determine whether HR-SBO allowed indication is sent to the V-SMF(s) for the PDU Sessions of the UE.

Step 2 in Figure 4.23.7.3.2-1 of TS 23.502 takes place. If the T-AMF considers that HR-SBO is possible, the T-AMF selects a V-SMF supporting HR-SBO.

(V-SMF insertion or V-SMF change) step 2 in Figure 4.23.7.3.2-1 of TS 23.502 takes place. For V-SMF insertion and inter VPLMN V-SMF change case, the T-AMF sends an HR-SBO allowed indication to the target V-SMF in Nsmf_PDUSession_CreateSMContext Request as part of the step 3 of the procedure in Figure 4.23.7.3.2-1 of TS 23.502.

(V-SMF removal) steps 9 to 12b in Figure 4.23.7.3.2-1 of TS 23.502 take place. The target AMF sends to H-SMF a Nsmf_PDUSession_CreateSMContext request as in step 9 in Figure 4.23.7.3.2-1 of TS 23.502. For EAS discovery with EASDF, the H-SMF selects an EASDF in HPLMN and configures the DNS context in this EASDF (Neasdf_DNSContext_Create) and may select and configure UPF(s) in HPLMN. For EAS discovery with Local DNS Server, the H-SMF selects a Local DNS Server.

(V-SMF insertion or V-SMF change) step 4 or step 5 in Figure 4.23.7.3.2-1 of TS 23.502.

(V-SMF insertion case) The (target) V-SMF retrieves SM context from H-SMF using Nsmf_PDUSession_Context Request, followed by the Nsmf_PDUSession_Context Response.

(V-SMF change case) The target V-SMF retrieves SM context from the source V-SMF using Nsmf_PDUSession_Context Request/Response. In step 3b, if source and target V-SMFs belong to same VPLMN, the SM context includes Authorization Result for HR-SBO, VPLMN Specific Offloading Information, the SM context also includes (if previously received by source V-SMF from H-SMF in the case of V-SMF change) the HPLMN address information, and the DNS Server address provided by the HPLMN. The SM context may also include EAS information to be refreshed for EAS re-discovery, i.e. FQDN(s) corresponding to the old target DNAI selected by the source V-SMF (V-SMF change case).

(V-SMF insertion or V-SMF change) The (target) V-SMF selects a new V-EASDF e.g. based on the target UE location. The (target) V-SMF invokes Neasdf_DNSContext_Create including the DNN, S-NSSAI and HPLMN ID to obtain the new V-EASDF address. In the case of V-SMF insertion, the UE IP address is set to the unspecified address in Neasdf_DNSContext_Create as specified in clause 7.1.2.2. In the case of V-SMF change with inter PLMN mobility or intra PLMN mobility, the target V-SMF shall select a new V-EASDF if it is configured to use an EASDF for the PDU Session. To support EAS discovery with local DNS server as described in clause 6.7.2.4, the (target) V-SMF (re-)selects a local DNS server, e.g. based on the target UE location.

(V-SMF insertion or V-SMF change) The (target) V-SMF may perform UL CL/BP and local PSA insertion/change/removal as described in step 2 of Figure 6.7.2.2-1.

The H-SMF (V-SMF removal) or the target V-SMF (V-SMF insertion or V-SMF change) responses to the target AMF with a Nsmf_PDUSession_CreateSMContext Response as in step 8 (V-SMF insertion or V-SMF change) or step 13 in Figure 4.23.7.3.2-1 of TS 23.502 (V-SMF removal).

(V-SMF insertion or V-SMF change) when the T-AMF sends to the Target V-SMF an indication of Handover Complete within Nsmf_PDUSession_UpdateSMContext Request (at step 2 in Figure 4.23.7.3.3-1 of TS 23.502) the target V-SMF invokes Nsmf_PDUSession_Update Request to the H-SMF. If a V-EASDF or a local DNS server has been selected in step 4, the selected V-EASDF or local DNS server address is provided in the request. The target V-SMF needs not provide the selected V-EASDF or local DNS server address if the target V-SMF is configured to use EAS discovery with V-EASDF using IP replacement mechanism corresponding to clause 6.7.2.5. If the UE indicated support of refreshing stale EAS information, the V-SMF may also provide an EAS rediscovery indication and EAS information to be refreshed for EAS re-discovery if received in step 3 to the H-SMF. This Nsmf_PDUSession_UpdateSMContext Request triggers steps 8 to 11.

(V-SMF insertion or V-SMF change): If the UE has changed of serving VPLMN or has moved from HPLMN to a VPLMN, the H-SMF:

• invokes Nudm_SDM_Get service to get subscription data from UDM by providing serving PLMN ID to get subscription data specific to the Serving PLMN;
• authorizes the request for HR-SBO based on the SM subscription data (i.e., HR-SBO authorization indication); and
• If the HR-SBO is authorized, retrieves the VPLMN Specific Offloading Policy from H-PCF.

(V-SMF insertion or V-SMF change): As defined in step 8 in clause 4.23.7.3.3 of TS 23.502, the H-SMF invokes Nsmf_PDUSession_Update Response, providing the same HR-SBO related information as sent by the H-SMF in step 2 of Figure 6.7.2.2-1. The H-SMF furthermore provides V-SMF with PCO including EAS rediscovery indication and impact field based on the EAS information to be refreshed for EAS re-discovery if received at step 7. The target V-SMF stores the PCO including the V-EASDF address/local DNS server address, EAS rediscovery, impact field for the UE until it receives an indication of HO completion as described in step 2 in Figure 4.23.7.3.3-1 of TS 23.502 or in step 11. If the request for HR-SBO is not authorized and a V-EASDF context had been created, the V-SMF deletes the DNS context from the selected V-EASDF, and the subsequent steps related to the HR-SBO in this procedure are skipped.

(V-SMF insertion or V-SMF change): The (target) V-SMF configures the V-EASDF with the DNS handling rules as defined in step 3 of Figure 6.7.2.2-1. If the (target) V-SMF has interacted with the V-EASDF in step 4, the V-SMF invokes Neasdf_DNSContext_Update Request including UE IP address to complete the configuration of the context in the V-EASDF. The (target) V-SMF may configure the ULCL/L-PSA selected in the step 5 to forward DNS messages to V-EASDF. When the V-SMF is configured to use EAS discovery with V-EASDF using IP replacement mechanism as described in clause 6.7.2.5, the (target) V-SMF configures the UL CL/L-PSA in the VPLMN with the IP replacement information (i.e. IP address of the DNS server provided by the HPLMN, the selected V-EASDF IP address and port number and DNS traffic filtering rules related with when IP replacement applies).

(V-SMF insertion or V-SMF change): The target V-SMF sends the PCO for the UE (received at step 9) in a PDU Session Modification Command sent to the UE. (V-SMF removal): At step 10 in Figure 4.23.7.3.3-1 of TS 23.502, when receiving Nsmf_PDUSession_UpdateSMContext Request (Handover Complete indication), the H-SMF sends the PCO including the V-EASDF or Local DNS Server address selected in step 2b in a PDU Session Modification Command sent to the UE. If the UE indicated support of refreshing stale EAS information, the PCO may include EAS rediscovery indication.

(V-SMF change or removal): When the S-AMF invokes Nsmf_PDUSession_ReleaseSMContext Request to inform the Source V-SMF to release the SM context of the PDU Session, e.g. at step 3a or 11a in Figure 4.23.7.3.3-1 of TS 23.502, the DNS context in the old (V-)EASDF is removed by the (source) V-SMF using Neasdf_DNSContext_Delete service. (V-SMF insertion): When the target V-SMF sends Nsmf_PDUSession_Update Request with a Handover Complete Indication at step 6 in Figure 4.23.7.3.3-1 of TS 23.502, the DNS context in the old EASDF is removed by the H-SMF using Neasdf_DNSContext_Delete service.

If the AF had subscribed in step 0 and a serving PLMN change occurred towards a PLMN where local traffic offload is possible for the PDU Session, the H-SMF notifies the AF indicating the target serving PLMN ID and DNN, S-NSSAI of the HPLMN. This may take place as soon as the H-SMF has received an indication of Handover Complete.

EAS discovery procedure by UE may take place: (V-SMF change or V-SMF insertion): EAS Discovery procedure with V-EASDF for HR-SBO (according to clause 6.7.2.3), with Local DNS for HR-SBO (according to clause 6.7.2.4), or with V-EASDF using IP replacement mechanism (according to clause 6.7.2.5); or (V-SMF removal): EAS Discovery procedure with EASDF or Local DNS Server (according to clause 6.2.3.2).

The UE establishes a HR-SBO PDU Session as described in clause 6.7.2.2.

The UE initiates Mobility Registration Update procedure to the Target AMF as described in clauses 4.23.3 and 4.2.2.2.2 of TS 23.502. During the registration procedure, the target AMF (in roaming case) receives the SMF selection data including HR-SBO allowed indication per DNN/S-NSSAI from the UDM in the step 14b of the procedure in clause 4.2.2.2.2 of TS 23.502.

(V-SMF insertion or V-SMF change): at step 17 of clause 4.2.2.2.2 of TS 23.502, the Target AMF selects and inserts a V-SMF supporting HR-SBO and provides the received HR-SBO allowed indication for the established Session for DNN, S-NSSAI in the PDUSession_CreateSMContext Request sent to the target V-SMF.

(V-SMF removal) in case the Target AMF is an AMF of HPLMN (the UE moves from a VPLMN to HPLMN), in step 3b-1, the Target AMF sends a PDUSession_CreateSMContext Request sent to the H-SMF. The H-SMF may select an EASDF in HPLMN and configure the DNS context in this EASDF (Neasdf_DNSContext_Create) and may select and configure UPF(s) in HPLMN as in step 3b-2. For the V-SMF removal case, the steps 4 to 10 are skipped.

(V-SMF insertion case) The (target) V-SMF retrieves SM context from H-SMF using Nsmf_PDUSession_Context Request/Response, followed by the Nsmf_PDUSession_Context Request/Response.

(V-SMF change case) The target V-SMF retrieves SM context from the source V-SMF using Nsmf_PDUSession_Context Request/Response indicating HR-SBO support in the Request in the case of an intra-PLMN V-SMF case. In step 4b, if source and target V-SMFs belong to same VPLMN, the SM context from the source V-SMF includes Authorization Result for HR-SBO, VPLMN Specific Offloading Information, and (if previously received by source V-SMF from H-SMF) the HPLMN address information, and the DNS Server address provided by the HPLMN.

As in step 4 of Figure 6.7.2.6-1, the (target) V-SMF may invoke Neasdf_DNSContext_Create.

As in step 5 of Figure 6.7.2.6-1, the (target) V-SMF may perform UL CL/BP and local PSA insertion/change/removal.

The target V-SMF invokes Nsmf_PDUSession_Update Request to the H-SMF as in step 7 of Figure 6.7.2.6-1.

As in step 8 of Figure 6.7.2.6-1, the H-SMF invokes Nudm_SDM_Get service, authorizes the request for HR-SBO based on the SM subscription data, and retrieves the VPLMN Specific Offloading Policy from H-PCF in case the HR-SBO is authorized.

As in step 9 of Figure 6.7.2.6-1, once the HR-SBO is authorized, the H-SMF sends the VPLMN Specific Offloading Information in the Nsmf_PDUSession_Update Response message to the target V-SMF.

As in step 9 of Figure 6.7.2.6-1, the (target) V-SMF may configure the V-EASDF based on the received VPLMN Specific Offloading Information.

The (target) V-SMF may also update the configuration of the V-UPF based on the received VPLMN Specific Offloading Information.

As in step 6 of Figure 6.7.2.6-1, the target V-SMF (in the case of V-SMF removal, the H-SMF) answers to the target AMF with PDUSession_CreateSMContext Response.

The registration procedure continues as defined in clause 4.2.2.2.2 of TS 23.502 from step 18 on.

In the case of V-SMF removal or change, when, at step 17a of clause 4.23.4.3 of TS 23.502, receiving Nsmf_PDUSession_ReleaseSMContext Request from the source AMF, the source V-SMF initiates a Neasdf_DNSContext_Delete if a V-EASDF was used for the PDU Session. In the case of V-SMF insertion, when at step 9 the H-SMF sends to the V-SMF VPLMN Specific Offloading Information in Nsmf_PDUSession_Update Response, the DNS context in the old EASDF may be removed by the H-SMF using Neasdf_DNSContext_Delete service.

(V-SMF insertion or V-SMF change): The target V-SMF sends the DNS information for the UE (received at step 9) and EAS rediscovery indication via PCO in a PDU Session Modification Command sent to the UE. (In the case of V-SMF removal): the H-SMF sends the DNS information (received at step 3) for the UE and EAS rediscovery indication via PCO in a PDU Session Modification Command sent to the UE.

As in step 13 of Figure 6.7.2.6 -1, notification from H-SMF to the AF.

As in step 14 of Figure 6.7.2.6 -1: EAS discovery procedure by UE may take place.

The procedures described in clauses 6.7.2.6, 6.7.2.7 and 6.7.2.9 are performed: inter V-SMF inter-PLMN N2 handover or mobility registration (0a) in the HR-SBO case; or inter V-SMF intra-PLMN N2 handover or Xn handover or mobility registration update (0b) in the HR-SBO case.

In the case of the procedures happened in step 0a, if the AF had subscribed to the corresponding event and a serving PLMN change occurred towards a PLMN where local traffic offload is possible for the PDU Session, the H-SMF notifies the AF, indicating the new serving PLMN ID as well as HPLMN DNN and S-NSSAI for HR-SBO session. This may take place as soon as the H-SMF has received an indication of Handover Complete (see step 13 of Figure 6.7.2.6-1). This may trigger the AF triggered edge relocation / EAS rediscovery as defined in step 1b of Figure 6.2.3.3-1 and in step 4a of Figure 6.3.3.1.1-1.

For AF triggered EAS re-discovery and edge relocation via interacting with HPLMN, the AF may indicate the EAS rediscovery for the impacted applications, which are identified by Application Identifier(s), to the H-SMF via the H-PCF using the AF influence on traffic routing procedure as described in clause 4.3.6 of TS 23.502. The AF may also provide EAS IP replacement information and target DNAI together with an indication of the PLMN associated with this target DNAI, i.e. the serving PLMN ID.

For AF triggered EAS re-discovery and edge relocation via interacting with serving VPLMN, the AF may indicate the EAS rediscovery for the impacted applications via the V-NEF using the procedure described in clause 4.3.6 of TS 23.502. This may trigger step 2 of Figure 6.2.3.3-1 where the SMF that initiates PDU Session modification is the V-SMF that initiates Nsmf_PDUSession_Update request with the requested PCO. The AF may also provide EAS IP replacement information and target DNAI to the VPLMN (i.e. V-SMF). In this case, steps 3-4 are skipped.

(For AF triggered EAS re-discovery and edge relocation via interacting with HPLMN case): The AF traffic influence request information is sent to H-SMF via PCC rule. This may trigger step 2 of Figure 6.2.3.3-1 where the SMF that initiates the PDU Session modification is the H-SMF. The H-SMF issues a Nsmf_PDUSession_Update request which may contain EAS IP replacement information and target DNAI provided by AF in step 2. If the V-SMF cannot serve the target DNAI, it invokes a Nsmf_PDUSession_SMContextStatusNotify service operation to send the target DNAI to AMF, and the AMF selects a target V-SMF based on the target DNAI as described in clause 4.23.5.4 of TS 23.502 by replacing I-SMF with V-SMF. The target V-SMF retrieves SM context from the source V-SMF using Nsmf_PDUSession_Context Request/Response, containing Authorization Result for HR-SBO, EAS IP replacement information and target DNAI in the Request. The target V-SMF may select a new V-EASDF as described from steps 2 to 12 in Figure 6.7.2.6-1.

(For AF triggered EAS re-discovery and edge relocation via interacting with VPLMN case): The V-SMF initiates Nsmf_PDUSession_Update request with the EAS rediscovery indication and the impact field to the H-SMF, and the H-SMF initiates Nsmf_PDUSession_Update Response towards the (target) V-SMF including the PCO information to be sent to the UE as described in step 2 of Figure 6.2.3.3-1. In intra-PLMN V-SMF change, the target V-SMF may use the source and target DNAI to determine the Impact field to be sent to the UE. In inter-PLMN mobility, the target V-SMF provides EAS rediscovery information without an Impact field.

The V-SMF may initiate PDU Session Modification command including the PCO to the UE. The PCO may include EAS rediscovery indication (optional) and the impact field (optional).

The V-SMF may configure the V-UPF (UL CL and L-PSA) with EAS IP replacement information.