Content for TS 23.548 Word version: 18.6.0

1… 4… 4.3 5… 6… 6.2.2.3… 6.2.3… 6.2.3.2.3… 6.2.3.2.5… 6.2.3.3… 6.3… 6.4… 6.5… 6.6 6.7… 6.7.2.4… 6.7.2.6… 6.7.3… 6.8… 7… A B… F…

6.7.3 EAS Re-discovery and Edge Relocation Procedure 6.7.3.1 General 6.7.3.2 Network triggered EAS change in HR-SBO context 6.7.4 AF request on PDU Sessions supporting HR-SBO
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6.7.3 EAS Re-discovery and Edge Relocation Procedure p. 69

6.7.3.1 General p. 69

The EAS re-discovery and edge relocation in VPLMN can be triggered due to UE mobility, AF interacting with HPLMN, or AF interacting with VPLMN.

6.7.3.2 Network triggered EAS change in HR-SBO context p. 70

Figure 6.7.3.2-1 shows the procedure of EAS re-discovery and edge relocation when HR-SBO is supported and allowed in the target serving PLMN.

Reproduction of 3GPP TS 23.548, Fig. 6.7.3.2-1: Network triggered EAS rediscovery and edge relocation in HR-SBO context procedure

Figure 6.7.3.2-1: Network triggered EAS rediscovery and edge relocation in HR-SBO context procedure

Step 0.

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.

Step 1.

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 and H-SMF may include capability of supporting EAS IP replacement in 5GC with PLMN ID of VPLMN. 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.

Step 2a.

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-PCF via the H-NEF for the H-AF untrusted, or directly to the H-PCF for the AF trusted, then transfer to the H-SMF and optional H-NEF, H-UDR 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 in the case that the VPLMN (V-SMF) supports EAS IP replacement capability and has already notified this capability information to AF (directly or via H-SMF/H-NEF).

Step 2b.

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. If the V-SMF cannot serve the target DNAI, it triggers V-SMF change/removal, and the EAS IP replacement information and target DNAI may be provided in SM context as described in clause 6.7.2.6.

Step 3a.

(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 . The Nsmf_PDUSession_Update request includes policies due to AF provided traffic influence information, which may also 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.

Step 3b.

(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.

Step 4.

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).

Step 5.

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

6.7.4 AF request on PDU Sessions supporting HR-SBO p. 71

For HR-SBO PDU Sessions, the AF may interact with VPLMN or HPLMN in order to send an AF request to influence traffic routing. The AF is assumed to check whether it has an SLA with the serving PLMN. If the AF has no SLA with the serving VPLMN, the AF interacts with HPLMN (H-NEF or H-PCF) to issue traffic influence requests.

If the AF has an SLA with the serving VPLMN, the AF in VPLMN may send to V-NEF an AF request to influence traffic routing. The AF request for the HR-SBO PDU Session from the AF is stored as Application Data (Data Subset = AF traffic influence request information) in the UDR of VPLMN as described in clause 4.3.6 of TS 23.502. NEF determine if HR-SBO is applicable as described in clause 4.3.6 of TS 23.502). To obtain the AF traffic influence request information, the V-SMF managing the PDU Session supporting HR-SBO subscribes to the NEF in VPLMN for notification of Application Data modification as specified in clause 4.3.6 of TS 23.502.

If the AF has no SLA with the serving VPLMN, the AF in HPLMN may send to H-NEF (or H-PCF directly) an AF request to influence traffic routing (e.g. for the purpose of subscription to UP path management events on HR-SBO Sessions in VPLMN) for HR-SBO session in VPLMN. In response to receiving the traffic influence request, the H-PCF may generate or update one or more PCC rules based on the traffic influence request. PCC rule that may contain information about the VPLMN DNAI(s) towards which the traffic routing should apply, and H-PCF sends an update notification to H-SMF.

The H-SMF may send to the V-SMF the received Application Function influence on traffic routing Enforcement Control (i.e. received in PCC rules from the H-PCF).

The H-SMF may also determine Application Function influence on traffic routing Enforcement Control information related to the VPLMN and provides the VPLMN-related Application Function influence on traffic routing Enforcement Control information to the V-SMF due to AF triggered EAS re-discovery or edge relocation as described in step 3a of Figure 6.7.3.2-1.