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full Contents for  TS 23.316  Word version:   16.3.0

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7.2.4  Reachability proceduresWord-p. 47
The procedures described in TS 23.502, clause 4.2.5 are not applicable for 5G-RG and FN-RG access via W-5GAN.
7.2.5  AN Release
7.2.5.1  General
The AN Release procedure via W-5GAN access is used by the W-5GAN or the AMF to release the logical NG-AP signalling connection and the associated N3 User Plane connections between the W-5GAN and the 5GC.
7.2.5.2  5G-RG AN Release via W-5GAN
The procedure will move the 5G-RG from CM-CONNECTED to CM-IDLE in AMF, and all 5G-RG related context information is deleted in the W-AGF.
Both W-AGF initiated and AMF-initiated AN release in the W-5GAN procedures are shown in Figure 7.2.5-1.
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Step 1.
The 5G-RG has already registered in the 5GC and may have established one or multiple PDU Sessions.
Step 2.
The W-AGF detects that the 5G-RG is not reachable.
Step 3.
The W-AGF sends a N2 UE Context Release Request message to the AMF This step is equivalent to step 1b of Figure 4.2.6-1.
NOTE 1:
The triggers for W-AGF to send UE Context Release Request are defined by BBF in [9] and in CableLabs WR-TR-5WWC-ARCH [27] and may e.g. include events where W-AGF has lost of synchronisation of physical link, loss of PPPoE session, or detects that the RG has been replaced.
NOTE 2:
AN Release procedure can also be triggered by an AMF internal event and in that case step 2 and step 3 do not take place.
Step 4.
AMF to W-AGF: If the AMF receives the N2 UE Context Release Request from W-AGF or if due to an internal AMF event the AMF wants to release N2 signalling, the AMF sends an N2 UE Context Release Command (Cause) to the W-AGF. The cause indicated is cause from step 3 or a cause due to internal AMF event. This step is equivalent to step 2 of Figure 4.2.6-1.
Step 5.
If the W-CP signalling connection and W-UP resources has not been released yet, the W-AGF releases the W-CP connection and W-UP resources with a procedure out of scope of 3GPP. The W-AGF sends to the 5G-RG the indication of the release reason if received in step 4.
Step 6.
W-AGF to AMF: The W-AGF confirms the release of the 5G-RG-associated N2-logical connection by returning N2 UE Release Complete (list of PDU Session ID(s) with active N3 user plane) to the AMF as in step 4 defined in clause 4.2.6. The AMF marks the 5G-RG as CM-IDLE state in non-3GPP access.
Step 7.
For each of the PDU Sessions in the N2 UE Context Release Complete, the steps 5 to 7 in TS 23.502, clause 4.2.6 are performed (PDU Session Update SM Context). After the AMF receives the Nsmf_PDUSession_UpdateSMContext Response as in step 7 of TS 23.502, clause 4.2.6, the AMF considers the N3 connection as released. If list of PDU Session ID(s) with active N3 user plane is included in step 3, then this step is performed before step 4.
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7.2.5.3  FN-RG AN Release via W-5GANWord-p. 49
The AN release procedure for the FN-RG is similar to that of 5G-RG described in clause 7.2.5.2 but with the following differences:
  • The 5G-RG is replaced with a FN-RG.
  • In step 5, the W-AGF may initiate the release of the L-W-CP signalling and L-W-UP resources between the FN-RG and W-AGF based on legacy protocols.
NOTE:
The message exchanges between the FN-RG and W-AGF are based on legacy protocols in the wireline access network as described in clause 6.2.2.
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7.2.6  N2 procedures
7.2.6.0  General
This clause specifies delta for N2 procedures defined in TS 23.502, clause 4.2.7 for 5G-RG and FN-RG.
7.2.6.1  N2 procedures via W-5GAN Access
At power up, restart and when modifications are applied, the W-AGF node and AMF use non-UE related N2 signalling to exchange configuration data. The N2 Configuration as described in TS 23.502, clause 4.2.7.1 is used with the following differences:
  • The 5G-AN corresponds to the W-AGF.
The Creating NGAP UE-TNLA-bindings during Registration and Service Request procedure as described in TS 23.502, clause 4.2.7.2.1 is used for 5G-RG connecting to 5GC via W-5GAN Access, with the following differences:
  • The 5G-AN corresponds to the W-AGF.
  • The UE corresponds to 5G-RG.
The Creating NGAP UE-TNLA-bindings during Registration and Service Request procedure as described in TS 23.502, clause 4.2.7.2.1 is used for FN-RG connecting to 5GC via W-5GAN Access with the following differences:
  • The 5G-AN corresponds to the W-AGF.
  • The UE corresponds to W-AGF on behalf of FN-RG.
  • If the W-AGF does not have any UE identities (i.e. a GUAMI or a 5G-S-TMSI) for the FN-RG, e.g. during Initial Registration procedure, the following differences are further applied:
    • In step 2, the W-AGF shall handle the access specific messages received from the FN-RG as described in BBF WT-456 [9] and WT-457 [10], e.g. PPPoE messages, and does not forward them to the AMF via the selected TNL association. Instead, the W-AGF shall send NAS messages on behalf of the FN-RG to the AMF via the selected TNL association.
    • Step 3 can only take place during the Initial Registration procedure.
  • The AMF may decide to modify the NGAP UE-TNLA-binding toward other 5G-AN nodes such as W-AGF. This is done if AMF is changed and old AMF have existing NGAP UE-TNLA-bindings toward another W-AGF.
The Creating NGAP UE-TNLA-bindings during handovers as described in TS 23.502, Clause 4.2.7.2.2 is not applicable to the scenario when 5G-RG or FN-RG is access to 5GC via W-5GAN.
Re-Creating NGAP UE-TNLA-bindings subsequent to NGAP UE-TNLA-binding release as described in TS 23.502, clause 4.2.7.2.3 is used for 5G-RG connecting to 5GC via W-5GAN Access with the following exceptions:
  • The 5G-AN corresponds to the W-AGF.
  • The UE corresponds to 5G-RG.
Re-Creating NGAP UE-TNLA-bindings subsequent to NGAP UE-TNLA-binding release as described in TS 23.502, clause 4.2.7.2.3 is used for FN-RG connecting to 5GC via W-5GAN Access with the following exceptions:
  • The 5G-AN corresponds to the W-AGF.
  • The UE corresponds to W-AGF on behalf of FN-RG.
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7.2.7  5G-RG and FN-RG Capability Match Request procedureWord-p. 50
This procedure is not applicable to 5G-RG and FN-RG access via wireline access.

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