6.4 Detach and PDN Disconnection for S2a

23.4023GPPArchitecture enhancements for non-3GPP accessesRelease 18TS

6.4.1 UE/Trusted Non-3GPP IP Access Network Initiated Detach and UE/Trusted Non-3GPP IP Access requested PDN Disconnection Procedure with PMIPv6

6.4.1.1 Non-Roaming, Home Routed Roaming and Local Breakout Case

The procedure in this clause applies to both Detach Procedures, including UE or Trusted non-3GPP access initiated detach procedure, and UE/Trusted non-3GPP Access requested PDN disconnection procedure when supported by the Trusted non-3GPP access.

The UE can initiate the detach procedure, e.g. when the UE is power off. The Trusted Non-3GPP Access Network can initiate the detach procedure due to administrative reasons or detecting the UE’s leaving by, e.g. Link-layer event specific to the access technology (refer to PMIPv6 specification, RFC 5213 [8], for more information).

Figure 6.4.1.1-1: UE/Trusted Non-3GPP Access Network initiated detach procedure or PDN-disconnection with PMIPv6

For detach procedure and in case of connectivity with multiple PDNs, the steps 2 to 6 are repeated for each PDN the UE is connected to.

For UE-requested PDN disconnection procedure, steps 2 to 6 are performed for the PDN that the UE requested disconnection from.

This procedure applies to the Non-Roaming (Figure 4.2.2-1), Roaming (Figure 4.2.3-1) and Local Breakout (Figure 4.2.3-4) cases. For the Roaming and Local Breakout cases, the vPCRF forwards messages between the non-3GPP access and the hPCRF. In the Local Breakout case, the vPCRF forwards messages between the PDN GW and the hPCRF. In the Roaming and LBO cases, the 3GPP AAA Proxy serves as an intermediary between the Trusted Non-3GPP IP Access and the 3GPP AAA Server in the HPLMN. In the non-roaming case, the vPCRF is not involved at all.

If dynamic policy provisioning is not deployed, the optional steps of interaction between the gateways and PCRF do not occur. Instead, the PDN GW may employ static configured policies.

1) The UE or the Trusted Non-3GPP Access Network triggers either detach or disconnection from a specific PDN by an access technology specific procedure. In the case of PDN disconnection of a PDN connection out of multiple PDN connections, the UE shall use the access specific mechanism for differentiating the PDN connections towards the same APN (see clause 6.8.1.1) to indicate the PDN connection to be deregistered and allow the Mobile Access Gateway in the Trusted Non-3GPP IP Access to select the corresponding PDN connection identity needed in step 3 (e.g. the UE informs the Trusted Non-3GPP access of the prefix to be disconnected).

2) The Trusted Non-3GPP Access Network initiates the Gateway Control Session Termination Procedure with the PCRF as specified in TS 23.203 [19]. The Trusted Non-3GPP Access Network no longer applies QoS policy to traffic flows for this UE.

3) The Mobile Access Gateway (MAG) in the Trusted Non-3GPP IP Access sends a Proxy Binding Update (MN NAI, APN, lifetime=0) message to the PDN GW with lifetime value set to zero, indicating de-registration. The MN NAI identifies the UE to deregister from the PDN GW. When only one PDN connection to the given APN is allowed the APN is needed in order to determine which PDN to deregister the UE from, as some PDN GWs may support multiple PDNs. When multiple PDN connections to the given APN are supported the APN and the PDN connection identity are needed in order to determine which PDN to deregister the UE from.

4) The PDN GW informs the 3GPP AAA Server of the PDN disconnection. If the UE no longer has any context in the 3GPP AAA Server, the 3GPP AAA Server notifies the HSS as described in clause 12.1.2.

5) The PDN GW deletes the IP CAN session associated with the UE and executes a PCEF-Initiated IP CAN Session Termination Procedure with the PCRF as specified in TS 23.203 [19].

6) The PDN GW deletes existing entries implied in the Proxy Binding Update message from its Binding Cache and sends a Proxy Binding Ack (MN NAI, APN, lifetime=0) message to the MAG.

7) Non-3GPP specific resource release procedure is executed. The resources of Trusted Non-3GPP Access Network are released. In case of disconnection from a PDN, if the PDN from which the UE is disconnected was the only PDN that the UE was connected to, detach related procedures may be performed in the Trusted non-3GPP IP access.

6.4.1.2 Chained PMIP-based S8-S2a Roaming Case

This clause defines the UE/Trusted Non-3GPP IP Access Network-initiated detach procedure UE-requested PDN disconnection procedure for PMIP-based S8-S2a chaining. This procedure also applies to UE/ePDG-initiated detach procedure for PMIP-based S8-S2b chaining.

Figure 6.4.1.2-1: UE/ePDG/Trusted Non-3GPP Access Network initiated detach procedure for chained PMIP-based S8-S2a/b roaming scenarios and PDN-disconnection for chained PMIP-based S8-S2a

For detach procedure and in case of connectivity with multiple PDNs, the steps 2 to 7 are repeated for each PDN the UE is connected to.

For UE-requested PDN disconnection procedure for chained PMIP-based S8-S2a, steps 2 to 7 are performed for the PDN that the UE requested disconnection from.

1) For detach, initial steps of the detach is performed as described in steps 1‑2 of clause 6.4.1.1 (for trusted non-3GPP access) and step 1 of clause 7.4.1.1 (for untrusted non-3GPP access). For UE-requested PDN disconnection in chained PMIP-based S8-S2a, steps 1-2 of clause 6.4.1.1 are performed.

2) The MAG in the Trusted Non-3GPP IP Access or ePDG sends a Proxy Binding Update (MN NAI, APN, lifetime=0) message to the Serving GW with lifetime value set to zero, indicating de-registration. The MN NAI identifies the UE to deregister from the PDN GW. When only one PDN connection to the given APN is allowed the APN is needed in order to determine which PDN to deregister the UE from, as some PDN GWs may support multiple PDNs. When multiple PDN connections to the given APN are supported the APN and PDN connection identity are needed in order to determine which PDN to deregister the UE from.

3) The Serving GW deletes all existing entries implied in the Proxy Binding Update message from its Binding Cache and releases all associated resources (e.g. GRE tunnel), and then sends a corresponding Proxy Binding Update message (as in step 2) to the PDN GW in the HPLMN.

4) The PDN GW informs the 3GPP AAA Server of the PDN disconnection. If the UE no longer has any context in the 3GPP AAA Server, the 3GPP AAA Server notifies the HSS as described in clause 12.1.2.

5) The PDN GW initiates the PCEF-initiated IP CAN Session Termination Procedure, as specified in TS 23.203 [19].

6) The PDN GW deletes existing entries implied in the Proxy Binding Update message from its Binding Cache and releases all associated resources, and then sends a Proxy Binding Ack (MN NAI, APN, lifetime=0) message to the Serving GW in the VPLMN.

7) The Serving GW sends a corresponding Proxy Binding Ack message (as in step 6) to the MAG function in Trusted Non-3GPP IP Access.

8) The detach procedure is completed as described in step 7 of clause 6.4.1.1 (for trusted non-3GPP access) and step 6 of clause 7.4.1.1 (for untrusted non-3GPP access). In case of disconnection from a PDN, if the PDN from which the UE is disconnected was the only PDN that the UE was connected to, detach related procedures may be performed.

6.4.2 HSS/AAA Initiated Detach Procedure with PMIPv6

6.4.2.1 Non-Roaming, Home Routed Roaming and Local Breakout Case

HSS/AAA-initiated detach procedure with PMIPv6 is illustrated in figure 6.4.2.1-1. The HSS can initiate the procedure e.g. when the user’s subscription is removed. The 3GPP AAA Server can initiate the procedure, e.g. instruction from O&M, timer for re-authentication/re-authorization expired.

If the HSS/AAA-initiated detach procedure has been initiated to delete the UE from the Evolved Packet Core, the HSS/AAA server shall initiate the detach procedure for each of the access systems to which the UE is registered.

Figure 6.4.2.1-1: HSS/AAA-initiated detach procedure with PMIPv6

This procedure applies to the Non-Roaming (Figure 4.2.2-1), Roaming (Figure 4.2.3-1) and Local Breakout (Figure 4.2.3-4) cases. For the Roaming and Local Breakout cases, the vPCRF forwards messages between the non-3GPP access and the hPCRF. In the Local Breakout case, the vPCRF forwards messages between the PDN GW and the hPCRF. In the Roaming and LBO cases, the 3GPP AAA Proxy serves as an intermediary between the Trusted Non-3GPP IP Access and the 3GPP AAA Server in the HPLMN. In the non-roaming case, the vPCRF is not involved at all.

1) The HSS/AAA sends a Detach Indication message to the MAG in the Trusted Non-3GPP Access Network to detach a specific UE.

2) This includes the procedure after step 1 as in figure 6.4.1.1-1.

3) The MAG of the Trusted Non-3GPP Access Network sends a Detach Ack message to the 3GPP AAA Server. If the detach procedure was initiated from the 3GPP AAA Server and if the UE no longer has any context in the 3GPP AAA Server, the 3GPP AAA Server communicates the HSS as described in clause 12.1.2. If the detach procedure was initiated by HSS, the 3GPP AAA Server replies to the HSS as described in clause 12.1.3.

NOTE: The HSS/AAA may also send a detach indication message to the PDN GW. The PDN GW does not remove the PMIP tunnels on S2a, since the MAG in the non-3GPP access is responsible for removing the PMIP tunnels on S2a. The PDN GW acknowledges the receipt of the detach indication message to the 3GPP AAA Server.

6.4.2.2 Chained PMIP-based S8-S2a Roaming Case

This clause defines the HSS/AAA-initiated detach procedure for PMIP-based S8-S2a chaining. This procedure also applies for PMIP-based S8-S2b chaining.

If the HSS/AAA-initiated detach procedure has been initiated to delete the UE from the Evolved Packet Core, the HSS/AAA server shall initiate the detach procedure for each of the access systems to which the UE is registered.

Figure 6.4.2.2-1: HSS/AAA-initiated detach procedure for chained PMIP-based S8-S2a/b roaming scenarios

1) The HSS/AAA sends a Detach Indication message to the MAG in the Trusted Non-3GPP Access Network or ePDG to detach a specific UE.

2) The detach procedure as described in steps 2‑8 of clause 6.4.1.2 is performed.

3) The MAG of the Trusted Non-3GPP Access Network or ePDG sends a Detach Ack message to the 3GPP AAA Server. If the detach procedure was initiated from the 3GPP AAA Server and if the UE no longer has any context in the 3GPP AAA Server, the 3GPP AAA Server communicates the HSS as described in clause 12.1.2. If the detach procedure was initiated by HSS, the 3GPP AAA Server replies to the HSS as described in clause 12.1.3.

NOTE: The HSS/AAA may also send a detach indication message to the PDN GW. The PDN GW does not remove the PMIP tunnels on S2a, since the MAG in the non-3GPP access is responsible for removing the PMIP tunnels on S2a. The PDN GW acknowledges the receipt of the detach indication message to the 3GPP AAA Server.

6.4.3 UE-initiated Detach Procedure and UE-Requested PDN Disconnection Procedure with MIPv4 FACoA

The procedure in this clause applies to both UE initiated Detach Procedure and UE-requested PDN disconnection procedure with MIPv4 FACoA when supported by the Trusted non-3GPP access.

The UE can initiate this procedure, e.g. when the UE is powered off.

Figure 6.4.3-1: UE-initiated detach procedure with MIPv4 FACoA

NOTE: AAA proxy and vPCRF are only used in the case of home routed roaming (Figure 4.2.3-1) and local breakout (Figure 4.2.3-4).

For detach procedure and in case of connectivity with multiple PDNs, the steps 1 to 9 are repeated for each PDN the UE is connected to.

For UE-requested PDN disconnection procedure, steps 1 to 9 are performed for the PDN that the UE requested disconnection from.

The optional interaction steps between the gateways and the PCRF in the procedures only occur if dynamic policy provisioning is deployed. Otherwise policy may be statically configured with the gateway.

This procedure applies to the Non-Roaming (Figure 4.2.2-1), Roaming (Figure 4.2.3-1) and Local Breakout (Figure 4.2.3-4) cases. For the Roaming and Local Breakout cases, the vPCRF forwards messages between the non-3GPP access and the hPCRF. In the Local Breakout case, the vPCRF forwards messages between the PDN GW and the hPCRF. In the Roaming and LBO cases, the 3GPP AAA Proxy serves as an intermediary between the Trusted Non-3GPP IP Access and the 3GPP AAA Server in the HPLMN. In the non-roaming case, the vPCRF is not involved at all.

1) The UE sends a MIPv4 Registration Request (RRQ) (MN-NAI, Home Address, Home Agent Address, Care-of Address, lifetime = 0) message to the Foreign Agent (FA) in the Trusted Non-3GPP Access Network with lifetime value set to zero, indicating de-registration. The MN-NAI identifies the UE. The Home Address includes UE Home IP addresses, the Home Agent Address contains the IP address of Home Agent. Care-of Address indicates the CoA used by the UE for the binding.

2) The Trusted Non-3GPP Access Network initiates the Gateway Control Session Termination Procedure with the PCRF as specified in TS 23.203 [19]. The Trusted Non-3GPP Access Network no longer applies QoS policy to traffic flows for this UE.

3) The FA relays this MIPv4 RRQ (MN-NAI, lifetime = 0) message to the PDN GW.

4) The selected PDN GW obtains Authentication and Authorization information from the AAA/HSS.

5) The PDN GW informs the 3GPP AAA Server of the PDN disconnection. If the UE no longer has any context in the 3GPP AAA Server, the 3GPP AAA Server notifies the HSS as described in clause 12.1.2.

6) The PDN GW deletes the IP CAN session associated with the UE and executes a PCEF-Initiated IP‑CAN Session Termination Procedure with the PCRF as specified in TS 23.203 [19].

7) The PDN GW sends a MIPv4 Registration Reply (RRP) (MN-NAI, Home Address, Home Agent Address, Lifetime=0) message to the FA.

8) Any time after step 7, the FA relays this MIPv4 RRP (MN-NAI, Home Address, Home Agent Address, Lifetime=0) message to the UE.

9) After step 7, Non-3GPP specific resource release procedure is executed.

6.4.4 Network Initiated Detach Procedure with MIPv4 FACoA

Trusted Non-3GPP Access Network initiated detach procedure with MIPv4 FACoA Mode is illustrated in Figure 6.4.4‑1. The Trusted Non-3GPP Access Network can initiate this procedure due to administration reason or detecting the UE’s leaving by, e.g. Link-layer event specific to the access technology (see RFC 3543 [25] for more information).

Figure 6.4.4-1: Trusted Non-3GPP Access Network initiated detach procedure with MIPv4 FACoA

NOTE: AAA proxy and vPCRF are only used in the case of home routed roaming (Figure 4.2.3-1) and local breakout (Figure 4.2.3-4).

The optional interaction steps between the gateways and the PCRF in the procedures only occur if dynamic policy provisioning is deployed. Otherwise policy may be statically configured with the gateway.

This procedure applies to the Non-Roaming (Figure 4.2.2-1), Roaming (Figure 4.2.3-1) and Local Breakout (Figure 4.2.3-4) cases. For the Roaming and Local Breakout cases, the vPCRF forwards messages between the non-3GPP access and the hPCRF. In the Local Breakout case, the vPCRF forwards messages between the PDN GW and the hPCRF. In the Roaming and LBO cases, the 3GPP AAA Proxy serves as an intermediary between the Trusted Non-3GPP IP Access and the 3GPP AAA Server in the HPLMN. In the non-roaming case, the vPCRF is not involved at all.

1) The Trusted Non-3GPP Access Network detects the UE’s leaving and initiates a Gateway Control Session Termination Procedure with the PCRF as specified in TS 23.203 [19]. The Trusted Non-3GPP Access Network no longer applies QoS policy to traffic flows for this UE.

2) The FA sends a Registration Revocation (Home Address, Home Agent Address, Care-of Address) message (see RFC 3543 [25]) to the PDN GW.

3) The PDN GW informs the 3GPP AAA Server of the PDN disconnection. If the UE no longer has any context in the 3GPP AAA Server, the 3GPP AAA Server notifies the HSS as described in clause 12.1.2.

4) The PDN GW deletes the IP CAN session associated with the UE and executes a PCEF-Initiated IP‑CAN Session Termination Procedure with the PCRF as specified in TS 23.203 [19].

5) The PDN GW sends a Registration Revocation Ack (Home Address) message (see RFC 3543 [25]) to the FA.

6) The Trusted Non-3GPP Access Network executes a specific resource release procedure.

6.4.5 HSS/AAA-initiated detach procedure with MIPv4 FACoA

HSS/AAA-initiated detach procedure with MIPv4 FACoA Mode is illustrated in Figure 6.4.5-1. The HSS can initiate the procedure e.g. when the user’s subscription is removed. The 3GPP AAA Server can initiate the procedure, e.g. instruction from O&M, timer for re-authentication/re-authorization expired.

If the HSS/AAA-initiated detach procedure has been initiated to delete the UE from the Evolved Packet Core, the HSS/AAA server shall initiate the detach procedure for each of the access systems to which the UE is registered.

Figure 6.4.5-1: HSS/AAA-initiated detach procedure with MIPv4 FACoA

NOTE 1: AAA proxy and vPCRF are only used in the case of home routed roaming (Figure 4.2.3-1) and local breakout (Figure 4.2.3-4).

The optional interaction steps between the gateways and the PCRF in the procedures only occur if dynamic policy provisioning is deployed. Otherwise policy may be statically configured with the gateway.

This procedure applies to the Non-Roaming (Figure 4.2.2-1), Roaming (Figure 4.2.3-1) and Local Breakout (Figure 4.2.3-4) cases. For the Roaming and Local Breakout cases, the vPCRF forwards messages between the non-3GPP access and the hPCRF. In the Local Breakout case, the vPCRF forwards messages between the PDN GW and the hPCRF. In the Roaming and LBO cases, the 3GPP AAA Proxy serves as an intermediary between the Trusted Non-3GPP IP Access and the 3GPP AAA Server in the HPLMN. In the non-roaming case, the vPCRF is not involved at all.

1) The HSS/AAA sends a detach indication message to the FA in the Trusted Non-3GPP Access Network to detach a specific UE.

2) This includes the procedure in figure 6.4.4-1.

3) The FA sends a Detach Ack message to the 3GPP AAA Server. If the detach procedure was initiated from the 3GPP AAA Server and if the UE no longer has any context in the 3GPP AAA Server, the 3GPP AAA Server communicates the HSS as described in clause 12.1.2. If the detach procedure was initiated by HSS, the 3GPP AAA Server replies to the HSS as described in clause 12.1.3.

NOTE 2: The HSS/AAA may also send a detach indication message to the PDN GW. The PGW does not remove the MIPv4 tunnels, since the MIPv4 FA in the non-3GPP access is responsible for removing the MIPv4 tunnels. The PDN GW acknowledges the receipt of the detach indication message to the 3GPP AAA Server.