Content for  TS 33.128  Word version:  18.7.0

For Phase-1 of HR LI, the following LI functions are provisioned over LI_X1 by the LIPF using the X1 protocol defined in ETSI TS 103 221-1 [7] with the LIPF playing the role of ADMF and the following LI functions playing the role of NE as per the reference model depicted in ETSI TS 103 221-1 [7]:

• BBIFF-C present in the SMF.
• BBIFF-C present in the SGW-C.
• BBIFF present in the SGW.
• LMISF-IRI.

As described in clause 7.10.1, the Phase-1 of HR LI applies to all inbound roaming UEs that use the IMS-based services with home-routed roaming. The target identities "HR" and "IMSSignaling" are used for Phase-1 of HR LI.

The minimum details of LI_X1 ActivationTask message is shown in Table 7.10.3.2-2.

The LMISF-IRI is listed as the delivery endpoint over LI_X2_LITE for xIRI generated by the BBIFF-C/BBIFF and for the xCC generated by the BBIFF-U/BBIFF. The provisioning of LMISF-IRI is to enable it to receive the xIRIs and xCC sent from the BBIFF-C (SMF, SGW-C), BBIFF-U (UPF, SGW-U) and BBIFF (SGW). As an alternate deployment option, LMISF-IRI may be presumed to be enabled to receive such xIRI/xCC by default. This clause does not apply to such alternate deployment option. Table 7.10.3.2-4 shows the minimum details of the LI_X1 ActivateTask message used for provisioning the LMISF-IRI for Phase-1.

LI_X2_LITE is an interface between the BBIFF-C/BBIFF to the LMISF-IRI. The xIRIs are generated at the BBIFF-C/BBIFF and are sent over LI_X2_LITE interface to the LMISF-IRI. These xIRIs are applicable to HR LI Phase-1 only. For N9HR LI, the BBIFF-C present in the SMF shall generate the xIRIs as described in clause 7.10.3.3.2. For S8HR LI, the BBIFF-C present in the SGW-C and BBIFF present in the SGW shall generate the xIRIs as defined in clause 7.10.3.3.3. The xIRIs are generated only when the following prior conditions are met:

• ActivateTask with target identity "HR" and "IMSSignaling" is received with X2 being included in the delivery type.
• The MCC + MNC of the Operator Identifier field of the DNN (for N9HR) or APN (for S8HR) is different from the MCC+MNC configured in the SMF (N9HR) or SGW-C/SGW (S8HR) - see clause 6.1.6.2.2 of TS 29.502 and clause 9.1.2 of TS 23.003.
• The Network Identifier field of DNN (for N9HR) or APN (for S8HR) contains "IMS" (IMS services) - see GSMA IR.88 [67].

The first point is indicating that HR LI is enabled (see clause 7.10.3.2.2). The second point is telling that the UE is an inbound roamer with home-routed based roaming. The third point is telling that the PDU session/PDN connection is for IMS services.

The BBIFF-C present in the SMF shall generate the following xIRI when the prior conditions defined in clause 7.10.3.3.1 are met:

• N9HRPDUSessionInfo.

The main purpose of the xIRI is to report the UE location, PDU session ID and the SMF identity. The scenarios that result in the above xIRI are listed below and apply to all inbound roaming UEs with home-routed roaming and using IMS services:

• PDU session is established with the creation of a default QoS flow for IMS signaling.
• PDU session is modified with the creation of a dedicated QoS flow used for IMS media.
• PDU session is modified with the updates to the QoS flow.
• PDU session is modified with the deleting of dedicated QoS flow used for IMS media.
• PDU session is deleted.
• MA PDU session is created, modified or deleted.
• SMF relocation.
• New UE location due to UE requested or network initiated service request.
• New UE location due to hand-over situations including EPS to 5GS handover.
• New UE location due to tracking area updates or routing area updates.
• New SMF from the SMF set is taking over the PDU session.
• HR LI is enabled with an established PDU session.

The exact trigger for the xIRI is subject to implementation, however, the following can be used as a general guidance along with observing the prior conditions listed in clause 7.10.3.3.1:

• SMF receives the Nsmf_PDU_Session_Create response message with n1SmInfoToUe IE containing the PDU SESSION ESTABLISHMENT ACCEPT (see TS 29.502) from the H-SMF and sends the NAS message (via AMF) PDU SESSION ESTABLISHMENT ACCEPT to the UE as a part of PDU session establishment procedures. This may also happen with MA PDU session establishment procedures, or during handover procedures with access type change, or as a part of SMF relocation procedures.
• SMF receives an Nsmf_PDUSession_UpdateSMContext request from the AMF with a new UE location. This may happen whenever a PDU session or a MA PDU session is modified with the addition, modification or deletion of a dedicated QoS flow. This may also happen for UE-initiated or network-initiated service request procedures, or as a part of the handover procedures, or as a part of the tracking area update procedures.
• When a new SMF (e.g. in the SMF set) takes over the control for the PDU session.
• When an ActivateTask is received from the LIPF over LI_X1 (see clause 7.10.3.2.2) to enable the HR LI, the BBIFF-C present in the SMF detects that a PDU session for IMS services is already established for an inbound roaming UE with home-routed roaming.

The contents of xIRI N9HRPDUSessionInfo record is shown in Table 7.10.3.3-1 below.

The xIRIs shall include the Network Function ID (NFID), a conditional attribute field as defined in ETSI TS 103 221-2 [8], with the V-SMF identity. Handling of this xIRI within the LMISF-IRI is described in clause 7.10.3.4.

The BBIFF-C present in the SGW-C and BBIFF present in the SGW shall generate the following xIRI for the purpose of S8HR LI when the prior conditions defined in clause 7.10.3.3.1 are met:

• S8HRBearerInfo.

The main purpose of the xIRI is to report the UE location and the SGW/SGW-C identity to the LMISF-IRI. This xIRI is generated for the following scenarios that apply to all inbound roaming UEs with home-routed roaming and using IMS services:

• PDN connection is established with the creation of a default bearer for IMS signaling.
• Dedicated bearer is activated for the for IMS media.
• Dedicated bearer is updated for IMS media.
• Dedicated bearer is deactivated for IMS media.
• PDN is disconnected.
• SGW-C/SGW relocation.
• New UE location due to UE requested or network initiated service request.
• New UE location due to hand-over situations including 5GS to EPS handover.
• New UE location due to tracking area updates or routing area updates.
• HR LI is enabled with an established PDN connection with the creation of a default bearer.

The exact trigger for the xIRI is subject to implementation, however, the following can be used as a general guidance observing the prior conditions listed in clause 7.10.3.3.1:

• SGW-C/SGW receives a Create Session Response from the PGW-C/PGW and forwards the same to the MME as a part of PDN connection establishment procedures that creates the default bearer used for IMS signaling or as a part of the handover procedures that results in the SGW-C/SGW relocation or 5GS to EPS relocation.
• SGW-C/SGW receives a Create Session Response from the MME and forwards the same to the PGW-C/PGW as a part of dedicated bearer activation procedure on a PDN connection used for IMS media.
• SGW-C/SGW receives an Update Bearer Response from MME and forwards the same to the PGW-C/PGW as a part of bearer update procedures with or without the bearer update QoS.
• SGW-C/SGW receives a Delete Bearer Response from MME and forwards the same to the PGW-C/PGW as a part of bearer deactivation procedure.
• SGW-C/SGW receives a Delete Session Request from the MME and forwards the same to the PGW-C/PGW as a part of PDN disconnection procedures. The procedures potentially have the last known UE location.
• SGW-C/SGW receives a Create Session Request from the MME and sends a Modify Bearer Request to the PGW-C/PGW as a part of tracking area/routing area update procedures with a change of SGW-C/SGW. The procedures potentially have a new UE location.
• SGW-C/SGW receives a Modify Bearer Request from the MME and sends the same to the PGW-C/PGW as a part of Service Request handling procedures, or hand-over procedures, or tracking area/routing area update procedures without a change in the SGW-C/SGW. The procedures potentially have a new UE location.
• When an ActivateTask is received from the LIPF over LI_X1 (see clause 7.10.3.2.2) to enable the HR LI, the BBIFF-C/BBIFF present in the SGW-C/SGW detects that a PDN connection with a default bearer used for IMS services is already established for an inbound roaming UE with home-routed roaming.

The details of the xIRI S8HRBearerInfo record is defined in Table 7.10.3.3-3 below.

All of the xIRIs listed above shall also include the Network Function ID (NFID), a conditional attribute field as defined in ETSI TS 103 221-2 [8], with the SGW-C/SGW identity. Handling of this xIRI within the LMISF-IRI is described in clause 7.10.3.4.

The LMISF-IRI that receives the xIRI, N9HRPDUSessionInfo record shall store or update the record with the information received in the xIRI (e.g. UE location) as applicable, for the future handling. The LMISF-IRI that receives the xIRI, S8HRBearerInfo record shall store or update the record with the information received in the xIRI (e.g. UE location) as applicable, for the future handling. The stored record is referred to LI_X2_LITE record in the present document.

For the N9HR LI related LI_X2_LITE records, the LMISF-IRI shall use the SUPI and PDU Session ID to uniquely associate a record with the inbound roaming UE. For S8HR LI related LI_X2_LITE records, the LMISF-IRI shall use the IMSI, Linked Bearer ID or the Bearer ID (when the Linked Bearer ID is not present) to uniquely associate a record with the inbound roaming UE.

With HR LI Phase-1, the user plane packets from the IMS signaling channel are delivered to the LMISF-IRI for all inbound roaming UEs with home-routed roaming. When BBIFF is separated into BBIFF-C and BBIFF-U, these user plane packets are captured at the BBIFF-U. In order to enable the BBIFF-U to do that function, the BBIFF-C triggers the BBIFF-U over the LI_T3 interface. The BBIFF-U delivers the user plane from the IMS signaling channel over the LI_X3_LITE-S interface to the LMISF-IRI.

When the BBIFF-C present in the SMF detects that a PDU session is established with IMS signaling related QoS Flow for an inbound roaming UE with home-routed roaming, it shall send an activation message to the BBIFF-U present in the UPF over the LI_T3 interface with the associated QFI value. The exact point at which the trigger is sent is left to the implementation (preferably, when the SMF receives the N4: PFCP Session Establishment/Modification Response from the UPF, see clauses 6.3.2 and 6.3.3 of TS 29.244), however, the BBIFF-C can send the trigger only when the following conditions are met:

• ActivateTask with target identity "HR" and "IMSSignaling" is received with X3 being included in the delivery type.
• The MCC + MNC of the Operator Identifier field of the DNN is different from the MCC+MNC configured in the SMF - see clause 6.1.6.2.2 of TS 29.502 and clause 9.1.2 of TS 23.203.
• The Network Identifier field of DNN contains "IMS" (IMS services) - see GSMA IR.88 [67].
• The 5QI value associated with the QoS Flow is 5 - see GSMA NG.114 [68].

The first point is indicating that N9HR LI is enabled (see clause 7.10.3.3.1) with a need to capture and deliver the IMS signaling related user plane packets. The second point is telling that the UE is an inbound roamer with Home Routed based roaming. The third point is telling that the PDU session is established for IMS services. The fourth point is telling that the IMS signaling related QoS Flow is established. If the PDU session for IMS services is already established for an inbound roaming UE with Home-Routed based roaming when the above indicated ActivateTask is received, then the BBIFF-C shall send the trigger at the time Activation Task is received from the LIPF. The details of ActivateTask sent to the BBIFF-U are shown in Table 7.10.3.5-1.

When the BBIFF-C present in the SMF detects that the PDU session is released (e.g. when SMF receives the N4: PFCP Session Deletion Response from the UPF, see clause 6.3.4 of TS 29.244), it shall send a deactivation message to the BBIFF-U present in the UPF over the LI_T3 interface, if the task is still active in the BBIFF-U. The BBIFF-C shall also send the deactivation message to the BBIFF-U when a DeactivateTask is received from the LIPF for the XID if the task is still active in the BBIFF-U.

When the BBIFF-C present in the SGW-C detects that the default bearer used for IMS signaling is activated on the PDN connection for an inbound roaming UE with home-routed roaming, it shall send an activation message to the BBIFF-U present in the SGW-U over the LI_T3 interface. The exact point at which the trigger is sent is left to the implementation (preferably, when the SGW-C receives the Sx: Session Establishment/Modification Response from the SGW-U). However, the BBIFF-C can send the trigger only when the following conditions are met:

• ActivateTask with target identity "HR" and "IMSSignaling" is received with X3 being included in the delivery type.
• The MCC + MNC of the Operator Identifier field of the APN is different from the MCC+MNC configured in the SGW/SGW-C - see clause 6.1.6.2.2 of TS 29.502 and clause 9.1.2 of TS 23.203.
• The Network Identifier field of APN contains "IMS" (IMS services) - see GSMA IR.88 [67].
• The QCI value associated with the default bearer is 5 - see GSMA NG.114 [68].

The first point is indicating that S8HR LI is enabled (see clause 7.10.3.3.1) with a need to capture and deliver the IMS signaling related user plane packets. The second point is telling that the UE is an inbound roamer with Home Routed based roaming. The third point is telling that the PDN connection is established for IMS services. The fourth point is telling that the IMS signaling bearer is activated. If the default bearer (for IMS signaling bearer) on the PDN connection is already established for an inbound roaming UE with Home-Routed based roaming when the above indicated ActivateTask is received, then the BBIFF-C shall send the trigger at the time Activation Task is received from the LIPF. The details of ActivateTask sent to the BBIFF-U present in the SGW-U are shown in Table 7.10.3.5-2.

When the BBIFF-C present in the SGW-C detects that the PDN connection is released (e.g. when SGW-C receives the Sx: Session Release Response from the SGW-U), it shall send a deactivation message to the BBIFF-U present in the SGW-U over the LI_T3 interface, if the task is still active in the BBIFF-U. The BBIFF-C present in the SGW-C shall also send the deactivation message to the BBIFF-U present in the SGW-U when a DeactivateTask is received from the LIPF for the XID if the task is still active in the BBIFF-U.

The BBIFF-U in UPF and the BBIFF-U in SGW-U shall send the xCC over LI_X3_LITE_S for each of the packet matching the criteria specified in the Triggering message (i.e. Activate Task message) received over the LI_T3 from the BBIFF-C.

The BBIFF present in the SGW shall send the xCC over LI_X3_LITE_S for each of the packet from the default bearer with the QCI value of 5 (GSMA NG.114 [68]) with following other conditions:

• ActivateTask with target identity "HR" and "IMSSignaling" is received with delivery type "X3Only".
• The MCC + MNC of the Operator Identifier field of the APN is different from the MCC+MNC configured in the SGW - see clause 6.1.6.2.2 of TS 29.502 and clause 9.1.2 of TS 23.203.
• The Network Identifier field of APN contains "IMS" (IMS services) - see GSMA IR.88 [67].

The first point is indicating that S8HR LI is enabled (see clause 7.10.3.2.2) with a need to capture and deliver the IMS signaling related user plane packets. The second point is telling that the UE is an inbound roamer with Home Routed based roaming. The third point is telling that the PDN connection is established for IMS services. The BBIFF in SGW uses the QCI value of 5 (GSMA NG.114 [68]) to identify that the packets are from the IMS signaling bearer.

Each X3 PDU shall contain the contents of the user plane packet given using the GTP-U, IP or Ethernet payload format. The BBIFF-U/BBIFF shall set the payload format to indicate the appropriate payload type (5 for IPv4 Packet, 6 for IPv6 Packet, 12 for GTP-U Packet as described in ETSI TS 103 221-2 [8] clauses 5.4 and 5.4.13.