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Content for  TS 33.128  Word version:  18.7.0

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7.10  LI in VPLMN for IMS-based services with home-routed roamingp. 284

7.10.1  Backgroundp. 284

This clause defines protocol and procedures to support the LI in the VPLMN for IMS-based services with home-routed roaming architecture where IMS signaling (e.g. CSCFs) and media functions (e.g. IMS-AGW) are in the HPLMN. The scope of LI functions defined here are the following in the VPLMN:
  • IMS-based voice services.
  • SMS over IP.
For IMS-based voice services and the SMS over IP, the target can be an inbound roaming UE or a non-local ID.
As defined in clause 7.4.7.4.2 of TS 33.127, LMISF-IRI, LMISF-CC, BBIFF-C and BBIFF-U handle the LI in the VPLMN for IMS-based services with home routed roaming architecture.
This clause uses the term "HR LI" in referring to the common functions associated with the N9HR LI and S8HR LI collectively.
The HR LI includes two phases of LI processing with the following scope:
  • Phase 1 - Initial configuration and target checking, applies to all in-bound roaming UEs with home-routed roaming and using IMS-based services. No interception is done in this phase.
  • Phase 2 - Applies to specific target UEs or UEs in communication with a target non-local ID. Interception is done in this phase.
The details of the above two phases of LI processes are described in clause 7.4.7.4.11 of TS 33.127.
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7.10.2  Backward compatibilityp. 285

The present document provides two options for stage 3 definitions for implementing S8HR LI:
  • Use LI_X1, LI_X2 and LI_X3 interfaces specified below in the present document.
  • Use TS 33.107 natively as defined in that document.
In both cases, the present document specifies the stage 3 for the LI_HI1 and LI_HI2 interfaces. Only the first option indicated above is used for N9HR LI.

7.10.3  HR LI Phase 1p. 285

7.10.3.1  Overviewp. 285

The Phase-1 of HR LI that applies to all inbound roaming UEs with home-routed roaming using the IMS-based services include the functions that revolve around the following interfaces (see TS 33.127):
  • LI_X1: Used by the LIPF to provision the BBIFF-C/BBIFF and optionally, the LMISF-IRI to enable the same for HR LI (aka initial configuration of HR LI).
  • LI_T3: Used by the BBIFF-C to instruct the BBIFF-U to capture and deliver the IMS signaling related user plane packets of inbound roaming UEs to the LMISF-IRI.
  • LI_X2_LITE: Used by the BBIFF-C/BBIFF to carry the control plane information (e.g. packet data connection related notifications, UE location) to LMISF-IRI for inbound roaming UEs.
  • LI_X3_LITE_S: Used by the BBIFF-U/BBIFF to forward the IMS signalling related user plane packets of inbound roaming UEs to the LMISF-IRI.
The triggering interface LI_T3 is not used in the case of BBIFF in SGW. The LI_X3_LITE_S is also used in HR LI Phase-2.
The LI_X2_LITE shall be realized using the X2 protocol as defined in ETSI TS 103 221-2 [8]. Likewise, the LI_X3_LITE_S and LI_X3_LITE_M shall be realized using the X3 protocol as defined in ETSI TS 103 221-2 [8].
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7.10.3.2  Provisioning over LI_X1p. 286

7.10.3.2.1  Generalp. 286
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.
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7.10.3.2.2  Provisioning of BBIFF-C and BBIFFp. 286
The minimum details of LI_X1 ActivationTask message is shown in Table 7.10.3.2-2.
ETSI TS 103 221-1 [7] field name Description M/C/O
XID Shall be set to a value assigned by the LIPF. This shall be same as the XID used for ActivateTask as shown in Table 7.10.3.2-4 when LMISF-IRI is configured using the ActivateTask.M
TargetIdentifiers Shall contain Target Identifiers of type "HR" and "IMSSignaling" (see Table 7.10.3.2-3). M
DeliveryType Set to "X2andX3". M
ListOfDIDs Shall give the DID of the LMISF-IRI to which the xIRI and xCC should be delivered. The delivery endpoint is configured using the CreateDestination message as described in ETSI TS 103 221-1 [7] clause 6.3.1 prior to the task activation.M
Identifier type ETSI TS 103 221-1 [7] TargetIdentifier type Definition
HRTargetIdentifierExtension /HREmpty tag (see XSD schema)
IMSSignalingTargetIdentifierExtension/IMSSignalingEmpty tag (see XSD schema)
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7.10.3.2.3  Provisioning of LMISF-IRIp. 286
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.
ETSI TS 103 221-1 [7] field name Description M/C/O
XID Shall be set to a value assigned by the LIPF. This shall be same as the XID used for ActivateTask as shown in Table 7.10.3.2-2.M
TargetIdentifiers Shall contain two Target Identifiers of type "HR" and "IMSSignaling" (see Table 7.10.3.2-3). M
DeliveryType Set to "X2andX3".
LMISF-IRI shall use this only to enable the receiving of xIRI and xCC from the BBIFF-C/BBIFF.
M
ListOfDIDsShall be given as an empty list, since DIDs are not required in LMISF-IRI for Phase-1.M
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7.10.3.3  Generation of xIRI over LI_X2_LITEp. 287

7.10.3.3.1  Generalp. 287
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.
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7.10.3.3.2  N9HR LIp. 287
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.
Field Name Description M/C/O
sUPISUPI associated with the PDU session (e.g. as provided by the AMF in the associated Nsmf_PDU Session_CreateSMContext service operation).M
pEIPEI associated with the PDU session, if available.C
pDUSessionIDPDU Session ID. See clause 9.4 of TS 24.501.M
locationUE location information provided by the AMF.C
sNSSAISlice identifiers associated with the PDU session, if available. See clause 28.4.2 of TS 23.003 and clause 5.12.2.2 of TS 23.501.C
dNNData Network Name associated with the UE traffic, as defined in clause 9A of TS 23.003 and described in clause 4.3.2.2 of TS 23.501. Shall be given in dotted-label presentation format as described in clause 9.1 of TS 23.003.C
messageCause Included to indicate why the xIRI is generated (see Table 7.10.3.3-2).M
Field Name Description
pDUSessionEstablishedIndicates that the PDU session is established.
pDUSessionModifiedIndicates that the PDU session is being modified.
pDUReleasedIndicates that the PDU session is being released.
updatedLocationAvailableIndicates that an updated UE location is available
sMFChangedIndicates that the SMF that is handling the PDU session is changed.
otherIndicates that cause is other than those listed elsewhere in this table.
hRLIEnabledIndicates that the HR LI is enabled after the PDU session for IMS services is established.
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.
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7.10.3.3.3  S8HR LIp. 289
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.
Field Name Description M/C/O
iMSIIMSI associated with the PDN connection on which a bearer is created.M
iMEIIMEI associated with the PDN connection on which a bearer is created, if available.C
bearerIDThe identity of the EPS bearer.M
linkedBearerIDThe identity of the default bearer when the bearerID is for dedicated bearer.C
locationLocation information provided by the MME.C
aPNPacket Data Network to which the connection is being made, as defined in clause 9A of TS 23.003 and described in clause 4.3.2.2 of TS 23.401. Applicable for PDN connection establishment. Shall be given in dotted-label presentation format as described in clause 9.1 of TS 23.003.C
sGWIPAddressIP Address of the SGW-C or SGW as applicable and when available.C
messageCause Included to indicate why the xIRI is generated (see Table 7.10.3.3-4).M
Field Name Description
bearerActivatedIndicates that the bearer is activated (default or dedicated).
bearerModifiedIndicates that the bearer is being modified.
bearerDeletedIndicates that the bearer is being deactivated.
pDNDisconnectedIndicates that the PDN is disconnected.
updatedLocationAvailableIndicates that an updated UE location is available.
sGWChangedIndicates that the SGW that is handling the PDN connection is changed.
otherIndicates that cause is other than those listed elsewhere in this table.
hRLIEnabledIndicates that the HR LI is enabled after the PDN connection with default bearer for IMS services is established.
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.
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7.10.3.4  LMISF-IRI handling of xIRIs received over LI_X2_LITEp. 290

7.10.3.4.1  Handling of xIRIsp. 290
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.
7.10.3.4.2  Handling of the stored recordp. 290
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.

7.10.3.5  Triggering of BBIFF-U from BBIFF-C over LI_T3p. 291

7.10.3.5.1  Generalp. 291
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.
7.10.3.5.2  N9HR LIp. 291
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.
ETSI TS 103 221-1 [7] field name Description M/C/O
XIDShall be set to the XID of the Task Object associated with the interception at the BBIFF-C.M
TargetIdentifiers Packet detection criteria as determined by the BBIFF-C in the SMF, which enables the BBIFF-U to isolate user-plane packets. The BBIFF-U in the UPF shall support the identifier types given in Table 6.2.3-7. The target identity type of PDR ID shall be mandatory. The BBIFF-C in SMF shall use the QFI associated with the IMS signaling (5QI = 5) related QoS flow to populate the QFI field within the PDI of PDR ID.M
DeliveryType Set to "X3Only". M
ListOfDIDs Shall give the DID of the LMISF-IRI to which the xCC should be delivered. The delivery endpoint is configured using the CreateDestination message as described in ETSI TS 103 221-1 [7] clause 6.3.1 prior to the task activation.M
CorrelationIDCorrelation ID to assign to X3 PDUs generated by the BBIFF-U in the UPF. This field is populated with the same CorrelationID the BBIFF-C in the SMF uses for the associated xIRI.M
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.
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7.10.3.5.3  S8HR LIp. 292
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.
ETSI TS 103 221-1 [7] field name Description M/C/O
XIDShall be set to the XID of the Task Object associated with the interception at the BBIFF-C.M
TargetIdentifiers Packet detection criteria as determined by the BBIFF-C in the SGW-C, which enables the BBIFF-U in SGW-U to isolate user-plane packets. The BBIFF-U in the SGW-U shall support the identifier types given in Table 6.2.3-7. The target identity type of PDR ID shall be mandatory. The BBIFF-C in SGW-C shall use the F-TIEDs associated with the IMS signaling (QCI = 5) related default bearer to populate the F-TEID field within the PDI of PDR ID.M
DeliveryType Set to "X3Only". M
ListOfDIDs Shall give the DID of the LMISF-IRI to which the xCC should be delivered. The delivery endpoint is configured using the CreateDestination message as described in ETSI TS 103 221-1 [7] clause 6.3.1 prior to the task activation.M
CorrelationIDCorrelation ID to assign to X3 PDUs generated by the BBIFF-U in the SGW-U. This field is populated with the same CorrelationID the BBIFF-C in the SGW-C uses for the associated xIRI.M
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.
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7.10.3.6  Generation of xCC over LI_X3_LITE_Sp. 293

7.10.3.6.1  BBIFF-Up. 293
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.
7.10.3.6.2  BBIFFp. 293
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.
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7.10.3.6.3  X3 PDU formatp. 293
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.

7.10.3.7  LMISF-IRI handling of xCC received over LI_X3_LITE_Sp. 294

The LMISF-IRI shall extract the IMS signaling messages (i.e. SIP messages) from the xCC received over the LI_X3_LITE_S from the BBIFF-U/BBIFF.
The LMISF-IRI shall examine the extracted SIP message for a target match as described in clause 7.10.4.2. If no match is found, then the LMISF-IRI shall store the extracted SIP message for a later use. If a match is found, then the LMISF-IRI shall proceed according to clause 7.10.4.3.
The record that stores the SIP message is referred to as LI_X2_LITE_S record.
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