8.3.1 S-NG-RAN node Addition Preparation

38.4233GPPNG-RANRelease 17TSXn Application Protocol (XnAP)

Tools: ARFCN - Frequency Conversion for 5G NR/LTE/UMTS/GSM

8.3.1.1 General

The purpose of the S-NG-RAN node Addition Preparation procedure is to request the S-NG-RAN node to allocate resources for dual connectivity operation for a specific UE.

The procedure uses UE-associated signalling.

8.3.1.2 Successful Operation

Figure 8.3.1.2-1: S-NG-RAN node Addition Preparation, successful operation

The M-NG-RAN node initiates the procedure by sending the S-NODE ADDITION REQUEST message to the S-NG-RAN node.

When the M-NG-RAN node sends the S-NODE ADDITION REQUEST message, it shall start the timer TXn_DCprep.

The allocation of resources according to the values of the Allocation and Retention Priority IE included in the QoS Flow Level QoS Parameters IE for each QoS flow shall follow the principles specified for the PDU Session Resource Setup procedure in TS 38.413 [5].

The S-NG-RAN node shall choose the ciphering algorithm based on the information in the UE Security Capabilities IE and locally configured priority list of AS encryption algorithms and apply the key indicated in the S-NG-RAN node Security Key IE as specified in TS 33.501 [28].

If the TSC Traffic Characteristics IE is included for a QoS flow in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall behave the same as the NG-RAN node in the PDU Session Resource Setup procedure, specified in TS 38.413 [5].

If the Additional QoS Flow Information IE is included for a QoS flow in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall behave the same as the NG-RAN node in the PDU Session Resource Setup procedure, specified in TS 38.413 [5].

For each GBR QoS flow, if the Alternative QoS Parameters Sets IE is included in the GBR QoS Flow Information IE, the S-NG-RAN node shall, if supported, behave the same as the NG-RAN node in the PDU Session Resource Setup procedure specified in TS 38.413 [5].

For each PDU session, if the Network Instance IE is included in the PDU Session Resource Setup Info – SN terminated IE contained in the PDU Session Resources To Be Added List IE and the Common Network Instance IE is not present, the S-NG-RAN node shall, if supported, use it when selecting transport network resource as specified in TS 23.501 [7].

For each GBR QoS flow, if the Offered GBR QoS Flow Information IE is included in the QoS Flows To Be Setup List IE contained in the PDU Session Resource Setup Info – SN terminated IE, the S-NG-RAN node may request the M-NG-RAN node to configure the DRB to which that QoS flow is mapped with MCG resources.

For each PDU session, if the Non-GBR Resources Offered IE is included in the PDU Session Resource Setup Info – SN terminated IE contained in the PDU Session Resources To Be Added List IE and set to "true", the S-NG-RAN node may request the M-NG-RAN node to configure DRBs to which non-GBR QoS flows of the PDU session are mapped with MCG resources.

For each PDU session, if the Common Network Instance IE is included in the PDU Session Resource Setup Info – SN terminated IE contained in the PDU Session Resources To Be Added List IE, the S-NG-RAN node shall, if supported, use it when selecting transport network resource as specified in TS 23.501 [7].

Redundant transmission:

– For each PDU session, if the Redundant UL NG-U UP TNL Information at UPF IE is included in the PDU Session Resource Setup Info – SN terminated IE, the S-NG-RAN node shall, if supported, use it as the uplink termination point for the user plane data for this PDU session for the redundant transmission and it shall include the Redundant DL NG-U UP TNL Information at NG-RAN IE in the PDU Session Resource Setup Response Info – SN terminated IE as described in TS 23.501 [7].

– For each PDU session, if the Redundant Common Network Instance IE is included in the PDU Session Resource Setup Info – SN terminated IE the S-NG-RAN node shall, if supported, use it when selecting transport network resource for the redundant transmission as specified in TS 23.501 [7].

– For each PDU session for which the Redundant QoS Flow Indicator IE is include in QoS Flows To Be Setup List IE contained in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, store and use it as specified in TS 23.501 [7].

– For each PDU session, if the Redundant PDU Session Information IE is included in the PDU Session Resource Setup Info – SN terminated IE in the S-NODE ADDITION REQUEST message, the S-NODE-RAN node shall, if supported, store the received information in the UE context and setup the redundant user plane resources for the concerned PDU session, as specified in TS 23.501 [7].

– For each PDU session resource successfully setup for which the Redundant PDU Session Information IE is included in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, include the Used RSN Information IE in the PDU Session Resource Setup Response Info – SN terminated IE in the S-NODE ADDITION REQUEST ACKNOWLEDGE message. If the PDU Session Pair ID IE is included in the Redundant PDU Session Information IE, the S-NG-RAN node may store and use it to identify the paired PDU sessions.

If the S-NODE ADDITION REQUEST message contains the Selected PLMN IE, the S-NG-RAN node may use it for RRM purposes.

If the S-NODE ADDITION REQUEST message contains the Expected UE Behaviour IE, the S-NG-RAN node shall, if supported, store this information and may use it to optimize resource allocation.

If the S-NODE ADDITION REQUEST message contains the Mobility Restriction List IE, the S-NG-RAN node, if supported, shall store this information and use it to select an appropriate SCG.

If the S-NODE ADDITION REQUEST message contains the Index to RAT/Frequency Selection Priority IE, the S-NG-RAN node may use it for RRM purposes.

If the S-NG-RAN node is a gNB and the S-NODE ADDITION REQUEST message contains the PCell ID IE, the S-NG-RAN node shall search for the target NR cell among the NR neighbour cells of the PCell indicated, as specified in the TS 37.340 [8].

If the S-NODE ADDITION REQUEST message contains the S-NG-RAN node PDU Session Aggregate Maximum Bit Rate IE, the S-NG-RAN node may use it for RRM purposes.

If the S-NODE ADDITION REQUEST message contains the MR-DC Resource Coordination Information IE, the S-NG-RAN node should forward it to lower layers and it may use it for the purpose of resource coordination with the M-NG-RAN node, or to coordinate with sidelink resources used in the M-NG-RAN node. The S-NG-RAN node shall consider the value of the received UL Coordination Information IE valid until reception of a new update of the IE for the same UE. The S-NG-RAN node shall consider the value of the received DL Coordination Information IE valid until reception of a new update of the IE for the same UE. If the E-UTRA Coordination Assistance Information IE or the NR Coordination Assistance Information IE is contained in the MR-DC Resource Coordination Information IE, the S-NG-RAN node shall, if supported, use the information to determine further coordination of resource utilisation between the S-NG-RAN node and the M-NG-RAN node.

If the S-NODE ADDITION REQUEST message contains the NE-DC TDM Pattern IE, the S-NG-RAN node should forward it to lower layers and use it for the purpose of single uplink transmission. The S-NG-RAN node shall consider the value of the received NE-DC TDM Pattern IE valid until reception of a new update of the IE for the same UE.

If the S-NODE ADDITION REQUEST message contains the QoS Flow Mapping Indication IE, the S-NG-RAN node may take it into account that only the uplink or downlink QoS flow is mapped to the DRB.

For each bearer for which allocation of the PDCP entity is requested at the S-NG-RAN node:

– the M-NG-RAN node may propose to apply forwarding of downlink data by including the DL Forwarding IE within PDU Session Resource Setup Info – SN terminated IE of the S-NODE ADDITION REQUEST message. For each bearer that it has decided to admit, the S-NG-RAN node may include the DL Forwarding GTP Tunnel Endpoint IE within the PDU Session Resource Setup Response Info – SN terminated IE of the S-NODE ADDITION REQUEST ACKNOWLEDGE message to indicate that it accepts the proposed forwarding of downlink data for this bearer.

– the S-NG-RAN node may include for each bearer in the PDU Session Resource Setup Response Info – SN terminated IE the UL Forwarding GTP Tunnel Endpoint IE to indicates it request data forwarding of uplink packets to be performed for that bearer.

– the M-NG-RAN node shall include RLC Mode IE for each bearer offloaded from M-NG-RAN node to S-NG-RAN node in the DRBs to QoS Flow Mapping List IE within the PDU Session Resource Setup Info – SN terminated IE of the S-NODE ADDTION REQUEST message, and the RLC Mode IE indicates the mode that the M-NG-RAN used for the DRB when it was hosted at the M-NG-RAN node.

For each bearer for which the PDCP entity is at the M-NG-RAN node:

– the M-NG-RAN node shall include the RLC mode IE for each bearer in the DRBs To Be Setup List IE within the PDU Session Resource Setup Info – MN terminated IE of the S-NODE ADDTION REQUEST message to indicate the RLC mode has been configured at the M-NG-RAN node, so that the S-NG-RAN node shall configure the same RLC mode for this MN terminated split bearer.

The M-NG-RAN node may also propose to apply forwarding of UL data when offloading QoS flows for which in-order delivery is requested by including the UL Forwarding Proposal IE in the Data Forwarding and Offloading Info from source NG-RAN node IE within the PDU Session Resource Setup Info – SN terminated IE of the S-NODE ADDITION REQUEST message. The S-NG-RAN node may include the PDU Session Level UL Data Forwarding UP TNL Information IE in the Data Forwarding Info from target NG-RAN node IE within the PDU Session Resource Setup Response Info – SN terminated IE of the S-NODE ADDITION REQUEST ACKNOWLEDGE message to indicate that it accepts the proposed forwarding.

If the Masked IMEISV IE is contained in the S-NODE ADDITION REQUEST message the S-NG-RAN node shall, if supported, use it to determine the characteristics of the UE for subsequent handling.

If the UE Radio Capability ID IE is contained in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, store this information in the UE context and use it as defined in TS 23.501 [7] and TS 23.502 [13].

The S-NG-RAN node shall report to the M-NG-RAN node, in the S-NODE ADDITION REQUEST ACKNOWLEDGE message, the result for all the requested PDU session resources in the following way:

– A list of PDU session resources which are successfully established shall be included in the PDU Session Resources Admitted To Be Added List IE.

– A list of PDU session resources which failed to be established shall be included in the PDU Session Resources Not Admitted List IE.

Upon reception of the S-NODE ADDITION REQUEST ACKNOWLEDGE message the M-NG-RAN node shall stop the timer TXn_DCprep.

If the S-NODE ADDITION REQUEST ACKNOWLEDGE message contains the MR-DC Resource Coordination Information IE, the M-NG-RAN node may use it for the purpose of resource coordination with the S-NG-RAN node. The M-NG-RAN node shall consider the value of the received UL Coordination Information IE valid until reception of a new update of the IE for the same UE. The M-NG-RAN node shall consider the value of the received DL Coordination Information IE valid until reception of a new update of the IE for the same UE. If the E-UTRA Coordination Assistance Information IE or the NR Coordination Assistance Information IE is contained in the MR-DC Resource Coordination Information IE, the M-NG-RAN node shall, if supported, use the information to determine further coordination of resource utilisation between the M-NG-RAN node and the S-NG-RAN node.

The S-NG-RAN node may include for each bearer in the DRBs To Be Setup List IE in the S-NODE ADDITION REQUEST ACKNOWLEDGE message the PDCP SN Length IE to indicate the PDCP SN length for that DRB.

If the S-NG-RAN node UE XnAP ID IE is contained in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, store this information and use it as defined in TS 37.340 [8].

If the S-NODE ADDITION REQUEST message contains the PDCP SN Length IE, the S-NG-RAN node shall, if supported, store this information and use it for lower layer configuration of the concerned MN terminated bearer.

If the S-NODE ADDITION REQUEST message contains the SN Addition Trigger Indication IE, the S-NG-RAN node shall include the RRC config indication IE in the S-NODE ADDITION REQUEST ACKNOWLEDGE message to inform the M-NG-RAN node if the S-NG-RAN node applied full or delta configuration, as specified in TS 37.340 [8].

If the S-NODE ADDITION REQUEST message contains the S-NG-RAN node Maximum Integrity Protected Data Rate Uplink IE or the S-NG-RAN node Maximum Integrity Protected Data Rate Downlink IE, the S-NG-RAN node shall use the received information when enforcing the maximum integrity protected data rate for the UE.

If the Security Indication IE is included in the PDU Session Resource Setup Info – SN terminated IE of the S-NODE ADDITION REQUEST message, the behaviour of the S-NG-RAN node shall be the same as specified for the same IE in the PDU Session Resources To Be Setup List IE in the Handover Preparation procedure, for the concerned PDU session, and the S-NG-RAN node shall include the Security Result IE in the PDU Session Resource Setup Response Info – SN terminated IE.

If the Security Result IE is included in the PDU Session Resource Setup Info – SN terminated IE of the S-NODE ADDITION REQUEST message, the S-NG-RAN node may take the information into account when deciding whether to perform user plane integrity protection or ciphering for the DRBs that it establishes for the concerned PDU session, except if the Split Session Indicator IE is included in the PDU Session Resource Setup Info – SN terminated IE and set to "split", in which case it shall perform user plane integrity protection or ciphering according to the information in the Security Result IE. If the S-NG-RAN node is an ng-eNB, it shall reject all PDU sessions for which the Integrity Protection Indication IE is set to "required" as specified in TS 33.501 [28]. If either the S-NG-RAN node or the M-NG-RAN node is an ng-eNB, the S-NG-RAN node shall behave according to clause 6.10.4 of TS 33.501 [28] for PDU sessions for which the Integrity Protection Indication IE is set to "preferred".

The S-NG-RAN node may include the Location Information at S-NODE IE in the S-NODE ADDITION REQUEST ACKNOWLEDGE message, if respective information is available at the S-NG-RAN node.

If the Location Information at S-NODE Reporting IE set to "pscell" is included in the S-NODE ADDITION REQUEST, the S-NG-RAN node shall, start providing information about the current location of the UE. If the Location Information at S-NODE IE is included in the S-NODE ADDITION REQUEST ACKNOWLEDGE, the M-NG-RAN node shall store the included information so that it may be transferred towards the AMF.

If the Default DRB Allowed IE is included in the PDU Session Resource Setup Info – SN terminated IE of the S-NODE ADDITION REQUEST message and set to "true", the S-NG-RAN node may configure the default DRB for the PDU session.

If the S-NODE ADDITION REQUEST ACKNOWLEDGE message includes the DRB IDs taken into use IE, the M-NG-RAN node, if applicable, shall act as specified in TS 37.340 [8].

If Trace Activation IE has previously been received for this UE, it shall be included in the S-NODE ADDITION REQUEST message. If the Trace Activation IE is included in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, initiate the requested trace function as described in TS 32.422 [23].

If the Trace Activation IE is included in the S-NODE ADDITION REQUEST message which includes

– the MDT Activation IE set to "Immediate MDT and Trace", then the S-NG-RAN node shall if supported, initiate the requested trace session and MDT session as described in TS 32.422 [23].

– the MDT Activation IE set to "Immediate MDT Only", the S-NG-RAN node shall, if supported, initiate the requested MDT session as described in TS 32.422 [23] and the S-NG-RAN node shall ignore the Interfaces To Trace IE, and the Trace Depth IE.

– the MDT Location Information IE, within the MDT Configuration IE, the S-NG-RAN node shall, if supported, store this information and take it into account in the requested MDT session.

– the MDT Activation IE set to "Immediate MDT Only", and if the Signalling based MDT PLMN List IE is included in the MDT Configuration IE, the S-NG-RAN node may use it to propagate the MDT Configuration as described in TS 37.320 [43].

– the Bluetooth Measurement Configuration IE, within the MDT Configuration IE, the S-NG-RAN node shall, if supported, take it into account for MDT Configuration as described in TS 37.320 [43].

– the WLAN Measurement Configuration IE, within the MDT Configuration IE, the S-NG-RAN node shall, if supported, take it into account for MDT Configuration as described in TS 37.320 [43].

– the Sensor Measurement Configuration IE, within the MDT Configuration IE, the S-NG-RAN node shall take it into account for MDT Configuration as described in TS 37.320 [43].

– the MDT Configuration IE and if the S-NG-RAN node is a gNB at least the MDT Configuration-NR IE shall be present, while if the S-NG-RAN Node is an ng-eNB at least the MDT Configuration-EUTRA IE shall be present.

If the Requested Fast MCG recovery via SRB3 IE set to "true" is included in the S-NODE ADDITION REQUEST message and the S-NG-RAN node decides to configure fast MCG link recovery via SRB3 as specified in TS 37.340 [8], the S-NG-RAN node shall, if supported, include the Available fast MCG recovery via SRB3 IE set to "true" in the S-NODE ADDITION REQUEST ACKNOWLEDGE message.

If the QoS Monitoring Request IE is included in the QoS Flow Level QoS Parameters IE for a QoS flow contained in the DRBs To Be Setup List IE of the PDU Session Resource Setup Info – MN terminated IE, the S-NG-RAN node shall, if supported, use it to configure lower layers for the purpose of delay measurement and QoS monitoring as specified in TS 23.501 [7]. If the QoS Monitoring Reporting Frequency IE is included in the QoS Flow Level QoS Parameters IE for a QoS flow contained in the DRBs To Be Setup List IE of the PDU Session Resource Setup Info – MN terminated IE, the S-NG-RAN node shall, if supported, use it for RAN part delay reporting.

For each QoS flow which has been successfully established in the S-NG-RAN node, if the QoS Monitoring Request IE was included in the QoS Flow Level QoS Parameters IE contained in the PDU Session Resource Setup Info – SN terminated IE, the S-NG-RAN node shall store this information, and shall, if supported, perform delay measurement and QoS monitoring as specified in TS 23.501 [7]. If the QoS Monitoring Reporting Frequency IE was included in the QoS Flow Level QoS Parameters IE contained in the PDU Session Resource Setup Info – SN terminated IE, the S-NG-RAN node shall store this information, and shall, if supported, use it for RAN part delay reporting. In case such a QoS flow is included in the DRBs To Be Setup List IE of the PDU Session Resource Setup Response Info – SN terminated IE, the M-NG-RAN node shall, if supported, use it to configure lower layers for the purpose of delay measurement and QoS monitoring. If the QoS Monitoring Reporting Frequency IE is included in the DRBs To Be Setup List IE of the PDU Session Resource Setup Response Info – SN terminated IE, the M-NG-RAN node shall, if supported, use it for RAN part delay reporting.

For each DRB configured as MN-terminated split bearer/SCG bearer, if the QoS Mapping Information IE is included in the DRBs Admitted List IE in the PDU Session Resource Setup Response Info – MN terminated IE of the S-NODE ADDITION REQUEST ACKNOWLEDGE message, the M-NG-RAN node shall, if supported, use it to set DSCP and/or IPv6 flow label fields for the downlink IP packets which are transmitted from M-NG-RAN node to S-NG-RAN node through the GTP tunnels indicated by the UP Transport Layer Information IE.

If the Source NG-RAN Node ID IE is included in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, use it to decide the direct data path availability with the indicated source NG-RAN node, and if the direct data forwarding path is available, include the Direct Forwarding Path Availability IE in the S-NODE ADDITION REQUEST ACKNOWLEDGE message.

If for a given QoS Flow the Source DL Forwarding IP Address IE or both, the Source DL Forwarding IP Address IE and the Source Node DL Forwarding IP Address IE are included within the Data Forwarding and Offloading Info from source NG-RAN node IE in the PDU Session Resource Setup Info – SN terminated IE contained in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, store this information and use it as part of its ACL functionality configuration actions, if such ACL functionality is deployed.

If for a given QoS Flow the Source DL Forwarding IP Address IE is included within the QoS Flows Mapped To DRB List IE in the PDU Session Resource Setup Response Info – SN terminated IE contained in the S-NODE ADDITION REQUEST ACKNOWLEDGE message, the M-NG-RAN node shall, if supported, store this information and use it as part of its ACL functionality to identify source TNL address for data forwarding in case of subsequent handover preparation, if such ACL functionality is deployed.

If the Management Based MDT PLMN List IE is contained in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, store the received information in the UE context, and use this information to allow subsequent selection of the UE for management based MDT defined in TS 32.422 [23].

Upon reception of the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, start collecting SCG information and continue for as long as the UE stays in one of its cells.

If the UE History Information from the UE IE is included in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, store this information.

If the PSCell Change History IE set to "reporting full history" is included in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, signal the latest SCG UE History Information upon each PSCell change, to the M-NG-RAN node, using the S-NG-RAN node initiated S-NG-RAN node Modification procedure.

If the IAB Node Indication IE is contained in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, consider that dual connectivity operation is requested for an IAB-node. In addition:

– If the No PDU Session Indication IE is contained in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, consider the UE as an IAB-node which does not have any PDU sessions activated, and ignore the PDU Session Resources To Be Added List IE, and shall not take any action with respect to PDU session setup. Subsequently, the M-NG-RAN node shall, if supported, ignore the PDU Session Resources Admitted To Be Added List IE in the S-NODE ADDITION REQUEST ACKNOWLEDGE message.

– If the F1-terminating IAB-donor Indicator IE is contained in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, assume that it will become the F1-terminating IAB-donor of the IAB-node, and act as described in TS 38.401 [2].

If the CHO Information SN Addition IE is included in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall consider that the S-NG-RAN node Addition Preparation procedure has been triggered as part of a conditional handover. It may use the Source M-NG-RAN node ID IE and the Source M-NG-RAN node UE XnAP ID IE to identify other active S-NG-RAN node Addition Preparations related to this UE. If the Estimated Arrival Probability IE is contained in the CHO Information SN Addition IE included in the S-NODE ADDITION REQUEST message, then the S-NG-RAN node may use the information to allocate necessary resources for the UE.

If the SCG Activation Request IE is included in the S-NODE ADDITION REQUEST message, the S-NG-RAN node may use it to configure SCG resources as specified in TS 37.340 [8], and shall, if supported, include the SCG Activation Status IE in the S-NODE ADDITION REQUEST ACKNOWLEDGE message. If the SCG Activation Request IE in the S-NODE ADDITION REQUEST message is set to "Activate SCG", the S-NG-RAN node shall, if supported, activate the SCG resources and set the SCG Activation Status IE in the S-NODE ADDITION REQUEST ACKNOWLEDGE message to "SCG activated".

If the Conditional PSCell Addition Information Request IE is included in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, consider that the request concerns CPAC, as described in TS 37.340 [8]. Accordingly, the S-NG-RAN node shall, if supported, include the Conditional PSCell Addition Acknowledge IE in the S-NODE ADDITION REQUEST ACKNOWLEDGE message.

If the Conditional PSCell Addition Information Acknowledge is included in the S-NODE ADDITION REQUEST ACKNOWLEDGE message, the M-NG-RAN node shall, if supported, shall, if supported, consider the indicated PSCells are selected by the target SN as candidate PSCells for CPAC.

If the CG-CandidateList is included in the S-NG-RAN node to M-NG-RAN node Container IE in the S-NODE ADDITION REQUEST ACKNOWLEDGE message, the M-NG-RAN node shall, if supported, use it for the purpose of CPAC.

If the Estimated Arrival Probability IE is contained in the Conditional PSCell Addition Information Request IE included in the S-NODE ADDITION REQUEST message, then the candidate target S-NG-RAN node may use the information to allocate necessary resources for the incoming CPAC procedure.

If the S-NG-RAN node UE Slice Maximum Bit Rate IE for a specific S-NSSAI is included in the S-NODE ADDITION REQUEST message, the S-NG-RAN node shall, if supported, store and use the received S-NG-RAN node UE Slice Maximum Bit Rate for all PDU sessions associated with the S-NSSAI for the concerned UE as defined in TS 23.501 [7].

Interactions with the S-NG-RAN node Reconfiguration Completion procedure:

If the S-NG-RAN node admits at least one PDU session resource, the S-NG-RAN node shall start the timer TXn_DCoverall when sending the S-NODE ADDITION REQUEST ACKNOWLEDGE message to the M-NG-RAN node except for a request for conditional configuration. The reception of the S-NODE RECONFIGURATION COMPLETE message shall stop the timer TXn_DCoverall if TXn_DCoverall is running.

Interaction with the Activity Notification procedure

Upon receiving an S-NODE ADDITION REQUEST message containing the Desired Activity Notification Level IE, the S-NG-RAN node shall, if supported, use this information to decide whether to trigger subsequent Activation Notification procedures according to the requested notification level.

8.3.1.3 Unsuccessful Operation

Figure 8.3.1.3-1: S-NG-RAN node Addition Preparation, unsuccessful operation

If the S-NG-RAN node is not able to accept any of the bearers or a failure occurs during the S-NG-RAN node Addition Preparation, the S-NG-RAN node sends the S-NODE ADDITION REQUEST REJECT message with an appropriate cause value to the M-NG-RAN node.

8.3.1.4 Abnormal Conditions

If the S-NG-RAN node receives an S-NODE ADDITION REQUEST message containing in a PDU Session Resource To Be Added Item IE neither the PDU Session Resource Setup Info – SN terminated IE nor the PDU Session Resource Setup Info – MN terminated IE, the S-NG-RAN node shall fail the S-NG-RAN node Addition Preparation procedure indicating an appropriate cause.

If the supported algorithms for encryption defined in the NR Encryption Algorithms IE in the NR UE Security Capabilities IE, plus the mandated support of NEA0 in all UEs (TS 33.501 [28]), do not match any algorithms defined in the configured list of allowed encryption algorithms in the S-NG-RAN node (TS 33.501 [28]), the S-NG-RAN node shall reject the procedure using the S-NODE ADDITION REQUEST REJECT message.

If the supported algorithms for integrity defined in the NR Integrity Protection Algorithms IE in the NR UE Security Capabilities IE do not match any algorithms defined in the configured list of allowed integrity protection algorithms in the S-NG-RAN node (TS 33.501 [28]), the S-NG-RAN node shall reject the procedure using the S-NODE ADDITION REQUEST REJECT message.

If the S-NG-RAN node receives an S-NODE ADDITION REQUEST message containing a S-NG-RAN node UE XnAP ID IE that does not match any existing UE Context that has such ID, the S-NG-RAN node shall reject the procedure using the S-NODE ADDITION REQUEST REJECT message.

If the M-NG-RAN node receives an S-NODE ADDITION REQUEST ACKNOWLEGE message containing a value for PDU Session ID in PDU Session Resources Admitted List IE and in PDU Session Resources Not Admitted List IE, the M-NG-RAN node shall regard setup of S-NG-RAN node resources of that PDU Session as being failed.

If the S-NG-RAN node receives an S-NODE ADDITION REQUEST message containing, for a PDU session, a PDU Session Resource Setup Info – SN terminated IE for which the Split Session Indicator IE is included and set to "split", the Security Result IE is not included, and either the Integrity Protection Indication IE or the Confidentiality Protection Indication IE is set to "preferred", it shall reject the PDU session.

Interaction with the M-NG-RAN node initiated S-NG-RAN node Release procedure:

If the M-NG-RAN node receives an S-NODE ADDITION REQUEST ACKNOWLEDGE message containing in a PDU Session Resource Admitted To Be Added Item IE neither the PDU Session Resource Setup Response Info – SN terminated IE nor the PDU Session Resource Setup Response Info – MN terminated IE, the M-NG-RAN node shall trigger the M-NG-RAN node initiated S-NG-RAN node Release procedure indicating an appropriate cause.

If the timer TXn_DCprep expires before the M-NG-RAN node has received the S-NODE ADDITION REQUEST ACKNOWLEDGE message, the M-NG-RAN node shall regard the S-NG-RAN node Addition Preparation procedure as being failed and shall trigger the M-NG-RAN node initiated S-NG-RAN node Release procedure.

Interactions with the S-NG-RAN node Reconfiguration Completion and S-NG-RAN node initiated S-NG-RAN node Release procedure:

If the timer TXn_DCoverall expires before the S-NG-RAN node has received the S-NODE RECONFIGURATION COMPLETE or the S-NODE RELEASE REQUEST message, the S-NG-RAN node shall regard the requested RRC connection reconfiguration as being not applied by the UE and shall trigger the S-NG-RAN node initiated S-NG-RAN node Release procedure.