Section: 6.1.4.1 Coordination between 5GSM and ESM with N26 interface
Content: Interworking with EPS is supported for a PDU session, if the PDU session includes the mapped EPS bearer context(s) or has association(s) between QoS flow and mapped EPS bearer after inter-system change from S1 mode to N1 mode. The SMF shall not include any mapped EPS bearer contexts associated with a PDU session for LADN and with a PDU session which is a multi-homed IPv6 PDU session. If the UE receives any mapped EPS bearer context for a PDU session for LADN or for a multi-homed IPv6 PDU session, the UE may locally delete the mapped EPS bearer context. See coding of the Mapped EPS bearer contexts IE in subclause 9.11.4.8. In an MA PDU session, the UE shall have one set of the mapped EPS bearer contexts. The network can provide the set of the mapped EPS bearer contexts of the MA PDU session via either access of the MA PDU session. In an MA PDU session, the UE shall support modification or deletion via an access of a mapped EPS bearer context of the MA PDU session created via the same or the other access. Upon inter-system change from N1 mode to S1 mode, the UE shall create the default EPS bearer context and the dedicated EPS bearer context(s) based on the parameters of the mapped EPS bearer contexts or the associations between QoS flow and mapped EPS bearer in the PDU session, if available. The EPS bearer identity assigned for the QoS flow of the default QoS rule becomes the EPS bearer identity of the default bearer in the corresponding PDN connection. If there is no EPS bearer identity assigned to the QoS flow of the default QoS rule of a PDU session associated with 3GPP access, or if there is no corresponding mapped EPS bearer contexts associated with the EPS bearer identity assigned to the QoS flow of the default QoS rule of a PDU session associated with 3GPP access: a) the PDU session is not an MA PDU session established over both 3GPP access and non-3GPP access, the UE shall perform a local release of the PDU session; or b) the PDU session is an MA PDU session established over both 3GPP access and non-3GPP access, the UE shall perform a local release of the PDU session over 3GPP access and consider that the MA PDU session is established over non-3GPP access only. If there is no EPS bearer identity assigned to the QoS flow(s) of a PDU session associated with 3GPP access which is not associated with the default QoS rule, or if there is no corresponding mapped EPS bearer contexts associated with the EPS bearer identity assigned to the QoS flow of the non-default QoS rule of a PDU session associated with 3GPP access, unless the PDU session is an MA PDU session established over 3GPP access and over non-3GPP access, the UE shall locally delete the QoS rules and the QoS flow description(s). The UE uses the parameters from each PDU session for which interworking with EPS is supported to create corresponding default EPS bearer context and optionally dedicated EPS bearer context(s) as follows: a) the PDU session type of the PDU session shall be mapped to the PDN type of the default EPS bearer context as follows: 1) the PDN type shall be set to "non-IP" if the PDU session type is "Unstructured"; 2) the PDN type shall be set to "IPv4" if the PDU session type is "IPv4"; 3) the PDN type shall be set to "IPv6" if the PDU session type is "IPv6"; 4) the PDN type shall be set to "IPv4v6" if the PDU session type is "IPv4v6"; 5) the PDN type shall be set to "non-IP" if the PDU session type is "Ethernet", and the UE, the network or both of them do not support Ethernet PDN type in S1 mode; and 6) the PDN type shall be set to "Ethernet" if the PDU session type is "Ethernet" and the UE and the network support Ethernet PDN type in S1 mode; b) the PDU address of the PDU session shall be mapped to the PDN address of the default EPS bearer context as follows: 1) the PDN address of the default EPS bearer context is set to the PDU address of the PDU session, if the PDU session type is "IPv4", "IPv6" or "IPv4v6"; and 2) the PDN address of the default EPS bearer context is set to zero, if the PDU session type is "Ethernet" or "Unstructured"; c) the DNN of the PDU session shall be mapped to the APN of the default EPS bearer context, unless the PDU session is an emergency PDU session; d) the APN-AMBR and extended APN-AMBR received in the parameters of the default EPS bearer context of the mapped EPS bearer contexts shall be mapped to the APN-AMBR and extended APN-AMBR of the default EPS bearer context; e) for each PDU session in state PDU SESSION ACTIVE, PDU SESSION MODIFICATION PENDING or PDU SESSION INACTIVE PENDING: 1) if the UE is performing an inter-system change from N1 mode to WB-S1 mode, the UE shall set the state of the mapped EPS bearer context(s) to BEARER CONTEXT ACTIVE; or 2) if the UE is performing an inter-system change from N1 mode to NB-S1 mode, for the mapped EPS bearer context corresponding to the default EPS bearer, the UE shall set the state of the mapped EPS bearer context to BEARER CONTEXT ACTIVE. Additionally, if the UE is performing an inter-system change from WB-N1 mode to NB-S1 mode, for the mapped EPS bearer context corresponding to a dedicated EPS bearer, if any, the UE shall set the state of the mapped EPS bearer context to BEARER CONTEXT INACTIVE; and f) for any other PDU session the UE shall set the state of the mapped EPS bearer context(s) to BEARER CONTEXT INACTIVE. Additionally, for each mapped EPS bearer context or the association between QoS flow and mapped EPS bearer in the PDU session: a) the EPS bearer identity shall be set to the EPS bearer identity received in the mapped EPS bearer context, or the EPS bearer identity associated with the QoS flow; b) the EPS QoS parameters shall be set to the mapped EPS QoS parameters of the EPS bearer received in the mapped EPS bearer context, or the EPS QoS parameters associated with the QoS flow; c) the extended EPS QoS parameters shall be set to the mapped extended EPS QoS parameters of the EPS bearer received in the mapped EPS bearer context, or the extended EPS QoS parameters associated with the QoS flow; and d) the traffic flow template shall be set to the mapped traffic flow template of the EPS bearer received in the mapped EPS bearer context, or the stored traffic flow template associated with the QoS flow, if available. After inter-system change from N1 mode to S1 mode, the UE shall associate the PDU session identity, the S-NSSAI, and the session-AMBR with the default EPS bearer context, and for each EPS bearer context mapped from one or more QoS flows, associate the QoS rule(s) for the QoS flow(s) and the QoS flow description(s) for the QoS flow(s) with the EPS bearer context. If the PDU session is associated with the control plane only indication and supports interworking with EPS, after inter-system change from N1 mode to S1 mode, the UE shall associate the EPS bearer context(s) of the PDN connection corresponding to the PDU session with the control plane only indication. If the PDU session is associated with a PDU session pair ID, after inter-system change from N1 mode to S1 mode, the UE shall associate the default EPS bearer context of the PDN connection corresponding to the PDU session with the PDU session pair ID. If the PDU session is associated with an RSN, after inter-system change from N1 mode to S1 mode, the UE shall associate the default EPS bearer context of the PDN connection corresponding to the PDU session with the RSN. After inter-system change from N1 mode to S1 mode, the UE and the SMF shall maintain the PDU session type of the PDU session until the PDN connection corresponding to the PDU session is released if the UE supports non-IP PDN type and the PDU session type is "Ethernet" or "Unstructured". After inter-system change from N1 mode to S1 mode, the UE and the SMF shall maintain the following 5GSM attributions and capabilities associated with the PDU session until the PDN connection corresponding to the PDU session is released: a) the always-on PDU session indication; b) the maximum number of supported packet filters; c) the support of reflective QoS; d) the maximum data rate per UE for user-plane integrity protection supported by the UE for uplink and the maximum data rate per UE for user-plane integrity protection supported by the UE for downlink; e) the support of multi-homed IPv6 PDU session; and f) if the PDU session is an MA PDU session established over 3GPP access, the PDN connection of the default EPS bearer corresponding to the MA PDU session shall be considered as a user-plane resource of the MA PDU session. After inter-system change from N1 mode to S1 mode, the UE operating in single-registration mode in a network supporting N26 interface shall deem that the following features are supported by the network on the PDN connection corresponding to the PDU session: a) PS data off; and b) Local address in TFT. If there is a QoS flow used for IMS signalling, after inter-system change from N1 mode to S1 mode, the EPS bearer associated with the QoS flow for IMS signalling becomes the EPS bearer for IMS signalling. When the UE is provided with a new session-AMBR in the Protocol configuration options IE or Extended protocol configuration options IE in the MODIFY EPS BEARER CONTEXT REQUEST message, the UE shall discard the corresponding association and associate the new valuewith the default EPS bearer context. The network may provide the UE with one or more QoS rules by including either one QoS rules parameter, or one QoS rules with the length of two octets parameter, but not both, in the Protocol configuration options IE or Extended protocol configuration options IE in the MODIFY EPS BEARER CONTEXT REQUEST message. The network may provide the UE with one or more QoS flow descriptions corresponding to the EPS bearer context being modified, by including either one QoS flow descriptions parameter, or one QoS flow descriptions with the length of two octets parameter, but not both, in the Protocol configuration options IE or Extended protocol configuration options IE in the MODIFY EPS BEARER CONTEXT REQUEST message. When the UE is provided with one or more QoS flow descriptions or the EPS bearer identity of an existing QoS flow description is modified in the Protocol configuration options IE or Extended protocol configuration options IE in the MODIFY EPS BEARER CONTEXT REQUEST message, the UE shall check the EPS bearer identity included in the QoS flow description; and: a) if the EPS bearer identity corresponds to the EPS bearer context being modified or the EPS bearer identity is not included, the UE shall store the QoS flow description and all the associated QoS rules, if any, for the EPS bearer context being modified for use during inter-system change from S1 mode to N1 mode; and b) otherwise the UE shall locally delete the QoS flow description and all the associated QoS rules, if any, and include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #84 "syntactical error in the QoS operation" in the MODIFY EPS BEARER CONTEXT ACCEPT message. When the UE is provided with one or more QoS rules, or one or more QoS flow descriptions in the Protocol configuration options IE or Extended protocol configuration options IE in the MODIFY EPS BEARER CONTEXT REQUEST message, the UE shall process the QoS rules sequentially starting with the first QoS rule and shall process the QoS flow descriptions sequentially starting with the first QoS flow description. The UE shall check the QoS rules and QoS flow descriptions for different types of errors as follows: NOTE 1: If an error is detected in a QoS rule or a QoS flow description which requires sending a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause value, then the QoS rules parameter, the QoS rules with the length of two octets parameter, the QoS flow descriptions parameter and the QoS flow descriptions with the length of two octets parameter included in the Protocol configuration options IE or Extended protocol configuration options IE in the MODIFY EPS BEARER CONTEXT REQUEST message are discarded, if any. NOTE 2: If the EPS bearer context modification procedure is rejected, then the QoS rules parameter, the QoS rules with the length of two octets parameter, the QoS flow descriptions parameter and the QoS flow descriptions with the length of two octets parameter included in the Protocol configuration options IE or Extended protocol configuration options IE in the MODIFY EPS BEARER CONTEXT REQUEST message are discarded, if any. a) Semantic errors in QoS operations: 1) When the rule operation is "Modify existing QoS rule and add packet filters", "Modify existing QoS rule and replace all packet filters", "Modify existing QoS rule and delete packet filters" or "Modify existing QoS rule without modifying packet filters" on the default QoS rule and the DQR bit is set to "the QoS rule is not the default QoS rule". 2) When the rule operation is "Modify existing QoS rule and add packet filters", "Modify existing QoS rule and replace all packet filters", "Modify existing QoS rule and delete packet filters" or "Modify existing QoS rule without modifying packet filters" on a QoS rule which is not the default QoS rule and the DQR bit is set to "the QoS rule is the default QoS rule". 3) When the rule operation is "Create new QoS rule" and the DQR bit is set to "the QoS rule is the default QoS rule" when there's already a default QoS rule with different QoS rule identifier. 4) When the rule operation is "Delete existing QoS rule" on the default QoS rule. 5) When the rule operation is "Create new QoS rule", "Modify existing QoS rule and add packet filters", "Modify existing QoS rule and replace all packet filters", "Modify existing QoS rule and delete packet filters", or "Modify existing QoS rule without modifying packet filters" and two or more QoS rules associated with this PDU session would have identical precedence values. 6) When the rule operation is "Modify existing QoS rule and delete packet filters", the QoS rule is a QoS rule of a PDU session of IPv4, IPv6, IPv4v6 or Ethernet PDU session type, and the packet filter list in the resultant QoS rule is empty. 7) When the rule operation is "Create new QoS rule", and there is already an existing QoS rule with the same QoS rule identifier and the existing QoS rule is associated with a QoS flow description stored for the EPS bearer context being modified or the existing QoS rule is not associated with any QoS flow description. 8) When the rule operation is "Modify existing QoS rule and add packet filters", "Modify existing QoS rule and replace all packet filters", "Modify existing QoS rule and delete packet filters", or "Modify existing QoS rule without modifying packet filters" and there is no existing QoS rule with the same QoS rule identifier associated with a QoS flow description stored for the EPS bearer context being modified. 9) When the rule operation is "Delete existing QoS rule" and there is no existing QoS rule with the same QoS rule identifier associated with a QoS flow description stored for the EPS bearer context being modified. 10) When the flow description operation is "Create new QoS flow description" and there is already an existing QoS flow description with the same QoS flow identifier stored for the EPS bearer context being modified. 11) When the flow description operation is "Modify existing QoS flow description" and there is no existing QoS flow description with the same QoS flow identifier stored for the EPS bearer context being modified. 12) When the flow description operation is "Delete existing QoS flow description" and there is no existing QoS flow description with the same QoS flow identifier stored for the EPS bearer context being modified. 13) When the UE determines that: i) the default EPS bearer context is associated with one or more QoS flows but the default EPS bearer context is not associated with the default QoS rule. ii) a dedicated EPS bearer context is associated with one or more QoS flows but the dedicated EPS bearer context is associated with the default QoS rule. 14) When the rule operation is "Create new QoS rule" and there is already an existing QoS rule with the same QoS rule identifier associated with a QoS flow description stored for an EPS bearer context different from the EPS bearer context being modified and belonging to the same PDN connection as the EPS bearer context being modified. 15) When the flow description operation is "Create new QoS flow description", and there is already an existing QoS flow description with the same QoS flow identifier stored for an EPS bearer context different from the EPS bearer context being modified and belonging to the same PDN connection as the EPS bearer context being modified. 16) When the rule operation is "Create new QoS rule", "Modify existing QoS rule and add packet filters", "Modify existing QoS rule and replace all packet filters", "Modify existing QoS rule and delete packet filters", or "Modify existing QoS rule without modifying packet filters" and the resultant QoS rule is associated with a QoS flow description stored for an EPS bearer context different from the EPS bearer context being modified. 17) When the rule operation is "Create new QoS rule", the DQR bit is set to "the QoS rule is not the default QoS rule", the QoS rule is provided for a PDN connection of PDN type "non-IP" and there is locally available information associated with the PDN connection that is set to "Unstructured". 18) When the flow description operation is "Create new QoS flow description" or "Modify existing QoS flow description", the QFI associated with the QoS flow description is not the same as the QFI of the default QoS rule, the QoS flow description is provided for a PDN connection of PDN type "non-IP" and there is locally available information associated with the PDN connection that is set to "Unstructured". 19) When the rule operation is "Modify existing QoS rule and add packet filters", the "packet filter list" field contains a match-all packet filter, the resultant QoS rule is the default QoS rule and there is already an existing match-all packet filter associated with the default QoS rule. 20) When the rule operation is "Create new QoS rule" and the DQR bit is set to "the QoS rule is not the default QoS rule", or the rule operation is "Modify existing QoS rule and add packet filters" on a QoS rule which is not the default QoS rule or "Modify existing QoS rule and replace all packet filters" on a QoS rule which is not the default QoS rule, and one match-all packet filter is to be associated with the resultant QoS rule. In case 5, if the old QoS rule (i.e. the QoS rule that existed before the MODIFY EPS BEARER CONTEXT REQUEST message was received) is not the default QoS rule and the old QoS rule is associated with a QoS flow description stored for the EPS bearer context being modified, the UE shall not diagnose an error, shall further process the new request and, if it was processed successfully, shall delete the old QoS rule which has identical precedence value. Otherwise, the UE shall include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #83 "semantic error in the QoS operation" in the MODIFY EPS BEARER CONTEXT ACCEPT message. In case 6, if the QoS rule is not the default QoS rule, the UE shall delete the QoS rule. If the QoS rule is the default QoS rule, the UE shall include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #83 "semantic error in the QoS operation" in the MODIFY EPS BEARER CONTEXT ACCEPT message. In case 7, if the existing QoS rule is not the default QoS rule and the DQR bit of the new QoS rule is set to "the QoS rule is not the default QoS rule", the UE shall not diagnose an error, further process the create request and, if it was processed successfully, delete the old QoS rule (i.e. the QoS rule that existed when case 7 was detected). If the existing QoS rule is the default QoS rule or the DQR bit of the new QoS rule is set to "the QoS rule is the default QoS rule", the UE shall include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #83 "semantic error in the QoS operation" in the MODIFY EPS BEARER CONTEXT ACCEPT message. In case 9, the UE shall not diagnose an error, further process the delete request and, if it was processed successfully, consider the respective QoS rule as successfully deleted. In case 10, the UE shall not diagnose an error, further process the create request and, if it was processed successfully, delete the old QoS flow description (i.e. the QoS flow description that existed when case 10 was detected. In case 12, the UE shall not diagnose an error, further process the delete request and, if it was processed successfully, consider the respective QoS flow description as successfully deleted. Otherwise, the UE shall include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #83 "semantic error in the QoS operation" in the MODIFY EPS BEARER CONTEXT ACCEPT message. b) Syntactical errors in QoS operations: 1) When the rule operation is "Create new QoS rule", "Modify existing QoS rule and add packet filters", "Modify existing QoS rule and replace all packet filters" or "Modify existing QoS rule and delete packet filters", the packet filter list in the QoS rule is empty, and the QoS rule is provided for a PDN connection of PDN type IPv4, IPv6, IPv4v6 or Ethernet, or for a PDN connection of PDN type "non-IP" and there is locally available information associated with the PDN connection that is set to "Ethernet". 2) When the rule operation is "Delete existing QoS rule" or "Modify existing QoS rule without modifying packet filters" with a non-empty packet filter list in the QoS rule. 3) When the rule operation is "Modify existing QoS rule and delete packet filters" and the packet filter to be deleted does not exist in the original QoS rule. 4) Void. 5) When there are other types of syntactical errors in the coding of the QoS rules parameter, the QoS rules with the length of two octets parameter, the QoS flow descriptions parameter or the QoS flow descriptions with the length of two octets parameter, such as a mismatch between the number of packet filters subfield, and the number of packet filters in the packet filter list when the rule operation is "delete existing QoS rule" or "create new QoS rule", or the number of packet filters subfield is larger than the maximum possible number of packet filters in the packet filter list (i.e., there is no QoS rule precedence subfield included in the QoS rule IE), the QoS Rule Identifier is set to "no QoS rule identifier assigned" when the rule operation is not "delete existing QoS rule", or the QoS flow identifier is set to "no QoS flow identifier assigned" when the flow description operation is not "Delete existing QoS flow description". 6) When, the A) rule operation is "Create new QoS rule", "Modify existing QoS rule and add packet filters", "Modify existing QoS rule and replace all packet filters", "Modify existing QoS rule and delete packet filters" or "Modify existing QoS rule without modifying packet filters", the UE determines, by using the QoS rule’s QFI as the 5QI, that there is a resulting QoS rule for a GBR QoS flow (as described in 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [8] table 5.7.4-1), and there is no QoS flow description with a QFI corresponding to the QFI of the resulting QoS rule. B) flow description operation is "Delete existing QoS flow description", and the UE determines, by using the QoS rule’s QFI as the 5QI, that there is a resulting QoS rule for a GBR QoS flow (as described in 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [8] table 5.7.4-1) with a QFI corresponding to the QFI of the QoS flow description that is deleted (i.e. there is no associated QoS flow description with the same QFI). 7) When the flow description operation is "Create new QoS flow description" or "Modify existing QoS flow description", and the UE determines that there is a QoS flow description of a GBR QoS flow (as described in 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [8] table 5.7.4-1) which lacks at least one of the mandatory parameters (i.e., GFBR uplink, GFBR downlink, MFBR uplink and MFBR downlink). If the QoS flow description does not include a 5QI, the UE determines this by using the QFI as the 5QI. 8) When the rule operation is "Create new QoS rule", "Modify existing QoS rule and add packet filters" or "Modify existing QoS rule and replace all packet filters" with a non-empty packet filter list in the QoS rule, and the DQR bit is set to "the QoS rule is the default QoS rule", the QoS rule is provided for a PDN connection of PDN type "non-IP" and there is locally available information associated with the PDN connection that is set to "Unstructured". In case 3 the UE shall not diagnose an error, further process the deletion request and, if no error according to items c and d was detected, consider the respective packet filter as successfully deleted. Otherwise the UE shall include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #84 "syntactical error in the QoS operation" in the MODIFY EPS BEARER CONTEXT ACCEPT message. NOTE 3: It is not considered an error if the UE determines that after processing all QoS operations on QoS rules and QoS flow descriptions there is a QoS flow description that is not associated with any QoS rule and the UE is not in NB-N1 mode. NOTE 3a: An implementation that strictly follows QoS rule operation as defined in subclause 9.11.4.13 might not detect case 2). c) Semantic errors in packet filters: 1) When a packet filter consists of conflicting packet filter components which would render the packet filter ineffective, i.e. no IP packet will ever fit this packet filter. How the UE determines a semantic error in a packet filter is outside the scope of the present document. The UE shall include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #44 "semantic errors in packet filter(s)" in the MODIFY EPS BEARER CONTEXT ACCEPT message. d) Syntactical errors in packet filters: 1) When the rule operation is "Modify existing QoS rule and add packet filters" or "Modify existing QoS rule and replace all packet filters", and two or more packet filters in the resultant QoS rule would have identical packet filter identifiers. 2) When the rule operation is "Create new QoS rule", and two or more packet filters in the resultant QoS rule would have identical packet filter identifiers. 3) When there are other types of syntactical errors in the coding of packet filters, such as the use of a reserved value for a packet filter component identifier. 4) Void. In case 1, if two or more packet filters with identical packet filter identifiers are contained in the MODIFY EPS BEARER CONTEXT REQUEST message, the UE shall include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #45 "syntactical error in packet filter(s)" in the MODIFY EPS BEARER CONTEXT ACCEPT message. Otherwise, the UE shall not diagnose an error, further process the MODIFY EPS BEARER CONTEXT REQUEST message and, if it was processed successfully, delete the old packet filters which have the identical packet filter identifiers. Otherwise the UE shall include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #45 "syntactical error in packet filter(s)" in the MODIFY EPS BEARER CONTEXT ACCEPT message. If the UE detects different errors in the QoS rules and QoS flow descriptions as described in this subclause which requires sending a 5GSM cause parameter in the MODIFY EPS BEARER CONTEXT ACCEPT message, the UE shall include a single 5GSM cause parameter in the MODIFY EPS BEARER CONTEXT ACCEPT message. NOTE 4: The 5GSM cause to use cannot be different from #44 "semantic error in packet filter(s)", #45 "syntactical errors in packet filter(s)", #83 "semantic error in the QoS operation" or #84 "syntactical error in the QoS operation". The selection of a 5GSM cause is up to UE implementation. Upon successful completion of an EPS attach procedure or tracking area updating procedure after inter-system change from N1 mode to S1 mode (see 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [15]), unless the PDU session is an MA PDU session established over 3GPP access and over non-3GPP access both connected to 5GCN, a) the UE shall delete any UE derived QoS rules of each PDU session which has been transferred to EPS; b) the UE and the SMF shall perform a local release of the PDU session(s) associated with 3GPP access which have not been transferred to EPS; and c) the UE and the SMF shall perform a local release of QoS flow(s) which have not been transferred to EPS, of the PDU session(s) which have been transferred to EPS. The UE and the SMF shall also perform a local release of any QoS flow description not associated with any QoS rule and not associated with any mapped EPS bearer context. If there is a QoS flow description not associated with any QoS rule, but associated with a mapped EPS bearer context, and after the inter-system change from N1 mode to S1 mode the respective EPS bearer context is active, then the UE shall associate the QoS flow description with the EPS bearer context. For PDU session(s) associated with non-3GPP access in 5GS, if present, the UE may: a) keep some or all of these PDU sessions still associated with non-3GPP access in 5GS, if supported; b) release some or all of these PDU sessions explicitly by initiating the UE requested PDU session release procedure(s); or c) attempt to transfer some or all of these PDU sessions from N1 mode to S1 mode by initiating the UE requested PDN connectivity procedure(s) with the PDN CONNECTIVITY REQUEST message created as follows: 1) if the PDU session is an emergency PDU session, the request type shall be set to "handover of emergency bearer services". Otherwise the request type shall be set to "handover"; 2) the PDU session type of the PDU session shall be mapped to the PDN type of the default EPS bearer context as follows: i) the PDN type shall be set to "non-IP" if the PDU session type is "Unstructured"; ii) the PDN type shall be set to "IPv4" if the PDU session type is "IPv4"; iii) the PDN type shall be set to "IPv6" if the PDU session type is "IPv6"; iv) the PDN type shall be set to "IPv4v6" if the PDU session type is "IPv4v6"; v) the PDN type shall be set to "non-IP" if the PDU session type is "Ethernet" and the UE, the network or both of them do not support Ethernet PDN type in S1 mode; and vi) the PDN type shall be set to "Ethernet" if the PDU session type is "Ethernet" and the UE and the network support Ethernet PDN type in S1 mode; 3) the DNN of the PDU session shall be mapped to the APN of the default EPS bearer context, unless the PDN connection is an emergency PDN connection; and 4) the PDU session ID parameter in the Protocol configuration options IE or the Extended protocol configuration options IE shall be set to the PDU session identity of the PDU session. If a PDU session associated with non-3GPP access is transferred to EPS, the UE shall associate the PDU session identity with the default EPS bearer context and shall delete any UE derived QoS rules of such PDU session. Interworking to 5GS is supported for a PDN connection, if the corresponding default EPS bearer context includes a PDU session identity, an S-NSSAI, if the PDN connection is a non-emergency PDN connection, session AMBR and one or more QoS flow descriptions received in the Protocol configuration options IE or Extended protocol configuration options IE (see 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [15]), or the default EPS bearer context has association with the PDU session identity, the S-NSSAI, if the PDU session is a non-emergency PDU session, the session-AMBR and one or more QoS flow descriptions after inter-system change from N1 mode to S1 mode. For a PDN connection established in S1 mode, to enable the UE to attempt to transfer the PDN connection from S1 mode to N1 mode in case of inter-system change, the UE shall allocate a PDU session identity, indicate the allocated PDU session identity in the PDU session ID parameter in the Protocol configuration options IE of the PDN CONNECTIVITY REQUEST message and associate the allocated PDU session identity with the default EPS bearer context of the PDN connection. If an N5CW device supporting 3GPP access establishes a new PDN connection in S1 mode, the N5CW device supporting 3GPP access shall refrain from allocating "PDU session identity value 15". For a PDN connection established in S1 mode, the SMF assigning the QoS rules shall consider that the UE supports 16 packet filters for the corresponding PDU session until the UE indicates a higher number (as specified in subclause 6.4.2.2). The network may provide the UE with one or more QoS rules by including either one QoS rules parameter, or one QoS rules with the length of two octets parameter, but not both, in the Protocol configuration options IE or Extended protocol configuration options IE in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST or ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST message. The network may provide the UE with one or more QoS flow descriptions corresponding to the EPS bearer context being activated, by including either one QoS flow descriptions parameter, or one QoS flow descriptions with the length of two octets parameter, but not both, in the Protocol configuration options IE or Extended protocol configuration options IE in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST or ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST message. When the UE is provided with one or more QoS flow descriptions in the Protocol configuration options IE or Extended protocol configuration options IE of the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST or ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST message, the UE shall check the EPS bearer identity included in the QoS flow description; and: a) if the EPS bearer identity corresponds to the EPS bearer context being activated or the EPS bearer identity is not included, the UE shall store the QoS flow description and all the associated QoS rules, if any, for the EPS bearer context being activated for use during inter-system change from S1 mode to N1 mode; and b) otherwise the UE shall locally delete the QoS flow description and all the associated QoS rules, if any, and include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #84 "syntactical error in the QoS operation" in the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT or ACTIVATE DEDICATED EPS BEARER CONTEXT ACCEPT message. When the UE is provided with one or more QoS rules, or one or more QoS flow descriptions in the Protocol configuration options IE or Extended protocol configuration options IE of the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST or ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST message, the UE shall process the QoS rules sequentially starting with the first QoS rule and shall process the QoS flow descriptions sequentially starting with the first QoS flow description. The UE shall check QoS rules and QoS flow descriptions for different types of errors as follows: NOTE 5: If an error is detected in a QoS rule or a QoS flow description which requires sending a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause value, then the QoS rules parameter, the QoS rules with the length of two octets parameter, the QoS flow descriptions parameter and the QoS flow descriptions with the length of two octets parameter included in the Protocol configuration options IE or Extended protocol configuration options IE in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST or ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST message are discarded, if any. NOTE 6: If the default EPS bearer context activation procedure or the dedicated EPS bearer context activation procedure is rejected, then the QoS rules parameter, the QoS rules with the length of two octets parameter, the QoS flow descriptions parameter and the QoS flow descriptions with the length of two octets parameter included in the Protocol configuration options IE or Extended protocol configuration options IE in the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST or ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST message are discarded, if any. a) Semantic errors in QoS operations: 1) When the rule operation is "Create new QoS rule" and the DQR bit is set to "the QoS rule is the default QoS rule" when there's already a default QoS rule. 2) When the rule operation is received in an ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message, the rule operation is "Create new QoS rule", and there is no rule with the DQR bit set to "the QoS rule is the default QoS rule". 3) When the rule operation is "Create new QoS rule" and two or more QoS rules associated with this PDU session would have identical precedence values. 4) When the rule operation is an operation other than "Create new QoS rule". 5) When the flow description operation is an operation other than "Create new QoS flow description". 6) When the UE determines that: i) the default EPS bearer context is associated with one or more QoS flows but the default EPS bearer context is not associated with the default QoS rules. ii) a dedicated EPS bearer context is associated with one or more QoS flows but the dedicated EPS bearer context is associated with the default QoS rule. 7) When the flow description operation is received in an ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST message, the flow description operation is "Create new QoS flow description" and there is already an existing QoS flow description with the same QoS flow identifier stored for an EPS bearer context different from the EPS bearer context being activated and belonging to the same PDN connection as the EPS bearer context being activated. 8) When the rule operation is received in an ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST message, the rule operation is "Create new QoS rule" and there is already an existing QoS rule with the same QoS rule identifier stored for an EPS bearer context different from the EPS bearer context being activated and belonging to the same PDN connection as the EPS bearer context being activated. 9) When the rule operation is received in an ACTIVATE DEDICATED EPS BEARER CONTEXT REQUEST message, the rule operation is "Create new QoS rule" and the resultant QoS rule is associated with a QoS flow description stored for an EPS bearer context different from the EPS bearer context being activated and belonging to the same PDN connection as the EPS bearer context being activated. 10) When the rule operation is "Create new QoS rule" and the DQR bit is set to "the QoS rule is not the default QoS rule" and one match-all packet filter is to be associated with the QoS rule. 11) When the flow description operation is "Create new QoS flow description" and there is already an existing QoS flow description with the same QoS flow identifier stored for the EPS bearer context being activated. 12) When the rule operation is "Create new QoS rule", and there is already an existing QoS rule with the same QoS rule identifier and the existing QoS rule is associated with a QoS flow description stored for the EPS bearer context being activated or the existing QoS rule is not associated with any QoS flow description. In case 4, if the rule operation is for a non-default QoS rule, the UE shall delete the QoS rule. If the QoS rule is the default QoS rule, the UE shall include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #83 "semantic error in the QoS operation" in the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT or ACTIVATE DEDICATED EPS BEARER CONTEXT ACCEPT message. In case 11, the UE shall not diagnose an error, further process the create request and, if it was processed successfully, delete the old QoS flow description (i.e. the QoS flow description that existed when case 11 was detected). In case 12, if the existing QoS rule is not the default QoS rule and the DQR bit of the new QoS rule is set to "the QoS rule is not the default QoS rule", the UE shall not diagnose an error, further process the create request and, if it was processed successfully, delete the old QoS rule (i.e. the QoS rule that existed when case 12 was detected). If the existing QoS rule is the default QoS rule or the DQR bit of the new QoS rule is set to "the QoS rule is the default QoS rule", the UE shall include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #83 "semantic error in the QoS operation" in the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT or ACTIVATE DEDICATED EPS BEARER CONTEXT ACCEPT message. Otherwise for all the cases above, the UE shall include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #83 "semantic error in the QoS operation" in the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT or ACTIVATE DEDICATED EPS BEARER CONTEXT ACCEPT message. b) Syntactical errors in QoS operations: 1) When the rule operation is "Create new QoS rule", the packet filter list in the QoS rule is empty, and the QoS rule is provided for a PDN connection of PDN type IPv4, IPv6, IPv4v6 or Ethernet, or for a PDN connection of PDN type "non-IP" and there is locally available information associated with the PDN connection that is set to "Ethernet". 2) Void. 3) When there are other types of syntactical errors in the coding of the QoS rules parameter, the QoS rules with the length of two octets parameter, the QoS flow descriptions parameter or the QoS flow descriptions with the length of two octets parameter, such as a mismatch between the number of packet filters subfield, and the number of packet filters in the packet filter list when the rule operation is "delete existing QoS rule" or "create new QoS rule", or the number of packet filters subfield is larger than the maximum possible number of packet filters in the packet filter list (i.e., there is no QoS rule precedence subfield included in the QoS rule IE), the QoS Rule Identifier is set to "no QoS rule identifier assigned", or the QoS flow identifier is set to "no QoS flow identifier assigned. 4) When, the A) rule operation is "Create new QoS rule", the UE determines, by using the QoS rule’s QFI as the 5QI, that there is a resulting QoS rule for a GBR QoS flow (as described in 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [8] table 5.7.4-1), and there is no QoS flow description with a QFI corresponding to the QFI of the resulting QoS rule. 5) When the flow description operation is "Create new QoS flow description", and the UE determines that there is a QoS flow description of a GBR QoS flow (as described in 3GPP TS 23.501[ System architecture for the 5G System (5GS) ]  [8] table 5.7.4-1) which lacks at least one of the mandatory parameters (i.e., GFBR uplink, GFBR downlink, MFBR uplink and MFBR downlink). If the QoS flow description does not include a 5QI, the UE determines this by using the QFI as the 5QI. The UE shall include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #84 "syntactical error in the QoS operation" in the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT or ACTIVATE DEDICATED EPS BEARER CONTEXT ACCEPT message. NOTE 7: It is not considered an error if the UE determines that after processing all QoS operations on QoS rules and QoS flow descriptions there is a QoS flow description that is not associated with any QoS rule and the UE is not in NB-N1 mode. c) Semantic errors in packet filters: 1) When a packet filter consists of conflicting packet filter components which would render the packet filter ineffective, i.e. no IP packet will ever fit this packet filter. How the UE determines a semantic error in a packet filter is outside the scope of the present document. The UE shall include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #44 "semantic errors in packet filter(s)" in the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT or ACTIVATE DEDICATED EPS BEARER CONTEXT ACCEPT message. d) Syntactical errors in packet filters: 1) When the rule operation is "Create new QoS rule" and two or more packet filters in the resultant QoS rule would have identical packet filter identifiers. 2) When there are other types of syntactical errors in the coding of packet filters, such as the use of a reserved value for a packet filter component identifier. The UE shall delete the QoS rule and include a Protocol configuration options IE or Extended protocol configuration options IE with a 5GSM cause parameter set to 5GSM cause #45 "syntactical error in packet filter(s)" in the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT or ACTIVATE DEDICATED EPS BEARER CONTEXT ACCEPT message. If the UE detects different errors in the QoS rules and QoS flow descriptions as described in this subclause which requires sending a 5GSM cause parameter in the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT or ACTIVATE DEDICATED EPS BEARER CONTEXT ACCEPT message, the UE shall include a single 5GSM cause parameter in the ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT or ACTIVATE DEDICATED EPS BEARER CONTEXT ACCEPT message. NOTE 8: The 5GSM cause to use cannot be different from #44 "semantic error in packet filter(s)", #45 "syntactical errors in packet filter(s)", #83 "semantic error in the QoS operation" or #84 "syntactical error in the QoS operation". The selection of a 5GSM cause is up to UE implementation. Upon inter-system change from S1 mode to N1 mode, the UE uses the parameters from the default EPS bearer context of each PDN connection for which interworking to 5GS is supported to create a corresponding PDU session associated with 3GPP access as follows, unless the PDN connection is a user-plane resource of an MA PDU session: a) the PDN type of the default EPS bearer context shall be mapped to the PDU session type of the PDU session as follows: 1) if the PDN type is "non-IP": - the PDU session type is set to the locally available information associated with the PDN connection (either "Ethernet" or "Unstructured"), if available; or - otherwise, the PDU session type is set to "Unstructured"; 2) if the PDN type is "IPv4" the PDU session type is set to "IPv4"; 3) if the PDN type is "IPv6", the PDU session type is set to "IPv6"; 4) if the PDN type is "IPv4v6", the PDU session type is set to "IPv4v6"; and 5) if the PDN type is "Ethernet", the PDU session type is "Ethernet"; b) the PDN address of the default EPS bearer context shall be mapped to PDU address of the PDU session, if the PDN type is "IPv4", "IPv6" or "IPv4v6"; c) the APN of the default EPS bearer context shall be mapped to the DNN of the PDU session, unless the PDN connection is an emergency PDN connection; d) for each default EPS bearer context in state BEARER CONTEXT ACTIVE the UE shall set the state of the mapped PDU session to PDU SESSION ACTIVE; and e) for any other default EPS bearer context the UE shall set the state of the mapped PDU session to PDU SESSION INACTIVE. Additionally, the UE shall set: a) the PDU session identity of the PDU session to the PDU session identity included by the UE in the Protocol configuration options IE or Extended protocol configuration options IE in the PDN CONNECTIVITY REQUEST message, or the PDU session identity associated with the default EPS bearer context; b) the S-NSSAI of the PDU session to the S-NSSAI included by the network in the Protocol configuration options IE or Extended protocol configuration options IE in the ACTIVATE DEFAULT EPS BEARER REQUEST message, or the S-NSSAI associated with the default EPS bearer context, if the PDN connection is a non-emergency PDN connection; c) the session-AMBR of the PDU session to the session-AMBR included by the network in the Protocol configuration options IE or Extended protocol configuration options IE in the ACTIVATE DEFAULT EPS BEARER REQUEST message or the MODIFY EPS BEARER CONTEXT REQUEST message, or the session-AMBR associated with the default EPS bearer context; d) the SSC mode of the PDU session to "SSC mode 1"; and e) the always-on PDU session indication to the always-on PDU session indication maintained in the UE, if any. Upon inter-system change from S1 mode to N1 mode, the UE shall locally release the PDN connection(s) for which interworking to 5GS is not supported. Upon inter-system change from S1 mode to N1 mode, for each PDN connection which is a user-plane resource of MA PDU session and for which interworking to 5GS is supported, the UE shall consider that the MA PDU session is established over 3GPP access and, unless the MA PDU session is established over non-3GPP access too, the UE shall set the session-AMBR of the PDU session to the session-AMBR included by the network in the Protocol configuration options IE or Extended protocol configuration options IE in the ACTIVATE DEFAULT EPS BEARER REQUEST message or the MODIFY EPS BEARER CONTEXT REQUEST message, or the session-AMBR associated with the default EPS bearer context of the PDN connection. Additionally, for each EPS bearer context of the PDN connection, the UE shall create QoS flow(s) each of which is associated with the QoS flow description received in the Protocol configuration options IE or Extended protocol configuration options IE in the ACTIVATE DEFAULT EPS BEARER REQUEST message, ACTIVATE DEDICATED EPS BEARER REQUEST message, or MODIFY EPS BEARER REQUEST message (see 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [15]), or the QoS flow description associated with EPS bearer context, unless: a) the PDU session is an MA PDU session which: 1) is established over non-3GPP access; and 2) has a PDN connection as a user-plane resource; and b) the QoS flow already exists over the non-3GPP access. Additionally, for each EPS bearer context of the PDN connection, the UE shall create QoS rules(s), if any, each of which is associated with the QoS rule received in the Protocol configuration options IE or Extended protocol configuration options IE in the ACTIVATE DEFAULT EPS BEARER REQUEST message, ACTIVATE DEDICATED EPS BEARER REQUEST message, or MODIFY EPS BEARER CONTEXT REQUEST message (see 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [15]), or the QoS rules associated with EPS bearer context, unless: a) the PDU session is an MA PDU session which: 1) is established over non-3GPP access; and 2) has a PDN connection as a user-plane resource; and b) the QoS rule already exists over the non-3GPP access. NOTE 9: For a QoS rule which does not exist over non-3GPP access, the UE does not create the QoS rule if the QoS rule is the default QoS rule, or the precedence value of the QoS rule equals to the precedence value of a QoS rule exists over the non-3GPP access. Additionally, for each PDU session which was created at inter-system change from S1 mode to N1 mode from a corresponding PDN connection of the "Ethernet" PDN type, the UE shall consider that Ethernet PDN type in S1 mode is supported by the network and the SMF shall consider that Ethernet PDN type in S1 mode is supported by the UE. The UE and the network shall locally release the PDN connection(s) and EPS bearer context(s) associated with the 3GPP access which have not been transferred to 5GS. After inter-system change from S1 mode to N1 mode, for each QoS flow mapped from an EPS bearer context the UE shall associate the EPS bearer identity, the EPS QoS parameters, the extended EPS QoS parameters, and the traffic flow template, if available, of the EPS bearer context with the QoS flow. After inter-system change from S1 mode to N1 mode, for each QoS flow of an MA PDU session which: a) is established over non-3GPP access; and b) has a PDN connection as a user-plane resource; such that the QoS flow was received in the Protocol configuration options IE or Extended protocol configuration options IE in the ACTIVATE DEFAULT EPS BEARER REQUEST message, ACTIVATE DEDICATED EPS BEARER REQUEST message, MODIFY EPS BEARER CONTEXT REQUEST message, (see 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [15]), or associated with EPS bearer context, the UE shall associate the EPS bearer identity, the EPS QoS parameters, the extended EPS QoS parameters, and the traffic flow template, if available, of the EPS bearer context with the QoS flow. If the EPS bearer context(s) of the PDN connection are associated with the control plane only indication, and the PDN connection supports interworking to 5GS, after inter-system change from S1 mode to N1 mode, the UE shall associate the PDU session corresponding to the PDN connection with the control plane only indication. If the default EPS bearer context of the PDN connection is associated with the PDU session pair ID, and the PDN connection supports interworking to 5GS, after inter-system change from S1 mode to N1 mode, the UE shall associate the PDU session corresponding to the PDN connection with the PDU session pair ID. If the default EPS bearer context of the PDN connection is associated with the RSN, and the PDN connection supports interworking to 5GS, after inter-system change from S1 mode to N1 mode, the UE shall associate the PDU session corresponding to the PDN connection with the RSN. If there is an EPS bearer used for IMS signalling, after inter-system change from S1 mode to N1 mode, the QoS flow of the default QoS rule in the corresponding PDU session is used for IMS signalling. For a PDN connection established when in S1 mode, upon an inter-system change from S1 mode to N1 mode, if a UE-requested PDU session modification procedure has not been successfully performed yet,the SMF shall determine the always-on PDU session indication as specified in subclause 6.3.2.2. When the UE is provided with one or more mapped EPS bearer contexts in the Mapped EPS bearer contexts IE of the PDU SESSION MODIFICATION COMMAND message, the UE shall process the mapped EPS bearer contexts sequentially starting with the first mapped EPS bearer context. When the UE is provided with a new EPS bearer identity, a new EPS QoS parameters, a new extended EPS QoS parameters, a new APN-AMBR or a new extended APN-AMBR in the Mapped EPS bearer context IE of the PDU SESSION MODIFICATION COMMAND message for a QoS flow, the UE shall discard the corresponding association(s) and associate the new value(s) with the QoS flow. When the UE is provided with a new traffic flow template in the Mapped EPS bearer contexts IE of the PDU SESSION MODIFICATION COMMAND message for a QoS flow, the UE shall check the traffic flow template for different types of TFT IE errors as specified in subclause 6.3.2.3. When a QoS flow is deleted, the associated EPS bearer context information that are mapped from the deleted QoS flow shall be deleted from the UE and the network if there is no other existing QoS flow associated with this EPS bearer context. When the EPS bearer identity of a QoS flow is deleted, the associated EPS bearer context information that are mapped from the deleted EPS bearer identity shall be deleted from the UE and the network if there is no other existing QoS flow associated with this EPS bearer context. When an EPS bearer is released, all the associated QoS flow descriptions and QoS rules that are mapped from the released EPS bearer shall be deleted from the UE and the network. NOTE 10: If T3584 is running or deactivated for the S-NSSAI and optionally the DNN combination, the UE is allowed to initate ESM procedures in EPS with or without APN corresponding to that DNN, and if the APN is congested in EPS, the MME can send a back-off timer for the APN to the UE as specified in 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [15]. Upon inter-system change from N1 mode to S1 mode, if the UE has any PDU sessions associated with one or more multicast MBS sessions, the UE shall locally leave the associated multicast MBS sessions and the network shall consider the UE as removed from the associated MBS sessions. For the case of handover of an existing PDU session from 3GPP access to non-3GPP access, - upon receipt of the PDU SESSION ESTABLISHMENT ACCEPT message, the UE locally deletes the EPS bearer identities for the PDU session, if any (see subclause 6.4.1.3); and - after successful handover, the network shall locally delete the EPS bearer identities for the PDU session, if any.