4 Descriptions of UE policies for 5GS

24.5263GPPRelease 17Stage 3TSUser Equipment (UE) policies for 5G System (5GS)

4.1 Overview

The UE policies for 5GS include:

– UE route selection policy(URSP)(see clause 4.2); and

– Access network discovery and selection policy(ANDSP)(see clause 4.3).

The UE policies can be delivered from the PCF to the UE. The UE policy delivery procedure is specified in 3GPP TS 24.501 [11].

The UE policies can also be pre-configured in the UE. The pre-configured policy shall be applied by the UE only when the UE has not received the same type of policy from the PCF. The implementation of pre-configured UE policies is out of scope of this specification.

The UE policies can be delivered from the PCF to the 5G-RG or a W-AGF acting on behalf of the FN-RG. The UE policy delivery service is specified in 3GPP TS 24.501 [11]. These UE policies include the UE route selection policy (URSP) (see clause 4.2).

The UE policies can also be pre-configured in the 5G-RG or a W-AGF acting on behalf of the FN-RG. The pre-configured policy shall be applied by the 5G-RG or a W-AGF acting on behalf of the FN-RG only when the 5G-RG or a W-AGF acting on behalf of the FN-RG has not received the same type of policy from the PCF. The implementation of pre-configured UE policies is out of scope of this specification.

The UE policies for V2X (V2XP) are specified in 3GPP TS 24.588 [18].

The UE policies for 5G ProSe policy (ProSeP) are specified in 3GPP TS 24.555 [18A].

4.2 UE route selection policy (URSP)

4.2.1 General

The URSP is defined in 3GPP TS 23.503 [2] and is a set of one or more URSP rules, where a URSP rule is composed of:

a) a precedence value of the URSP rule identifying the precedence of the URSP rule among all the existing URSP rules;

b) a traffic descriptor, including either:

1) match-all traffic descriptor; or

2) at least one of the following components:

A) one or more application identifiers;

B) one or more IP 3 tuples as defined in 3GPP TS 23.503 [2] i.e. the destination IP address, the destination port number, and the protocol in use above the IP;

C) one or more non-IP descriptors, i.e. destination information of non-IP traffic;

D) one or more DNNs;

E) one or more connection capabilities; and

F) one or more domain descriptors, i.e. destination FQDN(s) or a regular expression as a domain name matching criteria; and

c) one or more route selection descriptors each consisting of a precedence value of the route selection descriptor and either

1) one PDU session type and, optionally, one or more of the followings:

A) SSC mode;

B) one or more S-NSSAIs;

C) one or more DNNs;

D) Void;

E) preferred access type;

F) multi-access preference;

G) a time window;

H) location criteria;

I) PDU session pair ID; and

J) RSN;

2) non-seamless non-3GPP offload indication; or

3) 5G ProSe layer-3 UE-to-network relay offload indication.

Only one URSP rule in the URSP can be a default URSP rule and the default URSP rule shall contain a match all traffic descriptor. If a default URSP rule and one or more non-default URSP rules are included in the URSP, any non-default URSP rule shall have lower precedence value than (i.e. shall be prioritised over) the default URSP rule.

If a traffic descriptor lists one or more application identifiers together with one or more connection capabilities, the UE shall consider that the application identifiers identify the applications requesting access to the connection capabilities.

NOTE 1: The connection capabilities requested by the applications are OS dependent. The connection capability identifiers defined in table 5.2.1 are OS independent. It is based on the UE implementation how the UE matches the connection capabilities requested by the applications to the connection capability identifiers in table 5.2.1.

NOTE 2: If the UE has multiple concurrently active OS, the traffic descriptor can list as many multiple OS Ids.

NOTE 3: It is recommended to avoid the combination of more than two components in the traffic descriptor.

4.2.2 Association between an application and a PDU session, non-seamless non-3GPP offload or 5G ProSe layer-3 UE-to-network relay offload

4.2.2.1 General

Association between an application and a PDU session, non-seamless non-3GPP offload or 5G ProSe Layer-3 UE-to-network relay offload is described separately for a UE and for a 5G-RG or a W-AGF acting on behalf of an FN-RG. Clause 4.2.2.2 is not applicable for the 5G-RG or the W-AGF acting on behalf of the FN-RG.

4.2.2.2 Association between an application and a PDU session, non-seamless non-3GPP offload or 5G ProSe layer-3 UE-to-network relay offload by a UE

In order to send a PDU of an application, the upper layers require information on the PDU session (e.g. PDU address) via which to send a PDU of an application.

NOTE 0: If PAP/CHAP is used, it is recommended that the request from the upper layers includes a DNN.

When the upper layers request information of the PDU session via which to send a PDU of an application;

– information on the non-3GPP access outside of a PDU session shall be provided to the upper layers, without evaluating the URSP rules, if due to UE local configuration non-seamless non-3GPP offload is requested; or

– information on the 5G ProSe layer-3 UE-to-network relay shall be provided to the upper layers, without evaluating the URSP rules, if due to UE local configuration 5G ProSe layer-3 UE-to-network relay offload is requested;

otherwise, the UE shall proceed in the following order:

a) the UE shall evaluate the URSP rules, except the default URSP rule, with a traffic descriptor matching the application information in increasing order of their precedence values, if any. If the traffic descriptor contains more than one traffic descriptor component type, each of a different type, all of them shall be matched. If the traffic descriptor contains more than one traffic descriptor component of the same traffic descriptor component type, at least one of the traffic descriptor components of the same traffic descriptor component type shall be matched with the application information. A URSP rule is determined not to be applicable when for any given component in the traffic descriptor no corresponding information from the application is available or the corresponding information from the application does not match any of the values in the traffic descriptor component as specified in clause 6.6.2.1 of 3GPP TS 23.503 [2].

If the UE finds the traffic descriptor in a non-default URSP rule matching the application information, and:

I) if:

1) at least one of the route selection descriptors of the URSP rule contains a non-seamless non-3GPP offload indication and the information on the non-3GPP access outside of a PDU session is available;

the UE shall provide information on the non-3GPP access outside of a PDU session to the upper layers; and

2) there is one or more PDU sessions:

i) matching at least one of the route selection descriptors of the URSP rule except the preferred access type and the multi-access preference, if any, wherein a route selection descriptor with PDU session type IPv4v6 matches also with PDU session type IPv4 if the network has sent 5GSM cause value #50 "PDU session type IPv4 only allowed" in the PDU SESSION ESTABLISHMENT ACCEPT message, a route selection descriptor with PDU session type IPv4v6 matches also with PDU session type IPv6 if the network has sent 5GSM cause value #51 "PDU session type IPv6 only allowed" in the PDU SESSION ESTABLISHMENT ACCEPT message and a route selection descriptor with PDU session type IPv4v6 matches also with PDU session type IPv6 or IPv4 if the UE requested the PDU session type IPv4v6 but the selected PDU session type is set to IPv4 or IPv6 in the PDU SESSION ESTABLISHMENT ACCEPT message; and

ii) established without requesting any parameter for which the matching route selection descriptor of the URSP rule does not provide a route selection descriptor component, except:

A) the preferred access type;

B) the multi-access preference;

C) the DNN, if no DNN is included in the route selection descriptor component and the DNN provided by the application is the same as the DNN requested by the UE during the PDU session establishment; and

D) the S-NSSAI, if the UE has only one S-NSSAI in the allowed NSSAI.

the UE shall provide information on the PDU session that matches the route selection descriptor of the lowest precedence value to the upper layers;

NOTE 1: It is up to the UE implementation which PDU session to select if there exist multiple PDU sessions matching the same route selection descriptor of the lowest precedence value.

II) otherwise:

1) the UE shall select a route selection descriptor with the next smallest precedence value which has not yet been evaluated;

2) if:

i) the selected route selection descriptor contains a non-seamless non-3GPP offload indication:

A) if the information on the non-3GPP access outside of a PDU session is available, it shall be provided to the upper layers and the UE shall stop selecting a route selection descriptor matching the application information.

B) if the information about the non-3GPP access outside of a PDU session is not available, or non-3GPP access is not available the UE shall proceed to step 4);

ia) the selected route selection descriptor contains a 5G ProSe layer-3 UE-to-network relay offload indication:

A) if the information on the 5G ProSe layer-3 UE-to-network relay is available and the UE supports acting as ProSe layer-3 UE-to-network remote UE as specified in 3GPP TS 24.501 [11], it shall be provided to the upper layers and the UE shall stop selecting a route selection descriptor matching the application information.

B) if the information about the 5G ProSe layer-3 UE-to-network relay is not available or the UE does not support acting as ProSe layer-3 UE-to-network remote UE as specified in 3GPP TS 24.501 [11], the UE shall proceed to step 4);

ii) the selected route selection descriptor includes a PDU session type or an SSC mode which is not supported by the UE, the UE shall proceed to step 4);

iii) the selected route selection descriptor contains a time window but the time does not match the time window, the UE shall proceed to step 4);

iv) the selected route selection descriptor contains location criteria but the UE location does not match the location criteria, the UE shall proceed to step 4);

v) the selected route selection descriptor includes the multi-access preference but the UE does not support ATSSS, the UE shall proceed to step 4);

va) the selected route selection descriptor includes an SSC mode which either has been rejected by the network with 5GSM cause value #68 "not supported SSC mode" for the same DNN (or no DNN, if no DNN was indicated by the UE) and the same S-NSSAI associated with (if available in roaming scenarios) a mapped S-NSSAI (or no S-NSSAI, if no S-NSSAI was indicated by the UE) or was not included in the Allowed SSC mode IE following a rejection with 5GSM cause value #68 "not supported SSC mode" for the same DNN (or no DNN, if no DNN was indicated by the UE) and the same S-NSSAI associated with (if available in roaming scenarios) a mapped S-NSSAI (or no S-NSSAI, if no S-NSSAI was indicated by the UE), the UE shall proceed to step 4); or

vi) the selected route selection descriptor does not contain a non-seamless non-3GPP offload indication nor a 5G ProSe layer-3 UE-to-network relay offload indication, the URSP handling layer requests the UE NAS layer to establish a PDU session providing the following PDU session attributes based on the selected route selection descriptor:

A) SSC mode if there is a SSC mode in the route selection descriptor;

NOTE 2: The SSC mode 3 is only used when the PDU session type is IPv4, IPv6 or IPv4v6.

B) one S-NSSAI if the S-NSSAI is in the route selection descriptor; and the S-NSSAI is in the allowed NSSAI. If none of the S-NSSAI(s) in the route selection descriptor is in the allowed NSSAI, the UE shall proceed to step 4);

NOTE 3: If there are multiple S-NSSAIs in the route selection descriptor, an S-NSSAI is chosen among the S-NSSAIs based on UE implementation.

C) one DNN, if the DNN is in the route selection descriptor; and if the DNN is an LADN DNN and the UE is in the service area of that LADN;

NOTE 4: If one or more DNNs are included in the traffic descriptor and no DNN is included in the route selection descriptor, the DNN provided by the application is selected as one of the PDU session attributes by the URSP handling layer to request the UE NAS layer.

NOTE 5: If there are multiple DNNs in the route selection descriptor, a DNN is chosen based on UE implementation.

D) the PDU session type of the route selection descriptor;

E) preferred access type or multi-access preference, if the preferred access type or the multi-access preference is in the route selection descriptor; and

NOTE 6: If a preferred access type or a multi-access preference is included in the traffic descriptor of a URSP rule, it is recommended that the UE establishes a PDU session based on the preferred access type or the multi-access preference.

The UE NAS layer indicates the result of the PDU session establishment. Upon successful completion of the PDU session establishment, the UE NAS layer shall additionally indicate the attributes of the established PDU session (e.g. PDU session identity, SSC mode, S-NSSAI, DNN, PDU session type, access type, PDU address) to the URSP handling layer, and shall provide information (e.g. PDU address) of the successfully established PDU session to the upper layers. The UE shall stop selecting a route selection descriptor matching the application information. If the PDU session establishment is unsuccessful, the UE shall proceed to step 3);

3) Based on the rejection cause and if there is another value which can be used for the rejected component in the same route selection descriptor, the UE shall select another combination of values in the currently selected route selection descriptor by using this value of the rejected component and proceed to step 2), otherwise the UE shall proceed to step 4); and

4) if there is any route selection descriptor which has not yet been evaluated, the UE shall proceed to step 1). If all route selection descriptors for the matching non-default URSP rule have been evaluated and there is one or more non-default matching URSP rule which has not yet been evaluated, the UE shall proceed to step a). If all non-default matching URSP rules have been evaluated, the UE shall inform the upper layers of the failure.

b) if no non-default matching URSP rule can be found and if UE local configuration for the application is available, the UE shall perform the association of the application to a PDU session accordingly. If no matching PDU session exists, the UE NAS layer shall attempt to establish a PDU session using UE local configuration.

NOTE 7: Any missing information in the UE local configuration needed to build the PDU session establishment request can be the appropriate corresponding component from the default URSP rule with the "match-all" traffic descriptor.

NOTE 8: If a DNN was provided by the application and no DNN is included in the UE local configuration, the DNN provided by the application is selected as one of the PDU session attributes by the URSP handling layer to request the UE NAS layer.

NOTE 9: If there are multiple DNNs in the UE local configuration, a DNN is chosen based on UE implementation.

If the PDU session establishment is successful, the UE NAS layer shall provide information (e.g. PDU address) of the successfully established PDU session to the upper layers. Otherwise, the UE shall go to step c);

c) if no non-default matching URSP rule can be found and if either UE local configuration for the application is not available or the PDU session establishment based on UE local configuration for the application was unsuccessful, the UE shall perform the association of the application to a PDU session, to non-seamless non-3GPP offload or to 5G ProSe layer-3 UE-to-network relay offload according to the default URSP rule with the "match-all" traffic descriptor, if any. If the association is unsuccessful, the UE shall inform the upper layers of the failure.

NOTE 10: If a DNN was provided by the application and no DNN is included in the route selection descriptor of the default URSP rule, the DNN provided by the application is selected as one of the PDU session attributes by the URSP handling layer to request the UE NAS layer. If one or more DNNs are included in the route selection descriptor of the default URSP rule, the DNN in the route selection descriptor is selected as one of the PDU session attributes by the URSP handling layer to request the UE NAS layer. When there are multiple DNNs in the route selection descriptor, the DNN is selected based on UE implementation.

The HPLMN may pre-configure the UE with URSP in the ME or in the USIM and the SNPN(s) may pre-configure the UE with URSP in the corresponding entry of the "list of subscriber data" stored in ME, or the HPLMN and the SNPN(s) may provide URSP to the UE by signalling as described in annex D of 3GPP TS 24.501 [11]. The HPLMN pre-configured URSP in the ME and the HPLMN signalled URSP shall be stored in a non-volatile memory in the ME together with the SUPI from the USIM. The SNPN(s) signalled URSP shall be stored per SNPN in a non-volatile memory in the ME together with the subscriber identifier and the associated SNPN identity of the SNPN in the "list of subscriber data" configured in the ME. The SNPN(s) pre-configured URSP and the SNPN(s) signalled URSP shall be used only when the selected SNPN identity matches the associated SNPN identity. If the UE has both pre-configured URSP(s) and signalled URSP, the UE shall only use the signalled URSP. For a UE not operating in SNPN access operation mode, if the UE has no signalled URSP, the UE shall:

– only use the pre-configured URSP rules of the HPLMN and ignore URSP rules of other PLMN(s) in the USIM, if there are pre-configured URSP rules of the HPLMN in the USIM; or

– use the pre-configured URSP rules in the ME if the UE has pre-configured URSP in the ME and:

– only pre-configured URSP rules of PLMN(s) other than HPLMN in the USIM; or

– no pre-configured URSP in the USIM.

The HPLMN pre-configured URSP in the ME shall be stored until a new URSP is configured by HPLMN or the USIM is removed.

For a UE not operating in SNPN access operation mode, the signalled URSP may be modified by the procedures defined in annex D of 3GPP TS 24.501 [11] and shall be stored until USIM is removed. The URSP can only be used if the SUPI from the USIM matches the SUPI stored in the non-volatile memory of the ME. If the SUPI from the USIM does not match the SUPI stored in the non-volatile memory of the ME, the UE shall delete the URSP.

For a UE operating in SNPN access operation mode, the signalled URSP may be modified by the procedures defined in annex D of 3GPP TS 24.501 [11] and shall be stored until the entry of the "list of subscriber data" with the corresponding SNPN identity is updated or considered as "invalid".

The UE may re-evaluate the URSP rules, to check if the change of the association of an application to a PDU session is needed, when:

NOTE 11: The time when the UE performs the re-evaluation is up to UE implementation. It is recommended that the UE performs the re-evaluation in a timely manner.

a) the UE performs periodic URSP rules re-evaluation based on UE implementation;

b) the UE NAS layer indicates that an existing PDU session used for routing traffic of an application based on a URSP rule is released;

c) the URSP is updated by the PCF;

d) the UE NAS layer indicates that the UE performs inter-system change from S1 mode to N1 mode;

e) the UE NAS layer indicates that the UE is successfully registered in N1 mode over 3GPP access or non-3GPP access;

f) the UE establishes or releases a connection to a WLAN access and transmission of a PDU of the application via non-3GPP access outside of a PDU session becomes available/unavailable;

g) the allowed NSSAI or the configured NSSAI is changed; or

h) the LADN information is changed.

If the re-evaluation leads to a change of the association of an application to a PDU session, the UE may enforce such change immediately or when UE returns to 5GMM-IDLE mode.

NOTE 12: The time when the UE enforces the change of the association of an application to a PDU Session is up to UE implementation. It is recommended that the UE performs the enforcement in a timely manner.

The URSP handling layer may request the UE NAS layer to release an existing PDU session after the re-evaluation.

4.2.2.3 Association between an application and a PDU session by a 5G-RG or a W-AGF acting on behalf of FN-RG

In order to send a PDU of an application, the upper layers require information on the PDU session (e.g. PDU address) via which to send a PDU of an application.

NOTE 1: If PAP/CHAP is used, it is recommended that the request from the upper layers includes a DNN.

The 5G-RG or the W-AGF acting on behalf of the FN-RG shall proceed in the following order:

a) the 5G-RG or the W-AGF acting on behalf of the FN-RG shall evaluate the URSP rules, except the default URSP rule, with a traffic descriptor matching the application information in increasing order of their precedence values, if any. If the traffic descriptor contains more than one traffic descriptor component type, each of a different type, all of them shall be matched. If the traffic descriptor contains more than one traffic descriptor component of the same traffic descriptor component type, at least one of the traffic descriptor components of the same traffic descriptor component type shall be matched with the application information. A URSP rule is determined not to be applicable when for any given component in the traffic descriptor no corresponding information from the application is available or the corresponding information from the application does not match any of the values in the traffic descriptor component as specified in clause 6.6.2.1 of 3GPP TS 23.503 [2].

If the 5G-RG or the W-AGF acting on behalf of the FN-RG finds the traffic descriptor in a non-default URSP rule matching the application information, and:

I) if there is one or more PDU sessions:

1) matching at least one of the route selection descriptors of the URSP rule except the preferred access type and the multi-access preference, if any, wherein a route selection descriptor with PDU session type IPv4v6 matches also with PDU session type IPv4 if the network has sent 5GSM cause value #50 "PDU session type IPv4 only allowed" in the PDU SESSION ESTABLISHMENT ACCEPT message, a route selection descriptor with PDU session type IPv4v6 matches also with PDU session type IPv6 if the network has sent 5GSM cause value #51 "PDU session type IPv6 only allowed" in the PDU SESSION ESTABLISHMENT ACCEPT message, and a route selection descriptor with PDU session type IPv4v6 matches also with PDU session type IPv6 or IPv4 if the UE requested the PDU session type IPv4v6 but the selected PDU session type is set to IPv4 or IPv6 in the PDU SESSION ESTABLISHMENT ACCEPT message; and

2) established without requesting any parameter, except the preferred access type and the multi-access preference, for which the matching route selection descriptor of the URSP rule does not provide a route selection descriptor component,

the 5G-RG or the W-AGF acting on behalf of the FN-RG shall provide information on the PDU session that matches the route selection descriptor of the lowest precedence value to the upper layers;

NOTE 2: It is up to the 5G-RG or the W-AGF acting on behalf of the FN-RG implementation which PDU session to select if there exist multiple PDU sessions matching the same route selection descriptor of the lowest precedence value.

II) otherwise:

1) the 5G-RG or the W-AGF acting on behalf of the FN-RG shall select a route selection descriptor with the next smallest precedence value which has not yet been evaluated;

2) if:

i) the selected route selection descriptor contains a non-seamless non-3GPP offload indication, the 5G-RG or the W-AGF acting on behalf of the FN-RG shall proceed to step 4);

ii) the selected route selection descriptor includes a PDU session type which is not supported by the 5G-RG or the W-AGF acting on behalf of the FN-RG, the 5G-RG or the W-AGF acting on behalf of the FN-RG shall proceed to step 4);

iii) the selected route selection descriptor contains a time window but the time does not match the time window, the 5G-RG or the W-AGF acting on behalf of the FN-RG shall proceed to step 4);

iv) the selected route selection descriptor contains location criteria but location of the 5G-RG or the W-AGF acting on behalf of the FN-RG does not match the location criteria, the 5G-RG or the W-AGF acting on behalf of the FN-RG shall proceed to step 4);

v) the selected route selection descriptor includes the multi-access preference but the 5G-RG or the W-AGF acting on behalf of the FN-RG does not support ATSSS, the 5G-RG or the W-AGF acting on behalf of the FN-RG shall proceed to step 4);

va) the selected route selection descriptor includes an SSC mode which either has been rejected by the network with 5GSM cause value #68 "not supported SSC mode" for the same DNN (or no DNN, if no DNN was indicated by the 5G-RG or the W-AGF acting on behalf of the FN-RG) and the same S-NSSAI associated with (if available in roaming scenarios) a mapped S-NSSAI (or no S-NSSAI, if no S-NSSAI was indicated by the 5G-RG or the W-AGF acting on behalf of the FN-RG) or was not included in the Allowed SSC mode IE following a rejection with 5GSM cause value #68 "not supported SSC mode" for the same DNN (or no DNN, if no DNN was indicated by the 5G-RG or the W-AGF acting on behalf of the FN-RG) and the same S-NSSAI associated with (if available in roaming scenarios) a mapped S-NSSAI (or no S-NSSAI, if no S-NSSAI was indicated by the 5G-RG or the W-AGF acting on behalf of the FN-RG), the 5G-RG or the W-AGF acting on behalf of the FN-RG shall proceed to step 4); or

vi) the URSP handling layer requests NAS layer of the 5G-RG or the W-AGF acting on behalf of the FN-RG to establish a PDU session providing at least one of the following PDU session attributes:

A) SSC mode if there is a SSC mode in the route selection descriptor;

NOTE 3: The SSC mode 3 is only used when the PDU session type is IPv4, IPv6 or IPv4v6.

B) one S-NSSAI if the S-NSSAI is in the route selection descriptor; and the S-NSSAI is in the allowed NSSAI. If none of the S-NSSAI(s) in the route selection descriptor is in the allowed NSSAI, the 5G-RG or the W-AGF acting on behalf of the FN-RG shall proceed to step 4);

NOTE 4: If there are multiple S-NSSAIs in the route selection descriptor, an S-NSSAI is chosen among the S-NSSAIs based on implementation of the 5G-RG or the W-AGF acting on behalf of the FN-RG.

C) one DNN, if the DNN is in the route selection descriptor; and if the DNN is an LADN DNN and the 5G-RG is in the service area of that LADN;

NOTE 5: The LADN service does not apply for either 5G-RG connected to 5GC via wireline access or the W-AGF acting on behalf of the FN-RG.

NOTE 6: If one or more DNNs are included in the traffic descriptor of a URSP rule and no DNN is included in the route selection descriptor, the DNN provided by the application is selected as one of the PDU session attributes by the URSP handling layer to request the UE NAS layer.

NOTE 7: If there are multiple DNNs in the route selection descriptor, a DNN is chosen based on implementation of the 5G-RG or the W-AGF acting on behalf of the FN-RG.

D) the PDU session type of the route selection descriptor;

E) preferred access type or multi-access preference, if the preferred access type or the multi-access preference is in the route selection descriptor; and

NOTE 8: If a preferred access type or a multi-access preference is included in the traffic descriptor of a URSP rule, it is recommended that the 5G-RG or the W-AGF acting on behalf of the FN-RG establishes a PDU session based on the preferred access type or the multi-access preference.

the NAS layer of the 5G-RG or the W-AGF acting on behalf of the FN-RG indicates the result of the PDU session establishment. Upon successful completion of the PDU session establishment, the NAS layer of the 5G-RG or the W-AGF acting on behalf of the FN-RG shall additionally indicate the attributes of the established PDU session (e.g. PDU session identity, SSC mode, S-NSSAI, DNN, PDU session type, access type, PDU address) to the URSP handling layer, and shall provide information (e.g. PDU address) of the successfully established PDU session to the upper layers. The 5G-RG or the W-AGF acting on behalf of the FN-RG shall stop selecting a route selection descriptor matching the application information. If the PDU session establishment is unsuccessful, the 5G-RG or the W-AGF acting on behalf of the FN-RG shall proceed to step 3);

3) Based on the rejection cause and if there is another value which can be used for the rejected component in the same route selection descriptor, the 5G-RG or the W-AGF acting on behalf of the FN-RG shall select another combination of values in the currently selected route selection descriptor by using this value of the rejected component and proceed to step 2), otherwise the 5G-RG or the W-AGF acting on behalf of the FN-RG shall proceed to step 4); and

4) if there is any route selection descriptor which has not yet been evaluated, the 5G-RG or the W-AGF acting on behalf of the FN-RG shall proceed to step 1). If all route selection descriptors for the matching non-default URSP rule have been evaluated and there is one or more non-default matching URSP rule which has not yet been evaluated, the 5G-RG or the W-AGF acting on behalf of the FN-RG shall proceed to step a). If all non-default matching URSP rules have been evaluated, the 5G-RG or the W-AGF acting on behalf of the FN-RG shall inform the upper layers of the failure.

b) if no non-default matching URSP rule can be found:

1) by the 5G-RG and local configuration of the 5G-RG for the application is available, the 5G-RG shall perform the association of the application to a PDU session accordingly. If no matching PDU session exists, the NAS layer of the 5G-RG shall attempt to establish a PDU session using local configuration of the 5G-RG.

NOTE 9: Any missing information in local configuration of the 5G-RG needed to build the PDU session establishment request can be the appropriate corresponding component from the default URSP rule with the "match-all" traffic descriptor.

If the PDU session establishment is successful, the NAS layer of the 5G-RG shall provide information (e.g. PDU address) of the successfully established PDU session to the upper layers. Otherwise, the 5G-RG shall go to step c); or

2) by the W-AGF acting on behalf of the FN-RG, the W-AGF acting on behalf of the FN-RG shall go to step c); and

c) if no non-default matching URSP rule can be found:

1) by the 5G-RG and if either local configuration of the 5G-RG for the application is not available or the PDU session establishment based on local configuration of the 5G-RG for the application was unsuccessful, the 5G-RG shall perform the association of the application to a PDU session according to the default URSP rule with the "match-all" traffic descriptor, if any. If the association is unsuccessful, the 5G-RG shall inform the upper layers of the failure; or

2) by the W-AGF acting on behalf of the FN-RG, the W-AGF acting on behalf of the FN-RG shall perform the association of the application to a PDU session according to the default URSP rule with the "match-all" traffic descriptor, if any. If the association is unsuccessful, and local configuration of the W-AGF acting on behalf of the FN-RG for the application is available, the W-AGF acting on behalf of the FN-RG shall perform the association of the application to a PDU session accordingly. If no matching PDU session exists, the NAS layer of the W-AGF acting on behalf of the FN-RG shall attempt to establish a PDU session using local configuration of the W-AGF acting on behalf of the FN-RG. If the PDU session establishment is successful, the NAS layer of the W-AGF acting on behalf of the FN-RG shall provide information (e.g. PDU address) of the successfully established PDU session to the upper layers. Otherwise, the W-AGF acting on behalf of the FN-RG shall inform the upper layers of the failure.

The HPLMN may pre-configure the 5G-RG or the W-AGF acting on behalf of the FN-RG with URSP or may provide URSP to the 5G-RG or the W-AGF acting on behalf of the FN-RG by signalling as described in annex D of 3GPP TS 24.501 [11]. In the 5G-RG, the pre-configured URSP and the signalled URSP shall be stored in a non-volatile memory in the ME together with the SUPI from the USIM. If the 5G-RG or the W-AGF acting on behalf of the FN-RG has both pre-configured URSP and signalled URSP, the 5G-RG or the W-AGF acting on behalf of the FN-RG shall only use the signalled URSP. The pre-configured URSP shall be stored until a new URSP is configured by HPLMN or the USIM is removed from the 5G-RG. The signalled URSP may be modified by the procedures defined in annex D of 3GPP TS 24.501 [11] and shall be stored until USIM is removed from the 5G-RG or until W-AGF acting on behalf of the FN-RG deregisters on behalf of the FN-RG. In the 5G-RG, the URSP can only be used if the SUPI from the USIM matches the SUPI stored in the non-volatile memory of the ME. In the 5G-RG, if the SUPI from the USIM does not match the SUPI stored in the non-volatile memory of the ME, the 5G-RG shall delete the URSP.

The 5G-RG or the W-AGF acting on behalf of the FN-RG may re-evaluate the URSP rules, to check if the change of the association of an application to a PDU session is needed, when:

NOTE 10: The time when the 5G-RG or the W-AGF acting on behalf of the FN-RG performs the re-evaluation is up to implementation of the 5G-RG or the W-AGF acting on behalf of the FN-RG. It is recommended that the 5G-RG or the W-AGF acting on behalf of the FN-RG performs the re-evaluation in a timely manner.

a) the 5G-RG or the W-AGF acting on behalf of the FN-RG performs periodic URSP rules re-evaluation based on implementation of the 5G-RG or the W-AGF acting on behalf of the FN-RG;

b) the NAS layer of the 5G-RG or the W-AGF acting on behalf of the FN-RG indicates that an existing PDU session used for routing traffic of an application based on a URSP rule is released;

c) the URSP is updated by the PCF;

d) the NAS layer of the 5G-RG indicates that the 5G-RG performs inter-system change from S1 mode to N1 mode;

e) the NAS layer of the 5G-RG indicates that the 5G-RG is successfully registered in N1 mode over 3GPP access;

f) the allowed NSSAI or the configured NSSAI is changed; or

g) the LADN information is changed for the 5G-RG.

If the re-evaluation leads to a change of the association of an application to a PDU session, the 5G-RG or the W-AGF acting on behalf of the FN-RG may enforce such change immediately or when the 5G-RG or the W-AGF acting on behalf of the FN-RG returns to 5GMM-IDLE mode.

NOTE 11: The time when the 5G-RG or the W-AGF acting on behalf of the FN-RG enforces the change of the association of an application to a PDU Session is up to implementation of the 5G-RG or the W-AGF acting on behalf of the FN-RG. It is recommended that the 5G-RG or the W-AGF acting on behalf of the FN-RG performs the enforcement in a timely manner.

The URSP handling layer may request the NAS layer of the 5G-RG or the W-AGF acting on behalf of the FN-RG to release an existing PDU session after the re-evaluation.

4.2.3 Unknown or unexpected URSP rules

If the network provides URSP rules including any new component in the traffic descriptor or in the route selection descriptor which is not recognized by the UE, the 5G-RG or the W-AGF acting on behalf of an FN-RG, such URSP rules are unknown or unexpected to the UE, the 5G-RG or the W-AGF acting on behalf of an FN-RG. In this case:

– if the traffic descriptor of this URSP rule includes any component which is not recognized by the UE, the UE shall skip this URSP rule when evaluating the URSP rules to associate an application with a PDU session, with non-seamless non-3GPP offload or with 5G ProSe layer-3 UE-to-network relay offload;

– if the traffic descriptor of this URSP rule includes any component which is not recognized by the 5G-RG or the W-AGF acting on behalf of an FN-RG, the 5G-RG or the W-AGF acting on behalf of an FN-RG shall skip this URSP rule when evaluating the URSP rules to associate an application either with a PDU session;

– if the route selection descriptor of this URSP rule includes any component which is not recognized by the UE, the 5G-RG or the W-AGF acting on behalf of an FN-RG, the UE, the 5G-RG or the W-AGF acting on behalf of an FN-RG shall skip this route selection descriptor and handle this URSP rule with the remaining route selection descriptors.

4.3 Access network discovery and selection policy (ANDSP)

4.3.1 Overview

The ANDSP is used to control the UE behaviour related to access network discovery and selection over non-3GPP access network.

The ANDSP consists of:

– WLAN Selection Policy (WLANSP) which is described in clause 4.3.2.; and

– non-3GPP access network (N3AN) node configuration information which is described in clause 4.3.3.

The 5G-RG or a W-AGF acting on behalf of the FN-RG shall ignore any ANDSP information, if received.

4.3.2 WLAN selection policy (WLANSP)

4.3.2.1 General

The WLANSP is used to control UE behaviour related to selection and reselection of a WLAN.

The WLANSP consists of zero or more WLANSP rules.

Each WLANSP rule consists of:

– rule identifier;

– one or more groups of WLAN selection criteria;

– validity area;

– zero or more time of day;

– rule priority;

– roaming.

Each group of WLAN selection criteria contains:

– criteria priority;

– home network indication;

– preferred roaming partner list;

– min backhaul threshold;

– maximum BSS load value;

– required proto port tuple;

– SP exclusion list; and

– preferred SSID list.

The priority of a selection criteria is encoded in the criteria priority field. The WLAN priority defined in the preferred SSID list (see figure 5.3.2.4c) represents the priority of the WLAN matching the selection criteria.

The validity of the WLANSP rule can be restricted by validity conditions. The validity of the WLANSP rule takes into account validity area, roaming, and time of day where each condition shall match in order to make the WLANSP rule valid.

Each validity area consists of:

– 3GPP location;

– WLAN location; and

– Geo location.

Each time of day consists of:

– time start;

– time stop;

– date start;

– date stop; and

– day of week.

The WLANSP rule is considered valid if none of the validity conditions exist or all validity conditions match.

There can be multiple valid WLANSP rules at the same time. In addition to validity conditions and selection criteria, there is a rule priority that shall be set for each WLANSP rule. The rule priority is encoded in the rule priority field, and it enables the UE to determine which WLANSP rule, out of potentially several valid WLANSP rules, it should consider as active. A WLANSP rule is active if it is valid and has highest rule priority out of the valid WLANSP rules. At any point in time, there shall be at most one active WLANSP rule. A WLAN that matches a selection criteria of the active WLANSP rule is considered as matching the selection criteria.

If the UE is roaming and WLANSP rules from both HPLMN and VPLMN are available, visited WLANSP rules shall take precedence.

4.3.2.2 WLAN access selection

The procedure of UE selecting WLAN access network based on WLAN selection policy is specified in 3GPP TS 24.502 [3].

The 5G-RG and the W-AGF acting on behalf of an FN-RG shall ignore the WLAN selection policy, if received.

4.3.3 N3AN node configuration information

4.3.3.1 General

Non-3GPP access network (N3AN) node configuration information is used to control UE behaviour related to selection of either N3IWF or ePDG for accessing 5GCN or EPC respectively via non-3GPP access.

The non-3GPP access network (N3AN) node configuration information consists of:

– Non-3GPP access network (N3AN) node selection information;

– optionally, home ePDG identifier configuration; and

– optionally, home N3IWF identifier configuration.

4.3.3.2 N3AN node selection

The procedure of UE selecting an N3AN node based on N3AN node configuration information is specified in 3GPP TS 24.502 [3].

4.4 Interworking with EPC

4.4.1 Precedence between URSP, ANDSP, ANDSF and RAN rules

If the UE supports both S1 mode and N1 mode:

– the UE shall always use the ANDSP information and applicable user preferences on non-3GPP access selection, if available at the UE, for non-3GPP access node selection;

NOTE: This includes the case when the UE is registered to the 5GCN via 3GPP access, the case when the UE is registered to the EPC via 3GPP access, and the case when the UE is not registered to any CN via 3GPP access.

– if the UE is:

a) registered to the 5GCN via 3GPP access and not registered to any CN via non-3GPP access; or

b) registered to the 5GCN via 3GPP access and registered to the 5GCN via non-3GPP access,

the UE shall apply URSP rules and applicable UE local configuration, if available at the UE, to all uplink user data;

– if the UE is registered to the 5GCN via 3GPP access and registered to the EPC via non-3GPP access, the UE shall:

a) use the ANDSF rules and RAN rules, if available at the UE, for uplink user data sent via the ePDG; and

b) apply URSP rules and applicable UE local configuration, if available at the UE, to all other uplink user data;

– if the UE is:

a) registered to the EPC via 3GPP access and not registered to any CN via non-3GPP access; or

b) registered to the EPC via 3GPP access and registered to the EPC via non-3GPP access,

the UE:

a) shall use the ANDSF rules and RAN rules, if available at the UE, for all uplink user data for which there is one or more applicable ANDSF rule or RAN rule, except for the rules and parameters related to non-3GPP access node selection; and

b) should use the URSP rules, if available at the UE, to derive the parameters to be used in EPS as specified in clause 4.4.2 for all uplink user data for which there is no applicable ANDSF rule or RAN rule except for the rules and parameters related to non-3GPP access node selection and there is no applicable UE local configuration; and

– if the UE is registered to the EPC via 3GPP access and registered to the 5GCN via non-3GPP access, the UE:

a) shall apply URSP rules and applicable UE local configuration, if available at the UE, to uplink user data sent via the N3IWF;

b) shall use the ANDSF rules and RAN rules, if available at the UE, for all other uplink user data for which there is one or more applicable ANDSF rule or RAN rule, except for the rules and parameters related to non-3GPP access node selection; and

c) should use the URSP rules, if available at the UE, to derive the parameters to be used in EPS as specified in clause 4.4.2 for all uplink user data for which there is no applicable ANDSF rule or RAN rule except for the rules and parameters related to non-3GPP access node selection. and there is no applicable UE local configuration

4.4.2 Use of URSP in EPS

If the UE:

– supports both S1 mode and N1 mode;

– does not have preconfigured rules for associating an application to a PDN connection, a non-seamless non-3GPP offload or a 5G ProSe layer-3 UE-to-network relay offload (i.e. there are no rules in UE local configuration and no ANDSF rules applicable for the application); and

– is provisioned with URSP,

when in S1 mode, the UE should use a matching URSP rule, if available, to derive the parameters, e.g. APN, using the mapping between the parameters in the URSP rules and the parameters used for PDN connection establishment specified in table 4.4.2.1 and table 4.4.2.2. The URSP rule with the derived EPS parameters are used for associating the application to a PDN connection, non-seamless non-3GPP offload or a 5G ProSe layer-3 UE-to-network relay offload, as specified in clause 4.2.2. The precedence of URSP rule is reused in EPS.

If a route selection descriptor for the matching URSP rule includes:

– at least one parameter not applicable in EPS, the UE shall not use the route selection descriptor and shall proceed to evaluate the route selection descriptor with the next lowest precedence value; and

– one or more parameters ignored in EPS, the UE shall evaluate the route selection descriptor without considering the one or more parameters ignored in EPS.

Table 4.4.2.1: Mapping table for traffic descriptor parameters

Traffic descriptor parameter name

Description

Mapped EPS parameter description

Application descriptors

It consists of OSId and OSAppId(s)

OSId and OSAppId(s)

IP descriptors

Destination IP 3 tuple(s) (IP address or IPv6 network prefix, port number, protocol ID of the protocol above IP)

Destination IP 3 tuple(s) (IP address or IPv6 network prefix, port number, protocol ID of the protocol above IP)

Domain descriptors

Destination FQDN(s) or a regular expression as a domain name matching criteria

Destination FQDN(s) or a regular expression as a domain name matching criteria

Non-IP descriptors

Descriptor(s) for destination information of non-IP traffic

Descriptor(s) for destination information of non-IP traffic

DNN

This is matched against the DNN information provided by the application

APN

Connection Capabilities

This is matched against the information provided by a UE application when it requests a network connection with certain capabilities

This is matched against the information provided by a UE application when it requests a network connection with certain capabilities

Table 4.4.2.2: Mapping table for route selection descriptor parameters

Route selection descriptor parameter name

Description

Mapped EPS parameter description

Route selection descriptor precedence

Determines the order in which the route selection descriptors are to be applied

Determines the order in which the route selection descriptors are to be applied

SSC Mode Selection

One single value of SSC mode

Ignored in EPS if set to SSC mode 1

Not applicable in EPS if set to SSC mode 2 or 3

Network Slice Selection

Either a single value or a list of values of S-NSSAI(s)

Not applicable in EPS

DNN Selection

Either a single value or a list of values of DNN(s)

Either a single value or a list of values of APN(s).

Not applicable in EPS if it contains at least one LADN DNN

PDU Session Type Selection

One single value of PDU Session Type

PDN type:

– PDU session type "Unstructured" is mapped to PDN type "non-IP".

– PDU session type "Ethernet" is mapped to PDN type "Ethernet", if supported by the UE. Otherwise PDU session type "Ethernet" is mapped to PDN type "non-IP"

Non-Seamless Offload indication

Indicates if the traffic of the matching application is to be offloaded to non-3GPP access outside of a PDU session

Indicates if the traffic of the matching application is to be offloaded to non-3GPP access outside of a PDN connection

5G ProSe layer-3 UE-to-network relay offload indication

Indicates if the traffic of the matching application is to be offloaded to 5G ProSe layer-3 UE-to-network relay outside of a PDU session

Not applicable in EPS

Access Type preference

Indicates the preferred Access Type (3GPP or non-3GPP) when the UE establishes a PDU Session for the matching application

preferred Access Type (3GPP or non-3GPP)

Multi-Access preference

Indicates that the PDU session should be established as a multi-access PDU session, using both 3GPP access and non-3GPP access.

Not applicable in EPS

Time window

The time window when the matching traffic is allowed.

Not applicable in EPS

Location criteria

The UE location where the matching traffic is allowed.

Not applicable in EPS

PDU session pair ID

One single value of PDU session pair ID for redundant PDU session establishment.

Ignored in EPS

RSN

One single value of RSN for redundant PDU session establishment.

Ignored in EPS