Non-access stratum (NAS) message routing

Abstract

A method performed by a user equipment (UE). The method includes transmitting a first message to a network node of a radio access network (RAN). The first message comprises: a first non-access stratum (NAS) message to be processed by an instance of network function (NF) having a particular NF type, and NF routing information (NFRI) enabling the network node of the RAN to obtain an address of an instance of a NF of the particular NF type. The NFRI does not comprise a NF identifier.

Description

NON-ACCESS STRATUM (NAS) MESSAGE ROUTINGTECHNICAL FIELD

[0001] Disclosed are embodiments related to the routing of non-access stratum (NAS) messages.BACKGROUND

[0002] Non-access stratum messages are used to carry information between the UE and core network (CN) functions, e.g., to manage the establishment of communication sessions and for maintaining continuous communications with a user equipment (UE) as it moves. The access stratum, in contrast, is responsible for carrying information between the UE and the radio access network (RAN) network node (e.g. a base station). A further characteristic of NAS is that it is passed transparently through the RAN. That is, when a base station receives an access stratum message, such as a radio resource control (RRC) message containing a NAS message, the base station merely forwards the NAS message to the core network (CN). Accordingly, NAS messages are passed between the UE and a network function (NF) instances in the CN. In 2G and 3G networks, all NAS messages from a UE are forwarded by the base station to a SGSN. In 4G networks, which is also known as Evolved Packet System (EPS), all NAS messages from a UE are forwarded by the base station to a Mobility Management Entity (MME). An in 5G networks, all NAS messages from a UE are forwarded by the base station to an Access and Mobility Management function (AMF). In 5G, the AMF may transparently relay certain NAS messages to a Session Management Function (SMF). The AMF also interacts with other NFs using information received via NAS or sent via NAS. For example, if the AMF receives from a UE a NAS message comprising a Short Message Service (SMS) message, the AMF forwards the SMS message to a SMS Function (SMSF). As another example, UE policy information is relayed between the UE and a Policy Control Function (PCF). The NAS protocol for the 5G system (5GS) is specified in 3GPP Technical Specification (TS) 24.501 V18.5.0 ("TS 24.501”).

[0003] The Globally Unique Temporary Identity (GUTI)

[0004] In all previous core network generations (GPRS, EPC and 5GC) the mobility management logical function (e.g., MME in EPC and AMF in 5GC) has been responsible for assigning to the UE a globally unique temporary identity. As there was only one mobility management function in the core, only one globally temporary unique (GUTI) was needed.

[0005] The GUTI is described in 3GPP TS 23.003 V18.4.0 ("TS 23.003”). The table below contains an excerpt from TS 23.003.

[0006] The 5G-GUTI is also described in 3GPP TS 33.501 V18.4.0 (“TS 33.501”). The table below contains an excerpt form TS 33.501 .SUMMARY

[0007] Certain challenges presently exist. For instance, forwarding all NAS messages from a UE to a single type of network function (e.g., AMF) is a processing bottleneck, especially if the message or message content is only relayed.

[0008] Accordingly, in one aspect there is provided a method performed by a user equipment, UE. The method includes transmitting a first message to a network node of a radio access network, RAN. The first message comprises a first non-access stratum, NAS, message to be processed by an instance of network function, NF, having a particular NF type. The first message further comprises NF routing information, NFRI, enabling the network node of the RAN to obtain an address of an instance of a NF of the particular NF type. The NFRI does not comprise a NF identifier.

[0009] In another aspect there is provided a UE that is configured to perform the UE methods disclosed herein. The UE may include memory and processing circuitry coupled to the memory. In another aspect there is provided a computer program comprising instructions which when executed by processing circuitry of a UE causesthe UE to perform any of the UE methods disclosed herein. In one embodiment, there is provided a carrier containing the computer program wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer readable storage medium.

[0010] In another aspect there is provided a method performed by a network node of a radio access network, RAN. The method includes receiving from a user equipment, UE, a first message comprising: i) a first non- access stratum, NAS, message to be processed by an instance of network function, NF, having a particular NF type, and ii) NF routing information (NFRI). The method includes using the NFRI to obtain an address of an instance of a NF of the particular NF type. The NFRI does not comprise a NF identifier. The method includes transmitting the first NAS message to the obtained address of the instance of the NF of the particular NF type.

[0011] In another aspect there is provided a network node that is configured to perform the network node methods disclosed herein. The network node may include memory and processing circuitry coupled to the memory. In another aspect there is provided a computer program comprising instructions which when executed by processing circuitry of a network node causes the network node to perform any of the network node methods disclosed herein. In one embodiment, there is provided a carrier containing the computer program wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer readable storage medium.

[0012] An advantage of the embodiments disclosed herein is that they free up resources in the AMF because the AMF (or its equivalent 6G function) need no longer be the middleman between the RAN and the intended consumer of the NAS message (e.g., an SMF).BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments.

[0014] FIG. 1 illustrates a system according to an embodiment.

[0015] FIG. 2 illustrates various protocol stacks used in an embodiment.

[0016] FIG. 3 is a message flow diagram according to an embodiment.

[0017] FIG. 4 is a message flow diagram according to an embodiment.

[0018] FIG. 5 is a message flow diagram according to an embodiment.

[0019] FIG. 6 is a flowchart illustrating a process according to an embodiment.

[0020] FIG. 7 is a flowchart illustrating a process according to an embodiment.

[0021] FIG. 8 is a flowchart illustrating a process according to an embodiment.

[0022] FIG. 9 is a flowchart illustrating a process according to an embodiment.

[0023] FIG. 10 is a flowchart illustrating a process according to an embodiment.

[0024] FIG. 11 is a flowchart illustrating a process according to an embodiment.

[0025] FIG. 12 is a block diagram of UE according to some embodiments.

[0026] FIG. 13 is a block diagram of a network node according to some embodiments.DETAILED DESCRIPTION

[0027] FIG. 1 illustrates a system 100 according to an embodiment. System 100 includes a UE 102, a RAN network node 104 (e.g., a base station), and several instantiated core network NFs, including, for example, as shown NF1 106, NF2 108, NF3 110, and NF4 112. Each NF instance may be of a different NF type, including, for example, an AMF, a NF repository function (NRF), a PCF, a SMF, etc. Other core network NFs may be instantiated as needed and several NFs of the same type can also be instantiated if required, e.g., to distribute load to additional NF(s) of the same type. Thus, an NF instance may be seen as an example or a specimen of a certain NF. Herein, the terms NF and NF instance are used interchangeably, unless otherwise expressly stated or is apparent from the context in which the terms are used. An NF instance exposes one or more NF Service Instances.

[0028] As noted above, in the current 5G system, any NAS message transmitted by UE 102 is received by network node 104 and then forwarded to an instance of an AMF. This architecture creates a bottleneck at both network node 104 and the AMF. This disclosure aims to solve this problem such that when network node 104 receives a NAS message from UE 102, network node 104 can forward the NAS message directly towards the intended NF instance, such as, for example, an NF instance configured to establish PDU sessions for UE 102 and manage these PDU session, thereby by-passing the access control NF instance configured to manage the registration and mobility of UE 102, such as an instance of an AMF.

[0029] FIG. 2 illustrates a protocol stack within UE 102, protocol stacks within network node 104, and a protocol stack within an exemplary NF, NF1 106. The protocol stack within UE 102 may include a NAS layer and an RRC layer. When UE needs to send information to an NF, UE generates a NAS message which is then encapsulated in an RRC message. The physical layer (PHY) of the UE is then responsible for transmitting the RRC message containing the NAS message and RRC information elements over the air so that the RRC message can be received by a PHY layer of network node 104. The RRC layer of the network node extracts the NAS message from the RRC message and then uses, in this example, the next generation application protocol (NGAP) protocol to forward the NAS message to an appropriate NF, which is NF1 in this example.

[0030] In one embodiment, each NAS message has a NAS type and the NAS type is associated with an NF type. For example, the NAS type may be "Access” which may be associated with the NF type "AMF”. As another example, the NAS type may be "Session” which may be associated with the NF type "SMF.”

[0031] In one embodiment, when UE 102 generates an RRC message containing a NAS message, UE 102 may include in the RRC message an information element (IE) containing NF routing information (NFRI) indicating (e.g., specifying) the NAS type of the NAS message. For instance, if the NAS message included in the RRC message is a NAS message used for establishing a session, then the RRC message may include the following name-value-pair: "NAS type = Session”. In one embodiment, network node 104 uses the information included in the RRC message that indicates the NAS type to route the NAS message to the correct type of NF. For example, in one embodiment, network node 104 uses a look-up table, like the one shown below, to map the NAS type indicated in the RRC message to an NF type. That is, given a NAS type, network node 104 can use the look-up table to determine the NF type to which the NAS type is mapped.

[0032] After determining the NF type to which the NAS type is mapped, network node 104 can use the NF type information to obtain an NF profile of an NF instance of the NF type, which NF profile may include the address (e.g., IP address or fully-qualified domain name (FQDN)) for the NF instance. Hence, after obtaining the NF profile of the NF instance, network node can send to the NF instance, that is send to the address for the NF instance, a NGAP message comprising the NAS message.

[0033] In other embodiments, to avoid having to use a look-up table, the NFRI included in the RRC message may include an NF type value instead of an NAS type value, thereby avoiding having to map a NAS type to an NF type.

[0034] FIG. 3 is a message flow diagram illustrating a process according to an embodiment. The process illustrates UE 102 exchanging messages with NF2 108. In this example NF2 108 (or "NF2” for short) is an NF that performs session management functions; hence, NF2 may be an enhanced version of a 5G SMF (a.k.a., eSMF).

[0035] The process may begin with UE 102 transmitting an RRC message m302 to a network node 104. The RRC message may include an IE containing a NAS message and a separate IE containing NFRI, which in this example comprises a NAS type value (e.g., "Session”). The NAS message is intended for a NF associated with the NAS type. In this example, the NAS message is a session establishment request and thus has a NAS type of "Session,” which means that the NAS message should be routed to an NF of type SMF or eSMF or similar. In some embodiments, a NF may register an individual and non-standardized NAS type. Network node 104 may be informed of the new NAS type by an NRF. Specifically, the NFs may register their "NAS type” in the NF profile in a discovery system, e.g., NRF, to be discovered by network node 104.

[0036] In some embodiments, the RRC message m302 may also include a first temporary identifier (TID) that was allocated to UE 102 by NF1 106 (or “NF1” for short). In this example, NF1 is a network function that performs access control functions; hence NF1 may be an enhanced version of a 5G AMF. Because NF1 performs access control functions, the first TID (denoted “TID_1”), which was allocated by NF1 to UE 102 may be referred to herein as an "anchor” or "primary” TID. TID_1 may be a 5G GUTI or an enhanced version of the 5G GUTI. The NFRI included in RRC message m302 may further include network slice selection assistance information (NSSAI) and a data network name (DNN) and / or other information useful in discovering an instance of an NF.

[0037] After receiving RRC message m302, the network node 104 determines an NF type value (e.g., "SMF”) based on the NAS type value included in RRC message m302. For example, as described above, a look-up table can be used for this purpose.

[0038] In one embodiment, after determining the NF type value, network node 104 may transmit to NRF 305 a discovery request message m304. The discovery request message may include the NF type value, the NSSAI, and the DNN.

[0039] After receiving request m304, NRF 305 may transmit a discovery result message m306 to network node 104. The discovery result message may include an NF profile of an NF having the NF type, such as NF2 and otherwise matching the query included in the discovery request message.

[0040] In another embodiment, rather than send the discovery request to NRF 305, network node 104 may send to the NF associated with TID_1, which in this case is NF1, an NF discovery request comprising the determined NF type value. Network node 104 may then be informed by the NF1 which NF to use for NAS message purposes. In such embodiments, the NF1 may be aware of each NF used for NAS messages.

[0041] After receiving the address of NF2, network node 104 may transmit to NF2 an N2 message (e.g. NGAP message) m308 containing the NAS message. The NAS message may comprise the first temporary identifier (TID_1).

[0042] After receiving the N2 message m308, NF2 obtains the address of the access control function that allocated to UE 102 the first temporary identifier (TID_1 ), which in this case is NF1, and transmits to NF1 a TID validation request message m312. The verification message may include the first temporary identifier and requests NF1 to verify that the first temporary identifier is valid. In one embodiment, NF2 obtains the address of NF1 using TID_1, which includes, among other things, an identifier identifying NF1.

[0043] After verifying TID_1, NF1 transmits to NF2 a response message m314 verifying the validity of the first temporary identifier. In some embodiments, the response message may include a subscription permanent identifier (SUPI) associated with the first temporary identifier and NF2 stores the SUPI together with the first temporary identifier. After receiving the response message, NF2 may allocate a second TID (TID_2) to UE 102. NF2 may link TID_1 and TID_2 together. For example, NF2 may store in a database a record comprising TID_1 and TID_2. Because NF2 in this example does not perform access control function, but rather session management function, the TID allocated by NF2 to UE 102 may be referred to herein as a "supplemental” or "secondary” TID.

[0044] A supplemental TID may also be referred to as a 6G-NUTI and may be defined as shown in the table below.8 7 6 5 4 3 2 1 octet 1 octet 2 octet 3 octet 4 octet 5 octet 6 octet 7 octet 8 octet 9 octet 10 octet 11 octet 12octet 13

[0045] The table below describes the security specification (33.501) that may specify the new additional NF specific identity. The 6G-NUTI mentioned in the table below may be like the 5G-GUTI.

[0046] In addition, the table below describes how the new 6G-NUTI and 6G-TNUI values may be included in the 23.003 specification.

[0047] Referring back to FIG. 3, after allocating TID_2 to UE 102, NF2 may transmit to NF1 a TID notification message m316 comprising the TID_1 and TID_2. The TID notification message may instruct NF1 to link together the first and second temporary identifiers. This will link together UE 102, which is associated with the first temporary identifier, and NF2, which is associated with the second temporary identifier. In some embodiments, UE 102 may be linked together with multiple NFs, each of which may have a unique temporary identifier. Each NF andNF1 may keep an updated list of the existing links.

[0048] In one embodiment, NF2 may generate TID_2 before sending TID validation request message m312 and the TID validation request message may include TID_2. In this embodiment, TID notification message m316 is not necessary as NF1 is already aware of the second temporary identifier.

[0049] As also shown in FIG. 3, after determining that TID_1 is valid, NF2 transmits to network node 104 a response message m318. The response message m318 in this example is an N2 message comprising i) a NAS message that is responsive to the NAS message transmitted by UE 102 and ii) separately comprising TID_2. More specifically, in this example, the responsive NAS message transmitted by NF2 is a PDU Session Establishment Accept message, and the response NAS message also includes TID_2.

[0050] After receiving message m318, network node 104 extracts the NAS message from message 318, includes the NAS message in an RRC message m320, and transmits the RRC message containing the NAS message to UE 102. Additionally, network node 104 stores TID_2 together with the address of NF2. In some embodiments, RRC message also includes a NAS type value separate from the NAS message and indicates the NAS type of the NAS message included in the RRC message. At step s322, UE 102 may link a UE generated session ID (e.g., a PDU Session ID) with TID_2. For example, in the case where the NAS message sent by the UE is a PDU Session Establishment request, the NAS message sent by the UE includes a PDU Session ID selected by the UE, and when the UE receives the PDU Session Establishment accept message transmitted by NF2, the UE will link the PDU Session ID with TID_2. In some embodiments, UE 102 may have multiple sessions simultaneously and UE 102 may separate the sessions internally, for example, by linking the generated session ID with TID_2.

[0051] In some embodiments, network node 104 may receive NAS related messages from different NFs and may add the same NS type values as listed above, e.g., session, location, before sending the NAS messages to UE 102. Network node 104 may support different scheduling policies per NAS message, i.e., may schedule the sending of mobility related messages with higher priority than SMS related messages. There may be further differentiation between messages, e.g., SMS related messages with lower or higher priority.

[0052] FIG. 4 is a message flow diagram illustrating UE 102 communicating with NF2 108. More specifically, in the example shown, UE 102 is attempting to modify a previously established PDU session managed by NF2.

[0053] The process may begin with UE 102 transmitting an RRC message m402 to network node 104. The RRC message may include an IE containing the second temporary identifier (TID_2) and a separate IE containing a NAS message. In this example, the NAS message is a PDU session modification request comprising the second temporary identifier. The NAS message is intended for NF2 108 and UE 102 causes network node 104 to send the NAS message to NF2 by including the second temporary identifier in RRC message m402. In someembodiments, RRC message m402 also includes a separate IE containing a NAS type value (e.g., "Session”). Here, the NAS type may be set, e.g., to Session.

[0054] After receiving RRC message m402, network node 104 determines s404 an NF instance based on the second temporary identifier included in the RRC message m402. For example, a look-up table can be used for this purpose that maps TID_2 to an address of an NF instance. In the present embodiment, the NF instance associated with the second temporary identifier is NF2 108. After identifying NF2, network node 104 sends a N2 message m406 to NF2. N2 message m406 comprises the NAS message.

[0055] After receiving message m406, NF2 108 may, in step s408, allocate a third temporary identifier, TID_3, to UE 102. In some embodiments, NF2 may replace s410 the second temporary identifier (TID_2) with the third temporary identifier (Tl D_3). Here, NF2 may replace the link between the first and second temporary identifiers with a link between the first and third temporary identifiers. For example, NF2 may store in a database a record comprising TID_1 and TID_3. In such embodiments, NF2 may transmit an update message m412 to NF1 comprising the Tl D_1 and Tl D_3. The linking message may instruct NF1 to link together the first and third temporary identifiers. This will link together UE 102, which is associated with the first temporary identifier, and NF2, which is associated with the third temporary identifier.

[0056] After allocating the temporary identifier, NF2 transmits to network node 104 a response message m414. Response message m414 in this example is a N2 message comprising I) a NAS message that is responsive to the NAS message transmitted by UE 102 and ii) separately comprising TID_3. More specifically, in this example, the responsive NAS message transmitted by NF2 is a PDU Session Modification Accept message, and the response NAS message also includes Tl D_3.

[0057] After receiving message m414, network node 104 extracts the NAS message from message m414, includes the NAS message in an RRC message m416, and transmits the RRC message containing the NAS message to UE 102. Additionally, network node 104 stores Tl D_3 together with the address of NF2. In some embodiments, RRC message also includes a NAS type value separate from the NAS message and indicates the NAS type of the NAS message included in the RRC message. At step s418, UE 102 may link the above described session ID with Tl D_3 and unlink the session ID with Tl D_2 because Tl D_3 has now replaced TID_2.

[0058] FIG. 5 is a message flow diagram illustrating a handover process according to an embodiment. The process illustrates a handover from a source RAN 501 to a target RAN 503 for a UE.

[0059] The process may begin with source RAN 501 transmitting a handover required message m502 to NF1 106. Source RAN 501 may transmit the handover required message m502 in response to deciding to trigger a relocation. The handover required may include a target identifier, a N2 information list, a PDU session identifier, an intra system handover indication, and / or an inter system handover indication.

[0060] After receiving handover required message m502, NF1 106, in step s504, may discover NF3 110 using the information included in the handover required. In this example, NF3 110 (or "NF3” for short) is a network function that, like NF1, performs access control functions; hence NF3 may be an enhanced version of a 5G AMF. In some embodiments, the discovery process may include NF1 transmitting a discovery request message to an NRF. The NRF may respond with an NF profile of NF3 and feature capabilities. The feature capabilities may allow NF1 106 to determine whether NF3 110 is an evolved NF or legacy NF. A NF Profile, used in a registration procedure towards the NRF, should be updated with an indication of if this capability is supported or not.

[0061] With a legacy NF, all NAS messages to and from a RAN may be passed through an AMF. The AMF may only handle a temporary ID assignment. Here, the AMF may be unaware of any NAS message paths that are in use that are not passing the AMF itself. The legacy NF supports 5GS only from a connectivity perspective.

[0062] With an evolved NF, NAS messages may be sent directly between a RAN and an affected NF, e.g., between a RAN and a PCF, without being passed through an AMF. All affected NFs may, especially if stateful, handle their respective temporary ID assignment. Here, the AMF is aware of all NAS message paths that are in use. The evolved NF supports 5GS and 6GS from a connectivity perspective.

[0063] In some embodiments (e.g., embodiments in which the target NF is an MME or a legacy AMF), in step s506, NF1 106 obtains a complete UE context. First, NF1 106 may retrieve TIDs linked with TID_1. For example, NF1 106 may keep track of a linked identifiers, e.g., 6G-GUTI, 6G-NUTI, NFType, optionally PDU Session ID. For example, TID_1, which NF1 previously allocated to UE 102, may be linked with a first n-tuple comprising a TID allocated by NF2 (e.g. TID_2) and an NF type value indicating NF2's NF type, a second n-tuple comprising a TID allocated by NF3 and an NF type value indicating NF3's NF type, and a third n-tuple comprising a TID allocated by NF4 and an NF type value indicating NF2's NF type. For instance, the table below shows a list of four 2-tuples that may be linked with TID_1, where each 2-tuple, i.e., each row of the table, includes an NF type value and a TID.

[0064] For each of the TIDs linked with TID_1, NF1 106 may transmit a Get UE Context Request message to the NF identified by the TID with the corresponding TID. In response, each NF may transmit to NF1 106a Get UE Context Response message comprising UE context associated with the TID. NF1 106 may build the complete UE context with these responses.

[0065] NF1 106 transmits to NF3 110 a create UE context request message m508 comprising the list of TIDs linked with TID_1 and / or the complete UE context. Message m508 may comprise the list of TIDs linked with TID_1 when the message is transmitted to an evolved AMF and may comprise the complete UE context when the message is transmitted to an MME or legacy AMF.

[0066] In embodiments including mobility inside 6G (using evolved 5GC), NF1 106 may send the TID list to NF3 110, e.g, via an extended N14 interface, between source AMF and targetAMF in legacy 5GC, together with the full UE Context.

[0067] In embodiments including mobility between 6G (using evolved 5GC) and 5G (using legacy 5GC), NF1 106 may collect the data, UE Context, from all other NF controlling participants in the UE Context and build the message compliant to the legacy N14 interface.

[0068] In embodiments including mobility between 6G (using evolved 5GC) and 4G (using legacy EPC), NF1 106 may collect the data, UE Context, from all other NF controlling participants in the UE Context and build the message compliant to the legacy N26 interface.

[0069] After receiving request message m508, NF3 110 may transmit to NF2 108 an update SM context request message m510. The update SM context request message m510 may include an IE containing the TID that NF2 allocated to the UE and a second IE containing an identifier identifying NF3. After receiving message m510, NF2 108 may transmit a response message m512. The response message m512 may include the TID that NF2 originally allocated to the UE or a new TID allocated by NF2 to the UE that replaces the previous TID that NF2 allocated to the UE.

[0070] NF3 110 may transmit a handover request message m514 to target RAN 503 which may respond with an acknowledgement (ACK) message m515. After receiving the ACK from the target RAN, NF3 110 may transmit a create UE context response m516 to NF1 106.

[0071] NF3 110 also transmits an update SM context request message m518 to NF2. In some embodiments, NF3 may allocate a TID to the UE and this TID, which may be a 5G-GUTI or other GUTI, is included in message m518 sent to NF2. NF2 may respond with a response message m520, which includes the TID (e.g., NUTI) that was included in message m512. In some embodiments, UE context information may be obtained from one or more other NF instances. Because in this example NF3, like NF1 is a NF that performs access control function, the TID allocated by NF3 to UE 102 is an anchor TID.

[0072] As noted above, in some embodiments, NF3 110 may assign a TID to the UE, for example, during mobility inside 6G (using evolved 5GC). The TID may be a GUTI. NF3 110 may then link the received identifiers, e.g., 6G-NUTI, NFType, optionally PDU Session ID, with the TID allocated by NF3. NF3 110 may then transmit this TID that it allocated to the UE to the NFs linked with the UE, e.g., to each NF identified by a TID included in the list of TIDs that was included in message m508. As an example, as shown in FIG. 5, NF3 may transmit to NF4 112 an update UE context request message m522 comprising the anchor TID NF3 allocated to the UE, and this message m522 may also include the supplementary TID that NF4 allocated to the UE (this TID allocated by NF4 is included in the list of TIDs NF3 received from NF2). NF4 then sends to NF3 a response message m524. If NF4 allocated a new supplemental TID to the UE to replace the supplemental TID that NF4 had previously allocated to the UE, then response message m524 includes the new supplemental TID allocated by NF4 to the UE. In some embodiments, the NF's linked with the UE may include both legacy and evolved NFs. Here, NF3 110 may keep track of the receiver NFs capabilities and adapt its behavior accordingly, e.g., either send pointers and / or send the data.

[0073] FIG. 6 is a flowchart illustrating a process 600, according to an embodiment, performed by a UE.

[0074] Process 600 may begin with s602. Step s602 comprises transmitting a first message to a network node of a RAN (e.g., network node 104). The first message comprises: a first NAS message to be processed by an instance of NF having a particular NF type, and NF routing information (NFRI) enabling the network node of the RAN to obtain an address of an instance of a NF of the particular NF type. The NFRI does not comprise a NF identifier.

[0075] In some embodiments, the NFRI comprises a type value and the type value is a NF type value specifying the particular NF type, or a NAS message type value to which the particular NF type is mapped.

[0076] In some embodiments, process 600 further comprises receiving a second NAS message. The second NAS message was generated by the instance of the NF. The second NAS message comprises a temporary identifier allocated to the UE by the instance of the NF.

[0077] In some embodiments, process 600 further comprises transmitting a second message to the network node. The second message comprises: a third NAS message to be processed by the instance of the NF, and the temporary identifier allocated to the UE by the instance of the NF.

[0078] In some embodiments, the first message is a radio resource control, RRC, message, the first NAS message is included in a first IE of the RRC message, and the type value is included in a second IE of the RRC message.

[0079] In some embodiments, the NFRI further comprises: single network slice selection assistance information, S-NSSAI, and a DNN.

[0080] In some embodiments, the instance of the NF is an instance of a session management function (e.g., any function that is designed to manage UE sessions).

[0081] In some embodiments, the session management function is a 6G session management function.

[0082] In some embodiments, the first NAS message is a PDU session establishment request.

[0083] In some embodiments, the first NAS message comprises a PDU session identifier, and process600 further comprises linking the temporary identifier with the PDU session identifier.

[0084] FIG. 7 is a flowchart illustrating a process 700, according to an embodiment, performed by a network node of a RAN.

[0085] Process 700 may begin with s702. Step s702 comprises receiving from a UE (e.g., UE 102) a first message comprising: i) a NAS message to be processed by an instance of NF having a particular NF type, and ii) NFRI. Step s704 comprises using the NFRI to obtain an address of an instance of a NF of the particular NF type. The NFRI does not comprise a NF identifier. Step s706 comprises transmitting the first NAS message to the obtained address of the instance of the NF of the particular NF type.

[0086] In some embodiments, the NFRI comprises a type value and the type value is: a NF type value specifying the particular NF type, or a NAS message type value to which the particular NF type is mapped.

[0087] In some embodiments, process 700 further comprises receiving a second message from the instance of the NF, and the second message received from the instance of the NF comprises a temporary identifier allocated to the UE by the instance of the NF.

[0088] In some embodiments, process 700 further receiving a third message transmitted by the UE, wherein the third message comprises a second NAS message to be processed by the instance of the NF and the temporary identifier allocated to the UE by the instance of the NF; using the temporary identifier to obtain the address of the instance of the NF; and transmitting the second NAS message to the address obtained using the temporary identifier.

[0089] In some embodiments, the first message is a RRC message, the first NAS message is included in a first IE of the RRC message, and the type value is included in a second IE of the RRC message.

[0090] In some embodiments, the NFRI further comprises: a S-NSSAI, and a DNN.

[0091] In some embodiments, using the NFRI to obtain the address comprises transmitting a discovery request comprising the NFRI, and process 700 comprises receiving a discovery response responsive to the discovery request, the discovery response comprising the address or information enabling the network node to obtain the address.

[0092] In some embodiments, the instance of the NF is an instance of a session management function,SMF.

[0093] In some embodiments, the first NAS message is a PDU session establishment request.

[0094] FIG. 8 is a flowchart illustrating a process 800, according to an embodiment, performed by a first instance of a second NF type.

[0095] Process 800 may begin with s802. Step s802 comprises receiving from a network node of a RAN a first NAS message comprising a first TID allocated to a UE by a first instance of a first NF type. The first NF type is different than the second NF type. Step s804 comprises determining whether the first TID is valid. Step s806 comprises allocating a second TID to the UE. Step s808 comprises, after determining that the first TID is valid, transmitting to the UE a second NAS message responsive to the first NAS message. The second NAS message comprises the second TID.

[0096] In some embodiments, the first TID is an anchor TID (e.g., a GUTI), the second TID is a supplementary TID (e.g., a NUTI), and process 800 further comprising linking the supplementary TID with the anchor TID.

[0097] In some embodiments, the first NAS message is a request for establishing a PDU session.

[0098] In some embodiments, transmitting the second NAS message to the UE comprises transmitting to the network node of the RAN a message comprising a first IE comprising the second TID and a second IE comprising the second NAS message.

[0099] In some embodiments, determining whether the first TID is valid comprises: transmitting to the first instance of the first NF type a TID validation request message comprising the first TID; and receiving from the first instance of the first NF type a TID validation response message, wherein, if the first TID is valid the TID validation response message comprises a subscription identifier (e.g., a 5G SUPI) associated with the first TID.[000100] In some embodiments, the verification request message further comprises the second TID.[000101] In some embodiments, the second TID is allocated to the UE after determining that the first TID is valid, and process 800 further comprises, after allocating the second TID to the UE, transmitting to the first instance of the first NF type a TID notification message comprising the first TID and the second TID to enable the first instance of the first NF type to link the second TID with the first TID.[000102] In some embodiments, process 800 further comprises associating the second TID with the firstTID.[000103] In some embodiments, process 800 further comprises: receiving a third NAS message comprising the second TID; allocating a third TID to replace the second TID; and transmitting to the network node of the RAN a message comprising a first IE comprising the third TID and a second IE comprising the fourth NAS message responsive to the third NAS message and comprising the third TID.[000104] In some embodiments, process 800 further comprises transmitting to the first instance of the first NF type a TID update message comprising the second TID and the third TID, thereby enabling the first instance of the first NF type to replace the second TID with the third TID.[000105] FIG. 9 is a flowchart illustrating a process 900, according to an embodiment, performed by a first NF.[000106] Process 900 may begin with s902. Step s902 comprises allocating a first TID to a UE. Step s904 comprises receiving from a second NF a TID validation request message comprising the first TID. Step s906 comprises, in response to receiving the TID validation request message, determining whether the first TID is valid. Step s908 comprises, after determining that the first TID is valid, sending to the second NF a TID validation response message responsive to the TID validation request message. The TID validation response message comprises a subscription identifier to which the first TID is linked.[000107] In some embodiments, the request message further comprises a second TID obtained by the second NF, and process 900 further comprises, linking the second TID with the first TID if the first TID is valid.[000108] In some embodiments, process 900 further comprises, after sending the TID validation response message to the second NF, receiving from the second NF a TID notification message comprising a second TID allocated to the UE by the second NF and linking the second TID with the first TID.[000109] In some embodiments, the first TID is an anchor TID, and the second TID is a supplemental TID.[000110] In some embodiments, the first NF is configured to perform access control functions, and the second NF is configured to perform session management functions.[000111] In some embodiments, process 900 the method further comprises: prior to allocating the first TID to the UE, receiving a first NAS message transmitted by the UE; and after receiving the NAS message, authenticating the UE; and after authenticating the UE, transmitting to the UE a second NAS message comprising the first TID, wherein the first TID is allocated to the UE after the UE is authenticated.[000112] In some embodiments, the first NAS message is a registration request message, and the second NAS message is a registration accept message.[000113] In some embodiments, determining whether the first TID is valid comprises determining whether the first TID is included in a set of allocated TIDs.[000114] FIG. 10 is a flowchart illustrating a process 1000, according to an embodiment, performed by a source NF.[000115] Process 1000 may begin with s1002. Step s1002 comprises receiving a handover message for handing over a UE to a target NF. Step s1004 comprises, after receiving the handover message, transmitting a create context message to the target NF. The create context message comprises: i) complete UE context information comprising source UE context information maintained by the source NF, first UE context information maintained by a first NF, and second UE context information maintained by a second NF, wherein the first NF is configured to perform session management functions and the second NF is not configured to perform session management functions; and / or ii) an identity list comprising a first temporary identifier, TID, allocated by the first NF to the UE.[000116] In some embodiments, the create context message comprises the complete UE context information, and process 1000 further comprises obtaining the complete UE context information after receiving the handover message.[000117] In some embodiments, obtaining the complete UE context information comprises: transmitting to the first NF a first context request message; receiving from the first NF a first context response message responsive to the first context request message, wherein the first context response message comprises the first UE context information maintained by the first NF; transmitting to the second NF a second context request message; and receiving from the second NF a second context response message responsive to the second context request message, wherein the second context response message comprises the second UE context information maintained by the second NF.[000118] In some embodiments, the first context request message comprises the first TID, thereby providing information to the first NF enabling the first NF to retrieve the first UE context information maintained by the first NF, and the second context request message comprises a second TID allocated by the second NF to the UE, thereby providing information to the second NF enabling the second NF to retrieve the second UE context information maintained by the second NF.[000119] In some embodiments, the create context message comprises the identity list, and the identity list comprises a first information element comprising the first TID allocated by the first NF and an NF type value specifying an NF type of the first NF.[000120] In some embodiments, the identity list further comprises a second information element comprising a second TID allocated by a second NF and an NF type value specifying an NF type of the second NF.[000121] In some embodiments, process 1000 further comprises transmitting to the first NF a PDU session context request comprising the first TID.[000122] FIG. 11 is a flowchart illustrating a process 1100, according to an embodiment, performed by a target NF (e.g., an NF that performs access and / or mobility management functions).[000123] Process 1100 may begin with s1102. Step s1102 comprises receiving from a source NF a create context message related to a handover of a user equipment. The create context message comprises an identity list comprising a first TID allocated by a first NF to the UE, for example, the TID may be a supplemental TID allocated by NF2 to the UE. The first NF is different than the source NF. Step s1104 comprises allocating a second TID to the UE, such as, for example, an anchor TID. Step s1106 comprises transmitting to the first NF a first update message comprising the second TID allocated by the target NF to the UE.[000124] In some embodiments, process 1100 further comprises associating the identity list with the second TID allocated by the target NF to the UE.[000125] In some embodiments, the first update message further comprises the first TID allocated by the first NF to the UE.[000126] In some embodiments, the identity list further comprises a third TID allocated by a second NF to the UE, and process 1100 further comprises transmitting to the second NF (e.g., a NF configured to perform policy management functions, like a 5G PCF) a second update message comprising the second TID allocated by the target NF to the UE.[000127] In some embodiments, the target NF is a target access and mobility management function, and the first NF is a session management function.[000128] FIG. 12 is a block diagram of UE 102, according to some embodiments. As shown in FIG. 12, UE 102 may comprise: processing circuitry (PC) 1202, which comprises one or more processors (P) 1255 (e.g., one or more general purpose microprocessors and / or one or more other processors, such as an application specific integrated circuit (ASIC), field-programmable gate arrays (FPGAs), and the like); communication circuitry 1248, which is coupled to an antenna arrangement 1249 comprising one or more antennas and which comprises a transmitter (Tx) 1245 and a receiver (Rx) 1247 for enabling UE 102 to transmit data and receive data (e.g., wirelessly transmit / receive data); and a storage unit (a.k.a., "data storage system”) 1208, which may include one or more nonvolatile storage devices and / or one or more volatile storage devices. In embodiments where PC 1202 includes a programmable processor, a computer readable storage medium (CRSM) 1242 may be provided. CRSM 1242 may store a computer program (CP) 1243 comprising computer readable instructions (CRI) 1244. CRSM 1242 may be a non-transitory computer readable medium, such as, magnetic media (e.g., a hard disk), optical media, memorydevices (e.g., random access memory, flash memory), and the like. In some embodiments, the CRI 1244 of computer program 1243 is configured such that when executed by PC 1202, the CRI causes UE 102 to perform steps described herein (e.g., steps described herein with reference to the flow charts). In other embodiments, UE 102 may be configured to perform steps described herein without the need for code. That is, for example, PC 1202 may consist merely of one or more ASICs. Hence, the features of the embodiments described herein may be implemented in hardware and / or software.[000129] FIG. 13 is a block diagram of a network node 1300, according to some embodiments, which can be used to implement any of the NFs described herein. In embodiments where an NF consists of software, network node 1300 may run (or execute a virtual machine that runs) the NF. As shown in FIG. 13, network node 1300 may comprise: processing circuitry (PC) 1302, which comprises one or more processors (P) 1355 (e.g., one or more general purpose microprocessors and / or one or more other processors, such as an application specific integrated circuit (ASIC), field-programmable gate arrays (FPGAs), and the like), which processors may be co-located in a single housing or in a single data center or may be geographically distributed (e.g., network node 1300 may be a distributed, cloud computing system comprising two or more computers or a monolithic computing system consisting of a single computer); at least one network interface 1348 (e.g., a physical interface or air interface) comprising a transmitter (Tx) 1345 and a receiver (Rx) 1347 for enabling network node 1300 to transmit data to and receive data from other nodes connected to network 110 (e.g., an Internet Protocol (IP) network) to which network interface 1348 is connected (physically or wirelessly) (e.g., network interface 1348 may be coupled to an antenna arrangement comprising one or more antennas for enabling network node 1300 to wirelessly transmit / receive data); and a storage unit (a.k.a., "data storage system”) 1308, which may include one or more non-volatile storage devices and / or one or more volatile storage devices. In embodiments where PC 1302 includes a programmable processor, a computer readable storage medium (CRSM) 1342 may be provided. CRSM 1342 may store a computer program (CP) 1343 comprising computer readable instructions (CRI) 1344. CRSM 1342 may be a non-transitory computer readable medium, such as, magnetic media (e.g., a hard disk), optical media, memory devices (e.g., random access memory, flash memory), and the like. In some embodiments, the CRI 1344 of computer program 1343 is configured such that when executed by PC 1302, the CRI causes network node 1300 to perform steps described herein (e.g., steps described herein with reference to the flow charts). In other embodiments, network node 1300 may be configured to perform steps described herein without the need for code. That is, for example, PC 1302 may consist merely of one or more ASICs. Hence, the features of the embodiments described herein may be implemented in hardware and / or software.[000130] Summary of Various Embodiments[000131] A1. A method performed by a user equipment, UE, the method comprising: transmitting a first message to a network node of a radio access network, RAN, wherein the first message comprises: a first non-accessstratum, NAS, message to be processed by an instance of network function, NF, having a particular NF type, and NF routing information, NFRI, enabling the network node of the RAN to obtain an address of an instance of a NF of the particular NF type, and further wherein the NFRI does not comprise a NF identifier.[000132] A2. The method of claim A1, wherein the NFRI comprises a type value and the type value is: a NF type value specifying the particular NF type, or a NAS message type value to which the particular NF type is mapped.[000133] A3. The method of claim A1 or A2, wherein the method further comprises receiving a second NAS message, the second NAS message was generated by the instance of the NF, and the second NAS message comprises a temporary identifier allocated to the UE by the instance of the NF.[000134] A4. The method of claim A3, wherein the method further comprises transmitting a second message to the network node, wherein the second message comprises: a third NAS message to be processed by the instance of the NF, and the temporary identifier allocated to the UE by the instance of the NF.[000135] A5. The method of any one of claims A2-A4, wherein the first message is a radio resource control,RRC, message, the first NAS message is included in a first information element, IE, of the RRC message, and the type value is included in a second IE of the RRC message.[000136] A6. The method of any one of claims A2-A5, wherein the NFRI further comprises: single network slice selection assistance information, S-NSSAI, and a data network name, DNN.[000137] A7. The method of any one of claims A1-A6, wherein the instance of the NF is an instance of a session management function (e.g., any function that is designed to manage UE sessions).[000138] A8. The method of claim A7, wherein the session management function is a 6G session management function.[000139] A9. The method of claim A7 or A8, wherein the first NAS message is a PDU session establishment request.[000140] A10. The method of claim A3 or A4, the first NAS message comprises a PDU session identifier, and the method further comprises linking the temporary identifier with the PDU session identifier.[000141] B1. A method performed by a network node of a radio access network, RAN, the method comprising: receiving from a user equipment, UE, a first message comprising: I) a first non-access stratum, NAS, message to be processed by an instance of network function, NF, having a particular NF type, and ii) NF routing information (NFRI); using the NFRI to obtain an address of an instance of a NF of the particular NF type, wherein the NFRI does not comprise a NF identifier; and transmitting the first NAS message to the obtained address of the instance of the NF of the particular NF type.[000142] B2. The method of claim B1, wherein the NFRI comprises a type value and the type value is: a NF type value specifying the particular NF type, or a NAS message type value to which the particular NF type is mapped.[000143] B3. The method of claim B1 or B2, wherein the method further comprises receiving a second message from the instance of the NF, and the second message received from the instance of the NF comprises a temporary identifier allocated to the UE by the instance of the NF.[000144] B4. The method of claim B3, wherein the method further comprises: receiving a third message transmitted by the UE, wherein the third message comprises a second NAS message to be processed by the instance of the NF and the temporary identifier allocated to the UE by the instance of the NF; using the temporary identifier to obtain the address of the instance of the NF; and transmitting the second NAS message to the address obtained using the temporary identifier.[000145] B5. The method of any one of claims B2-B4, wherein the first message is a radio resource control,RRC, message, the first NAS message is included in a first information element, IE, of the RRC message, and the type value is included in a second IE of the RRC message.[000146] B6. The method of any one of claims B2-B5, wherein the NFRI further comprises: single network slice selection assistance information, S-NSSAI, and a data network name, DNN.[000147] B7. The method of any one of claims B1-B6, wherein using the NFRI to obtain the address comprises transmitting a discovery request comprising the NFRI, and the method comprises receiving a discovery response responsive to the discovery request, the discovery response comprising the address or information enabling the network node to obtain the address.[000148] B8. The method of any one of claims B1-B6, wherein the instance of the NF is an instance of a session management function, SMF.[000149] B9. The method of claim B7, wherein the first NAS message is a PDU session establishment request.[000150] C1. A method performed by a first instance of a second network function, NF, type, the method comprising: receiving from a network node of a radio access network, RAN, a first non-access stratum (NAS) message comprising a first temporary identifier, TID, allocated to a user equipment, UE by a first instance of a first NF type, wherein the first NF type is different than the second NF type; determining whether the first TID is valid; allocating a second TID to the UE; and after determining that the first TID is valid, transmitting to the UE a second NAS message responsive to the first NAS message, wherein the second NAS message comprises the second TID.[000151] C2. The method of claim C1, wherein the first TID is an anchor TID (e.g., a GUTI), the second TID is a supplementary TID (e.g., a NUTI), and the method further comprising linking the supplementary TID with the anchor TID.[000152] C3. The method of claim C1 or C2, wherein the first NAS message is a request for establishing aPDU session.[000153] C4. The method of any one of claims C1-C3, wherein transmitting the second NAS message to theUE comprises transmitting to the network node of the RAN a message comprising a first information element, IE, comprising the second TID and a second IE comprising the second NAS message.[000154] C5. The method of any one of claims C1-C4, wherein determining whether the first TID is valid comprises: transmitting to the first instance of the first NF type a TID validation request message (m312) comprising the first TID; and receiving from the first instance of the first NF type a TID validation response message (m314), wherein, if the first TID is valid the TID validation response message comprises a subscription identifier (e.g., a 5G SUPI) associated with the first TID.[000155] C6. The method of claim C5, wherein the verification request message further comprises the second TID.[000156] C7. The method of any one of claims C1-C5, wherein the second TID is allocated to the UE after determining that the first TID is valid, and the method further comprises, after allocating the second TID to the UE, transmitting to the first instance of the first NF type a TID notification message (m316) comprising the first TID and the second TID to enable the first instance of the first NF type to link the second TID with the first TID.[000157] C8. The method of any one of claims C1-C7, wherein the method further comprises associating the second TID with the first TID.[000158] C9. The method of any one of claims C1-C8, wherein the method further comprises: receiving a third NAS message comprising the second TID; allocating a third TID to replace the second TID; and transmitting to the network node of the RAN a message comprising a first IE comprising the third TID and a second IE comprising the fourth NAS message responsive to the third NAS message and comprising the third TID.[000159] C10. The method of claim C9, further comprising: transmitting to the first instance of the first NF type a TID update message comprising the second TID and the third TID, thereby enabling the first instance of the first NF type to replace the second TID with the third TID.[000160] D1. A method performed by a first network function, NF (106, 110), the method comprising: allocating (sx02) a first temporary identifier, TID, to a user equipment, UE (102); receiving (sx04) from a second NF (108, 112) a TID validation request message (m312) comprising the first TID; in response to receiving the TID1 validation request message, determining whether the first TID is valid; after determining that the first TID is valid, sending to the second NF a TID validation response message (m314) responsive to the TID validation request message, wherein the TID validation response message comprises a subscription identifier to which the first TID is linked.[000161] D2. The method of claim D1, wherein the request message further comprise a second TID obtained by the second NF, and the method further comprises, linking the second TID with the first TID if the first TID is valid.[000162] D3. The method of claim D1, wherein the method further comprises, after sending the TID validation response message to the second NF, receiving from the second NF a TID notification message (m316) comprising a second TID allocated to the UE by the second NF and linking the second TID with the first TID.[000163] D4. The method of claim D2 or D3, wherein the first TID is an anchor TID, and the second TID is a supplemental TID.[000164] D5. The method of any one of claims D1-D4, wherein the first NF is configured to perform access control functions, and the second NF is configured to perform session management functions.[000165] D6. The method of any one of claims D1-D4, wherein the method further comprises: prior to allocating the first TID to the UE, receiving a first non-access stratum (NAS) message transmitted by the UE; and after receiving the NAS message, authenticating the UE; and after authenticating the UE, transmitting to the UE a second NAS message comprising the first TID, wherein the first TID is allocated to the UE after the UE is authenticated.[000166] D7. The method of claim D6, wherein the first NAS message is a registration request message, and the second NAS message is a registration accept message.[000167] D8. The method of any one of claims D1-D7, wherein determining whether the first TID is valid comprises determining whether the first TID is included in a set of allocated TIDs.[000168] E1. A method performed by a source network function, NF, the method comprising: receiving a handover message for handing over a user equipment to a target NF; after receiving the handover message, transmitting a create context message to the target NF, wherein the create context message comprises: I) complete UE context information comprising source UE context information maintained by the source NF, first UE context information maintained by a first NF, and second UE context information maintained by a second NF, wherein the first NF is configured to perform session management functions and the second NF is not configured to perform session management functions; and / or ii) an identity list comprising a first temporary identifier, TID, allocated by the first NF to the UE.[000169] E2. The method of claim E1, wherein the create context message comprises the complete UE context information, and the method further comprises obtaining the complete UE context information after receiving the handover message.[000170] E3. The method of claim E2, wherein obtaining the complete UE context information comprises: transmitting to the first NF a first context request message; receiving from the first NF a first context response message responsive to the first context request message, wherein the first context response message comprises the first UE context information maintained by the first NF; transmitting to the second NF a second context request message; and receiving from the second NF a second context response message responsive to the second context request message, wherein the second context response message comprises the second UE context information maintained by the second NF.[000171] E4. The method of claim E3, wherein the first context request message comprises the first TID, thereby providing information to the first NF enabling the first NF to retrieve the first UE context information maintained by the first NF, and the second context request message comprises a second TID allocated by the second NF to the UE, thereby providing information to the second NF enabling the second NF to retrieve the second UE context information maintained by the second NF.[000172] E5. The method of any one of claims E1-E4, wherein the create context message comprises the identity list, and the identity list comprises a first information element comprising the first TID allocated by the first NF and an NF type value specifying an NF type of the first NF.[000173] E6. The method of claim E5, wherein the identity list further comprises a second information element comprising a second TID allocated by a second NF and an NF type value specifying an NF type of the second NF.[000174] E7. The method of any one of claims E1-E6, wherein the method further comprises transmitting to the first NF a PDU session context request comprising the first TID.[000175] F1. A method performed by a target network function, NF (e.g., an NF that performs access and / or mobility management functions), the method comprising: receiving from a source NF a create context message related to a handover of a user equipment, wherein the create context message comprises an identity list comprising a first temporary identifier, TID, allocated by a first NF to the UE, wherein the first NF is different than the source NF; allocating a second TID to the UE; and transmitting to the first NF a first update message comprising the second TID allocated by the target NF to the UE.[000176] F2. The method of claim F1, further comprising associating the identity list with the second TID allocated by the target NF to the UE.[000177] F3. The method of claim F1 or F2, wherein the first update message further comprises the first TID allocated by the first NF to the UE.[000178] F4. The method of any one of claims F1-F3, wherein the identity list further comprises a third TID allocated by a second NF to the UE, and the method further comprises transmitting to the second NF (e.g., a NF configured to perform policy management functions, like a 5G PCF) a second update message comprising the second TID allocated by the target NF to the UE.[000179] F5. The method of any one of claims F1-F4, wherein the target NF is a target access and mobility management function, and the first NF is a session management function.[000180] While various embodiments are described herein, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of this disclosure should not be limited by any of the above-described exemplary embodiments. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.[000181] As used herein transmitting a message "to” or "toward” an intended recipient encompasses transmitting the message directly to the intended recipient or transmitting the message indirectly to the intended recipient (i.e., one or more other nodes are used to relay the message from the source node to the intended recipient). Likewise, as used herein receiving a message "from” a sender encompasses receiving the message directly from the sender or indirectly from the sender (i.e., one or more nodes are used to relay the message from the sender to the receiving node). Further, as used herein "a” means "at least one” or "one or more.”[000182] Additionally, while the processes described above and illustrated in the drawings are shown as a sequence of steps, this was done solely for the sake of illustration. Accordingly, it is contemplated that some steps may be added, some steps may be omitted, the order of the steps may be re-arranged, and some steps may be performed in parallel.

Claims

CLAIMS1. A method (600) performed by a user equipment, UE (102), the method comprising: transmitting (s602) a first message (m302) to a network node (104) of a radio access network, RAN, wherein the first message comprises: a first non-access stratum, NAS, message to be processed by an instance of network function, NF, having a particular NF type, andNF routing information, NFRI, enabling the network node of the RAN to obtain an address of an instance of a NF of the particular NF type, and further wherein the NFRI does not comprise a NF identifier.

2. The method of claim 1, wherein the NFRI comprises a type value and the type value is: a NF type value specifying the particular NF type, or a NAS message type value to which the particular NF type is mapped.

3. The method of claim 1 or 2, wherein the method further comprises receiving a second NAS message, the second NAS message was generated by the instance of the NF, and the second NAS message comprises a temporary identifier allocated to the UE by the instance of the NF.

4. The method of claim 3, wherein the method further comprises transmitting a second message (m308) to the network node, wherein the second message comprises: a third NAS message to be processed by the instance of the NF, and the temporary identifier allocated to the UE by the instance of the NF.

5. The method of any one of claims 2-4, wherein the first message is a radio resource control, RRC, message, the first NAS message is included in a first information element, IE, of the RRC message, and the type value is included in a second IE of the RRC message.

6. The method of any one of claims 2-5, wherein the NFRI further comprises: single network slice selection assistance information, S-NSSAI, and a data network name, DNN.

7. The method of any one of claims 1-6, wherein the instance of the NF is an instance of a session management function.

8. The method of claim 7, wherein the session management function is a 6G session management function.

9. The method of claim 7 or 8, wherein the first NAS message is a PDU session establishment request.

10. The method of claim 3 or 4, the first NAS message comprises a PDU session identifier, and the method further comprises linking the temporary identifier with the PDU session identifier.11 . A method (700) performed by a network node (104) of a radio access network, RAN, the method comprising: receiving (s702) from a user equipment, UE (102), a first message (m302) comprising: i) a first non-access stratum, NAS, message to be processed by an instance of network function, NF, having a particular NF type, and ii) NF routing information, NFRI; using (s704) the NFRI to obtain an address of an instance of a NF of the particular NF type, wherein the NFRI does not comprise a NF identifier; and transmitting (s706) the first NAS message to the obtained address of the instance of the NF of the particular NF type.

12. The method of claim 11, wherein the NFRI comprises a type value and the type value is: a NF type value specifying the particular NF type, or a NAS message type value to which the particular NF type is mapped.

13. The method of claim 11 or 12, wherein the method further comprises receiving a second message from the instance of the NF, and the second message received from the instance of the NF comprises a temporary identifier allocated to the UE by the instance of the NF.

14. The method of claim 13, wherein the method further comprises:receiving a third message transmitted by the UE, wherein the third message comprises a second NAS message to be processed by the instance of the NF and the temporary identifier allocated to the UE by the instance of the NF; using the temporary identifier to obtain the address of the instance of the NF; and transmitting the second NAS message to the address obtained using the temporary identifier.

15. The method of any one of claims 11-14, wherein the first message is a radio resource control, RRC, message, the first NAS message is included in a first information element, IE, of the RRC message, and the type value is included in a second IE of the RRC message.

16. The method of any one of claims 11-15, wherein the NFRI further comprises: single network slice selection assistance information, S-NSSAI, and a data network name, DNN.

17. The method of any one of claims 11-16, wherein using the NFRI to obtain the address comprises transmitting a discovery request comprising the NFRI, and the method comprises receiving a discovery response responsive to the discovery request, the discovery response comprising the address or information enabling the network node to obtain the address.

18. The method of any one of claims 11-17, wherein the instance of the NF is an instance of a session management function, SMF.

19. The method of claim 18, wherein the first NAS message is a PDU session establishment request.

20. A computer program (1243) comprising instructions (1244) which when executed by processing circuitry (1202) of a user equipment (102) causes the user equipment to perform the method of any one of claims 1-10.21 . A carrier containing the computer program of claim 20, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer readable storage medium (1232).

22. A user equipment, UE (102), the UE being configured to: transmit (s602) a first message (m302) to a network node (104) of a radio access network, RAN, wherein the first message comprises:a first non-access stratum, NAS, message to be processed by an instance of network function, NF, having a particular NF type, andNF routing information, NFRI, enabling the network node of the RAN to obtain an address of an instance of a NF of the particular NF type, and further wherein the NFRI does not comprise a NF identifier.

23. The UE of claim 22, wherein the UE is further configured to perform the method of any one of claims 2- 10.

24. A user equipment (102), the UE comprising: a storage unit (1208); and processing circuitry (1202) coupled to the storage unit, wherein the network node is configured to perform the method of any one of claims 1-10.

25. A computer program (1343) comprising instructions (1344) which when executed by processing circuitry (1302) of a network node (104, 1300) causes the network node to perform the method of any one of claims 11-19.

26. A carrier containing the computer program of claim 25, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer readable storage medium (1332).

27. A network node (104, 1300) of a radio access network, RAN, the first network node being configured to: receive (s702) from a user equipment, UE (102), a first message (m302) comprising: I) a first non-access stratum, NAS, message to be processed by an instance of network function, NF, having a particular NF type, and ii) NF routing information, NFRI; use (s704) the NFRI to obtain an address of an instance of a NF of the particular NF type, wherein the NFRI does not comprise a NF identifier; and transmit (s706) the first NAS message to the obtained address of the instance of the NF of the particular NF type.

28. The network node of claim 27, wherein the network node is further configured to perform the method of any one of claims 12-19.

29. A network node (104, 1300), the network node comprising: a storage unit (1308); andprocessing circuitry (1302) coupled to the storage unit, wherein the network node is configured to perform the method of any one of claims 11-19.

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