Method and apparatus for addressing mismatch in SMF sets

Abstract

This invention provides a method and apparatus for addressing mismatches in the session management function (SMF) set. [Solution] The method performed by the Access and Mobility Function (AMF) includes: obtaining third information about whether a resource is exclusively bound to a particular service instance in a first SMF; obtaining fourth information about whether a second SMF supports the re-selection of an alternative first SMF instance within the SMF set of the first SMF; detecting that the first SMF has failed; and re-selecting an alternative service instance within the SMF set of the first SMF based on the third and fourth information.

Description

Technical Field

[0001] The non-limiting and exemplary embodiments of the present disclosure generally relate to the technical field of communications, and more specifically, to methods and apparatuses for addressing mismatches in a set of SMFs (Session Management Functions).

Background Art

[0002] This section introduces aspects that may facilitate a better understanding of the present disclosure. Therefore, the description in this section should be read from this perspective and should not be construed as an admission of what is in the prior art or what is not in the prior art.

[0003] For example, in an NR (New Radio) communication network as defined by the 3rd Generation Partnership Project (3GPP (registered trademark)), NF set-based session resilience (recovery processing) is introduced, where equivalent control plane network functions (NFs) can be grouped into NF sets. For example, several SMF instances are grouped into an SMF set. Multiple NFs within an NF set are interchangeable because they share the same context data. In scenarios such as failures, load distribution, and load re-distribution, an NF can be replaced by an alternative NF within the same NF set.

[0004] An SMF can serve as an SMF for different PDU session contexts, a V-SMF (Visited SMF), or an H-SMF (Home SMF). The concept of an SMF set does not distinguish between the roles of different SMFs. When an SMF is registered with the SMF set ID (identifier) of the NRF (Network Repository Function), it means that the SMF can support SMF set-based resilience for all session contexts established in the role of an SMF, a V-SMF, or an H-SMF when the SMF is used simultaneously for non-roaming (the role of an SMF), roaming in (the role of a V-SMF), or roaming out (the role of an H-SMF). [Overview of the project]

[0005] This summary of the invention is provided in a simplified form to introduce a selection of concepts that will be further described in the following detailed description. This summary of the invention is not intended to identify any major or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0006] To support SMF set resilience for roaming interworking between VPLMN and HPLMN, both VPLMN (Visited PLMN (Public Ground Mobile Network)) and HPLMN (Home PLMN) are required to deploy (install) SMF sets and support resilience functions for the roles of V-SMF and H-SMF.

[0007] In actual network deployments, it's unlikely that all PLMNs will deploy SMF sets. It's also possible that a PLMN might set up SMF sets for non-roaming users. However, SMF sets don't support roaming user resilience, or the resilience of SMF sets isn't included in the roaming agreement.

[0008] It is also unclear whether a peer SMF supports SMF sets and whether it provides binding indications in request and response messages. NRF-based service discovery may be helpful, but it would introduce at least extra signaling latency and would not cover cases where SMF sets are set for PDU sessions for non-roaming UEs but not for home-routed PDU sessions. If such support for SMF set information is not available, it would result in PDU sessions being serviced by a failed SMF being unnecessarily deleted or left as hung resources.

[0009] The network behavior when VPLMN or HPLMN have different SMF set recovery capabilities or configurations is not specified in the current 3GPP® release, and potential mismatches between VPLMN and HPLMN can occur in SMF failure scenarios. As a result, it may take time to reactivate all related PDU sessions, affecting service availability.

[0010] For example, V-SMF supports SMF sets, but H-SMF does not. Therefore, if a V-SMF failure is detected, H-SMF will locally delete the PDU session, while V-SMF will maintain the PDU session. Mobile termination services will be affected.

[0011] V-SMF does not support SMF sets, but H-SMF does. If an H-SMF failure is detected, V-SMF will release the affected PDU sessions, which may leave the PDU sessions hung up in an alternative H-SMF, which in turn may hang up further upstream, for example, in a PCF.

[0012] While the 3GPP® does not clearly define support for the SMF(NF)(service) set, in the applicant's opinion, it includes at least two embodiments for supporting SMF(NF). 1) All resource contexts provided by an SMF may be shared by at least one SMF within the same SMF (service) set or its backup SMF, and as a result, in the event of an SMF failure, a peer entity can select an alternative when it detects the failure of an SMF. 2) SMF can re-select an alternative peer entity based on binding indications provided by the peer entity, or on the NF profile of the peer entity registered in the NRF when SMF detects that the peer entity has failed.

[0013] According to one embodiment, it can be claimed that SMF supports the SMF set function as long as SMF supports bullet 2.

[0014] However, if SMF only supports bullet 2, it seems reasonable to consider this, because you may be allowed to request support for the SMF set, and supporting bullet 2 in an implementation is much easier than supporting bullet 1, which requires larger changes in both software and hardware.

[0015] However, consider the following scenario: If the H-SMF does not support resilience, meaning its resources are bound only to a specific NF service instance, then support will be indicated to SETFRI because if the V-SMF fails, another V-SMF can be re-selected.

[0016] Therefore, if this H-SMF fails, the peer SMF (V-SMF) cannot trigger a restore (recovery) immediately after detecting the H-SMF failure. Instead, the peer SMF will only trigger a restore when there are signaling messages to be sent for PDU sessions destined for the failed H-SMF. However, when the peer V-SMF searches for an alternative H-SMF, it will find that no alternative H-SMF exists.

[0017] In fact, in PDU sessions where H-SMF is removed, all PDU sessions hosted (served) by this H-SMF are unable to receive mobile termination services and suffer significant hang-up resources in V-SMF and AMF.

[0018] To overcome or mitigate at least one of the aforementioned problems or other issues, a new solution is needed to address mismatches in SMF sets.

[0019] A first aspect of this disclosure provides a method performed by an Access and Mobility Function (AMF). This method may include obtaining third information about whether a resource is exclusively bound to a particular service instance within a first Session Management Function (SMF). This method may further include obtaining fourth information about whether a second SMF supports the re-selection of an alternative first SMF instance within the SMF set of the first SMF. This method may further include detecting that the first SMF has failed. This method may further include re-selecting an alternative service instance within the SMF set of the first SMF based on the third and fourth information.

[0020] According to one embodiment, the third piece of information may be of Boolean type, and / or the fourth piece of information may be of Boolean type.

[0021] According to one embodiment, obtaining the third information may include sending a network function (NF) discovery request to a network repository function (NRF) and receiving an NF discovery response containing the third information from the NRF.

[0022] According to one embodiment, obtaining the third information may include receiving a service response message or service request message containing the third information from the first SMF.

[0023] According to one embodiment, obtaining the fourth information may include sending an NF discovery request to the NRF and receiving an NF discovery response from the NRF that includes the fourth information.

[0024] According to one embodiment, obtaining the fourth information may include receiving an update session management (SM) context response message containing the fourth information from the first SMF.

[0025] According to one embodiment, re-selecting an alternative service instance within the SMF set of the first SMF based on third and fourth information may include re-selecting an alternative V-SMF service instance within the SMF set of the first SMF if the third information indicates that the resource is not exclusively bound to a particular service instance in the first SMF, and the fourth information indicates that the second SMF supports re-selecting an alternative first SMF instance within the SMF set of the first SMF.

[0026] According to one embodiment, reselecting an alternative service instance within the SMF set of the first SMF based on the third information and the fourth information may further include reselecting an alternative first SMF service instance within the SMF set of the first SMF when the third information indicates that the resource is not exclusively bound to a specific service instance in the first SMF and the fourth information indicates that the second SMF does not support reselecting an alternative first SMF instance within the SMF set of the first SMF, and sending a request to the alternative first SMF to delete at least one protocol data unit (PDU) session destined for a user equipment (UE) that is affected.

[0027] According to one embodiment, reselecting an alternative service instance within the SMF set of the first SMF based on the third information and the fourth information may include releasing at least one affected PDU session without reselecting an alternative first SMF service instance when the third information indicates that the resource is exclusively bound to a specific service instance in the first SMF.

[0028] According to an embodiment, the first SMF may be a visited SMF, and the second SMF may be a home SMF, or the first SMF may be an intermediate SMF and the second SMF may be an anchor SMF.

[0029] According to one embodiment, the method may further include obtaining fifth information as to whether the resource is exclusively bound to a specific service instance in the second SMF. The method may further include sending the fifth information to the first SMF.

[0030] A second aspect of this disclosure provides a method performed by a first session management function (SMF). This method includes sending a third piece of information to the AMF about whether a resource is exclusively bound to a particular service instance in the first SMF. This method may further include sending a fourth piece of information to the AMF about whether the second SMF supports re-selecting an alternative first SMF instance in the first SMF set. The third and fourth pieces of information are used by the AMF to re-select an alternative service instance in the first SMF set if the first SMF fails.

[0031] According to one embodiment, the fifth piece of information is obtained from access and mobility functions, AMF, or a second SMF.

[0032] According to one embodiment, the method may further include obtaining a fifth piece of information about whether a resource is exclusively bound to a particular service instance in the second SMF. The method further includes obtaining a sixth piece of information about whether the first SMF supports the re-selection of an alternative second SMF instance within the SMF set of the second SMF.

[0033] According to one embodiment, the method may further include obtaining a fourth piece of information.

[0034] According to one embodiment, obtaining the fourth information may include receiving the fourth information from the second SMF.

[0035] According to one embodiment, the third information may be included in a service request or response message.

[0036] According to one embodiment, the fourth piece of information may be included in the updated SM context response message.

[0037] According to one embodiment, the method may further include transmitting third information to a second SMF.

[0038] According to one embodiment, the first SMF may be a visited SMF and the second SMF may be a home SMF, or the first SMF may be an intermediate SMF and the second SMF may be an anchor SMF.

[0039] A third aspect of this disclosure provides a method performed by a second session management function (SMF). This method may include receiving third information from the first SMF about whether a resource is exclusively bound to a particular service instance in the first SMF. This method may further include obtaining fourth information about whether the second SMF supports re-selection of an alternative first SMF instance within the first SMF set of SMFs.

[0040] According to one embodiment, the method may further include sending a fifth piece of information to the first SMF regarding whether a resource is exclusively bound to a particular service instance in the second SMF.

[0041] According to one embodiment, the first SMF may be a visited SMF and the second SMF may be a home SMF, or the first SMF may be an intermediate SMF and the second SMF may be an anchor SMF.

[0042] A fourth aspect of this disclosure provides an Access and Mobility Function (AMF). The AMF comprises a processor and memory coupled to the processor. The memory contains instructions that can be executed by the processor. The AMF is operable to obtain third information about whether a resource is exclusively bound to a particular service instance in a first Session Management Function (SMF). The AMF is further operable to obtain fourth information about whether a second SMF supports the re-selection of an alternative first SMF instance within the SMF set of the first SMF. The AMF is further operable to detect that the first SMF has failed. Based on the third and fourth information, the AMF is further operable to re-select an alternative service instance within the SMF set of the first SMF.

[0043] A fifth aspect of this disclosure provides a first session management function (SMF). The first SMF comprises a processor and memory coupled to the processor. The memory contains instructions that can be executed by the processor. The first SMF operates to send a third information to the AMF about whether a resource is exclusively bound to a particular service instance within the first SMF. The first SMF is further operable to send a fourth information to the AMF about whether a second SMF supports the re-selection of an alternative first SMF instance within the first SMF set. The third and fourth information may be used by the AMF to re-select an alternative service instance within the first SMF set if the first SMF fails.

[0044] A sixth aspect of this disclosure provides a second session management function (SMF). The second SMF comprises a processor and memory coupled to the processor. The memory contains instructions that can be executed by the processor. The second SMF operates to receive a third piece of information from the first SMF about whether a resource is exclusively bound to a particular service instance in the first SMF. The second SMF is further operable to obtain a fourth piece of information about whether the second SMF supports re-selection of an alternative first SMF instance within the first SMF set of SMFs.

[0045] A seventh aspect of this disclosure provides an AMF. The AMF includes a first acquisition module that acquires third information about whether a resource is exclusively bound to a particular service instance within a first session management function (SMF). According to one embodiment, the AMF further includes a second acquisition module configured to acquire fourth information about whether a second SMF supports the reselection of an alternative first SMF instance within the SMF set of the first SMF. The AMF further includes a detection module configured to detect that the first SMF has failed. The AMF further includes a reselection module configured to reselect an alternative service instance within the SMF set of the first SMF based on the third and fourth information.

[0046] According to one embodiment, the AMF may further have a third retrieval module that can be configured to retrieve a fifth piece of information about whether a resource is exclusively bound to a particular service instance in a second SMF.

[0047] According to one embodiment, the AMF may further have a transmitting module configured to transmit a fifth piece of information to the first SMF.

[0048] An eighth aspect of this disclosure provides a first SMF. The first SMF may include a first transmit module configured to transmit a third information to the AMF about whether a resource is exclusively bound to a particular service instance within the first SMF. The first SMF may further include a second transmit module configured to transmit a fourth information to the AMF about whether a second SMF supports the re-selection of an alternative first SMF instance within the SMF set of the first SMF.

[0049] According to one embodiment, the third and fourth pieces of information may be used by the AMF to re-select an alternative service instance within the SMF set of the first SMF when the first SMF fails.

[0050] According to one embodiment, the first SMF may further include a first retrieval module configured to retrieve a fifth piece of information about whether a resource is exclusively bound to a particular service instance in the second SMF. The first SMF may further include a second retrieval module configured to retrieve a sixth piece of information about whether the first SMF supports the re-selection of an alternative second SMF instance within the SMF set of the second SMF.

[0051] According to one embodiment, the first SMF may further include a third acquisition module configured to acquire a fourth piece of information.

[0052] According to one embodiment, the first SMF may further include a third transmitting module configured to transmit third information to the second SMF.

[0053] A ninth aspect of this disclosure provides a second SMF. The second SMF may include a receive module configured to receive a third piece of information from the first SMF, which is whether a resource is exclusively bound to a particular service instance within the first SMF. The second SMF may further include a retrieve module configured to obtain a fourth piece of information, which is whether the second SMF supports re-selection of an alternative first SMF instance within the first SMF set of SMFs.

[0054] According to one embodiment, the second SMF may further include a transmission module configured to send a fifth piece of information to the first SMF regarding whether a resource is exclusively bound to a particular service instance within the second SMF.

[0055] In another aspect of the present disclosure, a computer program product is provided which, when executed by at least one processor, comprises instructions causing at least one processor to perform a method according to any one of the first, second, or third aspects.

[0056] In another aspect of the present disclosure, a computer-readable storage medium is provided that stores instructions causing at least one processor to perform a method according to one of the first, second, or third aspects when executed by at least one processor.

[0057] The embodiments of this specification can offer many advantages, and a non-exhaustive list of examples follows. According to some embodiments of this specification, a restore (recovery) procedure for recovering PDU sessions affected by an SMF failure is proposed. According to some embodiments of this specification, the time required to recover PDU sessions affected by an SMF failure can be reduced. According to some embodiments of this specification, the problem of ghost sessions can be solved. According to some embodiments of this specification, the availability of services can be improved. The embodiments of this specification are not limited to the features and advantages described above. Those skilled in the art will recognize additional features and advantages by reading the detailed description below. [Brief explanation of the drawing]

[0058] The above and other aspects, features, and advantages of various embodiments of the present disclosure will become more fully apparent, for example, from the following detailed description with reference to the accompanying drawings, where similar reference numbers or letters are used to designate similar or equivalent elements. The drawings are provided to facilitate a better understanding of the embodiments of the present disclosure and are not necessarily drawn to scale.

[0059] [Figure 1] This illustrates a first failure scenario according to an embodiment of the present disclosure.

[0060] [Figure 2] This illustrates a second failure scenario according to embodiments of the present disclosure.

[0061] [Figure 3] This illustrates a third failure scenario according to embodiments of the present disclosure.

[0062] [Figure 4] This illustrates a fourth failure scenario according to embodiments of the present disclosure.

[0063] [Figure 5]This illustrates a fifth failure scenario according to embodiments of the present disclosure.

[0064] [Figure 6] This illustrates a sixth failure scenario according to embodiments of the present disclosure.

[0065] [Figure 7] This schematically illustrates a roaming 5G system architecture according to an embodiment of the present disclosure.

[0066] [Figure 8] This shows a flowchart of the method according to an embodiment of the present disclosure.

[0067] [Figure 9] This shows a flowchart illustrating how to obtain first information about whether a first SMF supports a first capability according to an embodiment of the present disclosure.

[0068] [Figure 10] This shows a flowchart illustrating how to obtain second information regarding whether a second SMF supports the first capability, according to an embodiment of the present disclosure.

[0069] [Figure 11] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0070] [Figure 12] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0071] [Figure 13] This flowchart shows how to obtain third information, according to embodiments of the present disclosure, regarding whether a first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF.

[0072] [Figure 14]This shows a flowchart, according to one embodiment of the present disclosure, for obtaining a fourth piece of information regarding whether the second SMF supports a local NF set for the second SMF and a peer NF set for the first SMF.

[0073] [Figure 15] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0074] [Figure 16] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0075] [Figure 17] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0076] [Figure 18] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0077] [Figure 19] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0078] [Figure 20a] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0079] [Figure 20b] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0080] [Figure 21a] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0081] [Figure 21b] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0082] [Figure 22] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0083] [Figure 23] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0084] [Figure 24] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0085] [Figure 25] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0086] [Figure 26] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0087] [Figure 27a] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0088] [Figure 27b] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0089] [Figure 28] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0090] [Figure 29] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0091] [Figure 30] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0092] [Figure 31] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0093] [Figure 32] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0094] [Figure 33] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0095] [Figure 34] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0096] [Figure 35] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0097] [Figure 36] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0098] [Figure 37] This shows a flowchart of an exemplary solution for V-SMF failure according to embodiments of the present disclosure.

[0099] [Figure 38] This shows a flowchart of an exemplary solution for V-SMF failure according to another embodiment of the present disclosure.

[0100] [Figure 39] This shows a flowchart of an exemplary solution for V-SMF failure according to another embodiment of the present disclosure.

[0101] [Figure 40] This shows a flowchart of an exemplary solution for H-SMF failure according to embodiments of the present disclosure.

[0102] [Figure 41] This shows a flowchart of an exemplary solution for H-SMF failure according to another embodiment of the present disclosure.

[0103] [Figure 42a] This shows a flowchart of an exemplary solution for H-SMF failure according to another embodiment of the present disclosure.

[0104] [Figure 42b] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0105] [Figure 42c] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0106] [Figure 42d] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0107] [Figure 42e] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0108] [Figure 42f] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0109] [Figure 42g] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0110] [Figure 42h] This shows a flowchart of a method according to another embodiment of the present disclosure.

[0111] [Figure 43] This block shows an apparatus suitable for carrying out some embodiments of the present disclosure.

[0112] [Figure 44] This is a block diagram of an AMF according to one embodiment of the present disclosure.

[0113] [Figure 45] This is a block diagram showing a first SMF according to one embodiment of the present disclosure.

[0114] [Figure 46] This is a block diagram of a second SMF according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0115] Embodiments of the Disclosure are described below in detail with reference to the accompanying drawings. These embodiments are discussed solely for the purpose of enabling those skilled in the art to better understand and thus implement the Disclosure, and should not be understood as implying any limitation to the scope of the Disclosure. Throughout this Specification, the criteria for features, advantages, or similar terms are not intended to imply that all features and advantages that may be realized by the Disclosure should be or should be found in any single embodiment of the Disclosure. Rather, the terms referring to features and advantages should be understood to mean that a particular feature, advantage, or characteristic described in relation to an embodiment is included in at least one embodiment of the Disclosure. Furthermore, the features, advantages, and characteristics described in the Disclosure may be combined in any suitable manner in one or more embodiments. Those skilled in the art will recognize that the Disclosure may be implemented without one or more of the particular features or advantages of a particular embodiment. In other cases, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the Disclosure.

[0116] As used herein, the term “Network” refers to a network conforming to any appropriate communication standard, such as New Radio (NR), Long-Term Evolution (LTE), LTE Advanced (LTE-A), Broadband Code Division Multiple Access (WCDMA®), High-Speed ​​Packet Access (HSPA), Code Division Multiple Access (CDMA), Time Division Multiple Destination (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), Single Carrier Frequency Division Multiple Access (SC-FDMA), and other wireless networks. A CDMA network may implement radio technologies such as Universal Terrestrial Radio Access (UTRA), which includes WCDMA® and other variations of CDMA. A TDMA network may implement radio technologies such as Global System for Mobile Communications (GSM). OFDMA networks can implement wireless technologies such as Evolved UTRA (E-UTRA), Ultra-Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, ad-hoc networks, and wireless sensor networks. In the following description, the terms “network” and “system” can be used interchangeably. Furthermore, communication between two devices within a network may be carried out according to any suitable communication protocol, including but not limited to communication protocols defined by standardization organizations such as 3GPP®. For example, communication protocols may include first-generation (1G), 2G, 3G, 4G, 4.5G, 5G communication protocols, and / or any other protocols currently known or to be developed in the future.

[0117] The terms “network device,” “network node,” or “network function” refer to any suitable network function (NF) that can be implemented on a network element (physical or virtual) of a communication network. For example, a network function can be implemented as a network element on dedicated hardware, as a software instance running on dedicated hardware, or as a virtualized function instantiated on a suitable platform, for example, on a cloud infrastructure. For example, a 5G system (5GS) may include multiple NFs such as AMF (Access and Mobility Function), SMF (Session Management Function), AUSF (Authentication Service Function), UDM (Unified Data Management), PCF (Policy Control Function), AF (Application Function), NEF (Network Exposure Function), UPF (User Plane Function), and NRF (Network Repository Function), RAN (Radio Access Network), SCP (Service Communication Proxy), NWDAF (Network Data Analysis Function), NSSF (Network Slice Selection Function), and NSSAAF (Network Slice Identification Authentication and Authorization Function).

[0118] The term “Terminal device” refers to any terminal device that can access a communication network and receive services from it. Examples, but not limited to, a terminal device may include a mobile terminal, user equipment (UE), or other suitable device. A UE may, for example, be a subscriber station (SS), portable subscriber station, mobile station (MS), or access terminal (AT). A terminal device may include, but is not limited to, portable computers, digital cameras, game terminal devices, image capture terminal devices such as music storage and playback devices, mobile phones, cell phones, smartphones, voice over IP (VoIP) phones, wireless local loop phones, tablets, wearable devices, personal digital assistants (PDAs), portable computers, desktop computers, wearable terminal devices, in-vehicle wireless terminal devices, wireless endpoints, mobile stations, laptop embedded devices (LEE), laptop mounted devices (LME), USB dongles, smart devices, and wireless customer premises equipment (CPE). In the following description, the terms “Terminal device,” “Terminal,” “User equipment,” and “UE” may be used interchangeably. As an example, a terminal device may represent a UE configured to communicate in accordance with one or more communication standards published by 3GPP® (Third Generation Partnership Project), such as the LTE or NR standards of 3GPP®. As used herein, “user device” or “UE” does not necessarily have a “user,” but means a human user who owns and / or operates the device in question. According to some embodiments, a terminal device may be configured to transmit and / or receive information without direct human interaction. For example, a terminal device may be designed to transmit information to a network at a predetermined schedule, when triggered by an internal or external event, or in response to a request from a communication network. Alternatively, a UE may represent a device intended for sale to or operation by a human user, but not initially associated with a specific human user.

[0119] As yet another example, in an Internet of Things (IoT) scenario, a terminal device can represent a machine or other device that performs monitoring and / or measurement and transmits the results of such monitoring and / or measurement to another terminal device and / or network equipment. In this case, the terminal device may also be a machine-to-machine (M2M) device, sometimes referred to as a machine-type communication (MTC) device in the context of 3GPP®. In one particular example, a terminal device may be a UE implementing the 3GPP® Narrowband Internet of Things (NB-IoT) standard. Specific examples of such machines or devices include sensors, measuring devices such as power meters, industrial machinery, or household or personal devices, such as refrigerators, televisions, and personal wearables like watches. In other scenarios, a terminal device can represent a vehicle or other equipment that can monitor and / or report its operating status or other functions related to its operation.

[0120] References in this specification to “one embodiment,” “one example,” or “exemplary embodiment” indicate that the described embodiments may include certain features, structures, or characteristics, but it is not necessary that all embodiments include those features, structures, or characteristics. Furthermore, such phrases do not necessarily refer to the same embodiment. Moreover, if certain features, structures, or characteristics are described in relation to an embodiment, it will be understood that, whether explicitly stated or not, the influence of such features, structures, or characteristics in relation to other embodiments is within the knowledge of those skilled in the art.

[0121] In this specification, terms such as “first” and “second” may be used to describe various elements, but it should be understood that these elements should not be limited by these terms. These terms are used solely to distinguish one element from another. For example, without departing from the scope of the exemplary embodiments, a first element may be called a second element, and similarly, a second element may be called a first element. As used herein, the term “and / or” includes any and all combinations of one or more of the related enumerated terms.

[0122] When used herein, the phrase "at least one of A and B" or "at least one of A or B" should be understood to mean "A only, B only, or both A and B." The phrase "A and / or B" should be understood to mean "A only, B only, or both A and B."

[0123] The terms used herein are intended solely to describe specific embodiments and are not intended to limit the exemplary embodiments. Where used herein, the singular forms “a,” “an,” and “the” are intended to include the plural form unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “has,” “having,” “includes,” and / or “including,” where used herein, will be further understood to identify the presence of a described feature, element, and / or component, but not to exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0124] These terms used herein are solely for the purpose of facilitating the description and differentiation between nodes, devices, or networks. As this technology develops, other terms with similar or identical meanings may also be used.

[0125] In the following description and claims, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by one of the persons of ordinary skill in the art to which this disclosure belongs.

[0126] The subject matter described herein focuses on the mismatch problem for roaming interworking between V-SMF and H-SMF. However, similar mismatch problems also exist in scenarios where I-SMF (intermediate SMF) and anchor SMF have different resilience or configurations.

[0127] The following mismatch issues may need to be considered.

[0128] V-SMF failure: ● VPLMN does not deploy the SMF set. This is not a problem. ● VPLMN deploys the SMF set, and V-SMF supports the SMF set functionality. The H-SMF supports SMF sets, and there are no issues with normal set handling. H-SMF does not support SMF sets (HPLMN may or may not deploy SMF sets to non-roaming users), and there is a mismatch between V-SMF and H-SMF. ● VPLMN deploys SMF sets, but V-SMF does not support SMF set functionality. H-SMF supports SMF sets, and there is a mismatch between V-SMF and H-SMF. H-SMF does not support SMF sets (HPLMN may or may not deploy SMF sets to non-roaming users), and there is a mismatch between AMF and V-SMF.

[0129] HSMF dysfunction: ● HPLMN does not deploy the SMF set. This is not a problem. ● HPLMN deploys SMF sets, and H-SMF supports the SMF set functionality. The V-SMF supports SMF sets, and there are no issues with normal set handling. V-SMF does not support SMF sets (VPLMN may or may not deploy SMF sets to non-roaming users). There is a mismatch between V-SMF and H-SMF. ● HPLMN deploys SMF sets, but H-SMF does not support SMF set functionality. V-SMF supports SMF sets, and there is a mismatch between V-SMF and H-SMF. V-SMF does not support SMF sets (VPLMN may or may not deploy SMF sets for non-roaming users), and in HPLMN, there is a mismatch between H-SMF and other NFs, such as UDM (Unified Data Management) or PCF (Policy Control Function).

[0130] The following failure scenarios are considered. V-SMF failure: 1. V-SMF supports SMF sets for roaming interfaces (it is recommended to introduce the new Nsmf_PDUSession service feature). aH-SMF supports SMF sets, applying and not modifying the standard SMF set logic. bH-SMF does not support SMF sets, and H-SMF can maintain a context-awaiting state for a potential restore (recovery process) triggered by AMF re-selecting another V-SMF within the same set, or delete affected PDU sessions (legacy behavior of H-SMF and AMF). AMF can request the UE to reactivate the PDU session based on the local configuration if the PDU session should be deleted. 2. V-SMF does not support SMF sets: a. Regardless of whether H-SMF supports SMF sets or not, H-SMF will remove the affected PDU session. To cover 1b and 2a, it is desirable to define another new feature so that AMF and H-SMF know that it is supported. HSMF dysfunction: 1. H-SMF does not support SMF sets, and V-SMF releases the PDU session. 2. H-SMF supports SMF sets (we propose introducing new functionality for the Nsmf_PDUSession service). aV-SMF supports SMF sets that apply the re-selection of another SMF within the same SMF set. bV-SMF does not support SMF sets, and V-SMF will release the affected PDU sessions.

[0131] Figure 1 shows a first failure scenario according to an embodiment of the present disclosure.

[0132] In the initial failure scenario, VPLMN deploys the SMF set, V-SMF supports the SMF set, and H-SMF does not support the SMF set.

[0133] As shown in Figure 1, if the H-SMF does not support the SMF set after detecting a V-SMF failure (i.e., a vSMF1 failure), the H-SMF (i.e., hSMF1) will initiate the release of the associated PDU session. However, since the V-SMF (i.e., a vSMF1 failure) does support the SMF set, the AMF in the VPLMN will re-select vSMF2 as another SMF example in the same SMF set A, and the re-selected vSMF2 will then recover the SM (Session Management) context and initiate an update request to the H-SMF (i.e., hSMF1). Nevertheless, the update request will fail because the H-SMF (i.e., hSMF1) has already triggered the release of the corresponding PDU session after detecting the failure of vSMF1. Since vSMF2 has no clue about the PDU session state on the original H-SMF side, V-SMF2 can only release its local SM context per session based on the error response from the H-SMF (i.e., hSMF1). As a result, reactivating all related PDU sessions takes time, impacting service availability.

[0134] The message shown in Figure 1 may be the same as or similar to the corresponding message described in 3GPP® TS 23.502 V17.2.1, and its disclosure is incorporated herein by standard in its entirety.

[0135] Figure 2 shows a second failure scenario according to an embodiment of the present disclosure.

[0136] In the second failure scenario, VPLMN deploys the SMF set, V-SMF does not support the SMF set, and H-SMF does support the SMF set.

[0137] It should be noted that this scenario can occur during a development phase where a VPLMN SMF vendor has implemented SMF set functionality for the SMF role, but has not yet implemented SMF set functionality for the V-SMF role.

[0138] As shown in Figure 2, after detecting a vSMF1 failure, the AMF in the VPLMN re-selects another SMF in the same SMF set A (vSMF2, for example) for the established PDU session. The AMF sends an Nsmf_PDUSession_UpdateSMContext request to the re-selected vSMF2. However, the re-selected vSMF2 does not have the logic to recover the session context, and because V-SMF does not support SMF set-based roaming recovery (resilience), it triggers a PDU session update request to hSMF1 with the updated vSMF2's callbackUri. Instead, the re-selected V-SMF rejects the Nsmf_PDUSession_UpdateSMContext request with an error response. As a result, the AMF in the VPLMN can only trigger PDU session reactivation on a per-session basis based on the error response from v-SMF2, which takes time to reactivate all related PDU sessions and impacts service availability. Furthermore, if the reactivation selects an H-SMF from a different SMF set, a ghost session may exist on the original H-SMF.

[0139] The message shown in Figure 2 may be the same as, or similar to, the corresponding message described in 3GPP® TS 23.502 V17.2.1 (whose disclosure is incorporated herein by standard in its entirety).

[0140] Figure 3 shows a third failure scenario according to an embodiment of the present disclosure.

[0141] In the third failure scenario, VPLMN deploys the SMF set, but V-SMF does not support the SMF set, and H-SMF does not support the SMF set.

[0142] As shown in Figure 3, H-SMF initiates the release of the associated PDU session if H-SMF does not support SMF set-based roaming resilience. When VPLMN deploys an SMF set, the AMF within VPLMN re-selects another SMF within the same SMF set (vSMF2, for example). The AMF sends an Nsmf_PDUSession_UpdateSMContext request to the re-selected vSMF2. Similarly, in a second failure scenario, the re-selected vSMF2 has no logic to recover the session context and, because V-SMF does not support SMF set-based roaming resilience, triggers a PDU session update request to hSMF1 with the updated vSMF2's callbackUri. Instead, the re-selected V-SMF rejects the Nsmf_PDUSession_UpdateSMContext request with an error response. As a result, the AMF within VPLMN can only trigger PDU session reactivation on a per-session basis based on error responses from V-SMF, and reactivating all related PDU sessions takes time, impacting service availability.

[0143] The message shown in Figure 3 may be the same as or similar to the corresponding message described in 3GPP® TS 23.502 V17.2.1, and its disclosure is incorporated herein by standard in its entirety.

[0144] Figure 4 shows a fourth failure scenario according to an embodiment of the present disclosure.

[0145] In the fourth failure scenario, HPLMN deploys the SMF set, H-SMF supports the SMF set, and V-SMF does not support the SMF set.

[0146] As shown in Figure 4, when V-SMF in VPLMN detects that hSMF1 in SMF set B of HPLMN has failed, V-SMF for existing PDU sessions does not re-select another SMF in SMF set B because V-SMF does not support the SMF set function. Instead, V-SMF triggers an SM context release to AMF, which then triggers PDU session reactivation. However, if PDU reactivation selects an SMF in a different SMF set, there may be ghost sessions in SMF set B.

[0147] The message shown in Figure 4 may be the same as, or similar to, the corresponding message described in 3GPP® TS 23.502 V17.2.1 (whose disclosure is incorporated herein by standard in its entirety).

[0148] Figure 5 shows a fifth failure scenario according to an embodiment of the present disclosure.

[0149] In the fifth failure scenario, HPLMN deploys the SMF set, H-SMF does not support the SMF set, and V-SMF does support the SMF set.

[0150] This fifth failure scenario could occur during the development phase, such as when the HPLMN's SMF vendor has implemented the SMF set functionality for the SMF role, but has not yet implemented the SMF set functionality for the H-SMF role.

[0151] As shown in Figure 5, there are problems with both the VPLMN and HPLMN that initiated the request.

[0152] In VPLMN, after detecting a failure in hSMF1, V-SMF re-selects another SMF within the same SMF set B (e.g., hSMF2) for established PDU sessions and sends a PDU session update request to the re-selected hSMF2. However, since hSMF2 lacks the logic to recover the session context, hSMF2 rejects the PDU session update request with "CONTEXT_NOT_FOUND". As a result, the AMF in VPLMN can only trigger PDU session reactivation on a per-session basis based on the error response from V-SMF, which takes time to reactivate all related PDU sessions and impacts service availability. Additionally, if reactivation selects an H-SMF in a different SMF set, ghost sessions may exist on the original H-SMF.

[0153] In HPLMN, surrounding 5GC (5G Core Network) NFs are considered H-SMFs that support the SMF set. For example, after a PCF detects an hSMF1 failure, it re-selects another H-SMF in the same SMF set, but the re-selected H-SMF does not have the application logic to recover the session context and process notification requests from the PCF. Depending on the implementation, if the H-UPF (home UPF) does not release the context associated with the failed hSMF1 (i.e., what the H-UPF considers to be hSMF1 in the SMF set), downlink data can still arrive at the V-UPF, and the network trigger service request procedure can succeed. However, since the H-SMF does not process the UpdateNotify request from the PCF (including PCC rules for MT calls), the call will not be set up.

[0154] The message shown in Figure 5 may be the same as, or similar to, the corresponding message described in 3GPP® TS 23.502 V17.2.1 (whose disclosure is incorporated herein by standard in its entirety).

[0155] Figure 6 shows a sixth failure scenario according to an embodiment of the present disclosure.

[0156] In the sixth failure scenario, HPLMN deploys an SMF set, but H-SMF does not support SMF sets, and V-SMF does not support SMF sets.

[0157] As shown in Figure 6, when the vSMF in the VPLMN detects that hSMF1 in SMF set B of the HPLMN has failed, the vSMF triggers an SM context release to the AMF, which then triggers PDU session reactivation. However, if the PDU reactivation selects an SMF in a different SMF set, a ghost session may exist in SMF set B.

[0158] Depending on the embodiment, if the H-UPF does not release the context associated with the failed hSMF1 (i.e., the H-UPF considers hSMF1 to be in the SMF set), downlink data is sent to the V-UPF (Visited V-UPF), but if the vSMF releases the associated context, a GTP-U (GPRS (General-Purpose Packet Radio Service) Tunneling Protocol for User Planes) error indication is returned. The H-UPF may send the error indication report to other available hSMFs in SMF set B. The behavior of the hSMF is implementation-dependent. The hSMF may or may not trigger context cleanup in the PCF and other 5GC NFs within the HPLMN.

[0159] The message shown in Figure 6 may be the same as, or similar to, the corresponding message described in 3GPP® TS 23.502 V17.2.1 (whose disclosure is incorporated herein by standard in its entirety).

[0160] To overcome or mitigate at least one of the aforementioned problems or other issues, it is proposed to introduce roaming resilience indicators and recovery indicators to negotiate capabilities between VPLMN and HPLMN so that V-SMF and H-SMF can make decisions based on peer capability when a V-SMF or H-SMF failure occurs.

[0161] According to one embodiment, V-SMF introduces a "vSMF roaming resilience indication," which means that V-SMF supports SMF set-based roaming resilience, including both a local set for V-SMF and a peer set for H-SMF.

[0162] According to one embodiment, H-SMF introduces an "hSMF roaming resilience indication," which means that it supports SMF set-based roaming resilience, including both a local set for H-SMF and a peer set for V-SMF.

[0163] According to one embodiment, a "vSMF recovery indication" is introduced, which means the ability to support PDU session restoration (recovery) in the event of a V-SMF failure. This requires that AMF, V-SMF, and H-SMF all support the ability to function in the event of a V-SMF failure, enabling PDU session recovery.

[0164] According to one embodiment, if the above indication is not included in the request / response message and SMF profile, the corresponding capability for roaming interworking will not be supported, and therefore should be addressed.

[0165] According to one embodiment, V-SMF and H-SMF can exchange (send and receive) information when their resource contexts are exclusively bound to a specific NF service instance, i.e., when they lack resilience, which can be achieved by the following alternatives, as described below.

[0166] According to one embodiment, through an NF service discovery procedure for SMF selection, the AMF can determine whether the resources served by a candidate V-SMF or H-SMF are exclusively bound to a particular NF service instance, i.e., whether they are unresilient in the event of failure. The AMF is then proposed to populate (input) this information to the V-SMF and H-SMF, for example, into new attributes in an SmContext creation request to the V-SMF, which may preferably be called vSmfNoResilence and hsmfNoResilence, which may be defined as Boolean data, defaulting to 0, and the V-SMF then forwards these new attributes to the H-SMF in a PDU session creation request.

[0167] According to one embodiment, V-SMF includes a new vSmfNoResilence in the PDU session creation request message, and H-SMF includes a new hsmfNoResilence in the corresponding response message.

[0168] The proposed solution provides peer SMF clear information if an SMF set is supported (at least for re-selection in case of peer failure) and if the resources it contains can be shared by at least one alternative SMF.

[0169] The subject matter described herein can be implemented in any suitable type of system using any preferred components, but the embodiments disclosed herein are described with respect to a communication system conforming to the exemplary system architecture shown in Figure 7. For simplicity, the system architecture in Figure 7 shows only some exemplary elements. In practice, the communication system may further include any additional elements suitable for facilitating communication between terminal devices, or between a wireless device and another communication device, such as a fixed telephone, a service provider, or any other network node or terminal device. The communication system can provide communication and various types of services to one or more terminal devices to facilitate access by terminal devices to and / or use of services provided by or through the communication system.

[0170] Figure 7 schematically illustrates a roaming 5G system architecture according to an embodiment of the present disclosure. The architecture in Figure 7 is identical to Figure 4.2.4-1 described in 3GPP® TS 23.501 V17.2.0, the disclosure of which is incorporated herein by standard. The system architecture in Figure 7 may include several exemplary elements such as AUSF, AMF, DN (Data Network), NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, UE, (R)AN, SCP (Service Communications Proxy), NSACF (Network Slice Admission Control Function), vSEPP (Visited Security Edge Protection Proxy), and hSEPP (Home Security Edge Protection Proxy).

[0171] According to an exemplary embodiment, the UE can establish a signaling connection with the AMF via reference point N1, as shown in Figure 7. This signaling connection includes a signaling connection between the UE and (R)AN and an N2 connection between (R)AN and the AMF for this UE, which can enable NAS (Non-Access Layer) signaling exchange between the UE and the core network. (R)AN can communicate with the UPF on reference point N3. The UE can establish a protocol data unit (PDU) session to the DN (Data Network, e.g., Operator Network or Internet) via the UPF through reference point N6.

[0172] As further shown in Figure 7, the exemplary system architecture also includes service-based interfaces such as Nnrf, Nnef, Nausf, Nudm, Npcf, Namf, Nnsacf, and Nsmf, indicated by NFs such as NRF, NEF, AUSF, UDM, PCF, AMF, NSACF, and SMF. In addition, Figure 7 also shows several reference points such as N1, N2, N3, N4, N6, N32, and N9, which can support interactions between NF services in the NF. For example, these reference points can be realized by specifying several NF service consumers and providers and their interactions through the corresponding NF service-based interfaces in order to perform a particular system procedure.

[0173] The various NFs shown in Figure 7 may be responsible for functions such as session management, mobility management, authentication, and security. AUSF, AMF, DN, NEF, NRF, NSSF, PCF, SMF, UDM, UPF, AF, UE, (R)AN, SCP, and NSACF may include functions as defined, for example, in section 6.2 of 3GPP® TS 23.501 V17.2.0.

[0174] Figure 8 shows a flowchart of a method according to an embodiment of the present disclosure, which may be performed by a device that is implemented within an Access and Mobility Function (AMF), implemented in the same location as an AMF, implemented as an AMF, or communicatively coupled to an AMF. Thus, the device may provide means or modules for achieving various parts of Method 800, as well as means or modules for achieving other processes in conjunction with other components.

[0175] In block 802, the AMF may obtain first information regarding whether the first session management function (SMF) supports the first capability of protocol data unit (PDU) session recovery in the event of a failure of the first SMF.

[0176] For example, the first capability could mean the ability to support PDU session recovery in the event of a V-SMF failure.

[0177] The AMF can obtain the first information in various ways. For example, the first SMF may register the first information with the NRF. In this case, the AMF can obtain the first information through NRF discovery. As another example, the AMF can obtain the first information from the first SMF if the first SMF can send a message containing the first information to the AMF. As yet another example, the first information may be pre-configured in the network.

[0178] In block 804, the AMF may obtain second information about whether the second SMF supports the first capability.

[0179] The AMF can obtain the second information in various ways. For example, a second SMF may register the second information with the NRF. In this case, the AMF can obtain the second information through NRF discovery. As another example, the AMF can obtain the second information from the second SMF if the second SMF can send a message containing the second information to the AMF. As yet another example, the second information may be pre-configured in the network.

[0180] In block 806, the AMF may send a PDU session creation session management (SM) context request to a first SMF. If the AMF, the first SMF, and the second SMF support the first capability, the PDU session creation SM context request includes a first indication that supports the first capability.

[0181] A PDU session creation SM context request can create an AMF-SMF association to support a PDU session. According to one embodiment, a PDU session creation SM context request may be identical or similar to an Nsmf_PDUSession_CreateSMContext request, as described in 3GPP® TS 23.502 V17.2.1.

[0182] According to one embodiment, if any one of the AMF, the first SMF, or the second SMF does not support the first capability, the first indication is not included in the PDU session creation SM context request.

[0183] Figure 9 shows a flowchart illustrating how to obtain first information about whether the first SMF supports the first capability according to an embodiment of the present disclosure.

[0184] According to one embodiment, the first SMF can register the first information in the NRF.

[0185] In block 902, the AMF may send a Network Function (NF) discovery request to the Network Repository Function (NRF).

[0186] In block 904, the AMF may receive an NF discovery response containing first information from the NRF.

[0187] According to one embodiment, the NF Discovery Request / Response may be the same as the Nnrf_NFDiscovery_Request and Nnrf_NFDiscovery_Request Response, as described in 3GPP® TS 23.502 V17.2.1.

[0188] Figure 10 shows a flowchart illustrating how to obtain second information regarding whether a second SMF supports the first capability, according to an embodiment of the present disclosure.

[0189] According to one embodiment, the second SMF can register the second information in the NRF.

[0190] In block 1002, the AMF may send a network function (NF) discovery request to the network repository function (NRF).

[0191] In block 1004, the AMF may receive an NF discovery response from the NRF containing second information.

[0192] According to one embodiment, the NF Discovery Request / Response may be the same as the Nnrf_NFDiscovery_Request and Nnrf_NFDiscovery_Request Response, as described in 3GPP® TS 23.502 V17.2.1.

[0193] Figure 11 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device that is implemented inside the AMF, implemented in the same location as the AMF, implemented as the AMF, or communicatively coupled to the AMF. Thus, the device may provide means or modules for achieving various parts of Method 1100, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0194] In block 1102, the AMF may obtain first information regarding whether the first SMF supports the first capability for PDU session recovery in the event of a failure of the first SMF.

[0195] In block 1104, the AMF may obtain second information regarding whether the second SMF supports the first capability.

[0196] In block 1106, the AMF may send a PDU session creation SM context request to a first SMF. If the AMF, the first SMF, and the second SMF support the first capability, the PDU session creation SM context request includes a first indication that supports the first capability.

[0197] In block 1108, the AMF may receive a PDU session creation SM context response from the first SMF. If the first SMF supports the first capability, the PDU session creation SM context response includes the first indication. If the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF, the PDU session creation SM context response includes an indication that the first SMF supports the local NF set for the first SMF and the peer NF set for the second SMF.

[0198] In addition, according to other embodiments, the AMF may obtain the first indication and the indication that the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF in other ways, for example via NRF discovery, so the PDU session creation SM context response may not include the first indication and the indication that the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF.

[0199] According to one embodiment, if the first SMF supports a local NF set for the first SMF, it may mean that the first SMF supports SMF set-based non-roaming PDU session resilience. For example, if the first SMF is a V-SMF and the first SMF supports a local SMF set for a user or UE in the VPLMN, it means that the first SMF supports SMF set-based non-roaming PDU session resilience.

[0200] According to one embodiment, if the first SMF supports a peer NF set of the second SMF, it may mean that the first SMF supports SMF set-based roaming PDU session resilience. For example, if the first SMF is a V-SMF and the first SMF supports a peer SMF set for a user or UE in HPLMN, it means that the first SMF supports SMF set-based roaming PDU session resilience.

[0201] According to one embodiment, if the first SMF supports a local NF set for the first SMF, it may mean that the first SMF supports SMF set-based PDU session resilience, and PDU sessions are established using the first SMF without other SMFs in other networks or network slices.

[0202] According to one embodiment, if the first SMF supports the peer NF set of the second SMF, it may mean that the first SMF supports SMF set-based PDU session resilience and that a PDU session is established with the first SMF and the second SMF.

[0203] Figure 12 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device that is implemented inside the AMF, implemented in the same location as the AMF, implemented as the AMF, or communicatively coupled to the AMF. Thus, the device may provide means or modules for achieving various parts of Method 1200, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0204] In block 1202, the AMF may obtain third information about whether the first SMF supports the peer NF set for the second SMF.

[0205] According to one embodiment, the AMF may obtain third information regarding whether the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF.

[0206] The AMF can obtain the third information in various ways. For example, the first SMF can register the third information with the NRF. In this case, the AMF can obtain the third information through NRF discovery. As another example, the AMF can obtain the third information from the first SMF if the first SMF can send a message containing the third information to the AMF. As yet another example, the third information may be pre-configured in the network.

[0207] In block 1204, the AMF may obtain a fourth piece of information regarding whether the second SMF supports the peer NF set for the first SMF.

[0208] According to one embodiment, the AMF may obtain a fourth piece of information regarding whether the second SMF supports the local network functions (NFs) configured for the second SMF and the peer NF set configured for the first SMF.

[0209] According to one embodiment, if the second SMF supports a local NF set for the second SMF, it may mean that the second SMF supports SMF set-based non-roaming PDU session resilience. For example, if the second SMF is an H-SMF, the second SMF supports a local SMF set for users or UEs within the HPLMN. This means that the second SMF supports SMF set-based non-roaming PDU session resilience.

[0210] According to one embodiment, if the second SMF supports the peer NF set of the first SMF, it may mean that the second SMF supports SMF set-based roaming PDU session resilience. For example, if the second SMF is an H-SMF, the second SMF supports the peer SMF set for users or UEs in the VPLMN. This means that the second SMF supports SMF set-based roaming PDU session resilience.

[0211] According to one embodiment, if the second SMF supports a local NF set for the second SMF, it may mean that the second SMF supports SMF set-based PDU session resilience, and PDU sessions are established with the second SMF without other SMFs in other networks or network slices.

[0212] According to one embodiment, if the second SMF supports the peer NF set of the first SMF, it may mean that the second SMF supports SMF set-based PDU session resilience and that a PDU session is established with both the first SMF and the second SMF.

[0213] The AMF can obtain the fourth information in various ways. For example, a second SMF may register the fourth information with the NRF. In this case, the AMF can obtain the fourth information through NRF discovery. As another example, the AMF can obtain the fourth information from the second SMF if the second SMF can send a message containing the fourth information to the AMF. As yet another example, the fourth information may be pre-configured in the network.

[0214] In block 1206, the AMF may send a PDU session creation session management (SM) context request to the first SMF, which includes third and / or fourth information.

[0215] According to one embodiment, the third piece of information is of Boolean type, and / or the fourth piece of information is of Boolean type.

[0216] For example, the third piece of information may preferably be called vSmfNoResilence. The fourth piece of information may preferably be called smfNoResilence. The third piece of information may be defined as a Boolean type. The default value is 0. The fourth piece of information may be defined as a Boolean type. The default value is 0.

[0217] Figure 13 shows a flowchart illustrating a third piece of information obtained according to an embodiment of the present disclosure, regarding whether the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF.

[0218] According to one embodiment, the first SMF can register the third information in the NRF.

[0219] In block 1302, the AMF may send a Network Function (NF) discovery request to the Network Repository Function (NRF).

[0220] In block 1304, the AMF may receive an NF discovery response from the NRF that includes third information.

[0221] According to one embodiment, the NF Discovery Request / Response may be the same as the Nnrf_NFDiscovery_Request and Nnrf_NFDiscovery_Request Response, as described in 3GPP® TS 23.502 V17.2.1.

[0222] Figure 14 shows a flowchart illustrating a fourth piece of information obtained by an embodiment of the present disclosure regarding whether the second SMF supports a local NF set for the second SMF and a peer NF set for the first SMF.

[0223] According to one embodiment, the second SMF can register the fourth information in the NRF.

[0224] In block 1402, the AMF may send a Network Function (NF) discovery request to the Network Repository Function (NRF).

[0225] In block 1404, the AMF may receive an NF discovery response from the NRF containing a fourth piece of information.

[0226] According to one embodiment, the NF Discovery Request / Response may be the same as the Nnrf_NFDiscovery_Request and Nnrf_NFDiscovery_Request Response, as described in 3GPP® TS 23.502 V17.2.1.

[0227] Figure 15 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device that is implemented inside the AMF, implemented in the same location as the AMF, implemented as the AMF, or communicatively coupled to the AMF. Thus, the device may provide means or modules for achieving various parts of Method 1500, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0228] According to one embodiment, the AMF, the first SMF, and the second SMF support the first capability. The first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF. The second SMF does not support a local NF set for the second SMF or a peer NF set for the first SMF.

[0229] In block 1502, the AMF may detect that the first SMF has failed when receiving notifications from the NRF or when using PING frames. The AMF may receive an NF status notification request from the NRF that contains information indicating that the first SMF has failed. For example, the NF status notification request may be an Nnrf_NFManagement_NFStatusNotify request, as described in 3GPP® TS 23.502 V17.2.1.

[0230] In block 1504, the AMF may re-select an SMF to replace the first SMF in the peer NF set.

[0231] In block 1506, the AMF may send a PDU session update SM context request to the SMF to replace the first SMF. The PDU session update SM context request may be an Nsmf_PDUSession_UpdateSMContext request, as described in 3GPP® TS 23.502 V17.2.1.

[0232] According to one embodiment, the AMF includes a vSMF recovery indicator in a CreateSMContext request to the selected V-SMF, and the V-SMF includes a vSMF roaming resilience indicator and a vSMF recovery indicator in a PDUSessionCreateRequest to the H-SMF.

[0233] According to one embodiment, when a first SMF failure occurs, the second SMF maintains the associated PDU session and waits for recovery. The AMF triggers a first SMF reselection for the established SM context in an update request to trigger recovery, and the reselected first SMF includes updated vSMFId and vSmfPduSessionUri in an update request directed to the second SMF.

[0234] Figure 16 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented in or at the same location as the AMF, or implemented as the AMF, or communicatively coupled to the AMF. Thus, the device may provide means or modules for achieving various parts of Method 1600, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0235] According to one embodiment, the AMF, the first SMF, and the second SMF support the first capability. The first SMF supports a local NF set for the first SMF but does not support a peer NF set for the second SMF. The second SMF supports a local NF set for the second SMF and a peer NF set for the first SMF.

[0236] In block 1602, the AMF may detect that the first SMF has failed when receiving a notification from the NRF or when using a PING frame.

[0237] In block 1604, the AMF may re-select an SMF to replace the first SMF.

[0238] In block 1606, the AMF can send an SM context creation request to the SMF in order to re-establish the PDU session.

[0239] According to one embodiment, if an SMF for replacing a first SMF supports the first capability, the PDU session creation SM context request includes the first indication.

[0240] According to one embodiment, the SM context creation request includes information on whether the re-selected SMF supports the peer NF set of the second SMF, and / or whether the second SMF supports the peer NF set of the re-selected SMF.

[0241] According to one embodiment, the AMF includes the vSMF recovery indicator in the CreateSMContext request for the selected vSMF. The V-SMF forwards the received vSMF recovery indicator in the PDUSessionCreateRequest to the H-SMF, but does not include the vSMF roaming resilience indicator in the V-SMF because the vSMF does not support SMF sets.

[0242] According to one embodiment, if a failure occurs in the selected V-SMF, the H-SMF maintains the associated PDU sessions and waits for the vSMF to recover. The AMF triggers PDU session reactivation to recover the affected PDU sessions, and the re-selected V-SMF sends a PDUSessionCreateRequest to the original H-SMF. The H-SMF performs a Create on Create process to accept the new PDU session request.

[0243] Figure 17 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device that is implemented inside the AMF, implemented in the same location as the AMF, implemented as the AMF, or communicatively coupled to the AMF. Thus, the device may provide means or modules for achieving various parts of Method 1700, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0244] According to one embodiment, the AMF, the first SMF, and the second SMF support the first capability. The first SMF supports a local NF set for the first SMF but does not support a peer NF set for the second SMF. The second SMF does not support a local NF set for the second SMF or a peer NF set for the first SMF.

[0245] In block 1702, the AMF may detect that the first SMF has failed when receiving a notification from the NRF or when using a PING frame.

[0246] In block 1704, the AMF may re-select an SMF to replace the first SMF.

[0247] In block 1706, the AMF can send an SM context creation request to the SMF to re - establish a PDU session.

[0248] According to one embodiment, the SM context creation request includes information on whether the re - selected SMF supports the peer NF set of the second SMF, and / or information on whether the second SMF supports the peer NF set of the re - selected SMF.

[0249] According to one embodiment, when the SMF for replacing the first SMF supports the first capability, the PDU session creation SM context request includes the first indication.

[0250] FIG. 18 shows a flowchart of a method according to another embodiment of the present disclosure, which can be implemented within the AMF, implemented at the same location as the AMF, implemented as the AMF, or executed by a device communicatively coupled to the AMF. Thus, the device can provide means or modules for achieving various parts of method 1800, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments are omitted for brevity.

[0251] According to one embodiment, the first SMF does not support the first capability. The first SMF does not support the local NF set for the first SMF and the peer NF set for the second SMF. The second SMF supports the local NF set for the second SMF and the peer NF set for the first SMF.

[0252] In block 1802, the AMF can receive a PDU session SM context status notification including the release (liberation) and the set resource state, and the cause of the release due to re - activation from the first SMF.

[0253] In block 1804, the AMF may send an SM context creation request to the first SMF in order to re-establish the PDU session.

[0254] According to one embodiment, the SM context creation request includes information on whether the first SMF supports the peer NF set of the reselected second SMF, and / or information on whether the reselected second SMF supports the peer NF set of the first SMF.

[0255] Figure 19 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside the AMF, implemented in the same location as the AMF, implemented as the AMF, or communicatively coupled to the AMF. Thus, the device may provide means or modules for achieving various parts of Method 1900, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0256] According to one embodiment, the AMF, the first SMF, and the second SMF support the first capability. The first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF. The second SMF supports a local NF set for the second SMF but does not support a peer NF set for the first SMF.

[0257] In block 1902, the AMF may receive a PDU session SM context status notification that includes the resource state set to release and the cause of the release due to reactivation from the first SMF.

[0258] In block 1904, the AMF may send an SM context creation request to the first SMF in order to re-establish the PDU session.

[0259] According to one embodiment, the SM context creation request includes information on whether the first SMF supports the peer NF set of the reselected second SMF, and / or information on whether the reselected second SMF supports the peer NF set of the first SMF.

[0260] According to one embodiment, if the AMF, the first SMF, and the re-selected SMF to replace the second SMF support the first capability, the PDU session creation SM context request includes the first indication.

[0261] Figure 20a shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device that is implemented inside the AMF, implemented in the same location as the AMF, implemented as the AMF, or communicatively coupled to the AMF. Thus, the device may provide means or modules for achieving various parts of Method 2000, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0262] According to one embodiment, the first SMF does not support the first capability. The first SMF does not support a local NF set for the first SMF and a peer NF set for the second SMF. The second SMF supports a local NF set for the second SMF but does not support a peer NF set for the first SMF.

[0263] In block 2002, the AMF may receive a PDU session SM context status notification that includes the resource state set to release and the cause of the release due to reactivation from the first SMF.

[0264] In block 2004, the AMF may send a request to the first SMF to create an SM context in order to re-establish the PDU session.

[0265] According to one embodiment, the SM context creation request includes information on whether the first SMF supports the peer NF set of the reselected second SMF, and / or information on whether the reselected second SMF supports the peer NF set of the first SMF.

[0266] According to one embodiment, the first SMF is a visited SMF, and the second SMF is a home SMF.

[0267] According to one embodiment, the first SMF is an intermediate SMF, and the second SMF is an anchor SMF.

[0268] Figure 20b shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside the AMF, implemented in the same location as the AMF, implemented as the AMF, or communicatively coupled to the AMF. Thus, the device may provide means or modules for achieving various parts of Method 2010, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0269] In block 2012, the AMF may obtain a fifth piece of information regarding whether there are two or more SMFs in the peer NF set for the first SMF.

[0270] In block 2014, the AMF may obtain a sixth piece of information regarding whether there are two or more SMFs in the peer NF set for the second SMF.

[0271] In block 2016, the AMF may send a PDU SM context request to the first SMF containing the fifth and / or sixth pieces of information.

[0272] According to one embodiment, the third information and the sixth information are represented by a single parameter, and the fourth information and the fifth information are represented by a single parameter.

[0273] For example, the roaming resilience indication should actually mean supporting the local set and the peer set. What is new is the indication that there are multiple vSMFs within the same vSMF set and multiple hSMFs within the same hSMF set. The AMF discovers that there are multiple vSMFs within the same vSMF set and / or multiple hSMFs within the hSMF set, and such information is sent by the AMF to the vSMF. Such information may be referred to as the vSMF set indication and the hSMF set indication. The vSMF relays the vSMF set indication to the hSMF.

[0274] FIG. 21a shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented inside the first SMF, implemented at the same location as the first SMF, implemented as the first SMF, or executed by a device communicatively coupled to the first SMF. Accordingly, the apparatus may provide means or modules for achieving various parts of method 2100, as well as means or modules for achieving other processing in conjunction with other components. Note that the description of some parts described in the above embodiments is omitted for the sake of brevity.

[0275] In block 2102, the first SMF may receive a PDU session creation SM context request from an access and mobility function (AMF).

[0276] In block 2104, the first SMF may send a PDU session creation request to the second SMF.

[0277] In block 2106, the first SMF can receive a PDU session creation response from the second SMF.

[0278] According to one embodiment, if the AMF, the first SMF, and the second SMF support a first capability for PDU session recovery in the event of a failure of the first SMF, the PDU session creation SM context request includes a first indication that supports the first capability.

[0279] According to one embodiment, if the AMF, the first SMF, and the second SMF support the first capability, the PDU session creation request includes the first indication.

[0280] According to one embodiment, if the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF, the PDU session creation request further includes an indication that the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF.

[0281] According to one embodiment, if the AMF, the first SMF, and the second SMF support the first capability, the PDU session creation response includes the first indication.

[0282] According to one embodiment, a first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF, and a second SMF supports a local NF set for the second SMF and a peer NF set for the first SMF, and the PDU session creation response includes an indication that the second SMF supports a local NF set for the second SMF and a peer NF set for the first SMF.

[0283] According to one embodiment, if any one of the AMF, the first SMF, or the second SMF does not support the first capability, the first indication is not included in the PDU session creation SM context request.

[0284] According to one embodiment, if the second SMF supports the peer NF set of the first SMF, the PDU session creation response includes an indication that the second SMF supports the peer NF set for the first SMF.

[0285] According to one embodiment, the PDU session creation SM context request includes third information regarding whether the first session management function (SMF) supports a set of peer network functions (NFs) for the second SMF, and / or fourth information regarding whether the second SMF supports a set of peer NFs for the first SMF, and the PDU session creation request includes the third information and / or the fourth information.

[0286] According to one embodiment, a PDU session creation request includes information on whether the first SMF supports peer SMF reselection within the peer SMF set in the event of a failure of the original peer SMF instance.

[0287] According to one embodiment, the PDU session creation response includes information on whether the second SMF supports peer SMF reselection within the peer SMF set if the original peer SMF instance fails.

[0288] According to some embodiments, in order to ensure that roaming resilience operates end-to-end, it is necessary that both vSMF and hSMF support their own SMF set and peer SMF set.

[0289] According to some embodiments, it may refer to its own SMF set as a "roaming resilience indication" and its peer SMF set as a "peer v / h SMF set support indication".

[0290] The meaning of one's own SMF set ("Roaming Resilience Indication") has two aspects: (1) it supports the replication / backup of its session context in other SMF instances of the same set, and (2) it is itself deployed in an SMF set (multiple SMF instances available in the SMF pool so that context replication / switchover can occur after an SMF failure). When AMF discovers vSMF and hSMF, it can detect whether there are multiple instances in the same SMF set / pool.

[0291] The significance of the "Peer SMF Set Support Indication" is somewhat simple. In short, SMF supports the re-selection of peer SMFs within a peer SMF set when the original SMF instance fails.

[0292] Based on this, AMF sends both the "vSMF roaming resilience indication" (its own vSMF set) and the "hSMF roaming resilience indication" (its own hSMF set) to vSMF in the SM context creation request, and vSMF relays this information to hSMF. In such an exchange, vSMF knows whether the peer hSMF is deployed to the SMF set, and hSMF knows whether vSMF is deployed to the SMF set. Note that the "hSMF roaming resilience indication" is somewhat redundant information between the vSMF and hSMF interfaces, as vSMF has already learned it from AMF in the SM context creation request. However, there is no problem in conveying that information in the PDU creation request / response.

[0293] According to one embodiment, the third piece of information is of Boolean type, and / or the fourth piece of information is of Boolean type.

[0294] According to one embodiment, the PDU session creation SM context request includes a fifth piece of information about whether there are two or more SMFs in the peer NF set for a first SMF, and / or a sixth piece of information about whether there are two or more SMFs in the peer NF set for a second SMF, and the PDU session creation request includes the fifth piece of information and / or the sixth piece of information.

[0295] According to one embodiment, the third and sixth pieces of information are represented by a single parameter, and the fourth and fifth pieces of information are represented by a single parameter.

[0296] For example, roaming resilience indication should, in practice, mean supporting local and peer sets. A new addition would be an indication that there are multiple vSMFs within the same vSMF set and multiple hSMFs within the same hSMF set. vSMFs and hSMFs themselves can also detect such information, and vSMFs and hSMFs can discover other members within the same set based on their own implementation mechanisms, and then vSMFs and hSMFs can exchange such information.

[0297] Furthermore, the concepts of "vSMF set indication" and "hSMF set indication" can be extended to encompass the meanings of "vSMF roaming resilience indication" and "hSMF roaming resilience indication." It is simply necessary to send and receive "vSMF set indication" and "hSMF set indication." This is actually easy and logical to implement, as vSMF set indication is based on vSMF resilience indication in any case, and similar processing applies to hSMF. This solution essentially replaces parameter name resilience indication with set indication, and extends the concept so that "set indication" means supporting local sets, peer sets, and multiple members within the same set.

[0298] Figure 21b shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside the first SMF, implemented in the same location as the first SMF, implemented as the first SMF, or communicatively coupled to the first SMF. Thus, the device may provide means or modules for achieving various parts of method 2100, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0299] In block 2112, the first SMF may determine a sixth piece of information regarding whether there are two or more SMFs in the peer NF set for the second SMF. The PDU session creation request includes this sixth piece of information.

[0300] According to one embodiment, the PDU session creation response includes a fifth piece of information regarding whether there are two or more SMFs in the peer NF set for the first SMF.

[0301] Figure 22 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside the first SMF, implemented in the same location as the first SMF, implemented as the first SMF, or communicatively coupled to the first SMF. Thus, the device may provide means or modules for achieving various parts of Method 2200, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0302] In block 2202, the first SMF may send a network function (NF) registration request to the NRF, which includes the NF profile of the first SMF.

[0303] According to one embodiment, the NF profile of the first SMF includes an indication of whether the first SMF supports the ability to recover PDU sessions in the event of a failure of the first SMF.

[0304] According to one embodiment, the NF profile of the first SMF includes an indication of whether the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF.

[0305] According to one embodiment, the NF profile of the first SMF includes an indication of whether the first SMF supports a peer NF set for the second SMF (e.g., vSMF roaming resilience indication).

[0306] Figure 23 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside the first SMF, implemented in the same location as the first SMF, implemented as the first SMF, or communicatively coupled to the first SMF. Thus, the device may provide means or modules for achieving various parts of Method 2300, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0307] In block 2302, the first SMF may receive a PDU session creation SM context request from the Access and Mobility Function (AMF). Block 2302 is the same as block 2102.

[0308] In block 2304, the first SMF can send a PDU session creation SM context response to the AMF.

[0309] According to one embodiment, if the first SMF supports the first capability, the PDU session creation SM context response includes the first indication.

[0310] According to one embodiment, if the first SMF supports an NF set for the first SMF and a peer NF set for the second SMF, the PDU session creation SM context response includes an indication that the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF.

[0311] In block 2306, the first SMF can send a PDU session creation request to the second SMF. Block 2306 is the same as block 2104.

[0312] In block 2308, the first SMF can receive a PDU session creation response from the second SMF. Block 2308 is the same as block 2106.

[0313] Figure 24 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside the first SMF, implemented in the same location as the first SMF, implemented as the first SMF, or communicatively coupled to the first SMF. Thus, the device may provide means or modules for achieving various parts of Method 2400, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0314] According to one embodiment, the first SMF does not support the first capability. The first SMF does not support a local NF set for the first SMF and a peer NF set for the second SMF. The second SMF supports a local NF set for the second SMF and a peer NF set for the first SMF.

[0315] In block 2402, the first SMF may receive an NF status notification request from the NRF containing information indicating that the second SMF has failed. Alternatively, the first SMF may detect that the second SMF has failed via a PING frame or any other suitable method.

[0316] In block 2404, the first SMF may send a PDU session SM context status notification that includes the resource state set to be released and the reason for the release due to reactivation to the AMF.

[0317] In block 2406, the first SMF can receive a PDU session creation SM context request from the AMF.

[0318] In block 2408, the first SMF may send a PDU session creation request to the re-selected SMF to replace the second SMF.

[0319] Figure 25 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside the first SMF, implemented in the same location as the first SMF, implemented as the first SMF, or communicatively coupled to the first SMF. Thus, the device may provide means or modules for achieving various parts of Method 2500, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0320] According to one embodiment, the AMF, the first SMF, and the second SMF support the first capability. The first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF. The second SMF supports a local NF set for the second SMF but does not support a peer NF set for the first SMF.

[0321] In block 2502, the first SMF may receive an NF status notification request from the NRF that contains information indicating that the second SMF has failed.

[0322] In block 2504, the first SMF may send a PDU session SM context status notification that includes the resource state set to be released and the reason for the release due to reactivation to the AMF.

[0323] In block 2506, the first SMF can receive a PDU session creation SM context request from the AMF. If the AMF, the first SMF, and the SMF re-selected to replace the second SMF support the first capability, the PDU session creation SM context request includes the first indication.

[0324] In block 2508, the first SMF may send a PDU session creation request to the re-selected SMF. The PDU session creation request includes an indication that the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF. If the AMF, the first SMF, and the re-selected SMF to replace the second SMF support the first capability, the PDU session creation request includes the first indication.

[0325] In block 2510, the first SMF may receive a PDU session creation response from the re-selected SMF. If the AMF, the first SMF, and the re-selected SMF support the first capability, the PDU session creation response may include the first indication.

[0326] Figure 26 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside the first SMF, implemented in the same location as the first SMF, implemented as the first SMF, or communicatively coupled to the first SMF. Thus, the device may provide means or modules for achieving various parts of Method 2600, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0327] According to one embodiment, the first SMF does not support the first capability. The first SMF does not support a local NF set for the first SMF and a peer NF set for the second SMF. The second SMF supports a local NF set for the second SMF but does not support a peer NF set for the first SMF.

[0328] In block 2602, the first SMF may receive an NF status notification request from the NRF that contains information indicating that the second SMF has failed.

[0329] In block 2604, the first SMF may send a PDU session SM context status notification that includes the resource state set to be released and the reason for the release due to reactivation to the AMF.

[0330] In block 2606, the first SMF can receive a PDU session creation SM context request from the AMF.

[0331] In block 2608, the first SMF may send a PDU session creation request to the re-selected SMF to replace the second SMF.

[0332] According to one embodiment, the first SMF is a visited SMF and the second SMF is a home SMF, or the first SMF is an intermediate SMF and the second SMF is an anchor SMF.

[0333] Figure 27a shows a flowchart of a method according to another embodiment of the present disclosure. This flowchart can be executed or communicated by a device implemented within or as a second SMF. Thus, the device may provide means or modules for achieving various parts of Method 2700, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments are omitted for brevity.

[0334] In block 2702, the second SMF may receive a PDU session creation request from the first SMF.

[0335] In block 2704, the second SMF can send a PDU session creation response to the first SMF.

[0336] According to one embodiment, if the AMF, the first SMF, and the second SMF support a first capability for PDU session recovery in the event of a failure of the first SMF, then a PDU session creation request includes a first indication that supports the first capability.

[0337] According to one embodiment, if the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF, the PDU session creation request further includes an indication that the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF.

[0338] According to one embodiment, if the AMF, the first SMF, and the second SMF support the first capability, the PDU session creation response includes the first indication.

[0339] According to one embodiment, if the first SMF supports the local NF set of the first SMF and the peer NF set of the second SMF, and the second SMF supports the local NF set of the second SMF and the peer NF set of the first SMF, the PDU session creation response includes an indication that the second SMF supports the local NF set of the second SMF and the peer NF set of the first SMF.

[0340] According to one embodiment, if the second SMF supports the peer NF set of the first SMF, the PDU session creation response includes an indication that the second SMF supports the peer NF set of the first SMF.

[0341] According to one embodiment, a PDU session creation request includes third information regarding whether the first SMF supports the peer NF set of the second SMF, and / or fourth information regarding whether the second SMF supports the peer NF set of the first SMF.

[0342] According to one embodiment, a PDU session creation request includes a fifth piece of information regarding whether there are two or more SMFs in the peer NF set for a first SMF, and / or a sixth piece of information regarding whether there are two or more SMFs in the peer NF set for a second SMF.

[0343] According to one embodiment, the third and sixth pieces of information are represented by a single parameter, and the fourth and fifth pieces of information are represented by a single parameter.

[0344] Figure 27b shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside a second SMF, implemented at the location of a second SMF, implemented as a second SMF, or communicatively coupled to a second SMF. Thus, the device may provide means or modules for achieving various parts of method 2710, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0345] In block 2712, the second SMF may determine a fifth piece of information regarding whether there are two or more SMFs in the peer NF set for the first SMF. The PDU session creation response includes this fifth piece of information.

[0346] According to one embodiment, the PDU session creation request includes a sixth piece of information regarding whether there are two or more SMFs in the peer NF set for the second SMF.

[0347] Figure 28 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device that is implemented inside the second SMF, implemented at the location of the second SMF, implemented as the second SMF, or communicatively coupled to the second SMF. Thus, the device may provide means or modules for achieving various parts of Method 2800, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0348] In block 2802, the second SMF may send an NF registration request to the NRF that includes the NF profile of the second SMF.

[0349] According to one embodiment, the NF profile of the second SMF includes an indication of whether the second SMF supports the ability to recover PDU sessions in the event of a failure of the first SMF.

[0350] According to one embodiment, the NF profile of the second SMF includes an indication of whether the second SMF supports a local NF set for the second SMF and a peer NF set for the first SMF.

[0351] According to one embodiment, the NF profile of the second SMF includes an indication (e.g., an hSMF roaming resilience indication) of whether the second SMF supports the peer NF set for the first SMF.

[0352] Figure 29 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside a second SMF, implemented at the location of a second SMF, implemented as a second SMF, or communicatively coupled to a second SMF. Thus, the device may provide means or modules for achieving various parts of method 2900, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0353] According to one embodiment, the AMF, the first SMF, and the second SMF support a first capability, the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF, and the second SMF does not support a local NF set for the second SMF or a peer NF set for the first SMF.

[0354] In block 2902, the second SMF may receive an NF status notification request from the NRF that contains information indicating that the first SMF has failed.

[0355] In block 2904, the second SMF can maintain at least one PDU session associated with the first SMF.

[0356] In block 2906, the second SMF may receive a PDU session update request from the SMF re-selected to replace the first SMF, which includes an updated SMF identifier and an updated SMF PDU session uniform resource identifier.

[0357] Figure 30 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside a second SMF, implemented at the location of a second SMF, implemented as a second SMF, or communicatively coupled to a second SMF. Thus, the device may provide means or modules for achieving various parts of method 3000, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0358] According to one embodiment, the AMF, the first SMF, and the second SMF support the first capability, the first SMF supports a local NF set for the first SMF but does not support a peer NF set for the second SMF, and the second SMF supports a local NF set for the second SMF and a peer NF set for the first SMF.

[0359] In block 3002, the second SMF may receive an NF status notification request from the NRF that contains information indicating that the first SMF has failed.

[0360] In block 3004, the second SMF can maintain at least one PDU session associated with the first SMF.

[0361] In block 3006, the second SMF can receive a PDU session creation request from the SMF that was re-selected to replace the first SMF.

[0362] According to one embodiment, if the AMF, the SMF re-selected to replace the first SMF, and the second SMF support the first capability, the PDU session creation SM context request includes the first indication.

[0363] In block 3008, the second SMF can perform a create-on-create operation to accept a PDU session creation request.

[0364] In block 3010, the second SMF may send a PDU session creation response to the SMF that has been re-selected to replace the first SMF.

[0365] According to one embodiment, if the AMF, the SMF for replacing the first SMF, and the second SMF support the first capability, the PDU session creation response includes the first indication.

[0366] Figure 31 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed in a second SMF, or as a second SMF, or by a device communicatively coupled to a second SMF. Thus, the device may provide means or modules for achieving various parts of method 3100, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0367] According to one embodiment, the AMF, the first SMF, and the second SMF support the first capability, the first SMF supports a local NF set for the first SMF but does not support a peer NF set for the second SMF, and the second SMF does not support a local NF set for the second SMF or a peer NF set for the first SMF.

[0368] In block 3102, the second SMF may receive an NF status notification request from the NRF that contains information indicating that the first SMF has failed.

[0369] In block 3104, the second SMF can maintain at least one PDU session associated with the first SMF.

[0370] In block 3106, the second SMF can receive a PDU session creation request from the SMF that was re-selected to replace the first SMF.

[0371] According to one embodiment, if the AMF, the SMF re-selected to replace the first SMF, and the second SMF support the first capability, the PDU session creation SM context request includes the first indication.

[0372] In block 3108, the second SMF can perform a create-on-create operation to accept a PDU session creation request.

[0373] In block 3110, the second SMF may send a PDU session creation response to the SMF that has been re-selected to replace the first SMF.

[0374] According to one embodiment, if the AMF, the SMF for replacing the first SMF, and the second SMF support the first capability, the PDU session creation response includes the first indication.

[0375] Figure 32 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device that is implemented inside the second SMF, implemented at the location of the second SMF, implemented as the second SMF, or communicatively coupled to the second SMF. Thus, the device may provide means or modules for achieving various parts of method 3200, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0376] According to one embodiment, the first SMF does not support the first capability, the first SMF does not support a local NF set for the first SMF and a peer NF set for the second SMF, and the second SMF supports a local NF set for the second SMF and a peer NF set for the first SMF.

[0377] In block 3202, the second SMF may send a service request to the third network function. The service request does not include an indication that the second SMF supports a local NF set for the second SMF and a peer NF set for the first SMF.

[0378] According to one embodiment, the third network function comprises at least one of the following: a policy control function (PCF), a user plane function (UPF), and an integrated data management (UDM).

[0379] According to one embodiment, the first SMF is a visited SMF, and the second SMF is a home SMF. According to another embodiment, the first SMF is an intermediate SMF, and the second SMF is an anchor SMF.

[0380] Figure 33 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed in a third network function, or as a third network function, or by a device communicatively coupled to a third network function. Thus, the device may provide means or modules for achieving various parts of method 3300, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0381] In block 3302, the third network function may determine that the second SMF does not support a local NF set for the second SMF and a peer NF set for the first SMF.

[0382] In block 3304, if the second SMF fails, the third network function may perform cleanup actions on the resource context associated with the second SMF.

[0383] According to one embodiment, a third network function may determine that a second SMF does not support a local NF set for the second SMF and a peer NF set for the first SMF by sending an NF discovery request to an NRF and receiving an NF discovery response from the NRF. The NF discovery response includes information indicating that the second SMF does not support a local NF set for the second SMF and a peer NF set for the first SMF.

[0384] According to one embodiment, a third network function may determine, by receiving a service request from a second SMF, that the second SMF does not support a local NF set for the second SMF and a peer NF set for the first SMF. The service request does not include any indication that the second SMF supports a local NF set for the second SMF and a peer NF set for the first SMF.

[0385] According to one embodiment, the third network function comprises at least one of the following: a policy control function (PCF), a user plane function (UPF), and an integrated data management (UDM).

[0386] According to one embodiment, the first SMF is a visited SMF and the second SMF is a home SMF, or the first SMF is an intermediate SMF and the second SMF is an anchor SMF.

[0387] Figure 34 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed in or in an NRF, or as an NRF, or by a device communicably coupled to an NRF. Thus, the device may provide means or modules for achieving various parts of Method 3400, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0388] In block 3402, the NRF may receive an NF registration request from the SMF, which includes the SMF's NF profile.

[0389] In block 3404, the NRF can store the NF profile of the SMF.

[0390] According to one embodiment, if the SMF is a first SMF and supports a first capability for PDU session recovery in the event of a failure of the first SMF, the NF profile of the first SMF includes a first indication that supports the first capability.

[0391] According to one embodiment, if SMF is a first SMF and supports a local NF set for the first SMF and a peer NF set for the second SMF, the NF profile of the first SMF includes an indication that the first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF.

[0392] According to one embodiment, if the SMF is a second SMF and supports the first capability, the NF profile of the second SMF includes the first indication.

[0393] According to one embodiment, if the SMF is a second SMF and supports a local NF set for the second SMF and a peer NF set for the first SMF, the NF profile of the second SMF includes an indication that the second SMF supports the local NF set for the second SMF and the peer NF set for the first SMF.

[0394] Figure 35 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device that is implemented inside the NRF, implemented in the same location as the NRF, implemented as an NRF, or communicatively coupled to the NRF. Thus, the device may provide means or modules for achieving various parts of Method 3500, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0395] In block 3502, the NRF may receive network function discovery requests from the Access and Mobility Function (AMF).

[0396] In block 3504, the NRF may send a network function discovery response to the AMF that includes at least one indication of the NF profile of the SMF.

[0397] According to one embodiment, the first SMF is a visited SMF and the second SMF is a home SMF, or the first SMF is an intermediate SMF and the second SMF is an anchor SMF.

[0398] The following explanation focuses on solutions for V-SMF and H-SMF roaming interworking. However, the same solution principles apply to scenarios where I-SMF and anchor SMF have different resilience capabilities or configurations.

[0399] Figure 36 shows a flowchart of a method according to another embodiment of the present disclosure. Some parts described in the above embodiments are omitted for brevity.

[0400] In step 3601, vSMF sends an Nnrf_NFRegister request {vSMF roaming resilience indication, vSMF recovery indication} to vNRF.

[0401] In step 3602, hSMF sends an Nnrf_NFRegister request {hSMF roaming resilience indication, vSMF recovery indication} to hNRF.

[0402] In step 3603, the AMF sends an hSMF discovery request to the hNRF.

[0403] In step 3604, the AMF receives the hSMF roaming resilience indication and the vSMF recovery indication from the hNRF.

[0404] In step 3605, the AMF sends a vSMF discovery request to the vNRF.

[0405] In step 3606, the AMF receives the vSMF roaming resilience indication and the vSMF recovery indication from the vNRF.

[0406] In step 3607, the AMF sends an Nsmf_PDUSession_CreateSMContext request to vSMF1. According to one embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF recovery indicator. According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indicator (which may be a Boolean) and / or an hSMF roaming resilience indicator (which may be a Boolean).

[0407] In step 3608, AMF receives the Nsmf_PDUSession_CreateSMContext response {vSMF roaming resilience indication, vSMF recovery indication} from vSMF1.

[0408] In step 3609, vSMF1 sends an Nsmf_PDUSession_Create request to hSMF1. According to one embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indicator and a vSMF recovery indicator. According to another embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indicator and / or an hSMF roaming resilience indicator.

[0409] In step 3610, vSMF1 receives an Nsmf_PDUSession_Create response from hSMF1. According to one embodiment, the Nsmf_PDUSession_Create response includes an hSMF roaming resilience indication.

[0410] According to one embodiment, the new additions are indications that there are multiple vSMFs within the same vSMF set and multiple hSMFs within the same hSMF set. Solution I: The AMF discovers through discovery that there are multiple vSMFs within the same vSMF set and / or multiple hSMFs within an hSMF set, and such information is sent by the AMF to the vSMF, for example, as a "vSMF set indication" and an "hSMF set indication". The vSMF relays the vSMF set indication to the hSMF. Solution II: vSMF and hSMF themselves can also detect such information. Based on their own implementation mechanisms, vSMF and hSMF can discover other members within the same set through discovery, and vSMF and hSMF can exchange (send and receive) such information. Solution III: Another possibility is to extend the concepts of “vSMF set indication” and “hSMF set indication” to also cover the meanings of “vSMF roaming resilience indication” and “hSMF roaming resilience indication”. This would simply involve exchanging “vSMF set indication” with “hSMF set indication”. This is actually easy and makes sense to do, since vSMF set indication is based on vSMF resilience indication in any case, and the same applies to hSMF. This solution essentially replaces parameter name resilience indication with set indication, and extends the concept so that “set indication” means supporting local sets, peer sets, and multiple members within the same set.

[0411] According to one embodiment, the V-SMF and H-SMF register the ability to support roaming resilience and vSMF recovery in the NRF.

[0412] According to one embodiment, the AMF obtains V-SMF and H-SMF capabilities that support roaming resilience and vSMF recovery via NRF discovery.

[0413] According to one embodiment, if AMF detects both V-SMF and H-SMF, supports vSMF recovery, and AMF also supports vSMF recovery, then AMF includes a vSMF recovery indication in the V-SMF creation request. Otherwise, AMF does not include vSMF recovery.

[0414] According to one embodiment, if the V-SMF supports vSMF recovery, the V-SMF includes a vSMF recovery indication (if received from the AMF) in the creation request to the H-SMF. Note that if the V-SMF supports vSMF recovery, it means that the V-SMF can relay the vSMF recovery indication (received from the AMF) to the H-SMF.

[0415] According to one embodiment, if V-SMF supports SMF sets, V-SMF includes its roaming resilience indication in the creation request to H-SMF. Otherwise, V-SMF does not send the roaming resilience indication to H-SMF.

[0416] According to one embodiment, if AMF detects V-SMF and / or H-SMF support SMF set-based resilience (i.e., roaming resilience indication), and AMF also supports vSMF failure reselection based on the SMF set, AMF includes vSMF resilience indication and / or hSMF resilience indication in the V-SMF creation request. Otherwise, AMF does not include vSMF resilience and / or hSMF resilience indication.

[0417] According to one embodiment, if AMF detects V-SMF and / or H-SMF support SMF set-based resilience (i.e., roaming resilience indication), AMF includes the vSMF resilience indication and / or hSMF resilience indication in the creation request to the V-SMF.

[0418] According to one embodiment, if H-SMF supports SMF sets and V-SMF also includes a roaming resilience indicator in its creation request, H-SMF includes the roaming resilience indicator in its creation response to V-SMF. Otherwise, H-SMF does not send the roaming resilience indicator to V-SMF.

[0419] Countermeasures against V-SMF failures: ● V-SMF supports SMF set function. o H-SMF supports SMF sets: o Follow the normal set handling. o H-SMF does not support SMF sets: If AMF, V-SMF, and H-SMF support vSMF recovery, H-SMF maintains the affected PDU sessions and waits for the recovery to be triggered by AMF re-selecting another vSMF within the same V-SMF set and performing a PDU session refresh procedure. Applicable to V-SMF failure scenario 1. Otherwise, H-SMF deletes the affected PDU session, and AMF requests the UE to reactivate the affected PDU session. ● If V-SMF does not support the SMF set function o Whether H-SMF supports SMF sets or not, If AMF, V-SMF, and H-SMF support vSMF recovery, H-SMF maintains the affected PDU session and waits for recovery triggered by AMF re-selecting another vSMF and performing the PDU session Create on Create procedure. Applicable to V-SMF failure scenarios 2 and 3. Otherwise, H-SMF deletes the affected PDU session, and AMF requests the UE to reactivate the affected PDU session.

[0420] Solutions for H-SMF failure: ● H-SMF supports the SMF set function. V-SMF supports SMF sets. o Follows the normal set handling. V-SMF does not support SMF sets. oV-SMF releases the affected PDU sessions, and AMF requests the UE to reactivate the affected PDU sessions. Applicable to H-SMF failure scenario 4. ● H-SMF does not support the SMF set function. o Regardless of whether V-SMF supports SMF sets, V-SMF releases the affected PDU sessions, and AMF requests the UE to reactivate the affected PDU sessions. Applicable to H-SMF failure scenarios 5 and 6.

[0421] Figure 37 shows a flowchart illustrating an exemplary solution for V-SMF failure according to an embodiment of the present disclosure. Some parts described in the above embodiment are omitted for brevity.

[0422] Scenario 1: VPLMN deploys an SMF set, V-SMF supports the SMF set, and H-SMF does not support the SMF set.

[0423] The AMF includes the vSMF recovery indicator in the CreateSMContext request to the selected V-SMF, and the V-SMF includes the vSMF roaming resilience indicator and the vSMF recovery indicator in the PDUSessionCreateRequest to the H-SMF.

[0424] If the selected V-SMF fails, the H-SMF maintains the associated PDU session and waits for its recovery. The AMF triggers a vSMF re-selection for the established SM context in the update request to trigger recovery, and the re-selected V-SMF includes the updated vSMFId and vSmfPduSessionUri in the update request directed to the original H-SMF.

[0425] In step 3701, AMF sends an Nsmf_PDUSession_CreateSMContext request to vSMF1 and receives a response from vSMF1.

[0426] According to one embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF recovery indication (i.e., vSMF supports PDU session recovery in the case of vSMF failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., vSMF supports roaming resilience) and / or an hSMF roaming resilience indication (i.e., hSMF does not support roaming resilience).

[0427] In step 3702, vSMF1 sends an Nsmf_PDUSession_Create request to hSMF1.

[0428] According to one embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indicator and a vSMF recovery indicator. According to another embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indicator and / or an hSMF roaming resilience indicator received from the AMF.

[0429] In step 3703, vSMF1 receives an Nsmf_PDUSession_Create response from hSMF1. According to one embodiment, the Nsmf_PDUSession_Create response includes a vSMF recovery indication (i.e., hSMF supports PDU session recovery in the event of a vSMF failure).

[0430] In step 3704, the vNRF (Visiting NRF) sends an Nnrf_NFManagement_NFStatusNotify request ("vSMF1 SUSPENDED") to the hSMF1.

[0431] In step 3705, hSMF1 maintains the PDU session associated with the failed vSMF and waits for its recovery.

[0432] In step 3706, vNRF sends an Nnrf_NFManagement_NFStatusNotify request ("vSMF1 SUSPENDED") to AMF.

[0433] In step 3708, the AMF triggers a re-selection of the vSMF for the established SM session.

[0434] In step 3709, AMF sends an Nsmf_PDUSession_UpdateSMContext request {SmConextUpdateData} to vSMF2.

[0435] In step 3710, vSMF2 sends an Nsmf_PDUSession_Update request {vsmfId=vSMF2Id, vsmfPduSessionUri=vSMF2} to hSMF1.

[0436] In step 3711, hSMF1 sends an Nsmf_PDUSession_Update response to vSMF2.

[0437] In step 3712, vSMF2 sends the Nsmf_PDUSession_UpdateSMContext response {SmConextUpdatedData} to AMF.

[0438] Some of the messages shown in Figure 37 may be the same as the corresponding messages described in 3GPP® TS 23.502 V17.2.1. Some of the messages shown in Figure 37 may be enhanced according to embodiments of the present disclosure.

[0439] Figure 38 shows a flowchart of an exemplary solution for a V-SMF failure according to another embodiment of the present disclosure. Some parts described in the above embodiments are omitted for brevity.

[0440] Scenario 2 - VPLMN deploys an SMF set, but V-SMF does not support SMF sets, while H-SMF does.

[0441] AMF includes the vSMF recovery indicator in the CreateSMContext request directed to the selected vSMF. V-SMF forwards the received vSMF recovery indicator, which is included in the PDUSessionCreateRequest, to H-SMF, but V-SMF does not include the vSMF roaming resilience indicator. Also, vSMF does not support SMF sets.

[0442] If the selected V-SMF fails, the H-SMF maintains the associated PDU sessions and waits for the vSMF to recover. The AMF triggers PDU session reactivation to recover the affected PDU sessions, and the re-selected V-SMF sends a PDUSessionCreateRequest to the original H-SMF. The H-SMF accepts the new PDU session request by performing a Create on Create process.

[0443] In step 3801, AMF sends an Nsmf_PDUSession_CreateSMContext request to vSMF1 and receives a response from vSMF1.

[0444] According to one embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF recovery indication (i.e., vSMF supports PDU session recovery in the case of vSMF failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., hSMF supports roaming resilience).

[0445] In step 3802, vSMF1 sends an Nsmf_PDUSession_Create request to hSMF1.

[0446] In one embodiment, the Nsmf_PDUSession_Create request includes a vSMF recovery indication. According to another embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indication and / or an hSMF roaming resilience indication received from the AMF.

[0447] In step 3803, hSMF1 sends an Nsmf_PDUSession_Create response to vSMF1. According to one embodiment, the Nsmf_PDUSession_Create response includes a vSMF recovery indication (i.e., hSMF supports PDU session recovery in the event of a vSMF failure).

[0448] In step 3804, vNRF sends an Nnrf_NFManagement_NFStatusNotify request ("vSMF1 SUSPENDED") to hSMF1 and receives a response from hSMF1.

[0449] In step 3805, hSMF1 maintains the PDU session associated with the failed vSMF.

[0450] In step 3806, vNRF sends an Nnrf_NFManagement_NFStatusNotify request ("vSMF1 SUSPENDED") to AMF and receives a response from AMF.

[0451] In step 3807, the AMF triggers the reactivation of the PDU session.

[0452] In step 3808, AMF sends an Nsmf_PDUSession_CreateSMContext request to vSMF2 and receives a response from vSMF2.

[0453] According to one embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF recovery indication (i.e., vSMF2 supports PDU session recovery in the case of a vSMF2 failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., hSMF supports roaming resilience).

[0454] In step 3809, vSMF2 sends an Nsmf_PDUSession_Create request {vSMF recovery indication} to hSMF1.

[0455] In one embodiment, the Nsmf_PDUSession_Create request includes a vSMF recovery indication. According to another embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indication and / or an hSMF roaming resilience indication received from the AMF.

[0456] In step 3810, hSMF1 executes the create on create process.

[0457] In step 3811, hSMF1 sends an Nsmf_PDUSession_Create response to vSMF2.

[0458] According to one embodiment, the Nsmf_PDUSession_Create response includes a vSMF recovery indication (i.e., hSMF supports PDU session recovery in the event of a vSMF failure).

[0459] Some of the messages shown in Figure 38 may be the same as the corresponding messages described in 3GPP® TS 23.502 V17.2.1. Some of the messages shown in Figure 38 may be enhanced according to embodiments of the present disclosure.

[0460] Figure 39 shows a flowchart of an exemplary solution for a V-SMF failure according to another embodiment of the present disclosure. Some parts described in the above embodiments are omitted for brevity.

[0461] Scenario 3 - VPLMN deploys an SMF set, but V-SMF does not support SMF sets, and H-SMF does not support SMF sets.

[0462] As shown below, the same recovery solution as in Scenario 2 applies. That is, after the selected V-SMF fails, the H-SMF maintains the associated PDU sessions and waits for their recovery. The AMF triggers PDU session reactivation to recover the affected PDU sessions, and the re-selected V-SMF sends a PDU session creation request to the original H-SMF. The H-SMF performs a Create on Create process to accept the new PDU session request.

[0463] In step 3901, AMF sends an Nsmf_PDUSession_CreateSMContext request to vSMF1 and receives a response from vSMF1.

[0464] According to one embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF recovery indication (i.e., vSMF supports PDU session recovery in the case of vSMF failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., hSMF does not support roaming resilience).

[0465] In step 3902, vSMF1 sends an Nsmf_PDUSession_Create request to hSMF1.

[0466] In one embodiment, the Nsmf_PDUSession_Create request includes a vSMF recovery indication. According to another embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indication and / or an hSMF roaming resilience indication received from the AMF.

[0467] In step 3903, hSMF1 sends an Nsmf_PDUSession_Create response to vSMF1. According to one embodiment, the Nsmf_PDUSession_Create response includes a vSMF recovery indication (i.e., hSMF supports PDU session recovery in the event of a vSMF failure).

[0468] In step 3904, the vNRF (Visiting NRF) sends an Nnrf_NFManagement_NFStatusNotify request ("vSMF1 SUSPENDED") to the hSMF1 and receives a response from the hSMF1.

[0469] In step 3905, hSMF1 maintains the PDU session associated with the failed vSMF1.

[0470] In step 3906, vNRF sends an Nnrf_NFManagement_NFStatusNotify request ("vSMF1 SUSPENDED") to AMF.

[0471] In step 3907, the AMF triggers the reactivation of the PDU session.

[0472] Step 3908. AMF sends an Nsmf_PDUSession_CreateSMContext request to vSMF2 and receives a response from vSMF2.

[0473] According to one embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF recovery indication (i.e., vSMF supports PDU session recovery in the case of vSMF failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., hSMF does not support roaming resilience).

[0474] In step 3909, vSMF2 sends an Nsmf_PDUSession_Create request to hSMF1.

[0475] In one embodiment, the Nsmf_PDUSession_Create request includes a vSMF recovery indication. According to another embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indication and / or an hSMF roaming resilience indication received from the AMF.

[0476] In step 3910, hSMF1 executes the create on create process.

[0477] In step 3911, hSMF1 sends an Nsmf_PDUSession_Create response to vSMF2. According to one embodiment, the Nsmf_PDUSession_Create response includes a vSMF recovery indication (i.e., hSMF2 supports PDU session recovery in the case of a vSMF failure).

[0478] Some of the messages shown in Figure 39 may be the same as the corresponding messages described in 3GPP® TS 23.502 V17.2.1. Some of the messages shown in Figure 39 may be enhanced according to embodiments of the present disclosure.

[0479] Figure 40 shows a flowchart of an exemplary solution for H-SMF failure according to an embodiment of the present disclosure. Some parts described in the above embodiment are omitted for brevity.

[0480] Scenario 4 - HPLMN deploys an SMF set, H-SMF supports the SMF set, and V-SMF does not support the SMF set.

[0481] If the selected V-SMF does not support vSMF restore, AMF will not include a vSMF recovery indication to the V-SMF. The V-SMF will not include a vSMF roaming resilience indication or a vSMF recovery indication in the PDUSessionCreateRequest to the selected H-SMF. The H-SMF will not return a roaming resilience indication in response to the V-SMF because it detects that the V-SMF does not support roaming resilience. The H-SMF will also suppress the roaming resilience indication in service requests directed to surrounding 5GC NFs within HPLMN.

[0482] When the original H-SMF fails, the surrounding 5GC NFs within HPLMN clean up the context associated with the failed H-SMF because the H-SMF does not include the hSMF roaming resilience indication in service requests (or through NRF discovery). The associated V-SMF initiates the release of the SM context to the AMF, which triggers the reactivation of the PDU sessions for the affected PDU sessions.

[0483] The vSMF recovery indication is not used in H-SMF failure situations.

[0484] If V-SMF does not support hSMF roaming resilience in step 4001, H-SMF suppresses roaming resilience indication in requests to other 5GC NFs within HPLMN.

[0485] In step 4002, AMF sends an Nsmf_PDUSession_CreateSMContext request to vSMF1 and receives an Nsmf_PDUSession_CreateSMContext response from vSMF1.

[0486] According to one embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., hSMF supports roaming resilience).

[0487] In step 4003, vSMF1 sends an Nsmf_PDUSession_Create request to hSMF1.

[0488] According to another embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indication and / or an hSMF roaming resilience indication received from AMF.

[0489] In step 4004, hSMF1 sends an Npcf_SMPolicyControl_Create request to PCF1 and receives an Npcf_SMPolicyControl_Create response from PCF1.

[0490] In step 4005, hSMF1 sends an Nsmf_PDUSession_Create response to vSMF1.

[0491] In step 4006, hNRF sends an Nnrf_NFManagement_NFStatusNotify request ("hSMF1 SUSPENDED") to vSMF1 and receives an Nnrf_NFManagement_NFStatusNotify response from vSMF1.

[0492] In step 4007, the PCF cleans up the context associated with the failed hSMF based on the capability indication of the initial service request.

[0493] In step 4008, vSMF1 sends Nsmf_PDUSession_SMContextStatusNotify{resourceStatus=RELEASED, cause=”REL_DUE_TO_REACTIVATION”} to AMF and receives a response from AMF.

[0494] In step 4009, AMF sends Nsmf_PDUSession_CreateSMContext to vSMF1 and receives a response from vSMF1.

[0495] According to one embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., hSMF supports roaming resilience).

[0496] In step 4010, vSMF1 sends an Nsmf_PDUSession_Create request to hSMF2.

[0497] According to another embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indication and / or an hSMF roaming resilience indication received from AMF.

[0498] In step 4011, hSMF2 sends an Npcf_SMPolicyControl_Create request to PCF1 and receives a response from PCF1.

[0499] In step 4012, hSMF2 sends an Nsmf_PDUSession_Create response to vSMF1.

[0500] Some of the messages shown in Figure 41 may be the same as the corresponding messages described in 3GPP® TS 23.502 V17.2.1. Some of the messages shown in Figure 42 may be enhanced according to embodiments of the present disclosure.

[0501] Figure 41 shows a flowchart of an exemplary solution for H-SMF failure according to another embodiment of the present disclosure. Some parts described in the above embodiments are omitted for brevity.

[0502] Scenario 5 - HPLMN deploys an SMF set, H-SMF does not support SMF sets, while V-SMF does.

[0503] AMF includes the vSMF recovery indicator in its CreateSMContext request to vSMF, and V-SMF includes the vSMF roaming resilience indicator and the vSMF recovery indicator in its PDUSessionCreateRequest to the selected H-SMF. Since H-SMF does not support SMF sets, H-SMF does not include the roaming resilience indicator in its response to V-SMF.

[0504] When the original H-SMF fails, the surrounding 5GC NFs within HPLMN clean up the context associated with the failed H-SMF because the H-SMF does not include the hSMF roaming resilience indication in service requests (or through NRF discovery). The associated V-SMF initiates an SM context release to the AMF, which triggers PDU session reactivation for the affected PDU sessions.

[0505] The vSMF recovery indication is not useful in the case of an hSMF failure.

[0506] In step 4101, AMF sends an Nsmf_PDUSession_CreateSMContext request to vSMF1 and receives a response from vSMF1.

[0507] According to one embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF recovery indication (i.e., vSMF supports PDU session recovery in the case of vSMF failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., vSMF supports roaming resilience) and / or an hSMF roaming resilience indication (i.e., hSMF does not support roaming resilience).

[0508] In step 4102, vSMF1 sends an Nsmf_PDUSession_Create request to hSMF1.

[0509] According to one embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indicator and a vSMF recovery indicator. According to another embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indicator and / or an hSMF roaming resilience indicator received from the AMF.

[0510] In step 4103, hSMF1 sends an Npcf_SMPolicyControl_Create request to PCF1 and receives an Npcf_SMPolicyControl_Create response from PCF1.

[0511] In step 4104, hSMF1 sends an Nsmf_PDUSession_Create response to vSMF1. According to one embodiment, the Nsmf_PDUSession_Create response includes a vSMF recovery indication (i.e., hSMF supports PDU session recovery in the event of a vSMF failure).

[0512] In step 4105, hNRF sends an Nnrf_NFManagement_NFStatusNotify request ("hSMF1 SUSPENDED") to vSMF1 and receives an Nnrf_NFManagement_NFStatusNotify response from vSMF1.

[0513] In step 4106, the PCF cleans up the context associated with the failed hSMF based on capability indications within the hSMF profile.

[0514] In step 4107, vSMF1 sends an Nsmf_PDUSession_SMContextStatusNotify request {resourceStatus=RELEASED, cause=”REL_DUE_TO_REACTIVATION”} to AMF and receives an Nsmf_PDUSession_SMContextStatusNotify response from AMF.

[0515] In step 4108, AMF sends an Nsmf_PDUSession_CreateSMContext request to vSMF1 and receives a response from vSMF1.

[0516] According to one embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF recovery indication (i.e., vSMF supports PDU session recovery in the case of vSMF failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., vSMF supports roaming resilience) and / or an hSMF roaming resilience indication (i.e., hSMF2 does not support roaming resilience).

[0517] In step 4109, vSMF1 sends an Nsmf_PDUSession_Create request to hSMF2.

[0518] According to one embodiment, the Nsmf_PDUSession_Create request includes a vSMF recovery indicator and a vSMF roaming resilience indicator. According to another embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indicator and / or an hSMF roaming resilience indicator received from the AMF.

[0519] In step 4110, hSMF2 sends an Npcf_SMPolicyControl_Create request to PCF1 and receives an Npcf_SMPolicyControl_Create response from PCF1.

[0520] In step 4111, hSMF2 sends an Nsmf_PDUSession_Create response to vSMF1. According to one embodiment, the Nsmf_PDUSession_Create response includes a vSMF recovery indication (i.e., hSMF supports PDU session recovery in the event of a vSMF failure).

[0521] Some of the messages shown in Figure 41 may be the same as the corresponding messages described in 3GPP® TS 23.502 V17.2.1. Some of the messages shown in Figure 42 may be enhanced according to embodiments of the present disclosure.

[0522] Figure 42a shows a flowchart of an exemplary solution for H-SMF failure according to another embodiment of the present disclosure. Some parts described in the above embodiments are omitted for brevity.

[0523] Scenario 6 - HPLMN deploys an SMF set, but H-SMF does not support SMF sets, and V-SMF does not support SMF sets.

[0524] As shown below, the same recovery solution as in Scenario 5 applies. That is, after the original H-SMF fails, the surrounding 5GC NFs within HPLMN clean up the context associated with the failed H-SMF because the H-SMF does not include the hSMF roaming resilience indication in the service request (or through NRF discovery). The associated V-SMF initiates an SM context release to the AMF, which triggers PDU session reactivation for the affected PDU sessions.

[0525] In step 4201, AMF sends an Nsmf_PDUSession_CreateSMContext request to vSMF1 and receives a response from vSMF1.

[0526] According to one embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., hSMF does not support roaming resilience).

[0527] In step 4202, vSMF1 sends an Nsmf_PDUSession_Create request to hSMF1.

[0528] According to one embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indication and / or an hSMF roaming resilience indication received from AMF.

[0529] In step 4203, hSMF1 sends an Npcf_SMPolicyControl_Create request to PCF1 and receives an Npcf_SMPolicyControl_Create response from PCF1.

[0530] In step 4204, hSMF1 sends an Nsmf_PDUSession_Create response to vSMF1.

[0531] In step 4205, the hNRF (home NRF) sends an Nnrf_NFManagement_NFStatusNotify request ("hSMF1 SUSPENDED") to the vSMF1 and receives an Nnrf_NFManagement_NFStatusNotify response from the vSMF1.

[0532] In step 4206, the PCF cleans up the context associated with the failed hSMF based on capability indications within the hSMF profile.

[0533] In step 4207, vSMF1 sends an Nsmf_PDUSession_SMContextStatusNotify request {resourceStatus = RELEASED, cause = "REL_DUE_TO_REACTIVATION"} to AMF and receives an Nsmf_PDUSession_SMContextStatusNotify response from AMF.

[0534] In step 4208, AMF sends an Nsmf_PDUSession_CreateSMContext request to vSMF1 and receives a response from vSMF1.

[0535] According to one embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., hSMF does not support roaming resilience).

[0536] In step 4209, vSMF1 sends an Nsmf_PDUSession_Create request to hSMF2.

[0537] According to one embodiment, the Nsmf_PDUSession_Create request includes a vSMF roaming resilience indication and / or an hSMF roaming resilience indication received from AMF.

[0538] In step 4210, hSMF2 sends an Npcf_SMPolicyControl_Create request to PCF1 and receives an Npcf_SMPolicyControl_Create response from PCF1.

[0539] In step 4211, hSMF2 sends an Nsmf_PDUSession_Create response to vSMF1.

[0540] Some of the messages shown in Figure 42 may be the same as the corresponding messages described in 3GPP® TS 23.502 V17.2.1. Some of the messages shown in Figure 42 may be enhanced according to embodiments of the present disclosure.

[0541] The following content may be included in 3GPP® TS 23.527 V17.3.1. 6.X Recovery procedure for home-routed PDU sessions 6.X.1 Overview This section specifies the requirements for AMF, V-SMF, and H-SMF for recovery procedures when the SMF set function is not supported by either VPLMN or HPLMN. The procedure specified in Section 6.5 is used to recover a home-routed PDU session by re-selecting an alternative V-SMF or H-SMF if the V-SMF and H-SMF support the SMF set function for roaming interfaces. If supported, the V-SMF and H-SMF may indicate support for the SMF set function by setting the binding indication (i.e., the "3gpp-sbi-binding" HTTP header, see Section 5.2.3.2.6 of 3GPP® TS 29.500

[10] ) or the "NF Set for Roaming Interface (SETFRI)" feature bit in the SupportFeature attribute in service request and response messages, respectively, as further described below. When establishing an AMF-to-AMF mobility procedure for a home-routed PDU session, or when the (target) AMF supports the "Recovery by V-SMF Reselection in Case of V-SMF Failure" (RVSMFR) feature, it sets the corresponding feature bit in the supportFeatures attribute within the service request message directed to the V-SMF. If both AMF and V-SMF support the "V-SMF Re-selection Recovery in Case of V-SMF Failure" (RVSMFR) function, V-SMF sets the corresponding feature bit in the supportFeatures attribute of the service request message directed to H-SMF. If V-SMF supports the SETFRI function, it sets the corresponding feature bit in the supportFeatures attribute of the service request message directed to H-SMF and the service response message directed to AMF. H-SMF sets the corresponding feature bit in the supportedFeatures section of the service response message directed to V-SMF if it supports RVSMFR or SETFRI, respectively. 6.X.2 V-SMF Failure When H-SMF detects a V-SMF failure, it extracts all PDU sessions associated with the failed V-SMF and performs the following steps on those PDU sessions: ● If V-SMF supports the SETFRI function Furthermore, if the H-SMF supports the SETFRI function, the H-SMF can maintain the PDU session and, for example, re-select an alternative V-SMF when it requires any request messages to the V-SMF. ● If the H-SMF does not support the SETFRI function but does support the RVSMFR function, the H-SMF will maintain the PDU session and, if the V-SMF and AMF support the RVSMFR function, will wait for the PDU session to be recovered, triggered by the AMF re-selecting another V-SMF in the same set. Otherwise, the H-SMF will delete the affected PDU session. The AMF may request the UE to reactivate the PDU session based on its local configuration if the PDU session should be deleted. ● If V-SMF does not support the SETFRI function ● Regardless of whether H-SMF supports the SETFRI function, H-SMF can delete affected PDU sessions. When AMF detects a V-SMF failure, it extracts all PDU sessions associated with the failed V-SMF and performs the following steps on those PDU sessions: ● If H-SMF and AMF support the RVSMFR function, AMF will re-select an alternative V-SMF associated with the same NF (service) set as the failed V-SMF if V-SMF supports the SETFRI function. Note: If SMF supports the SETFRI function, it is assumed that it will also support the SMF set function for non-roaming reference points. ● Otherwise, AMF can request the UE to release the affected PDU session and reactivate the PDU session based on the local configuration. 6.X.2 H-SMF failure When V-SMF detects an H-SMF failure, it extracts all PDU sessions associated with the failed H-SMF and performs the following steps on those PDU sessions: ● If H-SMF does not support the SETFRI function, V-SMF will release the affected PDU sessions. ● If H-SMF supports the SETFRI function, V-SMF can select a different H-SMF if V-SMF also supports the SETFRI function; otherwise, V-SMF will release the PDU session. Note: Resources related to PDU sessions affected by HPLMN do not need to be maintained even if H-SMF supports SMF sets.

[0542] Figure 42b shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside the AMF, implemented in the same location as the AMF, implemented as the AMF, or communicatively coupled to the AMF. Thus, the device may provide means or modules for achieving various parts of Method 4214, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0543] In block 4215, the AMF may obtain third information about whether the resource is exclusively bound to a particular service instance in the first session management function (SMF).

[0544] In block 4216, the AMF may obtain a fourth piece of information regarding whether the second SMF supports the re-selection of an alternative first SMF instance within the SMF set of the first SMF.

[0545] In block 4217, the AMF may detect that the first SMF has failed.

[0546] In block 4218, the AMF may re-select an alternative service instance within the SMF set of the first SMF based on the third and fourth pieces of information.

[0547] For example, when AMF detects a V-SMF failure, it extracts all PDU sessions associated with the failed V-SMF and performs the following steps on those PDU sessions:

[0548] ● If H-SMF supports the "Peer NF Set-Based Reselection" (PSETR) feature (e.g., Information 4) and V-SMF supports the "Deployed Local SMF Set" (DLSET) feature (e.g., Information 3), AMF should maintain the PDU session and reselect an alternative V-SMF service instance when it needs to send an arbitrary request message to V-SMF, for example.

[0549] ● If the V-SMF supports the DLSET function while the H-SMF does not support the PSETR function, the AMF can re-select an alternative V-SMF service instance to maintain the PDU session and request the selected alternative V-SMF to delete the PDU session destined for the UE and UPF. The V-SMF can then request the UE to reactivate the PDU session.

[0550] ● In other cases, AMF can release the affected PDU session locally and / or notify the UE about the release of the PDU session.

[0551] According to one embodiment, the third piece of information may be of Boolean type, and / or the fourth piece of information may be of Boolean type.

[0552] According to one embodiment, obtaining the third information may include sending a network function (NF) discovery request to a network repository function (NRF) and receiving an NF discovery response containing the third information from the NRF.

[0553] According to one embodiment, obtaining the third information may include receiving a service response message or service request message containing the third information from the first SMF.

[0554] According to one embodiment, obtaining the fourth information may include sending an NF discovery request to the NRF and receiving an NF discovery response from the NRF that includes the fourth information.

[0555] According to one embodiment, obtaining the fourth information may include receiving an update session management (SM) context response message containing the fourth information from the first SMF.

[0556] According to one embodiment, re-selecting an alternative service instance within the SMF set of the first SMF based on third and fourth information may include re-selecting an alternative V-SMF service instance within the SMF set of the first SMF if the third information indicates that the resource is not exclusively bound to a particular service instance in the first SMF, and the fourth information indicates that the second SMF supports re-selecting an alternative first SMF instance within the SMF set of the first SMF.

[0557] According to one embodiment, reselecting an alternative service instance in the SMF set of the first SMF based on third and fourth information may further include reselecting an alternative first SMF service instance in the SMF set of the first SMF if the third information indicates that a resource is not exclusively bound to a particular service instance in the first SMF, and the fourth information indicates that the second SMF does not support reselecting an alternative first SMF service instance in the SMF set of the first SMF, and sending a request to the alternative first SMF to delete at least one affected protocol data unit (PDU) session destined for a user device (UE).

[0558] According to one embodiment, reselecting an alternative service instance within the SMF set of the first SMF based on third and fourth information may include releasing at least one affected PDU session without reselecting an alternative first SMF service instance if the third information indicates that a resource is exclusively bound to a particular service instance in the first SMF.

[0559] In one embodiment, the first SMF may be a visited SMF and the second SMF may be a home SMF, or the first SMF may be an intermediate SMF and the second SMF may be an anchor SMF.

[0560] Figure 42c shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed in an AMF, or as an AMF, or by a device communicatively coupled to an AMF. Thus, the device may provide means or modules for achieving various parts of Method 4220, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0561] In block 4222, the AMF may obtain a fifth piece of information regarding whether the resource is exclusively bound to a particular service instance in the second SMF.

[0562] In block 4224, the AMF may transmit a fifth piece of information to the first SMF.

[0563] Figure 42d shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside the first SMF, implemented in the same location as the first SMF, implemented as the first SMF, or communicatively coupled to the first SMF. Thus, the device may provide means or modules for achieving various parts of method 4230, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0564] In block 4232, the first SMF may obtain a fifth piece of information regarding whether the resource is exclusively bound to a particular service instance in the second SMF.

[0565] In block 4234, the first SMF may obtain a sixth piece of information regarding whether the first SMF supports the re-selection of an alternative second SMF instance within the second SMF set of the second SMF.

[0566] For example, when V-SMF detects a failure in H-SMF, it extracts all PDU sessions associated with the failed H-SMF and performs the following steps on those PDU sessions:

[0567] ● If V-SMF does not support the PSETR function (e.g., Information 6), V-SMF can release the affected PDU session to the AMF and UE, and can request the UE to reactivate the PDU session.

[0568] ● If V-SMF supports the PSETR function: ● If H-SMF supports the DLSET function (e.g., Information 5), V-SMF can maintain the PDU session and, for example, re-select an alternative H-SMF service instance if it needs to send an arbitrary request message to H-SMF. ● If H-SMF does not support the DLSET function, V-SMF can release the PDU session destined for AMF and UE, and V-SMF can request UE to reactivate the PDU session.

[0569] According to one embodiment, the fifth piece of information may be obtained from the Access and Mobility Function (AMF) or the second SMF.

[0570] Figure 42e shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside the first SMF, implemented in the same location as the first SMF, implemented as the first SMF, or communicatively coupled to the first SMF. Thus, the device may provide means or modules for achieving various parts of method 4240, as well as means or modules for achieving other processes in conjunction with other components. Some parts described in the above embodiments will be omitted for brevity.

[0571] In block 4242, the first SMF may send third information to the AMF regarding whether a resource is exclusively bound to a particular service instance in the first SMF.

[0572] In block 4244, the first SMF may send a fourth piece of information to the AMF regarding whether the second SMF supports the re-selection of an alternative first SMF instance within the first SMF's SMF set. The third and fourth pieces of information may be used by the AMF to re-select an alternative service instance within the first SMF's SMF set if the first SMF fails.

[0573] Figure 42f shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside the first SMF, implemented in the same location as the first SMF, implemented as the first SMF, or communicatively coupled to the first SMF. Thus, the device may provide means or modules for achieving various parts of method 4250, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0574] In block 4252, the first SMF may obtain the fourth piece of information.

[0575] According to one embodiment, the first SMF can obtain the fourth information by receiving the fourth information from the second SMF.

[0576] According to one embodiment, the third information may be included in a service request or response message.

[0577] According to one embodiment, the fourth piece of information may be included in the update SM context response message.

[0578] Figure 42g shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed by a device implemented inside the first SMF, implemented in the same location as the first SMF, implemented as the first SMF, or communicatively coupled to the first SMF. Thus, the device may provide means or modules for achieving various parts of method 4260, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0579] In block 4262, the first SMF may transmit third information to the second SMF.

[0580] According to one embodiment, the first SMF may be a visited SMF and the second SMF may be a home SMF, or the first SMF may be an intermediate SMF and the second SMF may be an anchor SMF.

[0581] Figure 42h shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented by a device that is implemented inside a second SMF, implemented in the same location as a second SMF, implemented as a second SMF, or communicatively connected to a first SMF. Thus, the device may provide means or modules for achieving various parts of method 4270, as well as means or modules for achieving other processes in combination with other components. Some parts described in the above embodiments will be omitted for brevity.

[0582] In block 4272, the second SMF may receive third information from the first SMF regarding whether a resource is exclusively bound to a particular service instance in the first SMF.

[0583] In block 4274, the second SMF may obtain a fourth piece of information regarding whether the second SMF supports the re-selection of an alternative first SMF instance within the first SMF set of the first SMF.

[0584] For example, when H-SMF detects a failure in V-SMF, it extracts all PDU sessions associated with the failed V-SMF and performs the following steps on those PDU sessions:

[0585] ● If H-SMF supports the PSETR function (for example, information 4): ● If V-SMF supports DLSET functionality (e.g., third information), H-SMF should maintain the PDU session and re-select an alternative V-SMF service instance if it needs to send any request messages to V-SMF, for example. ● If V-SMF does not support the DLSET function, H-SMF will locally delete the affected PDU session.

[0586] ● If H-SMF does not support the PSETR function: ● H-SMF deletes the affected PDU sessions.

[0587] In block 4276, the second SMF may optionally send a fifth piece of information to the first SMF regarding whether a resource is exclusively bound to a particular service instance in the second SMF.

[0588] In one embodiment, the first SMF may be a visited SMF and the second SMF may be a home SMF, or the first SMF may be an intermediate SMF and the second SMF may be an anchor SMF.

[0589] Figure 43 is a block diagram showing an apparatus suitable for carrying out some embodiments of the present disclosure. For example, one of the AMF, first SMF, second SMF, third NF, or NRF described above may be implemented as or through apparatus 4300.

[0590] The device 4300 comprises at least one processor 4321, such as a digital processor (DP), and at least one memory (MEM) 4322 coupled to the processor 4321. The device 4300 may further include a transmitter TX and a receiver RX 4323 coupled to the processor 4321. The MEM 4322 stores a program (PROG) 4324. The PROG 4324 may contain instructions that, when executed on the associated processor 4321, enable the device 4300 to operate according to embodiments of the present disclosure. The combination of at least one processor 4321 and at least one MEM 4322 may form processing means 4325 adapted to implement various embodiments of the present disclosure.

[0591] Various embodiments of this disclosure may be implemented by a computer program executable by one or more of the processor 4321, software, firmware, hardware, or a combination thereof.

[0592] MEM4322 may be of any type suitable for the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples.

[0593] The processor 4321 may be of any type suitable for the local technical environment and may include, in non-limiting examples, one or more of general-purpose computers, dedicated computers, microprocessors, digital signal processors (DSPs), and processors based on multi-core processor architectures.

[0594] According to one embodiment in which the device is implemented as an AMF or in the same location as the AMF, the memory 4322 contains instructions that can be executed by the processor 4321, thereby the AMF operates in any of the AMF-related methods described above.

[0595] According to embodiments in which the device is implemented as a first SMF or in the same location as the first SMF, the memory 4322 contains instructions that can be executed by the processor 4321, thereby the first SMF operates in any of the manner associated with the first SMF as described above.

[0596] According to embodiments in which the device is implemented as a second SMF or in the same location as the second SMF, the memory 4322 contains instructions that can be executed by the processor 4321, thereby the second SMF operates in any of the manner associated with the second SMF as described above.

[0597] According to embodiments in which the device is implemented as a third NF, or in the same location as the third NF, the memory 4322 contains instructions that can be executed by the processor 4321, thereby the third NF operates in any of the ways relating to the third NF as described above.

[0598] According to embodiments in which the device is implemented as an NRF or in the same location as the NRF, the memory 4322 contains instructions that can be executed by the processor 4321, thereby the NRF operates in any of the manner relating to the NRF as described above.

[0599] Figure 44 is a block diagram showing an AMF according to one embodiment of the present disclosure. As shown in the figure, the AMF 4400 includes a first acquisition module 4401 configured to acquire third information regarding whether a resource is exclusively bound to a particular service instance in a first session management function (SMF). According to one embodiment, the AMF 4400 may further include a second acquisition module 4402 configured to acquire fourth information regarding whether a second SMF supports the reselection of an alternative first SMF instance within the SMF set of the first SMF. The AMF 4400 may further include a detection module 4403 configured to detect that the first SMF has failed. The AMF 4400 may further include a reselection module 4404 configured to reselect an alternative service instance within the SMF set of the first SMF based on the third and fourth information.

[0600] According to one embodiment, the AMF4400 may further comprise a third acquisition module 4405 configured to acquire fifth information regarding whether a resource is exclusively bound to a particular service instance in a second SMF.

[0601] According to one embodiment, the AMF4400 may further include a transmitting module 4406 configured to transmit fifth information to the first SMF.

[0602] Figure 45 is a block diagram of a first SMF according to one embodiment of the present disclosure. As shown, the first SMF 4500 may include a first transmit module 4501 configured to transmit a third information to the AMF regarding whether a resource is exclusively bound to a particular service instance in the first SMF. The first SMF 4500 may further include a second transmit module 4502 configured to transmit a fourth information to the AMF regarding whether a second SMF supports the reselection of an alternative first SMF instance within the SMF set of the first SMF.

[0603] According to one embodiment, the third and fourth pieces of information may be used by the AMF to re-select an alternative service instance within the SMF set of the first SMF when the first SMF fails.

[0604] According to one embodiment, the first SMF 4500 may further include a first retrieval module 4503 configured to retrieve a fifth piece of information about whether a resource is exclusively bound to a particular service instance in the second SMF. The first SMF 4500 may further include a second retrieval module 4504 configured to retrieve a sixth piece of information about whether the first SMF supports the re-selection of an alternative second SMF instance within the SMF set of the second SMF.

[0605] According to one embodiment, the first SMF4500 may further include a third acquisition module 4505 configured to acquire a fourth piece of information.

[0606] According to one embodiment, the first SMF 4500 may further include a third transmitting module 4506 configured to transmit third information to the second SMF.

[0607] Figure 46 is a block diagram of a second SMF according to one embodiment of the present disclosure. As shown, the second SMF 4600 includes a receive module 4601 configured to receive third information from the first SMF regarding whether a resource is exclusively bound to a particular service instance within the first SMF. The second SMF 4600 may further include a retrieve module 4602 configured to obtain fourth information regarding whether the second SMF supports re-selection of an alternative first SMF instance within the SMF set of the first SMF.

[0608] According to one embodiment, the second SMF 4600 may further include a transmission module 4603 configured to send a fifth piece of information to the first SMF regarding whether a resource is exclusively bound to a particular service instance within the second SMF.

[0609] The embodiments of this specification can offer many advantages, and a non-exhaustive list of examples follows below. According to some embodiments of this specification, recovery procedures are proposed for recovering PDU sessions affected by SMF failures. According to some embodiments of this specification, the time required to recover PDU sessions affected by SMF failures can be reduced. According to some embodiments of this specification, the problem of ghost sessions can be solved. According to some embodiments of this specification, the availability of services can be improved. The embodiments of this specification are not limited to the features and advantages described above. Those skilled in the art will recognize additional features and advantages by reading the detailed description below.

[0610] The terms unit or module may have their conventional meanings in the field of electronic equipment, electrical devices and / or electronic devices, and may include, for example, electrical and / or electronic circuits, devices, modules, processors, memories, logic solid-state and / or discrete devices, computer programs or instructions for performing their respective tasks, procedures, calculations, outputs and / or display functions, as described herein.

[0611] In a functional unit, the AMF, the first SMF, or the second SMF may not require a fixed processor or memory, and any computing and storage resources within the communication system may comprise the AMF, the first SMF, or the second SMF. The introduction of virtualization and network computing technologies can improve the efficiency of network resource utilization and network flexibility.

[0612] According to one aspect of the present disclosure, a computer program product is provided which, when tangibly stored in a computer-readable storage medium and executed on at least one processor, includes instructions that cause at least one processor to perform one of the methods described above.

[0613] According to one aspect of the present disclosure, a computer-readable storage medium is provided that, when executed by at least one processor, stores instructions causing at least one processor to perform one of the methods described above.

[0614] Furthermore, this disclosure may also provide a carrier including the aforementioned computer program, the carrier being one of the following: an electrical signal, an optical signal, a radio signal, or a computer-readable storage medium. The computer-readable storage medium may be, for example, an optical compact disc, or an electronic memory device such as RAM (random access memory), ROM (read-only memory), flash memory, magnetic tape, CD-ROM, DVD, or Blu-ray disc.

[0615] The techniques described herein may be implemented by various means such that an apparatus implementing one or more functions of the corresponding apparatus described in conjunction with the embodiments includes not only means of the prior art but also means for implementing one or more functions of the corresponding apparatus described in conjunction with the embodiments, and may include means that are configured to perform one or more functions, or separate means for each separate function. For example, these techniques may be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or a combination thereof. Firmware or software may be implemented via modules (e.g., procedures, functions, etc.) that perform the functions described herein.

[0616] Exemplary embodiments of this specification are described above with reference to block diagrams and flowcharts of methods and apparatus. It will be understood that each block in the block diagrams and flowcharts, as well as each combination of blocks in the block diagrams and flowcharts, can be implemented by various means, including computer program instructions. These computer program instructions can be loaded onto a general-purpose computer, a dedicated computer, or other programmable data processing device to generate a machine such that instructions executed on the computer or other programmable data processing device create means for implementing the functions specified in one or more flowchart blocks.

[0617] Furthermore, although the operations are described in a specific order, this should not be understood as requiring that such operations be performed in a specific or sequential order, or that all described operations be performed, in order to achieve the desired result. In certain circumstances, multitasking and parallel processing may be advantageous. Similarly, some specific implementation details are included in the above discussion, but these should be interpreted not as limitations on the scope of the subject matter described herein, but rather as descriptions of features that may be specific to a particular embodiment. Certain features described in the context of a separate embodiment may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may be implemented separately or in any suitable subcombination in multiple embodiments.

[0618] This specification includes many specific implementation details, but these should not be construed as limitations on the scope of any implementation or what can be claimed, but rather as descriptions of features that may be specific to a particular embodiment of a particular implementation. Certain features described herein in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented separately in multiple embodiments or in any suitable subcombination. Furthermore, features may be described above as acting in a particular combination, and even if initially claimed in that manner, one or more features from the claimed combination may, in some cases, be separated from that combination, and the claimed combination may be directed towards a subcombination or a variation of a subcombination.

[0619] As technology advances, it will be apparent to those skilled in the art that the concepts of this disclosure can be implemented in a variety of ways. The embodiments described above are provided for illustrative purposes rather than to limit this disclosure, and it should be understood that modifications and variations may be used without departing from the spirit and scope of this disclosure, as will be readily apparent to those skilled in the art. Such modifications and changes are considered to fall within the scope of this disclosure and the attached claims. The scope of protection of this disclosure is defined by the attached claims.

Claims

1. A method (4214) performed by an access and mobility function (AMF), In the first session management function (SMF), obtain a third piece of information regarding whether a resource is exclusively bound to a specific service instance (4215), The fourth information obtained (4216) is whether the second SMF supports the re-selection of an alternative first SMF instance within the SMF set of the first SMF, Detecting that the first SMF has failed (4217), Based on the third and fourth pieces of information, re-select an alternative service instance of the first SMF within the SMF set (4218), A method having.

2. A method according to claim 1, wherein the third information is of Boolean type, and / or the fourth information is of Boolean type.

3. A method according to claim 1 or 2, wherein obtaining the third information is: The Network Function (NF) sends a discovery request to the Network Repository Function (NRF), Receiving an NF discovery response containing the third information from the NRF, Methods that include...

4. A method according to any one of claims 1 to 3, wherein obtaining the third information is: Receiving a service response message or service request message containing the third information from the first SMF, Methods that include...

5. The method according to any one of claims 1 to 4, wherein obtaining the fourth information is: Sending an NF discovery request to the NRF, Receiving an NF discovery response containing fourth information from the aforementioned NRF, Methods that include...

6. A method according to any one of claims 1 to 5, wherein obtaining the fourth information is: Receiving an update session management (SM) context response message containing the fourth information from the first SMF, Methods that include...

7. A method according to any one of claims 1 to 6, wherein the re-selection of an alternative service instance within the SMF set of the first SMF based on the third and fourth information is: Reselecting the alternative V-SMF service instance in the SMF set of the first SMF if the third information indicates that the resource is not exclusively bound to the particular service instance in the first SMF, and the fourth information indicates that the second SMF supports reselecting the alternative first SMF instance in the SMF set of the first SMF, Methods that include...

8. A method according to any one of claims 1 to 7, wherein the reselection of an alternative service instance within the set of SMFs of the first SMF based on the third and fourth information is: If the third piece of information indicates that the resource is not exclusively bound to the particular service instance in the first SMF, and the fourth piece of information indicates that the second SMF does not support the re-selection of the alternative first SMF instance within the SMF set of the first SMF, Re-selecting the alternative first SMF service instance within the SMF set of the first SMF, Sending a request to the alternative first SMF to delete at least one affected protocol data unit (PDU) session destined for a user device (UE), Methods that include...

9. A method according to any one of claims 1 to 8, wherein the re-selection of an alternative service instance within the set of SMFs of the first SMF is based on the third and fourth information, If the third piece of information indicates that the resource is exclusively bound to the specific service instance in the first SMF, then release at least one affected PDU session without re-selecting the alternative first SMF service instance. Methods that include...

10. A method according to any one of claims 1 to 9, wherein the first SMF is a visited SMF and the second SMF is a home SMF, or the first SMF is an intermediate SMF and the second SMF is an anchor SMF.

11. A method according to any one of claims 1 to 10, further, Obtaining a fifth piece of information (4222) regarding whether the resource is exclusively bound to a specific service instance within the second SMF, Transmitting the fifth information to the first SMF (4224), A method having.

12. A method (4240) performed by a first session management function (SMF), Sending a third piece of information to the AMF (4242) regarding whether the resource is exclusively bound to a specific service instance within the first SMF, The AMF (4244) transmits a fourth piece of information to the AMF regarding whether the second SMF supports the reselection of an alternative first SMF instance within the SMF set of the first SMF, The third and fourth pieces of information are used by the AMF to reselect an alternative service instance within the SMF set of the first SMF if the first SMF fails.

13. The method according to claim 12, further, To obtain the fourth information (4252), A method having.

14. The method according to claim 13, wherein obtaining the fourth information is: Receiving the fourth information from the second SMF, Methods that include...

15. A method according to any one of claims 12 to 14, further, Transmitting the third information to the second SMF (4262), A method having.

16. A method according to any one of claims 12 to 15, wherein the third information is included in a service request or response message.

17. A method according to any one of claims 12 to 16, wherein the fourth information is included in the updated SM context response message.

18. A method according to any one of claims 12 to 17, wherein the first SMF is a visited SMF and the second SMF is a home SMF, or the first SMF is an intermediate SMF and the second SMF is an anchor SMF.

19. A method according to any one of claims 12 to 18, wherein the method further comprises: A fifth piece of information (4232) is obtained regarding whether the resource is exclusively bound to a specific service instance in the second SMF, Obtaining a sixth piece of information (4234) about whether the first SMF supports the re-selection of an alternative second SMF instance within the SMF set of the second SMF, A method having.

20. A method according to claim 19, wherein the fifth information is obtained from an access and mobility function (AMF) or the second SMF.

21. A method (4270) performed by a second session management function (SMF), Receiving third information from the first SMF regarding whether the resource is exclusively bound to a specific service instance in the first SMF (4272), A fourth piece of information (4274) is obtained regarding whether the second SMF supports the re-selection of an alternative first SMF instance within the SMF set of the first SMF, A method having.

22. The method according to claim 21, further, Sending a fifth piece of information to the first SMF regarding whether the resource is exclusively bound to a specific service instance in the second SMF (4276), A method having.

23. A method according to claim 21 or 22, wherein the first SMF is a visited SMF and the second SMF is a home SMF, or the first SMF is an intermediate SMF and the second SMF is an anchor SMF.

24. Access and mobility functions (AMF) (4300), Processor (4321), The AMF (4300) comprises a memory (4322) coupled to the processor (4321), wherein the memory (4322) includes instructions executable by the processor (4321), and thereby the AMF (4300) A third piece of information is obtained regarding whether the resource is exclusively bound to a specific service instance within the First Session Management Function (SMF). A fourth piece of information is obtained regarding whether the second SMF supports the re-selection of an alternative first SMF instance within the SMF set of the first SMF. The first SMF is detected to have failed, Based on the third and fourth pieces of information, re-select an alternative service instance of the first SMF within the SMF set. AMF operates in this manner.

25. An AMF according to claim 24, wherein the AMF further operates to perform the method according to any one of claims 2 to 11.

26. The first session management function (SMF) (4300) is, Processor (4321), The first SMF (4300) has a memory (4322) coupled to the processor (4321), and the memory (4322) includes instructions that can be executed by the processor (4321), thereby the first SMF (4300) Third information regarding whether the resource is exclusively bound to a specific service instance within the first SMF is sent to the AMF, The second SMF transmits fourth information to the AMF regarding whether the second SMF supports the reselection of an alternative first SMF instance within the SMF set of the first SMF. It operates in this way, The third and fourth pieces of information are used by the AMF to re-select an alternative service instance of the first SMF in the set of SMFs if the first SMF fails.

27. A first SMF according to claim 26, wherein the first SMF further operates to perform the method according to any one of claims 13 to 20.

28. The second session management function (SMF) (4300) is, Processor (4321), The second SMF (4300) has a memory (4322) coupled to the processor (4321), and the memory (4322) includes instructions that can be executed by the processor (4321), thereby the second SMF (4300) From the first SMF, receive third information regarding whether the resource is exclusively bound to a specific service instance within the first SMF. A fourth piece of information is obtained regarding whether the second SMF supports the re-selection of an alternative first SMF instance within the SMF set of the first SMF. A second SMF that operates in this manner.

29. A second SMF according to claim 28, wherein the second SMF further operates to perform the method described in any one of claims 22 to 23.

30. A computer-readable storage medium that, when executed by at least one processor, stores instructions causing the at least one processor to perform the method according to any one of claims 1 to 23.

31. A computer program product that, when executed by at least one processor, includes instructions causing the at least one processor to perform the method according to any one of claims 1 to 23.

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