Method and apparatus for dealing with mismatched SMF sets - Patents.com

Abstract

An embodiment of the present disclosure provides a method and apparatus for addressing a mismatch of SMF sets. The method performed by an Access and Mobility Function (AMF) may include obtaining third information about whether a resource is exclusively bound to a particular service instance in a first Session Management Function (SMF). The method may further include obtaining fourth information about whether a second SMF supports reselection of an alternative first SMF instance in the SMF set of the first SMF. The method may further include detecting that the first SMF has failed. The method may further include reselecting an alternative service instance in the SMF set of the first SMF based on the third information and the fourth information.

Description

[Technical field]

[0001] Non-limiting, exemplary embodiments of the present disclosure relate generally to the field of communications technology, and more particularly, to a method and apparatus for addressing a mismatch of SMF (Session Management Function) sets. [Background technology]

[0002] This section introduces aspects that may facilitate a better understanding of the present disclosure. Accordingly, the statements in this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.

[0003] For example, in a NR (New Radio) communication network as defined by the 3rd Generation Partnership Project (3GPP), we introduce NF set-based session resilience, where equivalent control plane network functions (NFs) can be grouped into an NF set. For example, several SMF instances are grouped into an SMF set. Multiple NFs in an NF set are interchangeable since they share the same context data. An NF can be replaced by an alternative NF in the same NF set in case of scenarios such as failure, load balancing, and load rebalancing.

[0004] An SMF can play the role of SMF, V-SMF (Visited SMF) or H-SMF (Home SMF) for different PDU session contexts. The concept of an SMF set does not distinguish between different SMF roles. When an SMF registers with an SMF set ID in the NRF (Network Repository Function), it means that the SMF can support SMF set based resilience for all session contexts established in SMF, V-SMF or H-SMF role, if the SMF is used simultaneously for non-roaming (SMF role) or roaming-in (V-SMF role) or roaming-out (H-SMF role). Summary of the Invention

[0005] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features 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 the VPLMN (Visited PLMN (Public Land Mobile Network)) and the HPLMN (Home PLMN) are required to deploy SMF sets to support resilience functions for the V-SMF and H-SMF roles.

[0007] In a real network deployment, it is unlikely that all PLMNs deploy an SMF set. It is also possible that a PLMN may have an SMF set for non-roaming users, but the SMF set does not support resilience for roaming users, or the resilience of the SMF set is not included in the roaming agreement.

[0008] It is also not clear how to derive whether a peer SMF supports SMF sets and whether the peer SMF does not provide binding indication in request and response messages. NRF-based service discovery can help, but it introduces at least extra signaling delay time and cannot cover the case where an SMF set is established 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 will result in PDU sessions served by the failed SMF being deleted unnecessarily or left as hung resources.

[0009] The network behavior when a VPLMN or HPLMN has different SMF set recovery capabilities or configurations is not specified in the current 3GPP release, and a possible mismatch between VPLMN and HPLMN may occur during an SMF failure scenario, resulting in time-consuming reactivation of all related PDU sessions and impacting service availability.

[0010] For example, since the V-SMF supports SMF sets but the H-SMF does not support SMF sets, when detecting a V-SMF failure, the H-SMF will delete the PDU session locally while the V-SMF will maintain the PDU session. Mobile terminated services will be affected.

[0011] The V-SMF does not support SMF sets, whereas the H-SMF does. Upon detecting a failure of the H-SMF, the V-SMF releases the affected PDU sessions, which may leave PDU sessions hung up in the alternative H-SMF, which in turn hangs up sessions in its upstream nodes, e.g. the PCF.

[0012] In 3GPP, the support of SMF (NF) (service) sets is not very clearly defined, but in the applicant's opinion, it includes at least two aspects for supporting SMF (NF). 1) All resource contexts provided by an SMF may be shared by at least one or more SMFs in the same SMF (service) set or its backup SMFs, so that in case of an SMF failure, a peer entity can select an alternative one when it detects the failure of an SMF. 2) The SMF may reselect an alternative peer entity based on the binding indication provided by the peer entity or the NF profile of the peer entity registered with the NRF when the SMF detects that the peer entity has failed.

[0013] According to one embodiment, as long as an SMF supports Barrett 2, it can claim to support the SMF set functionality.

[0014] However, if an SMF only supports Bullet 2, it seems reasonable to consider it, since it may be permitted to claim to support 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, imagine the following scenario: if the H-SMF does not support resilience, i.e. its resources are bound only to a specific NF service instance, then support is indicated to SETFRI since in case of a V-SMF failure another V-SMF can be reselected.

[0016] Therefore, if this H-SMF fails, the peer SMF (V-SMF) cannot trigger restoration immediately upon detecting the failure of the H-SMF, but will only trigger restoration when there are signaling messages to be sent for a PDU session destined for the failed H-SMF, but when the peer V-SMF tries to find an alternative H-SMF, it will find that no alternative H-SMF exists.

[0017] In fact, when a PDU session in which an H-SMF is deleted, all PDU sessions served by this H-SMF are unable to receive mobile terminated services and suffer from a large amount of hung-up resources in the V-SMF and AMF.

[0018] To overcome or mitigate at least one of the above problems or other problems, new solutions are needed to address SMF set mismatch.

[0019] In a first aspect of the present disclosure, a method is provided that is performed by an Access and Mobility Function (AMF). The method may include obtaining third information about whether a resource is exclusively bound to a particular service instance in a first Session Management Function (SMF). The method may further include obtaining fourth information about whether a second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF. The method may further include detecting that the first SMF has failed. The method may further include reselecting an alternative service instance in an SMF set of the first SMF based on the third information and the fourth information.

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

[0022] According to one embodiment, obtaining the third information may include receiving a service response message or a service request message including 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 including the fourth information.

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

[0025] 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 reselecting an alternative V-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 particular service instance in the first SMF and the fourth information indicates that the second SMF supports reselection of an alternative first SMF instance within the SMF set of the first SMF.

[0026] According to one embodiment, reselecting an alternative service instance in the SMF set of the first SMF based on the third information and the fourth information may further include, if the third information indicates that resources are not exclusively bound to a particular service instance in the first SMF and the fourth information indicates that the second SMF does not support reselection of the alternative first SMF 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 toward a user equipment (UE).

[0027] According to one embodiment, reselecting an alternative service instance in 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 if the third information indicates that the resource is exclusively bound to a particular 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 about whether the resource is exclusively bound to a particular service instance in the second SMF. The method may further include sending the fifth information to the first SMF.

[0030] In a second aspect of the present disclosure, a method is provided that is performed by a first Session Management Function (SMF). The method includes sending to the AMF third information about whether a resource is exclusively bound to a particular service instance in the first SMF. The method may further include sending to the AMF fourth information about whether the second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF. The third information and the fourth information are used by the AMF to reselect an alternative service instance in the SMF set of the first SMF when the first SMF fails.

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

[0032] According to an embodiment, the method may further include obtaining fifth information about whether the resource is exclusively bound to a particular service instance in the second SMF. The method further includes obtaining sixth information about whether the first SMF supports reselection of an alternative second SMF instance in 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 information may be included in an update SM context response message.

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

[0038] 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.

[0039] In a third aspect of the present disclosure, a method is provided that is performed by a second Session Management Function (SMF). The 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. The method may further include obtaining fourth information about whether the second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF.

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

[0041] 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.

[0042] In a fourth aspect of the present disclosure, an access and mobility function (AMF) is provided. The AMF comprises a processor and a memory coupled to the processor. The memory includes instructions executable by the processor. The AMF is operable to obtain third information regarding 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 regarding whether a second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF. The AMF is further operable to detect that the first SMF has failed. The AMF is further operable to reselect an alternative service instance in an SMF set of the first SMF based on the third information and the fourth information.

[0043] In a fifth aspect of the present disclosure, a first session management function (SMF) is provided. The first SMF comprises a processor and a memory coupled to the processor. The memory includes instructions executable by the processor. The first SMF is operative to send to the AMF third information about whether a resource is exclusively bound to a particular service instance in the first SMF. The first SMF is further operative to send to the AMF fourth information about whether the second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF. The third information and the fourth information may be used by the AMF to reselect an alternative service instance in an SMF set of the first SMF when the first SMF fails.

[0044] In a sixth aspect of the present disclosure, a second session management function (SMF) is provided. The second SMF comprises a processor and a memory coupled to the processor. The memory includes instructions executable by the processor. The second SMF is operative to receive from the first SMF third information about whether a resource is exclusively bound to a particular service instance in the first SMF. The second SMF is further operative to obtain fourth information about whether the second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF.

[0045] In a seventh aspect of the present disclosure, an AMF is provided. The AMF includes a first acquisition module 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 an embodiment, the second SMF further includes a second acquisition module configured to acquire fourth information regarding whether the second SMF supports reselection of an alternative first SMF instance in an 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 in an SMF set of the first SMF based on the third information and the fourth information.

[0046] According to one embodiment, the AMF may further have a third acquisition module that may be configured to acquire fifth information regarding whether a resource is exclusively bound to a particular service instance in the second SMF.

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

[0048] In an eighth aspect of the present disclosure, a first SMF is provided. The first SMF may include a first sending module configured to send to the AMF third information regarding whether a resource is exclusively bound to a particular service instance in the first SMF. The first SMF may further include a second sending module configured to send to the AMF fourth information regarding whether the second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF.

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

[0050] According to an embodiment, the first SMF may further include a first obtaining module configured to obtain fifth 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 obtaining module configured to obtain sixth information about whether the first SMF supports reselection of an alternative second SMF instance in 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 the fourth information.

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

[0053] In a ninth aspect of the present disclosure, a second SMF is provided. The second SMF may include a receiving module configured to receive, from the first SMF, third information about whether a resource is exclusively bound to a particular service instance in the first SMF. The second SMF may further include an acquiring module configured to acquire fourth information about whether the second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF.

[0054] According to one embodiment, the second SMF may further comprise a sending module configured to send to the first SMF fifth information regarding whether a resource is exclusively bound to a particular service instance in the second SMF.

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

[0057] The embodiments herein may provide many advantages, a non-exhaustive list of examples of which follows below. According to some embodiments herein, a restore procedure is proposed to recover PDU sessions affected by SMF failures. According to some embodiments herein, the time to recover PDU sessions affected by SMF failures may be reduced. According to some embodiments herein, the ghost session problem may be resolved. According to some embodiments herein, the availability of services may be improved. The embodiments herein are not limited to the features and advantages described above. Those skilled in the art will recognize additional features and advantages upon reading the following detailed description. [Brief description of the drawings]

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

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

[0060] [Diagram 2] 4 illustrates a second failure scenario according to an embodiment of the present disclosure.

[0061] [Diagram 3] 4 illustrates a third failure scenario according to an embodiment of the present disclosure.

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

[0063] [Diagram 5]5 illustrates a fifth failure scenario according to an embodiment of the present disclosure.

[0064] [Figure 6] 1 illustrates a sixth failure scenario according to an embodiment of the present disclosure.

[0065] [Figure 7] 1 is a schematic diagram illustrating a roaming 5G system architecture according to an embodiment of the present disclosure.

[0066] [Figure 8] 3 shows a flowchart of a method according to an embodiment of the present disclosure.

[0067] [Figure 9] 1 shows a flowchart of obtaining first information about whether a first SMF supports a first capability according to an embodiment of the present disclosure.

[0068] [Figure 10] 1 shows a flowchart of obtaining second information about whether a second SMF supports a first capability according to an embodiment of the present disclosure.

[0069] [Figure 11] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0070] [Figure 12] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0071] [Figure 13] 1 shows a flowchart of obtaining third information about whether a first SMF supports a local NF set for the first SMF and a peer NF set for a second SMF according to an embodiment of the present disclosure.

[0072] [Figure 14]1 shows a flowchart of obtaining fourth information about whether a second SMF supports a local NF set for the second SMF and a peer NF set for the first SMF according to one embodiment of the present disclosure.

[0073] [Figure 15] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0074] [Figure 16] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0075] [Figure 17] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0076] [Figure 18] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0077] [Figure 19] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0078] [Figure 20a] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0079] [Figure 20b] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0080] [Figure 21a] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0081] [Figure 21b] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0082] [Figure 22] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0083] [Figure 23] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0084] [Figure 24] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0085] [Diagram 25] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0086] [Figure 26] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0087] [Figure 27a] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0088] [Figure 27b] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0089] [Figure 28] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0090] [Figure 29] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0091] [Diagram 30] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0092] [Diagram 31] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0093] [Diagram 32] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0094] [Diagram 33] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0095] [Diagram 34] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0096] [Diagram 35] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0097] [Diagram 36] 3 shows a flowchart of a method according to another embodiment of the present disclosure.

[0098] [Figure 37] 1 shows a flowchart of an example solution for a V-SMF failure according to an embodiment of the present disclosure.

[0099] [Figure 38] 1 shows a flowchart of an exemplary solution for a V-SMF failure according to another embodiment of the present disclosure.

[0100] [Figure 39] 1 shows a flowchart of an exemplary solution for a V-SMF failure according to another embodiment of the present disclosure.

[0101] [Diagram 40] 1 shows a flowchart of an example solution for an H-SMF failure according to an embodiment of the present disclosure.

[0102] [Diagram 41] 1 shows a flowchart of an exemplary solution for an H-SMF failure according to another embodiment of the present disclosure.

[0103] [Figure 42a] 1 shows a flowchart of an exemplary solution for an H-SMF failure according to another embodiment of the present disclosure.

[0104] [Figure 42b] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0105] [Fig. 42c] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0106] [Fig.42d] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0107] [Figure 42e] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0108] [Fig.42f] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0109] [Fig. 42g] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0110] [Fig. 42h] 4 shows a flowchart of a method according to another embodiment of the present disclosure.

[0111] [Diagram 43] 1 is a block diagram illustrating an apparatus suitable for implementing some embodiments of the present disclosure.

[0112] [Diagram 44] 1 is a block diagram illustrating an AMF according to one embodiment of the present disclosure.

[0113] [Diagram 45] FIG. 2 is a block diagram illustrating a first SMF according to one embodiment of the present disclosure.

[0114] [Diagram 46] FIG. 2 is a block diagram showing a second SMF according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0115] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled in the art to better understand and thus practice the present disclosure, and do not imply any limitations on the scope of the present disclosure. Throughout this specification, reference to features, advantages, or similar words does not imply that all of the features and advantages that may be realized by the present disclosure should be or should be in any single embodiment of the present disclosure. Rather, words referring to features and advantages are understood to mean that the particular features, advantages, or characteristics described in connection with the embodiments are included in at least one embodiment of the present disclosure. Furthermore, the described features, advantages, and characteristics of the present disclosure can be combined in any suitable manner in one or more embodiments. Those skilled in the art will recognize that the present disclosure may be practiced without one or more of the specific features or advantages of a particular embodiment. In other cases, additional features and advantages may be recognized in a particular embodiment that may not be present in all embodiments of the present disclosure.

[0116] As used herein, the term "network" refers to a network conforming to any suitable communications standard, such as New Radio (NR), Long Term Evolution (LTE), LTE Advanced (LTE-A), Wideband 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 a radio technology such as Universal Terrestrial Radio Access (UTRA), which includes WCDMA and other variants of CDMA. A TDMA network may implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network may 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, wireless sensor networks, etc. In the following description, the terms "network" and "system" may be used interchangeably. Furthermore, communication between two devices in the network may be performed according to any suitable communication protocol, including but not limited to communication protocols defined by standardization organizations such as 3GPP. For example, the communication protocol may include first generation (1G), 2G, 3G, 4G, 4.5G, 5G communication protocols, and / or any other protocols currently known or developed in the future.

[0117] The term "network device" or "network node" or "network function" refers to any suitable network function (NF) that can be implemented in 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 Publishing 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), NSSAAF (Network Slice Specific Authentication and Authorization Function).

[0118] The term "terminal device" refers to any terminal device capable of accessing and receiving services from a communication network. By way of example and not limitation, a terminal device refers to a mobile terminal, a user equipment (UE), or other suitable device. A UE may be, for example, a subscriber station (SS), a portable subscriber station, a mobile station (MS), or an access terminal (AT). A terminal device may include, but is not limited to, a portable computer, an image capture terminal device such as a digital camera, a gaming terminal device, a music storage and playback device, a mobile phone, a mobile phone, a smartphone, a voice over IP (VoIP) phone, a wireless local loop phone, a tablet, a wearable device, a personal digital assistant (PDA), a portable computer, a desktop computer, a wearable terminal device, an in-vehicle wireless terminal device, a wireless endpoint, a mobile station, a laptop embedded equipment (LEE), a laptop mounted equipment (LME), a USB dongle, a smart device, a wireless customer premises equipment (CPE), and the like. 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 according to one or more communications standards promulgated by 3GPP® (Third Generation Partnership Project), such as the 3GPP® LTE or NR standards. As used herein, "user equipment" or "UE" may not necessarily have a "user" in the sense of a human user who owns and / or operates the associated device. 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 on a predefined schedule, when triggered by an internal or external event, or in response to a request from the communication network. Instead, a UE may represent a device that is intended for sale to or operation by a human user, but is not initially associated with a particular human user.

[0119] As yet another example, in an Internet of Things (IoT) scenario, a terminal device may represent a machine or other device that performs monitoring and / or measurements and transmits results of such monitoring and / or measurements to another terminal device and / or network equipment. In this case, the terminal device may be a machine-to-machine (M2M) device, sometimes referred to in the 3GPP context as a machine-type communication (MTC) device. As one particular example, the terminal device may be a UE that implements the 3GPP Narrowband Internet of Things (NB-IoT) standard. Particular examples of such machines or equipment are sensors, metering devices such as power meters, industrial machines, or household or personal appliances, e.g., personal wearables such as refrigerators, televisions, and clocks. In other scenarios, the terminal device may represent a vehicle or other equipment that can monitor and / or report its operating state or other functions related to its operation.

[0120] References herein to "one embodiment," "one embodiment," "exemplary embodiment," and the like indicate that the described embodiment may include a particular feature, structure, or characteristic, but do not necessarily require that all embodiments include the particular feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with an embodiment, it will be understood that it is within the knowledge of one of ordinary skill in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[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 only to distinguish one element from another element. For example, a first element can be referred to as a second element, and similarly, a second element can be referred to as a first element, without departing from the scope of the exemplary embodiments. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed terms.

[0122] As 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 for the purpose of describing particular embodiments only and are not intended to limit the exemplary embodiments. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms unless the context clearly indicates otherwise. The terms "comprises," "comprising," "has," "having," "includes," and / or "including," as used herein, specify the presence of stated features, elements, and / or components, etc., but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0124] It should be noted that these terms used in this specification are used only to facilitate description and differentiation between nodes, devices, networks, etc. As the technology develops, other terms having similar / same 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 commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0126] Although the subject matter described herein focuses on the mismatch problem for roaming interworking between the V-SMF and the H-SMF, similar mismatch problems exist for scenarios in which the I-SMF (Intermediate SMF) and the anchor SMF have different recovery capabilities or configurations.

[0127] The following mismatch issues may be considered:

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

[0129] H-SMF failure: ● HPLMN has not deployed the SMF set. No problem. ● The HPLMN deploys the SMF set and the H-SMF supports the SMF set functionality. o V-SMF supports SMF sets and there are no issues with normal set handling. o The V-SMF does not support SMF sets (VPLMN may or may not deploy SMF sets to non-roaming users) and there is a mismatch between the V-SMF and the H-SMF. ● The HPLMN deploys SMF sets, but the H-SMF does not support the SMF set functionality. o The V-SMF supports a set of SMFs, and there is a mismatch between the V-SMF and the H-SMF. o The V-SMF does not support SMF sets (VPLMNs may or may not deploy SMF sets for non-roaming users) and in the HPLMN there is a mismatch between the H-SMF and other NFs, e.g., UDM (Unified Data Management) or PCF (Policy Control Function).

[0130] The following failure scenarios are considered: V-SMF failure: 1. V-SMF supports a set of SMFs for roaming interfaces (it is recommended to introduce new functions of the Nsmf_PDUSession service). aH-SMF supports SMF sets and the normal SMF set logic applies and is unchanged. bH-SMF does not support SMF sets, H-SMF can keep context standby for potential restoration triggered by AMF reselection of another V-SMF in the same set or delete affected PDU sessions (legacy behavior of H-SMF and AMF). AMF can request UE to reactivate PDU sessions based on local configuration if PDU sessions should be deleted. 2. V-SMF does not support SMF sets: The H-SMF deletes the affected PDU sessions, regardless of whether the H-SMF supports the SMF set or not. To cover 1b and 2a, it is desirable to define another new function so that the AMF and the H-SMF know that it is supported. H-SMF failure: 1. The H-SMF does not support the SMF set, and the V-SMF releases the PDU session. 2. H-SMF supports the SMF set (proposes to introduce new functionality for the Nsmf_PDUSession service). The aV-SMF supports a set of SMFs that apply reselection of another SMF within the same SMF set. bV-SMF does not support SMF sets, and the V-SMF releases the affected PDU sessions.

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

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

[0133] As shown in Figure 1, after detecting a V-SMF failure (i.e., vSMF1 failure), if the H-SMF does not support the SMF set, the H-SMF (i.e., hSMF1) initiates the release for the associated PDU session. However, since the V-SMF (i.e., vSMF1 failure) supports the SMF set, the AMF in the VPLMN reselects another SMF example (vSMF2) in the same SMF set A, and then the reselected vSMF2 restores the SM (session management) context and initiates an update request (update request) to the H-SMF (i.e., hSMF1). Nevertheless, the update request does not succeed because the H-SMF (i.e., hSMF1) has already triggered the release of the corresponding PDU session after detecting the vSMF1 failure. Since the vSMF2 has no clue about the PDU session state on the original H-SMF side, the 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, it will take time to reactivate all related PDU sessions, impacting service availability.

[0134] The messages shown in FIG. 1 may be the same as or similar to corresponding messages as described in 3GPP TS 23.502 V17.2.1, the disclosure of which is incorporated herein by reference in its entirety.

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

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

[0137] Note that this scenario may occur during development phases where the SMF vendor for the VPLMN has implemented a set of SMF functions for the SMF role, but has not yet implemented a set of SMF functions for the V-SMF role.

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

[0139] The messages shown in FIG. 2 may be the same as or similar to corresponding messages as described in 3GPP TS 23.502 V17.2.1, the disclosure of which is incorporated herein by reference in its entirety.

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

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

[0142] As shown in Figure 3, the H-SMF initiates the release for the associated PDU session if the H-SMF does not support SMF set based roaming resilience. When the VPLMN deploys the SMF set, the AMF in the VPLMN reselects another SMF in the same SMF set (for example, vSMF2). The AMF sends a Nsmf_PDUSession_UpdateSMContext request to the reselected vSMF2. Similarly, as a second failure scenario, the reselected vSMF2 does not have the logic to recover the session context and triggers a PDU session update request to hSMF1 with the callbackUri of the updated vSMF2 since the V-SMF does not support SMF set based roaming resilience. Instead, the reselected 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 session-by-session basis based on an error response from the V-SMF, which takes time to reactivate all related PDU sessions and affects service availability.

[0143] The messages shown in FIG. 3 may be the same as or similar to the corresponding messages as described in 3GPP TS 23.502 V17.2.1, the disclosure of which is incorporated herein by reference in its entirety.

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

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

[0146] As shown in Figure 4, when the V-SMF in the VPLMN detects that the hSMF1 in the SMF set B of the HPLMN has failed, the V-SMF for the existing PDU session does not reselect another SMF in SMF set B because the V-SMF does not support the SMF set function. Instead, the V-SMF triggers an SM context release to the AMF, which then triggers a 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.

[0147] The messages shown in FIG. 4 may be the same as or similar to corresponding messages as described in 3GPP TS 23.502 V17.2.1, the disclosure of which is incorporated herein by reference in its entirety.

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

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

[0150] This fifth failure scenario may occur during the development phase when the SMF vendor of the HPLMN has implemented an SMF set of functions for the SMF role, but has not yet implemented an SMF set of functions for the H-SMF role.

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

[0152] In a VPLMN, after detecting the failure of hSMF1, the V-SMF reselects another SMF (e.g. hSMF2) in the same SMF set B for the established PDU sessions and sends a PDU session update request to the reselected hSMF2. However, since hSMF2 does not have the logic to recover the session context, hSMF2 rejects the PDU session update request with “CONTEXT_NOT_FOUND”. As a result, the AMF in the VPLMN can only trigger PDU session reactivation per session based on the error response from the V-SMF, and it takes time to reactivate all related PDU sessions, affecting service availability. Also, if the reactivation selects an H-SMF in a different SMF set, ghost sessions may exist on the original H-SMF.

[0153] In the HPLMN, the surrounding 5GC (5G Core Network) NFs are considered as H-SMFs supporting the SMF set. For example, after the PCF detects the hSMF1 failure, it reselects another H-SMF in the same SMF set, but the reselected H-SMF does not have the application logic to recover the session context and process the notification request from the PCF. Depending on the implementation, if the H-UPF (Home UPF) does not release the context related to the failed hSMF1 (i.e., the H-UPF considers the hSMF1 in the SMF set), the downlink data can arrive at the V-UPF and the network-triggered service request procedure can succeed. However, the H-SMF does not process the UpdateNotify request (including the PCC rules for MT calls) from the PCF, so the call is not set up.

[0154] The messages shown in FIG. 5 may be the same as or similar to corresponding messages as described in 3GPP TS 23.502 V17.2.1, the disclosure of which is incorporated herein by reference in its entirety.

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

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

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

[0158] Depending on the implementation, if the H-UPF does not release the context related to the failed hSMF1 (i.e. the H-UPF that considers hSMF1 in its SMF set), the downlink data is sent to the V-UPF (visited V-UPF), but if the vSMF releases the related context, a GTP-U (GPRS (General Packet Radio Service) Tunneling Protocol for User Plane) error indication is returned. The H-UPF may send an 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 PCFs and other 5GC NFs in the HPLMN.

[0159] The messages shown in FIG. 6 may be the same as or similar to corresponding messages as described in 3GPP TS 23.502 V17.2.1, the disclosure of which is incorporated herein by reference in its entirety.

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

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

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

[0163] According to one embodiment, we introduce a "vSMF recovery indication" which means the capability to support PDU session restoration in case of a V-SMF failure. This requires that the AMF, V-SMF and H-SMF all support the capability such that PDU session restoration can function in case of a V-SMF failure.

[0164] According to one embodiment, if the above indication is not included in the request / response messages and SMF profile, it should be handled as the corresponding capability for roaming interworking is not supported.

[0165] According to one embodiment, the V-SMF and H-SMF are allowed to exchange (send and receive) information when their resource context is exclusively bound to a specific NF service instance, i.e., there is no resilience, which can be achieved by the following alternatives as described below.

[0166] According to one embodiment, through the NF Service Discovery procedure for SMF selection, the AMF can determine whether the resources served by the candidate V-SMF, or H-SMF, are exclusively bound to a particular NF service instance, i.e., there is no resilience in case of failure. The AMF is then proposed to populate this information to the V-SMF and H-SMF, for example in new attributes in the Create SmContext request to the V-SMF, which may preferably be called vSmfNoResilence and hsmfNoResilence, which may be defined as Boolean data and default to 0, and the V-SMF then forwards these new attributes in the Create PDU Session request towards the H-SMF.

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

[0168] In the proposed solution, it provides peer SMF clearing information if the SMF set is supported (at least for reselection in case of peer failure) and if the resources it contains can be shared by at least one alternative SMF.

[0169] Although the subject matter described herein may be implemented in any suitable type of system using any suitable components, the embodiments disclosed herein are described with respect to a communication system conforming to an exemplary system architecture shown in FIG. 7. For simplicity, the system architecture of FIG. 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, e.g., a landline, a service provider, or any other network node or terminal device. The communication system may provide communications and various types of services to one or more terminal devices to facilitate the terminal device's access to and / or use of services provided by or through the communication system.

[0170] FIG. 7 is a schematic diagram of a roaming 5G system architecture according to an embodiment of the present disclosure. The architecture of FIG. 7 is the same as FIG. 4.2.4-1 described in 3GPP TS 23.501 V17.2.0, the disclosure of which is incorporated herein by reference in its entirety. The system architecture of FIG. 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 Communication Proxy), NSACF (Network Slice Admission Control Function), vSEPP (Visited Security Edge Protection Proxy), and hSEPP (Home Security Edge Protection Proxy).

[0171] According to an example embodiment, the UE may establish a signaling connection with the AMF via reference point N1, as shown in Figure 7. This signaling connection may include a signaling connection between the UE and the (R)AN and an N2 connection between the (R)AN and the AMF for this UE, enabling NAS (Non-Access Stratum) signaling exchange between the UE and the core network. The (R)AN may communicate with the UPF over reference point N3. The UE may establish a Protocol Data Unit (PDU) session to a DN (data network, e.g., an operator network or the Internet) via the UPF over 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, that are 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, that can support interactions between NF services in the NFs. For example, these reference points can be realized by specifying several NF service consumers and providers and their interactions through corresponding NF service-based interfaces to perform certain system procedures.

[0173] The various NFs shown in Figure 7 may be responsible for functions such as session management, mobility management, authentication, security, etc. The 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] 8 illustrates a flowchart of a method according to an embodiment of the present disclosure, which may be performed by an apparatus implemented within, co-located with, or implemented as an Access and Mobility Function (AMF), or communicatively coupled to the AMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 800, as well as means or modules for accomplishing other processing in conjunction with other components.

[0175] In block 802, the AMF may obtain first information about whether a first session management function (SMF) supports a 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 may refer to the capability to support PDU session recovery in the event of a V-SMF failure.

[0177] The AMF may 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 may obtain the first information through NRF discovery. As another example, the AMF may obtain the first information from the first SMF if the first SMF can send a message including the first information to the AMF. As yet another example, the first information may be pre-configured in the network.

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

[0179] The AMF may obtain the second information in various ways. For example, the second SMF may register the second information with the NRF. In this case, the AMF may obtain the second information through NRF discovery. As another example, the AMF may obtain the second information from the second SMF, where the second SMF may send a message including 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 create session management (SM) context request to the first SMF. If the AMF, the first SMF, and the second SMF support the first capability, the PDU session create SM context request includes a first indication of supporting the first capability.

[0181] The Create PDU Session SM Context request may create an AMF-SMF association to support the PDU session. According to one embodiment, the Create PDU Session SM Context request may be the same as or similar to the 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] FIG. 9 illustrates a flowchart of obtaining first information about whether a first SMF supports a first capability according to an embodiment of the present disclosure.

[0184] According to one embodiment, the first SMF may register the first information with the NRF.

[0185] At block 902, the AMF may send a network function (NF) discovery request to a network repository function (NRF).

[0186] At block 904, the AMF may receive an NF discovery response including the 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] FIG. 10 illustrates a flowchart for obtaining second information about whether a second SMF supports a first capability according to an embodiment of the present disclosure.

[0189] According to one embodiment, the second SMF may register the second information with the NRF.

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

[0191] At block 1004, the AMF may receive an NF discovery response from the NRF including the 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] 11 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within the AMF, implemented in the same location as the AMF, implemented as the AMF, or executed by an apparatus communicatively coupled to the AMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 1100, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

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

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

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

[0197] In block 1108, the AMF may receive a create PDU session SM context response from the first SMF. If the first SMF supports the first capability, the create PDU session SM context response includes a 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 create PDU session 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.

[0198] Note that according to other embodiments, 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 may be obtained in other manners, for example via NRF discovery, so the PDU session creation SM context response may not include the first indication and an 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 a VPLMN, it means that the first SMF supports SMF set-based non-roaming PDU session resilience.

[0200] According to one embodiment, if a first SMF supports a peer NF set of a 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 a HPLMN, it means that the first SMF supports SMF set-based roaming PDU session resilience.

[0201] According to one embodiment, if a 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 a PDU session is established with the first SMF without other SMFs in other networks or network slices.

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

[0203] 12 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within the AMF, implemented in the same location as the AMF, implemented as the AMF, or executed by an apparatus communicatively coupled to the AMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 1200, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

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

[0205] According to an embodiment, the AMF may obtain third information about 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 may obtain the third information in various ways. For example, the first SMF may register the third information with the NRF. In this case, the AMF may obtain the third information through NRF discovery. As another example, the AMF may obtain the third information from the first SMF, if the first SMF may send a message including 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 fourth information regarding whether the second SMF supports a peer NF set for the first SMF.

[0208] According to an embodiment, the AMF may obtain fourth information about whether the second SMF supports a local network function (NF) configured for the second SMF and a peer NF 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 a user or UE in an 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 a 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 a peer SMF set for a user or UE in a 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 a PDU session is established with the second SMF without other SMFs in other networks or network slices.

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

[0213] The AMF may obtain the fourth information in various ways. For example, the second SMF may register the fourth information with the NRF. In this case, the AMF may obtain the fourth information through NRF discovery. As another example, the AMF may obtain the fourth information from the second SMF, if the second SMF may send a message including 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 including the third information and / or the fourth information.

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

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

[0217] FIG. 13 shows a flowchart of obtaining third information about whether a first SMF supports a local NF set for the first SMF and a peer NF set for the second SMF according to an embodiment of the present disclosure.

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

[0219] In block 1302, the AMF may send a network function (NF) discovery request to a network repository function (NRF).

[0220] In block 1304, the AMF may receive an NF discovery response from the NRF including the 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] FIG. 14 shows a flowchart for obtaining fourth information about whether a second SMF supports a local NF set for the second SMF and a peer NF set for the first SMF according to one embodiment of the present disclosure.

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

[0224] In block 1402, the AMF may send a network function (NF) discovery request to a network repository function (NRF).

[0225] At block 1404, the AMF may receive an NF discovery response from the NRF including the fourth 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] 15 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within the AMF, implemented in the same location as the AMF, implemented as the AMF, or executed by an apparatus communicatively coupled to the AMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 1500, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0228] 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 supports a peer NF set for the second SMF. The second SMF does not support a local NF set for the second SMF and a peer NF set for the first SMF.

[0229] In block 1502, the AMF may detect that the first SMF has failed upon receiving a notification from the NRF or using a PING frame. The AMF may receive an NF status notification request from the NRF including 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 reselect 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 a 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 indication in a CreateSMContext request to the selected V-SMF, and the V-SMF includes a vSMF roaming resilience indication and a vSMF recovery indication 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 the recovery, and the reselected first SMF includes updated vSMFId and vSmfPduSessionUri in an update request towards the second SMF.

[0234] 16 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented in, co-located with, or as an AMF, or may be executed by an apparatus communicatively coupled to the AMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 1600, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0235] 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 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 upon receiving a notification from the NRF or using a PING frame.

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

[0238] In block 1606, the AMF may send a SM context creation request to the SMF to re-establish the PDU session.

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

[0240] According to one embodiment, the SM context creation request includes information regarding whether the reselected SMF supports a peer NF set of the second SMF and / or information regarding whether the second SMF supports a peer NF set of the reselected SMF.

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

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

[0243] 17 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within the AMF, implemented in the same location as the AMF, implemented as the AMF, or executed by an apparatus communicatively coupled to the AMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 1700, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0244] 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 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 and a peer NF set for the first SMF.

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

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

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

[0248] According to one embodiment, the SM context creation request includes information regarding whether the reselected SMF supports a peer NF set of the second SMF and / or information regarding whether the second SMF supports a peer NF set of the reselected SMF.

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

[0250] 18 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented in, co-located with, or as an AMF, or may be executed by an apparatus communicatively coupled to the AMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 1800, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0251] 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.

[0252] In block 1802, the AMF may receive a PDU session SM context status notification including a resource state set as released and a cause of release due to reactivation from the first SMF.

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

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

[0255] 19 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within the AMF, implemented in the same location as the AMF, or implemented as the AMF, or executed by an apparatus communicatively coupled to the AMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 1900, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0256] 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 supports 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 including a resource state set as released and a cause of release due to reactivation from the first SMF.

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

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

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

[0261] 20a shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, co-located with, or as an AMF, or may be executed by an apparatus communicatively coupled to the AMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 2000, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are 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 including a resource state set as released and a cause of release due to reactivation from the first SMF.

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

[0265] According to one embodiment, the SM context creation request includes information regarding whether the first SMF supports a peer NF set of the reselected second SMF and / or information regarding whether the reselected second SMF supports a 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] 20b shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, co-located with, or as an AMF, or may be executed by an apparatus communicatively coupled to the AMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 2010, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0269] In block 2012, the AMF may obtain fifth 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 sixth 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 including the fifth information and / or the sixth information to the first SMF.

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

[0274] 21a shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, co-located with, or as the first SMF, or performed by an apparatus communicatively coupled to the first SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 2100, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0275] In block 2102, the first SMF may receive a PDU session create 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 may 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 of PDU session recovery in the event of a failure of the first SMF, the PDU session creation SM context request includes a first indication supporting the first capability.

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

[0280] According to an 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 a first indication.

[0282] According to one embodiment, 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 and a peer NF set for the first SMF, and the PDU session creation response 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.

[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 a peer NF set for the first SMF, the PDU session creation response includes an indication that the second SMF supports a 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 peer network function (NF) set for the second SMF and / or fourth information regarding whether the second SMF supports a peer NF set for the first SMF, and the PDU session creation request includes the third information and / or the fourth information.

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

[0287] According to one embodiment, the PDU session creation response includes information regarding whether the second SMF supports peer SMF reselection in the peer SMF set in case of failure of the original peer SMF instance.

[0288] According to some embodiments, to ensure that roaming resilience works end-to-end, it requires that both the vSMF and the hSMF support their own SMF set and a peer SMF set.

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

[0290] The meaning of its own SMF set ("roaming resilience indication") has two aspects: (1) it supports replication / backup of its own 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 an SMF pool so that context replication / switchover can occur after an SMF failure). When AMF discovers vSMF and hSMF, it can detect if there are multiple instances in the same SMF set / pool.

[0291] The meaning of "Peer SMF Set Support Indication" is a bit simpler: the SMF supports reselection of a peer SMF in a peer SMF set upon failure of the original SMF instance.

[0292] Based on that basis, the AMF sends both "vSMF roaming resilience indication" (its own vSMF set) and "hSMF roaming resilience indication" (its own hSMF set) to the vSMF in the Create SM Context request, and the vSMF relays that information to the hSMF. In such an exchange, the vSMF knows if a peer hSMF is deployed in its SMF set and the hSMF knows if the vSMF is deployed in its SMF set. Note that the "hSMF roaming resilience indication" is a bit of redundant information between the vSMF and hSMF interface, since the vSMF already learns it from the AMF in the Create SM Context request. But there is no problem to convey that information in the Create PDU request / response.

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

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

[0295] 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.

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

[0297] It may also extend the concept of "vSMF set indication" and "hSMF set indication" to cover the meaning of "vSMF roaming resilience indication" and "hSMF roaming resilience indication". It only requires sending and receiving "vSMF set indication" and "hSMF set indication". It actually makes sense to implement since vSMF set indication is based on vSMF resilience indication anyway and similar processing applies to hSMF as well. This solution actually replaces the parameter name resilience indication with set indication and extends the concept to mean "set indication" supports local set, peer set and multiple members in the same set.

[0298] 21b shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, co-located with, or as the first SMF, or performed by an apparatus communicatively coupled to the first SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 2100, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

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

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

[0301] 22 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, co-located with, or as the first SMF, or may be executed by an apparatus communicatively coupled to the first SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 2200, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0302] In block 2202, the first SMF may send a network function (NF) registration request to the NRF including an 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 capability of PDU session recovery upon 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] 23 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, co-located with, or as the first SMF, or performed by an apparatus communicatively coupled to the first SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 2300, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0307] In block 2302, the first SMF may receive a PDU session create SM context request from an access and mobility function (AMF). Block 2302 is the same as block 2102.

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

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

[0310] According to one embodiment, if the first SMF supports a 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 may 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 may receive a PDU session creation response from the second SMF. Block 2308 is the same as block 2106.

[0313] 24 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, co-located with, or as the first SMF, or performed by an apparatus communicatively coupled to the first SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 2400, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are 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 including 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 including the resource state set to be released and the cause of the release due to reactivation to the AMF.

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

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

[0319] 25 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, co-located with, or as the first SMF, or performed by an apparatus communicatively coupled to the first SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 2500, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0320] 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 supports 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 including information indicating that the second SMF has failed.

[0322] In block 2504, the first SMF may send a PDU session SM context status notification including the resource state set as released and the cause of the release by reactivation to the AMF.

[0323] In block 2506, the first SMF may receive a create PDU session SM context request from the AMF. If the AMF, the first SMF, and the SMF reselected to replace the second SMF support the first capability, the create PDU session SM context request includes a first indication.

[0324] In block 2508, the first SMF may send a create PDU session request to the reselected SMF. The create PDU session 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 reselected SMF to replace the second SMF support the first capability, the create PDU session request includes the first indication.

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

[0326] 26 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, co-located with, or as the first SMF, or performed by an apparatus communicatively coupled to the first SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 2600, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are 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 including information indicating that the second SMF has failed.

[0329] In block 2604, the first SMF may send a PDU session SM context status notification including the resource state set as released and the cause of the release by reactivation to the AMF.

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

[0331] In block 2608, the first SMF may send a PDU session creation request to the reselected 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] 27a shows a flowchart of a method according to another embodiment of the present disclosure. This flowchart can be executed by or communicatively coupled to an apparatus implemented in or as a second SMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 2700, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment 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 may 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 of PDU session recovery in the event of a failure of the first SMF, the PDU session creation request includes a first indication supporting 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 a first indication.

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

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

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

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

[0343] 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.

[0344] 27b shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, at, or as the second SMF, or may be performed by an apparatus communicatively coupled to the second SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 2710, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0345] In block 2712, the second SMF may determine fifth information about whether there is more than one SMF in the peer NF set for the first SMF. The create PDU session response includes the fifth information.

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

[0347] 28 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, at, or as the second SMF, or may be performed by an apparatus communicatively coupled to the second SMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 2800, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0348] In block 2802, the second SMF may send an NF registration request to the NRF including an 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 capability of PDU session recovery upon 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 comprises an indication of whether the second SMF supports a peer NF set for the first SMF (e.g., an hSMF roaming resilience indication).

[0352] 29 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, at, or as the second SMF, or may be executed by an apparatus communicatively coupled to the second SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 2900, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are 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 supports a peer NF set for the second SMF, and the second SMF does not support the local NF set for the second SMF or the peer NF set for the first SMF.

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

[0355] In block 2904, the second SMF may 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 reselected to replace the first SMF, the PDU session update request including an updated SMF identifier and an updated SMF PDU session uniform resource identifier.

[0357] 30 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, at, or as the second SMF, or may be executed by an apparatus communicatively coupled to the second SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 3000, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0358] 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 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 including information indicating that the first SMF has failed.

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

[0361] In block 3006, the second SMF may receive a PDU session creation request from the SMF reselected to replace the first SMF.

[0362] According to one embodiment, if the AMF, the SMF reselected to replace the first SMF, and the second SMF support a first capability, the PDU session create SM context request includes a first indication.

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

[0364] In block 3010, the second SMF may send a PDU session creation response to the SMF reselected 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 a first indication.

[0366] 31 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed in, or as, the second SMF, or by an apparatus communicatively coupled to the second SMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 3100, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0367] 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 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 does not support 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 including information indicating that the first SMF has failed.

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

[0370] In block 3106, the second SMF may receive a PDU session creation request from the SMF reselected to replace the first SMF.

[0371] According to one embodiment, if the AMF, the SMF reselected to replace the first SMF, and the second SMF support a first capability, the PDU session create SM context request includes a first indication.

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

[0373] In block 3110, the second SMF may send a PDU session creation response to the SMF reselected 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 a first indication.

[0375] 32 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, at, or as the second SMF, or may be performed by an apparatus communicatively coupled to the second SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 3200, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are 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 a 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 a Policy Control Function (PCF), a User Plane Function (UPF), and a Unified 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 one embodiment, the first SMF is an intermediate SMF and the second SMF is an anchor SMF.

[0380] 33 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed in or as a third network function, or by an apparatus communicatively coupled to the third network function. Thus, the apparatus may provide means or modules for achieving various parts of the method 3300, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are 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 for a resource context associated with the second SMF.

[0383] According to one embodiment, 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 by sending an NF discovery request to the NRF and receiving an NF discovery response from the NRF, the NF discovery response including 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, 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 by receiving a service request from the second SMF, where 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.

[0385] According to one embodiment, the third network function comprises at least one of a Policy Control Function (PCF), a User Plane Function (UPF), and a Unified 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] 34 shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed in, at, or as an NRF, or by an apparatus communicatively coupled to the NRF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 3400, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0388] At block 3402, the NRF may receive an NF registration request from the SMF, the NF registration request including an NF profile for the SMF.

[0389] At block 3404, the NRF may store the NF profile of the SMF.

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

[0391] According to an embodiment, when an 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 the local NF set for the first SMF and the 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, when 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 a local NF set for the second SMF and a peer NF set for the first SMF.

[0394] 35 shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within an NRF, implemented in the same location as an NRF, or implemented as an NRF, or executed by an apparatus communicatively coupled to an NRF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 3500, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

[0395] At block 3502, the NRF may receive a network capability discovery request from an access and mobility function (AMF).

[0396] In block 3504, the NRF may send a network capability discovery response to the AMF that includes at least one indication of an 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 description focuses on solutions for V-SMF and H-SMF roaming interworking, but the same solution principles also apply to scenarios where the I-SMF and anchor SMF have different resilience capabilities or configurations.

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

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

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

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

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

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

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

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

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

[0410] According to one embodiment, what is new that is added is an indication that there are multiple vSMFs in the same vSMF set and multiple hSMFs in the same hSMF set. Solution I: The AMF discovers through discovery that there are multiple vSMFs in the same vSMF set and / or multiple hSMFs in the hSMF set, and such information is sent by the AMF to the vSMF, e.g., "vSMF set indication" and "hSMF set indication". The vSMF relays the vSMF set indication to the hSMF. Solution II: The vSMF and hSMF themselves can discover such information. The vSMF and hSMF can discover other members in the same set through discovery based on their own implementation mechanisms, and the vSMF and hSMF can exchange (send and receive) such information. Solution III: Another possibility is to extend the concept of "vSMF set indication" and "hSMF set indication" to cover the meaning of "vSMF roaming resilience indication" and "hSMF roaming resilience indication" as well. We only need to exchange vSMF set indication with "hSMF set indication". It actually makes sense to do, since vSMF set indication is anyway based on vSMF resilience indication and the same applies to hSMF. This solution actually replaces the parameter name resilience indication with set indication and extends the concept to mean supporting local set, peer set and multiple members in the same set.

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

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

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

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

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

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

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

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

[0419] Solution for V-SMF failure: ● V-SMF supports the SMF set function. o H-SMF supports the following SMF sets: o Follow normal set handling. o H-SMF does not support SMF sets: o If the AMF, V-SMF and H-SMF support vSMF recovery, the H-SMF maintains the affected PDU sessions and waits for recovery to be triggered by the AMF reselecting another vSMF in the same V-SMF set and performing a PDU session update procedure, applicable to V-SMF failure scenario 1. o Otherwise, the H-SMF deletes the affected PDU session and the AMF requests the UE to reactivate the affected PDU session. - When V-SMF does not support the SMF set function o Whether the H-SMF supports SMF sets or not, o If the AMF, V-SMF and H-SMF support vSMF recovery, the H-SMF maintains the affected PDU session and waits for recovery, which is triggered by the AMF reselecting another vSMF and executing the PDU session Create on Create procedure. Applicable for V-SMF failure scenarios 2 and 3. o Otherwise, the H-SMF deletes the affected PDU session and the AMF requests the UE to reactivate the affected PDU session.

[0420] Solutions to H-SMF failures: ● H-SMF supports the SMF set function. o V-SMF supports SMF sets. Follow normal set handling. o V-SMF does not support SMF sets The oV-SMF releases the affected PDU sessions and the 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 Whether or not the V-SMF supports SMF sets, The V-SMF releases the affected PDU sessions and the AMF requests the UE to reactivate the affected PDU sessions. Applicable to H-SMF failure scenarios 5 and 6.

[0421] 37 illustrates a flowchart of an example solution for a V-SMF failure according to an embodiment of the present disclosure. Note that some parts described in the above embodiment are omitted for brevity.

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

[0423] The AMF includes a vSMF recovery indication in a CreateSMContext request to the selected V-SMF, and the V-SMF includes a vSMF roaming resilience indication and a vSMF recovery indication in a 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. To trigger the recovery, the AMF triggers a vSMF reselection for the established SM context in the update request, and the reselected V-SMF includes the updated vSMFId and vSmfPduSessionUri in the update request towards the original H-SMF.

[0425] In step 3701, the 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., the vSMF supports PDU session recovery in case of a vSMF failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., the vSMF supports roaming resilience) and / or an hSMF roaming resilience indication (i.e., the hSMF does not support roaming resilience).

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

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

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

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

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

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

[0433] In step 3708, the AMF triggers reselection of the vSMF for the established SM session.

[0434] In step 3709, the 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, the hSMF1 sends an Nsmf_PDUSession_Update response to the vSMF2.

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

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

[0439] 38 illustrates a flowchart of an exemplary solution for a V-SMF failure according to another embodiment of the present disclosure. Note that some parts described in the above embodiment are omitted for brevity.

[0440] Scenario 2 - The VPLMN deploys an SMF set, but the V-SMF does not support the SMF set and the H-SMF supports the SMF set.

[0441] The AMF includes a vSMF recovery indication in the CreateSMContext request directed to the selected vSMF. The V-SMF forwards the vSMF recovery indication received in the PDUSessionCreateRequest to the H-SMF, but the V-SMF does not include a vSMF roaming resilience indication and the 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 recovery. The AMF triggers PDU session reactivation to recover the affected PDU sessions, and the reselected V-SMF sends a PDUSessionCreateRequest towards the original H-SMF. The H-SMF accepts the new PDU session request by performing a Create on Create operation.

[0443] In step 3801, the 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., the vSMF supports PDU session recovery in case of a vSMF failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., the vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., the hSMF supports roaming resilience).

[0445] In step 3802, the vSMF1 sends an Nsmf_PDUSession_Create request to the 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, the hSMF1 sends a Nsmf_PDUSession_Create response to the vSMF1. According to one embodiment, the Nsmf_PDUSession_Create response includes a vSMF recovery indication (i.e., the hSMF supports PDU session recovery upon vSMF failure).

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

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

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

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

[0452] In step 3808, the 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., the vSMF2 supports PDU session recovery in case of a vSMF2 failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., the vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., the hSMF supports roaming resilience).

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

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

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

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

[0460] 39 shows a flowchart of an example solution for a V-SMF failure according to another embodiment of the present disclosure. Note that some parts described in the above embodiment are omitted for brevity.

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

[0462] The same recovery solution as in Scenario 2 applies, as shown below: after the failure of the selected V-SMF, the H-SMF maintains the associated PDU sessions and waits for their recovery. The AMF triggers a PDU session reactivation to recover the affected PDU sessions, and the reselected V-SMF sends a PDU session creation request towards the original H-SMF. The H-SMF accepts the new PDU session request by performing the Create on Create operation.

[0463] In step 3901, the 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., the vSMF supports PDU session recovery in case of a vSMF failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., the vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., the hSMF does not support roaming resilience).

[0465] In step 3902, the vSMF1 sends an Nsmf_PDUSession_Create request to the 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, the hSMF1 sends a Nsmf_PDUSession_Create response to the vSMF1. According to one embodiment, the Nsmf_PDUSession_Create response includes a vSMF recovery indication (i.e., the hSMF supports PDU session recovery upon vSMF failure).

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

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

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

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

[0472] Step 3908. The 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., the vSMF supports PDU session recovery in case of a vSMF failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., the vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., the hSMF does not support roaming resilience).

[0474] In step 3909, the vSMF2 sends an Nsmf_PDUSession_Create request to the 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, the hSMF1 executes the create on create process.

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

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

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

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

[0481] If the selected V-SMF does not support vSMF restore, the AMF does not include a vSMF recovery indication to the V-SMF. The V-SMF does not include a vSMF roaming resilience indication and a vSMF recovery indication in the PDUSessionCreateRequest to the selected H-SMF. Since the H-SMF detects that the V-SMF does not support roaming resilience, the H-SMF does not return a roaming resilience indication in response to the V-SMF. The H-SMF also suppresses roaming resilience indications in service requests towards surrounding 5GC NFs in the HPLMN.

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

[0483] The vSMF recovery indication is not used in the event of an H-SMF failure.

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

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

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

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

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

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

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

[0492] In step 4007, the PCF cleans up the context associated with the failed hSMF based on the capability indication in 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, the 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., the vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., the hSMF supports roaming resilience).

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

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

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

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

[0501] 41 shows a flowchart of an example solution for an H-SMF failure according to another embodiment of the present disclosure, in which some parts described in the above embodiment are omitted for brevity.

[0502] Scenario 5 - The HPLMN deploys an SMF set, but the H-SMF does not support the SMF set and the V-SMF supports the SMF set.

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

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

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

[0506] In step 4101, the 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., the vSMF supports PDU session recovery in case of a vSMF failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., the vSMF supports roaming resilience) and / or an hSMF roaming resilience indication (i.e., the hSMF does not support roaming resilience).

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

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

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

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

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

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

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

[0515] In step 4108, the 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., the vSMF supports PDU session recovery in case of a vSMF failure). According to another embodiment, the Nsmf_PDUSession_CreateSMContext request includes a vSMF roaming resilience indication (i.e., the vSMF supports roaming resilience) and / or an hSMF roaming resilience indication (i.e., the hSMF2 does not support roaming resilience).

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

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

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

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

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

[0522] 42a shows a flowchart of an example solution for H-SMF failure according to another embodiment of the present disclosure, where some parts described in the above embodiment are omitted for brevity.

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

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

[0525] In step 4201, the 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., the vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., the hSMF does not support roaming resilience).

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

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

[0530] In step 4204, the hSMF1 sends a Nsmf_PDUSession_Create response to the 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 the capability indication in 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 a Nsmf_PDUSession_SMContextStatusNotify response from AMF.

[0534] In step 4208, the 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., the vSMF does not support roaming resilience) and / or an hSMF roaming resilience indication (i.e., the hSMF does not support roaming resilience).

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

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

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

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

[0541] The following contents may be included in 3GPP (registered trademark) TS 23.527 V17.3.1. 6.X Home Routed PDU Session Recovery Procedure 6.X.1 Overview This clause specifies the requirements on the AMF, V-SMF and H-SMF for the restoration procedure when the SMF set feature is not supported in either the VPLMN or the HPLMN. The procedure specified in clause 6.5 is used to restore the home-routed PDU session by reselecting an alternative V-SMF or H-SMF if the V-SMF and H-SMF support the SMF set feature for roaming interfaces. If supported, the V-SMF and H-SMF can indicate support of the SMF set feature as described further below by setting the binding indication (i.e., the "3gpp-sbi-binding" HTTP header, see clause 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 the Service Request and Response messages, respectively. When or during the establishment of inter-AMF mobility procedures for a home-routed PDU session, if the (target) AMF supports the "Recovery by V-SMF Reselection on V-SMF Failure" (RVSMFR) functionality, it sets the corresponding feature bit in the supportFeatures attribute in the service request message directed to the V-SMF. The V-SMF sets the corresponding feature bit in the supportFeatures attribute in the Service Request message directed to the H-SMF if both the AMF and the V-SMF support the "Recovery by V-SMF Reselection on V-SMF Failure" (RVSMFR) feature. If the V-SMF supports the SETFRI feature, it sets the corresponding feature bit in the supportFeatures attribute in the Service Request message directed to the H-SMF and in the Service Response message directed to the AMF. The H-SMF sets the corresponding feature bit if it supports RVSMFR or SETFRI, respectively, in supportedFeatures in the Service Response message directed to the V-SMF. 6.X.2 V-SMF failure When the H-SMF detects a V-SMF failure, it extracts all PDU sessions related to the failed V-SMF and performs the following steps for those PDU sessions: ● If V-SMF supports the SETFRI function, ● And if the H-SMF supports the SETFRI functionality, the H-SMF can maintain the PDU session and reselect an alternative V-SMF when required, for example, for any request message to the V-SMF. ● And if the H-SMF does not support the SETFRI function but the H-SMF supports the RVSMFR function, the H-SMF maintains the PDU session and waits for the recovery of the PDU session triggered by the AMF reselecting another V-SMF in the same set if the V-SMF and the AMF support the RVSMFR function. Otherwise, the H-SMF deletes the affected PDU session. The AMF can 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 ● Whether the H-SMF supports the SETFRI function or not, the H-SMF may delete the affected PDU sessions. When the AMF detects a V-SMF failure, it extracts all PDU sessions related to the failed V-SMF and performs the following steps for those PDU sessions: a. ● If the H-SMF and AMF support the RVSMFR function, the AMF reselects an alternative V-SMF associated with the same NF (service) set as the failed V-SMF associated with the V-SMF if the V-SMF supports the SETFRI function. NOTE: If an SMF supports the SETFRI function, it is assumed that it also supports the SMF SET function for non-roaming reference points. ● Otherwise, the AMF may 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 the V-SMF detects a failure of an H-SMF, it extracts all PDU sessions related to the failed H-SMF and performs the following steps for those PDU sessions: ● If the H-SMF does not support the SETFRI function, the V-SMF releases the affected PDU sessions. ● If the H-SMF supports the SETFRI functionality, the V-SMF may select another H-SMF if the V-SMF also supports the SETFRI functionality, otherwise the V-SMF releases the PDU session. NOTE: Resources related to the affected PDU session in the HPLMN do not need to be maintained even if the H-SMF supports SMF sets.

[0542] 42b shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within the AMF, implemented in the same location as the AMF, or implemented as the AMF, or executed by an apparatus communicatively coupled to the AMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 4214, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are 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 fourth information regarding whether the second SMF supports reselection 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 reselect an alternative service instance within the SMF set of the first SMF based on the third information and the fourth information.

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

[0548] ● If the H-SMF supports the "Peer NF Set Based Reselection" (PSETR) functionality (e.g., fourth piece of information) and the V-SMF supports the "Deployed Local SMF Set" (DLSET) functionality (e.g., third piece of information), the AMF shall maintain the PDU session and should, for example, reselect an alternative V-SMF service instance when it needs to send any request message to the V-SMF.

[0549] ● If the H-SMF does not support the PSETR functionality while the V-SMF supports the DLSET functionality, the AMF may reselect an alternative V-SMF service instance to maintain the PDU session and request the selected alternative V-SMF to delete the PDU session towards the UE and the UPF. The V-SMF may request the UE to reactivate the PDU session.

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

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

[0553] According to one embodiment, obtaining the third information may include receiving a service response message or a service request message including 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 including the fourth information.

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

[0556] 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 reselecting 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 reselection of 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 the third information and the fourth information may further include, if the third information indicates that resources are not exclusively bound to a particular service instance in the first SMF and the fourth information indicates that the second SMF does not support reselection of the alternative first SMF 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 toward a user equipment (UE).

[0558] According to one embodiment, reselecting an alternative service instance in 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 if the third information indicates that the resource is exclusively bound to a particular service instance in the first SMF.

[0559] 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.

[0560] 42c shows a flowchart of a method according to another embodiment of the present disclosure, which may be performed in the AMF, in the AMF, as the AMF, or by an apparatus communicatively coupled to the AMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 4220, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

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

[0562] In block 4224, the AMF may send the fifth information to the first SMF.

[0563] 42d shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, co-located with, or as the first SMF, or performed by an apparatus communicatively coupled to the first SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 4230, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

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

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

[0566] For example, when the V-SMF detects a failure of an H-SMF, it extracts all PDU sessions related to the failed H-SMF and performs the following steps for those PDU sessions:

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

[0568] ● If the V-SMF supports the PSETR function: ● If the H-SMF supports the DLSET functionality (e.g., fifth information), the V-SMF can maintain the PDU session and reselect an alternative H-SMF service instance, e.g., if it needs to send any request message to the H-SMF. ● If the H-SMF does not support the DLSET function, the V-SMF may release the PDU session towards the AMF and the UE, and the V-SMF may request the UE to reactivate the PDU session.

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

[0570] 42e shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, co-located with, or as the first SMF, or performed by an apparatus communicatively coupled to the first SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 4240, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

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

[0572] In block 4244, the first SMF may send to the AMF fourth information about whether the second SMF supports reselection of an alternative first SMF instance in the SMF set of the first SMF. The third information and the fourth information may be used by the AMF to reselect an alternative service instance in the SMF set of the first SMF when the first SMF fails.

[0573] 42f shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, co-located with, or as the first SMF, or performed by an apparatus communicatively coupled to the first SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 4250, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

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

[0575] According to one embodiment, the first SMF may 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 information may be included in an update SM context response message.

[0578] FIG. 42g shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within, co-located with, or as the first SMF, or performed by an apparatus communicatively coupled to the first SMF. Thus, the apparatus may provide means or modules for accomplishing various parts of the method 4260, as well as means or modules for accomplishing other processes in conjunction with other components. Note that some parts described in the above embodiment are omitted for brevity.

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

[0580] 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.

[0581] 42h shows a flowchart of a method according to another embodiment of the present disclosure, which may be implemented within the second SMF, implemented in the same location as the second SMF, implemented as the second SMF, or executed by an apparatus communicatively coupled to the first SMF. Thus, the apparatus may provide means or modules for achieving various parts of the method 4270, as well as means or modules for achieving other processes in conjunction with other components. Note that some parts described in the above embodiment are 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 fourth information regarding whether the second SMF supports reselection of an alternative first SMF instance within the SMF set of the first SMF.

[0584] For example, when the H-SMF detects a failure of a V-SMF, it extracts all PDU sessions related to the failed V-SMF and performs the following steps for those PDU sessions:

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

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

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

[0588] 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.

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

[0590] The apparatus 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 apparatus 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 include instructions that, when executed on the associated processor 4321, enable the apparatus 4300 to operate according to an embodiment of the present disclosure. The combination of the at least one processor 4321 and the at least one MEM 4322 may form a processing means 4325 adapted to implement various embodiments of the present disclosure.

[0591] Various embodiments of the present disclosure may be implemented by computer programs executable by one or more of the processor 4321, software, firmware, hardware, or combinations thereof.

[0592] The MEM4322 may be implemented using any suitable data storage technology, such as, for example, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed and removable memory.

[0593] The processor 4321 may be of any type suitable for the local technology environment and may include, by way of non-limiting examples, one or more of a general purpose computer, a special purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture.

[0594] According to one embodiment in which the apparatus is implemented as or in the same location as an AMF, the memory 4322 includes instructions executable by the processor 4321, thereby causing the AMF to operate according to any of the methods associated with the AMF described above.

[0595] According to an embodiment in which the apparatus is implemented as or co-located with the first SMF, the memory 4322 includes instructions executable by the processor 4321, whereby the first SMF operates according to any of the methods associated with the first SMF, as described above.

[0596] According to an embodiment in which the apparatus is implemented as or co-located with the second SMF, the memory 4322 includes instructions executable by the processor 4321, whereby the second SMF operates according to any of the methods associated with the second SMF, as described above.

[0597] According to an embodiment in which the apparatus is implemented as or co-located with a third NF, the memory 4322 includes instructions executable by the processor 4321 to cause the third NF to operate according to any of the methods relating to the third NF, as described above.

[0598] According to an embodiment in which the apparatus is implemented as or co-located with an NRF, the memory 4322 includes instructions executable by the processor 4321, which causes the NRF to operate according to any of the methods relating to an NRF, as described above.

[0599] FIG. 44 is a block diagram illustrating an AMF according to an embodiment of the present disclosure. As shown in the figure, the AMF 4400 comprises 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 an embodiment, the AMF 4400 may further comprise a second acquisition module 4402 configured to acquire fourth information regarding whether the second SMF supports reselection of an alternative first SMF instance in the SMF set of the first SMF. The AMF 4400 may further comprise a detection module 4403 configured to detect that the first SMF has failed. The AMF 4400 further comprises a reselection module 4404 configured to reselect an alternative service instance in the SMF set of the first SMF based on the third information and the fourth information.

[0600] According to one embodiment, the AMF 4400 may further include a third acquisition module 4405, which is configured to acquire fifth information regarding whether a resource is exclusively bound to a particular service instance in the second SMF.

[0601] According to one embodiment, the AMF 4400 may further include a transmitting module 4406 configured to transmit the fifth information to the first SMF.

[0602] 45 is a block diagram illustrating a first SMF according to an embodiment of the present disclosure. As shown, the first SMF 4500 may include a first sending module 4501 configured to send to the AMF third information 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 sending module 4502 configured to send to the AMF fourth information regarding whether the second SMF supports reselection of an alternative first SMF instance in the SMF set of the first SMF.

[0603] According to one embodiment, the third information and the fourth information may be used by the AMF to reselect 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 obtaining module 4503 configured to obtain fifth 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 obtaining module 4504 configured to obtain sixth information about whether the first SMF supports reselection of an alternative second SMF instance in the SMF set of the second SMF.

[0605] According to one embodiment, the first SMF 4500 may further comprise a third acquisition module 4505 configured to acquire the fourth information.

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

[0607] 46 is a block diagram illustrating a second SMF according to one embodiment of the present disclosure. As shown, the second SMF 4600 comprises a receiving module 4601 configured to receive, from the first SMF, third information regarding whether a resource is exclusively bound to a particular service instance in the first SMF. The second SMF 4600 may further comprise an acquiring module 4602 configured to acquire fourth information regarding whether the second SMF supports reselection of an alternative first SMF instance in the SMF set of the first SMF.

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

[0609] Embodiments herein may provide many advantages, a non-exhaustive list of examples of which follows below. According to some embodiments herein, a recovery procedure is proposed for recovering PDU sessions affected by SMF failures. According to some embodiments herein, the time to recover PDU sessions affected by SMF failures may be reduced. According to some embodiments herein, the ghost session problem may be resolved. According to some embodiments herein, the availability of services may be improved. The embodiments herein are not limited to the features and advantages described above. Those skilled in the art will recognize additional features and advantages upon reading the following detailed description.

[0610] The term unit or module may have its conventional meaning in the field of electronic equipment, electrical devices and / or electronic devices and may include, for example, electric and / or electronic circuits, devices, modules, processors, memories, logic solid state and / or discrete devices, computer programs or instructions for performing a respective task, procedure, computation, output and / or display function, etc., as described herein.

[0611] In the 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 may be configured in the AMF, the first SMF, or the second SMF in the communication system. The introduction of virtualization technology and network computing technology can improve the utilization efficiency of network resources and the flexibility of the network.

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

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

[0614] Furthermore, the present disclosure may provide a carrier containing the above-mentioned computer program, the carrier being one of 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 a RAM (random access memory), a ROM (read only memory), a flash memory, a magnetic tape, a CD-ROM, a DVD, a Blu-ray disc, etc.

[0615] The techniques described herein may be implemented by various means, including separate means for each separate function, or means that may be configured to perform two or more functions, such that an apparatus implementing one or more functions of a corresponding apparatus described with the embodiments includes not only conventional means, but also means for implementing one or more functions of a corresponding apparatus described with the embodiments. 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. The firmware or software may be implemented via modules (e.g., procedures, functions, etc.) that perform the functions described herein.

[0616] Exemplary embodiments of the present specification have been described above with reference to block diagrams and flowchart diagrams of methods and apparatuses. It will be understood that each block of the block diagrams and flowchart diagrams, and combinations of each block of the block diagrams and flowchart diagrams, can be implemented by various means including computer program instructions. These computer program instructions can be loaded onto a general purpose computer, special purpose computer, or other programmable data processing apparatus to generate a machine such that the instructions, which execute on the computer or other programmable data processing apparatus, create means for implementing the functions specified in one or more of the flowchart blocks.

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

[0618] Although the present specification contains many specific implementation details, these should not be construed as a limitation on the scope of any implementation or what may be claimed, but rather as a description of features that may be specific to a particular embodiment of a particular implementation. Certain features described in the present specification 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 in multiple embodiments separately or in any suitable subcombination. Furthermore, features may be described above as acting in a particular combination, and even as initially claimed, one or more features from a claimed combination may, in some cases, be separated from the combination, and the claimed combination may be directed to a subcombination or a variation of the subcombination.

[0619] It will be obvious to those skilled in the art that as technology advances, the concept of the present disclosure can be implemented in various ways. The above embodiments are given to illustrate, not to limit, the present disclosure, and it should be understood that modifications and variations can be utilized without departing from the spirit and scope of the present disclosure, as those skilled in the art will easily understand. Such modifications and changes are considered to be within the scope of the present disclosure and the appended claims. The scope of protection of the present disclosure is defined by the appended claims.

Claims

1. A method (4214) performed by an Access and Mobility Function (AMF), comprising: Obtaining (4215) third information regarding whether a resource is exclusively bound to a particular service instance in a first session management function (SMF); Obtaining fourth information regarding whether the second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF (4216); Detecting that the first SMF has failed (4217); and reselecting an alternative service instance within the SMF set of the first SMF based on the third information and the fourth information (4218); and The method comprising:

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

3. 3. The method according to claim 1, wherein obtaining the third information comprises: sending a Network Function (NF) discovery request to a Network Repository Function (NRF); receiving an NF discovery response from the NRF, the NF discovery response including the third information; A method comprising:

4. 4. The method according to claim 1, wherein obtaining the third information comprises: receiving a service response message or a service request message from the first SMF, the service response message or the service request message including the third information; A method comprising:

5. 5. The method according to claim 1, wherein obtaining the fourth information comprises: sending an NF discovery request to the NRF; receiving an NF discovery response from the NRF, the NF discovery response including fourth information; A method comprising:

6. 6. The method according to claim 1, wherein obtaining the fourth information comprises: receiving an update session management (SM) context response message from the first SMF, the SM context response message including the fourth information; A method comprising:

7. 7. The method according to claim 1, wherein the reselection of an alternative service instance in the SMF set of the first SMF based on the third information and the fourth information comprises: reselecting the alternative V-SMF service instance in the SMF set of the first SMF if the third information indicates that resources are not exclusively bound to the particular service instance in the first SMF and the fourth information indicates that the second SMF supports reselection of the alternative first SMF instance in the SMF set of the first SMF; A method comprising:

8. 8. The method according to claim 1, wherein the reselection of an alternative service instance in the set of SMFs of the first SMF based on the third information and the fourth information comprises: 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 does not support reselection of the alternative first SMF instance in the SMF set of the first SMF; reselecting the alternative first SMF service instance within 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 towards a user equipment (UE); A method comprising:

9. 9. The method according to claim 1, wherein the reselection of an alternative service instance in the set of SMFs of the first SMF based on the third information and the fourth information comprises: Releasing at least one affected PDU session without reselecting the alternative first SMF service instance if the third information indicates that the resource is exclusively bound to the particular service instance in the first SMF; A method comprising:

10. The 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. The method according to any one of claims 1 to 10, further comprising: Obtaining fifth information regarding whether a resource is exclusively bound to a particular service instance in the second SMF (4222); and Sending the fifth information to the first SMF (4224); and The method comprising:

12. A method (4240) performed by a first session management function (SMF), comprising: Sending third information to the AMF about whether the resource is exclusively bound to a particular service instance in the first SMF (4242); and and sending to the AMF fourth information about whether the second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF (4244); The third information and the fourth information are used by the AMF to reselect an alternative service instance in the SMF set of the first SMF when the first SMF fails.

13. 13. The method of claim 12 further comprising: obtaining the fourth information (4252); The method comprising:

14. 14. The method of claim 13, wherein obtaining the fourth information comprises: receiving the fourth information from the second SMF; A method comprising:

15. The method according to any one of claims 12 to 14, further comprising: sending the third information to the second SMF (4262); The method comprising:

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

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

18. The 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. The method according to any one of claims 12 to 18, further comprising: Obtaining fifth information about whether the resource is exclusively bound to a particular service instance in the second SMF (4232); and Obtaining sixth information about whether the first SMF supports reselection of an alternative second SMF instance in an SMF set of the second SMF (4234); The method comprising:

20. 20. The method of 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), comprising: receiving third information from the first SMF about whether a resource is exclusively bound to a particular service instance in the first SMF (4272); Obtaining fourth information about whether the second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF (4274); The method comprising:

22. 22. The method of claim 21 further comprising: sending to the first SMF fifth information regarding whether a resource is exclusively bound to a particular service instance in the second SMF (4276); The method comprising:

23. 23. The method of 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. An Access and Mobility Function (AMF) (4300), A processor (4321); and a memory (4322) coupled to the processor (4321), the memory (4322) including instructions executable by the processor (4321), whereby the AMF (4300) Obtain third information regarding whether the resource is exclusively bound to a particular service instance in the first session management function (SMF); Obtaining fourth information regarding whether the second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF; Detecting that the first SMF has failed; reselecting an alternative service instance within the SMF set of the first SMF based on the third information and the fourth information; AMF operates like this.

25. 25. The AMF of claim 24, wherein the AMF is further operable to perform a method according to any one of claims 2 to 11.

26. A first session management function (SMF) (4300), A processor (4321); and a memory (4322) coupled to the processor (4321), the memory (4322) including instructions executable by the processor (4321), whereby the first SMF (4300) Sending third information to the AMF regarding whether a resource is exclusively bound to a particular service instance in the first SMF; The second SMF sends to the AMF fourth information regarding whether the second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF; It works like this: A first SMF, wherein the third information and the fourth information are used by the AMF to reselect an alternative service instance within the SMF set of the first SMF when the first SMF fails.

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

28. A second session management function (SMF) (4300), A processor (4321); and a memory (4322) coupled to the processor (4321), the memory (4322) including instructions executable by the processor (4321), whereby the second SMF (4300) receiving third information from a first SMF regarding whether a resource is exclusively bound to a particular service instance within the first SMF; Obtaining fourth information about whether the second SMF supports reselection of an alternative first SMF instance in an SMF set of the first SMF; The second SMF operates as follows:

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

30. A computer readable storage medium storing instructions which, when executed by at least one processor, cause the at least one processor to perform the method of any one of claims 1 to 23.

31. A computer program product comprising instructions which, when executed by at least one processor, cause said at least one processor to perform the method of any one of claims 1 to 23.

Images