Subscription of an UPF event via an i-SMF / v-smf

Abstract

Disclose herein is a method performed by a first SMF, in a core network of a cellular communications system, the method comprises: receiving (Fig. 3, step 3) a first PDU, session update request from a second SMF, wherein the first PDU session update request comprises any one or more of the following: information that indicates one or more supported PFCP features of a User Plane Function, UPF, selected by the second SMF; information that indicates one or more UPF events exposed or supported by the UPF; an apiRoot of an event exposure service Application Programming Interface, API, of the UPF. The method further comprises sending (Fig. 3, step 5) a second PDU session update request to the second SMF, the second PDU session update request comprising UPF event subscription related information.

Description

[0001] SUBSCRIPTION OF AN U PF EVENT VIA AN I-SMF / V-SMF

[0002] Technical Field

[0003] The non-limiting and exemplary embodiments of the present disclosure generally relate to the technical field of communications, and specifically to methods and apparatuses for Session Management.

[0004] Background

[0005] Standardization work has been ongoing on Next Generation Radio Access Network (NG-RAN) and 5G Core (5GC) as new radio access and new packet core network since 3GPP Rel-15 (see 3GPP Technical Specifications (TS) 23.501 and 23.502 for stage-2 descriptions).

[0006] Figure 1

[0007] Figure 1 shows 5G System architecture using service-based representation as described in 3GPP TS 23 501 V18.5 0. In particular, Figure 1 corresponds to Figure 4.2 3-1 from 3GPP TS 23.501 V18.5.0.

[0008] In the 5GC, 3GPP TS 23.502 V18.5.0 clause 4.15.4.5 specifies “Exposure of Events from UPF for UPF Data Collection ” Clause 4.15.4.5.2 specifies “Information flow for subscription to UPF event exposure service for certain UE(s) via SMF” and is reproduced below in the following excerpt from 3GPP TS 23.502 V18.5.0.

[0009] ***** START EXCERPT FROM 3GPP TS 23.502 *****

[0010] 4.15.4.5.2 Information flow for subscription to UPF event exposure service for certain UE(s) via SMF

[0011] [REPRODUCED HEREIN AS FIGURE 2]

[0012] Figure 4.15.4.5.2-1 : Subscription to UPF event exposure service for certain UE(s) via SMF

[0013] In the case of a group of UEs, the UPF event consumer (e.g. NWDAF) first issues an Nnrf NFDiscovery Request service operation to find the UDM providing the target Group ID and gets the NF profile of the UDM serves this group. Then, NWDAF obtains the list of SUPIs that correspond to the Group ID from UDM using Nudm SDM Get

[0014] NOTE 1 : It is assumed that all members of a Group ID belong to the same UDM.

[0015] Then, for each SUPI:

[0016] 1. The UPF event consumer (e.g. NWDAF) invokes Nudm UECM Get service operation to retrieve the appropriate SMF by providing UE ID, DNN, S -NS SAI and NF type = SMF.

[0017] 2. The UDM provides a Nudm UECM Get response with the corresponding SMF.

[0018] 3. The UPF event consumer sends the Nsmf EventExposure Subscription request to the SMF to subscribe to UPF data, including the following information:

[0019] - Notification Target Address (UPF event consumer address), Notification Correlation Information. - Indication of UPF Event Exposure Service and Target subscription UPF Event Id.

[0020] - Event Filter Information: S-NSSAI, DNN, DNAI,UPF Id, Traffic Description for the target traffic (e g. Application Id), Area of Interest, SSID / BSSID.

[0021] - Target of Event Reporting: a UE.

[0022] - Reporting suggestion information.

[0023] - Target Subscription information: Type of Measurement and granularity of the information requested.

[0024] If the consumer is NWDAF and the analytic filter information includes application server IP address / FQDN, the NWDAF may need to first obtain the DNAI from NEF as described in steps 2 and 3 in Figure 4.15.4.5.3- 1.

[0025] 4. The SMF selects the PDU session(s) and the UPFs it has to send the request to. The SMF sends the request to the UPF including the UPF event consumer address, Notification Correlation Information, Event Filter Information, Reporting suggestion information, Target of Event Reporting and Target Subscription Information as required. Target of Event Reporting is a certain UE. The interaction mechanism used between SMF and UPF depends on UPF exposure event and which mechanism applies for each event as described in clause 5.2.26.2.1. For some events, the SMF shall contact UPF (4a) with N4 Session Modification with PFCP (TS 29.244

[0069] ), for other events (4b) with Nupf event exposure subscribe request (as defined in clause 5.2.26.2.3).

[0026] NOTE 2: Some events can require SMF interacts with RAN at this stage.

[0027] 5. Per Reporting suggestion information (if available), the UPF sends the locally collected UPF data by invoking Nupf EventExposure Notify service operation to the UPF event consumer.

[0028] ***** END EXCERPT FROM 3GPP TS 23.502 *****

[0029] As agreed in Change Request (OR) 4786 (see S2-2405685) for 3GPP TS 23.502 18.5.0:

[0030] To get exposure data from UPF, NF consumer may subscribe to the UPF indirectly via SMF. But, if the UPF is inserted by l-SMF that SMF cannot serve the target DNAI for the traffic routing for local access to the DN, the SMF can’t directly subscribe the event in UPF. The SMF should send the subscription to UPF via l-SMF.

[0031] For this case, the SMF should sent the subscription to l-SMF, and the l-SMF represents the SMF to subscribe to UPF.

[0032] The summary of CR 4786 is described in S2-2405685 as follows:

[0033] If l-SMF is used for this PDU session, for UPF events (except the QoS monitoring) involving UPFs controlled by the l-SMF, the SMF sends the Nsmf_PDUSession_Update including the UPF event subscription related information to l-SMF.

[0034] Towards the upcoming 3GPP meeting CT4#123, Huawei proposed a related CR CR 0782 (see C4-242152) for 23.502 to update the Nsmf_PDUSession_Update service. In this CR, it is proposed to simply add "upfSubscriptionlnfo" in the VsmfUpdateData sent from the Session Managmement Function (SMF) to Intermediate SMF (l-SMF), to request the I- SMF to create a User Plane Function (UPF) event subscription in the local Protocol Data Unit (PDU) Session Anchor (PSA) UPF by invoking Nupf_EventExposure service. Summary

[0035] 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.

[0036] To overcome or mitigate at least one problem mentioned herein or other problems, a solution is proposed to enable a Home Session Management Function [i.e. a (H-)SM F] to create an event subscription in a local PDU Session Anchor User Plane Function [i.e. a PSA UPF] (for a PDU session with an l-SMF) or in a PSA UPF in the Visiting PLMN (for a Home-Routed PDU Session), via the Intermediate Session Management Function [i.e. I-SMF] or the Visited Session Management Function [i.e. V-SMF] respectively. While not limited to the above mentioned proposed solution or any particular advantage provided by that solution, other solutions disclosures herein may provide a number of advantages over existing technology.

[0037] One solution disclosed heerin is directed to a method performed by a first SMF in a core network of a cellular communications system and to a first SMF performing the method, the method comprising:

[0038] • receiving (Fig. 3, step 3) a first Protocol Data Unit, PDU, session update request from a second SMF, wherein the first PDU session update request comprises any one or more of the following: o information that indicates one or more supported PFCP features of a User Plane Function, UPF, selected by the second SMF; o information that indicates one or more UPF events exposed or supported by the UPF; o an apiRoot of an event exposure service Application Programming Interface, API, of the UPF;

[0039] • sending (Fig. 3, step 5) a second PDU session update request to the second SMF, the second PDU session update request comprising UPF event subscription related information.

[0040] Anoither solution disclosed heerin is directed to a method performed by a second SMF in a core network of a cellular communications system and to a second SMF performing the method, the method comprising:

[0041] • sending (Fig. 3, step 3) a first Protocol Data Unit, PDU, session update request to a first SMF, wherein the first PDU session update request comprises any one or more of the following: o information that indicates one or more supported PFCP features of a User Plane Function, UPF, selected by the second SMF; o information that indicates one or more UPF events exposed or supported by the UPF; o an apiRoot of an event exposure service Application Programming Interface, API, of the UPF;

[0042] • receiving (Fig 3, step 5) a second PDU session update request from the first SMF, the second PDU session update request comprising UPF event subscription related information

[0043] Now, the description will turn to a more detailed description of some example embodiments of the present disclosure Brief Description of the Drawings

[0044] The above and other aspects, features, and benefits of various embodiments of the present disclosure will become more fully apparent, by way of example, from the following detailed description with reference to the accompanying drawings, in which like reference numerals or letters are used to designate like or equivalent elements. The drawings are illustrated for facilitating better understanding of the embodiments of the disclosure and not necessarily drawn to scale, in which:

[0045] FIG. 1 illustrates 5G System architecture using service-based representation as described in 3GPP TS 23.501 V18.5.0.;

[0046] FIG. 2 illustrates a Subscription to UPF event exposure service for certain UE(s) via SMF as described in 3GPP TS 23.502 clause 4.15.4.5.2 and Figure 4.15.4.5.2-1 therein;

[0047] FIG. 3 illustrates a procedure for when an l-SMF is inserted and the SMF requests the l-SMF to invoke Nupf_EventExposure service to create event subscription in the l-UPF (which has a local PSA UPF function);

[0048] FIG.4 is a schematic block diagram of a network node 400 according to some embodiments of the present disclosure;

[0049] FIG. 51 is a schematic block diagram that illustrates a virtualized embodiment of the network node 400 according to some embodiments of the present disclosure.

[0050] Detailed Description

[0051] Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art. Radio Node: As used herein, a ‘‘radio node” is either a radio access node or a wireless communication device.

[0052] Radio Access Node: As used herein, a “radio access node" or “radio network node" or “radio access network node” is any node in a Radio Access Network (RAN) of a mobile network that operates to wirelessly transmit and / or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3GPP) Fifth Generation (5G) NR network or an enhanced or evolved Node B (eNB) in a 3GPP Long Term Evolution (LTE) network), a high-power or macro base station, a low- power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), a relay node, a network node that implements part of the functionality of a base station (e.g., a network node that implements a gNB Central Unit (gNB-CU) or a network node that implements a gNB Distributed Unit (gNB-DU)) or a network node that implements part of the functionality of some other type of radio access node.

[0053] Core Network Node: As used herein, a “core network node” is any type of node in a core network or any node that implements a core network function. Some examples of a core network node include, e g., a Mobility Management Entity (MME), a Packet Data Network Gateway (P-GW), a Service Capability Exposure Function (SCEF), a Home Subscriber Server (HSS), or the like. Some other examples of a core network node include a node implementing an Access and Mobility Management Function (AMF), a User Plane Function (UPF), a Session Management Function (SMF), an Authentication Server Function (AUSF), a Network Slice Selection Function (NSSF), a Network Exposure Function (NEF), a Network Function (NF) Repository Function (NRF), a Policy Control Function (PCF), a Unified Data Management (UDM), or the like.

[0054] Communication Device: As used herein, a “communication device'' is any type of device that has access to an access network. Some examples of a communication device include, but are not limited to: mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or Personal Computer (PC). The communication device may be a portable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and / or data via a wireless or wireline connection.

[0055] Wireless Communication Device: One type of communication device is a wireless communication device, which may be any type of wireless device that has access to (i.e., is served by) a wireless network (e.g. , a cellular network). Some examples of a wireless communication device include, but are not limited to: a User Equipment device (UE) in a 3GPP network, a Machine Type Communication (MTC) device, and an Internet of Things (loT) device. Such wireless communication devices may be, or may be integrated into, a mobile phone, smartphone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or PC. The wireless communication device may be a portable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and / or data via a wireless connection.

[0056] Network Node: As used herein, a “network node” is any node that is either part of the RAN or the core network of a mobile network.

[0057] Note that the description given herein focuses on a 3GPP mobile network and, as such, 3GPP terminology or terminology similar to 3GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3GPP mobile network.

[0058] There currently exist certain problems. As agreed in CR 4786 (S2-2405685) for 3GPP TS 23.502, which is targeting the a PDU session with an l-SMF inserted, the reason to insert an l-SMF is mainly because the UE enters an area which is out of the Anchor SMF service area, i.e. there is no UPF (under the control of the said SMF) which can serve the UE If an l-SMF is inserted, it is likely that the l-SMF will select a Uplink Classifier or Internet Protocol (IP) Version 6 (IPv6) Branching Point to offload some of the application traffic to a local Data Network via a Local PSA UPF In such a scenario, i.e. when a local PSA UPF is inserted by l-SMF, if the SMF needs to create an UPF event subscription, e g. to get event reports for User Data Usage Measures and User Data Usage Trends, it has to do it via the l-SMF, since the local PSA UPF is "invisible", either administratively or logically or physically.

[0059] The solution as proposed by CR 4786 for 3GPP 23.502, which simply adds "upfSubscriptionlnfo" in the VsmfUpdateData sent from the SMF to l-SMF in order to request the l-SMF to create a UPF event subscription in the local PSA UPF by invoking NupLEventExposure service, cannot work.

[0060] The following problems exist: 1 . The (anchor) SMF does not know whether the l-SMF supports invoking the Nupf_EventExposure service, and the (anchor) SMF has no idea of whether the inserted new local PSA UPF offers the Nupf_EventExposure service, and which events it supports to subscribe and report.

[0061] 2 The change described in CR 4786 just specified that the SMF should send the subscription to the l-SMF, and then the l-SMF subscribes to the UPF. The l-SMF does not return the result of creation of the event subscription in the local PSA UPF. Since the Nupf_EventExposure service also supports the Unsubscribe service operation and modification of a subscription, the SMF needs to be able to modify (in case subscription is changed), e.g. reporting frequency (see below), or unsubscribe the subscription in the old local PSA UPF, e.g. in the event when the l-SMF is changed, so that the local PSA UPF is changed as well.

[0062] The same problems are applicable for subscription of UPF event via a Visited SMF (V-SMF), e.g. a Home-Routed PDU Session, especially considering the support of Edge Computing where 3GPP has introduced the support of Home- Routed Session Breakout PDU session, i.e. it allows some of application traffic may be offloaded at V-UPF (PSA UPF), e.g. for a gaming application. Note that a “V-SMF” is an SMF in a Visited Public Land Mobile Network (VPLMN), as compared to a Home SMF (H-SMF) (or simply “SMF") in a Home Public Land Mobile Network (HPLMN). Likewise, a “V-UPF” is a UPF in a VPLMN, as compared to a “H-UPF" is a UPF in a HPLMN.

[0063] The following excerpts from 3GPP TS 29.564 V18.4.0 show examples of UPF events.

[0064] ***** START EXCERPTS FROM 3GPP TS 29.564 *****

[0065] 5.2.1.3.3 User Data Usage Measures

[0066] Table 5.2.1.3.3-1 : User Data Usage Measures event 1.3.4 User Data Usage Trends

[0067] Table 5.2.1 .3.4-1 : User Data Usage Trends event

[0068] ***** START NEXT EXCERPT *****

[0069] 6.1.6.2.11 Type: UpfEventSubscription

[0070] Table 6.1.6.2.11-1: Definition of type UpfEventSubscription

[0071] 6.1.6.2.12 Type: UpfEventMode Table 6.1.6.2.12-1 : Definition of type UpfEventMode 6.1.6.2.13 Type: Upf Event

[0072] Table 6.2.6.2.13-1 : Definition of type UpfEvent

[0073] ***** END EXCERPTS FROM 3GPP TS 29.564 *****

[0074] Certain aspects of the present disclosure and their embodiments may provide solutions to the aforementioned or other challenges. Embodiments of systems and methods are disclosed herein that provide a mechanism to enable an (H- )SMF to create an event subscription in a local PSA UPF (for a PDU session with an I -SMF) or in a PSA UPF in a Visiting PLMN (for a Home-Routed PDU Session), via the l-SMF or the V-SMF respectively.

[0075] A procedure in accordance with an example embodiment of the present disclosure includes the following steps. Here, an l-SMF is used as an example. For a Home-Routed PDU Session, the references to the l-SMF in the following description are replaced by references to the V-SMF.

[0076] 1 . When an l-SMF is inserted into a PDU session or changed, and when the l-SMF selects a UPF based on the Data Network Name (DNN) and / or Single Network Slice Assistance Information (S-NSSAI) to which the PDU session pertains if available, the l-SMF selects an l-UPF that supports one or more certain Packet Forwarding Control Protocol (PFCP) features, or supports the Nupf_event exposure service.

[0077] 2. The l-SMF sends, to the SMF, an Nsmf_PDUSession_Update with the HsmfUpdateData including information that indicates one or more supported PFCP features of the (selected) l-UPF, UPF event(s) exposed / supported by the l-UPF, and an apiRoot (for both Intra PLMN and inter PLMN) of the Nupf_EventExposure service Application Programming Interface (API) of the l-UPF; 3. Based on the information from l-SMF, and if there are one or more UPF Event Exposure service consumer, e.g. a NWDAF, requests to subscribe to such event, the SMF sends, to the l-SMF, an Nsmf_PDUSession_Update request message with VsmfUpdateData including UPF event subscription related information

[0078] 4 The l-SMF subscribes to the l-UPF on behalf of the SMF using the UPF event subscription.

[0079] 5 the l-SMF shall send the Nsmf_PDUSession_Update response with the VsmfUpdatedData including the newly created UPF Event Subscription resource, which includes the resource URI and the subscription status, and possible event report(s) (e.g. an intermediate report when the immediateFlag is set in the subscription request) to the SMF.

[0080] 6. NOTE that, l-SMF may send a Nsmf_PDUSession_Update request with the HsmfUpdateData including the newly created UPF Event Subscription resource to the SMF, e.g. when the UPF does not respond in time.

[0081] While not limited to or by any particular advantage, embodiments of the present disclosure may provide a number of advantages over existing technology. These advantages may include the following. Embodiments of the present disclosure enable an SMF to subscribe an event of an UPF / DNAI that the SMF does not control.

[0082] Now, the description will turn to a more detailed description of some example embodiments of the present disclosure.

[0083] Figure 3

[0084] Figure 3 illustrates a procedure for when an l-SMF is inserted and the SMF requests the l-SMF to invoke NupLEventExposure service to create event subscription in the l-UPF (which has a local PSA UPF function). The bold, italicized parameters are new.

[0085] Note that a similar procedure can be used when V-SMF is inserted e.g. when UE enters into another PLMN so that a non-roaming PDU session becomes a Home Routed PDU session, or during a PDU session creation procedure, where the V-SMF can also report the Supported PFCP Features of the V-UPF (PSA UPF in the Visiting PLMN) , UPF event(s) exposed / supported by the said V-UPF and the apiRoot (for both Intra PLMN and inter PLMN) of the NupLEventExposure service API of the said UPF. In this case these parameters may also be included in the PduSessionCreateData (for PDU session creation procedure) and in the HsmfUpdateData instead including the same in the psalnfo and ulcIBpinfo.

[0086] The apiRoot (for both Intra PLMN and inter PLMN) of the NupLEventExposure service API of the said UPF is used to enable the (H-)SMF to directly invoke the NupLEventExposure service offered by the said UPF.

[0087] The steps of the procedure of Figure 3 are as follows:

[0088] • Step 1 : The UPF event consumer (e.g., NWDAF) sends a NsmfEventExposureJSubscribe message to the SMF.

[0089] • Step 2 (Optional): If no l-SMF is available for the PDU session to which the subscribe message of Step 1 pertains, the SMF sends an NupfEventExposure_Subscribe message to the UPF.

[0090] • Step 3: When an l-SMF is inserted or an l-SMF is available when the SMF receives the Nsmf_EventExposure_Subscribe message, the l-SMF sends, to the SMF, an Nsmf_PDUSession_Update request including one or more Supported PFCP Features of the l-UPF (i.e., information that indicates one or more supported PFCP features), UPF event(s) exposed by the l-UPF (i.e., information that indicates UPF event(s) exposed by the l-UPF, and an apiRoot (for both Intra PLMN and inter PLMN) of the Nupf_EventExposure service API of the l-UPF which may be used. In the illustrated example, the aforementioned information is included in HsmfUpdateData.

[0091] • Step 4: The SMF may send an NsmfPDUSessionJJpdate Response to the l-SMF.

[0092] • Step 5: Based on the information received from the l-SMF in step 3, and if there are one or more UPF Event Exposure service consumer, e.g. a NWDAF, requests to subscribe to such event, the SMF sends the Nsmf_PDUSession_Update request including the UPF event subscription related information to I- SMF. NOTE that, step 1 may be performed before or after an insertion of l-SMF. The UPF event subscription related information is, in one embodiment, an Information Element (IE) that includes subscription information for the event to be exposed by the l-UPF controlled by the l-SMF. As described in clauses 4.15.4.5 2 and 5.2.8.2.3 of 3GPP TS 23.502, this information includes, in one example embodiment, the following information: o Notification Target Address (UPF event consumer address), Notification Correlation Information, o Indication of UPF Event Exposure Service and Target subscription UPF Event Id. o Event Filter Information: S-NSSAI, DNN, DNAI.UPF Id, Traffic Description for the target traffic (e.g. Application Id), Area of Interest, SSID / BSSID. o Target of Event Reporting: a UE. o Reporting suggestion information. o Target Subscription information: Type of Measurement and granularity of the information requested.

[0093] • Step 6: The l-SMF subscribes to the l-UPF on behalf of the SMF.

[0094] • Step 7 (Optional): The l-SMF may send the newly created UPF Event Subscription resource to the SMF in the Nsmf_PDUSession_Update response (as or as part of VsmfUpdateData).

[0095] • Steps 8 and 9 (Optional): The l-SMF may send the newly created UPF Event Subscription resource to the SMF in an Nsmf_PDUSession_Update request message (as or as part of HsmfUpdateData) The SMF may send a response to the l-SMF.

[0096] • Step 10: A notification for the subscription is sent from the l-UPF to the UPF event consumer (e.g , NWDAF)

[0097] One example embodiment of the HsmfUpdateData included in Step 3 and / or Step 8 is shown below as changes to clauses 6.1.6.2.11, 6.1.6.2.41 , and 6.1.6.2.49 of 3GPP TS 29.502 where additions are noted via underlined text:

[0098] 3GPP TS29.502

[0099] 6.1.6.2.11 Type: HsmfUpdateData

[0100] Table 6.1.6.2.11 -1 : Definition of type HsmfUpdateData

[0101] 6.1.6.2.41 Type: Psalnformation

[0102] Table 6.1.6.2.41-1 : Definition of type Psalnformation 6.1.6.2.49 Type: UlcIBpInformation

[0103] Table 6.1.6.2.49-1: Definition of type UlcIBpInformation

[0104] One example embodiment of the VsmfUpdateData included in Step 7 is shown below as changes to clause

[0105] 6.1.6.2.16 of 3GPP TS 29.502 where additions are noted via underlined text:

[0106] 6.1.6.2.16 Type: VsmfUpdatedData Table 6.1.6.2.16-1: Definition of type VsmfUpdatedData

[0107] Figure 4

[0108] Figure 4 is a schematic block diagram of a network node 400 according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The network node 400 may be, for example, a network node that implements the functionality of a core network node (e.g., NWDAF, SMF, l-SMF, or the like), or the like. As illustrated, the network node 400 includes one or more processors 404 (e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and / or the like), memory 406, and a network interface 408. The one or more processors 404 are also referred to herein as processing circuitry. The one or more processors 404 operate to provide one or more functions of the network node 400 as described herein (e.g., one or more functions of a core network node as described herein). In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory 406 and executed by the one or more processors 404. Figure 5

[0109] Figure 5 is a schematic block diagram that illustrates a virtualized embodiment of the network node 400 according to some embodiments of the present disclosure. Again, optional features are represented by dashed boxes. As used herein, a "virtualized” network node is an implementation of the network node 400 in which at least a portion of the functionality of the network node 400 is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, the network node 400 includes one or more processing nodes 500 coupled to or included as part of a network(s) 502. Each processing node 500 includes one or more processors 504 (e.g., CPUs, ASICs, FPGAs, and / or the like), memory 506, and a network interface 508. In this example, functions 510 of the network node 400 described herein (e.g , one or more functions a core network node, as described herein) are implemented at the one or more processing nodes 500 or distributed across the two or more processing nodes 500 in any desired manner. In some particular embodiments, some or all of the functions 510 of the network node 400 described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s) 500.

[0110] In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the network node 400 or a node (e.g., a processing node 500) implementing one or more of the functions 510 of the network node 400 in a virtual environment according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

[0111] Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and / or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according to one or more embodiments of the present disclosure.

[0112] While processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.). Embodiments

[0113] Some of the embodiments describe above may be summarized in the following manner:

[0114] 1. A method performed by a first Session Management Function, SMF, in a core network of a cellular communications system, the method comprising:

[0115] • receiving (Fig. 3, step 3) a first Protocol Data Unit, PDU, session update request from a second SMF, wherein the first PDU session update request comprises any one or more of the following: o information that indicates one or more supported PFCP features of a User Plane Function, UPF, selected by the second SMF; o information that indicates one or more UPF events exposed or supported by the UPF; o an apiRoot of an event exposure service Application Programming Interface, API, of the UPF;

[0116] • sending (Fig. 3, step 5) a second PDU session update request to the second SMF, the second PDU session update request comprising UPF event subscription related information.

[0117] 2. The method of embodiment 1, wherein the second SMF is an Intermediate SMF, l-SMF, inserted for an associated PDU session of a User Equipment, UE.

[0118] 3. The method of embodiment 2, wherein the UPF selected by the second SMF is an Intermediate UPF, l-UPF, selected by the l-SMF.

[0119] 4. The method of embodiment 1 , wherein the second SMF is a Visited SMF, V-SMF, in a Visited Public Land Mobile Network, V-PLMN, of a User Equipment, UE, associated to the PDU session.

[0120] 5. The method of embodiment 4, wherein the UPF selected by the second SMF is Visited UPF, V-UPF, selected by the V-SMF.

[0121] 6. The method of any of embodiments 1 to 5, wherein the apiRoot comprised in the first PDU session update request is an Intra-PLMN apiRoot, and the first PDU session update request further comprises an Inter-PLMN apiRoot.

[0122] 7. The method of any of embodiments 1 to 6, further comprising receiving (Fig. 3, step 7) a PDU session update response from the second SMF, the PDU session update response comprising information about successful creation of a UPF event subscription by the second SMF with the UPF selected by the second SMF.

[0123] 8. The method of any of embodiments 1 to 6, further comprising receiving (Fig. 3, step 8) a third PDU session update request from the second SMF, the third PDU session update request comprising information about successful creation of a UPF event subscription by the second SMF with the UPF selected by the second SMF.

[0124] 9. A network node adapted to perform the method of any of embodiments 1 to 8. 10. A method performed by a second Session Management Function, SMF, in a core network of a cellular communications system, the method comprising:

[0125] • sending (Fig. 3, step 3) a first Protocol Data Unit, PDU, session update request to a first SMF, wherein the first PDU session update request comprises any one or more of the following: o information that indicates one or more supported PFCP features of a User Plane Function, UPF, selected by the second SMF; o information that indicates one or more UPF events exposed or supported by the UPF; o an apiRoot of an event exposure service Application Programming Interface, API, of the UPF;

[0126] • receiving (Fig 3, step 5) a second PDU session update request from the first SMF, the second PDU session update request comprising UPF event subscription related information

[0127] 11. The method of embodiment 10, wherein the second SMF is an Intermediate SMF, l-SMF, inserted for an associated PDU session of a User Equipment, UE.

[0128] 12. The method of embodiment 11, wherein the UPF selected by the second SMF is an Intermediate UPF, l-UPF, selected by the l-SMF.

[0129] 13. The method of embodiment 10, wherein the second SMF is a Visited SMF, V-SMF, in a Visited Public Land Mobile Network, V-PLMN, of a User Equipment, UE, associated to the PDU session.

[0130] 14. The method of embodiment 13, wherein the UPF selected by the second SMF is Visited UPF, V-UPF, selected by the V-SMF.

[0131] 15. The method of any of embodiments 10 to 14, wherein the apiRoot comprised in the first PDU session update request is an Intra-PLMN apiRoot, and the first PDU session update request further comprises an Inter-PLMN apiRoot.

[0132] 16. The method of any of embodiments 10 to 15, further comprising sending (Fig. 3, step 7) a PDU session update response to the first SMF, the PDU session update response comprising information about successful creation of a UPF event subscription by the second SMF with the UPF selected by the second SMF.

[0133] 17. The method of any of embodiments 10 to 15, further comprising sending (Fig. 3, step 8) a third PDU session update request to the first SMF, the third PDU session update request comprising information about successful creation of a UPF event subscription by the second SMF with the UPF selected by the second SMF.

[0134] 18. A network node adapted to perform the method of any of embodiments 10 to 17

Claims

ClaimsWhat is claimed is:

1. A method performed by a first Session Management Function, SMF, in a core network of a cellular communications system, the method comprising:• receiving (Fig. 3, step 3) a first Protocol Data Unit, PDU, session update request from a second SMF, wherein the first PDU session update request comprises any one or more of the following: o information that indicates one or more supported PFCP features of a User Plane Function, UPF, selected by the second SMF; o information that indicates one or more UPF events exposed or supported by the UPF; o an apiRoot of an event exposure service Application Programming Interface, API, of the UPF;• sending (Fig. 3, step 5) a second PDU session update request to the second SMF, the second PDU session update request comprising UPF event subscription related information.

2. The method of claim 1 , wherein the second SMF is an Intermediate SMF, l-SMF, inserted for an associated PDU session of a User Equipment, UE.

3. The method of claim 2, wherein the UPF selected by the second SMF is an Intermediate UPF, l-UPF, selected by the l-SMF.

4. The method of claim 1 , wherein the second SMF is a Visited SMF, V-SMF, in a Visited Public Land Mobile Network, V-PLMN, of a User Equipment, UE, associated to the PDU session.

5. The method of claim 4, wherein the UPF selected by the second SMF is Visited UPF, V-UPF, selected by the V-SMF.

6. The method of any one of claim 1 to 5, wherein the apiRoot comprised in the first PDU session update request is an Intra-PLMN apiRoot, and the first PDU session update request further comprises an Inter-PLMN apiRoot.

7. The method of any one of claim 1 to 6, further comprising receiving (Fig. 3, step 7) a PDU session update response from the second SMF, the PDU session update response comprising information about successful creation of a UPF event subscription by the second SMF with the UPF selected by the second SMF.

8. The method of any one of claim 1 to 6, further comprising receiving (Fig. 3, step 8) a third PDU session update request from the second SMF, the third PDU session update request comprising information about successful creation of a UPF event subscription by the second SMF with the UPF selected by the second SMF.

9. A network node adapted to perform the method of any one of claim 1 to 8.

10. A method performed by a second Session Management Function, SMF, in a core network of a cellular communications system, the method comprising:• sending (Fig. 3, step 3) a first Protocol Data Unit, PDU, session update request to a first SMF, wherein the first PDU session update request comprises any one or more of the following: o information that indicates one or more supported PFCP features of a User Plane Function, UPF, selected by the second SMF; o information that indicates one or more UPF events exposed or supported by the UPF; o an apiRoot of an event exposure service Application Programming Interface, API, of the UPF;• receiving (Fig. 3, step 5) a second PDU session update request from the first SMF, the second PDU session update request comprising UPF event subscription related information.

11. The method of claim 10, wherein the second SMF is an Intermediate SMF, l-SMF, inserted for an associated PDU session of a User Equipment, UE.

12. The method of claim 11 , wherein the UPF selected by the second SMF is an Intermediate UPF, l-UPF, selected by the l-SMF.

13. The method of claim 10, wherein the second SMF is a Visited SMF, V-SMF, in a Visited Public Land Mobile Network, V-PLMN, of a User Equipment, UE, associated to the PDU session.

14. The method of claim 13, wherein the UPF selected by the second SMF is Visited UPF, V-UPF, selected by the V-SMF.

15. The method of any one of claim 10 to 14, wherein the apiRoot comprised in the first PDU session update request is an Intra-PLMN apiRoot, and the first PDU session update request further comprises an Inter-PLMN apiRoot.

16. The method of any one of claim 10 to 15, further comprising sending (Fig. 3, step 7) a PDU session update response to the first SMF, the PDU session update response comprising information about successful creation of a UPF event subscription by the second SMF with the UPF selected by the second SMF.

17. The method of any one of claim 10 to 15, further comprising sending (Fig. 3, step 8) a third PDU session update request to the first SMF, the third PDU session update request comprising information about successful creation of a UPF event subscription by the second SMF with the UPF selected by the second SMF.

18. A network node adapted to perform the method of any one of claim 10 to 17.

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