WO2021094025A1

WO2021094025A1 - Virtual network group with multiple session management functions

Info

Publication number: WO2021094025A1
Application number: PCT/EP2020/076654
Authority: WO
Inventors: Klaus Hoffmann
Original assignee: Nokia Technologies Oy
Priority date: 2019-11-14
Filing date: 2020-09-24
Publication date: 2021-05-20

Abstract

Various example embodiments relate to establishment and control of a virtual network group comprising a plurality of session management functions. Apparatuses, methods, and computer programs are disclosed.

Description

VIRTUAL NETWORK GROUP WITH MULTIPLE SESSION MANAGEMENT FUNCTIONS

TECHNICAL FIELD

[0001] Various example embodiments generally relate to the field of wireless communication networks. In particular, some example embodiments relate to establishment and control of virtual network groups.

BACKGROUND

[0002] Various wireless communication systems, such as for example systems based on 3GPP Fifth Generation (5G) standards, may apply virtualization of network functions to enable flexible and efficient use of the network. For example, the service based architecture (SBA) of 5G defines a set of interconnected network functions (NF), where each network function may provide and consume services through service based interfaces (SBI) to other network functions. Virtualization of the network functions enables to adapt the network to various situations .

SUMMARY

[0003] 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.

[0004] Example embodiments improve selection of user plane functions in a communication network. The benefits may be achieved by the features of the independent claims. Further implementation forms are provided in the dependent claims, the description, and the drawings.

[0005] According to an aspect, an apparatus comprises at least one processor and at least one memory including computer program code, the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to: receive a session establishment request at a first session management function; send a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; receive, from the network management function, a user plane function candidate list; select a first user plane function from the user plane function candidate list; receive a first user plane function connectivity request from at least one second session management function associated with the virtual network group; and initiate establishment of a user plane function connection between the first user plane function and a second user plane function associated with the at least one second session management function.

[0006] According to an aspect, a method comprises receiving a session establishment request at a first session management function; sending a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; receiving, from the network management function, a user plane function candidate list; selecting a first user plane function from the user plane function candidate list; receiving a first user plane function connectivity request from at least one second session management function associated with the virtual network group; and initiating establishment of a user plane function connection between the first user plane function and a second user plane function associated with the at least one second session management function. [0007] According to an aspect, a computer program is configured, when executed by an apparatus, to cause the apparatus at least to: receive a session establishment request at a first session management function; send a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; receive, from the network management function, a user plane function candidate list; select a first user plane function from the user plane function candidate list; receive a first user plane function connectivity request from at least one second session management function associated with the virtual network group; and initiate establishment of a user plane function connection between the first user plane function and a second user plane function associated with the at least one second session management function.

[0008] According to an aspect, an apparatus comprises means for receiving a session establishment request at a first session management function; means for sending a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; means for receiving, from the network management function, a user plane function candidate list; means for selecting a first user plane function from the user plane function candidate list; means for receiving a first user plane function connectivity request from at least one second session management function associated with the virtual network group; and means for initiating establishment of a user plane function connection between the first user plane function and a second user plane function associated with the at least one second session management function.

[0009] According to an aspect, an apparatus comprises at least one processor and at least one memory including computer program code, the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to: receive a session establishment request at a first session management function; send a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; receive, from the network management function, a user plane function candidate list; select a first user plane function from the user plane function candidate list; receive a first user plane function connectivity request from at least one second session management function associated with the virtual network group; and initiate establishment of a user plane function connection between the first user plane function and a second user plane function associated with the at least one second session management function.

[0010] According to an aspect, a method comprises receiving a session establishment request at a first session management function; sending a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; receiving, from the network management function, a user plane function candidate list; selecting a first user plane function from the user plane function candidate list; receiving a first user plane function connectivity request from at least one second session management function associated with the virtual network group; and initiating establishment of a user plane function connection between the first user plane function and a second user plane function associated with the at least one second session management function.

[0011] According to an aspect, a computer program is configured, when executed by an apparatus, to cause the apparatus at least to: receive a session establishment request at a first session management function; send a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; receive, from the network management function, a user plane function candidate list; select a first user plane function from the user plane function candidate list; receive a first user plane function connectivity request from at least one second session management function associated with the virtual network group; and initiate establishment of a user plane function connection between the first user plane function and a second user plane function associated with the at least one second session management function.

[0012] According to an aspect, an apparatus comprises means for receiving a session establishment request at a first session management function; means for sending a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; means for receiving, from the network management function, a user plane function candidate list; means for selecting a first user plane function from the user plane function candidate list; means for receiving a first user plane function connectivity request from at least one second session management function associated with the virtual network group; and means for initiating establishment of a user plane function connection between the first user plane function and a second user plane function associated with the at least one second session management function.

[0013] According to an aspect, an apparatus comprises at least one processor and at least one memory including computer program code, the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to: receive, from a first session management function, a first user plane function query comprising an identifier of a virtual network group; send a first user plane function candidate list to the first session management function; receive an indication of a first user plane function selected by the first session management function; associate the first session management function and/or the first user plane function with the virtual network group; receive, from a second session management function, a second user plane function query comprising the identifier of the virtual network group; and send a second user plane function candidate list and an indication of the first session management function associated with the virtual network identifier to the second session management function.

[0014] According to an aspect, a method comprises receiving, from a first session management function, a first user plane function query comprising an identifier of a virtual network group; sending a first user plane function candidate list to the first session management function; receiving an indication of a first user plane function selected by the first session management function; associating the first session management function and/or the first user plane function with the virtual network group; receiving, from a second session management function, a second user plane function query comprising the identifier of the virtual network group; and sending a second user plane function candidate list and an indication of the first session management function associated with the virtual network identifier to the second session management function.

[0015] According to an aspect, a computer program is configured, when executed by an apparatus, to cause the apparatus at least to: receive, from a first session management function, a first user plane function query comprising an identifier of a virtual network group; send a first user plane function candidate list to the first session management function; receive an indication of a first user plane function selected by the first session management function; associate the first session management function and/or the first user plane function with the virtual network group; receive, from a second session management function, a second user plane function query comprising the identifier of the virtual network group; and send a second user plane function candidate list and an indication of the first session management function associated with the virtual network identifier to the second session management function

[0016] According to an aspect, an apparatus comprises means for receiving, from a first session management function, a first user plane function query comprising an identifier of a virtual network group; means for sending a first user plane function candidate list to the first session management function; means for receiving an indication of a first user plane function selected by the first session management function; means for associating the first session management function and/or the first user plane function with the virtual network group; means for receiving, from a second session management function, a second user plane function query comprising the identifier of the virtual network group; and means for sending a second user plane function candidate list and an indication of the first session management function associated with the virtual network identifier to the second session management function.

[0017] According to an aspect, an apparatus comprises at least one processor and at least one memory including computer program code, the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to: receive a session establishment request, a handover event message, or a service request message at an access management function; send a session management function query to a network management function, wherein the session management function query comprises an identifier of a virtual network group; receive, from the network management function, a session management function candidate list; and select a first session management function from the session management function candidate list.

[0018] According to an aspect, a method comprises receiving a session establishment request, a handover event message, or a service request message at an access management function; sending a session management function query to a network management function, wherein the session management function query comprises an identifier of a virtual network group; receive, from the network management function, a session management function candidate list; and select a first session management function from the session management function candidate list.

[0019] According to an aspect, a computer program is configured, when executed by an apparatus, to cause the apparatus at least to: receive a session establishment request, a handover event message, or a service request message at an access management function; send a session management function query to a network management function, wherein the session management function query comprises an identifier of a virtual network group; receive, from the network management function, a session management function candidate list; and select a first session management function from the session management function candidate list.

[0020] According to an aspect, an apparatus comprises means for receiving a session establishment request, a handover event message, or a service request message at an access management function; means for sending a session management function query to a network management function, wherein the session management function query comprises an identifier of a virtual network group; means for receiving, from the network management function, a session management function candidate list; and means for selecting a first session management function from the session management function candidate list.

[0021] Many of the attendant features will be more readily appreciated as they become better understood by reference to the following detailed description considered in connection with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

[0022] The accompanying drawings, which are included to provide a further understanding of the example embodiments and constitute a part of this specification, illustrate example embodiments and together with the description help to understand the example embodiments. In the drawings:

[0023] FIG. 1 illustrates an example of a network comprising network functions and a client node, according to an example embodiment .

[0024] FIG. 2 illustrates an example of a local switch based user plane architecture, according to an example embodiment; [0025] FIG. 3 illustrates an example of an N19 interface based user plane architecture, according to an example embodiment;

[0026] FIG. 4 illustrates an example of a protocol stack at an interface between two PSA UPFs, according to an example embodiment;

[0027] FIG. 5 illustrates an example of a virtual network group establishment and control procedure, according to an example embodiment;

[0028] FIG. 6 illustrates an example of a virtual network group establishment and control procedure in a roaming scenario, according to an example embodiment.

[0029] FIG. 7 illustrates an example of an apparatus configured to perform one or more example embodiments; [0030] FIG. 8 illustrates an example of a method for enabling establishment of a virtual network group at a first session management function, according to an example embodiment .

[0031] FIG. 9 illustrates an example of a method for enabling establishment of a virtual network group at a second session management function, according to an example embodiment .

[0032] FIG. 10 illustrates an example of a method for establishing a virtual network group at a network management function, according to an example embodiment.

[0033] FIG. 11 illustrates an example of a method for enabling establishment of a virtual network group at an access management function, according to an example embodiment.

[0034] Like references are used to designate like parts in the accompanying drawings.

DETAILED DESCRIPTION

[0035] Reference will now be made in detail to example embodiments, examples of which are illustrated in the accompanying drawings. The detailed description provided below in connection with the appended drawings is intended as a description of the present examples and is not intended to represent the only forms in which the present example may be constructed or utilized. The description sets forth the functions of the example and the sequence of steps for constructing and operating the example. However, the same or equivalent functions and sequences may be accomplished by different examples.

[0036] According to an example embodiment, multiple session management functions (SMF) and user plane functions (UPF) associated with the SMFs may be registered to a virtual network (VN) group. SMFs participating in the VN group are informed about other SMFs in the VN group and consequently interfaces between UPFs associated with different SMFs may be established. [0037] FIG. 1 illustrates an example embodiment of a network 100. One or more client nodes, such as for example user equipment 110, may communicate with access network (AN) 120, which may comprise one or more base stations such as for example 5G base stations (gNB). Base stations may be also called radio access network (RAN) nodes. The UE 110 may communicate with the access network 120 over a radio interface such as for example provided in the 5G-NR (New Radio) standard. However, the access network 120 may be also implemented based on alternative radio access technologies (RAT). The access network 120 may therefore comprise any suitable access point(s) for connecting UE 110 to the network 100. The UE 110 may be therefore configured to access the network using various technologies such as for example Wi-Fi, 4G, 5G, or the like.

[0038] Access network 120 may communicate with one or more user plane functions (UPF), for example over an N3 interface. A UPF may be configured to handle user data part of a communication session. A UPF may provide an interconnect point between the access network 120 and a data network 150. For example, an UPF may be configured to handle encapsulation and decapsulation of user plane protocol(s), such as for example the GPRS (general packet radio service) tunneling protocol for the user plane (GTP-U). Functionality of a UPF may be divided between an intermediate UPF (I-UPF) 130 and a PSA UPF 132, which may act as a session anchor for a user plane communication session. For example, PSA UPF 132 may be configured to operate as a PDU (packet data unit) session anchor for a PDU session. The I-UPF 130 may communicate with the PSA UPF 132, for example over a user plane function interface, such as for example an N9 interface. PSA UPF 132 may be for example configured to provide a PDU session anchor point for intra- or inter-RAT mobility. The I-UPF 130 may provide an access point interface towards the access network 120, for example an N3 interface.

[0039] An access and mobility management function (AMF) 134 may be configured to receive connection and session request related information from UE 110 or RAN 120, for example over the N1 and N2 interfaces, respectively. AMF 134 may be responsible for connection and mobility management. However, AMF 134 may be configured to delegate any session management related tasks to a session management function (SMF) 136, for example based on information about suitable SMF(s) 136 retrieved from a network repository function (NRF) 140. NRF 140 may be configured to enable network functions to register their services and discover services offered by other network functions. Based on the information received from NRF 140, or locally configured at AMF 134, the AMF 134 may select an SMF instance and an SMF service for a particular UE 110. Selection of the SMF instance may be for example based on subscription information associated with the UE 110 retrieved from a unified data management (UDM) function 146, access technologies supported or being used by UE 110, or the like.

[0040] A session management function (SMF) 136 may be configured to handle management of one or more communication sessions, for example PDU sessions within one or more UPFs. SMF 136 may communicate with AMF 134, for example to receive requests that trigger establishment, updating, or removal of communication sessions. For example, SMF 136 may be configured to select and/or reselect an UPF for a particular communication session. The SMF 136 may for example determine to select a centrally located UPF or a distributed UPF located closer to the access network (AN) node associated with UE 110. Information about available UPFs may be locally stored at SMF 136 or SMF 136 may receive this information from one or more other network elements or functions, such as for example the UPFs themselves or via the NRF 140.An SMF 136 may be configured to select an UPF based on various information and/or parameters, which may for example include location of the UPF, for example I-UPF 130, location of the UE 110, current UPF load, UPF capacity, or whether the UPF already has been selected for that group or the like.

[0041] The network functions may further comprise a network slice selection function (NSSF), a network exposure function (NEF), a policy control function (PCF), application function (AF), and an authentication server function (AUSF). The network functions may communicate over a service based interface (SBI) bus, which may be accessible to the plurality of network functions. Point-to-point interfaces between individual network functions, such as for example an N8 interface between AMF 134 and UDM 146, an N10 interface between SMF 136 and UDM 146, and an Nil interface between AMF 134 and SMF 136, may be implemented over the SBI message bus. For sake of simplicity, only few examples of point-to-point interfaces are illustrated in FIG. 1.

[0042] Even though some example embodiments have been described using the 5G network as an example, it is appreciated that example embodiments presented herein are not limited to this example network and may be applied in any present or future communication networks, for example other type of cellular networks, short-range wireless networks, broadcast networks, or the like. For example, functionality of a session management function, network management function, a user plane function, and/or an access management function may be also implemented within other network functions. [0043] FIG. 2 illustrates an example of a local switch based user plane architecture, which may be used in a non-roaming scenario. A first UE 110 may communicate with a second UE 112 through access networks, I-UPFs, and a single PSA UPF acting as a local switch. This architecture may be used for example to support 5G LAN type service.

[0044] FIG. 3 illustrates an example of an N19 interface based user plane architecture, where a first UE 110 and a second UE 112 may communicate through access networks, I-UPFs, and two PSA UPFs connected via the N19 interface. Also this architecture may be used to support 5G LAN type service. The PSA UPFs may be however associated with a single session management function.

[0045] FIG. 4 illustrates an example of a protocol stack between a first PSA UPF 132 and a second PSA UPF 133. Although the N19 interface is used as an example, it is appreciated that the example embodiments presented herein are applicable to any type of interface between UPFs that provide functionality of, or similar to, PDU session anchor UPFs. UE 110 may communicate with the first PSA UPF 132 using for example the PDU session protocol stack. The first PSA UPF 132 may be configured to decapsulate packet data unit at each layer of the PDU session protocol stack and encapsulate the data received from UE 110 in the first PDU session for transmission to the second PSA UPF 133.

[0046] The protocol stack at the interface between the first PSA UPF 132 and the second PSA UPF 133 may for example comprise a PDU layer, a GTP-U layer, UDP/IP (User Datagram Protocol/Internet Protocol) layer, Layer 2, and Layer 1. The GTP-U protocol may be used for example for tunneling user data between the first PSA UPF 132 and the second PSA UPF 133, and/or other network functions. Each tunnel established at the GTP-U protocol layer may be distinguished from other GTP-U tunnels based on at least one tunnel identifier assigned to a tunnel. The second PSA UPF 133 may be configured to decapsulate the UPF interface (N19) protocols used at the first PSA UPF 132 and deliver the data to the second UE 112 in a second PDU session. Data may be communicated from the second UE 112 to the first UE 110 in a similar fashion to create a bidirectional connection between applications at both devices. Even though example embodiments have been described using GTP-U as an example, it is appreciated that any other protocol providing a tunneling functionality may be used. Also the other layers of the N19 interface are provided as examples for implementing an UPF interface and it is understood that different implementations may be applied. For example, an N6 interface could be used instead of N19.

[0047] FIG. 5 illustrates an example of a virtual network group establishment and control procedure. The procedure of FIG. 5 may be applied for example in a non-roaming scenario. [0048] At 501, a first SMF 136 may receive a session establishment request. The session establishment request may be for example received from a first UE (not shown in FIG. 5). The session establishment request may be delivered to the first SMF 136 for example via the access network 120 and AMF 134. [0049] At 502, the first SMF 136 may send a UPF query (UPF

Q) to a network management function, represented in this example by network repository function (NRF) 140. However, similar network management functionality could be provided for example by the unified data management function (UDM) 146, or another network function. The user plane function query may comprise an identifier of a virtual network group. The virtual network group identified in the UPF query may refer to a virtual network group to which the first SMF 136 wishes to join, or to a new virtual network group to be established. [0050] The NRF 140 may receive the UPF query from the first SMF 136. In response to receiving the UPF query, the NRF 140 may determine an UPF candidate list to be provided to the first SMF 136. The UPF candidate list may include one or a plurality of candidate UPFs for the first SMF 136. The NRF 140 may determine the candidate UPFs based on various criteria, such as delay requirements or capabilities of the UPFs. For example, NRF 140 may determine to select candidate UPFs that are located close enough to the first UE such that delay requirement(s) are fulfilled, for example to enable mobile edge computing. When determining the UPF candidate list, the NRF 140 may prioritize UPFs on which at least one communication session for that particular VN group has been already established. A PDU session is an example of a communication session. For example, UPFs may be listed in a priority order, where UPFs with active PDU sessions may be located at the beginning of the list. The priority order may be indicated also by any other means. According to an example embodiment, the NRF 140 may be configured to determine the priority order of UPFs. An SMF may be configured to store the UPF candidate list and/or a separate indication of the priority order received from NRF 140, for example as a local copy in its cache memory. The candidate list and/or the indication of priority order may be stored for a predetermined time period or a time period indicated by NRF 140.

[0051] At 503, the NRF 140 may send the UPF candidate list to the first SMF 136, for example in an UPF query response (UPF QR). The first SMF 136 may receive the UPF candidate list from the NRF 140.

[0052] At 504, the first SMF 136 may select a first UPF 132 from the candidate list, for example in response to receiving the UPF query response. The first UPF 132 may comprise a session anchor UPF such as for example a PDU session anchor (PSA) UPF.

[0053] The first SMF 136 may be further configured to send an indication of the selected first UPF 132 to the NRF 140, for example to request registration of the selected first UPF 132 with the VN group. The indication of the selected first UPF 132 may comprise an identifier of the first UPF 132 (UPF ID 1) and optionally an identifier of the VN group to which the selected first UPF 132 is to be registered.

[0054] The NRF 140 may receive the indication of the first UPF 132 selected by the first SMF 136. The NRF 140 may associate also the first SMF 136 and/or the first UPF 132 with the VN group, for example in response to receiving the indication of the selected first UPF 132 from the first SMF 136.

[0055] At 505, the first SMF 136 may communicate with the first UPF 132, for example to initiate establishment of one or more communication sessions at the first UPF 132. The communication may be performed over the N4 interface, for example based on at least a packet forwarding control protocol (PFCP). The first SMF 136 may for example instruct the first UPF 132 to establish a communication session with the first UE. The first SMF 136 may further use the SMF/UPF interface to request UPF 132 to release one or more communication sessions ongoing at the first UPF 132.

[0056] At 506, the first SMF 136 may send a virtual network (VN) group registration request to NRF 140. Although in the example of FIG. 5 the VN group registration request is sent after the UPF communication step 505, it is understood that the VN group registration request may be sent any time during the procedure, for example before sending the UPF query at 502, or even before receiving the PDU session establishment request at 501. Registering an SMF to the VN group before receiving the session establishment request enables to speed up the procedure. The VN group registration request may comprise an identifier of the first SMF 136. The VN group registration request may comprise an identifier of the VN group. The first SMF 136 may send the VN group registration request for example in response to determining that it wishes to participate in the identified VN group. In the example of 5G, the virtual network group identifier may comprise a 5G VN group ID. The first SMF 136 may further send another VN group registration request comprising an indication of the first UPF 133 selected by the first SMF 136. Alternatively, the identifier of the first SMF 136 and the indication of the first UPF 132 may be included in a single VN group registration request message.

[0057] NRF 140 may receive the VN group registration request (s) from the first SMF 136. The NRF 140 may associate the first SMF 136 and/or the first UPF 132 with the VN group, for example in response to receiving the VN group registration request (s).

[0058] Associating an SMF or a UPF with a VN group may comprise assigning the SMF or UPF to the VN group. When the SMF or UPF is associated with the VN group, the NRF 140 may for example inform other SMFs of the VN group about the associated SMF or UPF. The associated SMF or UPF therefore belong to the set of SMFs or UPFs providing user plane communication services within the VN group.

[0059] At 507, the first SMF 136 may send a virtual network (VN) group notification subscription request to the NRF 140. Although in the example of FIG. 5 the VN group notification subscription request is sent after the UPF communication step 505, it is understood that the VN group notification subscription request may be sent any time during the procedure, for example after sending the VN group registration request regardless of when the VN group registration request is sent. [0060] In response to receiving the VN group notification subscription request, the NRF 140 may determine to send notifications associated with the VN group to the first SMF 136. Alternatively, NRF 140 may determine to send notifications associated with the VN group based on at least the registration of an SMF to the VN group. Therefore, separate VN group notification subscription message may not be needed in some example embodiments.

[0061] Information associated with the UPF query (502), the UPF query response (503), the VN group registration request (506), or the VN group subscription request (507) may be included in one or more control messages. According to an example embodiment, a UPF query message may include the identifier of the VN group. The UPF query request message, or another control message, may further comprise the VN group registration request and/or the VN group subscription request. The UPF query response (504) may be included in one or more control messages.

[0062] At 508, a second SMF 137 may receive a session establishment request. The session establishment request may be for example received from a second UE (not shown in FIG. 5). The session establishment request may be delivered to the second SMF 137 for example via the access network 120 and AMF 134, or another access network and/or another AMF.

[0063] At 509, the second SMF 137 may send an UPF query (UPF Q) to the NRF 140. The UPF query may comprise an identifier of the VN group. Thereby the second SMF 137 may indicate its interest to join the identified VN group. Prior to the UPF query, the second SMF 137 may have received an indication of the VN group from the NRF 140. Alternatively, the second SMF 137 may send an UPF query without an identifier of a VN group. The UPF query may however include a request to join an available VN group or indicate capability of the second SMF 137 to join a VN group.

[0064] The NRF 140 may receive the UPF query from the second SMF 137. In response to receiving the UPF query, the NRF 140 may prepare a UPF candidate list to be provided to the second SMF 137. The UPF candidate list may include one or a plurality of candidate UPFs for the second SMF 137. Similar to operation 504, the NRF 140 may determine the candidate UPFs based on various criteria such as delay requirements, capabilities of the UPFs, and/or their association with the VN group. The UPF candidate list may for example comprise a plurality of UPFs associated with the VN group. The first UPF 132 associated with the first SMF 136 may or may not be included in the candidate list prepared for the second SMF 137. For example, if the first SMF 136 and second SMF 137 belong to different SMF sets, which are responsible for different sets of UPFs, the first UPF 132 may not be included in the candidate list. However, if the first SMF and the second SMF 137 belong to the same SMF set, being responsible for the same set of UPFs, then the first UPF 132 may be part of the candidate UPF list provided to SMF 137.

[0065] The NRF 140 may further determine whether there are other SMFs associated with the VN group to which the second SMF 137 is to join. For example, in response to determining that the first SMF 136 and/or other SMFs are associated with the VN group, the NRF may send an indication of one or a plurality of SMFs associated with the VN group, for example an indication of the first SMF 136, to the second SMF 137.

[0066] At 510, the NRF 140 may send the UPF candidate list to the first SMF 136, for example in an UPF query response (UPF QR). In addition to the UPF candidate list, the NRF 140 may send an indication of the first SMF 136 being associated with the VN group. The indication of the first SMF 136 may be included in the UPF query response message, or be sent as a separate message. The second SMF 137 may receive the UPF candidate list and the indication of the SMF(s) associated with the VN group from the NRF 140.

[0067] At 511, the second SMF 137 may select a second UPF 133 from the candidate list, for example in response to receiving the UPF query response. The second UPF 133 may comprise a session anchor UPF such as for example a PDU session anchor (PSA) UPF.

[0068] The second SMF 137 may be further configured to send an indication of the selected second UPF 133 to the NRF 140, for example to request registration of the selected second UPF 133 with the VN group. The indication of the selected second UPF 133 may comprise an identifier of the second UPF 133 (UPF ID 2) and optionally an identifier of the VN group to which the selected second UPF 133 is to be registered. The NRF 140 may receive the indication of the second UPF 133 selected by the second SMF 137. The NRF 140 may associate the second SMF 137 and/or the second UPF 133 with the VN group, for example in response to receiving the indication of the selected second UPF 133 from the second SMF 137.

[0069] At 512, the second SMF 137 may communicate with the selected second UPF 133, for example to initiate establishment of one or more communication sessions at the second UPF 133. The communication may be performed over the N4 interface, for example based on at least the PFCP protocol. The second SMF 137 may for example instruct the second UPF 133 to establish a communication session with the second UE. The second SMF 137 may further use the SMF/UPF interface to request UPF 133 to release one or more communication sessions ongoing at the second UPF 133. [0070] At 513, the second SMF 137 may send a virtual network (VN) group registration request to NRF 140. Although in the example of FIG. 5 the VN group registration request is sent after the UPF communication step 512, it is understood that the VN group registration request may be sent any time during the procedure. The VN group registration request may comprise an identifier of the second SMF 137. The VN group registration request may comprise an identifier of the VN group. The second SMF 137 may send the VN group registration request for example in response to determining that it wishes to participate in the identified VN group.

[0071] The NRF 140 may receive the VN group registration message from the second SMF 137. The NRF 140 may associate the second SMF 137 with the VN group, for example in response to receiving the VN group registration request. The NRF 140 may further send a notification comprising an indication of the second SMF 137 being associated with the VN group to the first SMF 137.

[0072] At 514, the second SMF 137 may send a virtual network (VN) group notification subscription request. Although in the example of FIG. 5 the VN group notification subscription request is sent after the UPF communication step 505, it is understood that the VN group registration request may be sent any time during the procedure, for example after sending the VN group registration request, regardless of when the VN group registration is sent.

[0073] Information associated with the UPF query (509), the UPF query response (510), the VN group registration request (513), or the VN group notification subscription request (514) may be included in one or more control messages, as described in relation to the first SMF 136. [0074] At 515, the second SMF 137 may send a first SMF request to the first SMF 136. The first SMF request may comprise, or be sent as, a first UPF connectivity request. The UPF connectivity request may comprise a UPF tunneling request. In general, an SMF request may be used for instructing or requesting another SMF to establish, or initiate establishment of, a communication session or connection between UPFs associated with the different SMFs or a local switch within one UPF connected to a SMF. The communication session may comprise a tunneled communication session or a tunneled connection .

[0075] According to an example embodiment, one and the same SMF may have been allocated by the AMF for two UEs and the SMF may have selected the same UPF for that VN group. In that case there may not be an external tunnel, connectivity, or connection visible outside the UPF. The UPF in question may detect the local switch based on at least comparing the FTEIDs (Fully Qualified GTP Tunnel ID). If the two FTEIDs, which may comprise IP addresses of both FTEIDs, belong to the same UPF, then local switching may be performed instead of external tunnel/connectivity. Hence, the user plane function interface may comprise an internal interface at a local switch UPF. FTEID and TEID are examples of a tunnel identifier and other type of identifier (s) may be used instead.

[0076] A UPF interface may be established between the UPFs. The tunneled connection may be for example implemented according to the GTP-U tunneling protocol. The first SMF request may comprise at least one of: the VN group identifier, an identifier of the second UPF 133, or a second tunnel identifier associated with the second UPF 133 at the UPF interface. The identifier of the second UPF 133 may comprise an FTEID of the second UPF 133. Thereby the second SMF 137 may inform the first SMF 136 about the tunnel identifier towards the first SMF 136. The UPF interface may comprise an N19 interface. The first SMF 136 may receive the first SMF request from the second SMF 137.

[0077] At 516, the first SMF may communicate with the selected first UPF 132. For example, the first SMF 136 may initiate the establishment of the UPF connection, for example an UPF tunnel, between the first UPF 132 and the second UPF 133 associated with the second SMF 137. Initiating the establishment of the UPF connection may be based on at least the second tunnel identifier and/or at least the identifier of the second UPF 133 included in the received first SMF request. For instance, the FTEID of the second UPF 133 included in the first SMF request may be forwarded to the first UPF 132. This enables the first UPF 132 to send uplink (UL) packets from the first UPF 132 to the FTEID of the second UPF 133. The first UPF 132 may send its FTEID, for example in the N4 response from the first UPF 132 to the first SMF 136. The first SMF 136 can send this FTEID for example in a response to the first SMF request or in a second SMF request to the second SMF 133. The second SMF 137 may forward the FTEID to the second UPF 133. The second UPF 133 may then forward the UL traffic of the second UE towards the first UPF 132. Initiating the establishment of the UPF connection may be in response to determining that the VN group identified in the received SMF request corresponds with identifier (s) of associated VN group (s) at the first SMF 136, for example VN groups for which the first SMF 136 has registered.

[0078] At 517, the first SMF 136 may send a second SMF request to the second SMF 137, for example in response to receiving the first SMF request from the second SMF 137 and/or determining that the VN group identified in the received SMF request corresponds with identifier (s) of associated VN group (s) at the first SMF 136. The second SMF request may comprise, or be sent as, a second UPF connectivity request. The UPF connectivity request may comprise a UPF tunneling request. The second SMF request may comprise, or be sent as, a response to the first SMF request, for example a UPF connectivity request response message. The second SMF request may comprise at least one of: the VN group identifier, an identifier of the first UPF 132, or a first tunnel identifier associated with the first UPF 132 at the UPF interface. The identifier of the first UPF 132 may comprise an FTEID of the first UPF 132. Thereby the first SMF 136 may inform the second SMF 137 about the tunnel identifier towards the second SMF 137.

[0079] At 518, the second SMF 137 may communicate with the second UPF 133, for example to initiate establishment of an UPF connection, for example an UPF tunnel, between the second UPF 133 and the first UPF 132. Initiating the establishment of the UPF connection may be based on at least the first tunnel identifier and/or at least the identifier of the first UPF 132 included in the second SMF request. Initiating the establishment of the UPF tunnel may be further based on the second tunnel identifier included in the first SMF request sent at 515. For instance, the FTEID of the first UPF 132 may be included in a response to the first SMF request or in the second SMF request. The FTEID of the first UPF 132 may be then forwarded to the second UPF 133. This enables the second UPF 133 to send uplink (UL) packets from the second UPF 133 to the FTEID of the first UPF 132. Initiating the establishment of the UPF connection may be in response to determining that the VN group identified in the second SMF request corresponds with identifier (s) of associated VN group (s) at the second SMF 137, for example VN groups for which the second SMF 137 has registered, or the VN group identified in the first SMF request. [0080] At 519, the first UPF 132 and second UPF 133 may establish the connection (s), for example tunnel(s), between the first UPF 132 and second UPF 133. The SMF request(s) sent at 515 and/or 517 enable establishment of an UPF interface, for example N19, between UPFs associated with different session management functions. Since the network management function, for example NRF 140, is informed about the network functions already selected for the VN group, the NRF 140 may inform the SMFs about participating SMFs and UPFs accordingly. The UPF selection process at SMF is thereby enabled to calculate quality of service (QoS) requirements and to reuse UPFs already selected by other SMFs for corresponding VN group. The network management function is for example enabled to calculate a delay between participating UPFs and to optimize locations of selected UPFs. The same mechanism may be applied also for internal switching of two PDU sessions residing on the same UPF.

[0081] In order to keep the network management function, for example NRF 140, updated with active UPFs, an SMF, for example the first SMF 136 or the second SMF 137, may be configured to report establishment and release of communication sessions at associated UPFs to the NRF 140. For example, if an SMF releases the last PDU session of an UPF associated with a VN group, the SMF may deregister the corresponding UPF from the VN group. The SMF may for example remove the association of the UPF and the VN group in its memory. The SMF may further send an UPF deregistration request to NRF 140. The UPF deregistration request may comprise the identifier of the UPF. The UPF deregistration request may further comprise an identifier of the VN group.

[0082] For example, the first SMF 136 may cause a release of a communication session at the first UPF 132 and send, to NRF 140, a request to deregister the first UPF 132 from the VN group. Sending the deregistration request may be in response to determining that no communication sessions exist at the first UPF 132 after the release of the communication session. Similarly, the second SMF 137 may cause a release of a communication session at the second UPF 133 and send, to the NRF 140, a request to deregister the second UPF 133 from the VN group. Sending the deregistration request may be in response to determining that no packet data unit sessions exist at the second UPF 133 after the release of the communication session. [0083] In response to receiving a UPF deregistration request, the NRF 140 may remove the association of the identified UPF(s) from the VN group. This enables to keep the list of network functions associated the VN group updated. As a consequence, a new SMF establishing a new PDU session may not be informed about the deregistered UPFs anymore.

[0084] An SMF may be further configured to send an SMF deregistration request, for example if no communication sessions exist at any UPF associated with the VN group and the SMF after the release of the last communication session at a UPF. For example, the first SMF 136 may cause a release of a communication session at the first UPF 132 and send, to NRF 140, a request to deregister the first SMF 136 from the VN group. Sending the SMF deregistration request may be in response to determining that no communication sessions exist at the first UPF 132, or any other UPF associated with the first SMF 136 and the VN group, after the release of the communication session. Similarly, the second SMF 137 may cause a release of a communication session at the second UPF 133 and send, to the NRF 140, a request to deregister the second SMF 137 from the VN group. Sending the deregistration request may be in response to determining that no communication sessions exist at the second UPF 133, or any other UPF associated with the second SMF 137 and the VN group, after the release of the communication session.

[0085] In response to receiving an SMF deregistration request, the NRF 140 may remove the association of the SMF from the VN group (s). This enables to keep the list of network functions associated the VN group updated. Therefore a new SMF establishing a new PDU session may not be informed about the deregistered SMFs anymore. For example, the NRF 140 may remove the association of the first SMF 136 or the first UPF 132 with the VN group, in response to receiving a request to deregister the first SMF 136 or first UPF 132 from the virtual network group, and/or remove the association of the second SMF 137 or the second UPF 133 with the VN group, in response to receiving a request to deregister the second SMF 137 or the second UPF 133 from the VN group.

[0086] According to an example embodiment, an access management function, such as for example the AMF 134 may be configured to consult the NRF 140, or another network management function, with the VN group identifier to be able to select an SMF which has been already selected for that VN group. The access management function may for example comprise an AMF according to 3GPP 5G specifications, but it is understood that the access management function may in general comprise any network function, network node, or network device responsible of managing access of UEs to the network. For example, an access management function may or may not comprise a mobility management function.

[0087] According to an example embodiment, the access management function may cooperate with NRF 140 to select one or more SMFs. The access management function may receive a session establishment request , a handover event message, and/or a service request message from UE 110, for example via the access network 120. The access management function may send an SMF query to NRF 140, for example in response to the received message, for example the session establishment request, from UE 110. The SMF query may comprise an identifier of a virtual network group. The SMF query may comprise an identifier of the access management function. The SMF query may comprise an identifier of the UE 110. The NRF 140 may receive the SMF query from the access management function. The SMF query may be sent for example as one or more control messages.

[0088] In response to receiving the SMF query, the NRF 140 may determine an SMF candidate list to be provided to the access management function. The SMF candidate list may include one or a plurality of candidate SMFs for the access management function. The NRF 140 may determine the candidate SMFs based on at least one criterion, such as for example the identity of the UE 110, the location of the UE 110, required QoS, and/or the VN group indicated in the SMF query. When determining the SMF candidate list, the NRF 140 may prioritize SMFs that are associated with UPFs on which at least one communication session, for example a PDU session, for the indicated VN group has been already established.

[0089] The NRF 140 may send the SMF candidate list to the access management function, for example in an SMF query response. The access management function may receive the SMF candidate list from the NRF 140. The access management function may select an SMF from the SMF candidate list. The access management function may be further configured to send an indication of the selected SMF to the NRF 140, for example to request registration of the selected SMF with the VN group. The indication of the selected SMF may comprise an identifier of the selected SMF and optionally an identifier of the VN group to which the selected SMF is to be registered. The NRF 140 may receive the indication of the SMF selected by the access management function. The NRF 140 may associate the SMF and/or any UPFs already associated with the SMF with the VN group, for example in response to receiving the indication of the selected SMF from the access management function.

[0090] FIG. 6 illustrates an example of a virtual network group establishment procedure in a roaming scenario. Similar to operations 501, 502, 506, and 507, the first SMF 136 may receive a PDU session establishment request from a first UE (not shown in FIG. 6), and send a UPF query, VN group registration, and/or VN group subscription. A visitor network management function, represented in this example by visitor NRF 142 (V-NRF) may receive the UPF query, the VN group registration, and/or the VN group notification subscription. The V-NRF 142 may be configured to share its database with the home network management function, for example home-NRF 144 (H- NRF). Similarly, the H-NRF 144 may be configured to share its database with V-NRF 142. For example, in response to receiving the UPF query and/or the VN group registration request from the first SMF 136, the V-NRF 142 may determine whether there are UPFs and/or other SMFs associated with the VN group either at V-NRF 142 or H-NRF 144. V-NRF may provide a candidate UPF list accordingly, for example in a UPF query response. Upon selection of the first UPF 132 from the candidate list, the first SMF 136 may inform the V-NRF 142 about selection of the first 132 UPF. V-NRF 142 may forward the indication of the selected first UPF 132 to H-NRF 144. V-NRF 142 may further associate the first UPF 132 with the VN group. According to an example embodiment, V-NRF 142 may send an indication of the association of the first SMF 136 and/or the first UPF 132 with the VN group to the H-NRF 144.

[0091] Similar to operations 508, 509, 511, and 512, the second SMF 137 may receive a PDU session establishment from a second UE (not shown in FIG. 6), and send an UPF query, VN group registration, and/or VN group subscription. In response to receiving the UPF query and/or the VN group registration request from the second SMF 137, the V-NRF 142 may determine that the first SMF 136 is already associated with the VN group indicated in the UPF query, or, in a separate VN group registration message. The V-NRF 142 may then send an indication of the first SMF 136 to the second SMF 137, for example in a UPF query response. The UPF query response may further comprise a UPF candidate list for the second SMF 137. Upon selection of the second UPF 133 from the candidate list, the second SMF 137 may inform the V-NRF 142 about selection of the second UPF 133. V-NRF 142 may forward the indication of the selected second UPF 133 to H-NRF 144. V-NRF 142 may further associate the second UPF 133 with the VN group. According to an example embodiment, V-NRF 142 may send an indication of the association of the second UPF 133 with the VN group to the H-NRF 144. Therefore, the H-NRF 144 is kept informed about the SMFs and/or UPFs participating in the VN group, even if the UE(s) request the PDU session in a roaming scenario.

[0092] Similar to operations 515 to 519, the first SMF 136 and the second SMF 137 may exchange tunnel identifier information and initiate establishment of the tunnel(s) at the UPF interface between the first UPF 132 and the second UPF 133. Therefore, the disclosed solution may be also applied across PLMN (public land mobile network) boundaries. For example, the first UE and the second UE may be part of different PLMNs.

[0093] Even though some example embodiments have been used using SMF, AMF or NRF as example, it is understood that similar operations may be implemented at different network functions, network nodes, or network entities, for example at the control plane of a serving gateway (SGW-C), a control plane of a packet data network (PDN) gateway (PGW-C), gNB CU-CP (gNB-Control Unit-Control Plane) or at the user plane plane of a serving gateway (SGW-U), a user plane of a packet data network (PDN) gateway (PGW-U), gNB CU-UP (gNB-CU-User Plane, for example based 3GPP TS 38.401), a mobility management entity (MME) or a domain name server (DNS).

[0094] FIG. 7 illustrates an example embodiment of an apparatus 700. Apparatus 700 may be for example configured to implement one or more network functions such as for example a session management function or a network management function. Apparatus 700 may comprise at least one processor 702. The at least one processor may comprise, for example, one or more of various processing devices, such as for example a co-processor, a microprocessor, a controller, a digital signal processor (DSP), a processing circuitry with or without an accompanying DSP, or various other processing devices including integrated circuits such as, for example, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), a microcontroller unit (MCU), a hardware accelerator, a special-purpose computer chip, or the like.

[0095] The apparatus may further comprise at least one memory 704. The memory may be configured to store, for example, computer program code or the like, for example operating system software and application software. The memory may comprise one or more volatile memory devices, one or more non-volatile memory devices, and/or a combination thereof. For example, the memory may be embodied as magnetic storage devices (such as hard disk drives, floppy disks, magnetic tapes, etc.), optical magnetic storage devices, or semiconductor memories (such as mask ROM, PROM (programmable ROM), EPROM (erasable PROM), flash ROM, RAM (random access memory), etc.).

[0096] Apparatus 700 may further comprise a communication interface 708 configured to enable the apparatus to transmit and/or receive information, for example control data packets or user data packets to/ from other devices or network functions. In one example, apparatus 700 may use communication interface 708 to transmit or receive information over the SBI message bus, or any other network function interface, for example in accordance with the 3GPP 5G standard.

[0097] When the apparatus is configured to implement some functionality, some component and/or components of the apparatus, such as for example the at least one processor and/or the memory, may be configured to implement this functionality. Furthermore, when the at least one processor is configured to implement some functionality, this functionality may be implemented using program code 706 comprised, for example, in the memory 704.

[0098] The functionality described herein may be performed, at least in part, by one or more computer program product components such as software components. According to an embodiment, the apparatus comprises a processor or processor circuitry, such as for example a microcontroller, configured by the program code when executed to execute the embodiments of the operations and functionality described. Alternatively, or in addition, the functionality described herein can be performed, at least in part, by one or more hardware logic components. For example, and without limitation, illustrative types of hardware logic components that can be used include Field-programmable Gate Arrays (FPGAs), application-specific Integrated Circuits (ASICs), application-specific Standard Products (ASSPs), System-on-a-chip systems (SOCs), Complex Programmable Logic Devices (CPLDs), Graphics Processing Units (GPUs).

[0099] Apparatus 700 may comprise a computing device such as for example a network server, a network gateway, or the like. Although apparatus 700 is illustrated as a single device it is appreciated that, wherever applicable, functions of apparatus 700 may be distributed to a plurality of devices, for example to implement example embodiments as a cloud computing service.

[00100] Various example embodiments disclose methods, computer programs and apparatuses for establishing a virtual network group comprising a plurality of session management functions to enable optimization of network function selection for example with respect to delay requirements.

[00101] FIG. 8 illustrates an example of a method 800 for enabling establishment of a virtual network group at a network function, for example the first SMF 136, according to an example embodiment.

[00102] At 801, the method may comprise receiving a session establishment request at a first session management function. [00103] At 802, the method may comprise sending a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group.

[00104] At 803, the method may comprise receiving, from the network management function, a user plane function candidate list.

[00105] At 804, the method may comprise selecting a first user plane function from the user plane function candidate list.

[00106] At 805, the method may comprise receiving a first user plane function connectivity request from at least one second session management function associated with the virtual network group.

[00107] At 806, the method may comprise initiating establishment of a user plane function connection between the first user plane function and a second user plane function associated with the at least one second session management function.

[00108] FIG. 9 illustrates an example of a method 900 for enabling establishment of a virtual network group at a network function, for example the second SMF 137, according to an example embodiment.

[00109] At 901, the method may comprise receiving a session establishment request at a second session management function. [001 10] At 902, the method may comprise sending a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group.

[001 1 1] At 903, the method may comprise receiving, from the network management function, a user plane function candidate list and an indication of at least one first session management function associated with the virtual network group.

[001 12] At 904, the method may comprise selecting a second user plane function from the user plane function candidate list.

[001 13] At 905, the method may comprise sending at least one first user plane function connectivity request to the at least one first session management function associated with the virtual network group.

[001 14] At 906, the method may comprise initiating establishment of a user plane function connection between the second user plane function and a first user plane function associated with the at least one first session management function.

[001 15] FIG. 10 illustrates an example of a method 800 for establishing a virtual network group at a network function, for example a network management function such as NRF 140 or V-NRF 142, according to an example embodiment. [001 16] At 1001, the method may comprise receiving, at a network management function, a first user plane function query comprising an identifier of a virtual network group from a first session management function.

[001 17] At 1002, the method may comprise sending a first user plane function candidate list to the first session management function.

[001 18] At 1003, the method may comprise receiving an indication of a first user plane function selected by the first session management function.

[001 19] At 1004, the method may comprise associating the first session management function and/or the first user plane function with the virtual network group.

[00120] At 1005, the method may comprise receiving, from a second session management function, a second user plane function query comprising the identifier of the virtual network group.

[00121] At 1006, the method may comprise sending a second user plane function candidate list and an indication of the first session management function associated with the virtual network identifier to the second session management function. [00122] FIG. 11 illustrates an example of a method 1100 for enabling establishment of a virtual network group at a network function, for example an access management function such as AMF 134, according to an example embodiment.

[00123] At 1101, the method may comprise receiving a session establishment request, a handover event message, or a service request message at an access management function.

[00124] At 1102, the method may comprise sending a session management function query to a network management function, wherein the session management function query comprises an identifier of a virtual network group. [00125] At 1103, the method may comprise receiving, from the network management function, a session management function candidate list.

[00126] At 1104, the method may comprise selecting a first session management function from the session management function candidate list.

[00127] Further features of the methods directly result from functionalities of the access and/or mobility management (MME, AMF), the session management functions, network management function, and/or user plane function like UPF and PGW-U, as described throughout the specification and in the appended claims, and are therefore not repeated here. Different variations of the methods may be also applied, as described in connection with the various example embodiments.

[00128] An apparatus, such as for example a network device configured to implement one or more network functions, may be configured to perform or cause performance of any aspect of the method (s) described herein. Further, a computer program may comprise instructions for causing, when executed, an apparatus to perform any aspect of the method (s) described herein. Further, an apparatus may comprise means for performing any aspect of the method (s) described herein. According to an example embodiment, the means comprises at least one processor, and memory including program code, the at least one processor, and program code configured to, when executed by the at least one processor, cause performance of any aspect of the method (s).

[00129] Any range or device value given herein may be extended or altered without losing the effect sought. Also, any embodiment may be combined with another embodiment unless explicitly disallowed. [00130] Although the subject matter has been described in language specific to structural features and/or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as examples of implementing the claims and other equivalent features and acts are intended to be within the scope of the claims.

[00131] It will be understood that the benefits and advantages described above may relate to one embodiment or may relate to several embodiments. The embodiments are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to 'an' item may refer to one or more of those items.

[00132] The steps or operations of the methods described herein may be carried out in any suitable order, or simultaneously where appropriate. Additionally, individual blocks may be deleted from any of the methods without departing from the scope of the subject matter described herein. Aspects of any of the example embodiments described above may be combined with aspects of any of the other example embodiments described to form further example embodiments without losing the effect sought.

[00133] The term 'comprising' is used herein to mean including the method, blocks, or elements identified, but that such blocks or elements do not comprise an exclusive list and a method or apparatus may contain additional blocks or elements.

[00134] Although subjects may be referred to as 'first' or 'second' subjects, this does not necessarily indicate any order or importance of the subjects. Instead, such attributes may be used solely for the purpose of making a difference between subjects.

[00135] As used in this application, the term 'circuitry' may refer to one or more or all of the following: (a) hardware- only circuit implementations (such as implementations in only analog and/or digital circuitry) and (b) combinations of hardware circuits and software, such as (as applicable):(i) a combination of analog and/or digital hardware circuit(s) with software/firmware and (ii) any portions of hardware processor (s) with software (including digital signal processor (s)), software, and memory(ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and (c) hardware circuit(s) and or processor (s), such as a microprocessor(s) or a portion of a microprocessor (s), that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation. This definition of circuitry applies to all uses of this term in this application, including in any claims.

[00136] As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

[00137] It will be understood that the above description is given by way of example only and that various modifications may be made by those skilled in the art. The above specification, examples and data provide a complete description of the structure and use of exemplary embodiments. Although various embodiments have been described above with a certain degree of particularity, or with reference to one or more individual embodiments, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from scope of this specification.

Claims

1.An apparatus, comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to: receive a session establishment request at a first session management function; send a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; receive, from the network management function, a user plane function candidate list; select a first user plane function from the user plane function candidate list; receive a first user plane function connectivity request from at least one second session management function associated with the virtual network group; and initiate establishment of a user plane function tunnel between the first user plane function and a second user plane function associated with the at least one second session management function.

2. The apparatus according to claim 1, wherein the apparatus is further caused to: send a virtual network group registration request comprising an identifier of the first session management function to the network management function; and/or send a virtual network group notification subscription request to the network management function.

3. The apparatus according to any preceding claim, wherein the apparatus is further caused to: send an indication of the selected first user plane function to the network management function.

4. The apparatus according to any preceding claim, wherein the first user plane function connectivity request comprises at least one of: the virtual network group identifier; an identifier of the second user plane function; or a second tunnel identifier associated with the second user plane function at a user plane function interface.

5. The apparatus according to claim 4, wherein the apparatus is further caused to: send at least one second user plane function connectivity request to the at least one second session management function, wherein the second user plane function connectivity request comprises at least one of: the virtual network group identifier; an identifier of the first user plane function; a first tunnel identifier associated with the first user plane function at the user plane function interface.

6. The apparatus according to claim 5, wherein the apparatus is further caused to: initiate establishment of the user plane function tunnel between the first user plane function and the second user plane function over the user plane function interface based on the first tunnel identifier and/or the second tunnel identifier.

7. The apparatus according to claim 6, wherein user plane function interface comprises an N19 interface or an N6 interface.

8. The apparatus according to any of claims 4 to 7, wherein the first user plane function comprises a first session anchor user plane function, and wherein the second user plane function comprises a second session anchor user plane function.

9. The apparatus according to any preceding claim, wherein the apparatus is further caused to: cause a release of a communication session at the first user plane function; send, to the network management function, a request to deregister the first user plane function from the virtual network group, in response to determining that no packet data unit sessions exist at the first user plane function after the release of the communication session.

10. The apparatus according to any preceding claim, wherein the network management function comprises a network repository function, a visitor network repository function, or a unified data management function.

11.An apparatus, comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to: receive a session establishment request at a second session management function; send a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; receive, from the network management function, a user plane function candidate list and an indication of at least one first session management function associated with the virtual network group; select a second user plane function from the user plane function candidate list; send at least one first user plane function connectivity request to the at least one first session management function associated with the virtual network group; and initiate establishment of a user plane function connection between the second user plane function and a first user plane function associated with the at least one first session management function.

12. The apparatus according to claim 11, wherein the apparatus is further caused to: send a virtual network group registration request comprising an identifier of the second session management function to the network management function; and/or send a virtual network group notification subscription request to the network management function.

13. The apparatus according to claim 11 or claim 12, wherein the apparatus is further caused to: send an indication of the selected second user plane function to the network management function.

14. The apparatus according to any of claims 11 to 13, wherein the first user plane function connectivity request comprises at least one of: the virtual network group identifier; an identifier of the second user plane function; a second tunnel identifier associated with the second user plane function at a user plane function interface.

15. The apparatus according to claim 14, wherein the apparatus is further caused to: receive a second user plane function connectivity request from the at least one first session management function, wherein the second user plane function connectivity request comprises at least one of: the virtual network group identifier; an identifier of the first user plane function; or a first tunnel identifier associated with the first user plane function at the user plane function interface.

16. The apparatus according to claim 15, wherein the apparatus is further caused to: initiate establishment of at least one connection between the first user plane function and the second user plane function over the user plane function interface based on the first tunnel identifier and/or the second tunnel identifier.

17. The apparatus according to claim 16, wherein user plane function interface comprises an N19 interface, an N6 interface, or an internal interface at a local switch user plane function.

18. The apparatus according to any of claims 15 to 17, wherein the first user plane function comprises a first session anchor user plane function, and wherein the second user plane function comprises a second session anchor user plane function.

19. The apparatus according to any of claims 11 to 18, wherein the apparatus is further caused to: cause a release of a communication session at the second user plane function; send, to the network management function, a request to deregister the second user plane function and/or the second session management function from the virtual network group, in response to determining that no packet data unit sessions exist at the second user plane function after the release of the communication session.

20. The apparatus according to any of claims 11 to 19, wherein the network management function comprises a network repository function, a visitor network repository function, or a unified data management function.

21.An apparatus, comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to: receive, at a network management function, a first user plane function query comprising an identifier of a virtual network group from a first session management function; send a first user plane function candidate list to the first session management function; receive an indication of a first user plane function selected by the first session management function; associate the first session management function and/or the first user plane function with the virtual network group; receive, from a second session management function, a second user plane function query comprising the identifier of the virtual network group; and send a second user plane function candidate list and an indication of the first session management function associated with the virtual network identifier to the second session management function.

22. The apparatus according to claim 21, wherein the apparatus is further caused to: receive, from the first session management function, a first virtual network group registration request comprising an identifier of the first session management function; and associate the first session management function with the virtual network group, in response to receiving the first virtual network group registration request.

23. The apparatus according to claim 21 or claim 22, wherein the apparatus is further caused to: receive, from the first session management function, a second virtual network group registration request comprising the indication of the first user plane function selected by the first session management function; and associate the first user plane function with the virtual network group, in response to receiving the second virtual network group registration request.

24. The apparatus according to any of claims 21 to 23, wherein the apparatus is further caused to: receive, from the first session management function, a virtual network group notification subscription request; receive, from the second session management function, a third virtual network group registration request comprising an identifier of the second session management function; and in response to receiving the third virtual network group registration request: associate the second session management function user plane function with the virtual network group; and send a notification comprising an indication of the second session management function being associated with the virtual network group to the first session management function.

25. The apparatus according claim 24, wherein the second user plane function candidate list comprises a plurality of user plane functions associated with the virtual network group.

26. The apparatus according to any of claims 21 to 25, wherein the apparatus is further caused to remove the association of the first session management function or the first user plane function with the virtual network group, in response to receiving a request to deregister the first session management function or user plane function from the virtual network group; and/or remove the association of the second session management function or the second user plane function with the virtual network group, in response to receiving a request to deregister the second session management function or the second user plane function from the virtual network group.

27. The apparatus according to any of claims 21 to 26, wherein the network management function comprises a network repository function or a unified data management function.

28. The apparatus according to any of claims 21 to 27, wherein the network management function comprises a visitor network repository function and wherein the apparatus is further caused to: send an indication of the first session management function and/or the first user plane function associated with the virtual network group to a home network repository function.

29. The apparatus according to any of claims 21 to 28, wherein the apparatus is further caused to: receive a session management function query from an access management function; send a session management function candidate list to the access management function; receive an indication of the first session management function selected by the access management function; and associate the first session management function with the virtual network group.

30.An apparatus, comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer code configured to, with the at least one processor, cause the apparatus at least to: receive a session establishment request, a handover event message, or a service request message at an access management function; send a session management function query to a network management function, wherein the session management function query comprises an identifier of a virtual network group; receive, from the network management function, a session management function candidate list; and select a first session management function from the session management function candidate list.

31. The apparatus according to claim 30, wherein the session establishment request is received from a user equipment, and wherein the session management function query comprises an identifier of the user equipment.

32.A method, comprising: receiving a session establishment request at a first session management function; sending a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; receiving, from the network management function, a user plane function candidate list; selecting a first user plane function from the user plane function candidate list; receiving a first user plane function connectivity request from at least one second session management function associated with the virtual network group; and initiating establishment of a user plane function connection between the first user plane function and a second user plane function associated with the at least one second session management function.

33.A method comprising: receiving a session establishment request at a second session management function; sending a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; receiving, from the network management function, a user plane function candidate list and an indication of at least one first session management function associated with the virtual network group; selecting a second user plane function from the user plane function candidate list; sending at least one first user plane function connectivity request to the at least one first session management function associated with the virtual network group; and initiating establishment of a user plane function connection between the second user plane function and a first user plane function associated with the at least one first session management function.

34.A method comprising: receiving, at a network management function, a first user plane function query comprising an identifier of a virtual network group from a first session management function; sending a first user plane function candidate list to the first session management function; receiving an indication of a first user plane function selected by the first session management function; associating the first session management function and/or the first user plane function with the virtual network group; receiving, from a second session management function, a second user plane function query comprising the identifier of the virtual network group; and sending a second user plane function candidate list and an indication of the first session management function associated with the virtual network identifier to the second session management function.

35.A method comprising: receiving a session establishment request, a handover event message, or a service request message at an access management function; sending a session management function query to a network management function, wherein the session management function query comprises an identifier of a virtual network group; receiving, from the network management function, a session management function candidate list; and selecting a first session management function from the session management function candidate list.

36.A computer program comprising program code configured to cause an apparatus at least to: receive a session establishment request at a first session management function; send a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; receive, from the network management function, a user plane function candidate list; select a first user plane function from the user plane function candidate list; receive a first user plane function connectivity request from at least one second session management function associated with the virtual network group; and initiate establishment of a user plane function connection between the first user plane function and a second user plane function associated with the at least one second session management function.

37.A computer program comprising program code configured to cause an apparatus at least to: receive a session establishment request at a second session management function; send a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; receive, from the network management function, a user plane function candidate list and an indication of at least one first session management function associated with the virtual network group; select a second user plane function from the user plane function candidate list; send at least one first user plane function connectivity request to the at least one first session management function associated with the virtual network group; and initiate establishment of a user plane function connection between the second user plane function and a first user plane function associated with the at least one first session management function.

38.A computer program comprising program code configured to cause an apparatus at least to: receive, at a network management function, a first user plane function query comprising an identifier of a virtual network group from a first session management function,; send a first user plane function candidate list to the first session management function; receive an indication of a first user plane function selected by the first session management function; associate the first session management function and/or the first user plane function with the virtual network group; receive, from a second session management function, a second user plane function query comprising the identifier of the virtual network group; and send a second user plane function candidate list and an indication of the first session management function associated with the virtual network identifier to the second session management function.

39.A computer program comprising program code configured to cause an apparatus to: receive a session establishment request, a handover event message, or a service request message at an access management function; send a session management function query to a network management function, wherein the session management function query comprises an identifier of a virtual network group; receive, from the network management function, a session management function candidate list; and select a first session management function from the session management function candidate list.

40.An apparatus, comprising: means for receiving a session establishment request at a first session management function; means for sending a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; means for receiving, from the network management function, a user plane function candidate list; means for selecting a first user plane function from the user plane function candidate list; means for receiving a first user plane function connectivity request from at least one second session management function associated with the virtual network group; and means for initiating establishment of a user plane function connection between the first user plane function and a second user plane function associated with the at least one second session management function.

41.An apparatus, comprising: means for receiving a session establishment request at a second session management function; means for sending a user plane function query to a network management function, wherein the user plane function query comprises an identifier of a virtual network group; means for receiving, from the network management function, a user plane function candidate list and an indication of at least one first session management function associated with the virtual network group; means for selecting a second user plane function from the user plane function candidate list; means for sending at least one first user plane function connectivity request to the at least one first session management function associated with the virtual network group; and means for initiating establishment of a user plane function connection between the second user plane function and a first user plane function associated with the at least one first session management function.

42.An apparatus, comprising: means for receiving, at a network management function, a first user plane function query comprising an identifier of a virtual network group from a first session management function; means for sending a first user plane function candidate list to the first session management function; means for receiving an indication of a first user plane function selected by the first session management function; means for associating the first session management function and/or the first user plane function with the virtual network group; means for receiving, from a second session management function, a second user plane function query comprising the identifier of the virtual network group; and means for sending a second user plane function candidate list and an indication of the first session management function associated with the virtual network identifier to the second session management function.

43.An apparatus, comprising: means for receiving a session establishment request, a handover event message, or a service request message at an access management function; means for sending a session management function query to a network management function, wherein the session management function query comprises an identifier of a virtual network group; means for receiving, from the network management function, a session management function candidate list; and means for selecting a first session management function from the session management function candidate list.