WO2023147856A1

WO2023147856A1 - Apparatus, methods and computer programs

Info

Publication number: WO2023147856A1
Application number: PCT/EP2022/052502
Authority: WO
Inventors: Klaus Hoffmann; Bruno Landais; Laurent Thiebaut; Shubhranshu Singh
Original assignee: Nokia Technologies Oy
Priority date: 2022-02-02
Filing date: 2022-02-02
Publication date: 2023-08-10
Also published as: CN118592058A

Abstract

There is provided an apparatus comprising means for performing: receiving information of an interface between a first network and a second network that is different from the first network, wherein the apparatus is located in the second network and the first network is providing an user plane function interfacing with a data network serving a user equipment that has roamed in to the second network; and selecting a user plane function in the second network, using the information of the interface.

Description

Apparatus, methods and computer programs

Field

This disclosure relates to communications, and more particularly to apparatus, methods and computer programs in a wireless communication system. More particularly the present invention relates to interfacing between networks.

Background

A communication system can be seen as a facility that enables communication between two or more devices such as user terminals, machine-like terminals, base stations and/or other nodes by providing communication channels for carrying information between the communicating devices. A communication system can be provided for example by means of a communication network and one or more compatible communication devices. The communication may comprise, for example, communication of data for carrying data for voice, electronic mail (email), text message, multimedia and/or content data communications and so on. Non-limiting examples of services provided include two-way or multi-way calls, data communication or multimedia services and access to a data network system, such as the Internet.

In a wireless system at least a part of communications occurs over wireless interfaces. A user can access a communication system by means of an appropriate communication device or terminal capable of communicating with a base station. Hence nodes like base stations are often referred to as access points. A communication device of a user is often referred to as user equipment (UE).

A communication system and associated devices typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. Communication protocols and/or parameters which shall be used for the connection are also typically defined.

Since introduction of fourth generation (4G) services increasing interest has been paid to the next, or fifth generation (5G) standard. 5G may also be referred to as New Radio (NR). Edge computing, or mobile edge computing (MEC) aims to provide resources, such as processing and storage, close to an end user

Statement of invention

According to a first aspect there is provided an apparatus comprising means for performing: receiving information of an interface between a first network and a second network that is different from the first network, wherein the apparatus is located in the second network and the first network is providing a user plane function interfacing with a data network serving a user equipment that has roamed in to the second network; and selecting a user plane function in the second network, using the information of the interface.

According to some examples, the user plane function in the first network is considered a first user plane function, and the user plane function in the second network is considered a second user plane function.

According to some examples, the information of an interface between a first network and a second network comprises one or more of: an internet protocol address of the user plane function in the first network; a fully qualified domain name of the user plane function in the first network; a token obscuring an internet protocol address of the user plane function in the first network.

According to some examples, the user plane function in the first network provides edge computing services to the user equipment.

According to some examples, the selecting a user plane function in the second network comprises sending a query to a network function repository function.

According to some examples, the query comprises one or more of: location information of the user plane function in the first network; internet protocol address or fully qualified domain name of the user plane function in the first network; token information of the user plane function in the first network.

According to some examples, the means are further configured to perform receiving, from the network function repository function, a plurality of candidate user plane functions in the second network, and the selecting a user plane function in the second network comprises selecting a user plane function from the plurality of said candidate user plane functions.

According to some examples, the selecting a user plane function in the second network comprises selecting a user plane function in the second network having a lowest user plane path delay with the user plane function in the first network.

According to some examples, the selecting a user plane function in the second network comprises selecting a user plane function having a lowest user plane path delay with an intermediate user plane function in the first network.

According to some examples, the first network comprises a home network of the user equipment and the second network comprises a visited network of the user equipment.

According to some examples, the means are further configured to perform indicating that the apparatus supports receiving information of an interface between the first network and the second network.

According to some examples, the apparatus receives said information of an interface between a first network and a second network in a packet data unit session context response or in a packet data unit session update response.

According to some examples, the apparatus comprises a session management function located in the second network.

According to some examples, the means comprises at least one processor; and at least one memory including computer program code, the at least one memory and computer program code configured to, with the at least one processor, cause the performance of the apparatus.

According to a second aspect there is provided an apparatus comprising at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: receiving information of an interface between a first network and a second network that is different from the first network, wherein the apparatus is located in the second network and the first network is providing an user plane function interfacing with a data network serving a user equipment that has roamed in to the second network; and selecting a user plane function in the second network, using the information of the interface.

According to a third aspect there is provided an apparatus comprising: receiving circuitry for receiving information of an interface between a first network and a second network that is different from the first network, wherein the apparatus is located in the second network and the first network is providing an user plane function interfacing with a data network serving a user equipment that has roamed in to the second network; and selecting circuitry for selecting a user plane function in the second network, using the information of the interface.

According to a fourth aspect there is provided a method performed by an apparatus comprising: receiving information of an interface between a first network and a second network that is different from the first network, wherein the apparatus is located in the second network and the first network is providing an user plane function interfacing with a data network serving a user equipment that has roamed in to the second network; and selecting a user plane function in the second network, using the information of the interface.

According to some examples, the method comprises receiving, from the network function repository function, a plurality of candidate user plane functions in the second network, and the selecting a user plane function in the second network comprises selecting a user plane function from the plurality of said candidate user plane functions.

According to a fifth aspect there is provided a computer program comprising instructions for causing an apparatus to perform at least the following: receiving information of an interface between a first network and a second network that is different from the first network, wherein the apparatus is located in the second network and the first network is providing an user plane function interfacing with a data network serving a user equipment that has roamed in to the second network; and selecting a user plane function in the second network, using the information of the interface.

According to a sixth aspect there is provided a computer program comprising instructions stored thereon for performing at least the following: receiving information of an interface between a first network and a second network that is different from the first network, wherein an apparatus is located in the second network and the first network is providing an user plane function interfacing with a data network serving a user equipment that has roamed in to the second network; and selecting a user plane function in the second network, using the information of the interface.

According to a seventh aspect there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the following: receiving information of an interface between a first network and a second network that is different from the first network, wherein the apparatus is located in the second network and the first network is providing an user plane function interfacing with a data network serving a user equipment that has roamed in to the second network; and selecting a user plane function in the second network, using the information of the interface.

According to an eighth aspect there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: receiving information of an interface between a first network and a second network that is different from the first network, wherein an apparatus is located in the second network and the first network is providing an user plane function interfacing with a data network serving a user equipment that has roamed in to the second network; and selecting a user plane function in the second network, using the information of the interface.

According to a ninth aspect there is provided an apparatus comprising means for performing: in response to receiving a message from a session management function, determining whether the session management function is located in a second network that is different from a first network, the apparatus being located in the first network; and when it is determined that the session management function is located in said second network, sending to the session management function information of an user plane interface between a user plane function in the first network and a user plane function in the second network.

According to some examples, the said user plane function in the first network provides edge computing services to a user equipment.

According to some examples, the information of an user plane interface between the first network and the second network comprises one or more of: an internet protocol address of the user plane function in the first network; a fully qualified domain name of the user plane function in the first network; a token obscuring an internet protocol address of the user plane function in the first network.

According to some examples, the message from the session management function is received in a packet data unit session context request message or a packet data unit session update request message.

According to some examples, the information of the interface is provided to the session management function in a packet data unit session context response message or packet data unit session update response message.

According to some examples, the information of the interface is provided to the session management function prior to a packet data unit session context response message or packet data unit session update response message.

According to some examples, the apparatus comprises a session management function located in the first network.

According to a tenth aspect there is provided an apparatus comprising at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: in response to receiving a message from a session management function, determining whether the session management function is located in a second network that is different from a first network, the apparatus being located in the first network; and when it is determined that the session management function is located in said second network, sending to the session management function information of an user plane interface between a user plane function in the first network and a user plane function in the second network.

According to an eleventh aspect there is provided an apparatus comprising: determining circuitry for, in response to receiving a message from a session management function, determining whether the session management function is located in a second network that is different from a first network, the apparatus being located in the first network; and sending circuitry for, when it is determined that the session management function is located in said second network, sending to the session management function information of an user plane interface between a user plane function in the first network and a user plane function in the second network.

According to a twelfth aspect there is provided a method performed by an apparatus comprising: in response to receiving a message from a session management function, determining whether the session management function is located in a second network that is different from a first network, the apparatus being located in the first network; and when it is determined that the session management function is located in said second network, sending to the session management function information of an user plane interface between a user plane function in the first network and a user plane function in the second network.

According to some examples, the information of an user plane interface between the first network and the second network comprises one or more of: an internet protocol address of the user plane function in the first network; a fully qualified domain name of the user plane function in the first network; a token obscuring an internet protocol address of the user plane function in the first network. According to some examples, the message from the session management function is received in a packet data unit session context request message or a packet data unit session update request message.

According to a thirteenth aspect there is provided a computer program comprising instructions for causing an apparatus to perform at least the following: in response to receiving a message from a session management function, determining whether the session management function is located in a second network that is different from a first network, the apparatus being located in the first network; and when it is determined that the session management function is located in said second network, sending to the session management function information of an user plane interface between a user plane function in the first network and a user plane function in the second network.

According to a fourteenth aspect there is provided a computer program comprising instructions stored thereon for performing at least the following: in response to receiving a message from a session management function, determining whether the session management function is located in a second network that is different from a first network, an apparatus being located in the first network; and when it is determined that the session management function is located in said second network, sending to the session management function information of an user plane interface between a user plane function in the first network and a user plane function in the second network.

According to a fifteenth aspect there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the following: in response to receiving a message from a session management function, determining whether the session management function is located in a second network that is different from a first network, the apparatus being located in the first network; and when it is determined that the session management function is located in said second network, sending to the session management function information of an user plane interface between a user plane function in the first network and a user plane function in the second network.

According to a sixteenth aspect there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: in response to receiving a message from a session management function, determining whether the session management function is located in a second network that is different from a first network, an apparatus being located in the first network; and when it is determined that the session management function is located in said second network, sending to the session management function information of an user plane interface between a user plane function in the first network and a user plane function in the second network.

According to a seventeenth aspect there is provided an apparatus comprising means for performing: receiving a query for discovering a user plane function in a second network, the apparatus located in the second network and the query comprising one or more of: information of a location of a user equipment; information of an interface between a first network and the second network; and using the information in the query to determine a candidate user plane function of the second network for interfacing with a user plane function in the first network.

According to some examples, said information of an interface between a first network and the second network comprises one or more of: an internet protocol address of the user plane function in the first network; a fully qualified domain name of the user plane function in the first network; a token obscuring an internet protocol address of the user plane function in the first network. According to some examples, the means further configured to perform sending the query to a network function repository function located in the first network; and receiving, from the network function repository function located in the first network, information of a routable interface address or name for interfacing between the first network and the second network.

According to some examples, the information of an interface between a first network and a second network received from the network function repository function located in the first network comprises one or more of: an internet protocol address of the user plane function in the first network; a fully qualified domain name of the user plane function in the first network.

According to some examples, the apparatus comprises a network function repository function located in the second network.

According to an eighteenth aspect there is provided an apparatus comprising at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: receiving a query for discovering a user plane function in a second network, the apparatus located in the second network and the query comprising one or more of: information of a location of a user equipment; information of an interface between a first network and the second network; and using the information in the query to determine a candidate user plane function of the second network for interfacing with a user plane function in the first network.

According to a nineteenth aspect there is provided an apparatus comprising: receiving circuitry for receiving a query for discovering a user plane function in a second network, the apparatus located in the second network and the query comprising one or more of: information of a location of a user equipment; information of an interface between a first network and the second network; and determining circuitry for using the information in the query to determine a candidate user plane function of the second network for interfacing with a user plane function in the first network.

According to a twentieth aspect there is provided a method comprising: receiving a query for discovering a user plane function in a second network, the apparatus located in the second network and the query comprising one or more of: information of a location of a user equipment; information of an interface between a first network and the second network; and using the information in the query to determine a candidate user plane function of the second network for interfacing with a user plane function in the first network.

According to some examples, said information of an interface between a first network and the second network comprises one or more of: an internet protocol address of the user plane function in the first network; a fully qualified domain name of the user plane function in the first network; a token obscuring an internet protocol address of the user plane function in the first network.

According to some examples, the method comprises sending the query to a network function repository function located in the first network; and receiving, from the network function repository function located in the first network, information of a routable interface address or name for interfacing between the first network and the second network.

According to some examples, the first network comprises a home network of the user equipment and the second network comprises a visited network of the user equipment. According to some examples, the apparatus comprises a network function repository function located in the second network.

According to a twenty first aspect there is provided a computer program comprising instructions for causing an apparatus to perform at least the following: receiving a query for discovering a user plane function in a second network, the apparatus located in the second network and the query comprising one or more of: information of a location of a user equipment; information of an interface between a first network and the second network; and using the information in the query to determine a candidate user plane function of the second network for interfacing with a user plane function in the first network.

According to a twenty second aspect there is provided a computer program comprising instructions stored thereon for performing at least the following: receiving a query for discovering a user plane function in a second network, an apparatus located in the second network and the query comprising one or more of: information of a location of a user equipment; information of an interface between a first network and the second network; and using the information in the query to determine a candidate user plane function of the second network for interfacing with a user plane function in the first network.

According to a twenty third aspect there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the following: receiving a query for discovering a user plane function in a second network, the apparatus located in the second network and the query comprising one or more of: information of a location of a user equipment; information of an interface between a first network and the second network; and using the information in the query to determine a candidate user plane function of the second network for interfacing with a user plane function in the first network.

According to a twenty fourth aspect there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: receiving a query for discovering a user plane function in a second network, an apparatus located in the second network and the query comprising one or more of: information of a location of a user equipment; information of an interface between a first network and the second network; and using the information in the query to determine a candidate user plane function of the second network for interfacing with a user plane function in the first network.

According to a twenty fifth aspect there is provided an apparatus comprising means for performing: receiving a request, from a network function repository function in a second network, the request including one or more of: information of a location of a user equipment; information of an interface between a first network and the second network, the apparatus being located in the first network; providing, to the network function repository function in the second network, information of a routable interface address of a user plane function in the first network, the information of a routable user plane address to be used for user plane data transfer with a user plane function in the second network.

According to some examples, the apparatus comprises a network function repository function located in the first network.

According to a twenty sixth aspect there is provided an apparatus comprising at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform: receiving a request, from a network function repository function in a second network, the request including one or more of: information of a location of a user equipment; information of an interface between a first network and the second network, the apparatus being located in the first network; providing, to the network function repository function in the second network, information of a routable interface address of a user plane function in the first network, the information of a routable user plane address to be used for user plane data transfer with a user plane function in the second network.

According to a twenty seventh aspect there is provided an apparatus comprising: receiving circuitry for receiving a request, from a network function repository function in a second network, the request including one or more of: information of a location of a user equipment; information of an interface between a first network and the second network, the apparatus being located in the first network; providing circuitry for providing, to the network function repository function in the second network, information of a routable interface address of a user plane function in the first network, the information of a routable user plane address to be used for user plane data transfer with a user plane function in the second network.

According to a twenty eighth aspect there is provided a method comprising: receiving a request, from a network function repository function in a second network, the request including one or more of: information of a location of a user equipment; information of an interface between a first network and the second network, the apparatus being located in the first network; providing, to the network function repository function in the second network, information of a routable interface address of a user plane function in the first network, the information of a routable user plane address to be used for user plane data transfer with a user plane function in the second network.

According to a twenty ninth aspect there is provided: a computer program comprising instructions for causing an apparatus to perform at least the following: receiving a request, from a network function repository function in a second network, the request including one or more of: information of a location of a user equipment; information of an interface between a first network and the second network, the apparatus being located in the first network; providing, to the network function repository function in the second network, information of a routable interface address of a user plane function in the first network, the information of a routable user plane address to be used for user plane data transfer with a user plane function in the second network.

According to a thirtieth aspect there is provided a computer program comprising instructions stored thereon for performing at least the following: receiving a request, from a network function repository function in a second network, the request including one or more of: information of a location of a user equipment; information of an interface between a first network and the second network, an apparatus being located in the first network; providing, to the network function repository function in the second network, information of a routable interface address of a user plane function in the first network, the information of a routable user plane address to be used for user plane data transfer with a user plane function in the second network.

According to a thirty first aspect there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the following: receiving a request, from a network function repository function in a second network, the request including one or more of: information of a location of a user equipment; information of an interface between a first network and the second network, the apparatus being located in the first network; providing, to the network function repository function in the second network, information of a routable interface address of a user plane function in the first network, the information of a routable user plane address to be used for user plane data transfer with a user plane function in the second network.

According to a thirty second aspect there is provided a non-transitory computer readable medium comprising program instructions stored thereon for performing at least the following: receiving a request, from a network function repository function in a second network, the request including one or more of: information of a location of a user equipment; information of an interface between a first network and the second network, an apparatus being located in the first network; providing, to the network function repository function in the second network, information of a routable interface address of a user plane function in the first network, the information of a routable user plane address to be used for user plane data transfer with a user plane function in the second network.

Brief description of Figures

The invention will now be described in further detail, by way of example only, with reference to the following examples and accompanying drawings, in which:

Figure 1 shows a schematic example of parts of a wireless 5G communication system;

Figure 2 shows a schematic example of parts of a wireless 5G communication system; Figure 3 is a signalling diagram schematically showing communication between entities in a wireless communication system;

Figure 4 is a signalling diagram schematically showing communication between entities in a wireless communication system;

Figure 5 schematically shows parts of a wireless communication device according to an example;

Figure 6 schematically shows parts of a control entity according to an example;

Figure 7 is a flow chart showing a method according to an example;

Figure 8 is a flow chart showing a method according to an example;

Figure 9 is a flow chart showing a method according to an example;

Figure 10 is a flow chart showing a method according to an example;

Figure 11 shows a schematic representation of a non-volatile memory medium storing instructions which when executed by a processor allow a processor to perform one or more of the steps of the methods of some embodiments.

Detailed description

3GPP TS 23.501 defines aspects of system architecture for the 5G system (5GS). 3GPPTS 23.501 covers both roaming and non-roaming scenarios, including interworking between 5GS and EPS (evolved packet system), mobility within 5GS, QoS (quality of service), policy control and charging, authentication and in general 5G System wide features e.g., SMS, Location Services, Emergency Services.

For background understanding, Figure 4.2.3-2 of 3GPP TS 23.501 is reproduced in Figure 1 of the appended Figures, which schematically shows nonroaming 5G system architecture. It is to be noted that the DN (data network) 108 may comprise an edge application server ((E)AS)) i.e. , an application server operating at the edge of the system. For further understanding, Figure 4.2.4-6 of 3GPP TS 23.501 is reproduced in Figure 2 of the appended Figures, which schematically shows system architecture for home routed scenario in reference point representation. A scenario to which the present disclosure relates is when “Edge Computing” (EC) data traffic is forwarded from a UPF to a (local) data network (DN). This may be done, for example, so that an application can run on a local server, for example to reduce latency. The application then runs closer to the UE, at the “network edge” - on the Edge Application Server (E)AS. To generally enable connection to the respective DN I (E)AS, a UPF connected to the respective DN has to be selected in the data path. This specific UPF acts as the “PDU Session Anchor” (PSA). It will therefore be appreciated that the present disclosure may relates to low latency services and /or edge computing services.

In other words, and with respect to Figures 1 and 2, due to mobility the UE 106 may leave a home network (HPLMN) 102 and roam into a visited network (VPLMN) 104. To maintain continuity, the connection between the UE 106 and the (E)AS 108 is maintained. The intermediate/visited UPF 110 (l/V UPF) is inserted while still meeting QoS requirements of the UE (e.g., delay, jitter). The PSA UPF 112 (PDU session anchor UPF) in the home network 102 stays connected with the (E)AS 108, and the new IA/-UPF 110 mediates between V-RAN 114 and H-UPF 112 (H-UPF remains a PSA UPF, in the same manner as it was before roaming began). On the other hand, it could be possible that, when the UE moves, also the (E)AS is changed, to keep the application close to the UE - when both home and visited (E)AS support the same applications. But this may not be preferred, as this would mean that the applicative session will be interrupted.

ETSUN (Enhancing Topology of SMF and UPF in 5G Networks) addresses the support of deployment topologies with specific SMF (session management function) Service Areas, in which case the V-SMF 118 has a N11 interface with the AMF (access and mobility management function) 120 in the visited network, and a N16a interface with the H-SMF 122. The V-SMF 118 is responsible for controlling the UPF(s) that the H-SMF cannot directly control. For example, see chapter 5.34 of TS 23.501 and for Handover, see chapter 4.23.7.3 of “Procedures of 5GS” TS 23.502. In case of HR (home routed) roaming the V-SMFA/-UPF take over the roles of the l-SMF/l-UPF in general and in case of HO (Handover) the V-SMFA/-UPF take over the roles of the target T-SMF/T-UPF. From a handover procedure perspective, the UE 102 is handed over from the source S-RAN in the H-PLMN to the target T-RAN in the V-PLMN.

It has been noted in the present application that there exists a problem that before handover (HO), the PSA UPF 112 is directly connected via N3 to source RAN 124 (see Figure 1 ). After the HO, the PSA UPF 112 is connected via N9 to the V-LIPF 110, and the V-LIPF 110 is connected via N3 to target RAN 114 (see Figure 2).

It is to be noted that the old N3 address of PSA (H-)LIPF 112 is meaningless for the new V-PLMN 104 (N3 is valid only within one and the same network). In other words, a problem is that (a V-SMF 118 in) a V-PLMN 104 has no knowledge of the architecture of the H-PLMN 102 (and, particularly, on the H-LIPFs e.g., H-LIPF 112). More precisely, a problem is that the address of the H-LIPF (PSA) 112 connected to the respective DN 108 is a network-internal address (“N3 address”, only valid and understood in the H-PLMN 102). The same principle is applicable for a HO for a HR UE roaming in the VPLMN1 to the HR roaming in another VPLMN2 (N9 address is not valid between HPLMN and different VPLMNs).

A selection process for a best suited V-UPF in V-PLMN needs to know the new N9 interface address of the UPF 112 in the H-PLMN, but this information is not available at the V-SMF 118 according to TS 23.502.

Therefore, the existing handover procedure may not be capable of selecting the optimal target T-UPF in the V-PLMN to meet the QoS requirements for the handed over PDU session.

However, in order to meet tight QoS requirements for delay/j itter, the existing IA/-UPF selection function may not provide the optimal location of the T-UPF in general and in case of URLLC (ultra-reliable low latency connection) services. Moreover, the selection function may not be sufficient to select the T-UPF based only on the location of the UE, as this may not provide the optimal location in practice. In some examples, it is noted that the optimal location for the IA/-UPF is on the shortest path between the T-RAN and the PSA (PDU session anchor), in order to meet the delay/jitter requirements. In other words, normally (i.e., without EC sessions), for UE handover to a V-PLMN it is specified that the V-SMF would select a V-UPF depending on some criteria and depending on the UE location, as - normally - it may be optimal to select a UPF close to the UE. However, in scenarios with ongoing EC sessions, it may be more important to select a V-UPF that is close to the PSA (i.e., to the H-UPF that is connected to the DN with the maintained (E)AS).

A prior art SMF selection process at the AMF (Access and Mobility Management Function) /NRFs (Network Function Repository Function) is discussed in 3GPP TS 23.502 at Figure 4.3.2.2.3.3-2 and the description relating thereto. See also Figure 4.23.7.3.2-1 of 3GPP TS 23.502, and the description relating thereto. See also Table 5.2.8.2.10-1 of 3GPP TS 23.502, which shows SM Context of a PDU Session transferred between l-SMF(s) or between V-SMF(s).

Before describing examples in detail, the present disclosure relates to a method and mechanism(s) for how an interface address can be provided from a H-PLMN side to V-PLMN side, when a UE is roaming. For example, the interface may be an N9 interface between the UPFs. In some examples, the interface may be an N3 interface between UPF and RAN.

To assist with explaining examples in more detail, a portion of Figure 4.23.7.3.2- 1 of 3GPP TS 23.502 is reproduced at Figure 3, with some annotations made thereon.

In a case of HR roaming of a UE 306, according to 3GPP TS 23.502 clause 4.23.7.3 the source S-AMF selects the target T-AMF in steps 1 to 3 of Figure 4.23.7.3.2-1 . For that purpose the S-AMF considers the target PLMN ID of the Target ID, which is the target ID of the target gNB, conveyed in the Handover Required message. The S-AMF invokes the Namf_Communication_CreateUEContext Request towards the selected T-AMF. According to TS 23.502 figure 4.23.7.3.2-1 (see Figure 3 appended), at step 3 the T- AMF invokes the IA/-SMF 318 with Nsmf_PDUSession_CreateSMContext (PDU Session ID, Target ID, T-AMF ID, SM Context ID) and the IA/-SMF 318 turns to the H-SMF 322 with Nsmf_PDUSession_Context Request and provides the PLMN ID of the V-PLMN 304 to the H-SMF 322.

According to the present disclosure, it is proposed that the H-SMF 322 shall detect the HR roaming case of UE 306 if the PLMN ID sent by the V-SMF 318 to the H-SMF 322 is different from H-SMFs own PLMN ID.

It is noted that in HR roaming case the l-SMF of the ETSUN case becomes the V-SMF, as the l-SMF of ETSUN is located in the V-PLMN. Therefore in places the notation l/V is used.

Two options (“Option A” and “Option B”) for sharing the new GTP-U N9 and/or N3 FTEID/IP Address I FQDN Ztoken/Handle with the V-PLMN 304 are discussed inturn below. Option A

In one example, and with reference to Figure 3, the H-PLMN 302 shall share the new GTP-U N9 and/or N3 FTEID/IP Address ZFQDN/token/ with the V-PLMN 304, where FTEID is Fully Qualified Tunnel Endpoint Identifier. Optionally, the IA/-SMF 318 may request the H-SMF 322 to share the new GTP-U N9 and/or N3 FTEID/IP Address /FQDN/token/. The l/V-SMF 318 in VPLMN 304 shall consider the new GTP-U N9 FTEIDIP Addr of H-PLMN 302 together with the SMF area Identity of the IA/-SMF 318 to select the IA/-UPF 310 in the V-PLMN 304. Therefore, with reference to Figure 3, it may be considered that at step 5a the l/V-SMF 318 optionally may request the H-SMF 322 to share the new GTP-U N9 and/or N3 FTEID/IP Addr /token/Handle. In step 5d the H-SMF 322 may share the GTP-U N9 and/or N3 FTEID/IP Addr /token/Handle with l/V-SMF 318.

It is to be noted that the V-NRF may have a database configured with N9 delays between V-UPFs (e.g., I/V-UPF 310) and H-UPFs (e.g., H-UPF 312)). HR roaming requires an SLA (Service level agreement) confirming interfaces between participants. In case NRF (network function repository function) does not maintain this database with N9 delays, then it may return a list of candidate UPFs based on matching criterias, etc.

If the IA/-SMF 318 receives a list of UPF(s) from NRF, the IA/-SMF may determine the most suitable UPF by also determining delay between V-UPF(s) and H- UPF(s). For example, the delay may be determined by using ping messages or routing messages.

In examples, the H-SMF 322 shares the new N9 Addr with IA/-SMF 318 as part of existing call sequence. For example, the H-SMF 322 may communicate the new N9 address at step 5d. of 4.23.7.3.2-1 , as shown in Figure 3.

Alternatively, the H-SMF 322 may signal the new N9 address in a new request/notification to the IA/-SMF 318. For example, the new N9 address may be communicated before the normal response (e.g., at step 5d) is sent as of existing sequence chart to the IA/-SMF 318.

In either case the IA/-SMF 318 then sends NRF query to V-NRF with IA/-SMF area Identity and N9 Address I FQDN and/or N3 FTEID/IP Addr /token/Handle. V- NRF suggests IA/-UPF candidates based on IA/-SMF 318 area Identity and N9 Address / FQDN and/or N3 FTEID/IP Addr /token/Handle. Then l/V-SMF 318 selects IA/-UPF. As shown in Figure 3, it is proposed that this information like N9 Address / FQDN and/or N3 FTEID/IP Address Ztoken/Handle shall be available at the l/V-SMF 318 before the UPF selection in step 6.

It will be understood that in some examples the H-LIPF 312 may comprise an “anchor” UPF, or session anchor UPF. However, it will also be understood that in some examples the H-UPF 312 may not be an anchor UPF. So although in some examples the respective UPF in the HPLMN may be the anchor, further (border or intermediate) UPF(s) may exist between the actual anchor and the V-PLMN.

Under “Option A”, according to the present disclosure clause 4.23.7.3.2-1 of TS 23.502 may be modified as follows (l-SMF insertion and l-SMF change scenarios are dealt with in-turn): l-SMF insertion

Clause 4.23.7.3.2-1 of TS 23.502

5a. Target V/I-SMF to SMF: Target V/I-SMF retrieves SM Context from the H-SMF by invoking Nsmf_PDUSession_Context Request (SM context type, SM Context ID).

The Target V/I-SMF uses SM Context ID received from T-AMF for this service operation. SM context type indicates that the requested information is all SM context, i.e. , PDN Connection Context and 5G SM context. The SM Context ID is used by the recipient of Nsmf_PDUSession_Context Request to determine the targeted PDU Session. Optionally the target IA/-SMF may indicate/request the use of additional N9 information and/or N3 FTEID/IP Addr /token/Handle.

5b. Void.

5c. Void.

The H-UPF 312 sends an N4 Session Establishment Response message to the SMF. If the H-UPF 312 was requested CN Tunnel Info (on N9) of UPF, it provides CN Tunnel Info (on N9) to the SMF.

5d. H-SMF to Target V/I-SMF: Nsmf_PDUSession_Context Response. The SMF responds with the requested SM context. Additionally, in case the PLMN ID received in the step 5a is different from H-SMF own PLMN ID, the SMF provides the new N9 FTEID/IP Address I FQDN or a token/handle obscuring the old (and meaning less) N3 IP address of the H-UPF 312 to the Target l-SMF. Alternatively, in addition, the SMF may issue a new operation (e.g Nsmf_PDUSession_ContextUpdate and or etc conforming with inherent SBA/SBI rules) towards the target SMF carrying the new N9 FTEID/IP Address I FQDN before responding with Nsmf_PDUSession_Context Response.

6. The Target V/I-SMF selects a Target V/I-UPF: Based on the received

SM context and the new N9 FTEID/IP Address I FQDN and/or a token/handle obscuring the old (and meaning less) N3 IP address of the H-LIPF 312at the H-PLMN 302, S-NSSAI, and UE location information, the Target V/I-SMF selects a Target V/I- UPF as described in clause 6.3.3 of TS 23.501 [2] and clause 5.2.7.3.2 of TS 23.502.

I-SMF change

Clause 4.23.7.3.2-1 of TS 23.502

4a. (I-SMF change case) Target l-SMF to Source l-SMF: Target l-SMF retrieves SM Context from the source l-SMF by invoking Nsmf_PDUSession_Context Request (SM context type, SM Context ID).

The Target l-SMF uses SM Context ID received from T-AMF for this service operation. SM context type indicates that the requested information is all SM context, i.e. , PDN Connection Context and 5G SM context. The SM Context ID is used by the recipient of Nsmf_PDUSession_Context Request in order to determine the targeted PDU Session.

4b. Source l-SMF to Target l-SMF: Nsmf_PDUSession_Context Response. The source l-SMF responds with the requested SM context.

4c. Target l-SMF to SMF: Target l-SMF retrieves SM Context from the SMF by invoking Nsmf_PDUSession_Context Request (SM context type, SM Context ID).

The Target l-SMF uses SM Context ID received from T-AMF for this service operation. SM context type indicates that the requested information is all SM context, i.e., PDN Connection Context and 5G SM context. The SM Context ID is used by the recipient of Nsmf_PDUSession_Context Request in order to determine the targeted PDU Session.

4d. The Target l-SMF selects a Target l-UPF: Based on the received SM context and the new N9 FTEID/IP address of the UPF(PSA), e.g. S-NSSAI, and UE location information, the Target l-SMF selects a Target l-UPF as described in clause 6.3.3 of TS 23.501 [2] and clause 5.2.7.3.2 of TS 23.502 . 6. The Target l-SMF selects a Target I-IIPF: Based on the received SM context and the new N9 FTEID/IP address of the UPF(PSA), e.g. S-NSSAI, and UE location information, the Target l-SMF selects a Target I-IIPF as described in clause 6.3.3 of TS 23.501 [2] and clause 5.27.3.2 of TS 23.502 .

Under option A (for both l-SMF insertion and l-SMF change), according to the present disclosure clause 5.27.3.2 of TS 23.502 may be modified as follows:

If the target NF is UPF, the request may include SMF Area Identity, N9 IPv4 Address/IPv6 Prefix of the UPF 312 at H-PLMN 302, UE IPv4 Address/IPv6 Prefix,

NOTE 5: The (UE) IPv4 address or (UE) IPv6 Prefix is provided for UPF discovery: in that case the NRF looks up for a match within one of the Range(s) of (UE) IPv4 addresses or Range(s) of (UE) IPv6 prefixes provided by UPF as part of the invocation of Nnrf_NFManagement_NFRegister operation. The NRF is not meant to store individual (UE) IPv4 addresses or (UE) IPv6 prefixes.

NOTE 6: Discovering UPF at PDU Session Establishment time and creating the N4 association assumes full connectivity between SMF and UPFs.

Option B

According to option B, the H-PLMN 302 shall share the new GTP-U N9 and/or N3 FTEID/IP Addr /token/handle with the V-PLMN 304.

The V-SMF 318 in V-PLMN 304 shall consider the new GTP-U N9 and/or N3 FTEIDIP Addr /token/handle of H-PLMN 302 together with the SMF area Identity of the l-SMF to select the V-UPF in the V-PLMN 304. As per the home routed roaming case the l-SMF of the ETSUN case becomes the V-SMF i.e the V-SMF inherits the functionality of the l-SMF, but because of HR roaming the V-SMF need to perform additional functionality. Therefore, as previously described, the notation l/V is used in places.

It is to be noted that the V-NRF may have a database (DB) configured with N9 delays between V-UPF(s) and H-UPF(s).

According to some examples, HR roaming requires an SLA confirming interfaces between participants. According to some examples, based on Option B) H-SMF 322 shares a token/handle/old N3 IP Address instead of the new defined N9 address as of option a with V-SMF 318. Since the V-SMF knows based on existence of token/handle and/or different PLMNs in the home routed case, the V-SMF 318 queries V-NRF with the SMF area Identity of the l-SMF and old N3 IP Address/new token and V-NRF sends a request to H-NRF. Based on the token/old N3 address, H-NRF returns the new N9 address to V-NRF.

According to some examples, the V-NRF suggests V-LIPF candidates based on l/V-SMF area Identity and new N9 address. Then, the l/V-SMF can select the V- UPF.

Under “Option B”, clause 4.23.7.3.2-1 of TS 23.502 may be modified as follows:

5a. Target l-SMF to SMF: Target l-SMF retrieves SM Context from the SMF by invoking Nsmf_PDUSession_Context Request (SM context type, SM Context ID).

The Target l-SMF uses SM Context ID received from T-AMF for this service operation. SM context type indicates that the requested information is all SM context, i.e. PDN Connection Context and 5G SM context. The SM Context ID is used by the recipient of Nsmf_PDUSession_Context Request in order to determine the targeted PDU Session. Optionally, V-SMF may indicate/request that new procedure described herein as Option B may be performed.

5b. Void.

5c. Void.

The -H-UPF 312sends an N4 Session Establishment Response message to the SMF. If the H-UPF 312 was requested CN Tunnel Info (on N9), it provides CN Tunnel Info (on N9) to the SMF.

5d. SMF to Target l-SMF: Nsmf_PDUSession_Context Response. The SMF responds with the requested SM context. Additionally, in case the PLMN ID received in step 5a is different from H-SMF own PLMN ID, the SMF provides the new N9 FTEID/IP address of the UPF(PSA) to the Target l-SMF or a token/handle obscuring the old (and meaningless) N3 IP address of the UPF. Alternatively in addition the SMF may issue a new operation (e.g., Nsmf_PDUSession_ContextUpdate and or etc conforming with inherent SBA/SBI rules) towards the target SMF carrying the new N9 FTEID /IP address before responding or a token/handle obscuring the old (and meaningless) N3 IP address of the UPF with Nsmf_PDUSession_Context Response.

6. The Target l-SMF selects a Target I-IIPF: Based on the received SM context and the new N9 FTEID/IP address of the UPF(PSA) or a token/handle obscuring the old (and meaningless) N3 IP address of the UPF, e.g. S-NSSAI, and UE location information, the Target l-SMF selects a Target l-UPF as described in clause 6.3.3 of TS 23.501 [2] and clause 5.2.7.3.2 of TS 23.502 as additionally depicted below where the V-SMF consults the V-NRF and the where the V-NRF queries the H-NRF for resolving the token/handle obscuring the old (and meaningless) N3 IP address.

Also, with reference to Figure 4, box 3A:

At step 1., The V-SMF 418 sends the Nnrf_NFDiscovery_Request containing the token/handle of the UPF of the H-PLMN to the V-NRF 450. Differently to prior art behavior where the V-NRF does not forward a query from a V-SMF to the H-NRF, at step 2. the V-NRF 450 forwards Nnrf_NFDiscovery_Request containing the token/handle to the H-NRF 452. In other words, this may be considered a query for discovering a user plane function. On receipt of the token/handle the H-NRF 452 converts the token/handle into a routable N9 interface address which it sends back to the V-NRF in the response at step 3a. the V-NRF 450, of course, is now prepared to receive the N9 interface address and performs the preselection of the candidate I- UPFs based on the N9 interface address and the location of the UE. The pre-selected candidate UPFs are sent back to the V-SMF 418 at step 3a. The V-SMF 418 selects the l-UPF from the candidate l-UPFs.

Box 3B in Figure 4 covers a case where the hNRF (home PLMN NRF) 452 on its own is not in a position to already translate to routable N9 address. Thus hNRF needs to consult a more local /dedicated NRF in Home PLMN.

According to the present disclosure, Clause 5.2.7.3.2 of TS 23.502 may also be modified as follows:

If the target NF is UPF, the request may include SMF Area Identity, N9 IPv4 Address/IPv6 Prefix of the H-UPF (312) or a token/handle obscuring the old and meaningless N3 IP address, UE IPv4 Address/IPv6 Prefix, supported ATSSS steering functionality

According to the present disclosure, the impact on the NRF interface is as follows:

TS 29.510 ch. 6.2.3.2.3.1 “GET”

Note: at the time of filing, NRF query does not consider H-LIPF for selection of V-LIPF, only SMF service area:

Of note is the n9info information element (IE).

It will thus be appreciated from the foregoing that during handover towards a home-routed roaming scenario, the V-SMF may (at least for cases with ongoing edge computing (EC) session or low latency session) also receive the N9 address of the respective H-LIPF (PSA). The V-SMF then also considers this information of N9 address of H-LIPF (PSA), when selecting a V-LIPF. The present disclosure describes multiple procedures that could enable this.

In some examples, the present disclosure builds on known handover procedures where a source (S-)SMF and a target (T-)SMF interact.

In some examples, in a roaming situation, the T-SMF is also a V-SMF, and the S-SMF is also a H-SMF. Handover to (home-routed) roaming, again, builds on the specifications of handover from an S-SMF to an l-SMF. In some examples the I- SMF (intermediate SMF) is an SMF that may handle UPFs that cannot be controlled for some reason by the “main SMF”. Still, the main SMF instructs the l-SMF how to handle the respective UPFs. Therefore, it may be considered, in some examples, that the V-SMF takes the role of an l-SMF.

According to examples, in a first step the S-SMF detects whether the T-SMF is an SMF of another PLMN, so as to determine whether the new procedure described herein (i.e., forwarding of the PSA’s N9 address) is necessary. In some examples, detecting whether the T-SMF is an SMF of another PLMN is carried out by comparing the (T-)PLMN ID of the T-SMF (which will be shared by the T-SMF with the S-SMF when the T-SMF contacts the S-SMF for “organizing” the handover), with the (S-)PLMN ID of the S-SMF itself. When the PLMN IDs are not the same, the S-SMF can conclude that the T-SMF is from another PLMN (and thus, a roaming case including “H-SMF / V-SMF” occurred.).

Then, when “roaming handover” is detected, the H-SMF can follow procedures as laid out in the foregoing to also forward the N9 address of the current PSA (H-UPF) to the V-SMF. The V-SMF can then consider this N9 address when selecting a V-UPF.

Handover from a non-roaming case to a home routed roaming case is one example where the concept of the present disclosure may be used. Handover from a HR roaming case with a V-PLMN1 to a HR roaming case with a different V-PLMN1 is another example. The concept is also applicable for mobility between SNPN1 (Standalone NPN (Non-Public Network)) and SNPN2 , as well as between PNI (Public Network lntegrated)-NPN/PLMNs and SNPN and vice versa. A different SNPN is identified by the PLMN ID + NID (network Identifier).

Therefore SMF/UPF are examples. SGW-C (serving gateway control plane) and SGW-U (serving gateway user plane) are further examples.

It will be noted that the disclosure discusses interfaces between a first network (e.g., HPLMN) and a second network (e.g., VPLMN). It will be appreciated that the interface between the first network and the second network may be used for user plane data transfer between the first network and the second network. The interface may be an interface between the user plane function in the first network and the user plane function in the second network used for user plane data transfer.

A possible wireless communication device will now be described in more detail with reference to Figure 5 showing a schematic, partially sectioned view of a communication device 500. Such a communication device is often referred to as user equipment (UE) or terminal. An appropriate mobile communication device may be provided by any device capable of sending and receiving radio signals. Non-limiting examples comprise a mobile station (MS) or mobile device such as a mobile phone or what is known as a ’smart phone’, a computer provided with a wireless interface card or other wireless interface facility (e.g., USB dongle), personal data assistant (PDA) or a tablet provided with wireless communication capabilities, or any combinations of these or the like. A mobile communication device may provide, for example, communication of data for carrying communications such as voice, electronic mail (email), text message, multimedia and so on. Users may thus be offered and provided numerous services via their communication devices. Non-limiting examples of these services comprise two-way or multi-way calls, data communication or multimedia services or simply an access to a data communications network system, such as the Internet. Users may also be provided broadcast or multicast data. Non-limiting examples of the content comprise downloads, television and radio programs, videos, advertisements, various alerts and other information.

A wireless communication device may be for example a mobile device, that is, a device not fixed to a particular location, or it may be a stationary device. The wireless device may need human interaction for communication or may not need human interaction for communication. In the present teachings the terms UE or “user” are used to refer to any type of wireless communication device.

The wireless device 500 may receive signals over an air or radio interface 507 via appropriate apparatus for receiving and may transmit signals via appropriate apparatus for transmitting radio signals. In Figure 5 transceiver apparatus is designated schematically by block 506. The transceiver apparatus 506 may be provided for example by means of a radio part and associated antenna arrangement. The antenna arrangement may be arranged internally or externally to the wireless device.

A wireless device is typically provided with at least one data processing entity 501 , at least one memory 502 and other possible components 503 for use in software and hardware aided execution of tasks it is designed to perform, including control of access to and communications with access systems and other communication devices. The data processing, storage and other relevant control apparatus can be provided on an appropriate circuit board and/or in chipsets. This feature is denoted by reference 504. The user may control the operation of the wireless device by means of a suitable user interface such as keypad 505, voice commands, touch sensitive screen or pad, combinations thereof or the like. A display 508, a speaker and a microphone can be also provided. Furthermore, a wireless communication device may comprise appropriate connectors (either wired or wireless) to other devices and/or for connecting external accessories, for example hands-free equipment, thereto. Figure 6 shows an example of a control apparatus for a communication system, for example to be coupled to and/or for controlling a station of an access system, such as a RAN node, e.g., a base station, gNB, a central unit of a cloud architecture or a node of a core network such as an MME or S-GW, a scheduling entity such as a spectrum management entity, or a server or host. The control apparatus may be integrated with or external to a node or module of a core network or RAN. In some embodiments, base stations comprise a separate control apparatus unit or module. In other embodiments, the control apparatus can be another network element such as a radio network controller or a spectrum controller. In some embodiments, each base station may have such a control apparatus as well as a control apparatus being provided in a radio network controller. The control apparatus 600 can be arranged to provide control on communications in the service area of the system. The control apparatus 600 comprises at least one memory 601 , at least one data processing unit 602, 603 and an input/output interface 604. Via the interface the control apparatus can be coupled to a receiver and a transmitter of the base station. The receiver and/or the transmitter may be implemented as a radio front end or a remote radio head. For example, the control apparatus 600 or processor 601 can be configured to execute an appropriate software code to provide the control functions.

Figure 7 is a flow chart of a method according to an example. The flow chart of Figure 7 is viewed from the perspective of an apparatus. For example, the apparatus may comprise a session management function in a visited network.

At S1 , the method comprises receiving information of an interface between a first network and a second network that is different from the first network. The apparatus is located in the second network and the first network is providing an user plane function interfacing with a data network serving a user equipment that has roamed in to the second network.

At S2, the method comprises selecting a user plane function in the second network, using the information of the interface.

Figure 8 is a flow chart of a method according to an example. The flow chart of Figure 8 is viewed from the perspective of an apparatus. For example, the apparatus may comprise a session management function in a home network.

At S1 the method comprises, in response to receiving a message from a session management function, determining whether the session management function is located in a second network that is different from a first network, the apparatus being located in the first network.

At S2, when it is determined that the session management function is located in said second network, the method comprises sending to the session management function information of an user plane interface between a user plane function in the first network and a user plane function in the second network.

Figure 9 is a flow chart of a method according to an example. The flow chart of Figure 9 is viewed from the perspective of an apparatus. For example, the apparatus may comprise a network function resource function in a visited network.

At S1 , the method comprises receiving a query for discovering a user plane function in a second network, the apparatus located in the second network and the query comprising one or more of: information of a location of a user equipment; information of an interface between a first network and the second network.

At S2, the method comprises using the information in the query to determine a candidate user plane function of the second network for interfacing with a user plane function in the first network.

Figure 10 is a flow chart of a method according to an example. The flow chart of Figure 10 is viewed from the perspective of an apparatus. For example, the apparatus may comprise a network function resource function in a home network.

At S1 , the method comprises receiving a request, from a network function repository function in a second network, the request including one or more of: information of a location of a user equipment; information of an interface between a first network and the second network, the apparatus being located in the first network.

At S2, the method comprises providing, to the network function repository function in the second network, information of a routable interface address of a user plane function in the first network, the information of a routable user plane address to be used for user plane data transfer with a user plane function in the second network.

Figure 11 shows a schematic representation of non-volatile memory media 1100a (e.g., computer disc (CD) or digital versatile disc (DVD)) and 1100b (e.g., universal serial bus (USB) memory stick) storing instructions and/or parameters 1102 which when executed by a processor allow the processor to perform one or more of the steps of the methods of Figures 7 to 10. In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic, or any combination thereof. Some aspects of the disclosure may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor, or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques, or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

In general, the various embodiments may be implemented in hardware or special purpose circuits, software, logic, or any combination thereof. Some aspects of the invention may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor, or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques, or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

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. 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.

The embodiments of this invention may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Computer software or program, also called program product, including software routines, applets and/or macros, may be stored in any apparatus-readable data storage medium and they comprise program instructions to perform particular tasks. A computer program product may comprise one or more computer-executable components which, when the program is run, are configured to carry out embodiments. The one or more computer-executable components may be at least one software code or portions of it.

Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media such as hard disk or floppy disks, and optical media such as for example DVD and the data variants thereof, CD. The physical media is a non-transitory media.

The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may comprise one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), FPGA, gate level circuits and processors based on multi core processor architecture, as non-limiting examples.

Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate. The foregoing description has provided by way of non-limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this invention will still fall within the scope of this invention as defined in the appended claims. Indeed, there is a further embodiment comprising a combination of one or more embodiments with any of the other embodiments previously discussed.

Claims

1. An apparatus comprising means for performing: receiving information of an interface between a first network and a second network that is different from the first network, wherein the apparatus is located in the second network and the first network is providing an user plane function interfacing with a data network serving a user equipment that has roamed in to the second network; and selecting a user plane function in the second network, using the information of the interface.

2. An apparatus according to claim 1 , wherein the information of an interface between a first network and a second network comprises one or more of: an internet protocol address of the user plane function in the first network; a fully qualified domain name of the user plane function in the first network; a token obscuring an internet protocol address of the user plane function in the first network.

3. An apparatus according to claim 1 or claim 2, wherein the user plane function in the first network provides edge computing services to the user equipment.

4. An apparatus according to any of claims 1 to 3, wherein the selecting a user plane function in the second network comprises sending a query to a network function repository function.

5. An apparatus according to claim 4, wherein the query comprises one or more of: location information of the user plane function in the first network; internet protocol address or fully qualified domain name of the user plane function in the first network; token information of the user plane function in the first network.

6. An apparatus according to any of claims 4 to 5, wherein the means are further configured to perform receiving, from the network function repository function, a plurality of candidate user plane functions in the second network, and the selecting a user plane function in the second network comprises selecting a user plane function from the plurality of said candidate user plane functions.

7. An apparatus according to claim 6, wherein the selecting a user plane function in the second network comprises selecting a user plane function in the second network having a lowest user plane path delay with the user plane function in the first network.

8. An apparatus according to claim 7, wherein the selecting a user plane function in the second network comprises selecting a user plane function having a lowest user plane path delay with an intermediate user plane function in the first network.

9. An apparatus according to any of claims 1 to 8, wherein the first network comprises a home network of the user equipment and the second network comprises a visited network of the user equipment.

10. An apparatus according to any of claims 1 to 9, wherein the means are further configured to perform indicating that the apparatus supports receiving information of an interface between the first network and the second network.

11. An apparatus according to any of claims 1 to 10, wherein the apparatus receives said information of an interface between a first network and a second network in a packet data unit session context response or in a packet data unit session update response.

12. An apparatus according to any of claims 1 to 11 , wherein the apparatus comprises a session management function located in the second network.

13. An apparatus comprising means for performing: in response to receiving a message from a session management function, determining whether the session management function is located in a second network that is different from a first network, the apparatus being located in the first network; and when it is determined that the session management function is located in said second network, sending to the session management function information of an user plane interface between a user plane function in the first network and a user plane function in the second network.

14. An apparatus according to claim 13, wherein the said user plane function in the first network provides edge computing services to a user equipment.

15. An apparatus according to claim 13 or claim 14, wherein the information of an user plane interface between the first network and the second network comprises one or more of: an internet protocol address of the user plane function in the first network; a fully qualified domain name of the user plane function in the first network; a token obscuring an internet protocol address of the user plane function in the first network.

16. An apparatus according to any of claims 13 to 15, wherein the message from the session management function is received in a packet data unit session context request message or a packet data unit session update request message.

17. An apparatus according to any of claims 13 to 16, wherein the information of the interface is provided to the session management function in a packet data unit session context response message or packet data unit session update response message.

18. An apparatus according to any of claims 13 to 17, wherein the first network comprises a home network of the user equipment and the second network comprises a visited network of the user equipment.

19. An apparatus according to any of claims 13 to 18, wherein the apparatus comprises a session management function located in the first network.

20. An apparatus comprising means for performing: receiving a query for discovering a user plane function in a second network, the apparatus located in the second network and the query comprising one or more of: information of a location of a user equipment; information of an interface between a first network and the second network; and using the information in the query to determine a candidate user plane function of the second network for interfacing with a user plane function in the first network.

21. An apparatus according to claim 20, wherein said information of an interface between a first network and the second network comprises one or more of: an internet protocol address of the user plane function in the first network; a fully qualified domain name of the user plane function in the first network; a token obscuring an internet protocol address of the user plane function in the first network.

22. An apparatus according to claim 20 or claim 21 , the means further configured to perform sending the query to a network function repository function located in the first network; and receiving, from the network function repository function located in the first network, information of a routable interface address or name for interfacing between the first network and the second network.

23. An apparatus according to claim 22, wherein the information of an interface between a first network and a second network received from the network function repository function located in the first network comprises one or more of: an internet protocol address of the user plane function in the first network; a fully qualified domain name of the user plane function in the first network.

24. An apparatus according to any of claims 20 to 23, wherein the apparatus comprises a network function repository function located in the second network.

25. An apparatus comprising means for performing: receiving a request, from a network function repository function in a second network, the request including one or more of: information of a location of a user equipment; information of an interface between a first network and the second network, the apparatus being located in the first network; providing, to the network function repository function in the second network, information of a routable interface address of a user plane function in the first network, the information of a routable user plane address to be used for user plane data transfer with a user plane function in the second network.

26. An apparatus according to claim 25, wherein the apparatus comprises a network function repository function located in the first network.

27. A method performed by an apparatus, comprising: receiving information of an interface between a first network and a second network that is different from the first network, wherein the apparatus is located in the second network and the first network is providing an user plane function interfacing with a data network serving a user equipment that has roamed in to the second network; and selecting a user plane function in the second network, using the information of the interface.

28. A method performed by an apparatus, comprising: in response to receiving a message from a session management function, determining whether the session management function is located in a second network that is different from a first network, the apparatus being located in the first network; and when it is determined that the session management function is located in said second network, sending to the session management function information of an user plane interface between a user plane function in the first network and a user plane function in the second network.

29. A method performed by an apparatus, comprising: receiving a query for discovering a user plane function in a second network, the apparatus located in the second network and the query comprising one or more of: information of a location of a user equipment; information of an interface between a first network and the second network; and using the information in the query to determine a candidate user plane function of the second network for interfacing with a user plane function in the first network.

30. A method performed by an apparatus, comprising: receiving a request, from a network function repository function in a second network, the request including one or more of: information of a location of a user equipment; information of an interface between a first network and the second network, the apparatus being located in the first network; providing, to the network function repository function in the second network, information of a routable interface address of a user plane function in the first network, the information of a routable user plane address to be used for user plane data transfer with a user plane function in the second network.

31. A computer program comprising instructions for causing an apparatus to perform at least the following: receiving information of an interface between a first network and a second network that is different from the first network, wherein the apparatus is located in the second network and the first network is providing an user plane function interfacing with a data network serving a user equipment that has roamed in to the second network; and selecting a user plane function in the second network, using the information of the interface.

32. A computer program comprising instructions for causing an apparatus to perform at least the following: in response to receiving a message from a session management function, determining whether the session management function is located in a second network that is different from a first network, the apparatus being located in the first network; and when it is determined that the session management function is located in said second network, sending to the session management function information of an user plane interface between a user plane function in the first network and a user plane function in the second network.

33. A computer program comprising instructions for causing an apparatus to perform at least the following: receiving a query for discovering a user plane function in a second network, the apparatus located in the second network and the query comprising one or more of: information of a location of a user equipment; information of an interface between a first network and the second network; and using the information in the query to determine a candidate user plane function of the second network for interfacing with a user plane function in the first network.

34. A computer program comprising instructions for causing an apparatus to perform at least the following: receiving a request, from a network function repository function in a second network, the request including one or more of: information of a location of a user equipment; information of an interface between a first network and the second network, the apparatus being located in the first network; providing, to the network function repository function in the second network, information of a routable interface address of a user plane function in the first network, the information of a routable user plane address to be used for user plane data transfer with a user plane function in the second network.