Method and apparatus for user plane function selection

Abstract

Various embodiments of the present disclosure provide a method for user plane function (UPF) selection The method which may be performed by a first network node comprises: transmitting first information indicating an access type interworking gateway (ATIG) towards a second network node, and receiving a list of UPFs transmitted by the second network node. The ATIG indicated by the first information is preferred for each of the list of the UPFs according to second information per UPF registered at the second network node. The second information per UPF indicates one or more preferred ATIGs for the UPF. In accordance with an exemplary embodiment, the method further comprises: selecting a UPF preferred for the ATIG from the list of the UPFs.

Description

METHOD AND APPARATUS FOR USER PLANE FUNCTION SELECTIONFIELD OF THE INVENTION

[0001] The present disclosure generally relates to communication networks, and more specifically, to a method and apparatus for user plane function (UPF) selection.BACKGROUND

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

[0003] With the rapid development of networking and communication technologies, wireless communication networks such as long-term evolution (LTE)Zfourth generation (4G) network and new radio (NR) / fifth generation (5G) network are expected to achieve high traffic capacity and transmission efficiency. In order to meet the diverse requirements of new services across a wide variety of industries, the 3rd generation partnership project (3GPP) is developing various network function (NF) services for the communication system architecture (e.g., 5G system (5GS) architecture, etc.). The service-based architecture (SBA) under development for the next generation network can restructure the core network control plane and divide it into multiple independent modules with decoupled functions that can be updated individually. The introduction of the service-based interface protocols and network-function repository function (NRF) may enable the function modules to be used flexibly. In the SBA, service discovery may be provided for individual network functions (NFs) by an NRF, so as to meet different service requirements. Considering the diversity of network capabilities and access types (e.g., 3GPP access or non-3GPP access), management and selection of various network services with different configurations and requirements may become more challenging.SUMMARY

[0004] 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.

[0005] Communication networks may be supposed to support the wide range of performance requirements demanded by multiple access technologies, a variety of services and new device types. A terminal device such as user equipment (UE) may be provided with various services by a communication network via different network nodes and / or functional entities. For a UE registering with the communication network over non-3GPP access (e.g., via S2b wirelessfidelity (WiFi) access, etc.) and connecting to a session management function (SMF) via a wireless access point (AP) and an evolved packet data gateway (ePDG), it may be advantageous that the SMF can select a UPF close to the ePDG compared to selecting a UPF close to the UE, because the UPF selection based on the UE's location may fail(e.g., in the case that the UE roams from a home network to a visited network and the SMF in the home network may not be able to control the UPF in the visited network), or even if it does not fail, more network resources may be required due to a long transfer path for the user plane traffic. However, the existing solutions do not support the UPF selection based on the current ePDG used for the UE. Other non-3GPP access cases using different access type interworking gateways (ATIG) or functions (e.g., a wireline access gateway function (WAGF / W-AGF), a trusted non-3GPP gateway function (TNGF), or a trusted wide local area network interworking function (TWIF), etc.) also have similar issues. Therefore, it may be desirable to improve UPF selection, especially for non-3GPP access.

[0006] Various exemplary embodiments of the present disclosure propose a solution for UPF selection, which can enable a UPF to register its preferred ATIG(s) to a repository (e.g., an NRF, etc.), so that a network node (e.g., an SMF, etc.) can obtain from the repository, e.g., by indicating an ATIG to the repository, a list including one or more UPFs preferring the indicated ATIG, and select a preferred UPF for the indicated ATIG from the list.

[0007] According to a first aspect of the present disclosure, there is provided a method performed by a first network node (e.g., an SMF, etc.). The method comprises: transmitting first information indicating an ATIG towards a second network node, and receiving a list of UPFs transmitted by the second network node. The ATIG indicated by the first information may be preferred for each of the list of the UPFs according to second information per UPF registered at the second network node. The second information per UPF indicates one or more preferred ATIGs for the UPF. In accordance with an exemplary embodiment, the method further comprises: selecting a UPF preferred for the ATIG from the list of the UPFs.

[0008] In accordance with an exemplary embodiment, the first information may comprise available endpoint address information and / or available endpoint fully qualified domain name (FQDN) information of the ATIG.

[0009] In accordance with an exemplary embodiment, the second information per UPF may comprise available endpoint address information and / or available endpoint FQDN information of the one or more preferred ATIGs for the UPF.

[0010] In accordance with an exemplary embodiment, the one or more preferred ATIGs for the UPF may include: one or more ATIGs close to the UPF; and / or one or more ATIGs prioritized for the UPF; and / or one or more ATIGs dedicated to the UPF.

[0011] In accordance with an exemplary embodiment, the ATIG may be an ePDG, a WAGF, a TNGF or a TWIF.

[0012] In accordance with an exemplary embodiment, the selected UPF may be a UPF close to the ATIG.

[0013] In accordance with an exemplary embodiment, the first network node may be configured to implement an SMF.

[0014] In accordance with an exemplary embodiment, the second network node may be configured to implement an NRF.

[0015] According to a second aspect of the present disclosure, there is provided an apparatus which may be implemented as a first network node. The apparatus may comprise one or more processors and one or more memories storing computer program codes. The one or more memories and the computer program codes may be configured to, with the one or more processors, cause the apparatus at least to perform any step of the method according to the first aspect of the present disclosure.

[0016] According to a third aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the first aspect of the present disclosure.

[0017] According to a fourth aspect of the present disclosure, there is provided an apparatus which may be implemented as a first network node. The apparatus may comprise a transmitting unit, a receiving unit and a selecting unit. In accordance with some exemplary embodiments, the transmitting unit may be operable to carry out at least the transmitting step of the method according to the first aspect of the present disclosure. The receiving unit may be operable to carry out at least the receiving step of the method according to the first aspect of the present disclosure. The selecting unit may be operable to carry out at least the selecting step of the method according to the first aspect of the present disclosure.

[0018] According to a fifth aspect of the present disclosure, there is provided a method performed by a second network node (e.g., an NRF, etc.). The method comprises: receiving first information indicating an ATIG transmitted by a first network node, and determining a list of UPFs according to the first information and second information per UPF registered at the second network node. The second information per UPF indicates one or more preferred ATIGs for the UPF. The ATIG indicated by the first information may be preferred for each of the list of the UPFs. In accordance with an exemplary embodiment, the method further comprises: transmitting the list of the UPFs towards the first network node.

[0019] In accordance with an exemplary embodiment, the first information received by the second network node according to the fifth aspect of the present disclosure may correspond to the first information transmitted by the first network node according to the first aspect of the present disclosure. Thus, the first information according to the first and fifth aspects of the present disclosure may have the same or similar contents and / or feature elements. Similarly, the second information according to the first and fifth aspects of the present disclosure may have the same or similar contents and / or feature elements.

[0020] In accordance with an exemplary embodiment, the list of the UPFs transmitted by the second network node according to the fifth aspect of the present disclosure may correspond to the list of the UPFs received by the first network node according to the first aspect of the present disclosure. Thus, the list of the UPFs according to the firstand fifth aspects of the present disclosure may have the same or similar contents and / or feature elements.

[0021] In accordance with an exemplary embodiment, the method according to the fifth aspect of the present disclosure may further comprise: obtaining the second information per UPF by receiving a register request for a corresponding UPF transmitted by a third network node. In an embodiment, the register request may include the second information of the corresponding UPF.

[0022] In accordance with an exemplary embodiment, the method according to the fifth aspect of the present disclosure may further comprise: transmitting a register response towards the third network node. In an embodiment, the register response may indicate a profile with the second information of the corresponding UPF.

[0023] In accordance with an exemplary embodiment, the third network node may be configured to implement the corresponding UPF.

[0024] In accordance with an exemplary embodiment, the first network node may be configured to implement an SMF.

[0025] In accordance with an exemplary embodiment, the second network node may be configured to implement an NRF.

[0026] According to a sixth aspect of the present disclosure, there is provided an apparatus which may be implemented as a second network node. The apparatus may comprise one or more processors and one or more memories storing computer program codes. The one or more memories and the computer program codes may be configured to, with the one or more processors, cause the apparatus at least to perform any step of the method according to the fifth aspect of the present disclosure.

[0027] According to a seventh aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the fifth aspect of the present disclosure.

[0028] According to an eighth aspect of the present disclosure, there is provided an apparatus which may be implemented as a second network node. The apparatus may comprise a receiving unit, a determining unit and a transmitting unit. In accordance with some exemplary embodiments, the receiving unit may be operable to carry out at least the receiving step of the method according to the fifth aspect of the present disclosure. The determining unit may be operable to carry out at least the determining step of the method according to the fifth aspect of the present disclosure. The transmitting unit may be operable to carry out at least the transmitting step of the method according to the fifth aspect of the present disclosure.

[0029] According to a ninth aspect of the present disclosure, there is provided a method performed by a third network node (e.g., a UPF, etc.). The method comprises: determining second information of a UPF. The secondinformation of the UPF indicates one or more preferred ATIGs for the UPF. In accordance with an exemplary embodiment, the method further comprises: transmitting a register request for the UPF towards a second network node. The register request may include the second information of the UPF.

[0030] In accordance with an exemplary embodiment, the second information according to the ninth aspect of the present disclosure may correspond to the second information according to the first and fifth aspects of the present disclosure. Thus, the second information according to the first, fifth and ninth aspects of the present disclosure may have the same or similar contents and / or feature elements. Similarly, the one or more preferred ATIGs for the UPF indicated by the second information according to the first, fifth and ninth aspects of the present disclosure may refer to the same or similar functional elements and / or network entities.

[0031] In accordance with an exemplary embodiment, the method according to the ninth aspect of the present disclosure may further comprise: receiving a register response transmitted by the second network node. The register response may indicate a profile with the second information of the UPF.

[0032] In accordance with an exemplary embodiment, the second network node may be configured to implement an NRF.

[0033] In accordance with an exemplary embodiment, the third network node may be configured to implement the UPF.

[0034] According to a tenth aspect of the present disclosure, there is provided an apparatus which may be implemented as a third network node. The apparatus may comprise one or more processors and one or more memories storing computer program codes. The one or more memories and the computer program codes may be configured to, with the one or more processors, cause the apparatus at least to perform any step of the method according to the ninth aspect of the present disclosure.

[0035] According to an eleventh aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the ninth aspect of the present disclosure.

[0036] According to a twelfth aspect of the present disclosure, there is provided an apparatus which may be implemented as a third network node. The apparatus may comprise a determining unit and a transmitting unit. In accordance with some exemplary embodiments, the determining unit may be operable to carry out at least the determining step of the method according to the ninth aspect of the present disclosure. The transmitting unit may be operable to carry out at least the transmitting step of the method according to the ninth aspect of the present disclosure.

[0037] According to various exemplary embodiments, a first network node (e.g., an SMF, etc.) may be able to select a preferred UPF for an ATIG (e.g., an ePDG, a WAGF, a TNGF, a TWIF, etc.) from one or more UPFs whichmay be provided by a second network node (e.g., an NRF, etc.) according to ATIG related preference information per UPF. This can achieve improvement of UPF selection for various access types (e.g., 3GPP access or non-3GPP access) with optimized transfer path and increased resource efficiency.BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The disclosure itself, the preferable mode of use and further objectives are best understood by reference to the following detailed description of the embodiments when read in conjunction with the accompanying drawings, in which:Fig. 1 A is a diagram illustrating exemplary coding of a fully qualified tunnel endpoint identifier (F-TEID) according to an embodiment of the present disclosure.Fig. 1 B is a diagram illustrating exemplary coding of a trusted WLAN access network (TWAN) identifier according to an embodiment of the present disclosure.Fig. 2A is a diagram illustrating an exemplary UPF selection procedure according to an embodiment of the present disclosure.Fig. 2B is a diagram illustrating an exemplary UPF selection procedure according to another embodiment of the present disclosure.Fig. 3 is a flowchart illustrating a method according to an embodiment of the present disclosure.Fig. 4 is a flowchart illustrating another method according to an embodiment of the present disclosure.Fig. 5 is a flowchart illustrating yet another method according to an embodiment of the present disclosure.Fig. 6 is a block diagram illustrating an apparatus according to an embodiment of the present disclosure.Fig. 7A-7C are block diagrams illustrating various apparatus according to some embodiments of the present disclosure.DETAILED DESCRIPTION

[0039] The embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the present disclosure, rather than suggesting any limitations on the scope of the present disclosure. Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present disclosure should be or are in any single embodiment of the disclosure. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodimentis included in at least one embodiment of the present disclosure. Furthermore, the described features, advantages, and characteristics of the disclosure may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the disclosure may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the disclosure.

[0040] As used herein, the term "communication network” refers to a network following any suitable communication standards, such as new radio (NR), long term evolution (LTE), LTE-Advanced, wideband code division multiple access (WCDMA), high-speed packet access (HSPA), and so on. Furthermore, the communications between a terminal device and a network node in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1 G), the second generation (2G), 2.5G, 2.75G, the third generation (3G), 4G, 4.5G, 5G communication protocols, and / or any other protocols either currently known or to be developed in the future.

[0041] As used herein, the terms "first”, "second” and so forth refer to different elements. The singular forms "a” and "an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms "comprises”, "comprising”, "has”, "having”, "includes” and / or "including” as used herein, specify the presence of stated features, elements, and / or components and the like, but do not preclude the presence or addition of one or more other features, elements, components and / or combinations thereof. The term "based on” is to be read as "based at least in part on”. The term "one embodiment” and "an embodiment” are to be read as "at least one embodiment”. The term "another embodiment” is to be read as "at least one other embodiment”. Other definitions, explicit and implicit, may be included below.

[0042] The registration management may be used to register or deregister a UE / user with the network, and establish the user context in the network. A UE / user may need to register with the network to receive services that requires registration. As described in section 5.3.2.3 of 3GPP technical specification (TS) 23.501 V18.2.2, registration area management may comprise the functions to allocate and reallocate a registration area to a UE. Registration area may be managed per access type, e.g., 3GPP access or non-3GPP access. When a UE registers with the network over the 3GPP access, an access and mobility management function (AMF) may allocate a set of tracking areas in a tracking area identity (TAI) list to the UE. TAI used for non-3GPP access may need to be dedicated to non-3GPP access. TAI(s) dedicated to non-3GPP access may be defined in a public land mobile network (PLMN) and apply within this PLMN. Each non-3GPP interworking function (N3IWF), TNGF, TWIF and WAGF is locally configured with one TAI value. Each N3IWF, TNGF, TWIF and WAGF may be configured with a different TAI value or with the same TAI value as other N3IWFs, TNGFs, TWIFs and / or WAGFs. The TAI may be provided to the AMF during N2 interface setup and as part of the user location information in UE associated messages as described in 3GPP TS 38.413 V17.5.0.

[0043] The selection and reselection of a UPF for protocol data unit (PDU) session establishment, UE mobility or UE traffic offloading may be performed by an SMF by considering UPF deployment scenarios such as centrallylocated UPF and distributed UPF located close to or at the access network site. The SMF provisioning of available UPF(s) is described in section 6.3.3.2 of 3GPP TS 23.501 V18.2.2. The SMF may be locally configured with the information about the available UPFs, e.g. by operation, administration and maintenance (OA&M) system when UPF is instantiated or removed. It is noted that UPF information can be updated, e.g. by OA&M system any time after the initial provisioning, or UPF itself updates its information to the SMF any time after the node level interaction is established. The UPF selection functionality in the SMF may optionally utilize the NRF to discover UPF instance(s). In this case, the SMF may issue a request to the NRF that may include following parameters: data network name (DNN), single-network slice selection assistance information (S-NSSAI), SMF area identity, access traffic steering, switching, splitting (ATSSS) steering capabilities. In its answer, the NRF may provide the NF profile(s) that include(s) the Internet protocol (IP) address(es) or the FQDN of the N4 interface of corresponding UPF instance(s) to the SMF.

[0044] According to the contents about selection of an UPF for a particular PDU session mentioned in section 6.3.3.3 of 3GPP TS 23.501 V18.2.2, the following parameter(s) and information may be considered by the SMF for UPF selection and re-selection:UPF's dynamic load;Analytics (i.e. statistics or predictions) for UPF load, Service Experience analytics and / or DN Performance analytics per UP path (including UPF and / or DNAI and / or AS instance) and UE related analytics (UE mobility, UE communication, and expected UE behavioral parameters) as received from NWDAF (see TS 23.288), if NWDAF is deployed;UPF's relative static capacity among UPFs supporting the same DNN;UPF location available at the SMF;UE location information;Capability of the UPF and the functionality required for the particular UE session: An appropriate UPF can be selected by matching the functionality and features required for a UE;Data Network Name (DNN);PDU Session Type (i.e. IPv4, IPv6, 1 Pv4v6, Ethernet Type or Unstructured Type) and if applicable, the static IP address / prefix;SSC mode selected for the PDU Session;UE subscription profile in UDM;DNAI as included in the PCC Rules and described in clause 5.6.7;Local operator policies;- S-NSSAI;Access technology being used by the UE;Information related to user plane topology and user plane terminations, that may be deduced from:- 5G-AN-provided identities (e.g. CelllD, TAI), available UPF(s) and DNAI(s);Identifiers (i.e. a FQDN and / or IP address(es)) of N3 terminations provided by a W-AGF or a TNGF or a TWIF;Information regarding the user plane interfaces of UPF(s). This information may be acquired by the SMF using N4;Information regarding the N3 User Plane termination(s) of the AN serving the UE. This may be deduced from 5G-AN-provided identities (e.g. CelllD, TAI);Information regarding the N9 User Plane term! nation (s) of UPF(s) if needed;Information regarding the User plane termination(s) corresponding to DNAI(s);RSN, support for redundant GTP-U path or support for redundant transport path in the transport layer (as in clause 5.33.2) when redundant UP handling is applicable;Information regarding the ATSSS Steering Capability of the UE session (e.g. any combination of ATSSS-LL capability, MPTCP capability, MPQUIC capability) and information on the UPF support of RTT measurements without PMF;Support for UPF allocation of IP address / prefix;Support of the IPUPS functionality, specified in clause 5.8.2.14;Support for High latency communication (see clause 5.31 .8);User Plane Latency Requirements within AF request (see clause 5.6.7.1 and clause 6.3.6 of TS 23.548).NOTE 1 : How the SMF determines information about the user plane network topology from information listed above, and what information is considered by the SMF, is based on operator configuration.NOTE 2: In this release the SMF uses no additional parameters for UPF selection for a PDU Session servingTSO. If a PDU Session of a specific DS-TT needs to connect to a specific UPF hosting a specific TSN 5GS bridge, this can be achieved e.g. by using a dedicated DNN / S-NSSAI combination.

[0045] A WAGF or a TNGF may provide identifiers of its N3 terminations when forwarding over N2 uplink non- access stratum (NAS) signaling to the 5G core network (5GC). The AMF may relay this information to the SMF, as part of session management signaling for a new PDU session.

[0046] As to the UE location information, 3GPP TS 29.502 V18.3.0 mentions in section 5.2.3.4 that when attributes with the UserLocation data type (as defined in clause 5.4.4.7 of 3GPP TS 29.571 V18.2.0) are included in the messages (as specified in clause 6) to report the UE location information to the SMF, the following information may need to be included in these attributes:the TAI and NCGI for NR user location; or the TAI and ECGI for E-UTRA user location; or the TAI, UE local IP address, Port if NAT is detected, and optionally n3l wid if available, for untrusted non-3GPP access; or - the TAI and TNAP Id / TWAP Id for trusted non-3GPP access; or the TAI and GLI and optionally LineType if available, or the TAI and hfcNodeld, or the TAI and GCI, for wireline network access.

[0047] As an example, Table 1 gives the definition of type N3gaLocation, which corresponds to Table 5.4.4.10- 1 in section 5.4.4.10 of 3GPP TS 29.571 V18.2.0. Table 1

[0048] As another example, Table 2 lists some information elements (lEs) in a create session request, and more details may be found in Table 7.2.1-1 at section 7.2.1 of 3GPP TS 29.274 V18.3.0.Table 2Figure 1A

[0049] Fig.1 A is a diagram illustrating exemplary coding of a F-TEID according to an embodiment of the present disclosure. In accordance with an exemplary embodiment, the F-TEID may be coded as depicted in Fig.1 A, and more details may be found in Figure 8.22-1 at section 8.22 of 3GPP TS 29.274 V18.3.0. Figure 1B

[0050] Fig.1 B is a diagram illustrating exemplary coding of a TWAN identifier according to an embodiment of the present disclosure. According to the contents in section 8.100 of 3GPP TS 29.274 V18.3.0, the TWAN identifier may be used for reporting UE location in a TWAN (see 3GPP TS 23.402 V18.2.0). In accordance with an exemplary embodiment, the TWAN identifier may be coded as depicted in Fig.l B, and more details may be found in Figure 8.100- 1 at section 8.100 of 3GPP TS 29.274 V18.3.0.

[0051] In addition, some definitions of type "Upflnfo”, type “WAgflnfo”, type “Tngflnfo” and type “Twifl nfo" are given in Tables 3-6, which correspond to Table 6.1.6.2.13-1, Table 6.1.6.2.51-1, Table 6.1.6.2.52-1 and Table 6.1.6.2.61-1 of 3GPP TS 29.510 V18.3.0, respectively.Table 3Table 4Table 5Table 6

[0052] As described in section 4.5.4 of 3GPP TS 23.402 V18.2.0, a UE may perform ePDG selection based on a set of information configured by the home PLMN (HPLMN) in the UE, and based on the UE's knowledge of the PLMN it is attached to. A UE connected to one or multiple packet data network gateways (PDN GWs) may use a single ePDG. Regarding ePDG FQDNs construction, when the UE attempts to construct an FQDN for selecting an ePDG in a certain PLMN-x (either a visited PLMN (VPLMN) or the HPLMN), then the UE may construct one of the following FQDN formats:Operator Identifier FQDN: The UE constructs the FQDN by using the PLMN-x ID as the Operator Identifier.Tracking / Location Area Identity FQDN: The UE constructs the FQDN by using the identity of the Tracking Area / Location Area it is located in (i.e. based on PLMN-x ID and TAC / LAC). The Tracking / Location Area Identity FQDN is used to support location-specific ePDG selection within a PLMN.

[0053] The ePDG FQDN formats may be specified as described in 3GPP TS 23.003 V18.2.0. According to the contents in section 4.5.4.2 of 3GPP TS 23.402 V18.2.0, the UE may select one of the above FQDN formats as follows: a) If the UE attempts to select an ePDG in the registered PLMN and the UE is configured to use for this PLMN the Tracking / Location Area Identity FQDN as defined in point 2) of clause 4.5.4.3; and b) The UE knows the TAI / LAI of the area the UE it is located in (e.g. the TAI / LAI from the most recent Attach or TAU / LAU), then the UE may construct a Tracking / Location Area Identity FQDN. Otherwise the UE may construct the Operator Identifier FQDN.

[0054] Also, the UE may construct the Operator Identifier FQDN as a fallback in the case of failure of DNS resolution of a Tracking / Location Area Identity based FQDN.

[0055] According to 3GPP standards, NRF discovery for UPF selection is a way to select a suitable UPF for a PDU session in an SMF, e.g., as defined by 3GPP TS 23.501 V18.2.2, TS 23.502 V18.2.0, and TS 29.510 V18.3.0. For PDU session establishment with S2b WiFi access, there may be the following WiFi deployments which are desired in the commercial operator networks.• Deployment 1 : A UE connects to a local wireless AP, and the local wireless AP connects to a local ePDG and a local SMF. Then the SMF may need to select a UPF close to the ePDG. This can achieve the shortest transfer path for the user plane traffic and bandwidth saving, by comparing to selecting a UPF based on the UE's location.For example: A UE staying in NewYork may establish a WiFi PDU session. In this case, the UE terminal connects to a wireless AP in NewYork, and the wireless AP in NewYork connects to an ePDG and an SMF in NewYork. Then the SMF may need to select a UPF close to the ePDG (e.g., in NewYork).• Deployment 2: A visited UE connects to a local wireless AP, and the local wireless AP connects to an ePDG and an SMF in the UE's home network. Then the SMF may need to select a UPF close to the ePDG, instead of selecting a UPF close to the UE's location. This can achieve the shortest transfer path for the user plane traffic and bandwidth saving.For example: A UE from NewYork may visit Paris and establish a WiFi PDU session. In this case, the UEterminal connects to a wireless AP in Paris, and the wireless AP in Paris connects to an ePDG and an SMF in NewYork. Then the SMF may need to select a UPF close to the ePDG (e.g., in NewYork). If the SMF selects a UPF close to the UE's location (e.g., in Paris), the selection may be failed (since the SMF in NewYork may not be able to control the UPF in Paris), or the selection may succeed but the transfer path for the user plane traffic may be unnecessarily long and waste the bandwidth.

[0056] For the UE in the home network (Deployment 1), the UE's location is not available, because the UE's location is not present in a create session request and the information such as "UE Local IP Address” and / or "UE UDP Port” in the create session request is not able to reflect the UE's location. In this case, it may be optimal that the SMF can select the UPF close to the currently used ePDG.

[0057] For the UE is in the visited network (Deployment 2) and home routed to the ePDG / SMF of the home network, the UE's location cannot be used and also is not available (because the UE's location is not present in a create session request and the information such as "UE Local IP Address” and / or "UE UDP Port” in the create session request is not able to reflect the UE's location). In this case, it may be optimal that the SMF can select the UPF close to the currently used ePDG.

[0058] In general, it may be optimal for the real network (e.g., in Deployment 1 , Deployment 2 or any other possible deployments) that an SMF can select a UPF based on the currently used ePDG. The same conclusion may be applied for other access types such as non-3GPP access, e.g., it may be optimal that an SMF can select a UPF close to the currently used WAGF / TNGF / TWIF. However, the existing solutions may not support such UPF selection, e.g., due to the following problems:• Problem 1 : For PDU session establishment with S2b wifi access, the SMF may not be able to select a UPF based on the available ePDG information (e.g., close to the ePDG, selecting one prioritized ePDG, selecting one dedicated ePDG, etc.).• Problem 2: For PDU session establishment with wireline access by a WAGF, the SMF may not be able to select a UPF based on the available WAGF information (e.g., close to the WAGF, selecting one prioritized WAGF, selecting one dedicated WAGF, etc.).NOTE 1 : The TAI in UElocation is a configured value for the WAGF, and the initial purpose for "TAI” is not used to reflect the location (it is used for slice differentiation) and also not accurate due to the configured value.NOTE 2: According to 3GPP TS 29.510 V18.3.0, upflnfo has wagfinfo that is only for the WAGF collocated with the UPF, while in the commercial deployment, there may be a WAGF which is not collocated with the UPF.• Problem 3: For PDU session establishment with trusted non-3GPP access by a TNGF, the SMF may not be able to select a UPF based on the available TNGF information (e.g., close to the TNGF, selecting one prioritized TNGF, selecting one dedicated TNGF, etc.).NOTE: According to 3GPP TS 29.510 V18.3.0, upflnfo has tngfinfo that is only for the TNGF collocated with the UPF, while in the commercial deployment, there may be a TNGF which is not collocated with the UPF.• Problem 4: For PDU session establishment with trusted WLAN access by a TWIF, the SMF may not be able to select a UPF based on the available TWIF information (e.g., close to the TWIF, selecting one prioritized TWIF, selecting one dedicated TWIF, etc.).NOTE: According to 3GPP TS 29.510 V18.3.0, upflnfo has twifinfo that is only for the TWIF collocated with the UPF, while in the commercial deployment, there may be a TWIF which is not collocated with the UPF.

[0059] In order to address one or more problems mentioned above, various exemplary embodiments of the present disclosure propose solutions to enable an SMF to select a UPF based on information related to an ATIG such as ePDG WAGF / TNGF / GWIF. In accordance with an exemplary embodiment, when a UPF starts to work, the UPF may perform the NRF registration (e.g., to an NRF) by including one or more of the following new lEs:• "preferred Epdg Info”: the UPF may register to the NRF with upflnfo including preferred Epdg Info, which may indicate the "one or more preferred ePDGs for this UPF”. In an embodiment, the preference criteria may be "ePDG(s) close to the UPF, prioritized ePDG(s), and / or dedicated ePDG(s), etc.”.• "preferredWagflnfo”: the UPF may register to the NRF with upflnfo including preferredWagflnfo, which may indicate the "one or more preferred WAGFs for this UPF”. In an embodiment, the preference criteria may be "WAGF(s) close to the UPF, prioritized WAGF(s), and / or dedicated WAGF(s), etc.”.• "preferredTngflnfo”: the UPF may register to the NRF with upflnfo including preferredTngflnfo, which may indicate the "one or more preferred TNGFs for this UPF”. In an embodiment, the preference criteria may be "TNGF(s) close to the UPF, prioritized TNGF(s), and / or dedicated TNGF(s), etc.”.• "preferredTwiflnfo”: the UPF may register to the NRF with upflnfo including preferredTwiflnfo, which may indicate the "one or more preferred TWIFs for this UPF”. In an embodiment, the preference criteria may be "TWIF(s) close to the UPF, prioritized TWIF(s), and / or dedicated TWIF(s), etc.”.

[0060] In accordance with an exemplary embodiment, during a PDU session establishment procedure, the SMF may perform NRF discovery for UPF by including a query parameter with one of the new lEs:• "preferredEpdglnfo”: indicating an ePDG (e.g., the currently used ePDG, etc.);• "preferred agfl nfo”: indicating a WAGF (e.g., the currently used WAGF, etc.);• "preferredTngflnfo”: indicating a TNGF (e.g., the currently used TNGF, etc.);• "preferredTwiflnfo”: indicating a TWIF (e.g., the currently used TWIF, etc.).

[0061] In accordance with an exemplary embodiment, the NRF can return a UPF list in which each UPF has ATIG preference information (e.g., “preferredEpdglnfo”, "preferred Wagfl nfo”, “preferredTngflnfo”, “preferredTwiflnfo”, etc.) matched with the query parameter provided by the SMF. Then the SMF can select from the UPF list a UPF which is preferred by the currently used ATIG such as ePDG / WAGF / TNGF / GWIF, e.g., a UPF close to the ATIG. This can achieve the shortest transfer path for the user plane traffic and bandwidth saving.

[0062] According to the proposed solutions of the present disclosure, some attributes or IPs may be defined to provide more information about a UPF (e.g., the preference information of the UPF with respect to a network node such as an ATIG), and / or node information (e.g., address information of the ATIG such as ePDG / WAGF / TNGF / GWIF, etc.). In accordance with exemplary embodiments, an exemplary definition of type Upflnfo is shown in Table 7, and an exemplary definition of type Nodeinfo is shown in Table 8.Table 7Table 8

[0063] In accordance with exemplary embodiments, one or more uniform resource identifier (URI) query parameters supported by the GET method on this resource, as shown in Table 9, may be used to query and find a UPF which is preferred for an ATIG.Table 9

[0064] In accordance with exemplary embodiments, some new query parameters such as preferred Epdg Info, preferred Wagfl nfo, preferredTngflnfo and preferredTwiflnfo may be introduced as features of supportedFeatures attribute used by the Nnrf_NFDiscovery service, as shown in Table 10.Table 10

[0065] It can be appreciated that the names, representations and values of the parameter / attributes used herein are exemplary, and other names, representations and values may also be used to indicate the same or similar information. It also can be appreciated that although the same name is used for first preference information (e.g.,preferredEpdgl nfo, preferred Wagfl nfo, preferredTngflnfo and preferredTwiflnfo shown in Table 7) in a UPF registration procedure and second preference information (e.g., preferredEpdgl nfo, preferred agflnfo, preferredTngflnfo and preferred? wifi nfo shown in Table 9 and Table 10) in a UPF query procedure, the first preference information may indicate one or more preferred ATIGs for a UPF while the second preference information may indicate the currently used ATIG, therefore, the first preference information and the second preference information may indicate different contents as described with respect to Tables 7-10, and also can be named differently.

[0066] According to the proposed solutions of the present disclosure, on the one hand, a UPF may register its preference information to an NRF with one or more new lEs such as “preferredEpdglnfo”, "preferredWagflnfo”, "preferredTngflnfo” and / or "preferredTwiflnfo” as described with respect to Table 7; and on the other hand, an SMF may use a query parameter or a new IE such as "preferredEpdglnfo”, "preferredWagflnfo”, "preferredTngflnfo” or "preferredTwiflnfo” as described with respect to Tables 9-10 to query a UPF list from the NRF by performing NRF discovery for UPF. For each UPF in the UPF list returned by the NRF, its preferred ATIG such as ePDG / WAGF / TNGF / GWIF can correspond to the ATIG such as ePDG / WAGF / TNGF / GWIF indicated by the query parameter, and the SMF can select from the UPF list a preferred UPF for the indicated ATIG. The UPF selection may be based on different requirements on network services and configurations, e.g., transmission performance and resource efficiency.

[0067] Many advantages may be achieved by applying the proposed solutions. For example, the proposed solutions can enable the optimized UPF selection by an SMF for various network access types, e.g., s2b WiFi access, WAGF wireline access, TNGF non-3GPP access, TWIF trusted WLAN access, etc. According to different preference criteria, the SMF can select a UPF preferred for an ATIG (e.g., a UPF close to the currently used ePDG / WAGF / TNGF / TWIF, etc.), so as to optimize transfer path configuration (e.g., achieving the shortest transfer path for the user plane traffic, etc.) and reduce consumption of resources in time / frequency / code domain (e.g., saving transmission bandwidth and / or time, etc.).Figure 2

[0068] Fig .2 A is a diagram illustrating an exemplary UPF selection procedure according to an embodiment of the present disclosure. As shown in Fig.2A, based on the "preferredEpdglnfo” IE for a PDU session of a UE with ePDG s2b WiFi access, the UPF selection procedure may be performed with the following steps:Step 1 : When a UPF starts to work, the UPF may perform the NRF registration by sending an NRF Register Request {nflnstancelD, NFProfile (upflnfo (preferredEpdglnfo)} to an NRF."preferredEpdglnfo”: the UPF may register to the NRF with upflnfo including the new IE "preferredEpdglnfo”, which may indicate the "preferred ePDG(s) for this UPF”. The preference criteria may be "ePDG(s) close to the UPF, prioritized ePDG(s), and / or dedicated ePDG(s), etc”.The "preferredEpdglnfo” IE may include one or more of the following addressing parameters:Ipv4address: the endpoint IPv4 address(es) of a node (e.g., an ePDG).• Ipv6address: the endpoint IPv6 address(es) of a node (e.g., an ePDG).• endpointFqdn: available endpoint FQDN of a node (e.g., an ePDG).Step 2: The NRF may send an NRF Register Response {201 Created, NFProfile (upflnfo (preferredEpdglnfo)} to the UPF.Step 3: The UE may initiate a PDU session establishment procedure, and the currently used ePDG may send a Create Session Request {(Sender F-TEID for Control Plane (ePDG IP address)}to an SMF.Step 4: During the PDU session establishment procedure, the SMF may need to select a UFP for the currently used ePDG, e.g., a UPF close to the ePDG.Step 5: The SMF may perform NRF discovery for UPF by including a query parameter with the "preferredEpdglnfo” IE and sending a message of NRF Discovery for UPF {Query parameters: preferredEpdglnfo (ePDG IP address or local configured ePDG FQDN)} to the NRF.Since the ePDG IP address (e.g., Sender F-TEID for Control Plane) is mandatory in the Create Session Request, the SMF can use the ePDG IP address received from the ePDG as the query parameter to perform NRF discovery for UPF selection.In an embodiment, the SMF can include the ePDG FQDN if there is local configuration for FQDN mapping with the received ePDG IP address.Step 6: The NRF may find one or more UPFs for which upflnfo\preferredEpdglnfo can match with the query parameter "preferredEpdglnfo (ePDG IP address or FQDN), and the NRF can return the matched UPFs list to the SMF.Step 7: The NRF may send 200 OK (Search Result: UPF lists) to the SMF.Step 8: Among the returned UPF list, the SMF may select a UPF which is preferred by the currently used ePDG (e.g., a UPF close to the currently used ePDG, etc.).Step 9: Continue the PDU session establishment procedure.Figure 2B

[0069] Fig.2B is a diagram illustrating an exemplary UPF selection procedure according to anotherembodiment of the present disclosure. As shown in Fig.2B, based on the "preferred Wagfl nfo” IE for a PDU session of a UE with WAGF wireline access, the UPF selection procedure may be performed with the following steps:Step 1 : When a UPF starts to work, the UPF may perform the NRF registration by sending an NRF Register Request {nflnstancelD, NFProfile (upflnfo (preferred Wagfl nfo)} to an NRF."preferred Wagfl nfo”: the UPF may register to the NRF with upflnfo including the new IE "preferredWagflnfo”, which may indicate the "preferred WAGF(s) for this UPF”. The preference criteria may be "WAGF(s) close to the UPF, prioritized WAGF(s), and / or dedicated WAGF(s), etc.”.The "preferredWagflnfo” IE may include one or more of the following addressing parameters:• Ipv4address: available endpoint IPv4 address(es) of the N3 terminations.• Ipv6address: available endpoint IPv6 address(es) of the N3 terminations.• endpointFqdn: available endpoint FQDN of the N3 terminations.NOTE: Node IP address and / or Node FQDN can be used.Step 2: The NRF may send an NRF Register Response {201 Created, NFProfile (upflnfo (preferredWagflnfo)} to the UPF.Step3: The UE may initiate a PDU session establishment procedure, and an AMF may send an Nsmf_PDUSession_CreateSMContext Request (SmContextCreateData\wAgflnfo) to an SMF.Step 4: The SMF may send an Nsmf_PDUSession_CreateSMContext Response to the AMF.Step 5: During the PDU session establishment procedure, the SMF may need to select a UFP for the currently used WAGF, e.g., a UPF close to the WAGF.Step 6: The SMF may perform NRF discovery for UPF by including a query parameter with the "preferredWagflnfo” IE and sending a message of NRF Discovery for UPF {Query parameters: preferredWagflnfo (WAGF IP address or local configured WAGF FQDN)} to the NRF.Since the "wAgflnfo (IP address / FQDN)” is conditional in the Create Request (i.e., the "wAgflnfo” IE may need to be present if received from the WAGF via the AMF, and when present, it contains information about the N3 terminations of the WAGF), the SMF can use the "wAgflnfo” received from the AMF as the query parameter to perform NRF discovery for UPF selection.Step 7: The NRF may find one or more UPFs for which upflnfo\preferred Wagflnfo can match with the query parameter "preferredWagflnfo (WAGF IP address or FQDN)”, and the NRF can return the matched UPFslist to the SMF.Step 8: The NRF may send 200 OK (Search Result: UPF lists) to the SMF.Step 9: Among the returned UPF list, the SMF may select a UPF which is preferred by the currently used WAGF (e.g., a UPF close to the currently used WAGF, etc.).Step 10: Continue the PDU session establishment procedure.

[0070] It can be appreciated that the UPF selection procedures as illustrated in Fig.2A and Fig.2B may be similarly applied for use cases with TNGF non-3GPP access or with TWIF trusted WLAN access. In accordance with an exemplary embodiment, a UPF selection procedure based on the “preferredTngfflnfo” IE for a PDU session with TNGF non-3GPP access may include the following parts:Part 1 : When a UPF starts to work, the UPF may perform the NRF registration by including the following new IE, e.g. in an NRF Register Request to an NRF:"preferredTngflnfo”: the UPF may register to the NRF with upflnfo including “preferredTngflnfo”, which may indicate the "preferred TNGF(s) for this UPF”. The preference criteria may be "TNGF(s) close to the UPF, prioritized TNGF(s), and / or dedicated TNGF(s), etc.”.The "preferredTngflnfo” IE may include one or more of the following addressing parameters:• Ipv4address: available endpoint IPv4 address(es) of the N3 terminations.• Ipv6adress: available endpoint IPv6 address(es) of the N3 terminations.• endpointFqdn: available endpoint FQDN of the N3 terminations.NOTE: Node IP address and / or Node FQDN can be used.Part 2: During the PDU session establishment procedure, the SMF may perform NRF discovery for UPF by including a query parameter with the "preferredTngflnfo” IE.Since "tngflnfo (IP address / FQDN)” is conditional in the Create Request (i.e., the “tngflnfo” IE may need to be present if received from TNGF via an AMF, and when present, it contains information about the N3 terminations of the TNGF), the SMF can use the "tngflnfo” received from the AMF as the query parameter to perform NRF discovery for UPF selection.Part 3: The NRF may find one or more UPFs for which upflnfoXpreferredTngflnfo can match with the query parameter "preferredTngflnfo (TNGF IP address or FQDN)”, and the NRF can return the matched UPFs list to the SMF.Among the returned UPF list, the SMF may select a UPF which is preferred by the currently used TNGF (e.g., a UPF close to the currently used TNGF, etc., so as to shorten the transfer path for the user plane traffic and save bandwidth).

[0071] In accordance with another exemplary embodiment, a UPF selection procedure based on the "preferredTwiflnfo” IE for a PDU session with TWIF trusted WLAN access may include the following parts:Part 1 : When a UPF starts to work, the UPF may perform the NRF registration by including the following new IE, e.g. in an NRF Register Request to an NRF:"preferredTwiflnfo”: the UPF may register to the NRF with upflnfo including "preferredTwiflnfo”, which may indicate the "preferred TWIF(s) for this UPF”. The preference criteria may be "TWIF(s) close to the UPF, prioritized TWIF(s), dedicated TWIF(s), etc.”.The "preferredTwiflnfo” IE may include one or more of the following addressing parameters:• Ipv4address: available endpoint IPv4 address(es) of the N3 terminations.• Ipv6adress: available endpoint IPv6 address(es) of the N3 terminations.• endpointFqdn: available endpoint FQDN of the N3 terminations.NOTE: Node IP address or Node FQDN can be used.Part 2: During the PDU session establishment procedure, the SMF may perform NRF discovery for UPF by including a query parameter with the "preferredTwiflnfo” IE.Since "twiflnfo (IP address / FQDN)” is conditional in the Create Request (i.e., the “twiflnfo” IE may need to be present if received from TWIF via an AMF, and when present, it contains information about the N3 terminations of the TWIF), the SMF can use the "twiflnfo” received from the AMF as the query parameter to perform NRF discovery for UPF selection.Part 3: The NRF may find one or more UPFs for which upflnfoXpreferredTwiflnfo can match with the query parameter "preferredTwiflnfo (TWIF IP address or FQDN)”, and the NRF can return the matched UPFs list to the SMF.Among the returned UPF list, the SMF may select a UPF which is preferred by the currently used TWIF (e.g., a UPF close to the currently used TWIF, etc., so as to shorten the transfer path for the user plane traffic and save bandwidth).

[0072] It can be appreciated that network elements and signaling messages shown in Fig.2A and Fig.2B arejust as examples, and more or less alternative network elements and signaling messages may be involved in the UPF selection procedure according to various embodiments of the present disclosure.Figure 3

[0073] Fig.3 is a flowchart illustrating a method 300 according to some embodiments of the present disclosure. The method 300 illustrated in Fig.3 may be performed by a first network node or an apparatus communicatively coupled to the first network node. In accordance with an exemplary embodiment, the first network node may be configured to implement an SMF or act as any other suitable network entity which may be configured to perform session management for one or more terminal devices (e.g., UEs, etc.).

[0074] According to the exemplary method 300 illustrated in Fig.3, the first network node may transmit first information (e.g., the lEs “preferredEpdglnfo”, "preferredWagflnfo”, "preferredTngflnfo” or "preferredTwiflnfo” as described with respect to Table 9 and Table 10) indicating an ATIG towards a second network node (e.g., an NRF, etc.), as shown in block 302. In accordance with an exemplary embodiment, the first network node may receive a list of UPFs transmitted by the second network node, as shown in block 304. The ATIG indicated by the first information may be preferred for each of the list of the UPFs according to second information per UPF (e.g., the lEs "preferredEpdglnfo”, "preferredWagflnfo”, "preferredTngflnfo” and / or "preferredTwiflnfo” as described with respect to Table 7) registered at the second network node. The second information per UPF may indicate one or more preferred ATIGs for the UPF. In accordance with an exemplary embodiment, the first network node may select a UPF preferred for the ATIG from the list of the UPFs, as shown in block 306. In an embodiment, the selected UPF may be a UPF close to the ATIG.

[0075] In accordance with an exemplary embodiment, the first information may comprise available endpoint address information (e.g., IPv4 / IPv6 address information, etc.) and / or available endpoint FQDN information of the ATIG. In accordance with another exemplary embodiment, the second information per UPF may comprise available endpoint address information (e.g., IPv4 / IPv6 address information, etc.) and / or available endpoint FQDN information of the one or more preferred ATIGs for the UPF.

[0076] In accordance with an exemplary embodiment, the one or more preferred ATIGs for the UPF may include: one or more ATIGs close to the UPF; and / or one or more ATIGs prioritized for the UPF; and / or one or more ATIGs dedicated to the UPF. In an embodiment, the ATIG may be any of an ePDG, a WAGF, a TNGF, a TWIF or a similar network entity.Figure 4

[0077] Fig.4 is a flowchart illustrating a method 400 according to some embodiments of the present disclosure. The method 400 illustrated in Fig.4 may be performed by a second network node or an apparatus communicatively coupled to the second network node. In accordance with an exemplary embodiment, the second network node may beconfigured to implement an NRF or act as any other suitable network entity which may be configured to store registration information and / or profiles of one or more NFs.

[0078] According to the exemplary method 400 illustrated in Fig.4, the second network node may receive first information indicating an ATIG transmitted by a first network node (e.g., the first network node as described with respect to Fig.3), as shown in block 402. In accordance with an exemplary embodiment, the second network node may determine a list of UPFs according to the first information and second information per UPF registered at the second network node, as shown in block 404. The second information per UPF may indicate one or more preferred ATIGs (e.g., ePDGs, WAGFs, TNGFs and / or TWIFs, etc.) for the UPF. The ATIG indicated by the first information may be preferred for each of the list of the UPFs. In accordance with an exemplary embodiment, the second network node may transmit the list of the UPFs towards the first network node, as shown in block 406.

[0079] In accordance with an exemplary embodiment, the first information received by the second network node according to the method 400 may correspond to the first information transmitted by the first network node according to the method 300. Thus, the first information as described with respect to Fig.3 and Fig.4 may have the same or similar contents and / or feature elements. Similarly, the second information as described with respect to Fig.3 and Fig.4 may have the same or similar contents and / or feature elements.

[0080] In accordance with an exemplary embodiment, the list of the UPFs transmitted by the second network node according to the method 400 may correspond to the list of the UPFs received by the first network node according to the method 300. Thus, the list of the UPFs as described with respect to Fig.3 and Fig.4 may have the same or similar contents and / or feature elements.

[0081] In accordance with an exemplary embodiment, the second network node may obtain the second information per UPF by receiving a register request for a corresponding UPF transmitted by a third network node (e.g., a UPF, etc.). In an embodiment, the register request may include the second information of the corresponding UPF.

[0082] In accordance with another exemplary embodiment, the second network node may transmit a register response towards the third network node. In an embodiment, the register response may indicate a profile with the second information of the corresponding UPF.Figure 5

[0083] Fig.5 is a flowchart illustrating a method 500 according to some embodiments of the present disclosure. The method 500 illustrated in Fig.5 may be performed by a third network node or an apparatus communicatively coupled to the third network node. In accordance with an exemplary embodiment, the third network node may be configured to implement a UPF or act as any other suitable network entity which may be configured to provide a user plane service.

[0084] According to the exemplary method 500 illustrated in Fig.5, the third network node may determine second information of a UPF, as shown in block 502. The second information of the UPF may indicate one or more preferred ATIGs (e.g., ePDGs, WAGFs, TNGFs and / or TWIFs, etc.) for the UPF. In accordance with an exemplary embodiment, the third network node may transmit a register request for the UPF towards a second network node (e.g., the second network node as described with respect to Fig.4), as shown in block 504. In an embodiment, the register request may include the second information of the UPF.

[0085] In accordance with an exemplary embodiment, the second information according to the method 500 may correspond to the second information according to the method 300 and the method 400. Thus, the second information as described with respect to Fig.3, Fig.4 and Fig.5 may have the same or similar contents and / or feature elements. Similarly, the one or more preferred ATIGs for the UPF indicated by the second information of the UPF as described with respect to Fig.3, Fig.4 and Fig.5 may refer to the same or similar functional elements and / or network entities.

[0086] In accordance with an exemplary embodiment, the third network node may receive a register response transmitted by the second network node. The register response may indicate a profile with the second information of the UPF.

[0087] The various blocks shown in Figs.3-5 may be viewed as method steps, and / or as operations that result from operation of computer program code, and / or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). The schematic flow chart diagrams described above are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of specific embodiments of the presented methods. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated methods. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown.

[0088] It can be appreciated that the network node according to various embodiments can be implemented either as a network element and / or a network entity on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g., on a cloud infrastructure.Figure 6

[0089] Fig.6 is a block diagram illustrating an apparatus 600 according to various embodiments of the present disclosure. As shown in Fig.6, the apparatus 600 may comprise one or more processors such as processor 601 and one or more memories such as memory 602 storing computer program codes 603. The memory 602 may be non- transitory machine / processor / computer readable storage medium. In accordance with some exemplary embodiments, the apparatus 600 may be implemented as an integrated circuit chip or module that can be plugged or installed into a first network node as described with respect to Fig.3, or a second network node as described with respect to Fig.4, or a third network node as described with respect to Fig.5. In such cases, the apparatus 600 may be implemented as afirst network node as described with respect to Fig.3, or a second network node as described with respect to Fig.4, or a third network node as described with respect to Fig.5.

[0090] In some implementations, the one or more memories 602 and the computer program codes 603 may be configured to, with the one or more processors 601 , cause the apparatus 600 at least to perform any operation of the method as described in connection with Fig.3. In other implementations, the one or more memories 602 and the computer program codes 603 may be configured to, with the one or more processors 601 , cause the apparatus 600 at least to perform any operation of the method as described in connection with Fig.4. In other implementations, the one or more memories 602 and the computer program codes 603 may be configured to, with the one or more processors 601 , cause the apparatus 600 at least to perform any operation of the method as described in connection with Fig.5. Alternatively or additionally, the one or more memories 602 and the computer program codes 603 may be configured to, with the one or more processors 601 , cause the apparatus 600 at least to perform more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.Figure 7A

[0091] Fig.7A is a block diagram illustrating an apparatus 710 according to some embodiments of the present disclosure. As shown in Fig.7A, the apparatus 710 may comprise a transmitting unit 711 , a receiving unit 712 and a selecting unit 713. In an exemplary embodiment, the apparatus 710 may be implemented in a first network node (e.g., an SMF, etc.). The transmitting unit 711 may be operable to carry out the operation in block 302, the receiving unit 712 may be operable to carry out the operation in block 304, and the selecting unit 713 may be operable to carry out the operation in block 306. Optionally, the transmitting unit 711 and / or the receiving unit 712 and / or the selecting unit 713 may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.Figure 7B

[0092] Fig .7B is a block diagram illustrating an apparatus 720 according to some embodiments of the present disclosure. As shown in Fig.7B, the apparatus 720 may comprise a receiving unit 721 , a determining unit 722 and a transmitting unit 723. In an exemplary embodiment, the apparatus 720 may be implemented in a second network node (e.g., an NRF, etc.). The receiving unit 721 may be operable to carry out the operation in block 402, the determining unit 722 may be operable to carry out the operation in block 404, and the transmitting unit 723 may be operable to carry out the operation in block 406. Optionally, the receiving unit 721 and / or the determining unit 722 and / or the transmitting unit 723 may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.Figure 7C

[0093] Fig.7C is a block diagram illustrating an apparatus 730 according to some embodiments of the presentdisclosure. As shown in Fig.7C, the apparatus 730 may comprise a determining unit 731 and a transmitting unit 732. In an exemplary embodiment, the apparatus 730 may be implemented in a third network node (e.g., a UPF, etc.). The determining unit 731 may be operable to carry out the operation in block 502, and the transmitting unit 732 may be operable to carry out the operation in block 504. Optionally, the determining unit 731 and / or the transmitting unit 732 may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.Some Embodiments

[0094] Some of the embodiments that have been described above may be summarized in the following manner:1 . A method (300) performed by a first network node, comprising: transmitting (302) first information indicating an access type interworking gateway, ATIG, towards a second network node; receiving (304) a list of user plane functions, UPFs, transmitted by the second network node, wherein the ATIG indicated by the first information is preferred for each of the list of the UPFs according to second information per UPF registered at the second network node, the second information per UPF indicating one or more preferred ATIGs for the UPF; and selecting (306) a UPF preferred for the ATIG from the list of the UPFs.2. The method according to embodiment 1 , wherein the first information comprises available endpoint address information and / or available endpoint fully qualified domain name, FQDN, information of the ATIG.3. The method according to embodiment 1 or 2, wherein the second information per UPF comprises available endpoint address information and / or available endpoint FQDN information of the one or more preferred ATIGs for the UPF.4. The method according to any of embodiments 1 -3, wherein the one or more preferred ATIGs for the UPF include: one or more ATIGs close to the UPF; and / or one or more ATIGs prioritized for the UPF; and / or one or more ATIGs dedicated to the UPF.5. The method according to any of embodiments 1-4, wherein the ATIG is an evolved packet data gateway, ePDG; or a wireline access gateway function, WAGF; or a trusted non-3GPP gateway function, TNGF; or a trusted wide local area network interworking function, TWIF.6. The method according to any of embodiments 1-5, wherein the selected UPF is a UPF close to the ATIG.7. The method according to any of embodiments 1-6, wherein the first network node is configured to implement a session management function, SMF; and / or the second network node is configured to implement a network-function repository function, NRF.8. A first network node (600), comprising: one or more processors (601); and one or more memories (602) comprising computer program codes (603), the one or more memories (602) and the computer program codes (603) configured to, with the one or more processors (601), cause the first network node (600) at least to: transmit first information indicating an access type interworking gateway, ATIG, towards a second network node; receive a list of user plane functions, UPFs, transmitted by the second network node, wherein the ATIG indicated by the first information is preferred for each of the list of the UPFs according to second information per UPF registered at the second network node, the second information per UPF indicating one or more preferred ATIGs for the UPF; and select a UPF preferred for the ATIG from the list of the UPFs.9. The first network node according to embodiment 8, wherein the one or more memories and the computer program codes are configured to, with the one or more processors, cause the first network node to perform the method according to any one of embodiments 2-7.10. A computer-readable medium having computer program codes (603) embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to any one of embodiments 1-7.11. A method (400) performed by a second network node, comprising: receiving (402) first information indicating an access type interworking gateway, ATIG, transmitted by a first network node; determining (404) a list of user plane functions, UPFs, according to the first information and second information per UPF registered at the second network node, wherein the second information per UPF indicates one or more preferred ATIGs for the UPF, and the ATIG indicated by the first information is preferred for each of the list of the UPFs; and transmitting (406) the list of the UPFs towards the first network node.12. The method according to embodiment 11 , wherein the first information comprises available endpoint address information and / or available endpoint fully qualified domain name, FQDN, information of the ATIG.13. The method according to embodiment 11 or 12, wherein the second information per UPF comprises availableendpoint address information and / or available endpoint FQDN information of the one or more preferred ATIGs for the UPF.14. The method according to any of embodiments 11-13, wherein the one or more preferred ATIGs for the UPF include: one or more ATIGs close to the UPF; and / or one or more ATIGs prioritized for the UPF; and / or one or more ATIGs dedicated to the UPF.15. The method according to any of embodiments 11-14, wherein the ATIG is an evolved packet data gateway, ePDG; or a wireline access gateway function, WAGF; or a trusted non-3GPP gateway function, TNGF; or a trusted wide local area network interworking function, TWIF.16. The method according to any of embodiments 11-15, further comprising: obtaining the second information per UPF by receiving a register request for a corresponding UPF transmitted by a third network node, wherein the register request includes the second information of the corresponding UPF.17. The method according to embodiment 16, further comprising: transmitting a register response towards the third network node, wherein the register response indicates a profile with the second information of the corresponding UPF.18. The method according to embodiment 16 or 17, wherein the third network node is configured to implement the corresponding UPF.19. The method according to any of embodiments 11-18, wherein the first network node is configured to implement a session management function, SMF; and / or the second network node is configured to implement a network -function repository function, NRF.20. A second network node (600), comprising: one or more processors (601); and one or more memories (602) comprising computer program codes (603), the one or more memories (602) and the computer program codes (603) configured to, with the one or more processors (601), cause the second network node (600) at least to: receive first information indicating an access type interworking gateway, ATIG, transmitted by a first network node;determine a list of user plane functions, UPFs, according to the first information and second information per UPF registered at the second network node, wherein the second information per UPF indicates one or more preferred ATIGs for the UPF, and the ATIG indicated by the first information is preferred for each of the list of the UPFs; and transmit the list of the UPFs towards the first network node.21 . The second network node according to embodiment 20, wherein the one or more memories and the computer program codes are configured to, with the one or more processors, cause the second network node to perform the method according to any one of embodiments 12-19.22. A computer-readable medium having computer program codes (603) embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to any one of embodiments 11-19.23. A method (500) performed by a third network node, comprising: determining (502) second information of a user plane function, UPF, wherein the second information of the UPF indicates one or more preferred access type interworking gateways, ATIGs, for the UPF; and transmitting (504) a register request for the UPF towards a second network node, wherein the register request includes the second information of the UPF.24. The method according to embodiment 23, wherein the second information of the UPF comprises available endpoint address information and / or available endpoint fully qualified domain name, FQDN, information of the one or more preferred ATIGs for the UPF.25. The method according to embodiment 23 or 24, wherein the one or more preferred ATIGs for the UPF include: one or more ATIGs close to the UPF; and / or one or more ATIGs prioritized for the UPF; and / or one or more ATIGs dedicated to the UPF.26. The method according to any of embodiments 23-25, wherein the ATIG is an evolved packet data gateway, ePDG; or a wireline access gateway function, WAGF; or a trusted non-3GPP gateway function, TNGF; or a trusted wide local area network interworking function, TWIF.27. The method according to any of embodiments 23-26, further comprising: receiving a register response transmitted by the second network node, wherein the register response indicates a profile with the second information of the UPF.28. The method according to any of embodiments 23-27, wherein the second network node is configured toimplement a network-function repository function, NRF; and / or the third network node is configured to implement the UPF.29. A third network node (600), comprising: one or more processors (601); and one or more memories (602) comprising computer program codes (603), the one or more memories (602) and the computer program codes (603) configured to, with the one or more processors (601), cause the third network node (600) at least to: determine second information of a user plane function, UPF, wherein the second information of the UPF indicates one or more preferred access type interworking gateways, ATIGs, for the UPF; and transmit a register request for the UPF towards a second network node, wherein the register request includes the second information of the UPF.30. The third network node according to embodiment 29, wherein the one or more memories and the computer program codes are configured to, with the one or more processors, cause the third network node to perform the method according to any one of embodiments 24-28.31 . A computer-readable medium having computer program codes (603) embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to any one of embodiments 23-28.

[0095] In general, the various exemplary embodiments may be implemented in hardware or special purpose chips, circuits, software, logic or any combination thereof. For example, some aspects 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 disclosure is not limited thereto. While various aspects of the exemplary embodiments of this disclosure 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.

[0096] As such, it should be appreciated that at least some aspects of the exemplary embodiments of the disclosure may be practiced in various components such as integrated circuit chips and modules. It should thus be appreciated that the exemplary embodiments of this disclosure may be realized in an apparatus that is embodied as an integrated circuit, where the integrated circuit may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor, a digital signal processor, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this disclosure.

[0097] It should be appreciated that at least some aspects of the exemplary embodiments of the disclosure may be embodied in computer-executable instructions, such as in one or more program modules, executed by one ormore computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types when executed by a processor in a computer or other device. The computer executable instructions may be stored on a computer readable medium such as a hard disk, optical disk, removable storage media, solid state memory, random access memory (RAM), etc. As will be appreciated by one of skill in the art, the function of the program modules may be combined or distributed as desired in various embodiments. In addition, the function may be embodied in whole or partly in firmware or hardware equivalents such as integrated circuits, field programmable gate arrays (FPGA), and the like.

[0098] The present disclosure includes any novel feature or combination of features disclosed herein either explicitly or any generalization thereof. Various modifications and adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this disclosure.

Claims

CLAIMSWhat is claimed is:1 . A method (300) performed by a first network node, comprising: transmitting (302) first information indicating an access type interworking gateway, ATIG, towards a second network node; receiving (304) a list of user plane functions, UPFs, transmitted by the second network node, wherein the ATIG indicated by the first information is preferred for each of the list of the UPFs according to second information per UPF registered at the second network node, the second information per UPF indicating one or more preferred ATIGs for the UPF; and selecting (306) a UPF preferred for the ATIG from the list of the UPFs.

2. The method according to claim 1 , wherein the first information comprises available endpoint address information and / or available endpoint fully qualified domain name, FQDN, information of the ATIG.

3. The method according to claim 1 or 2, wherein the second information per UPF comprises available endpoint address information and / or available endpoint FQDN information of the one or more preferred ATIGs for the UPF.

4. The method according to any of claims 1 -3, wherein the one or more preferred ATIGs for the UPF include: one or more ATIGs close to the UPF; and / or one or more ATIGs prioritized for the UPF; and / or one or more ATIGs dedicated to the UPF.

5. The method according to any of claims 1-4, wherein the ATIG is an evolved packet data gateway, ePDG; or a wireline access gateway function, WAGF; or a trusted non-3GPP gateway function, TNGF; or a trusted wide local area network interworking function, TWIF.

6. The method according to any of claims 1-5, wherein the selected UPF is a UPF close to the ATIG.

7. The method according to any of claims 1 -6, wherein the first network node is configured to implement a session management function, SMF; and / or the second network node is configured to implement a network -function repository function, NRF.

8. A first network node (600), comprising: one or more processors (601); and one or more memories (602) comprising computer program codes (603), the one or more memories (602) and the computer program codes (603) configured to, with the one or more processors (601), cause the first network node (600) at least to: transmit first information indicating an access type interworking gateway, ATIG, towards a second network node; receive a list of user plane functions, UPFs, transmitted by the second network node, wherein the ATIG indicated by the first information is preferred for each of the list of the UPFs according to second information per UPF registered at the second network node, the second information per UPF indicating one or more preferred ATIGs for the UPF; and select a UPF preferred for the ATIG from the list of the UPFs.

9. The first network node according to claim 8, wherein the one or more memories and the computer program codes are configured to, with the one or more processors, cause the first network node to perform the method according to any one of claims 2-7.

10. A computer-readable medium having computer program codes (603) embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to any one of claims 1 -7.

11. A method (400) performed by a second network node, comprising: receiving (402) first information indicating an access type interworking gateway, ATIG, transmitted by a first network node; determining (404) a list of user plane functions, UPFs, according to the first information and second information per UPF registered at the second network node, wherein the second information per UPF indicates one or more preferred ATIGs for the UPF, and the ATIG indicated by the first information is preferred for each of the list of the UPFs; and transmitting (406) the list of the UPFs towards the first network node.

12. The method according to claim 11 , wherein the first information comprises available endpoint address information and / or available endpoint fully qualified domain name, FQDN, information of the ATIG.

13. The method according to claim 11 or 12, wherein the second information per UPF comprises available endpoint address information and / or available endpoint FQDN information of the one or more preferred ATIGs for the UPF.

14. The method according to any of claims 11 -13, wherein the one or more preferred ATIGs for the UPF include: one or more ATIGs close to the UPF; and / or one or more ATIGs prioritized for the UPF; and / or one or more ATIGs dedicated to the UPF.

15. The method according to any of claims 11 -14, wherein the ATIG is an evolved packet data gateway, ePDG; or a wireline access gateway function, WAGF; or a trusted non-3GPP gateway function, TNGF; or a trusted wide local area network interworking function, TWIF.

16. The method according to any of claims 11 -15, further comprising: obtaining the second information per UPF by receiving a register request for a corresponding UPF transmitted by a third network node, wherein the register request includes the second information of the corresponding UPF.

17. The method according to claim 16, further comprising: transmitting a register response towards the third network node, wherein the register response indicates a profile with the second information of the corresponding UPF.

18. The method according to claim 16 or 17, wherein the third network node is configured to implement the corresponding UPF.

19. The method according to any of claims 11 -18, wherein the first network node is configured to implement a session management function, SMF; and / or the second network node is configured to implement a network -function repository function, NRF.

20. A second network node (600), comprising: one or more processors (601); and one or more memories (602) comprising computer program codes (603), the one or more memories (602) and the computer program codes (603) configured to, with the one or more processors (601), cause the second network node (600) at least to: receive first information indicating an access type interworking gateway, ATIG, transmitted by a first network node; determine a list of user plane functions, UPFs, according to the first information and second information per UPF registered at the second network node, wherein the second information per UPF indicates one or more preferred ATIGs for the UPF, and the ATIG indicated by the first information is preferred for each of the list of the UPFs; and transmit the list of the UPFs towards the first network node.21 . The second network node according to claim 20, wherein the one or more memories and the computer program codes are configured to, with the one or more processors, cause the second network node to perform the method according to any one of claims 12-19.

22. A computer-readable medium having computer program codes (603) embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to any one of claims 11 -19.

23. A method (500) performed by a third network node, comprising: determining (502) second information of a user plane function, UPF, wherein the second information of the UPF indicates one or more preferred access type interworking gateways, ATIGs, for the UPF; and transmitting (504) a register request for the UPF towards a second network node, wherein the register request includes the second information of the UPF.

24. The method according to claim 23, wherein the second information of the UPF comprises available endpoint address information and / or available endpoint fully qualified domain name, FQDN, information of the one or more preferred ATIGs for the UPF.

25. The method according to claim 23 or 24, wherein the one or more preferred ATIGs for the UPF include: one or more ATIGs close to the UPF; and / or one or more ATIGs prioritized for the UPF; and / or one or more ATIGs dedicated to the UPF.

26. The method according to any of claims 23-25, wherein the ATIG is an evolved packet data gateway, ePDG; or a wireline access gateway function, WAGF; or a trusted non-3GPP gateway function, TNGF; or a trusted wide local area network interworking function, TWIF.

27. The method according to any of claims 23-26, further comprising: receiving a register response transmitted by the second network node, wherein the register response indicates a profile with the second information of the UPF.

28. The method according to any of claims 23-27, wherein the second network node is configured to implement a network-function repository function, NRF; and / or the third network node is configured to implement the UPF.

29. A third network node (600), comprising: one or more processors (601); and one or more memories (602) comprising computer program codes (603), the one or more memories (602) and the computer program codes (603) configured to, with the one or more processors (601), cause the third network node (600) at least to: determine second information of a user plane function, UPF, wherein the second information of the UPF indicates one or more preferred access type interworking gateways, ATIGs, for the UPF; andtransmit a register request for the UPF towards a second network node, wherein the register request includes the second information of the UPF.

30. The third network node according to claim 29, wherein the one or more memories and the computer program codes are configured to, with the one or more processors, cause the third network node to perform the method according to any one of claims 24-28.31 . A computer-readable medium having computer program codes (603) embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to any one of claims 23-28.

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