Patent Description:
In modern telecommunications networks, user equipments (UEs), such as mobile phones, tablets, laptops, etc., will typically be carried by their users to travel from one place to another, which may trigger a so called "handover" procedure. A handover procedure denotes the process in which a radio access network (RAN) changes its radio transmitters, radio access mode, or radio system, and in which a core network (CN) adjusts its configurations and re-routes data packets to/from the UE of interest, to allow the transmission of information as efficient as possible.

For example, a mobile phone user moves within his/her service provider's network, switching between cellular towers when he/she moves in and out of range of network towers, as well as when a user's device must switch technologies (from <NUM> to <NUM> or from <NUM> to <NUM>, for example) or even between operators themselves.

As one of the key requirements of a <NUM> system, data forwarding at the point of the handover helps to minimize jitter, data loss, and out-of-order delivery. In all handovers, solutions are implemented to execute the process quickly and smoothly.

For example, in a <NUM>rd Generation Partnership Project (3GPP)-compliant network, when a UE is moving from one location to another location with an active data connection (e.g. a Packet Data Network (PDN) connection / Protocol Data Unit (PDU) session), a specific tunnel for data forwarding is sometimes required to relay buffered data or subsequent data from a source cell to a target cell. In such a case, a Session Management Function (SMF) serving the UE may decide to set up an indirect forwarding tunnel between the source cell and the target cell.

Prior art examples are: <CIT>; <CIT>; <NPL>.

Therefore, according to the current 3GPP standards, it is a problem for the SMF to identify a User Plane Function (UPF) which is dedicated for the data forwarding.

The scope of the present invention is defined in the appended claims.

According to claim <NUM>, that is a first aspect of the present disclosure, a method at a first network element for facilitating data forwarding is provided. The method comprises: receiving, from a second network element, a first message comprising a first indicator indicating that a data forwarding function is supported by the second network element.

In some embodiments, the first message is a first request message which requests registering, at the first network element, one or more functions of the second network element comprising the data forwarding function. In some embodiments, the method further comprises: transmitting, to the second network element, a first response message comprising a second indicator indicating success of the registration. In some embodiments, the first network element is a Network Repository Function (NRF), and the second network element is a User Plane Function (UPF) or Serving GateWay for User plane (SGW-U). In some embodiments, the first request message is a request message for Nnrf_NFManagement service, and the first response message is a response message for Nnrf_NFManagement service. In some embodiments, the first indicator is an attribute of the data type "Upfinfo" comprised in the first request message.

In some embodiments, the method further comprises: receiving, from a third network element, a second request message comprising a third indicator indicating a query for network elements having the data forwarding function. In some embodiments, the method further comprises: transmitting, to the third network element, a second response message comprising a list of one or more fourth indicators, each of the one or more fourth indicators indicating a network element having the data forwarding function. In some embodiments, the second network element is one of the one or more network elements indicated by the one or more fourth indicators. In some embodiments, the third network element is a Session Management Function (SMF), a Mobility Management Entity (MME), or a SGW for Control plane (SGW-C). In some embodiments, the second request message is a request message for Nnrf_NFDiscovery service, and the second response message is a response message for Nnrf_NFDiscovery service. In some embodiments, the third indicator is a Uniform Resource Indicator (URI) query parameter comprised in the second request message. In some embodiments, the first message comprises one or more fifth indicators indicating one or more network instances supported by the second network element for data forwarding. In some embodiments, for each of the one or more network elements indicated by the one or more fourth indicators, the second response message comprises one or more fifth indicators indicating one or more network instances supported by the corresponding network element for data forwarding. In some embodiments, each of the fifth indicators is an attribute of the data type "Upfinfo" comprised in the first request message or in the second response message.

In some embodiments, the first message is one of: a Packet Forwarding Control Plane (PFCP) Association Setup Request message; a PFCP Association Update Request message; a PFCP Association Setup Response message in response to a PFCP Association Setup Request message previously.

transmitted from the first network element to the second network element; and a PFCP Association Update Response message in response to a PFCP Association Setup Update message previously transmitted from the first network element to the second network element. In some embodiments, the first network element is a Control Plane (CP) function, and the second network element is a User Plane (UP) function. In some embodiments, the first indicator is an information element (IE) comprised in the first message. In some embodiments, the first message comprises one or more fifth indicators indicating one or more network instances supported by the second network element for data forwarding. In some embodiments, each of the fifth indicators is an IE comprised in the first message.

In some embodiments, the first message further comprises a sixth indicator indicating a target area towards which IP connectivity is enabled by at least one of the network instances indicated by the fifth indicators. In some embodiments, the sixth indicator indicates a target area towards which IP connectivity is enabled by one of the network instances indicated by the fifth indicators. In some embodiments, the sixth indicator comprises a list of Tracking Area Information (TAI) or a list of NG-RAN IDs.

In some embodiments, the first network element is a Domain Name System (DNS) server. In some embodiments, the first message is a first request message which requests adding or updating a Name Authority PoinTeR (NAPTR) DNS record at the first network element, and the NAPTR DNS record indicates that the second network element or another network element supports the data forwarding function. In some embodiments, the method further comprises: receiving, from a third network element, a second request message comprising a third indicator indicating a query for network elements having the data forwarding function. In some embodiments, the method further comprises: transmitting, to the third network element, a second response message comprising a list of one or more fourth indicators, each of the one or more fourth indicators indicating a network element having the data forwarding function. In some embodiments, the second network element is one of the one or more network elements indicated by the one or more fourth indicators. In some embodiments, the third network element is one of an Mobility Management Entity (MME) and an SGW-C.

According to claim <NUM>, that is a second aspect of the present disclosure, a first network element is provided. The first network element comprises: a processor; a memory storing instructions which, when executed by the processor, cause the processor to perform any of the methods of the first aspect.

The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and therefore are not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.

Hereinafter, the present disclosure is described with reference to embodiments shown in the attached drawings. However, it is to be understood that those descriptions are just provided for illustrative purpose, rather than limiting the present disclosure. Further, in the following, descriptions of known structures and techniques are omitted so as not to unnecessarily obscure the concept of the present disclosure.

Those skilled in the art will appreciate that the term "exemplary" is used herein to mean "illustrative," or "serving as an example," and is not intended to imply that a particular embodiment is preferred over another or that a particular feature is essential. Likewise, the terms "first", "second", "third", "fourth", "fifth", "sixth," and similar terms, are used simply to distinguish one particular instance of an item or feature from another, and do not indicate a particular order or arrangement, unless the context clearly indicates otherwise. Further, the term "step," as used herein, is meant to be synonymous with "operation" or "action. " Any description herein of a sequence of steps does not imply that these operations must be carried out in a particular order, or even that these operations are carried out in any order at all, unless the context or the details of the described operation clearly indicates otherwise.

Conditional language used herein, such as "can," "might," "may," "e.g.," and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or states. Thus, such conditional language is not generally intended to imply that features, elements and/or states are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without author input or prompting, whether these features, elements and/or states are included or are to be performed in any particular embodiment.

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. In addition, language such as the phrase "at least one of X, Y and Z," unless specifically stated otherwise, is to be understood with the context as used in general to convey that an item, term, etc. may be either X, Y, or Z, or a combination thereof.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limitation of example embodiments. It will be also understood that the terms "connect(s)," "connecting", "connected", etc. when used herein, just mean that there is an electrical or communicative connection between two elements and they can be connected either directly or indirectly, unless explicitly stated to the contrary.

Of course, the present disclosure may be carried out in other specific ways than those set forth herein without departing from the scope and essential characteristics of the disclosure. One or more of the specific processes discussed below may be carried out in any electronic device comprising one or more appropriately configured processing circuits, which may in some embodiments be embodied in one or more application-specific integrated circuits (ASICs). In some embodiments, these processing circuits may comprise one or more microprocessors, microcontrollers, and/or digital signal processors programmed with appropriate software and/or firmware to carry out one or more of the operations described above, or variants thereof. In some embodiments, these processing circuits may comprise customized hardware to carry out one or more of the functions described above. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Although multiple embodiments of the present disclosure will be illustrated in the accompanying Drawings and described in the following Detailed Description, it should be understood that the disclosure is not limited to the disclosed embodiments, but instead is also capable of numerous rearrangements, modifications, and substitutions without departing from the present disclosure that as will be set forth and defined within the claims.

Further, please note that although the following description of some embodiments of the present disclosure is given in the context of <NUM> New Radio (NR), the present disclosure is not limited thereto. In fact, as long as data forwarding is involved, the inventive concept of the present disclosure may be applicable to any appropriate communication architecture, for example, to Global System for Mobile Communications (GSM) / General Packet Radio Service (GPRS), Enhanced Data Rates for GSM Evolution (EDGE), Code Division Multiple Access (CDMA), Wideband CDMA (WCDMA), Time Division - Synchronous CDMA (TD-SCDMA), CDMA2000, Worldwide Interoperability for Microwave Access (WiMAX), Wireless Fidelity (Wi-Fi), <NUM>th Generation Long Term Evolution (LTE), LTE-Advance (LTE-A), or 5th Generation New Radio (<NUM> NR), etc. Therefore, one skilled in the arts could readily understand that the terms used herein may also refer to their equivalents in any other infrastructure. For example, the term "User Equipment" or "UE" used herein may refer to a mobile device, a mobile terminal, a mobile station, a user device, a user terminal, a wireless device, a wireless terminal, or any other equivalents. For another example, the term "gNB" used herein may refer to a base station, a base transceiver station, an access point, a hot spot, a NodeB, an Evolved NodeB, a network element, or any other equivalents. Further, the term "network element" used herein may refer to a network function, a network entity, a node, a network equipment, or any other device on the network side. Further, please note that the term "indicator" used herein may refer to an attribute, a setting, a configuration, a profile, an identifier, a field, one or more bits/octets, or any data by which information of interest may be indicated directly or indirectly.

Further, some of the 3GPP Technical Specifications (3GPP TSs) are cited or mentioned throughout the present description in order to facilitate understanding the claimed subject matter.

The <NUM> Core Network has been designed around services that are invoked using a standard Application Programming Interface (API). On the surface, the <NUM> architecture looks very different from the <NUM> Evolved Packet Core (EPC) but on close inspection, one can see the evolution from the <NUM> architecture to the <NUM> architecture.

For example, the <NUM> core has evolved from the <NUM> EPC in two steps:.

The introduction of control and user plane separation in the <NUM> EPC is the first step towards the <NUM> architecture. The Serving GateWay (SGW) and Packet Data Network (PDN) GateWay (PGW) functions were split into a control and data plane component:.

With the separation of control and user plane functions, the split functions are reorganized into new network functions, such as Access and Mobility Function (AMF), Session Management Function (SMF), User Plane Function (UPF), etc. In general, an AMF in <NUM> provides most of the functions which were previously performed by a Mobility Management Entity (MME) in <NUM>, an SMF provides rest of the functions which were previously provided by the MME in addition to the control plane (CP) functions which were previously provided by SGW and PGW, and a UPF provides the user plane (UP) functions which were previously provided by SGW and PGW. In such a manner, the <NUM> EPC components have been reorganized into service-oriented functions. Therefore, any reference to a network function defined for <NUM> may also be applicable to a node defined for <NUM> or any other appropriate telecommunication technologies. For example, when "SMF" is recited in some embodiments, "PGW-C" or "SGW-C" may be equally applicable. For example, when "UPF" is recited in some embodiments, "PGW-U" or "SGW-U" may be equally applicable.

<FIG> is an overview diagram illustrating a typical <NUM> New Radio (NR) network architecture <NUM> according to an embodiment of the present disclosure. As shown in <FIG>, the network <NUM> may comprise one or more UEs <NUM> and a (radio) access network ((R)AN) <NUM>, which could be a base station, a Node B, an evolved NodeB (eNB), a gNB, or any entity which provides access to the UEs <NUM>. Further, the network <NUM> may comprise its core network portion comprising (but not limited to) an AMF <NUM>, an SMF <NUM>, a Policy Control Function (PCF) <NUM>, an Application Function (AF) <NUM>, a Network Slice Selection Function (NSSF) <NUM>, an AUthentication Server Function (AUSF) <NUM>, a Unified Data Management (UDM) <NUM>, a Network Exposure Function (NEF) <NUM>, a Network Repository Function (NRF) <NUM>, and one or more UPFs <NUM>. As shown in <FIG>, these entities may communicate with each other via the service-based interfaces, such as, Namf, Nsmf, Npcf, etc. and/or the reference points, such as, N1, N2, N3, N6, N9, etc..

However, the present disclosure is not limited thereto. In some other embodiments, the network <NUM> may comprise additional network functions, less network functions, or some variants of the existing network functions shown in <FIG>. For example, in a network with the <NUM> architecture, the entities which perform these functions may be different from those shown in <FIG>. For another example, in a network with a mixed <NUM>/<NUM> architecture, some of the entities may be same as those shown in <FIG>, and others may be different. Further, the functions shown in <FIG> are not essential to the embodiments of the present disclosure. In other words, some of them may be missing from some embodiments of the present disclosure.

Here, some of the functions shown in <FIG>, such as AMF <NUM>, SMF <NUM>, NRF <NUM>, UPFs <NUM>, which may be involved in the embodiments of the present disclosure will be described in detail below.

Referring to <FIG>, the AMF <NUM> may provide most of the functions that the MME provides in a <NUM> network as mentioned above. Below please find a brief list of some of its functions:.

Further, the SMF <NUM> may provide the session management functions that are handled by the <NUM> MME, SGW-C, and PGW-C. Below please find a brief list of some of its functions:.

Further, the UPFs <NUM> is essentially a fusion of the data plane parts of the SGW and PGW, as mentioned above. In the context of the CUPS architecture: EPC SGW-U + EPC PGW-U → <NUM> UPF.

The UPFs <NUM> may perform the following functions:.

As shown in <FIG>, the UPFs <NUM> are communicatively connected to the Data Network (DN) <NUM> which may be, or in turn communicatively connected to, the Internet, such that the UE <NUM> may finally communicate its user plane data with other devices outside the network <NUM>, for example, via the RAN <NUM> and the UPFs <NUM>.

Further, the NRF <NUM> is basically a service registry, which provides a service registration and discovery service to various network functions (NFs) such that the NFs can discover each other via the NRF <NUM>. Further, the NRF <NUM> may maintain NF profiles and NF instances.

As mentioned above, when a UE is handed over from a source cell to a target cell with an active data connection, a data forwarding tunnel is sometimes required to be established between the source and target cells. Therefore, it is a problem for the serving SMF <NUM> to discover or identify a correct UPF <NUM> with such a data forwarding capability. This problem will be discussed in detail with reference to <FIG> below.

Further, Network Instances (Nls) are used to define on the UPFs <NUM> to specify different routing domains for different User Plane interfaces, e.g. network instance for access (e.g. N3) for connectivity to the RAN nodes, network interface for Core (e.g. N9) for connectivity to other Core Network hops.

In different scenarios for UE mobility with indirect data forwarding, a data path may go through multiple routing domains, for example:.

To overcome these complexity, specific routing domain for data forwarding purpose (which is focusing more on connectivity than traffic loads, as traffic for data forwarding is rather small compare to normal traffic flow). In this case, these specific network instance(s) for data forwarding should be configured in the UPF, and the SMF should indicate a correct network instance when allocating Tunnel Endpoints for data forwarding via N4. Currently it is not possible because the SMF cannot get the information on which network instance to be used for data forwarding in the UPF.

<FIG> is a diagram illustrating a telecommunication system <NUM> to which a method for data forwarding according to an embodiment of the present disclosure is applicable. As shown in <FIG>, the telecommunication system <NUM> may comprise a UE <NUM> and its source serving access node, gNB-<NUM> (or S-NG-RAN) <NUM>, which provides access to the UE <NUM> in its serving cell, Cell-<NUM><NUM>, before the UE <NUM> moves out of the Cell-<NUM><NUM>. Further, the telecommunication system <NUM> may further comprise a target serving access node, gNB-<NUM> (or T-NG-RAN) <NUM>, which will provide access to the UE <NUM> in its serving cell, Cell-<NUM><NUM>, after the UE <NUM> moves into the Cell-<NUM><NUM>. In other words, when the UE-<NUM><NUM> moves from the source Cell-<NUM><NUM> to the target Cell-<NUM><NUM>, a handover procedure is performed for the UE-<NUM><NUM> at various nodes shown in <FIG>.

Referring to <FIG>, the telecommunications system <NUM> may further comprise one or more UPFs, for example, an S-UPF <NUM>, a T-UPF <NUM>, and a UPF (PDU Session Anchor, or PSA) <NUM>, via which the UE <NUM> may communicate its user plane data with the Internet <NUM>. To be specific, the S-UPF <NUM> is a serving UPF for the UE <NUM> while the UE <NUM> is served by the gNB-<NUM><NUM>, and the T-UPF <NUM> is a serving UPF for the UE <NUM> while the UE <NUM> is served by the gNB-<NUM><NUM>. Further, the UPF (PSA) is an anchor UPF which terminates the N6 interface of a PDU session for the UE <NUM> within in the core network shown in <FIG>. Further, the telecommunications system <NUM> may comprise one or more forwarding UPFs, which may be dedicated for data forwarding between cells, such as a forwarding UPF <NUM> for data forwarding between the Cell-<NUM><NUM> and the Cell-<NUM><NUM>.

Furthermore, there could be one or more other UPFs in the telecommunications network <NUM>, for example, one or more UPFs between the UPF (PSA) <NUM> and the Internet <NUM> and/or between the UPF (PSA) <NUM> and the S-UPF <NUM>/T-UPF <NUM>, or more than one forwarding UPFs <NUM>, or the like. Therefore, the present disclosure is not limited to the embodiment shown in <FIG> in this regard.

Referring to <FIG> again, the telecommunications system <NUM> may further comprise an S-AMF or Source-AMF <NUM>, a T-AMF or Target-AMF <NUM>, an SMF <NUM>, and an NRF <NUM>. Further, some of the components are omitted from <FIG> for simplicity, for example, a PCF, an AF, an NSSF, etc., as those shown in <FIG>, since they are not directly involved in the embodiments of the present disclosure.

Please note that this deployment is only for the purpose of illustration rather than limiting of the present disclosure. In some other embodiments, the telecommunications system <NUM> may comprise more UEs, gNBs, UPFs, AMFs, SMFs, and/or NRFs, or may have different configurations thereof and/or different connections therebetween.

As shown in <FIG>, when the UE <NUM> moves from the Cell-<NUM><NUM> to the Cell-<NUM><NUM>, a handover procedure is triggered. According to the subclause <NUM>. <NUM>, 3GPP TS <NUM>, V16. <NUM>, an inter NG-RAN node N2 based handover procedure may be initiated. Next, a detailed description of the handover procedure will be given with reference to <FIG>, <FIG>, and <FIG>.

<FIG> and <FIG> are message flow diagrams illustrating exemplary messages exchanged between different nodes for facilitating data forwarding according to an embodiment of the present disclosure. Please note that some nodes shown in <FIG>, such as the UE <NUM>, the S-NG-RAN <NUM>, the T-NG-RAN <NUM> are omitted from <FIG> since they are not directly related to the steps shown in <FIG>.

As shown in <FIG> and <FIG>, UE <NUM> may communicate its downlink/uplink user plane data with the Internet <NUM>, for example, via S-NG-RAN (or gNB-<NUM>) <NUM>, S-UPF <NUM>, and UPF (PSA) <NUM> before the handover procedure is triggered.

Referring to <FIG>, the source NG-RAN <NUM> may decide to initiate an N2-based handover of the UE <NUM> to the target NG-RAN <NUM>. This can be triggered, for example, due to new radio conditions or load balancing, if there is no Xn connectivity to the target NG-RAN <NUM>, an error indication from the target NG-RAN <NUM> after an unsuccessful Xn-based handover (i.e. no IP connectivity between the T-RAN <NUM> and the S-UPF <NUM>), or based on dynamic information learnt by the S-RAN <NUM>.

The availability of a direct forwarding path may be determined in the source NG-RAN <NUM> and indicated to the SMFs (e.g. the serving SMF <NUM>). If IP connectivity is available between the source and target NG-RANs <NUM> and <NUM> and security association(s) is in place between them, a direct forwarding path is available. However, if a direct forwarding path is not available, indirect forwarding may be used, for example, as shown in <FIG>. The SMF <NUM> may use the indication from the source NG-RAN <NUM> to determine whether to apply indirect forwarding.

As shown in <FIG>, at step S301, the S-RAN <NUM> may transmit to the S-AMF <NUM> a Handover Required message to indicate its desire of handover of the UE <NUM>. All PDU Sessions of the UE <NUM> handled by the S-RAN <NUM> (i.e. all existing PDU Sessions with active UP connections) may be included in the Handover Required message, indicating which of those PDU Session(s) are requested by the S-RAN <NUM> to handover.

Further, in some embodiments, Direct Forwarding Path Availability included in the Handover Required message may indicate whether direct forwarding is available from the S-RAN <NUM> to the T-RAN <NUM>. This indication from the S-RAN <NUM> can be based on e.g. the presence of IP connectivity and security association(s) between the S-RAN <NUM> and the T-RAN <NUM> as mentioned above. In the embodiment shown in <FIG>, the indication indicates that the direct data forwarding is not available.

At step S302, the S-AMF <NUM> may select a T-AMF (e.g. the T-AMF <NUM>) for the UE <NUM> and the target RAN <NUM>. To be specific, when the S-AMF <NUM> cannot serve the UE <NUM> anymore, the S-AMF <NUM> may select the T-AMF <NUM>.

At step S303, the S-AMF <NUM> may transmit to the T-AMF <NUM> an Namf_Communication_CreateUEContext Request message to request the T-AMF <NUM> to create a UE context for the UE <NUM>.

At step S304, upon receipt of the Namf_Communication_CreateUEContext Request message, the T-AMF <NUM> may transmit to the serving SMF <NUM> an Nsmf_PDUSession_UpdateSMContext Request message. For each PDU Session indicated by the S-RAN <NUM>, the T-AMF <NUM> may invoke an Nsmf_PDUSession_UpdateSMContext Request to the associated SMF <NUM>. However, if the S-NSSAI associated with PDU Session is not available in the T-AMF <NUM>, the T-AMF <NUM> does not invoke Nsmf_PDUSession_UpdateSMContext for this PDU Session.

At step S305, based on the information comprised in the received Nsmf_PDUSession_UpdateSMContext Request, the SMF <NUM> may check if N2 Handover for the indicated PDU Session of the UE <NUM> can be accepted or not. Further, the SMF <NUM> may check also the UPF Selection Criteria. If the UE <NUM> has moved out of the service area of the UPF connecting to NG-RAN, the SMF <NUM> may select a new intermediate UPF. If redundant transmission is performed for one or more Quality of Service (QoS) Flows of the PDU Session, the SMF <NUM> may select two new Intermediate UPFs to support the redundant transmission based on two N3 and N9 tunnels between the T-RAN <NUM> and the UPF (PSA) <NUM>. In this case, the step S306c and S306d are performed between the SMF <NUM> and each T-UPF <NUM>.

At step S306a, the SMF <NUM> may transmit to the UPF (PSA) <NUM> an N4 Session Modification Request message. If the SMF <NUM> selects a new UPF to act as intermediate UPF for the PDU Session, and the different CN Tunnel Info need be used, the SMF <NUM> may send the N4 Session Modification Request message to the UPF (PSA) <NUM>.

At step S306b, the UPF (PSA) <NUM> may transmit to the SMF <NUM> an N4 Session Modification Response message. If the UPF (PSA) <NUM> allocates CN Tunnel Info (on N9) of UPF (PSA) <NUM>, it may provide CN Tunnel Info (on N9) to the SMF <NUM>.

At step S306c, the SMF <NUM> may transmit to the T-UPF <NUM> an N4 Session Establishment Request message. The N4 Session Establishment Request message is sent to the T-UPF <NUM> to provide Packet detection, enforcement and reporting rules to be installed on the T-UPF <NUM>. The CN Tunnel Info (on N9) of UPF (PSA) <NUM> for this PDU Session, which is used to set up N9 tunnel, is also provided to the T-UPF <NUM>.

At step S306d, the T-UPF <NUM> may transmit to the SMF <NUM> an N4 Session Establishment Response message with DL CN Tunnel Info and UL CN Tunnel Info.

At step S307, the SMF <NUM> may transmit to the T-AMF <NUM> an Nsmf_PDUSession_UpdateSMContext Response message to indicate the SMF <NUM> has updated its SMContext for the indicated PDU session and is ready for the handover of the UE <NUM>.

At step S308, the T-AMF <NUM> may supervise the Nsmf_PDUSession_UpdateSMContext Response message from the SMF <NUM>. When the Nsmf_PDUSession_UpdateSMContext Response message is received, the T-AMF <NUM> may continue with the N2 Handover procedure.

At step S309, the T-AMF <NUM> may transmit to the T-RAN <NUM> a Handover Request message to instruct the T-RAN <NUM> to prepare for a handover of the UE <NUM>.

At step S310, the T-RAN <NUM> may transmit to the T-AMF <NUM> a Handover Request Acknowledge message to acknowledge the handover request.

At step S311a shown in <FIG>, the T-AMF <NUM> may transmit to the SMF <NUM> an Nsmf_PDUSession_UpdateSMContext Request message. For each N2 SM response received from the T-RAN <NUM> (i.e. N2 SM information included in Handover Request Acknowledge), the T-AMF <NUM> may send the received N2 SM response to the SMF <NUM>.

At step S311b, the SMF <NUM> may transmit to the T-UPF <NUM> an N4 Session Modification Request message which may comprise indication to allocate DL forwarding tunnel(s) for indirect forwarding. To be specific, the SMF <NUM> may update the T-UPF <NUM> by providing the T-RAN SM N3 forwarding information list by sending a N4 Session Modification Request to the T-UPF <NUM>.

If indirect forwarding applies based on indication from the S-RAN <NUM> and the UPF is re-allocated and if the SMF <NUM> decides to setup the indirect forwarding tunnel on the same T-UPF <NUM>, the SMF <NUM> may also request in the N4 Session Modification Request message to the T-UPF <NUM>, to allocate DL forwarding tunnel(s) for indirect forwarding.

Indirect forwarding may be performed via a UPF which is different from the S-UPF <NUM> and the T-UPF <NUM>. In such a case, the SMF <NUM> may select a Forwarding UPF <NUM> shown in <FIG> for indirect forwarding. To be specific, the forwarding UPF <NUM> is a different UPF than the S-UPF <NUM> and the T-UPF <NUM>, and it may relay the data for the UE <NUM> from the S-NG-RAN <NUM> to the T-NG-RAN <NUM> with the help of S-UPF <NUM> and the T-UPF <NUM>. The description of the register & discovery procedures for the forwarding UPF <NUM> will be explained in detail with reference to <FIG>.

Nevertheless, the SMF <NUM> may determine or identify one or more forwarding UPFs <NUM> for indirect forwarding and inform the T-UPF <NUM> of information related to the UPFs <NUM>.

At step S311c, the T-UPF <NUM> may transmit to the SMF <NUM> an N4 Session Modification Response message to indicate its DL forwarding information and/or its awareness of the forwarding UPF <NUM>.

At step S311d, the SMF <NUM> may transmit to the S-UPF <NUM> an N4 Session Modification Request message to inform the S-UPF <NUM> of the information of the forwarding UPF <NUM>. In other words, the SMF <NUM> may indicate in the N4 Session Modification Request message to the S-UPF <NUM> to allocate DL forwarding tunnel(s) for indirect forwarding. Indirect forwarding may be performed via the forwarding UPF <NUM> which is different from the S-UPF <NUM> and the T-UPF <NUM>.

At step S311e, the S-UPF <NUM> may transmit to the SMF <NUM> an N4 Session Modification Response message indicate its DL forwarding information and/or its awareness of the forwarding UPF <NUM>.

At step S311f, the SMF <NUM> may transmit to the T-AMF <NUM> an Nsmf_PDUSession_UpdateSMContext Response message. The SMF <NUM> may include the T-UPF <NUM> and/or S-UPF <NUM>'s DL forwarding information containing the N3 UP address and the DL Tunnel ID of the UPFs.

At step S312, the T-AMF <NUM> may transmit to the S-AMF <NUM> an Namf_Communication_CreateUEContext Response message. The T-AMF <NUM> may supervise the Nsmf_PDUSession_UpdateSMContext Response message from the SMF <NUM> and send the Namf_Communication_CreateUEContext Response message to the S-AMF <NUM>.

After that, an execution phase of the handover procedure may be performed as provisioned in Subclause <NUM>. <NUM> of 3GPP TS <NUM>, V16.

As shown in <FIG>, <FIG>, and <FIG>, a handover procedure with indirect forwarding via the forwarding UPF <NUM> may be accomplished, and the data, which is destined to the UE <NUM> but sent to the S-UPF <NUM> during the handover procedure may be transferred via the forwarding UPF <NUM> to the T-UPF <NUM>, the gNB-<NUM><NUM>, and finally to the UE <NUM> once the UE <NUM> is handed over to and served by the Cell-<NUM><NUM>.

Next, the register & discovery procedures for the forwarding UPF <NUM> may be described in detail with reference to <FIG>.

<FIG> are message flow diagrams illustrating exemplary messages exchanged between different nodes for facilitating data forwarding according to another embodiment of the present disclosure. During a register & discovery procedure, three parties are typically involved, that is, a service producer, a service consumer, and a service registry or repository. As used herein, a service producer is responsible for providing a certain service which is to be consumed by a service consumer, and a service registry is responsible to maintain the information of the service producer and help the service consumer to discover the service producer. Please note that a service producer for a first service may also be a service consumer and/or service registry for a second service, or vice versa. For example, as shown in <FIG>, the NRF <NUM> acts as a service registry or repository, while it is also a service producer with respect to its service-registering service and service-discovery service. For another example, an NF service producer, such as a UPF which provides data forwarding service (or function or capability), may also a service consumer due to the use of the service-registering service offered by the NRF <NUM>. For yet another example, an NF service consumer as shown in <FIG>, such as an SMF which needs the data forwarding service (or function or capability) offered by the UPF, may also a service consumer due to the use of the service-discovering service offered by the NRF <NUM>.

Referring back to <FIG> and with reference to <FIG>, the NF service consumer <NUM> (e.g., the forwarding UPF <NUM> shown in <FIG>, which is a consumer of the service-registering service provided by the NRF <NUM>) may register its data forwarding service or function with the NRF <NUM> (e.g. the NRF <NUM> shown in <FIG>), for example, via a "NFRegister" or "NFUpdate" procedure or a request/response message for Nnrf_NFManagement service similar to that defined in Subclause <NUM>, 3GPP TS <NUM>, V16. Further, in some other embodiments, the NF Service Consumer <NUM> may not be the UPF itself, but another network function or node which registers the UPF's data forwarding function on behalf of the UPF. In some embodiments, the NF Service Consumer <NUM> may be an Operation & Maintenance entity/node/unit or even a human user who manually modifies the NRF <NUM>'s local configuration.

To be specific, at step S401, the UPF <NUM> may send a Hyper Text Transfer Protocol (HTTP) PUT request to the NRF <NUM>. As shown in <FIG>, the PUT message may comprise (i) an indicator indicating that the UPF <NUM> provides a data forwarding service or has a data forwarding function; and/or (ii) one or more indicators indicating the network instances for data forwarding. On success at step S402, an HTTP "<NUM> Created" response message may be returned.

In this way, the NRF <NUM> may be informed of the data forwarding capability of the UPF <NUM>, and this information may be maintained at the NRF <NUM> and discovered by another NF, for example, as shown in <FIG>.

Referring to <FIG> and with reference to <FIG>, the NF service consumer <NUM> (e.g., the SMF <NUM> shown in <FIG>, which is a consumer of the service-discovering service provided by the NRF <NUM>) may discover NFs providing a data forwarding service with the help from the NRF <NUM> (e.g. the NRF <NUM> shown in <FIG>), for example, via a "NFDiscover" procedure or a request/response message for Nnrf_NFDiscovery service similar to that defined in Subclause <NUM>, 3GPP TS <NUM>, V16.

To be specific, the SMF <NUM> may send an HTTP GET request to the NRF <NUM> at step S405. The input filter criteria for the discovery request may be included in query parameters, for example, "<query parameters: data-forwarding=true>" which indicates that the SMF <NUM> tries to find a UPF having a data forwarding function.

At step S406, on success, an HTTP "<NUM> OK" response message may be returned. The response body may contain a validity period, during which the search result can be cached by the SMF <NUM>, and an array of NF Profile objects, that satisfy the search filter criteria (e.g., all NF Instances offering a data forwarding service).

Although some exemplary procedures for service register & discovery are shown in <FIG>, the present disclosure is not limited thereto. For example, some other function register & discovery procedures may be described with reference to <FIG>.

<FIG> are message flow diagrams illustrating exemplary messages exchanged between different nodes for facilitating data forwarding according to yet another embodiment of the present disclosure.

Referring to <FIG> and with reference to <FIG>, a UP function <NUM> (e.g., the forwarding UPF <NUM> shown in <FIG>) may inform its data forwarding service or function to a CP function <NUM> (e.g. the SMF <NUM> or the NRF <NUM> shown in <FIG>), for example, via a procedure similar to that defined in Subclause <NUM>. <NUM>/<NUM>. <NUM>, 3GPP TS <NUM>, V16.

To be specific, at step S501, the UP function <NUM> may receive a Packet Forwarding Control Plane (PFCP) Association Setup Request message from the CP function <NUM> to setup a PFCP association therebetween, to enable the CP function <NUM> to use the resources of the UP function <NUM> subsequently.

At step S502, upon receipt of the PFCP Association Setup Request message, the UP function <NUM> may respond with a PFCP Association Setup Response message comprising: (i) an indicator indicating that the UP function <NUM> provides a data forwarding service or has a data forwarding function; (ii) one or more indicators indicating the network instances for data forwarding; and (iii) one or more indicators indicating a target area towards which IP connectivity is enabled by at least one of the network instances indicated in (ii). In some embodiments, the target area may be represented by a list of Tracking Area Identities (TAls), a list of NG-RAN-ids, or a list of eNB-ids.

In this way, the CP function <NUM> may be informed of the data forwarding capability of the UP function <NUM>, and this information may be used during the selection of UPF at the CP function <NUM>.

<FIG> shows a similar procedure as that shown in <FIG> with the difference that this procedure is initiated by the UP function <NUM> rather than the CP function <NUM>. To be specific, at step S503, the UP function <NUM> may transmit a Packet Forwarding Control Plane (PFCP) Association Setup Request message to the CP function <NUM> to setup a PFCP association therebetween, to enable the CP function <NUM> to use the resources of the UP function <NUM> subsequently. The PFCP Association Setup Request message may comprise: (i) an indicator indicating that the UP function <NUM> provides a data forwarding service or has a data forwarding function; (ii) one or more indicators indicating the network instances for data forwarding; and (iii) one or more indicators indicating a target area towards which IP connectivity is enabled by at least one of the network instances indicated in (ii). In some embodiments, the target area may be represented by a list of Tracking Area Identities (TAls), a list of NG-RAN-ids, or a list of eNB-ids.

At step S504, upon receipt of the PFCP Association Setup Request message, the CP function <NUM> may respond with a PFCP Association Setup Response message to acknowledge the awareness of the data forwarding capability of the UP function <NUM>.

In such a way, an SMF or NRF may be informed of the data forwarding capability of a UPF, and subsequent operations may be performed accordingly.

Further, a proposed change of 3GPP TS <NUM> may be as follows:.

Further, although <FIG> show an improved PFCP Association Setup procedure, some other procedures may also be used. For example, in some embodiments, a similarly improved PFCP Association Update procedure may also be applicable to inform an SMF or NRF of the data forwarding capability of a UPF. The present disclosure is not limited thereto.

Furthermore, although the embodiments described above are given in the context of <NUM> terminologies, similar issues may be present for a <NUM> LTE network, or more specific, Evolved Packet Core (EPC) network as well. Therefore, an enhanced DNS procedure is also proposed to enable the MME (to find a forwarding SGW or SGW-C) and the SGW-C (to find a SGW-U) to use enhanced DNS Records for SGW-C and SGW-U, respectively, with new application protocol, or new network capability corresponding to the data forwarding.

First, an SGW-C and/or an SGW-U being configured for data forwarding may be provisioned with a DNS NAPTR record under a target area, e.g. a TAI FQDN or eNode-ID FQDN, in the DNS server, for example, similarly to that defined in Subclause <NUM>. <NUM>, 3GPP TS <NUM>, V16.

In some embodiments, the (forwarding) SGW-C NAPTR DNS record may be enhanced with provisioning a new app-protocol, e.g. x-sgwforwarding, for the existing app-service, x-3gpp-sgw; or as a new Network Capability (e.g., named "sgwforwarding" or "sf"), where an existing app-protocol may be appended with "+nc-sgwforwarding", e.g. "x-3gpp-sgw:x-s5-gtp+nc-sgwforwarding". Please note that the names are only exemplary and the present disclosure is not limited thereto.

Similarly, the (forwarding) SGW-U NAPTR DNS record may be enhanced with provisioning a new app-protocol, e.g. x-sgwforwarding, for the existing app-service, x-3gpp-upf; or as a new Network Capability (e.g. named "sgwforwarding" or "sf"), where an existing app-protocol may be appended with "+nc-sgwforwarding", e.g. "x-3gpp-upf:x-sxa+nc-sgwforwarding". The "+nc-sgwforwarding" can be appended further with the corresponding network instance. e.g. "x-3gpp-upf:x-sgwforwarding+nc-networkinstance" or "x-3gpp-upf:x-sxa+nc-sgwforwarding. networkinstance". The symbol ". " between sgwforwarding and network instance is delimiter.

Next, an MME may start an S-NAPTR procedure with an Application Unique String which set to target area FQDN, e.g. TAI FQDN or eNode-ID FQDN, and desired services x-3gpp-sgw:x-sgwforwarding, x-3gpp-sgw:x-s5-gtp (if new app-protocol is used) or x-3gpp-sgw:x-s5-gtp+nc-sgwforwarding (when sgwforwarding is defined as a network capability in the DNS).

Similarly, the SGW-C may start an S-NAPTR procedure with an Application Unique String which set to target area FQDN, e.g. TAI FQDN or eNode-ID FQDN, and desired services x-3gpp-upf:x-sgwforwarding or x-3gpp-upf:x-sxa+nc-sgwforwarding.

Therefore, the MME or SGW-C may discover the SGW-U which provides a data forwarding function with the help of the DNS server.

Further, in some embodiments, additional information (e.g. Tracking Area or SMF Serving Area) might be provided by UPF together with the indication, indicating the serving area which is capable performing the data forwarding as part of Upflnfo, for example. Further, in some embodiments, additional information (e.g. Tracking Area or SMF serving area) might be provided by the UPF per network instance, to help SMF to identify which network instance to be used based on e.g. UE location. Further, in some embodiments, certain additional information might be provided by the AMF to the SMF, e.g. when perform PDU Session modification during handover or idle mobility.

Further, in the above embodiments, a UPF may register its own service at an NRF. The present disclosure is not limited thereto. In some other embodiments where the UPF itself may not support Service Registration to register its support of data forwarding, such registration at the NRF may be performed via Operation & Management, or may be performed via local configuration.

<FIG> is a flow chart of an exemplary method <NUM> for facilitating data forwarding according to an embodiment of the present disclosure. The method <NUM> may be performed at a first network element (e.g. the NRF <NUM> shown in <FIG>, the NRF <NUM> shown in <FIG>, the NRF <NUM> shown in <FIG>, the CP function <NUM> shown in <FIG>, or the network element <NUM> shown in <FIG>) for facilitating data forwarding. The method <NUM> may comprise step S610 and an optional Step S620. However, the present disclosure is not limited thereto. In some other embodiments, the method <NUM> may comprise more steps, less steps, different steps or any combination thereof. Further the steps of the method <NUM> may be performed in a different order than that described herein. Further, in some embodiments, a step in the method <NUM> may be split into multiple sub-steps and performed by different entities, and/or multiple steps in the method <NUM> may be combined into a single step.

The method <NUM> may begin at step S610 where a first message comprising a first indicator indicating that a data forwarding function is supported by the second network element is received from a second network element. In some embodiments, the first message may be a first request message which requests registering, at the first network element, one or more functions of the second network element comprising the data forwarding function.

At step S620, a first response message comprising a second indicator indicating success of the registration may be transmitted to the second network element.

In some embodiments, the first network element may be a Network Repository Function (NRF), and the second network element may be a User Plane Function (UPF) or Serving GateWay for User plane (SGW-U). In some embodiments, the first request message may be a request message for Nnrf_NFManagement service, and the first response message may be a response message for Nnrf_NFManagement service. In some embodiments, the first indicator may be an attribute of the data type "Upflnfo" comprised in the first request message.

In some embodiments, the method <NUM> may further comprise: receiving, from a third network element, a second request message comprising a third indicator indicating a query for network elements having the data forwarding function. In some embodiments, the method may further comprise: transmitting, to the third network element, a second response message comprising a list of one or more fourth indicators, each of the one or more fourth indicators indicating a network element having the data forwarding function. In some embodiments, the second network element may be one of the one or more network elements indicated by the one or more fourth indicators. In some embodiments, the third network element may be a Session Management Function (SMF), a Mobility Management Entity (MME), or a SGW for Control plane (SGW-C). In some embodiments, the second request message may be a request message for Nnrf_NFDiscovery service, and the second response message may be a response message for Nnrf_NFDiscovery service. In some embodiments, the third indicator may be a Uniform Resource Indicator (URI) query parameter comprised in the second request message. In some embodiments, the first message may comprise one or more fifth indicators indicating one or more network instances supported by the second network element for data forwarding. In some embodiments, for each of the one or more network elements indicated by the one or more fourth indicators, the second response message may comprise one or more fifth indicators indicating one or more network instances supported by the corresponding network element for data forwarding. In some embodiments, each of the fifth indicators may be an attribute of the data type "Upflnfo" comprised in the first request message or in the second response message.

In some embodiments, the first message may be one of: a Packet Forwarding Control Plane (PFCP) Association Setup Request message; a PFCP Association Update Request message; a PFCP Association Setup Response message in response to a PFCP Association Setup Request message previously transmitted from the first network element to the second network element; and a PFCP Association Update Response message in response to a PFCP Association Setup Update message previously transmitted from the first network element to the second network element. In some embodiments, the first network element may be a Control Plane (CP) function, and the second network element may be a User Plane (UP) function. In some embodiments, the first indicator may be an information element (IE) comprised in the first message. In some embodiments, the first message may comprise one or more fifth indicators indicating one or more network instances supported by the second network element for data forwarding. In some embodiments, each of the fifth indicators may be an IE comprised in the first message.

In some embodiments, the first message may further comprise a sixth indicator indicating a target area towards which IP connectivity is enabled by at least one of the network instances indicated by the fifth indicators. In some embodiments, the sixth indicator may indicate a target area towards which IP connectivity is enabled by one of the network instances indicated by the fifth indicators. In some embodiments, the sixth indicator may comprise a list of Tracking Area Information (TAI) or a list of NG-RAN IDs.

In some embodiments, the first network element may be a Domain Name System (DNS) server. In some embodiments, the first message may be a first request message which requests adding or updating a Name Authority PoinTeR (NAPTR) DNS record at the first network element, and the NAPTR DNS record may indicate that the second network element or another network element supports the data forwarding function. In some embodiments, the method may further comprise: receiving, from a third network element, a second request message comprising a third indicator indicating a query for network elements having the data forwarding function. In some embodiments, the method may further comprise: transmitting, to the third network element, a second response message comprising a list of one or more fourth indicators, each of the one or more fourth indicators indicating a network element having the data forwarding function. In some embodiments, the second network element may be one of the one or more network elements indicated by the one or more fourth indicators. In some embodiments, the third network element may be one of an Mobility Management Entity (MME) and an SGW-C.

<FIG> is a flow chart of an exemplary method <NUM> for facilitating data forwarding according to an embodiment of the present disclosure. The method <NUM> may be performed at a second network element (e.g. the UPF <NUM> shown in <FIG>, the Forwarding UPF <NUM> shown in <FIG>, the NF Service Consumer <NUM> shown in <FIG>, the UP function <NUM> shown in <FIG>, or the network element <NUM> shown in <FIG>) for facilitating data forwarding. The method <NUM> may comprise step S710 and an optional Step S720. However, the present disclosure is not limited thereto. In some other embodiments, the method <NUM> may comprise more steps, less steps, different steps or any combination thereof. Further the steps of the method <NUM> may be performed in a different order than that described herein. Further, in some embodiments, a step in the method <NUM> may be split into multiple sub-steps and performed by different entities, and/or multiple steps in the method <NUM> may be combined into a single step.

The method <NUM> may begin at step S710 where a first message comprising a first indicator indicating that a data forwarding function is supported by the second network element is transmitted to a first network element. In some embodiments, the first message may be a first request message which requests registering, at the first network element, one or more functions of the second network element comprising the data forwarding function.

At step S720, a first response message comprising a second indicator indicating success of the registration may be received from the first network element.

In some embodiments, the first network element may be a Network Repository Function (NRF), and the second network element may be a User Plane Function (UPF) or Serving GateWay for User plane (SGW-U). In some embodiments, the first request message may be a request message for Nnrf_NFManagement service, and the first response message may be a response message for Nnrf_NFManagement service. In some embodiments, the first indicator may be an attribute of the data type "Upflnfo" comprised in the first request message. In some embodiments, the first message may comprise one or more fifth indicators indicating one or more network instances supported by the second network element for data forwarding. In some embodiments, each of the fifth indicators may be an attribute of the data type "Upflnfo" comprised in the first request message. In some embodiments, the first message may be one of: a Packet Forwarding Control Plane (PFCP) Association Setup Request message; PFCP Association Update Request message; a PFCP Association Setup Response message in response to a PFCP Association Setup Request message previously transmitted from the first network element to the second network element; and a PFCP Association Update Response message in response to a PFCP Association Setup Update message previously transmitted from the first network element to the second network element.

In some embodiments, the first network element may be a Control Plane (CP) function, and the second network element may be a User Plane (UP) function. In some embodiments, the first indicator may be an information element (IE) comprised in the first message. In some embodiments, the first message may comprise one or more fifth indicators indicating one or more network instances supported by the second network element for data forwarding. In some embodiments, each of the fifth indicators may be an IE comprised in the first message. In some embodiments, the first message may further comprise a sixth indicator indicating a target area towards which IP connectivity is enabled by at least one of the network instances indicated by the fifth indicators. In some embodiments, the sixth indicator may indicate a target area towards which IP connectivity is enabled by one of the network instances indicated by the fifth indicators. In some embodiments, the sixth indicator may comprise a list of Tracking Area Information (TAI) or a list of NG-RAN IDs.

In some embodiments, the first network element may be a Domain Name System (DNS) server. In some embodiments, the first message may be a first request message which requests adding or updating a Name Authority PoinTeR (NAPTR) DNS record at the first network element, and the NAPTR DNS record may indicate that the second network element or another network element supports the data forwarding function.

<FIG> is a flow chart of an exemplary method <NUM> for facilitating data forwarding according to an embodiment of the present disclosure. The method <NUM> may be performed at a third network element (e.g. the SMF <NUM> shown in <FIG>, the SMF <NUM> shown in <FIG>, the NF Service Consumer <NUM> shown in <FIG>, the CP function <NUM> shown in <FIG>, or the network element <NUM> shown in <FIG>) for facilitating data forwarding. The method <NUM> may comprise step S810 and an optional Step S820. However, the present disclosure is not limited thereto. In some other embodiments, the method <NUM> may comprise more steps, less steps, different steps or any combination thereof. Further the steps of the method <NUM> may be performed in a different order than that described herein. Further, in some embodiments, a step in the method <NUM> may be split into multiple sub-steps and performed by different entities, and/or multiple steps in the method <NUM> may be combined into a single step.

The method <NUM> may begin at step S810 where a second request message comprising a third indicator indicating a query for network elements having a data forwarding function is transmitted to a first network element.

At step S820, a second response message comprising a list of one or more fourth indicators is received from the first network element, each of the one or more fourth indicators indicating a network element having the data forwarding function.

In some embodiments, the third network element may be a Session Management Function (SMF), Mobility Management Entity (MME), or a SGW for Control plane (SGW-C). In some embodiments, the second request message may be a request message for Nnrf_NFDiscovery service, and the second response message may be a response message for Nnrf_NFDiscovery service. In some embodiments, the third indicator may be a Uniform Resource Indicator (URI) query parameter comprised in the second request message. In some embodiments, for each of the one or more network elements indicated by the one or more fourth indicators, the second response message may comprise one or more fifth indicators indicating one or more network instances supported by the corresponding network element for data forwarding. In some embodiments, each of the fifth indicators may be an attribute of the data type "Upfinfo" comprised in the second response message. In some embodiments, the first network element may be a Control Plane (CP) function. In some embodiments, the first indicator may be an information element (IE) comprised in the first message. In some embodiments, the method may further comprise: selecting one of the one or more network elements indicated by the one or more fourth indicators based at least on the network instances supported by the one or more network elements and/or a location of an UE of interest. In some embodiments, the first network element may be a Domain Name System (DNS) server.

<FIG> schematically shows an embodiment of an arrangement <NUM> which may be used in a network element (e.g., the first network element, the second network element, or the third network element) according to an embodiment of the present disclosure. Comprised in the arrangement <NUM> are a processing unit <NUM>, e.g., with a Digital Signal Processor (DSP) or a Central Processing Unit (CPU). The processing unit <NUM> may be a single unit or a plurality of units to perform different actions of procedures described herein. The arrangement <NUM> may also comprise an input unit <NUM> for receiving signals from other entities, and an output unit <NUM> for providing signal(s) to other entities. The input unit <NUM> and the output unit <NUM> may be arranged as an integrated entity or as separate entities.

Furthermore, the arrangement <NUM> may comprise at least one computer program product <NUM> in the form of a non-volatile or volatile memory, e.g., an Electrically Erasable Programmable Read-Only Memory (EEPROM), a flash memory and/or a hard drive. The computer program product <NUM> comprises a computer program <NUM>, which comprises code/computer readable instructions, which when executed by the processing unit <NUM> in the arrangement <NUM> causes the arrangement <NUM> and/or the network elements in which it is comprised to perform the actions, e.g., of the procedure described earlier in conjunction with <FIG> or any other variant.

The computer program <NUM> may be configured as a computer program code structured in a computer program module 910A. Hence, in an exemplifying embodiment when the arrangement <NUM> is used in a first network element, the code in the computer program of the arrangement <NUM> includes: a reception module 910A for receiving, from a second network element, a first message comprising a first indicator indicating that a data forwarding function is supported by the second network element.

Further, the computer program <NUM> may be configured as a computer program code structured in a computer program module 910B. Hence, in an exemplifying embodiment when the arrangement <NUM> is used in a second network element, the code in the computer program of the arrangement <NUM> includes: a transmission module 910B for transmitting, to a first network element, a first message comprising a first indicator indicating that a data forwarding function is supported by the second network element.

Furthermore, the computer program <NUM> may be configured as a computer program code structured in a computer program module 910C. Hence, in an exemplifying embodiment when the arrangement <NUM> is used in a third network element, the code in the computer program of the arrangement <NUM> includes: a transmission module 910C for transmitting, to a first network element, a second request message comprising a third indicator indicating a query for network elements having a data forwarding function.

The computer program modules could essentially perform the actions of the flow illustrated in <FIG>, to emulate the network elements. In other words, when the different computer program modules are executed in the processing unit <NUM>, they may correspond to different modules in the various network elements.

Although the code means in the embodiments disclosed above in conjunction with <FIG> are implemented as computer program modules which when executed in the processing unit causes the arrangement to perform the actions described above in conjunction with the figures mentioned above, at least one of the code means may in alternative embodiments be implemented at least partly as hardware circuits.

The processor may be a single CPU (Central processing unit), but could also comprise two or more processing units. For example, the processor may include general purpose microprocessors; instruction set processors and/or related chips sets and/or special purpose microprocessors such as Application Specific Integrated Circuit (ASICs). The processor may also comprise board memory for caching purposes. The computer program may be carried by a computer program product connected to the processor. The computer program product may comprise a computer readable medium on which the computer program is stored. For example, the computer program product may be a flash memory, a Random-access memory (RAM), a Read-Only Memory (ROM), or an EEPROM, and the computer program modules described above could in alternative embodiments be distributed on different computer program products in the form of memories within the UE.

Claim 1:
A method performed by a Network Repository Function, NRF, (<NUM>, <NUM>) for facilitating data forwarding, the method comprising:
receiving (<NUM>), directly or indirectly, from a forwarding User Plane Function, UPF, (<NUM>, <NUM>), a HTTP PUT register request message comprising a first indicator indicating that a data forwarding function is supported by the forwarding UPF (<NUM>, <NUM>) dedicated for data forwarding between a source cell (Cell-<NUM>, <NUM>) and a target cell (Cell-<NUM>, <NUM>) of a UE (UE-<NUM>, <NUM>);
receiving (<NUM>), from a Session Management Function, SMF, (<NUM>, <NUM>), a HTTP GET discovery request message comprising filter criteria included in query parameters which indicates that the SMF (<NUM>, <NUM>) searches for an UPF having a data forwarding function;
transmitting (<NUM>), to the SMF (<NUM>, <NUM>), a HTTP "<NUM> OK" response message comprising a validity period, during which the received search result can be cached by the SMF (<NUM>, <NUM>) and an array of Network Function, NF, Profile objects that satisfy the filter criteria.