Patent Description:
Currently, 2nd generation mobile communication technology/3rd generation mobile communication technology (2nd generation/3rd generation, <NUM>/<NUM>) networks have been widely deployed in many areas. As communications technologies develop rapidly, LTE (long term evolution, Long Term Evolution) networks and the like have covered some urban areas and traffic hotspot areas. In addition, new generation <NUM> (5th generation, 5th generation mobile communication technology) networks are being deployed. Therefore, the <NUM>, LTE, and <NUM>/<NUM> networks coexist in these areas in the future. In other words, in a relatively long period of time, networks of different systems (such as the <NUM>, <NUM>, LTE, and <NUM> networks) coexist and jointly provide services for users. In view of this, inter-system interworking is introduced on a network side. Interworking is an important guarantee for service continuity between different systems. Through inter-system interworking, an operator can implement complementation between networks of different systems, improving coverage of an existing network, and improving network quality.

In the prior art, after a handover (handover) from <NUM> to LTE is initiated, an access network device in the <NUM> network forwards all received flows to a user plane function (user plane function, UPF) network element, and the UPF network element forwards a flow that has a corresponding forwarding tunnel, and discards a flow that has no corresponding forwarding tunnel, causing a waste of transmission resources. <NPL>" discusses a procedure for Inter NG-RAN node N2 based handover. <NPL>" discusses the content of the Create Indirect Data Forwarding Tunnel Request/ Response messages. <CIT> discusses a solution for interworking with legacy radio access technologies for connectivity to next generation core network. <CIT> discusses a solution for interworking with bearer-based system.

In particular, the invention is based on the embodiments disclosed below with reference to <FIG> and <FIG>, <FIG> and <FIG>. Additional aspects and examples are disclosed in this application for illustrative purposes.

According to an aspect, this application provides a data forwarding method, and the method includes: receiving, by a session management function network element, information about a first bearer in a first network from an access and mobility management function network element; and sending flow information of a first flow (for example, a QoS flow) in a second network and forwarding information (which may also be referred to as tunnel information) to the access and mobility management function network element, where the flow information indicates a flow for data forwarding, and the forwarding information is used for forwarding the first flow to a tunnel corresponding to the first bearer. According to the foregoing solution, the session management function network element sends the flow information and the forwarding information to the access and mobility management function network element, and then the access and mobility management function network element provides the flow information and the forwarding information for an access network device in the second network. The access network device in the second network may send, to a user plane function network element based on the flow information and the forwarding information, only a flow required for data forwarding, so the access network device does not need to forward all flows to the user plane function network element, thereby reducing transmission resources.

In a possible design, the method further includes: determining, by the session management function network element, the first flow based on the information about the first bearer and association information, where the association information indicates an association between the first flow and the first bearer.

In a possible design, before the receiving, by a session management function network element, information about a first bearer in a first network from an access and mobility management function network element, the method further includes: receiving, by the session management function network element, a flow list from the access and mobility management function network element; determining, based on the flow list and association information, a bearer for data forwarding; and indicating, to the access and mobility management function network element, the bearer for data forwarding. The flow list includes the flow information. The bearer for data forwarding is associated with a flow in the flow list, and the bearer for data forwarding includes the first bearer. The foregoing steps are applicable to a scenario in which the access network device in the second network determines a flow for data forwarding.

In another possible design, before the receiving, by a session management function network element, information about a first bearer in a first network from an access and mobility management function network element, the method further includes: determining, by the session management function network element based on association information, a bearer for data forwarding; and indicating, to the access and mobility management function network element, the bearer for data forwarding. The bearer for data forwarding includes the first bearer. The foregoing steps are applicable to a scenario in which the session management function network element determines a flow for data forwarding.

In a possible design, the flow information further includes identification information of a second flow in the second network, and the forwarding information is used for forwarding the first flow to the tunnel corresponding to the first bearer and for forwarding the second flow to a tunnel corresponding to a second bearer. The first bearer and the second bearer may be a same bearer. In other words, the forwarding information is at a granularity of a session and may indicate forwarding information of flows in the session.

In another possible design, the flow information further includes identification information of a second flow in the second network, and the forwarding information includes first forwarding information and second forwarding information, where the first forwarding information is used for forwarding the first flow to the tunnel corresponding to the first bearer, and the second forwarding information is used for forwarding the second flow to a tunnel corresponding to a second bearer. The first bearer and the second bearer may be a same bearer. In other words, the forwarding information is at a granularity of a flow, and each flow has corresponding forwarding information. In this case, the method may further include: allocating, by the session management function network element, the first forwarding information to the first flow, and allocating the second forwarding information to the second flow. That is, the session management function network element allocates the forwarding information at a granularity of a flow.

In a possible design, the method further includes: determining, by the session management function network element, a data forwarding rule, and sending the data forwarding rule to a user plane function network element, where the data forwarding rule indicates that the tunnel corresponding to the first bearer is used for forwarding the first flow. In this case, the user plane function network element may forward, according to the forwarding rule, the first flow to the tunnel corresponding to the first bearer. In this way, a problem of how the user plane function network element forwards a flow in the second network to a bearer in the first network by is resolved.

According to another aspect, this application further discloses a data forwarding method, including: sending, by an access and mobility management function network element, information about a first bearer in a first network to a session management function network element; receiving flow information of a first flow in a second network and forwarding information from the session management function network element; and sending the flow information and the forwarding information to an access network device in the second network. The flow information indicates a flow for data forwarding, and the forwarding information is used for forwarding the first flow to a tunnel corresponding to the first bearer. According to the foregoing solution, after receiving the flow information and the forwarding information from the session management function network element, the access and mobility management function network element sends the flow information and the forwarding information to the access network device in the second network. The access network device in the second network may send, to a user plane function network element based on the flow information and the forwarding information, only a flow required for data forwarding, so the access network device does not need to forward all flows to the user plane function network element, thereby reducing transmission resources.

In a possible design, before the sending, by an access and mobility management function network element, information about a first bearer in a first network to a session management function network element, the method further includes: sending, by the access and mobility management function network element, a flow list to the session management function network element; learning, from the session management function network element, of a bearer for data forwarding; and indicating, to a core network control plane network element in the first network, the bearer for data forwarding. The flow list includes the flow information. The bearer for data forwarding is associated with a flow in the flow list, and the bearer for data forwarding includes the first bearer. For example, the access and mobility management function network element sends a request message to the core network control plane network element in the first network, where the request message includes information to be sent to an access network device in the first network, and the information to be sent to the access network device in the first network indicates the bearer for data forwarding. The information to be sent to the access network device in the first network may be a transparent container. The steps in this possible design are applicable to a scenario in which an access network device in the second network determines a flow for data forwarding. In a scenario in which the session management function network element determines a flow for data forwarding, the access and mobility management function network element may directly receive, from the session management function network element, the bearer for data forwarding, without sending the flow list to the session management function network element.

According to still another aspect, this application further discloses a data forwarding method, including: receiving, by an access network device in a second network, flow information of a first flow in the second network and forwarding information from an access and mobility management function network element; and receiving, by the access network device, the first flow, and sending the first flow to a user plane function network element based on the flow information and the forwarding information. The flow information indicates a flow for data forwarding, and the forwarding information is used for forwarding the first flow to a tunnel corresponding to a first bearer in a first network. According to the foregoing solution, after receiving the flow information and the forwarding information from the access and mobility management function network element, the access network device in the second network may send, to the user plane function network element based on the flow information and the forwarding information, only a flow required for data forwarding, so the access network device does not need to forward all flows to the user plane function network element, thereby reducing transmission resources.

In a possible design, the method further includes: determining, by the access network device, a list of flows for data forwarding; and sending, by the access network device, the flow list to the access and mobility management function network element, where the flow list is used to determine a bearer for data forwarding, the flow list includes the flow information, the bearer for data forwarding is associated with a flow in the flow list, and the bearer for data forwarding includes the first bearer. The foregoing steps are applicable to a scenario in which the access network device in the second network initiates determining of a flow for data forwarding.

In the foregoing aspects and possible designs, the forwarding information may be at a granularity of a session, or may be at a granularity of a flow.

According to still another aspect, this application provides a data forwarding apparatus, and the data forwarding apparatus has functions for implementing operations of the session management function network element in the foregoing methods. The function may be implemented by using hardware, or may be implemented by executing corresponding software by hardware. The hardware or the software includes one or more modules corresponding to the foregoing functions. In a possible design, a structure of the data forwarding apparatus includes a processor and a transceiver. The processor is configured to perform corresponding functions of the session management function network element in the foregoing methods, and the transceiver is configured to implement communication between the session management function network element and an access and mobility management function network element/a user plane function network element. The data forwarding apparatus may further include a memory. The memory is configured to be coupled to the processor, and the memory stores a necessary program instruction and data of the session management function network element.

According to still another aspect, this application provides a data forwarding apparatus, and the data forwarding apparatus has functions for implementing operations of the access and mobility management function network element in the foregoing methods. The function may be implemented by using hardware, or may be implemented by executing corresponding software by hardware. The hardware or the software includes one or more modules corresponding to the foregoing functions. In a possible design, a structure of the data forwarding apparatus includes a processor and a transceiver. The processor is configured to perform corresponding functions of the access and mobility management function network element in the foregoing methods, and the transceiver is configured to implement communication between the access and mobility management function network element and a session management function network element/an access network device in a second network/a core network control plane network element in a first network. The data forwarding apparatus may further include a memory. The memory is configured to be coupled to the processor, and the memory stores a necessary program instruction and data of the access and mobility management function network element.

According to still another aspect, this application provides a data forwarding apparatus, and the data forwarding apparatus has functions for implementing operations of the access network device in the second network in the foregoing methods. The function may be implemented by using hardware, or may be implemented by executing corresponding software by hardware. The hardware or the software includes one or more modules corresponding to the foregoing functions. In a possible design, a structure of the data forwarding apparatus includes a processor and a transceiver. The processor is configured to perform corresponding functions of the access network device in the second network in the foregoing methods, and the transceiver is configured to implement communication between the access network device in the second network and an access and mobility management function network element/a user plane function network element. The data forwarding apparatus may further include a memory. The memory is configured to be coupled to the processor, and the memory stores a necessary program instruction and data of the access network device in the second network.

According to still another aspect, this application provides a computer readable storage medium. The computer readable storage medium stores an instruction, and when the instruction runs on a computer, the computer performs the methods in the foregoing aspects.

According to still another aspect, this application provides a computer program product including an instruction, and when the instruction runs on a computer, the computer performs the methods in the foregoing aspects.

According to still another aspect, this application provides a chip system, and the chip system includes a processor, configured to support the foregoing session management function network element/access and mobility management function network element/access network device in the second network in implementing the functions in the foregoing aspects, for example, generating or processing the information in the foregoing aspects. In a possible design, the chip system further includes a memory, and the memory is configured to store a necessary program instruction and data of a data forwarding apparatus. The chip system may include a chip, or may include a chip and another discrete device.

The following briefly describes the accompanying drawings required for describing the embodiments.

The following clearly describes the technical solutions in the aspects of this application with reference to the accompanying drawings in the aspects of this application.

A terminal in this application may include a handheld device having a wireless communication function, an in-vehicle device, a wearable device, a computing device, or another processing device connected to a wireless modem, user equipment (user equipment, UE) in various forms, a mobile station (mobile station, MS), a terminal (terminal), a terminal device (terminal equipment), and the like. For ease of description, in the aspects of this application, an example in which the terminal is UE is used for description.

A data forwarding method in the aspects of this application is applicable to various system architectures. <FIG> is a schematic diagram of an architecture of a non-roaming scenario in which interworking is performed between a <NUM> system and a <NUM> system and to which an aspect of this application is applicable.

As shown in <FIG>, the <NUM> system in the system architecture includes an evolved universal terrestrial radio access network (evolved universal terrestrial radio access network, E-UTRAN), a mobility management entity (mobility management entity, MME), a serving gateway (serving gateway, SGW), a packet data network gateway control plane (packet data network gateway control plane, PDN gateway control plane, PGW-C), a packet data network gateway user plane (packet data network gateway user plane, PDN gateway user plane, PGW-U), a policy and charging rules function (policy and charging rules function, PCRF), and a home subscriber server (Home Subscriber Server, HSS). There is an S1-MME interface between the E-UTRAN and the MME. There is an S1-U interface between the E-UTRAN and the SGW. There is an S11 interface between the MME and the SGW. There is an S5-C interface between the SGW and the PGW-C. There is an S5-U interface between the SGW and the PGW-U.

The <NUM> system includes a next generation radio access network (Next Generation radio access network, NG-RAN, also referred to as a <NUM> access network, <NUM> RAN), an access and mobility management function (access and mobility management function, AMF) network element, a user plane function (user plane function, UPF) network element, a session management function (session management function, SMF) network element, a policy control function (Policy Control Function, PCF) network element, and a unified data management (unified data management, UDM) network element. There is an N2 interface between the NG-RAN and the AMF. There is an N3 interface between the NG-RAN and the UPF. There is an N11 interface between the AMF and the SMF.

When interworking (interworking) is required between the <NUM> system and the <NUM> system, as shown in <FIG>, the UPF and the PGW-U may be integrated, and may be referred to as a UPF+PGW-U after they are integrated. Similarly, the SMF and the PGW-C may be integrated, and may be referred to as a PGW-C+SMF after they are integrated. There is an N26 interface between the AMF in the <NUM> system and the MME in the <NUM> system. The N26 interface is used for interworking between an evolved packet core (evolved packet core, EPC) and an NG core (Next Generation Core). For example, the AMF can select a target MME, and send a context (for example, MM context information and SM context information) of UE to the target MME by using the N26 interface, to implement a handover from the <NUM> system to the <NUM> system.

In the following descriptions, a first network is a <NUM> network in the scenario in which interworking is performed between the <NUM> system and the <NUM> system, that is, a network including the UE, the E-UTRAN, the MME, the SGW, the PGW-C, and the PGW-U in <FIG>; and a second network is a <NUM> network in the scenario in which interworking is performed between the <NUM> system interworks and the <NUM> system, that is, a network including the UE, the NG-RAN, the AMF, the SMF, and the UPF in <FIG>. In addition, the first network may include another network element in the <NUM> system, and the second network may include another network element in the <NUM> system. This is not limited in the present invention.

<FIG> is a schematic diagram of a data forwarding method according to an embodiment of the present invention. In an example in <FIG>, the data forwarding method relates to interaction between an access network device, an access and mobility management function network element, and a session management function network element.

The access network device in this embodiment of this application is an access network device in a second network. For example, the access network device may be the NG-RAN in <FIG>. The access network device may include various forms of base stations, such as a macro base station, a micro base station (also referred to as a small cell), a relay station, and an access point. For example, the access network device may be a gNB (gNodeB).

The access and mobility management function network element in this embodiment of this application may be the AMF network element in <FIG>, and is responsible for UE registration, mobility management, a tracking area update procedure, and the like. For ease of description, the AMF network element may be referred to as the "AMF" for short below.

The session management function network element in this embodiment of this application may be the SMF network element in <FIG>, and is responsible for UE session management, selection of a user plane function network element, reselection of a user plane function network element, IP address allocation, QoS control, and session establishment, modification, and release. For ease of description, the SMF network element may be referred to as the "SMF" for short below.

The access network device, the access and mobility management function network element, and the session management function network element may be implemented by using specified hardware, may be implemented by using a software instance on specified hardware, or may be implemented by using a virtual function instantiated on an appropriate platform. This is not limited herein in the present invention.

The data forwarding method according to this embodiment of this application is described below with reference to <FIG>.

Step <NUM>: The access and mobility management function network element sends information about a first bearer in a first network to the session management function network element, and correspondingly, the session management function network element receives the information about the first bearer from the access and mobility management function network element.

For example, in step <NUM>, the access and mobility management function network element sends information about at least one bearer in the first network to the session management function network element. The at least one bearer includes the first bearer.

Optionally, the information about the first bearer may be represented by using tunnel information of the GPRS tunneling protocol (GPRS tunneling protocol, GTP) of <NUM> For example, the information about the first bearer is SGW information. The SGW information includes a tunnel endpoint identifier (tunnel endpoint identifier, TEID) of an SGW. For example, the TEID of the SGW may be an SGW TEID (which may be referred to as an SGW F-TEID) used for forwarding downlink data. Optionally, the SGW information may further include an address of the SGW.

Alternatively, optionally, the information about the first bearer may be identification information of the first bearer. For example, the identification information of the first bearer may be an evolved packet system bearer identifier (evolved packet system bearer identifier, EPS bearer ID).

Alternatively, optionally, the information about the first bearer may be a combination of the SGW information and the identification information of the first bearer.

For example, the access and mobility management function network element may obtain the information about the first bearer from an MME of <NUM> by using an N26 interface. This is described in detail with reference to <FIG> and <FIG>. After obtaining the information about the first bearer, the access and mobility management function network element sends the information about the first bearer to the session management function network element.

Step <NUM>: The session management function network element determines a first flow in a second network based on the information about the first bearer and association information, where the association information indicates an association between the first flow and the first bearer.

The first flow in the second network may be a quality of service (quality of service, QoS) flow (QoS flow) of <NUM>. The first flow is a flow for data forwarding.

For example, the association between the first flow and the first bearer means that data may be indirectly forwarded on the first flow in the <NUM> system by using a tunnel corresponding to the first bearer in the <NUM> system. For example, as shown in <FIG>, data between an NG-RAN and a UPF in the <NUM> system is transmitted in a form of a QoS flow. In the <NUM> system, a different transmission manner is used. Specifically, an S5/S8 bearer may be used for data transmission between a PGW-U and an SGW, and an S <NUM> bearer may be used for data transmission between the SGW and an E-UTRAN. Therefore, during a handover from the <NUM> system to the <NUM> system, the QoS flow needs to be forwarded to the tunnel corresponding to the first bearer (the S5/S8 bearer or the S1 bearer) in the <NUM> system. Therefore, there is the association (or referred to as a correspondence) between the first flow and the first bearer. For example, in a process of establishing a packet data unit (packet data unit, PDU) session and a QoS flow, the session management function network element may perform mapping between a bearer and a QoS flow, to obtain a correspondence between each flow and each bearer (including the correspondence between the first flow and the first bearer).

For example, in a possible implementation, the association information includes an association between bearer information (for example, the bearer information is an SGW TEID), a bearer identifier, and a flow. For example, the association information is in a form shown in Table <NUM>.

As shown in Table <NUM>, the SGW TEID1 is bearer information of the bearer <NUM>, and the bearer <NUM> is corresponding to the flow A. The SGW TEID2 is bearer information of the bearer <NUM>, and the bearer <NUM> is corresponding to the flow B. Assuming that the information, received by the session management function network element, about the first bearer is the SGW TEID1, the session management function network element may determine, based on the association information, that a flow that is in the second network and that is corresponding to the first bearer is the flow A.

In another possible implementation, the association information includes an association between bearer information (for example, the bearer information is an EPS bearer ID) and a flow. For example, the association information is in a form shown in Table <NUM>.

As shown in Table <NUM>, the EPS bearer ID1 is bearer information of a bearer <NUM>, and the bearer <NUM> is corresponding to the flow A. The EPS bearer ID2 is bearer information of a bearer <NUM>, and the bearer <NUM> is corresponding to the flow B. Assuming that the information, received by the session management function network element, about the first bearer is the EPS bearer ID1, the session management function network element may determine, based on the association information, that a flow that is in the second network and that is corresponding to the first bearer is the flow A.

After the session management function network element determines the first flow, flow information of the first flow and forwarding information may be determined.

The flow information indicates a flow for data forwarding (that is, indicate that the first flow is a flow required for data forwarding). In other words, the flow information may be used to determine a specific flow for data forwarding. This is further described with reference to step <NUM>. Optionally, the flow information of the first flow may include a QoS flow identifier (QoS flow identifier, QFI) of the first flow.

The forwarding information is used for forwarding the first flow to the tunnel corresponding to the first bearer. The forwarding information may also be referred to as tunnel information. For example, the forwarding information may be used to identify a user plane function network element, and the user plane function network element is configured to forward the first flow to the tunnel corresponding to the first bearer. Optionally, the forwarding information is core network tunnel information for data forwarding (CN tunnel information for data forwarding). The forwarding information may be allocated by the session management function network element, or allocated by the user plane function network element. This is further described with reference to <FIG> and <FIG>.

A session in the <NUM> system may include a plurality of flows requiring data forwarding (the plurality of flows include the first flow). In a possible implementation, the forwarding information may include a QFI of each of the plurality of flows. For example, the flow information further includes identification information of a second flow in the second network. The forwarding information is used for forwarding the first flow to the tunnel corresponding to the first bearer and for forwarding the second flow to a tunnel corresponding to a second bearer. The second bearer and the first bearer may be a same bearer or different bearers. In this case, the forwarding information is forwarding information at a granularity of a session.

In another possible implementation, each of the plurality of flows has forwarding information dedicated to the flow, that is, the forwarding information includes a QFI of a flow. For example, the flow information further includes identification information of a second flow in the second network. The forwarding information includes first forwarding information and second forwarding information. The first forwarding information is used for forwarding the first flow to the tunnel corresponding to the first bearer, and the second forwarding information is used for forwarding the second flow to a tunnel corresponding to a second bearer. For example, the session management function network element allocates the first forwarding information to the first flow, and allocates the second forwarding information to the second flow. Similarly, the second bearer and the first bearer may be a same bearer or different bearers. In this case, the forwarding information is forwarding information at a granularity of a flow. In addition, the forwarding information may be at another granularity. This is not limited herein in the present invention.

Step <NUM> is an optional step. The session management function network element may alternatively obtain the flow information of the first flow and the forwarding information in another manner. This is not limited herein in the present invention.

Step <NUM>: The session management function network element sends flow information and forwarding information to the access and mobility management function network element, and correspondingly, the access and mobility management function network element receives the flow information and the forwarding information from the session management function network element.

Step <NUM>: The access and mobility management function network element sends the flow information and the forwarding information to an access network device in the second network, and correspondingly, the access network device in the second network receives the flow information and the forwarding information from the access and mobility management function network element.

Step <NUM>: The access network device in the second network receives the first flow.

For example, the access network device receives the first flow from a first user plane function network element.

Step <NUM>: The access network device sends the first flow to a user plane function network element based on the flow information and the forwarding information.

For example, if the access network device determines, based on the flow information, that the first flow is a flow for data forwarding, the access network device sends the first flow to a second user plane function network element based on the forwarding information, so that the second user plane function network element forwards the first flow to the tunnel corresponding to the first bearer. In other words, the flow information may be used to determine a specific flow required for data forwarding, that is, the flow information may be used to select, from flows received by the access network device, a flow required for data forwarding.

For example, a plurality of flows received by the access network device in step <NUM> include the first flow, the second flow, and a third flow. If the flow information received by the access network device in step <NUM> includes flow information of the first flow and flow information of the second flow, the access network device determines that the first flow and the second flow are flows for data forwarding. Because the flow information does not include flow information of the third flow, the access network device determines that the third flow is not a flow for data forwarding.

As shown in <FIG>, the access network device (NG-RAN) receives the first flow from the first user plane function network element (PGW-U+UPF) in step a, and after determining that the first flow is a flow for data forwarding, sends the first flow to the second user plane function network element (PGW-U+UPF) in step b, so that the second user plane function network element forwards the first flow to the tunnel corresponding to the first bearer (that is, the first flow is forwarded to an SGW in step c, and the first flow is forwarded to an E-UTRAN in step d), to forward downlink data. Therefore, a forwarding path of a flow for data forwarding is a→b→c→d, and this is specifically as follows:.

It should be noted that the first user plane function network element and the second user plane function network element may be a same user plane function network element or different user plane function network elements. This is not limited herein in the present application.

Therefore, according to the data forwarding method in this aspect of this application, the session management function network element sends the flow information and the forwarding information to the access and mobility management function network element, and then the access and mobility management function network element provides the flow information and the forwarding information for the access network device in the second network. The access network device in the second network may send, to the user plane function network element based on the flow information and the forwarding information, only a flow required for data forwarding, so the access network device does not need to forward all flows to the user plane function network element, thereby reducing transmission resources.

Optionally, the method further includes: determining, by the session management function network element, a data forwarding rule, and sending the data forwarding rule to the user plane function network element (for example, the second user plane function network element), where the data forwarding rule indicates that the tunnel corresponding to the first bearer is used for forwarding the first flow. In this way, a problem of how the user plane function network element forwards a flow in the second network to a bearer in the first network by is resolved. This is further described with reference to <FIG>, <FIG>, and <FIG>.

In a possible implementation, the access network device in the second network may initially determine a flow for data forwarding. In this scenario:.

A method on the access network device side includes: determining, by the access network device, a list of flows for data forwarding, where the flow list is used to determine a bearer for data forwarding; and sending the flow list to the access and mobility management function network element.

Correspondingly, before the access and mobility management function network element sends the information about the first bearer to the session management function network element, a method on the access and mobility management function network element side further includes: receiving, by the access and mobility management function network element, the flow list from the access network device, and sending the flow list to the session management function network element; learning, by the access and mobility management function network element from the session management function network element, of the bearer for data forwarding; and indicating, by the access and mobility management function network element to a core network control plane network element in the first network, the bearer for data forwarding.

Correspondingly, before the session management function network element receives the information about the first bearer from the access and mobility management function network element, a method on the session management function network element side further includes: receiving, by the session management function network element, the flow list from the access and mobility management function network element; determining, based on the flow list and association information, the bearer for data forwarding; and indicating, to the access and mobility management function network element, the bearer for data forwarding.

The flow list includes the flow information. The bearer for data forwarding is associated with a flow in the flow list, and the bearer for data forwarding includes the first bearer. Operations in this scenario are further described with reference to <FIG>.

In another possible implementation, the session management function network element may initially determine a flow for data forwarding. In this scenario:
Before the session management function network element receives the information about the first bearer from the access and mobility management function network element, a method on the session management function network element side further includes: determining, by the session management function network element based on association information, a bearer for data forwarding; and indicating, to the access and mobility management function network element, the bearer for data forwarding.

Correspondingly, before the access and mobility management function network element sends the information about the first bearer to the session management function network element, a method on the access and mobility management function network element side further includes: learning, by the access and mobility management function network element from the session management function network element, of the bearer for data forwarding; and indicating, to a core network control plane network element in the first network, the bearer for data forwarding.

The bearer for data forwarding includes the first bearer. Operations in this scenario are further described with reference to <FIG>.

In the foregoing two scenarios, the indicating, by the access and mobility management function network element to a core network control plane network element in the first network, the bearer for data forwarding includes: sending, by the access and mobility management function network element, a request message to the core network control plane network element in the first network, where the request message includes information to be sent to an access network device in the first network, and the information to be sent to the access network device in the first network indicates the bearer for data forwarding. For example, the information to be sent to the access network device in the first network is a transparent container. This is further described with reference to <FIG> and <FIG>.

<FIG> and <FIG> are a signaling interaction diagram of a data forwarding method according to an embodiment of the present invention. <FIG> and <FIG> relate to interaction between UE, an access network device in a first network, a core network control plane function network element, an access network device in a second network, an access and mobility management function network element, a session management function network element obtained through integration of network elements in the first network and the second network, and a user plane function network element. In <FIG> and <FIG>, description is provided by using an example in which the access network device in the first network is the E-UTRAN, the core network control plane function network element is the MME, the access network device in the second network is the NG-RAN, the access and mobility management function network element is the AMF, the session management function network element obtained through integration of network elements in the first network and the second network is the PGW-C+SMF, and the user plane function network element is the PGW-U+UPF. As shown in <FIG> and <FIG>, the method includes the following steps.

Step <NUM>: Establish a PDU session and one or more QoS flows through interaction in a <NUM> network, where in this process, the SMF maps the one or more QoS flows to one or more EPS bearers in a <NUM> network, to obtain associations between the one or more QoS flows and the one or more EPS bearers.

Step <NUM>: The NG-RAN determines that the UE should be handed over to the E-UTRAN. For example, when a new wireless condition or load balancing requirement or a specific QoS flow requirement is generated, the NG-RAN triggers a handover to the <NUM> network. The NG-RAN sends a handover required (Handover Required) message to the AMF. The handover required message includes an identifier of a target base station (for example, a target eNB ID) in the <NUM> network.

Step 402a: The AMF learns, based on the identifier that is of the target base station in the <NUM> network and that is carried in a handover required message, that the handover is a handover to the E-UTRAN, and sends an SM context request (SM Context Request) message to the PGW-C+SMF corresponding to the UE, to request a session management context (session management context, SM Context).

Step 402b: The AMF receives, from the PGW-C+SMF, an SM context response (SM Context Response) message including the SM context.

Step <NUM>: The AMF selects an MME, and sends a relocation request (Relocation Request, which may also be referred to as a reconfiguration request) message to the MME, where the relocation request message carries the identifier of the target base station in the <NUM> network and the SM context.

Step <NUM>: The MME selects an SGW, and sends a create session request (Create Session Request) message to the SGW.

Step <NUM>: The SGW allocates a local resource, and returns a create session response (Create Session Response) message to the MME.

Step <NUM>: The MME sends a handover request (Handover Request) message to the target base station in the E-UTRAN based on the identifier of the target base station in the <NUM> network, where the handover request message carries an identifier of an EPS bearer that needs to be established, to request to establish the EPS bearer.

Step <NUM>: The target base station in the E-UTRAN allocates a resource, and returns a handover request acknowledgement (Handover Request Ack) message to the MME, where the handover request acknowledgement message includes an EPS Bearers setup list (EPS Bearers setup list) and an EPS Bearers failed to setup list (EPS Bearers failed to setup list). In other words, it is possible that in EPS bearers that the MME requests the E-UTRAN to establish, only one or some EPS bearers are successfully established, and the other EPS bearer(s) fail to be established.

Step <NUM>: If the MME determines to forward data (that is, forward downlink data based on the forwarding path shown in <FIG>), the MME sends a create indirect data forwarding tunnel request (Create Indirect Data Forwarding Tunnel Request) message to the SGW, where the message carries identification information of the target base station in the E-UTRAN, which is used for downlink data forwarding. For example, the identification information of the target base station in the E-UTRAN, which is used for downlink data forwarding, includes a TEID of the target base station in the E-UTRAN. Optionally, the identification information of the target base station in the E-UTRAN, which is used for downlink data forwarding, further includes an address of the target base station in the E-UTRAN.

The SGW returns a create indirect data forwarding tunnel response (Create Indirect Data Forwarding Tunnel Response) message to the MME. The message carries SGW information used for downlink data forwarding. For example, the SGW information used for downlink data forwarding includes a TEID of the SGW. Optionally, the SGW information used for downlink data forwarding further includes an address of the SGW.

Step <NUM>: The MME sends a relocation response (Relocation Response, which may also be referred to as a reconfiguration response) message to the AMF, where the relocation response message carries the SGW information used for downlink data forwarding.

Step 410a: If data is to be forwarded, the AMF sends a create indirect data forwarding tunnel request message to the PGW-C+SMF, where the message carries the SGW information used for downlink data forwarding (that is, information about a successfully established EPS bearer, and the successfully established EPS bearer includes the first bearer).

Step 410b: The PGW-C+SMF sends, to the PGW-U+UPF, the SGW information used for downlink data forwarding. For example, the PGW-C+SMF interacts with the PGW-U+UPF, and sends, in an N4 session modification (N4 Session Modification) process, to the PGW-U+UPF, the SGW information used for downlink data forwarding. Similarly, the SGW information includes the TEID of the SGW. For example, the TEID of the SGW may be an SGW TEID (which may be referred to as an SGW F-TEID) used for downlink data forwarding. Optionally, the SGW information may further include the address of the SGW.

In step 410b, core network tunnel information for data forwarding (CN tunnel information for data forwarding) is also allocated. In a possible implementation, the core network tunnel information for data forwarding is allocated by the PGW-C+SMF. The PGW-C+SMF sends, to the PGW-U+UPF, the allocated core network tunnel information for data forwarding, and the PGW-U+UPF returns a response to the PGW-C+SMF. In another possible implementation, the core network tunnel information for data forwarding is allocated by the PGW-U+UPF, and is provided for the PGW-C+SMF by using a response message.

The allocated core network tunnel information for data forwarding may be used as the forwarding information. The information may be at a granularity of a session, or may be at a granularity of a flow. Details are not repeated herein.

Step 410c: The PGW-C+SMF determines a flow for data forwarding (including the first flow), based on the information about the successfully established EPS bearer (the SGW information used for downlink data forwarding) that is obtained in step 410a and the association, obtained in step <NUM>, between the QoS flow and the EPS bearer. That is, the PGW-C+SMF maps the information about the successfully established EPS bearer (the SGW information used for downlink data forwarding) that is obtained in step 410a to the flow for data forwarding (including the first flow), based on the association, obtained in step <NUM>, between the QoS flow and the EPS bearer.

The PGW-C+SMF returns a create indirect data forwarding tunnel response message to the AMF. The message carries flow information of the flow for data forwarding (including the first flow) and the core network tunnel information for data forwarding (the forwarding information).

Step 411a: The AMF sends a handover command (Handover Command) message to the NG-RAN, where the message carries the flow information of the flow for data forwarding (including the first flow) and the core network tunnel information for data forwarding (namely, the forwarding information). For a QoS flow indicated in the flow information, the NG-RAN sends the QoS flow to the PGW-U+UPF. For a QoS flow not included in the flow information, the NG-RAN does not send the QoS flow to the PGW-U+UPF.

Step 411b: The NG-RAN sends the handover command message to the UE.

At this time, the downlink data (for example, the first flow) is transmitted by using the forwarding path: a→b→c→d shown in <FIG>, that is, PGW-U+UPF→NG-RAN→PGW-U+UPF→SGW→E-UTRAN.

Step 412a: After the UE successfully accesses the target base station in the E-UTRAN, the UE sends a handover complete (Handover Complete) message to the E-UTRAN.

Step 412b: The E-UTRAN sends a handover notify (Handover Notify) message to the MME.

Step <NUM>: The MME sends a modify bearer request (Modify Bearer Request) message to the SGW, to notify the SGW that the MME is responsible for one or more bearers established by the UE. For an EPS bearer that fails to be established, the MME releases a context of the EPS bearer.

Step 414a: The SGW sends the modify bearer request message to the PGW-C+SMF.

Step 414b, the PGW-C+SMF interacts with the PGW-U+UPF to implement Sx session modification (Sx Session Modification). The PGW-U+UPF deletes a QoS flow to which no EPS bearer ID is allocated. Optionally, the PGW-U+UPF maps the deleted QoS flow to a default QoS flow.

Step <NUM>: The PGW-C+SMF sends a modify bearer response (Modify Bearer Response) message to the SGW.

At this time, a user plane path between the UE, the E-UTRAN, the SGW, and the PGW-U+UPF (which may also be referred to as a path of normal downlink data, that is, a'→b' in <FIG>) is established.

Step <NUM>: The SGW sends the modify bearer response to the MME, to acknowledge a handover to a user plane path. That is, the downlink data is transmitted by using the path PGW-U+UPF→SGW→E-UTRAN.

Optionally, when a flow for data forwarding is corresponding to a plurality of bearers, one or more tunnels may be used to implement forwarding. For example, the plurality of bearers may form a tunnel for forwarding, or each of the plurality of bearers forms a tunnel for forwarding. This is not limited herein in the present invention.

Optionally, in step 410b, the PGW-C+SMF further determines a data forwarding rule, and sends the data forwarding rule to the PGW-U+UPF. The data forwarding rule indicates that a tunnel corresponding to the first bearer is used for forwarding the first flow. Therefore, after receiving a flow for data forwarding, the PGW-U+UPF may determine, according to the forwarding rule, a bearer corresponding to the flow, and further forward the flow by using a tunnel corresponding to the bearer.

<FIG> is another signaling interaction diagram of a data forwarding method according to an aspect of the present application. <FIG> is applicable to a scenario in which an NG-RAN determines a flow for data forwarding. <FIG> is described with reference to <FIG> and <FIG>.

Step <NUM>: The NG-RAN determines that the UE should be handed over to the E-UTRAN. For example, when a new wireless condition or load balancing requirement or a specific QoS flow requirement is generated, the NG-RAN triggers a handover to the <NUM> network.

In addition, the NG-RAN determines a list of flows for data forwarding. For example, the NG-RAN may obtain, from the SMF, QoS information (QoS profiles) of the flows, and determine, based on the QoS information, a specific flow required for data forwarding, to generate the list of flows for data forwarding. The one or more flows in the flow list are the one or more flows for data forwarding. For example, the flow list includes QFIs of the one or more flows for data forwarding.

The NG-RAN sends a handover required message to the AMF. The handover required message includes an identifier of a target base station in the <NUM> network, information to be sent to the target base station, and the list of flows for data forwarding. The information to be sent to the target base station may be a transparent container (Transparent Container). More specifically, the information to be sent to the target base station may be a source to target transparent container (Source to Target Transparent Container).

Step 502a: The AMF learns, based on an identifier that is of a target base station in the <NUM> network and that is carried in a handover required message, that the handover is a handover to the E-UTRAN, and sends, to the PGW-C+SMF corresponding to the UE, an SM context request message carrying a flow list, to request an SM context.

Step 502b: The PGW-C+SMF determines one or more bearers for data forwarding, based on the flow list and the associations, obtained in step <NUM>, between the one or more QoS flows and the one or more EPS bearers. The one or more bearers for data forwarding are associated with the one or more flows in the flow list in a one-to-one manner.

Step 502c: The AMF receives, from the PGW-C+SMF, an SM context response message including the SM context. The PGW-C+SMF may further indicate, to the AMF by using the SM context response message, the one or more bearers for data forwarding.

Step <NUM>: The AMF selects an MME, and sends a relocation request message to the MME, where the relocation request message carries the identifier of the target base station in the <NUM> network and the SM context.

The AMF may further indicate, to the MME by using the relocation request message, the one or more bearers for data forwarding. For example, the relocation request message carries the information to be sent to the target base station, and the information to be sent to the target base station may indicate the one or more bearers for data forwarding. For example, the AMF inserts, into the information to be sent to the target base station, related information of the one or more bearers for data forwarding. Therefore, the information to be sent to the target base station includes the related information of the one or more bearers for data forwarding.

Step <NUM>: The MME selects an SGW, and sends a create session request message to the SGW.

Step <NUM>: The SGW allocates a local resource, and returns a create session response message to the MME.

Step <NUM>: The MME sends a handover request message to the target base station in the E-UTRAN based on the identifier of the target base station in the <NUM> network, where the handover request message carries information to be sent to the target base station. That is, the MME indicates, to the E-UTRAN, the one or more bearers for data forwarding. After receiving the information to be sent to the target base station, the target base station in the E-UTRAN obtains, from the information to be sent to the target base station, the related information of the one or more bearers for data forwarding, and further allocates specific tunnel identifiers to the one or more bearers for data forwarding.

Steps <NUM> to 511b are similar to steps <NUM> to 411b in <FIG> and <FIG>. Reference may be made to the description of <FIG> and <FIG>, and details are not repeated herein.

It should be noted that, in the example in <FIG>, the NG-RAN first determines the list of flows for data forwarding, and the PGW-C+SMF maps, based on association information, the one or more flows to the one or more bearers for data forwarding. The one or more bearers for data forwarding are finally transmitted to the target base station in the E-UTRAN through the PGW-C+SMF, the AMF, and the MME, and the target base station in the E-UTRAN determines specific bearers, in these bearers for data forwarding, that can be successfully established. These bearers that are required for data forwarding and that are successfully established are transmitted to the PGW-C+SMF by using steps <NUM>, <NUM>, and 510a, and the PGW-C+SMF maps again, based on the association information, the bearers to one or more flows that can finally implement data forwarding. Therefore, the PGW-C+SMF performs mapping twice, and the flows obtained after the final mapping may be a subset of the list, determined by the NG-RAN, of flows for data forwarding. In other words, the flow list includes the first flow, and the one or more bearers for data forwarding that are determined in step 502b include the first bearer.

In addition, the target base station in the E-UTRAN allocates tunnel identifiers based on the one or more bearers for data forwarding that are indicated by the MME. In the prior art, the target base station in the E-UTRAN uses one tunnel identifier to receive forwarded data and normal downlink data. Consequently, a disorder may occur after a path handover, causing degradation of transmission performance. However, in the present application, the target base station in the E-UTRAN allocates the tunnel identifiers based on the one or more bearers for data forwarding that are indicated by the MME. In this way, forwarded downlink data and normal downlink data are differentiated from each other by using different tunnel identifiers, thereby avoiding a disorder of downlink data.

<FIG> is still another signaling interaction diagram of a data forwarding method according to an aspect of the present application. <FIG> is applicable to a scenario in which a PGW-C+SMF determines a flow for data forwarding. <FIG> is described with reference to <FIG>, <FIG>, and <FIG>.

Step <NUM>: The NG-RAN determines that the UE should be handed over to the E-UTRAN. For example, when a new wireless condition or load balancing requirement or a specific QoS flow requirement is generated, the NG-RAN triggers a handover to the <NUM> network. The NG-RAN sends a handover required message to the AMF. The handover required message includes an identifier of a target base station in the <NUM> network and information to be sent to the target base station. The information to be sent to the target base station may be a transparent container. More specifically, the information to be sent to the target base station may be a source to target transparent container.

Step 602a: The AMF learns, based on an identifier that is of a target base station in the <NUM> network and that is carried in a handover required message, that the handover is a handover to the E-UTRAN, and sends an SM context request message to the PGW-C+SMF corresponding to the UE, to request an SM context.

Step 602b: The PGW-C+SMF determines a list of flows for data forwarding. For example, the PGW-C+SMF stores QoS information (QoS profiles) of the flows, and determines, based on the QoS information, flows required for data forwarding, to generate the list of flows for data forwarding. The one or more flows in the flow list are the one or more flows for data forwarding. For example, the flow list includes QFIs of the one or more flows for data forwarding.

The PGW-C+SMF determines one or more bearers for data forwarding, based on the flow list and the associations, obtained in step <NUM>, between the one or more QoS flows and the one or more EPS bearers. The one or more bearers for data forwarding are associated with the one or more flows in the flow list in a one-to-one manner.

Steps 602c to <NUM> are similar to steps 502c to <NUM> in <FIG>. Reference may be made to the description of <FIG>, and details are not repeated herein.

Steps <NUM> to 611b are similar to steps <NUM> to 411b in <FIG> and <FIG>. Reference may be made to the description of <FIG> and <FIG>, and details are not repeated herein.

It should be noted that, in the example in <FIG>, the PGW-C+SMF first determines the list of flows for data forwarding, and maps, based on association information, the one or more flows to the one or more bearers for data forwarding. The one or more bearers for data forwarding are finally transmitted to the target base station in the E-UTRAN through the PGW-C+SMF, the AMF, and the MME, and the target base station in the E-UTRAN determines specific bearers, in these bearers for data forwarding, that can be successfully established. These bearers that are required for data forwarding and that are successfully established are transmitted to the PGW-C+SMF by using steps <NUM>, <NUM>, and 610a, and the PGW-C+SMF maps again, based on the association information, the bearers to one or more flows that can finally implement data forwarding. Therefore, the PGW-C+SMF performs mapping twice, and the flows obtained after the final mapping may be a subset of the list, determined by the PGW-C+SMF, of flows for data forwarding. In other words, the flow list includes the first flow, and the one or more bearers for data forwarding that are determined in step 602b include the first bearer.

It should be noted that the messages in <FIG> may have other names. In addition, information transmission between the network elements may also be implemented by invoking network functions of the network elements in a service-oriented architecture. This is not limited herein in the present invention.

In the foregoing aspects provided in this application, solutions such as the data forwarding method provided in the aspects of this application are described from perspectives of the network elements and interaction between the network elements. It can be understood that, to implement the foregoing functions, the network element such as the session management function network element, the access and mobility management function network element, or the access network device includes corresponding hardware structures and/or software modules for implementing the functions. A person skilled in the art may be easily aware that, units and algorithm steps of each example described with reference to the aspects disclosed in this specification can be implemented in a form of hardware or a form of a combination of hardware and computer software in this application. Whether the functions are implemented by hardware or computer software driving hardware depends on particular applications and design constraint conditions of the technical solutions.

For example, when the foregoing network elements implement the corresponding functions by using software modules, as shown in <FIG>, a session management function network element may include a receiving module <NUM>, a processing module <NUM>, and a sending module <NUM>. The session management function network element may be configured to perform operations of the session management function network element or the PGW-C+SMF in <FIG> and <FIG> to <FIG>. For example:.

The receiving module <NUM> is configured to receive information about a first bearer in a first network from an access and mobility management function network element. The sending module <NUM> is configured to send flow information of a first flow in a second network and forwarding information to the access and mobility management function network element. The flow information indicates a flow for data forwarding, and the forwarding information is used for forwarding the first flow to a tunnel corresponding to the first bearer.

Therefore, the session management function network element sends the flow information and the forwarding information to the access and mobility management function network element, and then the access and mobility management function network element provides the flow information and the forwarding information for an access network device in the second network. The access network device in the second network may send, to a user plane function network element based on the flow information and the forwarding information, only a flow required for data forwarding, so the access network device does not need to forward all flows to the user plane function network element, thereby reducing transmission resources.

Optionally, the processing module <NUM> is configured to determine the first flow based on the information about the first bearer and association information. The association information indicates an association between the first flow and the first bearer.

Optionally, before receiving the information about the first bearer in the first network from the access and mobility management function network element, the receiving module <NUM> is further configured to receive a flow list from the access and mobility management function network element, where the flow list includes the flow information; the processing module <NUM> is further configured to determine, based on the flow list and the association information, a bearer for data forwarding, where the bearer for data forwarding is associated with a flow in the flow list, and the bearer for data forwarding includes the first bearer; and the sending module <NUM> is further configured to indicate, to the access and mobility management function network element, the bearer for data forwarding.

Optionally, before the information about the first bearer in the first network is received from the access and mobility management function network element, the processing module <NUM> is further configured to determine, based on the association information, a bearer for data forwarding, where the bearer for data forwarding includes the first bearer; and the sending module <NUM> is further configured to indicate, to the access and mobility management function network element, the bearer for data forwarding.

Optionally, before the information about the first bearer in the first network is received from the access and mobility management function network element, the processing module <NUM> is further configured to: determine a flow list, where the flow list includes the flow information; and determine, based on the flow list and the association information, a bearer for data forwarding, where the bearer for data forwarding includes the first bearer; and the sending module <NUM> is further configured to indicate, to the access and mobility management function network element, the bearer for data forwarding.

In a possible implementation, the flow information further includes identification information of a second flow in the second network, and the forwarding information is used for forwarding the first flow to the tunnel corresponding to the first bearer and for forwarding the second flow to a tunnel corresponding to a second bearer.

In another possible implementation, the flow information further includes identification information of a second flow in the second network, and the forwarding information includes first forwarding information and second forwarding information. The first forwarding information is used for forwarding the first flow to the tunnel corresponding to the first bearer, and the second forwarding information is used for forwarding the second flow to a tunnel corresponding to a second bearer. Further, optionally, the processing module <NUM> is configured to: allocate the first forwarding information to the first flow, and allocate the second forwarding information to the second flow.

Optionally, the processing module <NUM> is further configured to determine a data forwarding rule, and the sending module <NUM> is further configured to send the data forwarding rule to a user plane function network element. The data forwarding rule indicates that the tunnel corresponding to the first bearer is used for forwarding the first flow.

In addition, the receiving module <NUM>, the processing module <NUM>, and the sending module <NUM> in the session management function network element may further implement other operations or functions of the session management function network element or the PGW-C+SMF in the foregoing methods. Details are not repeated herein.

As shown in <FIG>, an access and mobility management function network element may include a receiving module <NUM>, a processing module <NUM>, and a sending module <NUM>. The access and mobility management function network element may be configured to perform operations of the access and mobility management function network element or the AMF in <FIG> and <FIG> to <FIG>. For example:.

The sending module <NUM> is configured to send information about a first bearer in a first network to a session management function network element. The receiving module <NUM> is configured to receive flow information of a first flow in a second network and forwarding information from the session management function network element. The flow information indicates a flow for data forwarding, and the forwarding information is used for forwarding the first flow to a tunnel corresponding to the first bearer.

Therefore, after receiving the flow information and the forwarding information from the session management function network element, the access and mobility management function network element sends the flow information and the forwarding information to an access network device in the second network. The access network device in the second network may send, to a user plane function network element based on the flow information and the forwarding information, only a flow required for data forwarding, so the access network device does not need to forward all flows to the user plane function network element, thereby reducing transmission resources.

Optionally, before sending the information about the first bearer in the first network to the session management function network element, the sending module <NUM> is further configured to send a flow list to the session management function network element, where the flow list includes the flow information; the receiving module <NUM> is further configured to learn, from the session management function network element, of a bearer for data forwarding, where the bearer for data forwarding is associated with a flow in the flow list, and the bearer for data forwarding includes the first bearer; and the sending module <NUM> is further configured to indicate, to a core network control plane network element in the first network, the bearer for data forwarding.

Optionally, before the information about the first bearer in the first network is sent to the session management function network element, the receiving module <NUM> is further configured to learn, from the session management function network element, of a bearer for data forwarding, where the bearer for data forwarding includes the first bearer; and the sending module <NUM> is further configured to indicate, to a core network control plane network element in the first network, the bearer for data forwarding.

Further, optionally, the sending module <NUM> is configured to send a request message to the core network control plane network element in the first network. The request message includes information to be sent to an access network device in the first network, and the information to be sent to the access network device in the first network indicates the bearer for data forwarding.

In another possible implementation, the flow information further includes identification information of a second flow in the second network, and the forwarding information includes first forwarding information and second forwarding information. The first forwarding information is used for forwarding the first flow to the tunnel corresponding to the first bearer, and the second forwarding information is used for forwarding the second flow to a tunnel corresponding to a second bearer.

In addition, the receiving module <NUM>, the processing module <NUM>, and the sending module <NUM> in the access and mobility management function network element may further implement other operations or functions of the access and mobility management function network element or the AMF in the foregoing methods. Details are not repeated herein.

As shown in <FIG>, an access network device may include a receiving module <NUM>, a processing module <NUM>, and a sending module <NUM>. The access network device may be configured to perform operations of the access network device or the NG-RAN in <FIG> and <FIG> to <FIG>. For example:
The receiving module <NUM> is configured to receive flow information of a first flow in a second network and forwarding information from an access and mobility management function network element. The flow information indicates a flow for data forwarding, and the forwarding information is used for forwarding the first flow to a tunnel corresponding to a first bearer in a first network. The receiving module <NUM> is further configured to receive the first flow. The sending module <NUM> is configured to send the first flow to a user plane function network element based on the flow information and the forwarding information.

Therefore, after receiving the flow information and the forwarding information from the access and mobility management function network element, the access network device in the second network may send, to the user plane function network element based on the flow information and the forwarding information, only a flow required for data forwarding, so the access network device does not need to forward all flows to the user plane function network element, thereby reducing transmission resources.

Optionally, the processing module <NUM> is configured to determine a flow list.

Optionally, the sending module <NUM> is further configured to send the flow list to the access and mobility management function network element. The flow list is used to determine a bearer for data forwarding, the flow list includes the flow information, the bearer for data forwarding is associated with a flow in the flow list, and the bearer for data forwarding includes the first bearer.

In addition, the receiving module <NUM>, the processing module <NUM>, and the sending module <NUM> in the access network device may further implement other operations or functions of the access network device or the NG-RAN in the foregoing methods. Details are not repeated herein.

An aspect of this application further discloses a data forwarding system, including the session management function network element, the access and mobility management function network element, and the access network device. For interaction in the system, refer to any of the descriptions of <FIG> and <FIG> to <FIG>. Details are not repeated herein.

<FIG> is a schematic structural diagram of a data forwarding apparatus in the foregoing aspects. As shown in <FIG>, the data forwarding apparatus includes a transceiver <NUM> and a processor <NUM>. In an aspect, the processor <NUM> is configured to perform corresponding functions of the session management function network element in the foregoing methods, and the transceiver <NUM> is configured to implement communication between the session management function network element and an access and mobility management function network element/a user plane function network element. In another aspect, the processor <NUM> is configured to perform corresponding functions of the access and mobility management function network element in the foregoing methods, and the transceiver <NUM> is configured to implement communication between the access and mobility management function network element and a session management function network element/an access network device in a second network/a core network control plane network element in a first network. In still another aspect, the processor <NUM> is configured to process and perform corresponding functions of the access network device in the second network in the foregoing methods, and the transceiver <NUM> is configured to implement communication between the access network device and an access and mobility management function network element/a user plane function network element. The data forwarding apparatus may further include a memory <NUM>. The memory <NUM> is configured to be coupled to the processor <NUM>, and the memory <NUM> stores a necessary program instruction and data of the data forwarding apparatus.

The memory <NUM> may store a program instruction used to trigger the processor <NUM> to perform the foregoing functions. The processor <NUM> may perform the foregoing functions by invoking the program instruction in the memory <NUM>. Alternatively, a computer readable storage medium stores a program instruction used to trigger the processor <NUM> to perform the foregoing functions. The processor <NUM> may perform the foregoing functions by invoking the program instruction in the computer readable storage medium.

It can be understood that <FIG> shows only a simplified design of the foregoing apparatuses. In actual application, each of the foregoing devices may include any quantities of transmitters, receivers, processors, controllers, memories, communications units, and the like.

A controller/processor configured to implement the session management function network element in this application may be a central processing unit (CPU), a general purpose processor, a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA) or another programmable logic device, a transistor logic device, a hardware component, or any combination thereof. The controller/processor may implement or execute various example logic blocks, modules, and circuits that are described with reference to the content disclosed in this application. The processor may also be a combination that implements a computing function, for example, a combination of one or more microprocessors or a combination of a DSP and a microprocessor.

The methods or algorithm steps described with reference to the content disclosed in this application may be implemented in a hardware manner, or may be implemented in a manner of executing a software instruction by a processor. The software instruction may include a corresponding software module. The software module may be stored in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable hard disk, a CD-ROM, or a storage medium in any other forms well-known in the art. An example storage medium is coupled to the processor, so that the processor can read information from the storage medium, and can write information into the storage medium. Certainly, the storage medium may also be a part of the processor. The processor and the storage medium may be located in an ASIC. In addition, the ASIC may be located in the session management function network element. Certainly, the processor and the storage medium may also exist in the session management function network element as discrete components.

Claim 1:
A data forwarding method for interworking between a first network and a second network, the first network and the second network are two different networks, the method comprising:
sending (<NUM>), by an access and mobility management function network element in the second network, information about a first bearer in the first network;
receiving (<NUM>), by a session management function network element from the access and mobility management function network element, the information about the first bearer in the first network, wherein the session management function network element integrates a packet data network gateway-control plane in the first network and a session management function in the second network;
determining (<NUM>), by the session management function network element, a first flow in the second network based on the information about the first bearer and association information, wherein the first flow is a flow for data forwarding, wherein the association information indicates an association between the first flow and the first bearer; and
sending (<NUM>, <NUM>), by the session management function network element to an access network device in the second network via the access and mobility management function network element, flow information of the first flow and forwarding information, wherein the flow information indicates the first flow, and the forwarding information identifies a user plane function network element to which to forward the first flow, wherein the user plane function network element integrates a user plane function in the second network and a packet data network gateway-user plane in the first network for forwarding the first flow to a tunnel corresponding to the first bearer.