Session establishment method and device

Abstract

An embodiment of the present application provides a method and apparatus for session establishment, which switches an established PDN connection to a network slice in a 5G network when a terminal switches across systems. The method includes: the terminal receives network slice information corresponding to when an established PDN connection is switched to a 5G network from a control plane functional entity; the network slice information corresponding to when the established PDN connection is switched to a 5G network includes single network slice selection auxiliary information S‑NSSAI of the network slice corresponding to when the established PDN connection is switched to a 5G network; a PDU session establishment request is sent, wherein the PDU session establishment request includes the S‑NSSAI of the network slice corresponding to when the first PDN connection is switched to the 5G network and the data network name DNN corresponding to when the first PDN connection is switched to the 5G network; the first PDN connection is any one of the established PDN connections.

Description

[0001] This application claims priority to Chinese application No. 201711148057.6, filed on November 17, 2017, with application number 201711148057.6 and invention name “Session Establishment Method and Device”, and Chinese application No. 201810037192.1, filed on January 15, 2018, with invention name “Session Establishment Method and Device”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of communication technology, and in particular to a method and device for establishing a session. Background Art

[0003] With the rapid development of wireless communication technology, fifth-generation (5G) mobile communication technology has emerged. In the early stages of network deployment, due to insufficient 5G network coverage, user equipment (UE) may need to switch between 5G and fourth-generation (4G) networks when the UE's location changes.

[0004] A network slice is a logically isolated network used to support specific network capabilities and network characteristics. It can include the entire network end-to-end (E2E), or some network functions can be shared among multiple network slices. It is a key technology to meet the network differentiation requirements of 5G mobile communication technology.

[0005] The network slice can be specifically represented by network slice selection assistance information (NSSAI). When the terminal accesses the 5G core network (5GC), the terminal provides the requested NSSAI. The network selects the corresponding network slice for the terminal based on the NSSAI, and the network determines the NSSAI that the terminal is allowed to access based on the NSSAI requested by the terminal, that is, the Allowed NSSAI.

[0006] However, there is no concept of network slicing in 4G networks. In 4G, each packet data network (PDN) connection corresponds to an access point name (APN). When creating a packet data unit (PDU) session in a network slice, a data network name (DNN) and a single NSSAI (S-NSSAI) are required. In existing protocols, although APN and DNN can be equivalent, when a terminal switches from a 4G network to a 5GC that supports network slicing, how to determine the S-NSSAI of the network slice corresponding to the PDN connection established by the terminal in the 4G network so that a PDU session can be established in the 5GC network slice based on the determined S-NSSAI? There is currently no relevant solution. Summary of the Invention

[0007] The embodiments of the present application provide a session establishment method and apparatus, so that when a terminal switches across systems, an established PDN connection is switched to a network slice in a 5G network.

[0008] To achieve the above objectives, the present invention provides the following technical solutions:

[0009] In a first aspect, a session establishment method is provided, the method comprising: a terminal receives network slice information corresponding to when an established packet data network PDN connection is switched to a 5G network from a control plane functional entity; the network slice information corresponding to when the established PDN connection is switched to the 5G network includes single network slice selection auxiliary information S-NSSAI of the network slice corresponding to when the established PDN connection is switched to the 5G network; a packet data unit PDU session establishment request is sent, wherein the PDU session establishment request includes the S-NSSAI of the network slice corresponding to when the first PDN connection is switched to the 5G network and the data network name DNN corresponding to when the first PDN connection is switched to the 5G network; the first PDN connection is any one of the established PDN connections. In which, the terminal establishes one or more PDN connections in the 4G network through one or more control plane functional entities.

[0010] When the terminal is in a non-roaming or local breakout (LBO) roaming scenario, the S-NSSAI of the corresponding network slice when the first PDN connection is switched to the 5G network is the S-NSSAI of the network slice received by the terminal from the control plane functional entity.

[0011] When the terminal is in a home routed scenario, the S-NSSAI of the network slice corresponding to the first PDN connection when it switches to the 5G network is the S-NSSAI of the network slice of the visited location. Specifically, before sending the PDU session establishment request, the method also includes the terminal mapping the network slice information corresponding to the first PDN connection when it switches to the 5G network received from the control plane functional entity to the S-NSSAI of the network slice of the visited location according to the mapping relationship between the S-NSSAI of the home network slice and the S-NSSAI of the network slice of the visited location.

[0012] The control plane functional entity sends the corresponding network slice information when the established PDN connection is switched to the 5G network to the terminal, so that when the terminal switches to the 5G network, it can establish a PDU session in the 5G network slice according to the corresponding network slice information.

[0013] In one possible implementation, the corresponding network slice information when the established packet data network PDN connection is switched to the 5G network is carried in the protocol configuration item PCO message. The control plane function entity sends the corresponding network slice information when the established PDN connection is switched to the 5G network to the terminal through the PCO message. Specifically, the PCO message can be sent to the terminal through the Mobility Management Entity (MME) and the base station in the 4G network. The network slice information corresponding to the switching of the established packet data network PDN connection to the 5G network is transmitted through the PCO message, so that the MME can only transparently transmit the message without saving the message.

[0014] In one possible implementation, the terminal also receives indication information from the control plane functional entity, and the indication information is used to indicate that the network slice information received from the control plane functional entity is home network slice information. Before sending a PDU session establishment request to the network, the terminal first maps the S-NSSAI of the home network slice corresponding to when the PDN connection requested to be switched is switched to 5G to the S-NSSAI of the visited network slice corresponding to when the PDN connection requested to be switched is switched to 5G, based on the correspondence between the S-NSSAI of the home network slice and the S-NSSAI of the visited network slice, and then carries the S-NSSAI of the visited network slice corresponding to when the PDN connection requested to be switched is switched to 5G in the PDU session establishment request to trigger the network to establish a PDU session.

[0015] In one possible implementation, the network slice information corresponding to when the established PDN connection is switched to the 5G network also includes the identifier NSI-ID of the network slice instance corresponding to when the established PDN connection is switched to the 5G network. When an S-NSSAI deploys more than one network slice instance in the network deployment, the network slice information corresponding to when the PDN connection is switched to the 5G network sent by the control plane functional entity to the terminal also includes the identifier of the corresponding network slice instance, thereby ensuring session continuity after the PDN connection is switched.

[0016] In one possible implementation, before the terminal receives the network slicing information corresponding to when the established packet data network PDN connection is switched to the 5G network from the control plane functional entity, the method further includes: the terminal sends a capability indication to the control plane functional entity, where the capability indication is used to indicate that the terminal can switch to the 5G network. In a specific implementation, not all terminals need to receive the network slicing information corresponding to when the established PDN connection is switched to the 5G network after establishing a PDN connection in the 4G network. For example, a terminal that does not support 5G network communication capabilities cannot use this information to switch to the 5G network even if it receives this information.

[0017] Optionally, sometimes not all PDN connections can be switched to the 5G network. For those PDN connections that cannot be switched to the 5G network, even if the terminal sends a PDU session establishment request, the final session establishment will fail. In order to avoid unnecessary signaling waste. Therefore, before sending the packet data unit PDU session establishment request, the method also includes: the terminal determines a PDN connection that can be switched to the 5G network among the established PDN connections, and the first PDN connection is any one of the PDN connections that can be switched to 5G. Among them, the terminal determines the PDN connection in the established PDN connection that can be switched to the 5G network, specifically including: the terminal sends a registration request, the registration request includes the network slice information corresponding to when the PDN connection requested by the terminal is switched to the 5G network, wherein the PDN connection requested by the terminal to be switched is a part or all of the PDN connections in the established PDN connection; receives a registration response, the registration response includes the S-NSSAI of the network slice allowed to access by the terminal; determines the PDN connection that can be switched to the 5G network according to the S-NSSAI corresponding when the PDN connection requested by the terminal to be switched is switched to the 5G network and the S-NSSAI of the network slice allowed to be accessed.

[0018] It should be noted that when the terminal is in a non-roaming or local breakout (LBO) roaming scenario, the corresponding network slice information when the PDN connection that the terminal requests to switch is switched to the 5G network is the network slice information received by the terminal from the control plane functional entity.

[0019] When the terminal is in a home-routed scenario, the corresponding network slice information when the PDN connection that the terminal requests to switch is switched to the 5G network is the network slice information of the visited location. Specifically, before sending the PDU session establishment request, the method also includes the terminal mapping the network slice information sent by the control plane function entity to the network slice information of the visited location based on the mapping relationship between the S-NSSAI of the home network slice and the S-NSSAI of the visited network slice.

[0020] In the second aspect, a session establishment method is provided, which includes: the control plane functional entity sends the network slice information corresponding to the established packet data network PDN connection when it is switched to the 5G network to the terminal through the MME; the network slice information corresponding to the established PDN connection when it is switched to the 5G network includes the single network slice selection auxiliary information S-NSSAI of the network slice corresponding to the established PDN connection; the receiving terminal sends a packet data unit PDU session establishment request through the AMF, wherein the PDU session establishment request includes the S-NSSAI of the network slice corresponding to the first PDN connection and the data network name DNN corresponding to the first PDN connection when it is switched to the 5G network; the first PDN connection is any one of the established PDN connections. The control plane functional entity sends the network slice information corresponding to the established PDN connection when it is switched to the 5G network to the terminal, so that the terminal can establish a PDU session in the 5G network slice according to the corresponding network slice information when it switches to the 5G network.

[0021] In one possible implementation, the corresponding network slice information when the established packet data network PDN connection is switched to the 5G network is carried in the protocol configuration item PCO message. The control plane function entity sends the corresponding network slice information when the established PDN connection is switched to the 5G network to the terminal through the PCO message. Specifically, the PCO message can be sent to the terminal through the Mobility Management Entity (MME) and the base station in the 4G network. The network slice information corresponding to the switching of the established packet data network PDN connection to the 5G network is transmitted through the PCO message, so that the MME can only transparently transmit the message without saving the message.

[0022] In one possible implementation, the control plane functional entity can specifically determine the corresponding network slice information when the established PDN connection is switched to the 5G network based on the access point name APN corresponding to the established PDN connection.

[0023] In one possible implementation, in the scenario of home routing, the control plane function entity also sends indication information to the terminal, and the indication information is used to indicate that the network slice information sent by the control plane function entity is the home network slice information, so that after the terminal receives the indication information, it will map the home network slice information received from the control plane function entity to the visited network slice information.

[0024] In one possible implementation, when the established PDN is established in a home routing scenario, the control plane functional entity may determine the network slice information of the home location corresponding to when the established PDN connection is switched to 5G; then map the network slice information of the home location corresponding to when the established PDN connection is switched to 5G to the network slice information of the visited location; and send the network slice information of the visited location corresponding to when the established PDN connection is switched to 5G to the terminal as the slice information corresponding to when the established PDN connection is switched to 5G. In this way, all network slice information received by the terminal can be used directly, and the terminal does not need to configure the relevant mapping table locally. When establishing a PDU session, it will no longer be necessary to distinguish whether it is a home routing scenario.

[0025] In one possible implementation, the network slice information corresponding to when the established PDN connection is switched to the 5G network also includes the identifier NSI-ID of the network slice instance corresponding to when the established PDN connection is switched to the 5G network. When an S-NSSAI deploys more than one network slice instance in the network deployment, the network slice information corresponding to when the PDN connection is switched to the 5G network sent by the control plane functional entity to the terminal also includes the identifier of the corresponding network slice instance, thereby ensuring session continuity after the PDN connection is switched.

[0026] In one possible implementation, before the control plane function entity sends the network slice information corresponding to when the established packet data network PDN connection is switched to the 5G network to the terminal, the method includes: the control plane function entity receives a capability indication from the terminal, and the capability indication is used to indicate that the terminal can switch to the 5G network. The control plane function entity may establish PDN connections for different terminals at the same time, but for those PDN connections corresponding to terminals that do not have 5G network communication capabilities or do not need to be switched to the 5G network, the control plane function entity does not need to send the network slice information corresponding to when the PDN connection is switched to the 5G network to these terminals.

[0027] In a third aspect, a terminal is provided that has the functionality to implement the method described in the first aspect. The functionality can be implemented in hardware or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the functionality described above.

[0028] In a fourth aspect, a device is provided, comprising: a processor and a memory; the memory is configured to store computer-executable instructions; when the device is running, the processor executes the computer-executable instructions stored in the memory, causing the device to perform any of the session establishment methods described in the first aspect. The device may specifically be a terminal or a chip in a terminal involved in any of the session establishment methods described in the first aspect.

[0029] In a fifth aspect, a computer-readable storage medium is provided, wherein instructions are stored in the computer-readable storage medium. When the computer-readable storage medium is run on a computer, the computer can execute the session establishment method described in any one of the above-mentioned first aspects.

[0030] In a sixth aspect, a computer program product comprising instructions is provided, which, when executed on a computer, enables the computer to execute the session establishment method described in any one of the first aspects.

[0031] Among them, the technical effects brought about by any design method in the third to sixth aspects can refer to the technical effects brought about by different design methods in the first aspect, and will not be repeated here.

[0032] In a seventh aspect, a control plane functional entity is provided, which has the function of implementing the method described in the second aspect. The function can be implemented by hardware or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the above functions.

[0033] In the eighth aspect, a control plane functional entity is provided, including: a processor and a memory; the memory is used to store computer execution instructions, and when the device is running, the processor executes the computer execution instructions stored in the memory to enable the device to perform a session establishment method as described in any one of the above-mentioned second aspects.

[0034] In a ninth aspect, a computer-readable storage medium is provided, wherein instructions are stored in the computer-readable storage medium. When the computer-readable storage medium is run on a computer, the computer can execute the session establishment method described in any one of the second aspects above.

[0035] In a tenth aspect, a computer program product comprising instructions is provided, which, when executed on a computer, enables the computer to execute the session establishment method described in any one of the second aspects.

[0036] These and other aspects of the present application will become more readily apparent from the description of the following embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a schematic diagram of the intercommunication architecture between 4G and 5G networks;

[0038] Figure 2 A schematic diagram of the hardware structure of the communication device provided in the embodiment of the present application;

[0039] Figure 3 Schematic diagram of the process of establishing a session provided in the embodiment of the present application Figure 1 ;

[0040] Figure 4 Schematic diagram of the process of establishing a session provided in the embodiment of the present application Figure 2 ;

[0041] Figure 5 A schematic diagram of the structure of the device provided in the embodiment of the present application;

[0042] Figure 6 A schematic diagram of the structure of the control plane functional entity provided in an embodiment of the present application. DETAILED DESCRIPTION

[0043] In order to facilitate understanding of the technical solutions of the embodiments of the present application, a brief introduction to the relevant technologies of the present application is first given as follows.

[0044] NSSAI:

[0045] NSSAI includes multiple S-NSSAIs. S-NSSAI consists of a slice / service type (SST) and a slice differentiator (SD). SST and SD can be defined by the standard or customized by the operator; SD is optional information that supplements the SST to distinguish multiple network slices with the same SST. For example, it can be used to characterize the ownership of network slices. The types and functions of NSSAI defined in the 23.501 standard are shown in Table 1.

[0046] Table 1

[0047]

[0048] The network architecture and business scenarios described in the embodiments of the present invention are intended to more clearly illustrate the technical solutions of the embodiments of the present invention, and do not constitute a limitation on the technical solutions provided by the embodiments of the present invention. Ordinary technicians in this field can know that with the evolution of network architecture and the emergence of new business scenarios, the technical solutions provided by the embodiments of the present invention are also applicable to similar technical problems.

[0049] The embodiment of the present invention provides a method for mobility management, which can be applied to Figure 1 In the 4G network and 5G network intercommunication architecture system 100 shown in FIG. Figure 1 As shown in the figure, it includes the user plane function (UPF) entity shared by the 4G network and the 5G network + the PDN gateway user plane function (PGW-U) entity, the session management function (SMF) entity + the PDN gateway control plane function (PGW-C) entity, the policy control function (PCF) entity + the policy and charging rules function (PCRF) entity, the home subscriber server (HSS) + the unified data management (UDM) entity. Here, "+" indicates a combined entity. UPF is the user plane function of the 5G network, PGW-U is the gateway user plane function of the 4G network corresponding to the UPF, SMF is the session management function of the 5G network, PGW-C is the gateway control plane function in the 4G network corresponding to the SMF, PCF is the policy control function of the 5G network, and PCRF is the policy charging rules function of the 4G network corresponding to the PCF. The term "combined" here means that the same device simultaneously possesses the functions of two entities. In the embodiments of this application, for ease of description, the HSS+UDM entity is referred to as the user data management entity, and the PGW-C entity+SMF entity is referred to as the control plane function entity. These terms are described here for simplicity and are not further elaborated below. Of course, the combined network device described above may also be referred to by other names, and this embodiment of the application does not specifically limit this.

[0050] In addition, if Figure 1 As shown, the above-mentioned 4G network and 5G network intercommunication architecture can also include MME and Serving Gateway (SGW), as well as Access and Mobility Management Function (AMF) entities in the 5G network.

[0051] Among them, the terminal accesses the 4G network through the evolved universal terrestrial radio access network (E-UTRAN) device, and the terminal accesses the 5G network through the next generation radio access network (NG-RAN) device. The E-UTRAN device communicates with the MME through the S1-MME interface, the E-UTRAN device communicates with the SGW through the S1-U interface, the MME communicates with the SGW through the S11 interface, the MME communicates with the user data management entity through the S6a interface, the MME communicates with the AMF entity through the N26 interface, the SGW communicates with the PGW-U entity + UPF entity through the S5-U interface, the SGW communicates with the PGW-C entity + SMF entity through the S5-C interface, the PGW-U entity + UPF entity communicates with the NG-RAN device through the N3 interface, and the PGW-U entity + UPF entity communicates with the NG-RAN device through the N3 interface. The N4 interface communicates with the PGW-C entity + SMF entity, the PGW-C entity + SMF entity communicates with the PCRF entity + PCF entity through the N7 interface, the HSS + UDM entity communicates with the PGW-C entity + SMF entity through the N10 interface, the HSS + UDM entity communicates with the AMF entity through the N8 interface, the PCRF entity + PCF entity communicates with the AMF entity through the N15 interface, the PGW-C entity + SMF entity communicates with the AMF entity through the N11 interface, the AMF entity communicates with the NG-RAN device through the N2 interface, and the AMF entity communicates with the terminal through the N1 interface.

[0052] It should be noted that Figure 1 The interface names between the network elements in the embodiment are just an example. In the specific implementation, the interface names may be other names, and the embodiments of the present application do not make specific limitations on this.

[0053] It should be noted that the NG-RAN device in the 5G network can also be referred to as an access device. The access device refers to a device that accesses the core network, such as a base station, a broadband network gateway (BNG), an aggregation switch, a non-3GPP access device, etc. The base station can include various forms of base stations, such as macro base stations, micro base stations (also known as small stations), relay stations, access points, etc., which are not specifically limited in the embodiments of the present application.

[0054] Of course, there may be other network elements in the 4G network and the 5G network. For example, the 4G network may also include a general packet radio system (GPRS) service support node (SGSN), and the 5G network may also include an authentication server function (AUSF) entity and a network slice selection function (NSSF) entity, etc. The embodiments of the present application do not specifically limit this.

[0055] Since the PDN connection in the 4G network is served by the jointly established PGW-C / SMF and PGW-U / UPF (i.e., the control plane functional entity), when the terminal switches from 4G to the 5G network, the PDU session is still served by the PGW-C / SMF and PGW-U / UPF, that is, the anchor point of the session service remains unchanged before and after the switch, so that the IP address of the session remains unchanged. In an embodiment of the present application, when the UE accesses the 4G network and establishes a PDN connection, the control plane functional entity sends the corresponding network slice information when the terminal's established PDN connection is switched to the 5G network to the terminal. Subsequently, when the terminal moves to the 5G coverage area, the terminal carries the corresponding network slice information when the established PDN connection is switched to the 5G network in the registration request sent to the 5G network. The 5G network determines the AMF and Allowed NSSAI serving the UE based on the information of the network slice corresponding to the established PDN connection, and sends the Allowed NSSAI to the terminal. Based on the Allowed NSSAI and the corresponding network slice information when switching from its existing PDN connection in the 4G network to the 5G network, the terminal can determine which established PDN connections can be switched to the 5G network. For PDN connections that can be switched to the 5G network, the terminal initiates PDU session establishment to complete the cross-network session handover.

[0056] The terminals involved in the embodiments of the present application may include various handheld devices, vehicle-mounted devices, wearable devices, computing devices, or other processing devices connected to a wireless modem with wireless communication functions; they may also include subscriber units, cellular phones, smartphones, wireless data cards, personal digital assistants (PDAs), tablet computers, wireless modems, handheld devices, laptop computers, cordless phones, or wireless local loop (WLL) stations, machine type communication (MTC) terminals, user equipment (UE), mobile stations (MS), terminal devices, etc. For the convenience of description, in this application, the above-mentioned devices are collectively referred to as terminals.

[0057] The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. In the description of the present application, unless otherwise specified, "multiple" refers to two or more than two. In addition, in order to facilitate the clear description of the technical solutions in the embodiments of the present application, in the embodiments of the present application, words such as "first" and "second" are used to distinguish between identical or similar items with substantially the same functions and effects. Those skilled in the art will understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit them to be different.

[0058] like Figure 2 As shown, Figure 1 The nodes shown, such as terminals, MME, AMF, SMF entity + PGW-C entity, E-UTRAN or NG-RAN, can be Figure 2 This is achieved by using the communication device (or system) in the communication device.

[0059] Figure 2 FIG2 is a schematic diagram of the hardware structure of a communication device provided in an embodiment of the present application. The communication device 200 includes at least one processor 201 , a communication line 202 , a memory 203 and at least one communication interface 204 .

[0060] The processor 201 may be a general-purpose central processing unit (CPU), a microprocessor, an application-specific integrated circuit (ASIC), or one or more integrated circuits for controlling the execution of the program of the present application.

[0061] The communication link 202 may include a pathway for transmitting information between the aforementioned components.

[0062] The communication interface 204 uses any transceiver or other device for communicating with other devices or communication networks, such as Ethernet, radio access network (RAN), wireless local area network (WLAN), etc.

[0063] The memory 203 may be a read-only memory (ROM) or other type of static storage device that can store static information and instructions, a random access memory (RAM) or other type of dynamic storage device that can store information and instructions, or an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, an optical disc storage (including a compact disc, laser disc, optical disc, digital versatile disc, Blu-ray disc, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and can be accessed by a computer, but is not limited thereto. The memory may exist independently and be connected to the processor via a communication line 302. The memory may also be integrated with the processor.

[0064] The memory 203 is used to store computer-executable instructions for executing the solution of the present application, and the execution is controlled by the processor 201. The processor 201 is used to execute the computer-executable instructions stored in the memory 203, thereby implementing the session establishment method provided in the following embodiments of the present application.

[0065] Optionally, the computer-executable instructions in the embodiments of the present application may also be referred to as application code, which is not specifically limited in the embodiments of the present application.

[0066] In a specific implementation, as an embodiment, the processor 201 may include one or more CPUs, such as Figure 2 CPU0 and CPU1 in.

[0067] In a specific implementation, as an embodiment, the communication device 200 may include multiple processors, such as Figure 2 201 and processor 208 in FIG. Each of these processors may be a single-CPU processor or a multi-CPU processor. A processor herein may refer to one or more devices, circuits, and / or processing cores for processing data (e.g., computer program instructions).

[0068] In a specific implementation, as an embodiment, the communication device 200 may further include an output device 205 and an input device 206. The output device 205 communicates with the processor 201 and can display information in a variety of ways. For example, the output device 205 can be a liquid crystal display (LCD), a light emitting diode (LED) display device, a cathode ray tube (CRT) display device, or a projector. The input device 306 communicates with the processor 301 and can receive user input in a variety of ways. For example, the input device 206 can be a mouse, a keyboard, a touch screen device, or a sensor device.

[0069] The communication device 200 can be a general purpose device or a dedicated device. In a specific implementation, the communication device 200 can be a desktop computer, a portable computer, a network server, a personal digital assistant (PDA), a mobile phone, a tablet computer, a wireless terminal device, an embedded device or a computer with a Figure 2 The embodiment of the present application does not limit the type of the communication device 200.

[0070] The following will be combined Figure 1 and Figure 2 , the session establishment method provided in the embodiment of the present application is specifically explained.

[0071] like Figure 3 As shown, a session establishment method is provided in an embodiment of the present application. In this embodiment, the terminal first accesses the 4G network through the E-UTRAN device and establishes a PDN connection in the 4G network. Subsequently, as the terminal moves to the 5G service range, the terminal accesses the 5G network through the NG-RAN device. This embodiment of the present application is applicable to non-roaming or LBO roaming scenarios. The method includes the following steps:

[0072] Step 301: The terminal establishes a PDN connection in the 4G network.

[0073] The establishment of the PDN connection may be established during the attach process, or initiated by the terminal after attaching. The process of establishing the PDN connection refers to the existing protocol and is not described here in detail.

[0074] Optionally, when the terminal establishes a PDN connection, the terminal determines that it may switch to a 5G network in the future, for example, it determines that it has the ability to support a 5G network, then the terminal sends a capability indication to the control plane function entity, and the capability indication is used to indicate that the terminal can subsequently switch to a 5G network, and the capability indication can be capability information of the terminal supporting 5G (for example, an indication that the terminal supports 5G NAS). The terminal sends the capability indication to the control plane function entity, specifically including: when the terminal is attached to the 4G network, the terminal sends the capability indication to the MME, so that the MME sends the capability indication to the control plane function entity through the SGW during the PDN connection establishment process; or, the terminal sends a protocol configuration option (PCO) message to the control plane function entity, and the PCO message carries the capability indication.

[0075] It should be noted that the terminal may establish one or more PDN connections in the 4G network, and the one or more PDN connections may be served by one or more control plane function entities, which is not limited in this embodiment of the present application. For ease of description, the embodiment of the present application only takes the example of the terminal establishing one or more PDN connections through a control plane function instance.

[0076] Step 302: The control plane functional entity obtains the network slice information corresponding to when the established PDN connection is switched to 5G, and sends the network slice information to the terminal so that the terminal receives the network slice information corresponding to when the established PDN connection is switched to 5G.

[0077] Among them, the established PDN connection includes one or more PDN connections. In actual deployment, PDU sessions in 5G are associated with network slice instances, and a network slice instance can be indicated by a network slice instance ID (NSI-ID). A network slice identified by S-NSSAI may have multiple network slice instances (for example, different network slice instances can achieve load sharing). In addition, a network slice instance can support one or more data networks, where the data network can be identified by a data network name (Data Network Name, DNN).

[0078] Therefore, according to the network deployment situation, in order to switch the PDN connection established by the terminal in the 4G network to the PDU session in the network slice instance in the 5G network, the network slice information corresponding to the PDN connection switched to 5G sent by the control plane functional entity to the terminal may include different contents. Since the control plane functional entity is located in the network slice instance, when the control plane functional entity supports multiple network slices, the control plane functional entity can obtain the S-NSSAI corresponding to the different network slice instances it supports, the identifier NSI-ID of the network slice instance, and one or more data network names supported by the network slice instance. The network slice information corresponding to when the established PDN connection is switched to 5G includes the S-NSSAI of the network slice corresponding to when the established PDN connection is switched to 5G, and optionally, also includes the identifier NSI-ID of the network slice instance corresponding to when the established PDN connection is switched to the 5G network. When the DNN used when the terminal switches to the 5G network is different from the APN in 4G, the control plane functional entity optionally also needs to obtain the DNN used when the terminal switches to the 5G network and send it to the terminal. Specifically,

[0079] In one possible implementation, based on the network deployment situation, a correspondence between the PDN connection and the S-NSSAI is pre-configured in the control plane functional entity, and the control plane functional entity obtains the network slice information corresponding to the established PDN connection when it is switched to 5G, including: the control plane functional entity obtains the S-NSSAI of the network slice corresponding to the established PDN connection based on the information of the established PDN connection and the pre-configured correspondence between the PDN connection and the S-NSSAI. Under this network deployment, the DNN used when the PDN connection is switched to 5G is the same as the APN in 4G, and only one network slice instance is deployed for each S-NSSAI.

[0080] For example, it is assumed that the correspondence between the pre-configured PDN connection and the S-NSSAI is as shown in Table 2:

[0081] Table 2

[0082]

[0083]

[0084] In another possible implementation, according to the network deployment situation, the correspondence between the PDN connection, S-NSSAI, and DNN is pre-configured in the control plane functional entity, and the control plane functional entity obtains the network slice information corresponding to when the established PDN connection is switched to 5G, including: the control plane functional entity obtains the S-NSSAI of the network slice corresponding to when the established PDN connection is switched to the 5G network and the DNN used when the established PDN connection is switched to 5G based on the information of the established PDN connection and the pre-configured correspondence between the PDN connection, S-NSSAI, and DNN. Under this network deployment, the DNN used when the PDN connection is switched to 5G may be different from the APN in 4G, and only one network slice instance is deployed for each S-NSSAI.

[0085] For example, it is assumed that the correspondence between the pre-configured PDN connection, S-NSSAI, and DNN is as shown in Table 3:

[0086] Table 3

[0087] PDN connection information S-NSSAI DNN PDN Connection 1 S-NSSAI1 DNN1 PDN Connection 2 S-NSSAI2 DNN2 …… …… ……

[0088] In another possible implementation, according to the network deployment situation, the correspondence between the PDN connection and the S-NSSAI, DNN and NSI-ID is pre-configured in the control plane functional entity, and the control plane functional entity obtains the network slice information corresponding to when the established PDN connection is switched to 5G, including: the control plane functional entity obtains the S-NSSAI of the network slice corresponding to when the established PDN connection is switched to 5G, the DNN used when the established PDN connection is switched to 5G, and the NSI-ID of the network slice instance corresponding to when the established PDN connection is switched to 5G based on the information of the established PDN connection and the pre-configured correspondence between the PDN connection and the S-NSSAI, DNN and NSI-ID. Under this network deployment, the DNN used when the PDN connection is switched to 5G may be different from the APN in 4G, and each S-NSSAI may deploy more than one network slice instance.

[0089] For example, it is assumed that the correspondence between the pre-configured PDN connection and the S-NSSAI, DNN, and NSI-ID is as shown in Table 4:

[0090] Table 4

[0091]

[0092]

[0093] Among them, the PDN connection can be represented by the APN corresponding to the PDN connection, that is, the information of the established PDN connection can specifically include the APN corresponding to the established PDN connection. Optionally, it can also be represented by the APN corresponding to the PDN connection and related subscription information. The embodiment of the present application does not limit the specific form of the information of the PDN connection.

[0094] In a specific implementation, the control plane functional entity may send the corresponding network slice information when the established PDN connection is switched to 5G to the terminal through a PCO message in the PDN connection establishment response or the terminal's attachment response. Optionally, the PCO message sent by the control plane functional entity to the terminal also includes the DNN used when the established PDN connection is switched to 5G.

[0095] Step 303: When the terminal moves to the 5G network coverage, the terminal initiates a registration request, which includes the network slice information corresponding to when the PDN connection that the terminal requests to switch is switched to 5G. The registration request is sent to the AMF through an access device (such as a base station) so that the AMF receives the registration request. The PDN connection that the terminal requests to switch is part or all of the established PDN connections.

[0096] Specifically, after the terminal receives the corresponding network slice information when the established PDN connection is switched to 5G from the control plane functional entity in step 302, the terminal determines the PDN connection requested to be switched and the corresponding network slice information when the PDN connection requested to be switched is switched to 5G according to its own policy requirements. For example, the user triggers the establishment of PDN connection 1 and PDN connection 2 respectively through APP1 and APP2 installed on the terminal, and the control plane functional entity returns the corresponding network slice information when the PDN connection 1 is switched to 5G and the corresponding network slice information when the PDN connection 2 is switched to 5G to the terminal; at this time, the terminal detects that APP1 and APP2 have set switching policies (which can be set by the user or provided by the application), such as APP1 prohibits switching to the 5G network, APP2 switches to 5G first when there is 5G coverage, etc., then the terminal determines that PDN connection 2 is the PDN connection requested to be switched, and the corresponding network slice information when PDN connection 2 is switched to 5G is the network slice information corresponding to the PDN connection requested to be switched when it is switched to 5G.

[0097] Specifically, when the terminal initiates a registration request to the 5G network, if it carries S-NSSAI, the access device will select AMF based on the S-NSSAI carried in the registration request. In an embodiment of the present application, the terminal carries the S-NSSAI of the network slice corresponding to when the PDN connection requested to be switched is switched to 5G in the registration request. Optionally, it may also carry other S-NSSAI requested by the terminal. The access device selects AMF based on the S-NSSAI of the network slice corresponding to when the PDN connection requested to be switched is switched to 5G and other S-NSSAI requested by the terminal, and forwards the registration request to the selected AMF so that the AMF receives the registration request sent by the terminal.

[0098] Specifically, the terminal may put the S-NSSAI of the network slice corresponding to when the PDN connection requested to be switched is switched to 5G and other S-NSSAIs requested by the terminal in the "requested NSSAI" and send them to the AMF, and the terminal notifies the AMF which S-NSSAI in the "requested NSSAI" corresponds to the established PDN connection; or, the terminal puts the S-NSSAI of other requests in the "requested NSSAI" and puts the S-NSSAI of the network slice corresponding to when the PDN connection requested to be switched is switched to 5G in another separate NSSAI and sends it to the AMF. The embodiment of the present application does not limit the method of how the terminal sends the S-NSSAI of the network slice corresponding to when the PDN connection requested to be switched is switched to 5G to the AMF through a registration request.

[0099] Optionally, the registration request also includes an identifier of the terminal. After receiving the registration request from the terminal, the AMF may perform authentication and other processes on the terminal, and ultimately obtain the permanent identifier (SUPI) of the terminal. For details, refer to the relevant standard protocol, which will not be described in detail in this embodiment of the application.

[0100] Step 304: AMF obtains the subscription data of the terminal, where the subscription data of the terminal includes the network slice subscription data of the terminal and the correspondence between the APN corresponding to the PDN connection requested to be switched and the identifier of the control plane functional entity.

[0101] Specifically, the AMF obtains the contract data of the terminal according to the terminal identifier (or SUPI) in the registration request: the contract data of the terminal is obtained from the AMF locally first. If the contract data of the terminal is not available locally, the contract data of the terminal is obtained from the user data management entity. Optionally, the AMF also saves the contract data of the terminal in the context corresponding to the terminal.

[0102] Among them, the number of network slices signed by the terminal includes the S-NSSAI corresponding to the signed network slice, and optionally, also includes information such as the DNN corresponding to the signed network slice.

[0103] Step 305: AMF obtains the S-NSSAI (i.e., Allowed NSSAI) corresponding to the network slice that the terminal is allowed to access.

[0104] Specifically, AMF can obtain the Allowed NSSAI based on the corresponding network slice information and terminal subscription data when the PDN connection requested to be switched is switched to 5G.

[0105] In one possible implementation, the AMF determines the Allowed NSSAI based on the network slice information corresponding to the 5G PDN connection being switched to, as well as the terminal's subscription data. Optionally, the AMF may further determine the Allowed NSSAI based on other S-NSSAIs requested by the terminal.

[0106] For example, when the PDN connection requested to be switched is switched to 5G, the corresponding network slice information includes the S-NSSAI of the network slice corresponding to the PDN connection requested to be switched to 5G, the AMF takes the union of the S-NSSAI of the network slice corresponding to the PDN connection requested to be switched and other S-NSSAIs requested by the terminal, and then takes the intersection with the S-NSSAI corresponding to the network slice subscribed by the terminal and the S-NSSAI corresponding to the network slice supported by the AMF to determine the Allowed NSSAI. When the PDN connection requested to be switched is switched to 5G, the corresponding network slice information includes the S-NSSAI of the network slice corresponding to the PDN connection requested to be switched and the identifier NSI-ID of the network slice instance corresponding to the PDN connection requested to be switched to 5G, in addition to making the above judgment, the AMF also eliminates the PDN connection corresponding to the network slice instance that it cannot serve according to the identifier NSI-ID of the network slice instance corresponding to the PDN connection requested to be switched to 5G.

[0107] For example, the S-NSSAI of the network slice corresponding to the PDN connection requested for switching is S-NSSAI1 and S-NSSAI2, the other S-NSSAI requested by the terminal are S-NSSAI3 and S-NSSAI4, the S-NSSAI corresponding to the network slice subscribed by the terminal is S-NSSAI1, S-NSSAI3 and S-NSSAI5, and the S-NSSAI corresponding to the network slice supported by AMF include S-NSSAI1, S-NSSAI12, S-NSSAI13, S-NSSAI14, S-NSSAI15, S-NSSAI16, S-NSSAI17, S-NSSAI18, S-NSSAI19, S-NSSAI20, S-NSSAI21, S-NSSAI22, S-NSSAI23, S-NSSAI24, S-NSSAI25, S-NSSAI26, S-NSSAI27, S-NSSAI28, S-NSSAI29, S-NSSAI30, S-NSSAI31, S-NSSAI32, S-NSSAI33, S-NSSAI34, S-NSSAI35, S-NSSAI36, S-NSSAI37, S-NSSAI38, S-NSSAI39, S-NSSAI41 SSAI14, S-NSSAI15, the AMF will take the union of the S-NSSAI of the network slice corresponding to the PDN connection requested to be switched and other S-NSSAI requested by the terminal to obtain S-NSSAI1, S-NSSAI2, S-NSSAI3 and S-NSSAI4, and then take the intersection of the S-NSSAI corresponding to the network slice subscribed by the terminal and the S-NSSAI corresponding to the network slice supported by the AMF to obtain S-NSSAI1 and S-NSSAI3, thereby determining that the Allowed NSSAI includes S-NSSAI1 and S-NSSAI3.

[0108] In another possible implementation, the AMF requests the network slice selection function (NSSF) entity to determine the Allowed NSSAI for the terminal. Specifically, the AMF sends a slice selection request to the NSSF, and the slice selection request includes the corresponding network slice information and the subscription data of the terminal when the PDN connection requested to be switched is switched to 5G, and optionally, other S-NSSAI requested by the terminal. The NSSF determines the Allowed NSSAI and the target AMF set corresponding to the Allowed NSSAI based on the corresponding network slice information and the subscription data of the terminal when the PDN connection requested to be switched is switched to 5G, and optionally, based on other S-NSSAI requested by the terminal. Specifically, when the network slice information corresponding to the request to switch the PDN connection is switched to 5G includes the S-NSSAI of the network slice corresponding to the request to switch the PDN connection to 5G, the NSSF takes the union of the S-NSSAI of the network slice corresponding to the request to switch the PDN connection to 5G and other S-NSSAIs requested by the terminal, and then takes the intersection with the S-NSSAI corresponding to the network slice contracted by the terminal to determine the first NSSAI, and then collects the terminal's location, the deployment status of the AMF in the network and other information to determine the target AMF set corresponding to the Allowed NSSAI and the Allowed NSSAI, wherein the Allowed NSSAI is part or all of the NSSAI in the first NSSAI, and any AMF in the target AMF set can simultaneously serve any network slice corresponding to the Allowed NSSAI. Optionally, the NSSF can select a target AMF from the target AMF set.

[0109] The NSSF sends the Allowed NSSAI and the target AMF set (or the target AMF selected from the target AMF set) to the AMF. In the embodiment of the present application, the AMF and the NSSF may also use other methods to confirm the Allowed NSSAI. The embodiment of the present application does not limit the method used by the AMF and the NSSF to confirm the Allowed NSSA.

[0110] The AMF determines whether to redirect the terminal to another AMF for processing based on the target AMF set or target AMF returned by the NSSF. If necessary, the AMF redirects the terminal to another AMF. The redirection method is well known to the public and is not described in detail in this embodiment of the application. This embodiment of the application assumes that the AMF is included in the target AMF set, that is, the AMF does not need to redirect the terminal to another AMF for processing.

[0111] Step 306: AMF sends a registration response to the terminal so that the terminal receives the registration response; wherein the registration response includes the S-NSSAI corresponding to the network slice that the terminal is allowed to access, i.e., Allowed NSSAI.

[0112] Step 307: The terminal determines that it can switch to a PDN connection in the 5G network.

[0113] Specifically, the terminal determines that the PDN connection that can be switched to the 5G network is based on the S-NSSAI corresponding to the network slice allowed to be accessed and the corresponding network slice information when the PDN connection requested to be switched is switched to 5G. For example, the S-NSSAI corresponding to the network slice allowed to be accessed by the terminal is S-NSSAI1 and S-NSSAI3, and the S-NSSAI of the network slice corresponding to the PDN connection requested to be switched is S-NSSAI1 and S-NSSAI2. The terminal determines that the PDN connection corresponding to the network slice S-NSSAI is S-NSSAI1 and the PDN connection can be switched to the 5G network.

[0114] For each PDN connection that can be switched to the 5G network, perform the following steps to switch the PDN connection to a PDU session in the 5G network.

[0115] Step 308: The terminal sends a PDU session establishment request to the AMF, so that the AMF receives the PDU session establishment request sent by the terminal, wherein the PDU session establishment request includes the S-NSSAI of the network slice corresponding to the first PDN connection and the DNN used when the first PDN connection is switched to 5G. The first PDN connection is any one of the switchable PDN connections.

[0116] Specifically, when the control plane function entity does not send the DNN used when switching the established PDN connection to 5G to the terminal in step 302, the terminal defaults to the DNN used when switching the established PDN connection to 5G being the same as the APN in 4G. Therefore, the DNN used when the first PDN connection is switched to 5G is equal to the APN corresponding to the first PDN connection.

[0117] When the control plane function entity sends the DNN used when switching the established PDN connection to 5G to the terminal in step 302, the terminal defaults to the DNN used when switching the established PDN connection to 5G being different from the APN in 4G. Therefore, the PDU session establishment request also includes the APN corresponding to the first PDN connection.

[0118] It should be noted that after the PDN connection is established, the terminal will maintain the APN corresponding to the established PDN connection.

[0119] Step 309: The AMF determines a control plane function entity and forwards the PDU session establishment request to the determined control plane function entity so that the control plane function entity receives the PDU session establishment request.

[0120] The AMF determines the control plane function entity according to the APN corresponding to the first PDN connection and the correspondence between the APN and the identifier of the control plane function entity.

[0121] Specifically, when the PDU session establishment request received by the AMF includes the S-NSSAI of the network slice corresponding to the first PDN connection and the DNN used when the first PDN connection is switched to 5G, the AMF determines that the APN corresponding to the first PDN connection is equal to the DNN used when the first PDN connection is switched to 5G, and determines the control plane functional entity based on the APN corresponding to the first PDN connection and the correspondence between the APN and the identifier of the control plane functional entity. When the PDU session establishment request received by the AMF includes the S-NSSAI of the network slice corresponding to the first PDN connection, the DNN used when the first PDN connection is switched to 5G, and the APN corresponding to the first PDN connection, the AMF determines the control plane functional entity based on the APN corresponding to the first PDN connection and the correspondence between the APN and the identifier of the control plane functional entity.

[0122] Step 310: Establish a PDU session in the network slice instance corresponding to the PDN connection.

[0123] The subsequent process of establishing a PDU session is the same as that of the existing protocol and will not be repeated here.

[0124] In an embodiment of the present application, when the UE has established a PDN connection in the 4G network, the control plane functional entity determines the network slice information corresponding to when the established PDN connection is switched to 5G and sends it to the UE through the PCO. When the UE subsequently registers with the 5GC, it carries the above-mentioned network slice information, which helps the 5GC select the 5G network slice corresponding to the established PDN connection, thereby ensuring that the IP address of the session remains unchanged.

[0125] like Figure 4As shown, another session establishment method provided by an embodiment of the present application. In this embodiment, the terminal first accesses the 4G network through the E-UTRAN device and establishes a PDN connection in the 4G network. Subsequently, because the terminal location moves to the 5G service range, the terminal accesses the 5G network through the NG-RAN device. The embodiment of the present application is applicable to the scenario of routing from the HPLMN (Home public land mobile operator network) during roaming (home routing). In the embodiment of the present application, the home control plane function entity is located in the HPLMN. The method comprises the following steps:

[0126] Step 401: The terminal establishes a PDN connection in the 4G network.

[0127] Step 402: The home control plane functional entity obtains the network slice information corresponding to when the established PDN connection is switched to 5G, and sends the network slice information to the terminal so that the terminal receives the network slice information corresponding to when the established PDN connection is switched to 5G.

[0128] Step 401 is the same as step 301, and step 402 is the same as step 302. For relevant descriptions, refer to the relevant steps of the above embodiment and will not be repeated here. It should be noted that, in one implementation, the network slice information corresponding to the PDN connection switched to 5G sent by the home control plane function entity to the terminal is the network slice information corresponding to the home location (such as S-NSSAI). If the network slice information sent to the UE by the home control plane function entity is the network slice information corresponding to the home location, the home control plane function entity will send indication information indicating that the PDN connection is home location routing to the UE. The indication information is used to indicate that the network slice information received from the control plane function entity is home location network slice information, so that the UE can map the S-NSSAI corresponding to the home location to the S-NSSAI corresponding to the visited location according to the mapping relationship between the home PLMN ID, the home S-NSSAI and the home to visited location S-NSSAI configured by the UE. The home routing indication information can be the home PLMN ID or an identifier of whether it is home location routing.

[0129] In another implementation, the network slice information corresponding to when the PDN connection is switched to 5G sent by the home control plane functional entity to the terminal is the S-NSSAI corresponding to the visited location. At this time, the home control plane functional entity maps the network slice information of the home location corresponding to when the PDN connection is switched to 5G to the network slice information of the visited location. Specifically, the home control plane functional entity first determines the network slice information of the home location corresponding to when the PDN connection is switched to 5G according to the method of step 302, and then maps the network slice information of the home location corresponding to when the PDN connection is switched to 5G to the network slice information of the visited location. The home control plane functional entity obtains the PLMN ID of the visited location currently accessed by the terminal from the MME, and then maps the network slice information of the home location to the network slice information of the visited location according to the mapping relationship between the visited location S-NSSAI and the home location S-NSSAI configured by the home control plane functional entity, as shown in the following table:

[0130] Home PLMN ID Place of Origin: S-NSSAI Visited PLMN ID Visiting place S-NSSAI PLMN ID 1 S-NSSAI1 PLMN ID 2 S-NSSAI12 PLMN ID 1 S-NSSAI2 PLMN ID 2 S-NSSAI22 PLMN ID 1 S-NSSAI1 PLMN ID3 S-NSSAI13

[0131] Optionally, the control plane function entity may also request the NSSF to map the S-NSSAI corresponding to the home location to the S-NSSAI corresponding to the visited location. Specifically, the control plane function entity sends the home location PLMN ID, the home location S-NSSAI, and the visited location PLMN ID to the NSSF, and the NSSF returns the S-NSSAI corresponding to the visited location to the control plane function entity.

[0132] Step 403. When the terminal moves to the coverage of the 5G network, the terminal initiates a registration request, and the registration request includes the network slice information corresponding to when the PDN connection that the terminal requests to switch is switched to 5G. The registration request is sent to the AMF through the access device (such as a base station) so that the AMF receives the registration request. If the terminal receives the home routing indication information in step 402, the terminal maps the received network slice information corresponding to the home location to the network slice information corresponding to the visited location. The terminal maps the network slice information corresponding to the home location to the network slice information corresponding to the visited location based on the mapping relationship between the network slice information corresponding to the home location, the home location PLMN ID, and the network slice information corresponding to the home location and the visited location configured by the UE. The PDN connection that the terminal requests to switch is part or all of the established PDN connections.

[0133] Step 404: AMF obtains the subscription data of the terminal, where the subscription data of the terminal includes the network slice subscription data of the terminal and the correspondence between the APN corresponding to the PDN connection requested to be switched and the identifier of the control plane functional entity.

[0134] Step 404 is the same as step 304. For related descriptions, please refer to the related steps in the above embodiment and will not be repeated here.

[0135] Step 405: AMF obtains the S-NSSAI (i.e., Allowed NSSAI) corresponding to the network slice that the terminal is allowed to access.

[0136] In one possible implementation, except that the AMF in step 403 is the AMF of the visited location, and the AMF in step 303 is the AMF of the home location, the rest of the specific implementation methods are the same. At this time, in step 405, the AMF maps the S-NSSAI of the network slice corresponding to the established PDN connection when switching to 5G to the S-NSSAI of the network slice of the visited location according to the correspondence between the S-NSSAI of the network slice of the home location and the S-NSSAI of the network slice of the visited location, and also maps the S-NSSAI of the network slice subscribed by the user to the S-NSSAI of the network slice of the visited location, and then determines the S-NSSAI corresponding to the visited location network slice that the terminal is allowed to access. The specific determination method is the same as step 305 and will not be repeated here.

[0137] In another possible implementation, in step 403, the corresponding network slice information when the PDN connection requested to be switched by the terminal is switched to 5G is that the terminal maps the S-NSSAI of the network slice corresponding to when the PDN connection requested to be switched is switched to 5G to the S-NSSAI of the visited network slice corresponding to when the PDN connection requested to be switched is switched to 5G according to the correspondence between the S-NSSAI of the home network slice and the S-NSSAI of the visited network slice. That is, with respect to step 302, after the terminal determines the PDN connection requested to be switched, it is also necessary to map the S-NSSAI of the network slice corresponding to when the PDN connection requested to be switched is switched to 5G to the S-NSSAI of the visited network slice corresponding to when the PDN connection requested to be switched is switched to 5G according to the correspondence between the S-NSSAI of the home network slice and the S-NSSAI of the visited network slice. In step 405, the AMF maps the S-NSSAI of the network slice subscribed by the user to the S-NSSAI of the network slice of the visited location based on the correspondence between the S-NSSAI of the home network slice and the S-NSSAI of the network slice of the visited location. Then, the AMF determines the S-NSSAI corresponding to the visited location network slice that the terminal is allowed to access based on the S-NSSAI of the network slice subscribed by the user and the S-NSSAI of the visited location network slice corresponding to the PDN connection requested by the terminal to be switched to 5G. The specific determination method is the same as step 305 and will not be repeated here.

[0138] Step 406: AMF sends a registration response to the terminal so that the terminal receives the registration response; wherein the registration response includes the S-NSSAI corresponding to the visited network slice that the terminal is allowed to access, i.e., Allowed NSSAI.

[0139] Step 407: The terminal determines that it can switch to a PDN connection in the 5G network.

[0140] Referring to step 307, the difference from step 307 is that if the network slice information corresponding to the PDN connection received by the terminal when it is switched to 5G is the S-NSSAI of the home location, the terminal maps the S-NSSAI of the network slice corresponding to the PDN connection requested to be switched to the S-NSSAI of the visited location network slice corresponding to the PDN connection requested to be switched when it is switched to 5G, based on the correspondence between the S-NSSAI of the home location network slice and the S-NSSAI of the visited location network slice, and then combines the S-NSSAI corresponding to the visited location network slice that the terminal is allowed to access received in step 406 to determine the PDN connection that can be switched to the 5G network.

[0141] For each PDN connection that can be switched to the 5G network, perform the following steps to switch the PDN connection to a PDU session in the 5G network.

[0142] Step 408: The terminal sends a PDU session establishment request to the AMF, so that the AMF receives the PDU session establishment request sent by the terminal, wherein the PDU session establishment request includes the S-NSSAI of the visited network slice corresponding to when the first PDN connection is switched to the 5G network and the DNN used when the first PDN connection is switched to 5G. The first PDN connection is any one of the switchable PDN connections.

[0143] Specifically, when the home control plane function entity does not send the DNN used when switching the established PDN connection to 5G to the terminal in step 402, the terminal defaults to the DNN used when switching the established PDN connection to 5G being the same as the APN in 4G. Therefore, the DNN used when the first PDN connection is switched to 5G is equal to the APN corresponding to the first PDN connection.

[0144] When the home control plane function entity sends the DNN used when switching the established PDN connection to 5G to the terminal in step 402, the terminal defaults to the DNN used when switching the established PDN connection to 5G being different from the APN in 4G. Therefore, the PDU session establishment request also includes the APN corresponding to the first PDN connection.

[0145] It should be noted that after the PDN connection is established, the terminal will maintain the APN corresponding to the established PDN connection.

[0146] Optionally, if the UE receives the identifier of the home network slice instance in step 402, the UE sends the identifier information of the home network slice instance to the AMF.

[0147] Step 409: The AMF determines the visited control plane function entity and the home control plane function entity, and forwards the PDU session establishment request to the determined visited control plane function entity so that the visited control plane function entity receives the PDU session establishment request.

[0148] Specifically, the AMF determines the home control plane functional entity, including: the AMF obtains the PDN connection context information of the terminal from the user data management entity, the PDN connection context information including the correspondence between the APN corresponding to the PDN connection and the identifier of the home control plane functional entity. When the PDU session establishment request received by the AMF includes the S-NSSAI of the visited network slice corresponding to the first PDN connection and the DNN used when the first PDN connection is switched to 5G, the AMF determines that the APN corresponding to the first PDN connection is equal to the DNN used when the first PDN connection is switched to 5G, and determines the home control plane functional entity based on the APN corresponding to the first PDN connection and the correspondence between the APN and the identifier of the home control plane functional entity. When the PDU session establishment request received by the AMF includes the S-NSSAI of the visited network slice corresponding to the first PDN connection, the DNN used when the first PDN connection is switched to 5G, and the APN corresponding to the first PDN connection, the AMF determines the home control plane functional entity based on the APN corresponding to the first PDN connection and the correspondence between the APN and the identifier of the home control plane functional entity.

[0149] AMF determines the visited control plane functional entity, specifically including: AMF determines the visited control plane functional entity according to the S-NSSAI of the visited network slice corresponding to the first PDN connection and the DNN used when the first PDN connection is switched to 5G. Specifically, AMF can determine the visited control plane functional entity according to local configuration or by querying the network function repository function (network function repository function, NRF) entity. The specific determination process refers to the existing protocol and will not be repeated here. If AMF receives the home network slice instance identifier from the UE in step 408, AMF also selects the visited control plane functional entity according to the home network slice instance identifier when selecting the visited control plane functional entity, and the selected visited control plane functional entity can communicate with the home network slice instance.

[0150] Step 410: The AMF forwards the PDU session establishment request and the identifier of the home control plane function entity to the visited control plane function entity.

[0151] Step 411: The visited control plane function entity sends a PDU session establishment request to the home control plane function entity according to the identifier of the home control plane function entity.

[0152] Step 412: Establish a PDU session in the network slice instance corresponding to the PDN connection.

[0153] The subsequent process of establishing a PDU session is the same as that of the existing protocol and will not be repeated here.

[0154] In an embodiment of the present application, when the UE has established a PDN connection in the 4G network, the home control plane functional entity determines the network slice information corresponding to when the established PDN connection is switched to 5G and sends it to the UE through the PCO. When the UE subsequently registers with the 5GC, it carries the above-mentioned network slice information mapped to the network slice information of the visited network slice, thereby helping the 5GC to select the 5G network slice corresponding to the established PDN connection, thereby ensuring that the IP address of the session remains unchanged.

[0155] Among them, the above Figure 3 and Figure 4 In the embodiment, the actions of each network element (such as a terminal, a control plane functional entity, etc.) can be performed by Figure 2 The processor 201 in the communication device 200 shown calls the application code stored in the memory 203 for execution, and the embodiment of the present application does not impose any limitation on this.

[0156] The above mainly introduces the solution provided by the embodiment of the present application from the perspective of the interaction between various network elements. It can be understood that in order to realize the above functions, the above-mentioned terminals, AMFs, control plane functional entities and other devices include hardware structures and / or software modules corresponding to the execution of each function. Those skilled in the art should easily realize that, in combination with the units and algorithm steps of each example described in the embodiments disclosed herein, the present application can be implemented in the form of hardware or a combination of hardware and computer software. Whether a function is executed in the form of hardware or computer software driving hardware depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of this application.

[0157] In the embodiment of the present application, the functional modules of devices such as terminals and control plane functional entities can be divided according to the above method examples. For example, each functional module can be divided according to each function, or two or more functions can be integrated into one processing module. The above integrated modules can be implemented in the form of hardware or in the form of software functional modules. It should be noted that the division of modules in the embodiment of the present application is schematic and is only a logical functional division. In actual implementation, there may be other division methods.

[0158] For example, when the functional modules are divided in an integrated manner, Figure 5 1 is a schematic diagram showing the structure of a device 500. The device 500 may be the terminal in the above embodiment, or a chip in the terminal, which is not specifically limited in the present embodiment. Figure 5 As shown, the device includes: a receiving module 501 and a sending module 502; wherein, the receiving module 501 is used to receive the network slice information corresponding to the established packet data network PDN connection when it is switched to the 5G network from the control plane functional entity; the network slice information corresponding to the established PDN connection when it is switched to the 5G network includes the single network slice selection auxiliary information S-NSSAI of the network slice corresponding to the established PDN connection when it is switched to the 5G network; the sending module 502 is used to send a packet data unit PDU session establishment request, wherein the PDU session establishment request includes the S-NSSAI of the network slice corresponding to when the first PDN connection is switched to the 5G network and the data network name DNN corresponding to when the first PDN connection is switched to the 5G network; the first PDN connection is any one of the established PDN connections.

[0159] Optionally, when the established packet data network PDN connection is switched to the 5G network, the corresponding network slice information is carried in the protocol configuration item PCO message.

[0160] Optionally, the receiving module 501 is also used to receive indication information from the control plane functional entity, where the indication information is used to indicate that the network slice information received from the control plane functional entity is home network slice information.

[0161] The terminal also includes: a mapping module; the mapping module is used to map the S-NSSAI of the home network slice corresponding to when the PDN connection requested to be switched is switched to 5G to the S-NSSAI of the visited network slice corresponding to when the PDN connection requested to be switched is switched to 5G according to the correspondence between the S-NSSAI of the home network slice and the S-NSSAI of the visited network slice.

[0162] Optionally, the network slice information corresponding to when the established PDN connection is switched to the 5G network also includes the identifier NSI-ID of the network slice instance corresponding to when the established PDN connection is switched to the 5G network.

[0163] In a possible implementation, the sending module 502 is further used to send a capability indication to the control plane function entity, where the capability indication is used to indicate that the terminal can switch to the 5G network.

[0164] The device also includes a determination module, which is used to determine a PDN connection among the established PDN connections that can be switched to a 5G network, wherein the first PDN connection is any one of the PDN connections that can be switched to 5G.

[0165] The device also includes a determination module 503, and the determination module 503 is used to determine the PDN connection that can be switched to the 5G network among the established PDN connections, and the first PDN connection is any one of the PDN connections that can be switched to 5G. In a possible implementation, the determination module 503 is specifically used to send a registration request, and the registration request includes the network slice information corresponding to when the PDN connection that the terminal requests to switch is switched to the 5G network, wherein the PDN connection that the terminal requests to switch is a part or all of the PDN connections in the established PDN connection; receive a registration response, and the registration response includes the S-NSSAI of the network slice that the terminal is allowed to access; determine the PDN connection that can be switched to the 5G network according to the S-NSSAI corresponding to when the PDN connection that the terminal requests to switch is switched to the 5G network and the S-NSSAI of the network slice that is allowed to access.

[0166] Optionally, the PCO message also includes the DNN corresponding to when the first PDN connection is switched to the 5G network, and the PDU session establishment request also includes the access point name APN corresponding to the first PDN connection.

[0167] Among them, all relevant contents of each step involved in the above method embodiment can be referred to the functional description of the corresponding functional module and will not be repeated here.

[0168] In this embodiment, the device 500 is presented in the form of dividing various functional modules in an integrated manner. The "module" here can refer to an application-specific integrated circuit (ASIC), a circuit, a processor and memory that executes one or more software or firmware programs, an integrated logic circuit, and / or other devices that can provide the above functions. In a simple embodiment, those skilled in the art can imagine that the device 500 can be used Figure 2 The form shown.

[0169] for example, Figure 2 The processor 201 in the apparatus 500 can call the computer-executable instructions stored in the memory 203 to enable the apparatus 500 to execute the session establishment method in the above method embodiment.

[0170] Specifically, Figure 5 The functions / implementation processes of the receiving module 501, the sending module 502 and the determining module 503 can be realized by Figure 2 The processor 201 in the memory 203 calls the computer execution instructions stored in the memory 203 to implement it.

[0171] Optionally, when the device 500 is a chip, the functions / implementation processes of the receiving module 501, the sending module 502, and the determining module 503 may also be implemented via pins or circuits. Optionally, when the device 500 is a chip, the memory 203 may be a storage unit within the chip, such as a register or cache. Of course, when the device 500 is a terminal, the memory 203 may be a storage unit within the terminal located outside the chip, which is not specifically limited in this embodiment of the present application.

[0172] Since the device provided in the embodiment of the present application can be used to execute the above-mentioned session establishment method, the technical effects that can be obtained can be referred to the above-mentioned method embodiment and will not be repeated here.

[0173] Figure 6A structural schematic diagram of a control plane functional entity 600 is shown. The control plane functional entity 600 includes: a sending module 601 and a receiving module 602; the sending module 601 is used to send the network slice information corresponding to the established packet data network PDN connection when it is switched to the 5G network; the network slice information corresponding to the established PDN connection when it is switched to the 5G network includes the single network slice selection auxiliary information S-NSSAI of the network slice corresponding to the established PDN connection; the receiving module 602 is used to receive a packet data unit PDU session establishment request, wherein the PDU session establishment request includes the S-NSSAI of the network slice corresponding to the first PDN connection and the data network name DNN corresponding to the first PDN connection when it is switched to the 5G network; the first PDN connection is any one of the established PDN connections.

[0174] Optionally, the network slice information corresponding to when the established packet data network PDN connection is switched to the 5G network is carried in the protocol configuration item PCO message. The PCO message also includes the DNN corresponding to when the established PDN connection is switched to the 5G network.

[0175] Optionally, the control plane functional entity also includes: a determination module; the determination module is used to determine the corresponding network slice information when the established PDN connection is switched to the 5G network based on the access point name APN corresponding to the established PDN connection.

[0176] One possible implementation method is that the sending module 502 is also used to send indication information, and the indication information is used to indicate that the network slice information sent by the control plane functional entity is the home network slice information.

[0177] In the case that the established PDN is established under the home routing scenario, the sending module 502 is specifically used to: determine the network slice information of the home location corresponding to when the established PDN connection is switched to 5G; map the network slice information of the home location corresponding to when the established PDN connection is switched to 5G to the network slice information of the visited location; and send the network slice information of the visited location corresponding to when the established PDN connection is switched to 5G to the terminal as the slice information corresponding to when the established PDN connection is switched to 5G.

[0178] Optionally, the network slice information corresponding to when the established PDN connection is switched to the 5G network also includes the identifier NSI-ID of the network slice instance corresponding to when the established PDN connection is switched to the 5G network.

[0179] In one possible implementation, the receiving module 602 is further used to receive a capability indication from the terminal, where the capability indication is used to indicate that the terminal can switch to a 5G network.

[0180] Among them, all relevant contents of each step involved in the above method embodiment can be referred to the functional description of the corresponding functional module and will not be repeated here.

[0181] The control plane functional entity 600 can be implemented on an integrated circuit, a radio frequency integrated circuit, a printed circuit board, or the like. The device can be a standalone device or part of a larger device. In this embodiment, the control plane functional entity 600 is presented in the form of functional modules divided in an integrated manner. The "module" here can refer to a specific ASIC, circuit, a processor and memory that executes one or more software or firmware programs, an integrated logic circuit, and / or other devices that can provide the aforementioned functions.

[0182] In a simple embodiment, those skilled in the art can imagine that the control plane function entity 600 can be implemented as Figure 2 For example, Figure 2 The processor 201 in the control plane function entity 600 can call the computer execution instructions stored in the memory 203 to enable the control plane function entity 600 to execute the session establishment method in the above method embodiment.

[0183] In the above embodiments, all or part of the embodiments may be implemented by software, hardware, firmware, or any combination thereof. When implemented using a software program, all or part of the embodiments may be implemented in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of the present application are generated. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another computer-readable storage medium. For example, the computer instructions may be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via a wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) method. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or data center that includes one or more media integrated therein. The available medium may be a magnetic medium (eg, a floppy disk, a hard disk, a magnetic tape), an optical medium (eg, a DVD), or a semiconductor medium (eg, a solid state disk (SSD)).

[0184] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the claimed application, those skilled in the art can understand and implement other changes to the disclosed embodiments by reviewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple situations. A single processor or other unit can implement several functions listed in the claims. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0185] Although the present application has been described with reference to specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present application. Accordingly, this specification and the drawings are merely illustrative of the present application as defined by the appended claims and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present application. Obviously, those skilled in the art may make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, the present application is intended to include such modifications and variations as fall within the scope of the claims of the present application and their equivalents.

Claims

1. A session establishment method, characterized in that: The method comprises: The device receives network slice information corresponding to when an established packet data network PDN connection is switched to a 5G network from a control plane function entity; the network slice information corresponding to when the established PDN connection is switched to the 5G network includes single network slice selection auxiliary information S-NSSAI of the network slice corresponding to when the established PDN connection is switched to the 5G network; wherein the device is a terminal or a chip in the terminal; When moving to a 5G network coverage area, the apparatus sends a registration request to an access and mobility management function entity in the 5G network, where the registration request includes a requested S-NSSAI, and the requested S-NSSAI includes an S-NSSAI corresponding to the established PDN connection; and The device receives a registration response from the access and mobility management function entity, where the registration response includes the S-NSSAI corresponding to the network slice to which access is allowed.

2. The method according to claim 1, characterized in that The S-NSSAI corresponding to the network slice allowed for access is obtained based on the subscription data of the device and the S-NSSAI corresponding to the established PDN connection.

3. The method according to claim 2, characterized in that The subscription data of the device includes the S-NSSAI corresponding to the network slice to which the device has subscribed, and the S-NSSAI corresponding to the network slice allowed access is the intersection of the S-NSSAI corresponding to the network slice to which the device has subscribed and the S-NSSAI of the request.

4. The method according to claim 3, characterized in that The requested S-NSSAI also includes other S-NSSAIs requested by the device.

5. The method according to claim 1, wherein Before receiving network slice information corresponding to when an established packet data network PDN connection is switched to a 5G network from a control plane function entity, the method further includes: The device sends a capability indication to the control plane function entity, where the capability indication is used to indicate that the device can switch to a 5G network.

6. The method according to claim 1, wherein When the established PDN connection is switched to the 5G network, the corresponding network slice information is carried in the protocol configuration item PCO message.

7. The method according to claim 6, characterized in that The PCO message is included in a PDN connection establishment response or an attach response of the terminal.

8. The method according to any one of claims 1 to 7, characterized in that: The method further comprises: The device sends a PDU session establishment request, wherein the PDU session establishment request includes the S-NSSAI of the network slice corresponding to when the first PDN connection is switched to the 5G network; the first PDN connection is any one of the established PDN connections.

9. The method according to claim 8, characterized in that The PDU session establishment request also includes the data network name DNN corresponding to when the first PDN connection is switched to the 5G network.

10. The method according to claim 8, characterized in that Before sending the PDU session establishment request, the method further includes: Determine a PDN connection in the established PDN connection that can be switched to a PDN connection in the 5G network.

11. The method according to claim 10, characterized in that The determining a PDN connection among the established PDN connections that can be switched to a 5G network includes: According to the S-NSSAI corresponding to the network slice allowed for access and the network slice information corresponding to when the PDN connection requested to be switched is switched to 5G, it is determined that the PDN connection that can be switched to the 5G network is determined.

12. The method according to any one of claims 1 to 7, characterized in that: The device also receives indication information from the control plane functional entity, wherein the indication information is used to indicate that the S-NSSAI received from the control plane functional entity is the home location S-NSSAI corresponding to the established PDN connection; then the S-NSSAI corresponding to the established PDN connection included in the requested S-NSSAI is the S-NSSAI of the visited location; the S-NSSAI corresponding to the network slice allowed for access included in the registration response is the S-NSSAI allowed for access by the visited location; wherein, the S-NSSAI of the visited location corresponding to the established PDN connection is obtained by the device according to the S-NSSAI mapping of the home location corresponding to the established PDN connection.

13. The method according to claim 12, characterized in that The indication information is the home operator network identifier PLMNID.

14. The method according to claim 12, characterized in that The method further comprises: According to the correspondence between the S-NSSAI of the home network slice and the S-NSSAI of the visited network slice, the S-NSSAI of the home network slice corresponding to the established PDN connection is mapped to the S-NSSAI of the visited network slice corresponding to the established PDN connection.

15. The method according to claim 12, characterized in that Before receiving network slice information corresponding to when an established packet data network PDN connection is switched to a 5G network from a control plane function entity, the method further includes: The device sends a capability indication to the control plane function entity, where the capability indication is used to indicate that the device can switch to a 5G network.

16. The method according to claim 12, characterized in that The method further comprises: When it is necessary to switch the first PDN connection to the 5G network, the device sends a session establishment request, where the session establishment request includes the S-NSSAI of the visited location corresponding to the established PDN connection; the first PDN connection is any one of the established PDN connections.

17. The method according to claim 16, characterized in that The method further comprises: Before sending the session establishment request, determine that the first PDN connection is a PDN connection that can be switched to a 5G network.

18. The method according to any one of claims 1 to 7, characterized in that: The control plane function entity is the PDN gateway control plane function / session management function (PGW-C / SMF).

19. A session establishment method, characterized in that: The method comprises: The control plane function entity sends to the terminal the network slice information corresponding to when the packet data network PDN connection established by the terminal is switched to the 5G network; the network slice information corresponding to when the established PDN connection is switched to the 5G network includes the single network slice selection auxiliary information S-NSSAI of the network slice corresponding to the established PDN connection; The access and mobility management function entity receives a registration request initiated by the terminal moving into the coverage of the 5G network, where the registration request includes requested single network slice selection assistance information S-NSSAI, and the requested S-NSSAI includes the S-NSSAI corresponding to the established PDN connection; The access and mobility management function entity determines, according to the requested S-NSSAI and the subscription data of the terminal, the S-NSSAI corresponding to the network slice that the terminal is allowed to access; The access and mobility management function entity sends a registration response to the terminal, where the registration response includes the S-NSSAI corresponding to the network slice allowed access.

20. The method according to claim 19, characterized in that The subscription data of the terminal includes the S-NSSAI corresponding to the network slice to which the terminal has subscribed, and the S-NSSAI corresponding to the network slice allowed access is the intersection of the S-NSSAI corresponding to the network slice to which the terminal has subscribed and the S-NSSAI of the request.

21. The method according to claim 19, wherein The method further comprises: The control plane function entity receives a packet data unit PDU session establishment request, wherein the PDU session establishment request includes the S-NSSAI of the network slice corresponding to the first PDN connection; the first PDN connection is any one of the established PDN connections.

22. The method according to claim 21, characterized in that The PDU session establishment request also includes the data network name DNN corresponding to when the first PDN connection is switched to the 5G network.

23. The method according to any one of claims 19 to 22, characterized in that: When the established packet data network PDN connection is switched to the 5G network, the corresponding network slice information is carried in the protocol configuration item PCO message.

24. The method according to claim 23, wherein The PCO message is included in a PDN connection establishment response or an attach response of the terminal.

25. The method according to any one of claims 19 to 22, characterized in that: The method also includes: the control plane functional entity determines the corresponding network slice information when the established PDN connection is switched to the 5G network based on the access point name APN corresponding to the established PDN connection.

26. The method according to any one of claims 19 to 22, characterized in that: The control plane function entity also sends indication information, where the indication information is used to indicate that the network slice information sent by the control plane function entity is home network slice information.

27. The method according to any one of claims 19 to 22, characterized in that: In the case where the established PDN is established in a home routing scenario, the control plane function entity sends the network slice information corresponding to the established packet data network PDN connection when switching to the 5G network, specifically including: The control plane function entity determines the network slice information of the home location corresponding to when the established PDN connection is switched to 5G; Mapping the network slice information of the home location corresponding to the switching of the established PDN connection to the network slice information of the visited location; The network slice information of the visited location corresponding to when the established PDN connection is switched to 5G is sent to the terminal as the slice information corresponding to when the established PDN connection is switched to 5G.

28. The method according to any one of claims 19 to 22, characterized in that: The network slice information corresponding to when the established PDN connection is switched to the 5G network also includes the identifier NS I-ID of the network slice instance corresponding to when the established PDN connection is switched to the 5G network.

29. The method according to any one of claims 19 to 22, characterized in that: Before the control plane function entity sends the network slice information corresponding to when the established packet data network PDN connection is switched to the 5G network to the terminal, the method includes: The control plane function entity receives a capability indication from the terminal, where the capability indication is used to indicate that the terminal can switch to a 5G network.

30. A communication device, characterized in that: The method comprises a module for executing the method according to any one of claims 1 to 18.

31. The device according to claim 30, characterized in that The device includes a terminal or a chip in the terminal.

32. A communication device, characterized in that: The device includes a processor and a memory; The memory is used to store computer-executable instructions. When the device is running, the processor executes the computer-executable instructions stored in the memory, so that the device executes the session establishment method according to any one of claims 1 to 18.

33. The device according to claim 32, characterized in that The device includes a terminal or a chip in the terminal.

34. A computer storage medium, characterized in that The computer-readable storage medium stores instructions, which, when executed on a computer, enable the computer to execute the method according to any one of claims 1 to 18.

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