CN112188608A

CN112188608A - Method, device, system and chip for synchronizing PDU session state

Info

Publication number: CN112188608A
Application number: CN201910598920.0A
Authority: CN
Inventors: 王志明; 段小嫣; 魏珍荣; 丁明
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2019-07-04
Filing date: 2019-07-04
Publication date: 2021-01-05
Anticipated expiration: 2039-07-04
Also published as: WO2021000938A1; CN112188608B

Abstract

A method, a device, a system and a chip for synchronizing PDU session state relate to the field of 5G NR and the field of artificial intelligence communication, so as to ensure that the session state of terminal equipment and network maintenance is consistent. The method comprises the following steps: the method comprises the steps that a terminal device sends a first request for requesting establishment of PDU session to a core network element, the number of PDU session of the terminal device in an activated state is N, N is an integer larger than or equal to 1, the core network element responds to the first request, the number M of the PDU session of the terminal device in the activated state is determined to reach the maximum value, M is larger than N, the core network element sends a first response to the terminal device, the first response comprises information for indicating the state of all PDU sessions maintained by a mobility management network element for the terminal device and indication information for indicating the number of the established PDU session of the terminal device to reach the maximum value, and then the terminal device can synchronize the state of the PDU session according to the first PDU session state information.

Description

Method, device, system and chip for synchronizing PDU session state

Technical Field

The present application relates to the field of mobile communications technologies, and in particular, to a method, an apparatus, a system, and a chip for synchronizing PDU session status.

Background

At present, the number of the current day,in the fifth generation (5)^thgeneration, 5G) communication, service data is carried in the form of "session" at the bottom layer, one session represents one data "path" between the terminal device and the network, and multiple sessions can be established between the terminal device and the network on the premise that the maximum concurrent session is not exceeded. To ensure that the sessions established between the terminal device and the network do not exceed a maximum value, the terminal device and the network need to maintain session states and the number of established sessions, respectively.

In the prior art, session states respectively maintained by a terminal device side and a network side may be inconsistent, which causes inconsistency of established session numbers respectively maintained by the terminal device side and the network side, thereby affecting session management. Therefore, how to ensure that the session states respectively maintained by the terminal device side and the network side are consistent is an urgent technical problem to be solved.

Disclosure of Invention

Embodiments of the present application provide a method, an apparatus, a system, and a chip for synchronizing a Packet Data Unit (PDU) session state, so as to ensure that session states maintained by a terminal device side and a network side are consistent, and improve session management efficiency.

In a first aspect, a method for synchronizing a PDU session state is provided, where a terminal device sends a first request for requesting establishment of a first PDU session to a core network element managing a PDU session of the terminal device, where the number of PDU sessions in an active state of the terminal device is N, and N is an integer greater than or equal to 1; the terminal equipment receives a first response responding to the first request from a core network element, wherein the first response comprises first PDU session state information and maximum value indication information, the first PDU session state information is used for indicating the state of all PDU sessions maintained by the mobility management network element for the terminal equipment, the maximum value indication information is used for indicating that the number of the established PDU sessions maintained for the terminal equipment reaches the maximum value, the number of the PDU sessions in an activated state included by all the PDU sessions is M, and M is an integer larger than N; and the terminal equipment synchronizes the state of the PDU session according to the first PDU session state information.

By adopting the method, the core network element can send the first PDU session state information to the terminal equipment in the message carrying the maximum value indication information, according to the method in the prior art, the core network element does not carry the first PDU session state information in the message carrying the maximum value indication information, the terminal equipment considers that the currently established PDU session reaches the maximum value supported by the network after receiving the maximum value indication information, and then a new session establishment request is not initiated; however, by adopting the method of the present application, the terminal device can determine that the PDU conversation essence established by the terminal device does not reach the maximum value at this time according to the maximum value indication information and the first PDU conversation state information, and the PDU conversation state maintained by the terminal device and the network is inconsistent at this time, and the terminal device can synchronize the state of the PDU conversation according to the first PDU conversation state information at this time.

In one possible design, a terminal device synchronizes the status of a PDU session according to first PDU session status information, including: and the terminal equipment indicates the first PDU session state information as an inactive state and maintains the state of the PDU session in the active state, the state is changed from the active state to the inactive state, and the PDU session is released.

In one possible design, after synchronizing the status of the PDU session according to the first PDU session status information, the terminal device further includes: and the terminal equipment sends a PDU session related message to the network element of the core network, wherein the PDU session related message comprises second PDU session state information, and the second PDU session state information is used for indicating the states of all PDU sessions of the terminal equipment.

In one possible design, the PDU session related message is a message carrying a PDU session setup request message, a PDU session release request message, or a PDU session modification request message, or the PDU session related message is a PDU session setup request message, a PDU session release request message, or a PDU session modification request message.

In a second aspect, a method for synchronizing PDU session status is provided, where the method includes a core network element receiving a first request from a terminal device for establishing a first protocol data unit PDU session; the core network element responds to the first request and determines that the number of PDU sessions in an activated state maintained for the terminal equipment reaches the maximum value; and the core network element sends a first response responding to the first request to the terminal equipment, wherein the first response comprises first PDU session state information and maximum value indication information, the first PDU session state information is used for indicating the state of all PDU sessions maintained by the mobility management element for the terminal equipment, and the maximum value indication information is used for indicating that the number of the established PDU sessions maintained for the terminal equipment reaches the maximum value.

In one possible design, after the network element in the core network sends the first response to the terminal device, the method further includes: the core network element receives a PDU session related message from the terminal equipment, the PDU session related message carries second PDU session state information, the second PDU session state information is used for indicating the state of all PDU sessions of the terminal equipment, the core network element executes corresponding processing according to the PDU session related message, and synchronizes the state of the PDU session maintained by the terminal equipment according to the second PDU session state information.

In one possible design, a core network element is a mobility management element, a PDU session related message is a message carrying a PDU session establishment request message, a PDU session release request message, or a PDU session modification message, and based on the design, the core network element synchronizes a state of a PDU session maintained for a terminal device according to second PDU session state information, including: and the mobility management network element indicates the second PDU session state information as an inactive state and maintains the PDU session state of the active state for the terminal equipment, and the active state is changed into the inactive state.

In one possible design, the mobility management network element sends session release information to the session management network element that manages the PDU session in which the second PDU session state information indicates the inactive state and the mobility management network element maintains the active state for the terminal device, where the session release information is used to indicate the session management network element to release the PDU session in which the second PDU session state information indicates the inactive state and the mobility management network element maintains the active state for the terminal device.

In one possible design, the PDU session related message is a PDU session setup request message;

the core network element executes corresponding processing according to the PDU session related message, and the processing comprises the following steps:

and the core network element establishes the PDU session according to the PDU session establishment request message. Alternatively, the first and second electrodes may be,

the PDU conversation related message is a PDU conversation release request message;

and the core network element releases the PDU session according to the PDU session release request message. Alternatively, the first and second electrodes may be,

the PDU conversation related message is a PDU conversation modification message;

and the core network element modifies the state of the PDU session according to the PDU session modification message.

In a third aspect, a chip is provided, which is applied to a terminal device, and includes a baseband processor, where the baseband processor is configured to send a first request for requesting establishment of a first PDU session to a core network element managing a PDU session of the terminal device, where the number of PDU sessions in an active state of the terminal device is N, where N is an integer greater than or equal to 1, receive a first response from the core network element in response to the first request, where the first response includes first PDU session status information and maximum indication information, the first PDU session status information is used to indicate a status of all PDU sessions maintained by a mobility management network element for the terminal device, the maximum indication information is used to indicate that the number of established PDU sessions maintained for the terminal device has reached a maximum value, the number of PDU sessions in an active state of all PDU sessions included by all PDU sessions is M, and M is an integer greater than N, synchronizing the state of the PDU session according to the first PDU session state information.

In one possible design, the baseband processor, when synchronizing the status of the PDU session according to the first PDU session status information, is specifically configured to: and indicating the first PDU session state information as the inactive state and maintaining the state of the PDU session in the active state by the terminal equipment, changing the state from the active state to the inactive state, and releasing the PDU session.

In one possible design, the baseband processor is further to:

after synchronizing the state of the PDU session according to the first PDU session state information, sending a PDU session related message to a core network element, wherein the PDU session related message comprises second PDU session state information, and the second PDU session state information is used for indicating the state of all PDU sessions of the terminal equipment.

A fourth aspect provides a system, including a terminal device and a core network element, where the terminal device sends a first request for requesting establishment of a first protocol data unit PDU session to the core network element, the number of PDU sessions in an active state of the terminal device is N, and N is an integer greater than or equal to 1; the core network element responds to the first request, and determines that the number M of the PDU sessions in the activated state maintained for the terminal equipment reaches the maximum value, wherein M is an integer larger than N; the core network element sends a first response responding to the first request to the terminal equipment, wherein the first response comprises first PDU session state information and maximum value indication information, the first PDU session state information is used for indicating the state of all PDU sessions maintained by the mobility management element for the terminal equipment, and the maximum value indication information is used for indicating that the number of the established PDU sessions maintained for the terminal equipment reaches the maximum value; and the terminal equipment synchronizes the state of the PDU session according to the first PDU session state information.

In one possible design, after synchronizing the status of the PDU session according to the first PDU session status information, the terminal device further includes: the terminal equipment sends a PDU session related message to a core network element, wherein the PDU session related message carries second PDU session state information which is used for indicating the state of all PDU sessions of the terminal equipment; and the core network element executes corresponding processing according to the PDU session related message and synchronizes the state of the PDU session maintained for the terminal equipment according to the second PDU session state information.

In one possible design, the core network element is a mobility management element, and based on the design, the core network element synchronizes a state of a PDU session maintained for the terminal device according to the second PDU session state information, including: and the mobility management network element indicates the second PDU session state information as an inactive state and maintains the PDU session state of the active state for the terminal equipment, and the active state is changed into the inactive state.

In one possible design, the PDU session related message is a message carrying a PDU session setup request message, a PDU session release request message, or a PDU session modify request message.

In a fifth aspect, there is provided an apparatus having functionality to implement the method of the first aspect. The functions can be realized by hardware, and the functions can also be realized by executing corresponding software by hardware. The hardware or software includes one or more modules corresponding to the above-described functions.

In one possible design, the apparatus may include a processor and a memory in a structure, and the processor is configured to perform the method mentioned in the first aspect. The memory is coupled to the processor and holds the program instructions and data necessary for the device.

In a sixth aspect, there is provided an apparatus having functionality to carry out the method of the second aspect. The functions can be realized by hardware, and the functions can also be realized by executing corresponding software by hardware. The hardware or software includes one or more modules corresponding to the above-described functions.

In one possible design, the apparatus may include a processor and a memory in a structure, and the processor is configured to execute the method of the second aspect. The memory is coupled to the processor and holds the program instructions and data necessary for the device.

In a seventh aspect, the present application provides a communication system comprising the apparatus of the fifth aspect and the apparatus of the sixth aspect.

In an eighth aspect, the present application further provides a computer storage medium, where the computer storage medium stores computer-executable instructions, and when the computer-executable instructions are called by a computer, the computer executes the method provided by the first aspect or any one of the designs of the first aspect, or the method provided by the second aspect or any one of the designs of the second aspect.

In a ninth aspect, this embodiment further provides a computer program product, which has instructions stored therein, and when the computer program product runs on a computer, causes the computer to execute the method described in the above first aspect or any one of the possible designs of the above first aspect or the method provided in the above second aspect or any one of the possible designs of the above second aspect.

In a tenth aspect, an embodiment of the present application further provides a chip, coupled to the memory, for reading and executing program instructions stored in the memory to implement any one of the methods mentioned in the first aspect or the second aspect.

Drawings

Fig. 1 is a schematic diagram of a network architecture to which the present application is applicable;

fig. 2 is a schematic diagram of a PDU session state transition provided in an embodiment of the present application;

fig. 3 is a schematic diagram of a PDU session establishment procedure provided in an embodiment of the present application;

fig. 4a is a schematic diagram of a PDU session release process provided in an embodiment of the present application;

fig. 4b is a schematic diagram of another PDU session release flow provided in this embodiment;

fig. 5 is a schematic format diagram of a PDU session status information element according to an embodiment of the present application;

fig. 6a is a schematic diagram of a PDU session establishment procedure provided in an embodiment of the present application;

fig. 6b is a schematic diagram of a PDU session release process provided in an embodiment of the present application;

fig. 7 is a flowchart illustrating a method for synchronizing a PDU session status according to an embodiment of the present application;

fig. 8 is a flowchart illustrating a further method for synchronizing a PDU session status according to an embodiment of the present application;

fig. 9a is a schematic flowchart of another method for synchronizing a PDU session status according to an embodiment of the present application;

fig. 9b is a schematic flowchart of another method for synchronizing a PDU session status according to an embodiment of the present application;

fig. 10a is a schematic flowchart of another method for synchronizing a PDU session status according to an embodiment of the present application;

fig. 10b is a flowchart illustrating a further method for synchronizing a PDU session status according to an embodiment of the present application;

fig. 11 is a schematic structural diagram of a terminal device according to an embodiment of the present application;

fig. 12 is a schematic structural diagram of another terminal device provided in an embodiment of the present application;

fig. 13 is a schematic structural diagram of a core network element according to an embodiment of the present application;

fig. 14 is a schematic structural diagram of another core network element according to an embodiment of the present application.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more clear, the present application will be further described in detail with reference to the accompanying drawings. The particular methods of operation in the method embodiments may also be applied to apparatus embodiments or system embodiments. In the description of the present application, unless otherwise specified, "a plurality" means two or more, and "at least one" means one or more. In addition, it should be understood that in the embodiments of the present application, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or order. "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone.

The network architecture and the service scenario described in this application are for more clearly illustrating the technical solution of the embodiment of the application, and do not constitute a limitation to the technical solution provided in the embodiment of the application, and it can be known by those skilled in the art that the technical solution provided in the embodiment of the application is also applicable to similar technical problems along with the evolution of the network architecture and the appearance of a new service scenario.

Please refer to fig. 1, which is a schematic diagram of a network architecture applicable to the present application, and fig. 1 is a schematic diagram of a 5G network architecture based on a service architecture. The 5G network architecture shown in fig. 1 may include three parts, which are a terminal device part, a Data Network (DN) and an operator network part.

The operator network may also be referred to as a mobile communication network, and is mainly a network in which a Mobile Network Operator (MNO) provides a mobile broadband access service for a user. The operator network described in the embodiment of the present application may specifically be a network meeting the requirements of the third generation partnership project (3 GPP) standard, which is referred to as a 3GPP network for short. Typically, the 3GPP network is operated by an operator, including but not limited to a 5G network, a fourth generation mobile communication technology (4th-generation, 4G) network, a third generation mobile communication technology (3rd-generation, 3G) network, and a second generation wireless telephone technology (2G) network, etc. In fig. 1 of the present application, an operator network is illustrated as a 5G network.

The 5G operator network may include a network open function (NEF) network element, a network storage function (NRF) network element, a Policy Control Function (PCF) network element, a Unified Data Management (UDM) network element, AN Application Function (AF) network element, AN authentication server function (AUSF) network element, AN access and mobility management function (AMF) network element, a Session Management Function (SMF) network element, a radio access network (radio) access network, (R) AN), and a user plane function (user plane function, UPF) network element, etc. The part of the operator network other than the (radio) access network is referred to as the core network.

The terminal device of the present application may provide telephony and/or data services, and may be a wired or wireless terminal device. The wireless terminal device may be a mobile phone, a computer, a tablet computer, a Personal Digital Assistant (PDA), a Mobile Internet Device (MID), a wearable device, an electronic book reader (e-book reader), and the like. As another example, the wireless terminal device may be a mobile station (mobile station), an access point (access point). A User Equipment (UE) is a kind of terminal equipment, and for convenience, the terminal equipment will be described in the following description.

The terminal device may establish a connection with the carrier network through an interface (e.g., N1, etc.) provided by the carrier network, and use data and/or voice services provided by the carrier network. The terminal device may also access the DN via an operator network, use operator services deployed on the DN, and/or services provided by a third party. The third party may be a service party other than the operator network and the terminal device, and may provide other services such as data and/or voice for the terminal device. The specific expression form of the third party may be determined according to an actual application scenario, and is not limited herein.

The AN is a sub-network of the operator network, and is AN implementation system between the service node and the terminal device in the operator network. The terminal equipment is to be accessed to the operator network, firstly passes through the AN, and then can be connected with the service node of the operator network through the AN. AN device in this application is a device for providing a wireless communication function for a terminal device, and AN access network device includes but is not limited to: next generation base station (G node B, gNB), evolved node B (eNB), Radio Network Controller (RNC), Node B (NB), Base Station Controller (BSC), Base Transceiver Station (BTS), home base station (e.g., home evolved node B, or home node B, HNB), Base Band Unit (BBU), transmission point (TRP), Transmission Point (TP), mobile switching center, etc. in 5G.

The AMF network element is a control plane network element provided by an operator network and is responsible for access control and mobility management of terminal equipment accessing the operator network, for example, including functions of mobility state management, user temporary identity assignment, user authentication and authorization, and the like.

The SMF network element is a control plane network element provided by an operator network and is responsible for managing a Protocol Data Unit (PDU) session of the terminal device. A PDU session is a channel for transmitting PDUs, and a terminal device needs to transfer PDUs to and from the DN through the PDU session. For example, when a terminal device establishes a communication with a DN, a PDU session may be established between the terminal device and the DN to establish a data transmission channel, where the PDU session refers to a connection between the terminal device and the DN that provides a PDU connection service. The PDU session is established, maintained, deleted and the like by the SMF network element. The SMF network element includes session management (e.g., session establishment, modification, and release, including tunnel maintenance between the UPF and the AN), selection and control of the UPF network element, Service and Session Continuity (SSC) mode selection, roaming, and other session-related functions.

The UPF network element is a gateway provided by the operator, which is a gateway for the operator network to communicate with the DN. The UPF network element includes user plane related functions such as packet routing and transmission, packet detection, service usage reporting, quality of service (QoS) processing, lawful interception, uplink packet detection, downlink packet storage, and the like.

A DN, which may also be referred to as a Packet Data Network (PDN), is a network located outside an operator network, where the operator network may access multiple DNs, and multiple services may be deployed on the DNs, so as to provide services such as data and/or voice for a terminal device. For example, the DN is a private network of a certain intelligent factory, a sensor installed in a workshop of the intelligent factory can be a terminal device, a control server of the sensor is deployed in the DN, and the control server can provide services for the sensor. The sensor can communicate with the control server, obtain the instruction of the control server, transmit the sensor data gathered to the control server, etc. according to the instruction. For another example, the DN is an internal office network of a company, the mobile phone or computer of the employee of the company may be a terminal device, and the mobile phone or computer of the employee may access information, data resources, and the like on the internal office network of the company.

The UDM network element is a control plane network element provided by an operator, and is responsible for storing information such as a subscriber permanent identifier (SUPI), a credential (trusted identity), a security context (security context), and subscription data of a subscribed user in an operator network. These information stored by the UDM network element can be used for authentication and authorization of the terminal device to access the operator network. The subscriber of the operator network may be specifically a user using a service provided by the operator network, for example, a user using a mobile phone core card of china telecommunications, or a user using a mobile phone core card of china mobile, and the like. The SUPI of the subscriber may be the number of the mobile phone core card. The credentials and security context of the subscriber may be a small file stored with an encryption key of the core card of the mobile phone or information related to encryption of the core card of the mobile phone, and used for authentication and/or authorization. The security context may be data (cookie) or token (token) stored on the user's local terminal (e.g., cell phone), etc. The subscription data of the subscriber may be a service associated with the mobile phone core card, such as a traffic package or a network using the mobile phone core card. It should be noted that the information related to the permanent identifier, the credentials, the security context, the authentication data (cookie), and the token equivalent authentication and authorization are not distinguished or limited in the present application for convenience of description. Unless otherwise specified, the embodiments of the present application will be described in the context of security, but the embodiments of the present application are also applicable to authentication, and/or authorization information in other expressions.

The AUSF network element is a control plane network element provided by an operator, and is generally used for primary authentication, i.e., authentication between a terminal device (subscriber) and an operator network. After receiving an authentication request initiated by a subscriber, the AUSF network element authenticates and/or authorizes the subscriber through authentication information and/or authorization information stored in the UDM network element, or generates authentication and/or authorization information of the subscriber through the UDM network element. The AUSF network element may feed back authentication information and/or authorization information to the subscriber.

The NEF network element is a control plane network element provided by the operator. The NEF network element opens the external interface of the operator network to the third party in a secure manner. When the SMF network element needs to communicate with a network element of a third party, the NEF network element may serve as a relay for the communication between the SMF network element and the network element of the third party. When the NEF network element is used as a relay, it can be used as a translation of the identification information of the subscriber and a translation of the identification information of the network element of the third party. For example, when NEF sends the SUPI of a subscriber from the carrier network to a third party, the SUPI may be translated into its corresponding external Identity (ID). Conversely, when the NEF element sends an external ID (the third party's element ID) to the operator network, it can be translated to SUPI.

The PCF network element is a control plane function provided by the operator for providing the policy of the PDU session to the SMF network element. The policies may include charging related policies, QoS related policies, authorization related policies, and the like.

A Network Slice Selection Function (NSSF) network element (not shown in the figure) is responsible for determining a Network Slice Instance (NSI), selecting an AMF network element, and the like.

It should be noted that, the network element referred to in the embodiments of the present application may also be referred to as a function or a functional entity, and the present application is not limited thereto. For example, the access and mobility management function network element may also be referred to as an access and mobility management function or an access and mobility management function entity, and the session management function network element may be referred to as a session management function or a session management function entity, etc. The names of the network elements are not limited in this application, and those skilled in the art can replace the names of the network elements with other names to perform the same functions, all of which belong to the protection scope of this application.

It is to be understood that the network element or the function or the functional entity may be a network element in a hardware device, a software function running on dedicated hardware, or a virtualization function instantiated on a platform (e.g., a cloud platform), and the present application is not limited thereto.

In fig. 1, Nnef, Nausf, Nnrf, Npcf, numm, Naf, Namf, Nsmf, N1, N2, N3, N4, and N6 are interface serial numbers. The meaning of these interface sequence numbers can be referred to as that defined in the 3GPP standard protocol, and is not limited herein.

To facilitate understanding of the present disclosure, some communication terms referred to in the present application are explained below.

1) Status of a session

In the embodiment of the present application, a session mainly refers to a PDU session. Please refer to fig. 2, which is a schematic diagram illustrating a PDU session state transition provided in the present application. The 3GPP24.501 protocol specifies the status of the PDU session, wherein the PDU session can be in two stable statuses, active status (active) and inactive status (inactive), the PDU session successfully established is in active status, and the PDU session successfully released is in inactive status, where the inactive status can also be referred to as deactivated status. Of course, besides being in the two stable states of active or inactive, the PDU session may also be in some suspended state when transitioning between the two stable states, as shown in fig. 2. It should be noted that the status of the PDU session in the embodiments of the present application refers to a stable status, and details of the suspend status during transition are not described. For convenience of description, the PDU session in the active state may be referred to as an active PDU session, and the PDU session in the inactive state may be referred to as an inactive PDU session or a deactivated PDU session.

2) PDU session establishment procedure

Please refer to fig. 3, which is a schematic diagram illustrating a PDU session establishment procedure provided in the present application, where fig. 3 includes the following steps:

step 1: the UE sends a PDU session establishment request (PDU session establishment request) message to the SMF, and requests the SMF to establish the PDU session for the SMF. Illustratively, the UE may send a PDU session setup request message to the SMF through the (R) AN and the AMF.

Step 2 a: after receiving a PDU session establishment request message sent by UE, if the SMF determines that the PDU session can be established for the UE, the SMF sends a PDU session establishment acceptance (PDU session establishment accept) message to the UE, the UE receives the PDU session establishment acceptance message from the SMF to complete the establishment of the PDU session, and the PDU session enters an active state at this time. Illustratively, the SMF may receive the PDU session setup request message from the UE through the (R) AN and the AMF, and accordingly, the SMF may transmit the PDU session setup accept message to the UE through the AMF and the (R) AN.

And step 2 b: after receiving a PDU session establishment request message sent by UE, if it is determined that a PDU session cannot be established for the UE, the SMF sends a PDU session establishment rejection (PDU session establishment reject) message to the UE, the UE receives the PDU session establishment rejection message from the SMF, the PDU session establishment fails, and at this time, the PDU session enters an inactive state. Illustratively, the SMF may send a PDU session setup reject message to the UE through the AMF and the (R) AN.

The step 2a and the step 2b are alternatively executed.

3) PDU session release flow

The present application provides two PDU session release approaches, which are described separately below.

Referring to fig. 4a, a PDU session release flow diagram provided in the present application is shown, fig. 4a shows a PDU session release flow initiated by an SMF, and fig. 4a includes the following steps:

step 1: the SMF transmits a PDU session release command (PDU session release command) to the UE. Illustratively, the SMF may send a PDU session release command to the UE through the AMF and the (R) AN.

Step 2: the UE sends a PDU session release complete message to the SMF. Illustratively, the UE may send a PDU session release complete message to the SMF through the (R) AN and the AMF.

In fig. 4a, the SMF may directly send a PDU session release command to the UE to initiate a PDU session release procedure, and after the UE replies a PDU session release completion message to the SMF, the release of the PDU session is completed, and at this time, the PDU session enters an inactive state or a deactivated state.

Referring to fig. 4b, a schematic diagram of another PDU session release procedure provided in the present application is shown in fig. 4b, where fig. 4b shows a PDU session release procedure initiated by a UE, and fig. 4b includes the following steps:

step 1: the UE sends a PDU session release request (PDU session release request) message to the SMF to request the release of the PDU session. In fig. 4b, the UE actively initiates a PDU session release procedure by sending a PDU session release request to the SMF. Illustratively, the UE may send a PDU session release request message to the SMF through the (R) AN and the AMF.

Step 2 a: after receiving a PDU session release request message sent by the UE, if it is determined that the PDU session requested to be released can be released, the SMF executes a release procedure of the PDU session, completes the release of the PDU session, and at this time, the PDU session enters an inactive state or a deactivated state. Illustratively, the SMF may receive the PDU session release request message transmitted by the UE through the (R) AN and the AMF.

And step 2 b: after receiving a PDU session release request message sent by the UE, if it is determined that the PDU session requested to be released cannot be released, the SMF sends a PDU session release reject (PDU session release reject) message to the UE, and the UE receives the PDU session release reject message from the SMF, which fails to release the PDU session. Illustratively, the SMF may send a PDU session release reject message to the UE through the AMF and the (R) AN.

The step 2a and the step 2b are alternatively executed.

4) Maximum maintenance of established PDU sessions

The maximum value and maintenance method of PDU sessions that a UE can establish simultaneously are defined in 6.4.1.5 of the 3GPP24.501 protocol, which is briefly described below.

The 3GPP24.501 protocol specifies that the maximum value of the number of PDU sessions that can be simultaneously established by a UE in a Public Land Mobile Network (PLMN) is determined by the minimum value among "maximum protocol definition value (16)", "maximum PDU session value supported by PLMN", and "upper limit implemented by UE". For example, if the "maximum value of the protocol definition" is 16, the "maximum value of the number of PDU sessions supported by the PLMN" is 12, and the "upper limit of the UE implementation" is 14, the maximum value of the number of PDU sessions that can be simultaneously established by the UE in the PLMN is 12. The PLMN is understood to be the operator network in fig. 1. It is to be understood that "maximum number of PDU sessions supported by a PLMN" may be understood as the maximum number of PDU sessions that the PLMN can support to establish for the UE; the "UE-implemented upper limit" may be understood as a maximum value for the software and/or hardware configuration of the UE such that the UE can support the established PDU session.

In one possible example, if the UE1 determines that the number of currently established PDU sessions does not exceed the "maximum value of protocol definition (16)" and also does not exceed the "upper limit implemented by the UE", at this time, the UE1 may continue to initiate a PDU session establishment request by using the method shown in fig. 3, when the AMF receives the PDU session establishment request sent by the UE1, if the number of established PDU sessions by the UE1 reaches the maximum value of the number of PDU sessions supported by the PLMN, the AMF may reject the PDU session establishment request, and reply a message carrying a cause value of #65 to the UE1, where the cause value of #65 indicates that the number of established PDU sessions has reached the maximum value (maximum number of PDU sessions received), and after the UE1 receives the message carrying the cause value of #65 replied by the AMF, the number of established PDU sessions at this time is considered as the "maximum value of session supported by the PLMN", and the maximum value of the number of PDU sessions that can be simultaneously established in a PLMN by the UE can be determined according to the 3GPP24.501 protocol.

To ensure that the PDU session established between the UE and the network does not exceed the maximum value specified by the 3GPP24.501 protocol, the UE and the network need to maintain the status of the PDU session and the number of established PDU sessions individually. Illustratively, after the UE successfully establishes the PDU session, the UE sets the status of the PDU session to an active status, and adds one to the number of the established PDU sessions maintained, and correspondingly, the core network element (e.g., AMF) sets the status of the PDU session to an active status, and adds one to the number of the established PDU sessions maintained by the UE; on the contrary, when the UE releases the PDU session successfully, the UE sets the status of the PDU session to an inactive state and reduces the number of the established PDU sessions maintained by the UE by one, and correspondingly, the core network element (e.g., AMF) sets the status of the PDU session to an inactive state and reduces the number of the established PDU sessions maintained by the UE by one. The network maintains the number of established PDU sessions, which may be understood as the AMF maintaining the number of PDU sessions in an active state of each UE accessing the core network through the AMF.

In the prior art, session states respectively maintained by a terminal device side and a network side may be inconsistent, so that numbers of sessions in an activated state respectively maintained by the terminal device side and the network side are inconsistent, which causes inconsistency of numbers of established sessions respectively maintained by the terminal device side and the network side, and further affects session management efficiency. Based on this, a method for synchronizing session states maintained by the terminal device and the network is given in the existing protocol, and is described in detail in relation to fig. 5) below.

5) Method for synchronizing all session states of network and terminal equipment

The synchronization of the PDU session status of the terminal device with the network by means of a PDU session status information element (PDU session status IE) is specified in 3GPP 24.501. As shown in fig. 5, which is a schematic format diagram of a PDU session status information element, a value (0/1) of each bit (bit) included in octet3 and octet4 in the IE represents a status of a session, specifically, when the value of the bit is 0, it indicates that a PDU session corresponding to the bit is in an inactive state, and conversely, when the value of the bit is 1, it indicates that the PDU session corresponding to the bit is in an active state. In the prior art, the terminal device and the network can carry the PDU session state information element only through three procedures of SERVICE REQUEST (SERVICE REQUEST), REGISTRATION (REGISTRATION), or NOTIFICATION (NOTIFICATION), so as to achieve the purpose of PDU session state synchronization.

The PDU session synchronization between the terminal device and the network is realized only through the above three procedures, which is not applicable to all communication stages of the interaction between the terminal device and the network, and is not applicable to the PDU session synchronization by using the method in the prior art in some scenarios. It should be noted that the following two scenarios are only described as examples of problems of the prior art, and are not limited to the following scenarios.

Scene one: PDU session establishment scenario

Please refer to fig. 6a, which is a schematic diagram illustrating a PDU session establishment procedure provided in the present application, where fig. 6a includes the following steps:

step 1: and the SMF receives the PDU session establishment request message sent by the UE.

Assuming the initial state, the number of PDU sessions maintained by the UE and the SMF in the active state is N, and the maximum session value supported by the PLMN is N + 1.

Step 2: the SMF sends a PDU session establishment acceptance message to the UE, and the UE does not receive the PDU session establishment acceptance message sent by the SMF due to factors such as environment and the like. At this time, after the SMF sends the PDU session establishment accept message, the SMF considers that the PDU session establishment is successful, the SMF adds 1 to the number of PDU sessions maintained in the active state, and the number of PDU sessions maintained in the active state by the SMF for the UE becomes N + 1.

It should be noted that, after the UE sends the PDU session establishment request message to the SMF, if the response message of the SMF is not received within the preset time, the PDU session establishment request message is resent after the preset time is exceeded, see step 5 in fig. 6 a.

And step 3: and the UE initiates a new PDU session establishment request message again, and the AMF receives the PDU session establishment request message sent by the UE.

And 4, step 4: the AMF determines that the number of the PDU sessions established for the UE at the moment reaches the maximum value N +1 supported by the network, the AMF sends a downlink non-access stratum transmission message carrying a reason value of #65 to the UE, wherein the reason value of #65 indicates that the number of the established PDU sessions reaches the maximum value (maximum number of PDU sessions accessible), after the UE receives the message sent by the AMF, the UE considers that the number of the established PDU sessions currently maintained by the UE is the maximum value of the PDU sessions which can be maintained by the network, namely, the maximum value of the PDU sessions which can be maintained by the network is N, so that the UE cannot continue to initiate new PDU session establishment requests, and the maximum value of the PDU sessions which can be maintained by the actual network is N +1, namely, the UE can continue to initiate new PDU session establishment requests at the actual moment, but the UE cannot continue to initiate new PDU session establishment requests due to the existence of the problems, thereby affecting PDU session management efficiency.

Scene two: PDU session release scenario

Please refer to fig. 6b, which is a schematic diagram illustrating a PDU session release process provided in the present application, where fig. 6b includes the following steps:

step 1: the SMF sends a PDU session release command to the UE, and the UE receives the PDU session release command sent by the SMF.

Assuming the initial state, the number of PDU sessions maintained by the UE and the SMF in the active state is N, and the maximum number of sessions supported by the PLMN is N.

Step 2: and the UE sends a PDU session release completion message to the SMF, and the SMF does not receive the PDU session release completion message sent by the UE. At this time, after the UE sends the PDU session release completion message, the UE considers that the PDU session release is successful, the UE subtracts 1 from the number of the PDU sessions maintained in the active state, and the number of the PDU sessions maintained in the active state by the UE becomes N-1.

It should be noted that, after the SMF sends the PDU session release command to the UE, if the response message of the UE is not received within the preset time, the PDU session release command is sent again after the preset time is exceeded, see step 5 in fig. 6 b.

And step 3: the UE sends a PDU session establishment request message to the AMF, and the AMF receives the PDU session establishment request message sent by the UE.

And 4, step 4: the AMF determines that the number of the PDU sessions established for the UE at the moment reaches a maximum value N supported by the network, the AMF sends a downlink non-access stratum transmission message carrying a reason value of #65 to the UE, wherein the reason value of #65 indicates that the number of the established PDU sessions reaches the maximum value (maximum number of PDU sessions accessible), after the UE receives the message sent by the AMF, the UE considers that the number of the established PDU sessions currently maintained by the UE is the maximum value of the PDU sessions which can be maintained by the network, namely, the maximum value of the PDU sessions which can be maintained by the network is N-1, so that the UE cannot continue to initiate new PDU session establishment requests, and the maximum value of the PDU sessions which can be maintained by the actual network is N, namely, the UE can continue to initiate new PDU session establishment requests at the actual moment, but the UE cannot continue to initiate new PDU session establishment requests due to the existence of the problems, thereby affecting PDU session management efficiency.

For the above scenario one and scenario two, if three flows in the prior art are used to synchronize the PDU session state between the terminal device and the network side, the PDU session state may be synchronized until the next three flows in the prior art occur, but generally, the three flows in the prior art occur in a specific scenario, for example, in a registration scenario or in a service request scenario, and the three flows in the prior art do not occur in time, which results in that the PDU session state between the terminal device and the network side cannot be synchronized in time in the scenario one and scenario two, thereby affecting the PDU session management efficiency.

In view of the above existing problems, an embodiment of the present application provides a method for synchronizing a PDU session state, where by using the method provided by the present application, a core network element may carry PDU session state information in the message carrying the cause value #65, so that a terminal device may find that the session state of the terminal device is inconsistent with the session state of a network side in time, and synchronize the PDU session state of the terminal device in time, so that the PDU session states maintained by the network side and the terminal device side are consistent, and the PDU session (i.e., the established PDU session) states of the terminal device side and the network side in an active state are consistent, so that the number of established PDU sessions maintained by the terminal device side and the network side is consistent, and further, the management efficiency of the PDU session can be improved. It should be noted that the maximum value indication information described later in this application is the cause value #65 described above.

It should be noted that the method for synchronizing the PDU session status provided in the embodiment of the present application can be applied to the network architecture shown in fig. 1. When the method provided by the present application is applied to the network architecture shown in fig. 1, a core network element related to the present application may be an AMF or an SMF in fig. 1, and a terminal device related to the present application may be a UE in fig. 1. The method provided by the present application is not limited to be applied to the network architecture shown in fig. 1, and may be applied to other network architectures.

Please refer to fig. 7, which is a flowchart illustrating a method for synchronizing a PDU session status according to an embodiment of the present application. As shown in fig. 7, the method may include the following process flow.

Step 101: the terminal equipment sends a first request for requesting to establish a first PDU session to a core network element for managing the PDU session of the terminal equipment, wherein the number of the PDU sessions of the terminal equipment in an activated state is N, and N is an integer greater than or equal to 1. In this embodiment of the present application, the core network element may be a mobility management element or a session management element, and hereinafter, the core network element is mainly taken as the mobility management element for example.

Step 102: and the core network element responds to the first request and determines that the number M of the PDU sessions in the activated state maintained for the terminal equipment reaches the maximum value, wherein M is an integer larger than N.

Step 103: and the core network element sends a first response responding to the first request to the terminal equipment, wherein the first response comprises first PDU session state information and maximum value indication information, the first PDU session state information is used for indicating the state of all PDU sessions maintained by the mobility management element for the terminal equipment, and the maximum value indication information is used for indicating that the number of the established PDU sessions maintained for the terminal equipment reaches the maximum value. In the embodiment of the present application, the maximum value indication information refers to the cause value #65 described above. The first PDU session status information refers to the PDU session status information element shown in fig. 5, where "first" is used only to distinguish from "second" PDU session status information appearing hereinafter, without other meaning. Exemplarily, taking a core network element as a mobility management element as an example, assuming that there are 5 PDU sessions of a terminal device, which are PDU session 1, PDU session 2, PDU session 3, PDU session 4 and PDU session 5, respectively, the status of PDU session 1, PDU session 2, PDU session 3, PDU session 4 and PDU session 5 maintained by the terminal device is active, the status of PDU session 5 is inactive, at this time, in step 103, the first PDU session status information sent by the mobility management element to the terminal device may at least include 5 bits, the status of PDU session 1 maintained by the mobility management element as the terminal device may be indicated as active by a value of one of the bits being 1, the status of PDU session 2 maintained by the mobility management element as the terminal device may be indicated as inactive by a value of one of the bits being 0, the state of the PDU session 3 maintained by the mobility management network element for the terminal equipment can be indicated to be active by setting the value of one bit to be 1, the state of the PDU session 4 maintained by the mobility management network element for the terminal equipment can be indicated to be active by setting the value of one bit to be 1, and the state of the PDU session 5 maintained by the mobility management network element for the terminal equipment can be indicated to be inactive by setting the value of one bit to be 0.

Step 104: and the terminal equipment determines that the state of the PDU session maintained by the core network element is inconsistent according to the first PDU session state information and the maximum value indication information. According to the method in the prior art, after receiving the maximum value indication information, the terminal device considers that the number of the PDU sessions currently established by the terminal device reaches the maximum value supported by the network, and by adopting the method in the application, the terminal device can determine that the PDU sessions currently established by the terminal device do not substantially reach the maximum value supported by the network and determine that the states of the PDU sessions maintained by the terminal device and the network element of the core network are inconsistent according to the fact that the number M of the PDU sessions currently established by the terminal device in the activated state indicated by the first PDU session state information is larger than the number N of the PDU sessions currently in the activated state of the terminal device.

Step 105: and the terminal equipment synchronizes the state of the PDU session according to the first PDU session state information. Illustratively, the terminal device indicates the first PDU session status information as inactive state and the terminal device maintains the state of the PDU session in the active state, changes the state from the active state to the inactive state, and releases the PDU session. Therefore, the terminal equipment can synchronize the state of the PDU session with the network in time, so that the state of the PDU session maintained by the terminal equipment side is consistent with the state of the PDU session maintained by the network side, the number of the PDU sessions (namely the successfully established PDU sessions) in the activated state of the terminal equipment side and the network side is further ensured to be consistent, and the management efficiency of the PDU session can be improved.

In the application, besides the PDU session state information element is carried by three flows of SERVICE REQUEST (SERVICE REQUEST), REGISTRATION (REGISTRATION) or NOTIFICATION (NOTIFICATION) specified by the protocol 3GPP24.501, innovatively providing that the PDU session state information element is carried in a downlink non-access stratum transmission message carrying #65 sent by a mobility management element to a terminal device, so that the terminal device does not need to synchronize the PDU session state until the next SERVICE REQUEST (SERVICE REQUEST), REGISTRATION (REGISTRATION) or NOTIFICATION (NOTIFICATION) flow occurs, by using the method of the application, the terminal device can timely find that the PDU session state is not synchronized with the PDU session state at the network side, and further timely synchronize the PDU session state according to the PDU session state information element, and after synchronizing the PDU session state, the PDU session can be efficiently managed, for example, after synchronizing the PDU session state, the terminal device can determine that the number of currently established PDU sessions substantially does not reach the maximum value supported by the network, a new PDU session setup procedure may be further initiated.

In the embodiment of the application, after the terminal device synchronizes the PDU session state according to the first PDU session state information sent by the core network element, the PDU session state information can be further sent to the core network element, so that the core network element and the terminal device perform PDU session state synchronization, and thus, the synchronization efficiency can be further improved.

In a first possible implementation manner, the terminal device sends PDU session status information to the network element of the core network when waiting for a next SERVICE REQUEST, REGISTRATION or NOTIFICATION (NOTIFICATION) flow. The method is a method in the prior art, and the detailed description is omitted.

In a second possible implementation manner, the terminal device sends a PDU session related message to the core network element, where the PDU session related message carries second PDU session status information, and the second PDU session status information is used to indicate the status of all PDU sessions of the terminal device. The second PDU session status information also refers to the PDU session status information element shown in fig. 5, where "second" is used only to distinguish from the "first" PDU session status information appearing above, without other meaning. In a possible example, when the core network element is a mobility management element, the PDU session related message may be a message carrying a PDU session establishment request message, a PDU session release request message, or a PDU session modification request message. In another possible example, when the core network element is a session management network element, the PDU session related message may be a PDU session establishment request message, a PDU session release request message, or a PDU session modification request message. Through the second implementation manner, in addition to the PDU session state information element carried by three flows of SERVICE REQUEST (SERVICE REQUEST), REGISTRATION (REGISTRATION) or NOTIFICATION (NOTIFICATION) specified by the protocol 3GPP24.501, the present application innovatively provides that PDU session state information is carried by a PDU session related message, so as to implement synchronization of the PDU session state between a core network element and a terminal device.

Based on the second possible implementation manner, in one possible example, after receiving the PDU session related message from the terminal device, the core network element performs corresponding processing according to the PDU session related message, and synchronizes the state of the PDU session maintained for the terminal device according to the second PDU session state information. For example, taking a core network element as a mobility management network element as an example, the mobility management network element may synchronize the state of the PDU session maintained for the terminal device according to the second PDU session state information by using the following method: and the mobility management network element indicates the second PDU session state information as an inactive state and maintains the PDU session state of the active state for the terminal equipment, and the active state is changed into the inactive state. Further, the mobility management network element may further send session release information to a session management network element that manages the PDU session that the second PDU session state information indicates as the inactive state and the mobility management network element maintains as the active state for the terminal device, where the session release information is used to instruct the session management network element to release the PDU session that the second PDU session state information indicates as the inactive state and the mobility management network element maintains as the active state for the terminal device. For another example, taking a core network element as a session management network element as an example, the session management network element may synchronize the state of the PDU session maintained for the terminal device according to the second PDU session state information by using the following method: the session management network element releases the PDU session which is indicated as the inactive state by the second PDU session state information and is maintained as the active state for the terminal equipment by the mobility management network element; further, after the session management network element releases the session, the session management network element may also send the second PDU session state information to the mobility management network element, so that the mobility management network element synchronizes the state of the PDU session with the terminal device according to the second PDU session state information.

It should be noted that, for different PDU session related messages, the core network element performs different processing according to the PDU session related messages. As described in detail below.

And when the PDU session related message is a PDU session establishment request message, the core network element establishes the PDU session according to the PDU session establishment request message.

And when the PDU session related message is a PDU session release request message, the core network element releases the PDU session according to the PDU session release request message.

And when the PDU session related message is a PDU session modification message, the core network element modifies the state of the PDU session according to the PDU session modification message.

The method of fig. 7 will be described below by way of example, applying the method of fig. 7 to the network architecture shown in fig. 1. Please refer to fig. 8, which is a schematic flowchart illustrating a further method for synchronizing a PDU session status provided in the present application, where fig. 8 illustrates a core network element as an AMF in fig. 1 and a terminal device as a UE in fig. 1, and the method may include the following processing flows.

Step 201: the UE sends a first request for requesting to establish a first PDU session to an AMF (advanced multimedia broadcast frame) for managing the PDU session of the UE, the number of the current active PDU sessions of the UE is 4, and the number of the current active PDU sessions of the UE is respectively PDU session a, PDU session b, PDU session c and PDU session e, wherein the UE also has inactive PDU session d and PDU session f. As shown in table 1, the status of all PDU sessions for the UE.

TABLE 1

PDU session for UE	Status of PDU sessions
		PDU session a	Active state
PDU session b	Active state
		PDU session c	Active state
PDU session d	Non-activated state
		PDU session e	Active state
PDU session f	Non-activated state

Step 202: assuming that the network can support a maximum number of PDU sessions established for the UE of 5, the AMF determines that the number of PDU sessions currently maintained for the UE in an active state (i.e., established PDU sessions) of 5 reaches the maximum number supported by the network in response to the first request, wherein the states of all PDU sessions maintained by the AMF for the UE are as shown in table 2.

TABLE 2

Step 203: the AMF sends a first response to the UE in response to the first request, where the first response includes PDU session status information 1 and a cause value #65, where the PDU session status information 1 is used to indicate the status of all PDU sessions maintained by the AMF for the UE, and based on the above example, the PDU session status information 1 is used to indicate that the status of the PDU session a maintained by the AMF for the UE is active, the status of the PDU session b is active, the status of the PDU session c is inactive, the status of the PDU session d is active, the status of the PDU session e is active, and the status of the PDU session f is active, and the cause value #65 is used to indicate that the number of established PDU sessions maintained for the UE has reached a maximum value (maximum number of PDU sessions accessed).

For example, the AMF may use an existing downlink non-access stratum transport message (DL NAS TRANPORT) carrying a cause value #65 to carry PDU session state information 1, in this example, only a new Information Element (IE) PDU session state information 1 needs to be added to the DL NAS TRANPORT message carrying the cause value #65, as shown in table 3, the last behavior in table 3 is an IE added as compared with the existing technology, for one possible format of the downlink non-access stratum transport message based on this example.

TABLE 3

Step 204: the UE determines the status of the PDU session maintained by the AMF to be inconsistent according to the PDU session status information 1 and the cause value # 65. According to the method of the prior art, after receiving the cause value #65, the UE considers that the number of currently established PDU sessions (i.e. PDU sessions in an active state) of the UE reaches the maximum value supported by the network, and with the method of the present application, the UE may determine that the currently established PDU sessions of the UE do not substantially reach the maximum value supported by the network according to the fact that the number 5 of currently established PDU sessions (i.e. PDU sessions in an active state) indicated by the PDU session state information 1 is greater than the number 4 of PDU sessions in an active state of the UE, and may determine that the status of the UE and the PDU sessions maintained by the AMF is inconsistent.

Step 205: and the UE synchronizes the state of the PDU session according to the PDU session state information 1. Continuing the above example, the UE indicates the PDU session status information 1 as inactive state and maintains the status of the PDU session c in active state, changes the active state into inactive state, and releases the PDU session c. As shown in table 4, the status of all PDU sessions of the synchronized UE.

TABLE 4

PDU session for synchronized UE	Status of PDU sessions
		PDU session a	Active state
PDU session b	Active state
		PDU session c	Non-activated state
PDU session d	Non-activated state
		PDU session e	Active state
PDU session f	Non-activated state

By adopting the method provided by the application, after the UE receives the message carrying the cause value #65 and the PDU session state information 1, the UE does not consider that the number of the currently established PDU sessions reaches the maximum value supported by the network like the prior art, and does not initiate a new session establishment flow.

In a possible implementation manner, after the UE synchronizes the PDU session state according to the PDU session state information 1 sent by the AMF, the PDU session state information 2 may be further sent to the AMF, where the PDU session state information 2 is used to indicate the state of all PDU sessions of the synchronized UE, so that the AMF further performs PDU session state synchronization with the UE, and thus, the synchronization efficiency may be further improved, see step 206-step 207. In step 206, the UE sends PDU session status information 2 through a PDU session setup request message as an example.

Step 206: the UE sends an uplink non-access stratum transmission message (UL NAS TRANSPORT) carrying a PDU session establishment request to the AMF, wherein the PDU session establishment request message is used for requesting the establishment of a PDU session g, and the uplink non-access stratum transmission message carries PDU session state information 2. Based on the above example, the PDU session status information 2 is used to indicate that the status of the PDU session a of the synchronized UE is active, the status of the PDU session b is active, the status of the PDU session c is inactive, the status of the PDU session d is inactive, the status of the PDU session e is active, and the status of the PDU session f is inactive.

In a possible implementation manner, the UE may also carry the PDU session state information 2 in the PDU session establishment request, in this implementation, since the AMF transparently transmits the session establishment request sent by the UE to the SMF, the AMF does not sense the PDU session state information 2 sent by the UE, and after the SMF receives the PDU session establishment request carrying the PDU session state information 2 sent by the UE, the PDU session state information 2 may be forwarded to the AMF, thereby synchronizing the state of the PDU session.

Step 207: and after receiving the uplink non-access stratum transmission message sent by the UE, the AMF synchronizes the state of the PDU session maintained for the UE according to the PDU session state information 2. Based on the above example, the AMF indicates the PDU session status information 2 as inactive state and maintains the status of the PDU session d and the PDU session f as active state for the UE, and changes from active state to inactive state. As shown in table 5, the status of all PDU sessions for the synchronized AMF. In addition, after the AMF synchronizes the PDU session state with the UE, it is determined that the number of the PDU sessions in the active state (i.e. the established PDU sessions) is 3 and does not reach the maximum value 5 supported by the network, and it is determined that a new PDU session can be established for the UE, and the PDU session establishment request is forwarded to the SMF to establish the PDU session g, it should be noted that the process of establishing the PDU session g may be described with reference to fig. 3, and details are not repeated in this example.

TABLE 5

PDU session maintained by synchronized AMF for UE	Status of PDU sessions
		PDU session a	Active state
PDU session b	Active state
		PDU session c	Non-activated state
PDU session d	Non-activated state
		PDU session e	Active state
PDU session f	Non-activated state

Step 208: the AMF can also send session release information to the SMF managing the PDU session d and the PDU session f, wherein the session release information is used for indicating the SMF to release the PDU session d and the PDU session f.

Step 209: and the SMF releases the PDU session d and the PDU session f according to the session release information.

In addition, aiming at the problem that the session states respectively maintained by the terminal equipment side and the network side in the prior art are possibly inconsistent and the session management efficiency is influenced, the application also provides two methods for synchronizing the session states maintained by the terminal equipment side and the network side.

In the first method, when the terminal device and the network interact with each other to manage the related messages, the terminal device may carry the PDU session status IE shown in fig. 5 in the UL NAS TRANSPORT message carrying the 5GSM message 1, and the mobility management network element may carry the PDU session status IE shown in fig. 5 in the DL NAS TRANSPORT message carrying the 5GSM message 2. Besides the PDU session state information element is carried by three flows of SERVICE REQUEST (SERVICE REQUEST), REGISTRATION (REGISTRATION) or NOTIFICATION (NOTIFICATION) specified by the protocol 3GPP24.501, the method innovatively proposes that PDU session status IE is carried in UL NAS TRANSPORT/DL NAS TRANSPORT message carrying 5GSM message, and the flow of synchronous PDU session is increased. The 5GSM message 1 may be a PDU session establishment request message, a PDU session release request message, a PDU session modification request message, and the like, and correspondingly, the 5GSM message 2 may be a PDU session establishment accept message, a PDU session establishment reject message, a PDU session release accept message, a PDU session modification accept message, or a PDU session modification reject message, and the like.

The following takes the network architecture shown in fig. 1 as an example to illustrate the first method. Please refer to fig. 9a, which is a schematic flowchart of another method for synchronizing PDU session status provided in the present application, wherein fig. 9a illustrates an example that 5GSM message 1 is a PDU session establishment request message, and 5GSM message 2 is a PDU session establishment accept message, but the method shown in fig. 9a is also applicable to other PDU session management flows, and the method may include the following process flows.

Step 301: the UE sends, to the AMF, a UL NAS TRANSPORT message carrying a PDU session establishment request message, where the UL NAS TRANSPORT message carries second PDU session status information, where the meaning of the second PDU session status information in this example is the same as the above meaning, and is not described here again. Illustratively, the UE may send a UL NAS TRANSPORT message to the AMF through r (an). As shown in table 6, which is a possible UL NAS TRANSPORT message format provided in the present application, the last row in table 6 is a new IE.

TABLE 6

Step 302: and the AMF synchronizes the PDU session state maintained by the AMF according to the second PDU session state information. Illustratively, the AMF modifies the status of the PDU session, which indicates the second PDU session status information as inactive and the AMF maintains the active status, to the inactive status according to the second PDU session status information.

Step 303: and the AMF sends session release information to the SMF managing the PDU session of which the second PDU session state information indicates the inactive state and the AMF maintains the active state, wherein the session release information is used for indicating the SMF to release the PDU session of which the second PDU session state information indicates the inactive state and the AMF maintains the active state.

Step 304: the SMF releases the PDU session indicated as inactive by the second PDU session state information and the AMF maintains the active PDU session.

Step 305: the AMF decapsulates the UL NAS TRANSPORT message to obtain a PDU session establishment request message, and it is worth noting that the PDU session establishment request message does not carry second PDU session state information, the second PDU session state information is carried in the outer-layer UL NAS TRANSPORT message, after the PDU session establishment request message is obtained, the AMF sends the PDU session establishment request message to the SMF, and correspondingly, the SMF receives the PDU session establishment request message from the AMF.

It should be noted that in this example, some steps irrelevant to the present application may be omitted between the various steps, and are not shown in fig. 9a for the omitted steps.

Step 306: the SMF sends a PDU session establishment acceptance message to the AMF, and correspondingly, the AMF receives the PDU session establishment acceptance message from the SMF.

Step 307: the AMF encapsulates the received PDU session establishment acceptance message to obtain a DL NAS TRANSPORT, and carries first PDU session state information in the DL NAS TRANSPORT, where the meaning of the first PDU session state information in this example is the same as that in the foregoing, and is not described herein again.

Step 308: and the AMF sends a DL NAS TRANSPORT message carrying the session state information of the first PDU to the UE. Illustratively, the AMF may be sent to the UE through r (an).

Step 309: and the UE synchronizes the state of the PDU session maintained by the UE according to the first PDU session state information.

The following takes the network architecture shown in fig. 1 as an example to illustrate the first method. Please refer to fig. 9b, which is a schematic flowchart illustrating a method for synchronizing PDU session status according to another embodiment of the present invention, where fig. 9b illustrates an example that a PDU session setup request message is a GSM message 5 1, and a PDU session setup accept message is a GSM message 5, the method may include the following process flows.

Step 401: the UE sends, to the AMF, a UL NAS TRANSPORT message carrying the PDU session establishment request message, where the UL NAS TRANSPORT message does not carry the second PDU session status information, where the meaning of the second PDU session status information in this example is the same as the meaning in the foregoing, and is not described here again. Illustratively, the UE may send a UL NAS TRANSPORT message to the AMF through r (an).

Step 402: and the AMF decapsulates the UL NAS TRANSPORT message to obtain a PDU session establishment request message, the AMF sends the PDU session establishment request message to the SMF, and correspondingly, the SMF receives the PDU session establishment request message from the AMF.

It should be noted that in this example, some steps irrelevant to the present application may be omitted between the various steps, and are not shown in fig. 9b for the omitted steps.

Step 403: the SMF sends a PDU session establishment acceptance message to the AMF, and correspondingly, the AMF receives the PDU session establishment acceptance message from the SMF.

Step 404: the AMF encapsulates the received PDU session establishment acceptance message to obtain a DL NAS TRANSPORT, and carries first PDU session state information in the DL NAS TRANSPORT, where the meaning of the first PDU session state information in this example is the same as that in the foregoing, and is not described herein again.

Steps 405 to 406 are the same as steps 308 to 309, and the repetition points can be referred to each other and are not described again.

In the second method, when the terminal device and the network interact with the session management related message, the terminal device may carry the PDU session status IE shown in fig. 5 in the 5GSM message 1, and correspondingly, the session management network element may carry the PDU session status IE shown in fig. 5 in the 5GSM message 2. Here, the meaning of the 5GSM message 1 and the 5GSM message 2 is the same as above, and is not described in detail. Besides the PDU session status information element is carried by three procedures of SERVICE REQUEST (SERVICE REQUEST), REGISTRATION (REGISTRATION) or NOTIFICATION (NOTIFICATION) specified by the protocol 3GPP24.501, the PDU session status IE is carried in the 5GSM message by the innovative proposal of the method, and the procedure of synchronizing the PDU session is increased.

The following takes the network architecture shown in fig. 1 as an example to illustrate the second method. Please refer to fig. 10a, which is a schematic flowchart of another method for synchronizing PDU session status provided in the present application, wherein fig. 10a illustrates an example that 5GSM message 1 is a PDU session establishment request message, and 5GSM message 2 is a PDU session establishment accept message, but the method shown in fig. 10a is also applicable to other PDU session management flows, and the method may include the following process flows.

Step 501: and the UE sends a PDU session establishment request message carrying the second PDU session state information to the AMF through the R (AN). Table 7 shows a schematic structural diagram of a possible PDU session establishment request message carrying second PDU session status information, where an information element second PDU session status information is newly added in the PDU session establishment request message, and it needs to be noted that when the GSM message 15 is other messages related to a PDU session, the structure is similar.

TABLE 7

Step 502: and after receiving the PDU session establishment request message carrying the second PDU session state information, the AMF forwards the PDU session establishment request message carrying the second PDU session state information to the SMF.

Step 503: after receiving the PDU session establishment request message carrying the second PDU session state information, the SMF sends a request message carrying the second PDU session state information to the AMF, wherein the request message is used for requesting the first PDU session state information.

Step 504: and the AMF synchronizes the PDU session state maintained by the AMF according to the second PDU session state information.

Step 505: and the AMF sends session release information to the SMF, wherein the session release information is used for indicating the SMF to release the PDU session of which the second PDU session state information indicates the inactive state and the AMF maintains the active state.

Step 506: and the SMF releases the PDU session which is indicated as the inactive state by the second PDU session state information and is maintained as the active state by the AMF according to the session release information.

It should be noted that in this example, some steps irrelevant to the present application may be omitted between the various steps, and are not shown in fig. 10a for the omitted steps.

Step 507: and the AMF sends a response message of the request message to the SMF, wherein the response message of the request message carries the session state information of the first PDU.

Step 508: the SMF sends a PDU session establishment receiving message carrying first PDU session state information to the UE through the AMF and the R (AN).

Step 601: and the UE sends a PDU session establishment request message which does not carry the session state information of the second PDU to the AMF through the R (AN).

Step 602: and after receiving the PDU session establishment request message, the AMF generates a PDU session establishment request message carrying first PDU session state information according to the PDU session establishment request message and the first PDU session state information. It can be understood that, when the AMF forwards the PDU session establishment request message to the SMF, the first PDU session status information is carried in the PDU session establishment request message.

Step 603: and the AMF sends a PDU session establishment request message carrying the session state information of the first PDU to the SMF.

It should be noted that in this example, some steps irrelevant to the present application may be omitted between the various steps, and are not shown in fig. 10b for the omitted steps.

Step 604: the SMF sends a PDU session establishment receiving message carrying first PDU session state information to the UE through the AMF and the R (AN).

Based on the same inventive concept, the embodiment of the present application further provides a terminal device, which may have a structure as shown in fig. 11 and has a behavior function of the terminal device in the foregoing method embodiment. As shown in fig. 11, the terminal device 1100 may include a processing module 1101 and a transceiver module 1102. In implementation, the terminal device 1100 may further have a storage module 1103, and the storage module 1103 may be coupled with the processing module 1101 for storing programs and instructions required by the processing module 1101 to execute functions.

Based on the method shown in fig. 7, the processing module 1101 in the terminal device 1100 shown in fig. 11 can be used for the terminal device 1100 to perform step 104 or step 105, and the transceiving module 1102 can be used for the terminal device 1100 to perform step 101 or step 103.

In one possible design, the processing module 1101 synchronizes the status of the PDU session according to the first PDU session status information as follows: and indicating the first PDU session state information as an inactive state and maintaining the state of the PDU session in an active state by the terminal equipment, changing the state from the active state to the inactive state, and releasing the PDU session.

In one possible design, the transceiver module 1102 is further configured to: after the processing module 1101 synchronizes the status of the PDU session according to the first PDU session status information, sending a PDU session related message to the core network element, where the PDU session related message includes second PDU session status information, and the second PDU session status information is used to indicate the status of all PDU sessions of the terminal device.

In one possible design, the PDU session related message is a message carrying a PDU session establishment request message, a PDU session release request message, or a PDU session modification request message, or the PDU session related message is a PDU session establishment request message, a PDU session release request message, or a PDU session modification request message.

In addition, the terminal device according to the embodiment of the present application may further have a structure of the terminal device 1200 shown in fig. 12, where the processor 1201 in the terminal device 1200 shown in fig. 12 may be configured to implement the function of the processing module 1101, for example, the processor 1201 may be configured to implement the terminal device 1200 to perform step 104 or step 105, and the transceiver 1202 may be configured to implement the function of the transceiver module 1102, for example, the transceiver 1202 may be configured to implement the terminal device 1200 to perform step 101 or step 103. Further, the transceiver 1202 may be coupled to an antenna 1203 for enabling the terminal device 1200 to communicate with core network elements. Illustratively, the terminal device 1200 may further include a memory 1204, in which computer programs and instructions are stored, and the memory 1204 may be coupled with the processor 1201 and/or the transceiver 1202, for supporting the processor 1201 to call the computer programs and instructions in the memory 1204 to implement the steps involved in the terminal device in the method provided by the embodiment of the present application; in addition, the memory 1204 may be further configured to store data related to embodiments of the method of the present application, for example, data, instructions necessary to support the transceiver 1202 to perform the interaction, and/or configuration information necessary for the terminal device 1200 to perform the method of the embodiments of the present application.

Based on the same inventive concept, an embodiment of the present application further provides a core network element, where the core network element may have a structure as shown in fig. 13 and has a behavior function of the core network element in the foregoing method embodiment. As shown in fig. 13, the core network element 1300 may include a processing module 1301 and a transceiver module 1302. In implementation, the core network element 1300 may further have a storage module 1303, and the storage module 1303 may be coupled to the processing module 1301 and used for storing programs and instructions required by the processing module 1301 for executing functions.

Based on the method shown in fig. 7, the processing module 1301 in the core network element 1300 shown in fig. 13 may be used by the core network element 1300 to perform step 102, and the transceiver module 1302 may be used by the core network element 1300 to perform step 101 or step 103.

In one possible design, the transceiver module 1302 is further configured to: receiving a PDU session related message from the terminal equipment, wherein the PDU session related message carries second PDU session state information, and the second PDU session state information is used for indicating the state of all PDU sessions of the terminal equipment;

the processing module 1301 is further configured to: and executing corresponding processing according to the PDU session related message, and synchronizing the state of the PDU session maintained for the terminal equipment according to the second PDU session state information.

In one possible design, the core network element 1300 is the mobility management element, and the PDU session related message is a message carrying a PDU session establishment request message, a PDU session release request message, or a PDU session modification message;

the processing module 1301 is specifically configured to: and indicating the second PDU session state information as an inactive state and maintaining the state of the PDU session in an active state for the terminal equipment by the mobility management network element, and changing the state from the active state to the inactive state.

In one possible design, the transceiver module 1302 is further configured to: and sending session release information to a session management network element which manages the PDU session state information indicating the inactive state and the mobility management network element maintaining the PDU session in the active state for the terminal device, wherein the session release information is used for indicating the session management network element to release the PDU session in which the PDU session state information indicating the inactive state and the mobility management network element maintaining the PDU session in the active state for the terminal device.

the processing module 1301 is specifically configured to: establishing a PDU session according to the PDU session establishment request message; alternatively, the first and second electrodes may be,

the processing module 1301 is specifically configured to: releasing the PDU session according to the PDU session release request message; alternatively, the first and second electrodes may be,

the processing module 1301 is specifically configured to: and modifying the state of the PDU session according to the PDU session modification message.

In addition, the core network element according to the embodiment of the present application may further have a structure of the core network element 1400 as shown in fig. 14, where the processor 1401 in the core network element 1400 as shown in fig. 14 may be configured to implement the function of the processing module 1101 described above, for example, the processor 1401 may be configured to implement the core network element 1400 to perform step 102, and the communication interface 1402 may be configured to implement the function of the transceiver module 1102 described above, for example, the communication interface 1402 may be configured to implement the core network element 1400 to perform step 101 or step 103. Illustratively, the core network element 1400 may further include a memory 1403, wherein a computer program and instructions are stored in the memory 1403, and the memory 1403 may be coupled to the processor 1401 and/or the communication interface 1402, for enabling the processor 1401 to call the computer program and instructions in the memory 1403 to implement the steps involved in the core network element in the method provided by the embodiment of the present application; in addition, the memory 1403 may be further configured to store data related to the embodiments of the method of the present application, for example, to store data, instructions necessary for supporting the communication interface 1402 to implement the interaction, and/or to store configuration information necessary for the core network element 1400 to execute the method of the embodiments of the present application. Optionally, the core network element 1400 may further include a bus 1404. Wherein the communication interface 1402, the processor 1401, and the memory 1403 can be connected to each other through a bus 1404; the bus 1404 may be a Peripheral Component Interconnect (PCI) bus, an Extended Industry Standard Architecture (EISA) bus, or the like. The bus 1404 may be divided into an address bus, a data bus, a control bus, and the like. For ease of illustration, only one thick line is shown in FIG. 14, but this is not intended to represent only one bus or type of bus.

Based on the same concept as the method embodiment, the embodiment of the present application further provides a computer-readable storage medium, on which some instructions are stored, and when the instructions are called by a computer and executed, the instructions may cause the computer to perform the method involved in any one of the possible designs of the method embodiment and the method embodiment. In the embodiment of the present application, the computer-readable storage medium is not limited, and may be, for example, a RAM (random-access memory), a ROM (read-only memory), and the like.

Based on the same concept as the above method embodiments, the present application also provides a computer program product, which when called by a computer can perform the method as referred to in the method embodiments and any possible design of the above method embodiments.

Based on the same concept as the method embodiments described above, the present application also provides a chip, which is coupled to a transceiver, for performing the method as referred to in any one of the possible implementations of the method embodiments described above, wherein "coupled" means that two components are directly or indirectly joined to each other, which may be fixed or movable, which may allow flowing liquid, electrical signals or other types of signals to be communicated between the two components.

In the above embodiments, the implementation may be wholly or partially realized by software, hardware, firmware, or any combination thereof. When implemented in software, may be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When loaded and executed on a computer, cause the processes or functions described in accordance with the embodiments of the invention to occur, in whole or in part. The computer may be a general purpose computer, a special purpose computer, a network of computers, 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, for example, from one website site, computer, server, or data center to another website site, computer, server, or data center via wired (e.g., coaxial cable, fiber optic, Digital Subscriber Line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium that can be accessed by a computer or a data storage device, such as a server, a data center, etc., that incorporates one or more of the available media. The usable medium may be a magnetic medium (e.g., floppy Disk, hard Disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., Solid State Disk (SSD)), among others.

The various illustrative logical units and circuits described in this application may be implemented or operated upon by design of a general purpose processor, a digital signal processor, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof. A general-purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a digital signal processor and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a digital signal processor core, or any other similar configuration.

The steps of a method or algorithm described in the embodiments herein may be embodied directly in hardware, in a software element executed by a processor, or in a combination of the two. The software cells may be stored in RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. For example, a storage medium may be coupled to the processor such the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium may reside in an ASIC, which may be disposed in a terminal device. In the alternative, the processor and the storage medium may reside as discrete components in a terminal device.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

While the invention has been described in conjunction with specific features and embodiments thereof, it will be evident that various modifications and combinations can be made thereto without departing from the spirit and scope of the invention. Accordingly, the specification and figures are merely exemplary of the invention as defined in the appended claims and are intended to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.

Claims

1. A method for synchronizing PDU session status, comprising:

the method comprises the steps that terminal equipment sends a first request for requesting to establish a first PDU session to a core network element managing a Protocol Data Unit (PDU) session of the terminal equipment, wherein the number of the PDU sessions of the terminal equipment in an activated state is N, and N is an integer greater than or equal to 1;

the terminal device receives a first response from the core network element in response to the first request, where the first response includes first PDU session state information and maximum value indication information, the first PDU session state information is used to indicate states of all PDU sessions maintained by a mobility management element for the terminal device, the maximum value indication information is used to indicate that the number of established PDU sessions maintained for the terminal device has reached a maximum value, the number of PDU sessions in an active state included in all PDU sessions is M, and M is an integer greater than N;

and the terminal equipment synchronizes the state of the PDU session according to the first PDU session state information.

2. The method of claim 1, wherein synchronizing the status of the PDU sessions by the terminal device based on the first PDU session status information comprises:

and the terminal equipment indicates the first PDU session state information as an inactive state and maintains the state of the PDU session in the active state, the state of the PDU session is changed from the active state to the inactive state, and the PDU session is released.

3. The method of claim 1 or 2, wherein after synchronizing the status of the PDU sessions by the terminal device according to the first PDU session status information, further comprising:

and the terminal equipment sends a PDU session related message to the network element of the core network, wherein the PDU session related message comprises second PDU session state information, and the second PDU session state information is used for indicating the states of all PDU sessions of the terminal equipment.

4. The method of claim 3, wherein the PDU session related message is a message carrying a PDU session establishment request message, a PDU session release request message, or a PDU session modification request message, or wherein the PDU session related message is a PDU session establishment request message, a PDU session release request message, or a PDU session modification request message.

5. A method for synchronizing PDU session status, comprising:

a core network element receives a first request for requesting to establish a first Protocol Data Unit (PDU) session from a terminal device;

the core network element responds to the first request and determines that the number of the PDU sessions in the activated state maintained for the terminal equipment reaches the maximum value;

the core network element sends a first response responding to the first request to the terminal equipment, wherein the first response comprises first PDU session state information and maximum value indication information, the first PDU session state information is used for indicating the state of all PDU sessions maintained by the mobility management element for the terminal equipment, and the maximum value indication information is used for indicating that the number of the established PDU sessions maintained for the terminal equipment reaches the maximum value.

6. The method of claim 5, wherein after the core network element sends a first response to the terminal device in response to the first request, further comprising:

the core network element receives a PDU session related message from the terminal equipment, wherein the PDU session related message carries second PDU session state information, and the second PDU session state information is used for indicating the state of all PDU sessions of the terminal equipment;

and the core network element executes corresponding processing according to the PDU session related message and synchronizes the state of the PDU session maintained for the terminal equipment according to the second PDU session state information.

7. The method of claim 6, wherein the core network element is the mobility management element, and the PDU session related message is a message carrying a PDU session establishment request message, a PDU session release request message, or a PDU session modification message;

the synchronizing, by the core network element according to the second PDU session status information, a status of the PDU session maintained by the terminal device includes:

and the mobility management network element indicates the second PDU session state information as an inactive state and maintains the PDU session state of the active state for the terminal equipment, and the active state is changed into the inactive state.

8. The method of claim 7, further comprising:

the mobility management network element sends session release information to a session management network element that manages the PDU session in which the second PDU session state information indicates the inactive state and the mobility management network element maintains the PDU session in the active state for the terminal device, where the session release information is used to indicate the session management network element to release the PDU session in which the second PDU session state information indicates the inactive state and the mobility management network element maintains the active state for the terminal device.

9. The method according to claim 5 or 6, wherein the PDU session related message is a PDU session establishment request message;

the core network element executes corresponding processing according to the PDU session related message, including:

the core network element establishes a PDU session according to the PDU session establishment request message;

alternatively, the first and second electrodes may be,

the core network element releases the PDU session according to the PDU session release request message;

alternatively, the first and second electrodes may be,

10. A chip is applied to terminal equipment and is characterized by comprising a baseband processor;

the baseband processor is configured to send a first request for requesting establishment of a first PDU session to a core network element managing a PDU session of a protocol data unit of the terminal device, where the number of PDU sessions in an active state of the terminal device is N, where N is an integer greater than or equal to 1, receive a first response from the core network element in response to the first request, where the first response includes first PDU session state information and maximum value indication information, the first PDU session state information is used to indicate a state of all PDU sessions maintained by a mobility management element for the terminal device, the maximum value indication information is used to indicate that the number of established PDU sessions maintained for the terminal device has reached a maximum value, the number of PDU sessions in an active state included in all PDU sessions is M, and M is an integer greater than N, and synchronizing the state of the PDU session according to the first PDU session state information.

11. The chip according to claim 10, wherein the baseband processor, when synchronizing the status of the PDU session according to the first PDU session status information, is specifically configured to: and indicating the first PDU session state information as an inactive state and maintaining the state of the PDU session in an active state by the terminal equipment, changing the state from the active state to the inactive state, and releasing the PDU session.

12. The chip of claim 10 or 11, wherein the baseband processor is further to:

after synchronizing the state of the PDU session according to the first PDU session state information, sending a PDU session related message to the core network element, wherein the PDU session related message comprises second PDU session state information, and the second PDU session state information is used for indicating the state of all PDU sessions of the terminal equipment.

13. The chip of claim 12, wherein the PDU session related message is a message carrying a PDU session setup request message, a PDU session release request message, or a PDU session modification request message, or wherein the PDU session related message is a PDU session setup request message, a PDU session release request message, or a PDU session modification request message.

14. A system comprising a terminal device and a core network element;

the terminal equipment sends a first request for requesting to establish a first Protocol Data Unit (PDU) session to the core network element, wherein the number of the PDU sessions of the terminal equipment in an activated state is N, and N is an integer greater than or equal to 1;

the core network element responds to the first request, and determines that the number M of the PDU sessions which are maintained for the terminal equipment and are in the activated state reaches the maximum value, wherein M is an integer larger than N;

the core network element sends a first response responding to the first request to the terminal equipment, wherein the first response comprises first PDU session state information and maximum value indication information, the first PDU session state information is used for indicating the state of all PDU sessions maintained by a mobility management element for the terminal equipment, and the maximum value indication information is used for indicating that the number of the established PDU sessions maintained for the terminal equipment reaches the maximum value;

15. The system of claim 14, wherein the terminal device synchronizing the status of PDU sessions according to the first PDU session status information, comprises:

16. The system according to claim 14 or 15, wherein after synchronizing the status of the PDU session according to the first PDU session status information, the terminal device further comprises:

the terminal equipment sends a PDU session related message to the core network element, wherein the PDU session related message carries second PDU session state information which is used for indicating the state of all PDU sessions of the terminal equipment;

17. The system of claim 16, wherein the core network element is the mobility management element;

18. The system of claim 17, further comprising:

19. The system according to claim 17 or 18, wherein said PDU session related message is a message carrying a PDU session setup request message, a PDU session release request message or a PDU session modify message.

20. The system according to any of claims 14 to 16, wherein said PDU session related message is a PDU session setup request message;

alternatively, the first and second electrodes may be,