CN108810988B

CN108810988B - Message transmission method and device

Info

Publication number: CN108810988B
Application number: CN201810289567.3A
Authority: CN
Inventors: 朱奋勤; 吴问付
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2017-05-03
Filing date: 2018-04-03
Publication date: 2020-12-01
Anticipated expiration: 2038-04-03
Also published as: CN108810988A

Abstract

The application discloses a method and a device for message transmission, relates to the technical field of communication, and can solve the problem of unbalanced load among equipment serving for UE. The method of the present application comprises: the session management function device receives a deletion instruction from the first device and instruction information of a group to which the first device belongs, deletes second interface information in a UE session context according to the deletion instruction when the session management function device receives a first interface release message from the first device, and then sends a downlink message to the second device when the downlink message needs to be sent, wherein the second device is a device which is determined according to the instruction information of the group and is used for serving the UE. The method and the device are suitable for the message transmission process.

Description

Message transmission method and device

The present application claims priority of chinese patent application entitled "a method and apparatus for message transmission" filed by the chinese patent office on 03.05/2017, application number 201710305752.2, which is incorporated herein by reference in its entirety.

Technical Field

The present application relates to the field of communications technologies, and in particular, to a method and an apparatus for transmitting a message.

Background

In the fourth Generation mobile communication technology (4G), a Serving GateWay (SGW) may store a session context of a User Equipment (UE), where the session context of the UE includes an IP address of a Mobility Management Entity (MME) Serving the UE, and when the SGW needs to send a downlink message related to the UE to the MME, the SGW may obtain the IP address of the MME Serving the UE from the stored session context of the UE, and then send the downlink message related to the UE to the MME according to the obtained IP address.

If this method is also used in the Session Management Function (SMF) of the fifth-Generation mobile communication technology (5th-Generation mobile communication, 5G), that is, the SMF stores the UE Session context, and the UE Session context includes the external interface information of the processing unit (or the AMF instance) in the Access and Mobility Management Function (AMF) serving the UE, when the SMF needs to send the downlink message related to the UE, the external interface information of the processing unit (or the AMF instance serving the UE) in the AMF serving the UE last time (or the AMF instance serving the UE) is obtained according to the UE Session context, and the downlink message related to the UE is sent to the processing unit (or the AMF instance serving the UE) in the AMF serving the UE last time according to the obtained external interface information.

However, with this method, each time the SMF needs to send a downlink message related to the UE, the SMF sends the downlink message to the processing unit in the AMF that served the UE last time (or the AMF instance serving the UE), so that the UE is always served by the same processing unit or AMF instance, and a phenomenon of load imbalance may occur.

Disclosure of Invention

The embodiment of the application provides a message transmission method and device, which can solve the problem of load imbalance caused by the fact that session management function equipment sends a downlink message related to UE to first equipment serving the UE last time.

In order to achieve the purpose, the technical scheme is as follows:

in a first aspect, the present application provides a method for message transmission, including:

the method comprises the steps that a session management function device receives a deletion instruction from a first device and instruction information of a group to which the first device belongs, under the condition that the session management function device receives a first interface release message from the first device, the session management function device deletes second interface information in a UE session context according to the deletion instruction, then when the session management function device needs to send a downlink message, the session management function device sends the downlink message to a second device, and the second device is a device which is determined according to the instruction information of the group and is used for serving the UE.

The deletion instruction is used to instruct the session management function device to delete second interface information in a session context of the user equipment UE when receiving a first interface release message, where the first interface is an interface between the radio access network RAN and the first device, and the second interface is an interface between the first device and the session management function device.

The session management function device may be an AMF device, and the first device and the second device may each be one instance of an AMF group, or the first device and the second device may each be one processing unit of the AMF device.

Compared with the prior art, the session management function device deletes the second interface information in the UE session context under the condition that the first interface of the first device is released, and then when the session management function device needs to send the downlink message, the session management function device cannot search the interface information of the first device serving the UE last time from the UE context, and can trigger the process of reselecting the second device serving the UE.

In a possible design, the session management function device receives the deletion instruction from the first device and the instruction information of the group to which the first device belongs, and may specifically be implemented as: the session management function device receives a session establishment request from the first device, wherein the session establishment request includes group indication information, a deletion indication and second interface information.

After the session management function device receives the session establishment request from the first device, the session management function device may store the indication information, the deletion indication, and the second interface information of the group in the UE session context.

The second interface information is stored in the UE session context, and before the UE is not switched to the idle state, the session management function device can directly communicate with the first device serving the UE according to the second interface information without frequently reselecting the device serving the UE, so that the service quality of the UE in the connection state can be improved. The deletion indication is stored in the UE session context, and the session management function device can delete the second interface information in the UE session context in time when receiving the release message of the first interface, so that the UE is prevented from being served by the same device every time the UE enters a connection state, and the problem of load imbalance in the prior art is solved.

In a possible design, the session management function device deletes the second interface information in the UE session context according to the deletion instruction, which may be specifically implemented as: and the session management function equipment deletes the second interface information in the UE session context according to the deletion indication in the UE session context.

In a possible design, the session management function device receives the deletion instruction from the first device and the instruction information of the group to which the first device belongs, and may specifically be implemented as: the session management function device receives a session establishment request from the first device, where the session establishment request includes the indication information of the group and the second interface information, and then receives a first interface release message from the first device, where the first interface release message includes a deletion indication.

After the session management function device receives the session establishment request from the first device, the session management function device may save the indication information of the group and the second interface information in the UE session context.

The second interface information is stored in the UE session context, and before the UE is not switched to the idle state, the session management function device can directly communicate with the first device serving the UE according to the second interface information without frequently reselecting the device serving the UE, so that the service quality of the UE in the connection state can be improved.

In a possible design, the session management function device receives the deletion instruction from the first device and the instruction information of the group to which the first device belongs, and may specifically be implemented as: and the session management function device receives a first interface release message from the first device, wherein the first interface release message comprises the indication information of the group and the deletion indication.

Before the session management function device receives the first interface release message from the first device, the session management function device receives a session establishment request from the first device, the session establishment request includes the second interface information, and then the session management function device stores the second interface information in the UE session context.

The first interface release message carries the deletion instruction, so that the session management function device can delete the second interface information in the UE session context in time under the condition of receiving the first interface release message, thereby avoiding that the UE is served by the same device when entering a connection state every time, and solving the problem of unbalanced load in the prior art.

In a possible design, the session management function device deletes the second interface information in the UE session context according to the deletion instruction, which may be specifically implemented as: and the session management function equipment deletes the second interface information in the session context of the UE according to the deletion instruction included in the first interface release message.

In one possible design, the indication information of the group is a group identity ID of the group; the session management function device may determine, according to the group ID, a second device serving the UE, and then send a downlink message to the second device through an interface between the session management function device and the second device.

In one possible design, the indication of the group is a default route of the group; when the session management function device needs to send a downlink message, the session management function device sends the downlink message to a device corresponding to the default route of the group, then receives a second device identifier from the device corresponding to the default route of the group, the second device is a device selected by the UE and corresponding to the default route of the group, and then the session management function device sends the downlink message to the second device corresponding to the second device identifier through an interface between the session management function device and the second device.

In one possible design, the indication of the group is a default route of the group; when the session management function device needs to send the downlink message, the session management function device sends the downlink message to the second device through the device corresponding to the default route of the group, and the second device is the second device selected by the UE and corresponding to the default route of the group.

In a possible design, after the session management function device sends a downlink message to the second device through the device corresponding to the default route of the group, and after the session management function device receives the message from the second device, the session management function device stores interface information between the session management function device and the second device in the UE session context.

By storing the interface information between the session management function device and the second device in the session context of the UE, the session management function device does not need to reselect the device serving the UE each time when sending the downlink message of the UE before the UE switches to the idle state, which can save the overhead and avoid the interruption of the UE service due to reselecting the device serving the UE.

In a second aspect, the present application provides a method for message transmission, including:

the session management function device obtains stateless indication information and group indication information of a group to which the first device belongs, the stateless indication information is used for indicating that the session management function device selects second equipment for serving the UE according to the group indication information when downlink information needs to be sent after the session management function device determines that the signaling connection corresponding to the user equipment UE is bound and released with the first interface, and then, the session management function device sends the downlink information to the second equipment when the session management function device needs to send the downlink information under the condition that the session management function device receives a release notification from the first device. The first device is a device serving the UE before the binding between the signaling connection and the first interface is released, the first interface is an interface between the radio access network RAN and the first device, and the second device is a device serving the UE determined according to the group indication information. The release notification is used to indicate that the binding of the signaling connection to the first interface has been released.

The session management function device may be an AMF device, and the first device and the second device may each be one instance of an AMF group, or the first device and the second device may each be one processing unit of the AMF device. The group indication information of the group to which the first device belongs may be an AMF group ID or a default route of the AMF group.

The binding release of the signaling connection and the first interface includes but is not limited to the following two cases:

the first method comprises the following steps: and releasing the signaling connection corresponding to the UE, and releasing the binding of the signaling connection and the first interface.

And the second method comprises the following steps: and releasing the binding of the signaling connection and the first interface, wherein the signaling connection corresponding to the UE is not released.

Compared with the prior art, the session management function device can send the downlink message to the second device which is reselected to serve the UE under the condition that the binding between the signaling connection corresponding to the UE and the first interface is determined to be released and the downlink message needs to be sent, so that the phenomenon of load imbalance caused by the fact that the same device always serves the UE is avoided.

In one possible design, before the session management function device sends the downlink message to the second device, the session management function device may determine that the signaling connection corresponding to the UE is released from binding with the first interface.

In a possible design, if the session management function module needs to send a downlink message and determines that the binding between the signaling connection corresponding to the UE and the first interface is released, the second device for serving the UE is determined according to the group indication information.

By adopting the method, under the condition that the session management function equipment determines the binding release of the signaling connection of the UE and the first interface, the second equipment serving the UE is determined, so that the situation that the first equipment always provides service for the terminal can be avoided, and when the subsequent session management function equipment needs to send downlink messages, the downlink messages can be sent to the terminal through the second equipment.

In a possible design, the obtaining, by the session management function device, the group indication information of the group to which the first device belongs may be specifically implemented as:

the session management function equipment receives a session establishment request from the first equipment, wherein the session establishment request comprises group indication information; or, the session management function device receives a release notification from the first device, where the release notification includes the group indication information.

In one possible design, the session management function device obtains the stateless indication information, and includes:

the session management function equipment receives a session establishment request from the first equipment, wherein the session establishment request comprises stateless indication information; or, the session management function device receives a release notification from the first device, wherein the release notification includes the stateless indication information; or, the session management function device obtains the stateless indication information from the local configuration information.

In another possible design, a deletion indication is included in the release notification. Wherein the deletion instruction is information for instructing the session management function device to delete the first device.

By adopting the method, the session management function equipment deletes the information of the first equipment in the UE session context under the condition that the binding between the signaling connection corresponding to the UE and the first interface is released, then when the session management function equipment needs to send the downlink message, the session management function equipment cannot search the information of the first equipment serving the UE last time from the UE context, and further can trigger the process of reselecting the second equipment serving the UE, and the session management function equipment can send the downlink message to the second equipment, thereby avoiding the phenomenon of load imbalance caused by always providing the service for the UE by the same equipment.

In one possible design, after the session management function device receives the release notification from the first device, the session management function device deletes information of the first device in the UE session context according to the stateless indication information.

In another possible design, after the session management function device receives the release notification from the first device, the session management function device stores the release state of the binding between the signaling connection and the first interface, and then when the session management function device needs to send a downlink message, the session management function determines that the binding between the signaling connection and the first interface is released according to the release state of the binding between the signaling connection and the first interface, and then determines the second device for serving the UE according to the group indication information.

By adopting the method, after the binding between the signaling connection and the first interface is released, the session management function equipment can store the release state of the binding between the signaling connection and the first interface, and further, if the session management function equipment needs to send downlink messages, the second equipment for serving the UE is determined, so that the load imbalance caused by the fact that the first equipment is always used for providing services for the UE is avoided, and if the session management function does not need to send downlink messages subsequently, the second equipment for serving the UE does not need to be determined, so that the system overhead can be saved.

In another possible design, the group indication information is a group identity ID of a group to which the first device belongs; correspondingly, the session management function device sends the downlink message to the second device, which may specifically be implemented as: and if the session management function equipment needs to send the downlink message and the binding between the signaling connection corresponding to the UE and the first interface is released, determining second equipment serving the UE according to the group ID.

In a third aspect, the present application provides a message transmission apparatus, where the apparatus may implement a function executed by the session management function device in the first aspect or the second aspect, where the function may be implemented by hardware, or may be implemented by hardware executing corresponding software. The hardware or software comprises one or more modules corresponding to the functions.

In one possible design, the apparatus includes a processor and a communication interface, and the processor is configured to support the apparatus to perform the corresponding functions of the method. The communication interface is used to support communication between the apparatus and other network elements. The apparatus may also include a memory, coupled to the processor, that retains program instructions and data necessary for the apparatus.

In a fourth aspect, the present application provides a message transmission system, where the system includes the session management function device of the first aspect or the second aspect, a UE, a RAN, and a group to which the first device belongs.

In a fifth aspect, the present application provides a computer storage medium for storing computer software instructions for the session management function apparatus, which includes a program designed to execute the above aspects.

In a sixth aspect, the present application provides a computer program product, such as a computer readable storage medium, comprising a program for performing the method of the above aspect.

Drawings

Fig. 1 is a schematic structural diagram of a communication system provided in the present application;

fig. 2 is a schematic structural diagram of another communication system provided in the present application;

FIG. 3 is a schematic diagram of an AMF apparatus provided herein;

FIG. 4 is a schematic diagram of another AMF device provided herein;

fig. 5 is a schematic structural diagram of an SMF device provided in the present application;

FIG. 6 is a flow chart of a method of message transmission provided herein;

FIG. 7 is a flow chart of another method of message transmission provided herein;

FIG. 8 is a flow chart of another method of message transmission provided herein;

fig. 9 is a schematic structural diagram of a message transmission apparatus provided in the present application;

FIG. 10 is a flow chart of another method of message transmission provided herein;

fig. 11 is a schematic structural diagram of another message transmission apparatus provided in the present application.

Detailed Description

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

It is noted that, in the present application, words such as "exemplary" or "for example" are used to mean exemplary, illustrative, or descriptive. Any embodiment or design described herein as "exemplary" or "e.g.," is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word "exemplary" or "such as" is intended to present concepts related in a concrete fashion.

It should be noted that "of, corresponding to" and "corresponding" may be sometimes used in combination in the present application, and it should be noted that the intended meaning is consistent when the difference is not emphasized.

Before describing the technical solutions of the present application in detail, for convenience of understanding, a description is first given of a scenario in which the embodiments of the present application are applied.

The embodiment of the present application is applied to a communication system as shown in fig. 1, which includes a session management function device 101, an access and mobility management function device 102, and an access network device 103.

The access and mobility management function device 102 may further include an ASF unit, where the ASF unit is a network function, specifically, may be a default AMF instance shown in fig. 3, or may also be a dedicated network function, for example, may be a load balancer.

The session management function device 101 is configured to receive a deletion instruction from a first device and instruction information of a group to which the first device belongs, where the first device is a device currently serving as a UE in the access and mobility management function device 102, and the group to which the first device belongs is the access and mobility management function device 102.

A first device in the access and mobility management function device 102 is configured to send a first interface release message to the session management function device 101, where the first interface is an interface between the access network device 103 and the first device.

The session management function device 101 is further configured to delete, according to the deletion instruction, second interface information in the UE session context when the first interface release message from the first device is received, where the second interface is an interface between the first device and the session management function device 101. Then, when the session management function device 101 needs to send a downlink message, the downlink message may be sent to a second device, where the second device is a device serving the UE determined according to the group indication information.

It should be noted that the UE referred to in this application may include various handheld devices, vehicle-mounted devices, wearable devices, computing devices or other processing devices connected to a wireless modem, and various types of terminals, Mobile Stations (MS), User Equipment (User Equipment, UE), Terminal devices (Terminal Equipment), soft terminals, and so on. For convenience of description, the above-mentioned devices are collectively referred to as a UE in this application.

In addition, the present application is applicable to a 5G Network, and when the present application is applied to a 5G Network, AN architecture diagram of a communication system is shown in fig. 2, where the system includes AN Authentication Server Function (AUSF) device, a Unified Data Management (UDM) device, AN AMF device, AN SMF device, a Policy Control Function (PCF) device, a UE, a Radio Access Network (RAN) or Access Network (AN), a User Plane Function (UPF) device, and a Data Network (DN) device.

Among them, the session management function device 101 in fig. 1 may be implemented as the SMF device in fig. 2, the access and mobility management function device 102 in fig. 1 may be implemented as the AMF device in fig. 2, and the access network device 103 in fig. 1 may be implemented as the RAN or AN in fig. 2. In the following, the session management function device 101 is taken as an SMF device, the access and mobility management function device 102 is taken as an AMF device, and the access network device 103 is taken as an RAN.

The AMF device may serve the UE, authorize Access of the UE, and manage mobility of the UE, and meanwhile, the AMF device is further configured to transfer a Non Access Stratum (NAS) message between the UE and the SMF, and the like. The RAN can communicate with the UE and the AMF device, e.g., the RAN can forward a NAS message sent by the UE to the AMF device after receiving the NAS message. The SMF device may communicate with the AMF device, for example, may send a downlink message to the AMF device, etc. The SMF device is further configured to manage a session, for example, the SMF device may maintain interface information between the AMF device and the SMF device in a session context of the UE, so that when the SMF device receives a downlink message for a certain UE, the SMF device may determine, according to the interface information stored in the session context of the UE, the AMF device serving the UE.

In fig. 2, serial numbers marked on connection lines between the devices are used to distinguish interfaces between different devices, and fig. 2 is only an exemplary schematic diagram, and the application does not limit the serial numbers of the interfaces between the devices. Illustratively, in fig. 2, the UE communicates with the AMF through an N1 interface, the RAN communicates with the AMF through an N2 interface, and communicates with the UPFs through an N3 interface, the UPFs communicate with each other through an N9 interface, and the UPFs are interconnected with the DN through an N6 interface. The SMF controls the SMF through an N4 interface, the AMF communicates with the SMF through an N11 interface, the AMF and the SMF acquire user subscription data from the UDM through an N8 interface and an N10 interface respectively, and acquire policy data from the PCF through an N15 interface and an N7 interface respectively. In addition, the AMF devices communicate with each other through an N14 interface, the AUSF communicates with the AMF through an N12 interface, and communicates with the UDM through an N13 interface.

It should be noted that fig. 1 and fig. 2 are only schematic structural diagrams of a communication system applied in the present application, and in an actual deployment process, the number of devices in the communication system is not limited to the number of devices shown in fig. 1 and fig. 2. In addition, each device in fig. 1 to fig. 2 may be implemented by one entity device, may also be implemented by multiple entity devices together, and may also be a logic function module in one entity device, which is not specifically limited in this embodiment of the present application.

It should be further noted that the UE, RAN, AMF device, SMF device, AUSF device, UDM device, etc. in the above 5G network are only names, and the names do not limit the devices themselves. In the 5G network and other future networks, network elements or entities corresponding to the UE, the RAN, the AMF device, the SMF device, the AUSF device, and the UDM device may also be other names, which is not specifically limited in this embodiment of the present application. For example, the UDM device may be replaced by a Home Subscriber Server (HSS) or a User Subscription Database (USD) or a Database entity, and the like, which will not be described herein in detail.

It should be noted that the AMF device in fig. 2 may have two implementations, the first implementation is shown in fig. 3, and fig. 3 shows one AMF device, where the AMF device includes a Database (Database, DB), at least one Load Balancing (LB) unit, and at least two processing units. The LB unit is used for selecting a processing unit for the UE and distributing the received NAS message to the corresponding processing unit, the processing unit is used for processing the received NAS message and other messages, and the plurality of processing units can share data in the database.

Specifically, each LB unit and the processing unit have external interfaces, and when the RAN device is initialized, the external interfaces of the LB units in the AMF device are configured in the RAN device as the external interfaces of the AMF device, and when the RAN device receives an NAS message sent by the UE in an idle state, the RAN device first selects one AMF device, then selects one from the LB unit interfaces configured in the RAN device by the AMF device, and then sends the NAS message to the LB unit in the AMF device through the selected LB unit interface, and after receiving the NAS message, the LB unit allocates one processing unit to the NAS message. When the UE is in the connected state, the RAN device may directly communicate with the processing unit without forwarding data through the LB unit.

The AMF device in fig. 2 may also be implemented in a group, as shown in fig. 4, where the AMF group includes a database, at least one LB unit, and at least two AMF instances. The LB unit is used for selecting the AMF instance for the UE and distributing the received NAS message to the corresponding AMF instance, the AMF instance is used for processing the received NAS message and other messages, and the AMF instances can share data in the data.

Specifically, each LB unit and AMF instance have an external interface, and when the RAN device is initialized, the external interface of the LB unit is configured in the RAN device as an external interface of an AMF group, and when the RAN device receives an NAS message sent by a UE in an idle state, the RAN device selects one AMF group, selects one LB unit interface of the AMF group, and sends the NAS message to an LB unit in the AMF group through the LB unit interface, and after receiving the NAS message, the LB unit allocates one AMF instance to the NAS message. When the UE is in the connected state, the RAN device may communicate directly with the AMF instance without forwarding data through the LB unit.

In the prior art, after the LB unit selects a processing unit or an AMF instance for the UE, the SMF device stores external interface information of the processing unit or the AMF instance serving the UE when the session is established or activated in a session context of the UE, and when the SMF device needs to send a downlink message, the SMF device always sends the downlink message to the processing unit or the AMF instance serving the UE according to the external interface information of the processing unit or the AMF instance serving the UE last time, which is stored in the session context of the UE. Therefore, even if the UE switches from the idle state to the connected state, the process of reselecting the processing unit or the AMF instance is not triggered, and after the processing unit or the AMF instance serving the UE is saved in the UE session context of the SMF device, the UE is always served by the same processing unit or the AMF instance, even if the load of the AMF instance serving the UE last time is large and the loads of other AMF instances in the AMF group are small, the AMF still sends the downlink message to the AMF instance serving the UE last time, so that the phenomenon of load imbalance easily occurs.

In order to avoid the phenomenon of load imbalance, the principle of the application is as follows: when the AMF device in fig. 2 is implemented as fig. 3, the processing unit in the AMF device carries the deletion instruction and the SMF identifier in the session establishment request or the N2 release message sent to the SMF device, and further, when the SMF device receives the N2 release message, the SMF device can delete the interface information between the processing unit in the UE session context and the SMF device according to the deletion instruction, so that when the SMF device needs to send a downlink message, since there is no interface information between the processing unit and the SMF device in the UE session context, the SMF device can only send the downlink message to the processing unit reselected according to the AMF identifier, thereby avoiding the problem of load imbalance caused by sending the downlink message to the same processing unit each time.

Similarly, when the AMF in fig. 2 is implemented as fig. 4, the AMF instance in the AMF group carries the deletion instruction and the AMF group identifier in the session establishment request or the N2 release message sent to the SMF device, and further, when the SMF device receives the N2 release message, the SMF device can delete the interface information between the AMF instance and the SMF device in the UE session context according to the deletion instruction, so that when the SMF device needs to send the downlink message, because there is no interface information between the AMF instance and the SMF device in the UE session context, the SMF device can only send the downlink message to the reselected AMF instance according to the AMF group identifier, thereby avoiding the problem of load imbalance caused by sending the downlink message to the same AMF instance each time.

In an embodiment of the present application, the SMF device in fig. 1 and fig. 2 has a structure as shown in fig. 5, and the SMF device may include: a memory 501, a processor 502, a communication interface 503, and a bus 504, the bus 504 being used to enable connection and intercommunication among these devices.

The communication interface 503 may be implemented by an antenna, and may be configured to perform data interaction with an external network element, for example: the communication interface 503 of the SMF device may send and receive packets or other information to and from the AMF device.

The processor 502 may be a Central Processing Unit (CPU), an Application Specific Integrated Circuit (ASIC), or one or more Integrated circuits configured to implement embodiments of the present invention. For example: one or more microprocessors (DSP), or one or more Field Programmable Gate Arrays (FPGA). The processor 502 has a processing management function, and specifically, the processor 502 in the SMF device may process data or information sent by the received AMF device, the UPF device, or the PCRF device, or process information or data sent by other devices.

The Memory 501 may be a Read-Only Memory (ROM) or other types of static storage devices that can store static information and instructions, a Random Access Memory (RAM) or other types of dynamic storage devices that can store information and instructions, an Electrically Erasable Programmable Read-Only Memory (EEPROM), a Compact Disc Read-Only Memory (CD-ROM) or other optical Disc storage, optical Disc storage (including Compact Disc, laser Disc, optical Disc, digital versatile Disc, blu-ray Disc, etc.), a magnetic Disc storage medium or other magnetic storage device, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer, but is not limited to these. The memory 501 may be self-contained and coupled to the processor 502 via a bus 504. The memory 501 may also be integrated with the processor 502.

The method for transmitting messages provided by the present application will be specifically described below with reference to the communication systems shown in fig. 1 to 5 and the AMF device and the SMF device.

First, terms related to the present application are briefly introduced to facilitate understanding.

1) A first interface

The first interface is an interface between the AMF device and the RAN device shown in fig. 2 (corresponding to N2 in fig. 2).

2) A second interface

The second interface is an interface between the AMF device and the SMF device shown in fig. 2, specifically, an interface between a first device serving the UE in the AMF device and the SMF device.

3) A first device

When the AMF device in fig. 2 is implemented as fig. 3, the first device is a processing unit in the AMF device, the group to which the first device belongs is the AMF device where the processing unit is located, and the second interface is an interface between the processing unit in the AMF device and the SMF device (corresponding to N11 in fig. 2).

When the AMF device in fig. 2 is implemented as the AMF group shown in fig. 4, the first device is an AMF instance in the AMF group, the group to which the first device belongs is the AMF group in which the AMF instance is located, and the second interface is an interface between the AMF instance in the AMF group and the SMF device (corresponding to N11 in fig. 2).

4) A second device

And the second equipment is the equipment which is newly determined by the SMF equipment to serve the UE after deleting the second interface information between the first equipment and the SMF equipment, which is saved in the UE session context.

When the AMF device in fig. 2 is implemented as in fig. 3, the second device is a processing unit in the AMF device.

When the AMF device in fig. 2 is implemented as the AMF group shown in fig. 4, the second device is one AMF instance in the AMF group.

As shown in fig. 6, to solve the problem of load imbalance in the prior art, an embodiment of the present application provides a method for message transmission, and when the method is applied to the scenario shown in fig. 4, an interaction flow between a UE, a RAN device, an AMF instance 1, an AMF instance 2, and an SMF device is taken as an example for description, where the AMF instance 1 and the AMF instance 2 belong to the same AMF group, the method includes three phases, a first phase is a session establishment process, corresponding to steps 601 to 603; the second stage is the processing procedure of entering the idle state by the UE, corresponding to steps 604 to 607; the third phase is a process in which the UE re-enters the connection state when the SMF device needs to send a downlink message, corresponding to steps 608 to 611. The method specifically comprises the following steps:

601. the UE sends a session establishment request to AMF instance 1, and AMF instance 1 receives the session establishment request.

The sending of the session establishment request to the AMF instance 1 by the UE is to trigger a process of establishing a User Datagram Protocol (PDU) session, and when the UE initiates the process of establishing the PDU session, the UE is in a connected state, and at this time, the AMF instance 1 serves the UE.

602. The AMF instance 1 sends a session establishment request to the SMF equipment, and the SMF equipment receives the session establishment request.

Among them, the session establishment request can have the following three implementations.

The first method comprises the following steps: the second interface information (N11 interface information) of AMF instance 1 is included in the session establishment request.

And the second method comprises the following steps: the session establishment request includes the second interface information (N11 interface information) of AMF instance 1 and indication information of the AMF group to which AMF instance 1 belongs.

And the third is that: the session establishment request includes second interface information (N11 interface information) of AMF instance 1, a deletion instruction, and instruction information of the AMF group to which AMF instance 1 belongs.

The indication information of the AMF group may be the AMF group ID or a default route of the AMF group. In the embodiment corresponding to fig. 6, the indication information of the AMF group is exemplified as the AMF group ID.

It should be further noted that, if the third implementation manner is adopted, the AMF instance 1 needs to first determine whether the AMF group to which the AMF instance 1 belongs supports stateless, and if the AMF group supports stateless, the AMF instance 1 carries the deletion instruction in the session establishment request. With reference to fig. 4, the AMF group supporting stateless means that the AMF instance does not store the UE session context information, the session context information of the UE served by each AMF instance in the AMF group is stored in the DB of the AMF group, and each AMF instance in the same AMF group may share the UE session context information stored in the DB, so that each AMF instance may process not only the related information of the UE served by itself but also the related information of other UEs.

And the deletion instruction is used for indicating the SMF equipment to delete the second interface information in the UE session context stored by the SMF equipment when the SMF equipment receives the first interface release message.

603. The SMF device saves the information carried in the session establishment request in the UE session context.

It can be understood that, in each implementation manner of the session establishment request described in step 602 above, the session establishment request carries the second interface information of the AMF instance 1, because the AMF instance currently serving the UE is the AMF instance 1, the SMF device needs to store the second interface information of the AMF instance 1 in the UE session context, so that when the UE is in a connected state, the SMF device can directly send the downlink message to the AMF instance 1 serving the UE through the second interface information stored in the UE session context.

In addition, if the session establishment request further includes indication information of the AMF group, the SMF device further needs to store the indication information of the AMF group in the UE session context, and similarly, if the session establishment request further includes a deletion indication, the SMF device further needs to store the deletion indication in the UE session context.

It should be noted that the UE session context may be stored in the SMF device, or may be stored in other devices having a storage function.

The above steps 601 to 603 are session establishment procedures, and after the session establishment is completed, when the UE enters the idle state, a processing procedure for the UE to enter the idle state needs to be executed.

604. The RAN equipment sends a first interface release request message to AMF example 1, and AMF example 1 receives the first interface release request message.

605. The AMF example 1 equipment releases the first interface according to the first interface release request message.

It is to be understood that after the AMF instance 1 releases the first interface between the AMF instance 1 and the RAN, the UE switches from the connected state to the idle state.

606. The AMF example 1 sends a first interface release message to the SMF device, and the SMF device receives the first interface release message.

It should be noted that, corresponding to step 602, the first interface release message also includes three implementation manners.

The first method comprises the following steps: if the session establishment request is the first implementation manner described in step 602, the first interface release message may carry a deletion instruction, instruction information of the AMF group to which the AMF instance 1 belongs, and a first interface release notification.

And the second method comprises the following steps: if the session establishment request is the second implementation manner described in step 602, the first interface release message may carry a deletion instruction and a first interface release notification.

And the third is that: if the session establishment request is the third implementation manner described in step 602, the first interface release message may carry a first interface release notification.

It should be noted that, if the AMF instance 1 needs to carry the deletion instruction in the first interface release message, it needs to first determine whether the AMF group to which the AMF instance 1 belongs supports the stateless state, and if the AMF group supports the stateless state, the AMF instance 1 will carry the deletion instruction in the first interface release message.

607. And the SMF equipment deletes the second interface information in the UE session context according to the deletion instruction under the condition of receiving the first interface release message.

If the first interface release message carries the deletion instruction, the SMF device deletes the second interface information in the UE session context directly according to the deletion instruction carried in the first interface release message. And if the first interface release message does not carry the deletion instruction and the deletion instruction is stored in the UE session context, the SMF equipment deletes the second interface information according to the deletion instruction stored in the UE session context.

The SMF equipment receives the first interface release message, which indicates that the UE enters the idle state, and deletes the second interface information in the UE session context at the moment, so that the SMF equipment can avoid taking the AMF instance 1 as an AMF instance serving the UE according to the second interface information in the UE session context when the UE enters the link state again. At this time, because the second interface information does not exist in the UE session context, the AMF instance serving the UE can be reselected only in the AMF group, so that the UE is prevented from being served by the same AMF instance all the time.

The above steps 604 to 607 are processing procedures for the UE to enter the idle state, and if the subsequent SMF device receives the downlink message for the UE, the following steps 608 to 611 need to be executed to make the UE enter the connected state again.

608. When the SMF device needs to send a downlink message, the SMF device selects an AMF instance serving the UE from the AMF group, for example, AMF instance 2, according to the AMF group ID.

The SMF device may search for an AMF instance serving the UE from a Network Function redundancy Function (NRF) device or other devices according to the AMF group ID. The specific method for selecting the AMF instance serving the UE by the SMF device according to the AMF group ID is the same as that in the prior art, and is not described herein again.

In one possible implementation, after reselecting the AMF instance 2 serving the UE, the SMF device may store interface information between the SMF device and the AMF instance 2 in a UE session context, so that in a case where the UE is always in a connected state, the SMF device directly communicates with the AMF instance 2 without reselecting the AMF instance. Alternatively, in another possible implementation manner, the SMF device may also save interface information between the SMF device and the AMF instance 2 through subsequent steps 610 to 611.

609. The SMF device sends a downlink message to the AMF instance 2 through an interface between the SMF device and the AMF instance 2, and the AMF instance 2 receives the downlink message.

It should be noted that, after the SMF device sends the downlink message to the AMF instance 2 found according to the AMF group identifier, the AMF instance 2 may also reselect an AMF instance for the UE, for example, the AMF instance 3, and send the downlink message to the AMF instance 3, or send the identifier of the AMF instance 3 to the SMF device, and send the downlink message to the AMF instance 3 by the SMF device.

The flow of the subsequent processing of the downlink message after the AMF instance 2 receives the downlink message is the same as that in the prior art, and is not described here again.

It should be noted that, in the subsequent flow, after the UE re-enters the connected state, steps 610 to 611 may also be performed.

610. The AMF instance 2 sends a response message to the SMF device, the response message comprises interface information between the AMF instance 2 and the SMF device, and the SMF device receives the response message.

611. The SMF device saves interface information between AMF instance 2 and the SMF device in the UE session context.

Compared with the prior art in which the SMF device always selects the AMF instance serving the UE last time to provide the service for the UE, in the embodiment of the present application, when the RAN releases the interface between the RAN and the AMF instance serving the UE, it is described that the UE enters the idle state, the SMF device deletes the interface information between the SMF device in the context of the UE and the AMF instance serving the UE, and when the SMF device needs to send a downlink message for the UE, the SMF device cannot directly search the interface information between the AMF instance serving the UE last time and the SMF device from the context of the UE, and does not continuously select the AMF instance serving the UE last time, but reselects the AMF instance, thereby avoiding the occurrence of load imbalance caused by the SMF device always selecting the AMF instance serving the UE last time.

In the embodiment shown in fig. 6, it is described that the indication information of the AMF group is an AMF group ID, in another implementation manner provided in the embodiment of the present application, the indication information of the AMF group may also be a default route of the AMF group, and when the indication information of the AMF group is the default route of the AMF group, as shown in fig. 7, the method may be implemented as the following steps 701 to 712.

Steps 701 to 707 are the same as steps 601 to 607, and steps 711 to 712 are the same as steps 610 to 611, which are not repeated herein.

708. When the SMF equipment receives the downlink message to be sent, the SMF equipment sends the downlink message to the equipment corresponding to the default route of the AMF group, and the equipment corresponding to the default route of the AMF group receives the downlink message.

The default route of the AMF group is directed to the ASF unit, where the ASF unit is a network function, and specifically may be a default AMF instance in the AMF group, or may also be a dedicated network function, for example, may be a load balancer.

709. The ASF unit selects an AMF instance serving the UE, e.g. AMF instance 2.

710. The ASF unit sends the downlink message to the AMF instance 2, and the AMF instance 2 receives the downlink message.

Alternatively, in another possible implementation manner, step 710 may also be replaced with that the ASF unit sends the identifier of AMF instance 2 to the SMF device, and then the SMF device sends the downlink message to the AMF instance 2 according to the identifier of AMF instance 2.

Fig. 6 and fig. 7 are corresponding embodiments, which are implementation manners when the method for message transmission of the present application is applied to the scenario shown in fig. 4, and in another embodiment of the present application, the method for message transmission of the present application may also be applied to the scenario shown in fig. 3, which is described by taking an interaction flow among a UE, a RAN device, a processing unit 1, a processing unit 2, and an SMF device as an example, where the processing unit 1 and the processing unit 2 belong to the same AMF device, as shown in fig. 8, the method includes:

801. the UE sends a session establishment request to the processing unit 1, and the processing unit 1 receives the session establishment request.

The UE sends the session establishment request to the processing unit 1 to trigger the PDU session establishment process, and when the UE initiates the PDU session establishment process, the UE is in a connected state, and the processing unit 1 serves the UE at this time.

802. The processing unit 1 sends a session establishment request to the SMF device, and the SMF device receives the session establishment request.

The first method comprises the following steps: the second interface information (N11 interface information) of processing unit 1 is included in the session establishment request.

And the second method comprises the following steps: the session establishment request includes the second interface information (N11 interface information) of processing unit 1 and indication information of the AMF device to which processing unit 1 belongs.

And the third is that: the session establishment request includes the second interface information (N11 interface information) of processing unit 1, a deletion instruction, and instruction information of the AMF device to which processing unit 1 belongs.

Note that the indication information of the AMF device may be the AMF device ID or the default route of the AMF device, and in the embodiment corresponding to fig. 8, the indication information of the AMF device is described as the AMF device ID.

803. The SMF device saves the information carried in the session establishment request in the UE session context.

It can be understood that, in each implementation manner of the session establishment request described in step 802 above, the session establishment request carries the second interface information of the processing unit 1, and because the processing unit currently serving as the UE is the processing unit 1, the SMF device needs to store the second interface information of the processing unit 1 in the UE session context, so that when the UE is in a connected state, the SMF device can directly send the downlink message to the processing unit 1 serving as the UE through the second interface information stored in the UE session context.

In addition, if the session establishment request further includes indication information of the AMF device, the SMF device further needs to store the indication information of the AMF device in the UE session context, and similarly, if the session establishment request further includes a deletion indication, the SMF device further needs to store the deletion indication in the UE session context.

The above steps 801 to 803 are session establishment procedures, and after the session establishment is completed, when the UE enters the idle state, a processing procedure for the UE to enter the idle state needs to be executed.

804. The RAN device sends a first interface release message to processing unit 1, and processing unit 1 receives the first interface release message.

805. The processing unit 1 releases the first interface according to the first interface release message.

It is understood that after the processing unit 1 releases the first interface between the processing unit 1 and the RAN, the UE switches from the connected state to the idle state.

806. The processing unit 1 sends a first interface release message to the SMF device, and the SMF device receives the first interface release message.

It should be noted that, corresponding to step 802, the first interface release message also includes three implementation manners.

The first method comprises the following steps: if the session establishment request is the first implementation manner described in step 802, the first interface release message may carry a deletion instruction, instruction information of the AMF group to which the processing unit 1 belongs, and a first interface release notification.

And the second method comprises the following steps: if the session establishment request is the second implementation manner described in step 802, the first interface release message may carry a deletion instruction and a first interface release notification.

And the third is that: if the session establishment request is the third implementation manner described in step 802, the first interface release message may carry a first interface release notification.

It should be noted that, if the processing unit 1 needs to carry the deletion instruction in the first interface release message, it needs to first determine whether each processing unit of the AMF device to which the processing unit 1 belongs supports the stateless state, and if each processing unit of the AMF device supports the stateless state, the processing unit 1 will carry the deletion instruction in the first interface release message, and with reference to fig. 3, each processing unit of the AMF device supports the stateless state means that each processing unit does not store the UE session context information, the session context information of the UE served by each processing unit is stored in the DB, and the processing units in the same AMF device may share the UE session context information stored in the DB.

807. And the SMF equipment deletes the second interface information in the UE session context according to the deletion instruction under the condition of receiving the first interface release message.

The SMF device receives the first interface release message, which indicates that the UE has entered the idle state, and at this time, the SMF device deletes the second interface information in the UE session context, so that it is possible to avoid that, when the UE re-enters the link state, the SMF device still uses the processing unit 1 as a processing unit serving the UE according to the second interface information in the UE session context. At this time, because the second interface information does not exist in the session context of the UE, the processing unit serving the UE can only be reselected from the SMF device, thereby avoiding that the UE is always served by the same processing unit.

The above steps 804 to 807 are processing procedures for the UE to enter the idle state, and if the subsequent SMF device receives the downlink message for the UE, the following steps 808 to 811 need to be executed to make the UE enter the connected state again.

808. And when the SMF equipment needs to send the downlink message, the SMF equipment selects the ASF unit of the AMF equipment according to the ID of the AMF equipment.

The SMF device may search for an external interface of the AMF device from the NRF device or another device according to the AMF device ID, where the interface may be transport layer information of the ASF unit. In this embodiment, the ASF unit may be one LB unit in the AMF device, or may be one processing unit in the AMF device.

In the case that the ASF unit is one processing unit in the AMF device, the SMF device may directly send the downlink message to the processing unit, and the processing unit provides a service for the UE, or after receiving the downlink message sent by the SMF device, the processing unit may also perform the following steps 810 to 811, reselect the processing unit serving the UE, and send the downlink message to the reselected processing unit.

809. The SMF equipment sends a downlink message to the ASF unit, and the ASF unit receives the downlink message.

It should be noted that, when the ASF unit is an LB unit, steps 810 to 811 may also be performed.

810. The ASF unit selects the processing unit serving the UE, e.g. processing unit 2.

811. The ASF unit sends a downlink message to the processing unit 2, and the processing unit 2 receives the downlink message.

In another possible implementation manner, the ASF unit may further send the identifier of the processing unit 2 to the SMF device, and the SMF device sends the downlink message to the processing unit 2 according to the identifier of the processing unit 2.

The flow of the subsequent processing of the downlink message after the processing unit 2 receives the downlink message is the same as that in the prior art, and is not described here again.

It should be noted that, in the subsequent flow, after the UE re-enters the connected state, steps 812 to 813 may also be performed.

812. The processing unit 2 sends a response message to the SMF device, where the response message includes interface information between the processing unit 2 and the SMF device, and the SMF device receives the response message.

813. The SMF device saves interface information between the processing unit 2 and the SMF device in the UE session context.

In the message transmission method provided in the embodiment of the present application, after the RAN releases the interface between the RAN and the processing unit serving the UE, the SMF device deletes the interface between the SMF device in the context of the UE and the processing unit serving the UE, and thus when the SMF device needs to send a downlink message, the process of selecting the processing unit needs to be triggered again, so that load balancing between the processing units can be achieved.

The scheme provided by the embodiment of the invention is mainly introduced from the perspective of the SMF device. It is understood that the SMF device includes hardware structures and/or software modules for performing the respective functions. Those of skill in the art would readily appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as hardware or combinations of hardware and computer software. Whether a function is performed as hardware or computer software drives hardware depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.

In the embodiment of the present application, the SMF device may be divided into the functional modules according to the above method example, for example, each functional module may be divided corresponding to each function, or two or more functions may be integrated into one processing module. The integrated module can be realized in a hardware mode, and can also be realized in a software functional module mode. It should be noted that, in the embodiments of the present application, the division of the modules is schematic, and is only one logical function division, and there may be another division manner in actual implementation.

In the case of adopting each functional module divided corresponding to each function, an embodiment of the present application provides a message transmission apparatus, which may be implemented as the SMF device in the foregoing embodiment. As shown in fig. 9, fig. 9 shows a schematic diagram of a possible structure of the SMF device in the above embodiment. The SMF device includes: a receiving module 901, a deleting module 902 and a sending module 903.

The receiving module 901 is configured to receive a deletion instruction from the first device and instruction information of a group to which the first device belongs, where the deletion instruction is used to instruct the deleting module 902 to delete the second interface information in the UE session context when the receiving module 901 receives the first interface release message.

A deleting module 902, configured to delete the second interface information in the UE session context according to the deletion instruction when the receiving module 901 receives the first interface release message.

A sending module 903, configured to send the downlink message to the second device when the downlink message needs to be sent.

In another possible implementation manner of the embodiment of the present application, the apparatus further includes: a storage module 904.

The receiving module 901 is specifically configured to receive a session establishment request from a first device, where the session establishment request includes indication information of a group, a deletion indication, and second interface information.

A storage module 904, configured to store the indication information, the deletion indication, and the second interface information of the group in the UE session context.

The deleting module 902 is specifically configured to, when the receiving module receives the first interface release message sent by the first device, delete the second interface information in the UE session context according to the deletion instruction in the UE session context.

In another possible implementation manner of the embodiment of the present application, the receiving module 901 is specifically configured to receive a session establishment request from a first device, where the session establishment request includes indication information of a group and second interface information; and receiving a first interface release message from the first device, wherein the first interface release message comprises a deletion instruction.

A storage module 904, configured to store the indication information of the group and the second interface information in a UE session context.

In another possible implementation manner of the embodiment of the present application, the receiving module 901 is specifically configured to receive a session establishment request from the first device, where the session establishment request includes second interface information; and receiving a first interface release message from the first device, wherein the first interface release message comprises the indication information and the deletion indication of the group.

A storage module 904 for storing the second interface information in the UE session context.

A deleting module 902, configured to delete the second interface information in the session context of the UE according to the deletion instruction included in the first interface release message.

In another possible implementation manner of the embodiment of the present application, the indication information of the group is a group identity ID of the group;

correspondingly, the sending module 903 is specifically configured to determine, according to the group ID, a second device serving the UE; and sending the downlink message to the second equipment through an interface between the message transmission device and the second equipment.

In another possible implementation manner of the embodiment of the present application, the indication information of the group is a default route of the group;

a sending module 903, configured to send a downlink message to a device corresponding to a default route of the group; receiving a second device identifier of a device corresponding to the default route from the group, wherein the second device is a second device selected by the UE for the device corresponding to the default route of the group; and sending the downlink message to the second equipment corresponding to the second equipment identifier received by the receiving module through an interface between the message transmission device and the second equipment.

the sending module 903 is specifically configured to send the downlink message to the second device through the device corresponding to the default route of the group, where the second device is the second device selected by the UE and corresponding to the default route of the group.

In addition, the storage module 904 is configured to, after the receiving module 901 receives the message from the second device, store interface information between the apparatus for message transmission and the second device in the UE session context.

Specifically, corresponding to the foregoing method embodiment, the receiving module 901 is configured to support the SMF device to receive the session establishment request sent in step 602 in fig. 6, the first interface release message sent in step 606, the response message sent in step 610, the first interface release message sent in step 702 in fig. 7, the first interface release message sent in step 706, the response message sent in step 711, and also to support the SMF device to receive the session establishment request sent in step 802 in fig. 8, the first interface release message sent in step 806, and the response message sent in step 812. A deletion module 903, configured to support the SMF device to perform step 607 in fig. 6, step 707 in fig. 7, and step 807 in fig. 8. A sending module 903, configured to support the SMF device to perform step 609 in fig. 6, step 708 in fig. 7, and step 809 in fig. 8. A storage module 904, configured to support the SMF device to perform step 603 and step 611 in fig. 6, step 703 and step 712 in fig. 7, and step 803 and step 813 in fig. 8.

All relevant contents of each step related to the above method embodiment may be referred to the functional description of the corresponding functional module, and are not described herein again.

In the case of using an integrated unit, it should be noted that the receiving module 901 and the sending module 903 shown in fig. 9 may be integrated in the communication interface 503 shown in fig. 5, so that the communication interface 503 performs specific functions of the receiving module 901 and the sending module 903. The deletion module 902 may be integrated into the processor 502 shown in fig. 5, such that the processor 502 performs the specific functions of the deletion module 902. The storage module 904 may be integrated into the memory 501 shown in fig. 5, so that the memory 501 performs specific functions of the storage module 904.

As shown in fig. 10, in order to solve the problem of load imbalance in the prior art, another embodiment of the present application provides a method for data transmission, which, when the method is applied in the scenario of fig. 4, is described by taking an interaction flow among a UE, a RAN device, an AMF instance, and an SMF device as an example, where AMF instance 1 and AMF instance 2 belong to the same AMF group, the method includes three stages, where the first stage is a session establishment process, corresponding to steps 1001 to 1003; the second stage is a processing procedure of entering an idle state by the UE, corresponding to steps 1004 to 1007; the third phase is a process in which the UE re-enters the connection state when the SMF device needs to send a downlink message, corresponding to steps 1008 to 1009. The method specifically comprises the following steps:

1001. the UE sends a session establishment request to AMF instance 1, and AMF instance 1 receives the session establishment request.

The UE sending the session establishment request to the AMF instance 1 is to trigger a PDU session establishment procedure, and when the UE initiates the PDU session establishment procedure, the UE is in a connected state, and at this time, the AMF instance 1 serves the UE.

1002. AMF instance 1 sends a session establishment request to the SMF device, and AMF instance 1 receives the session establishment request.

The first method comprises the following steps: the session establishment request includes information of AMF instance 1.

The information of the AMF instance 1 is used for the SMF device to address the AMF instance, for example, the information of the AMF instance 1 may be an AMF instance identifier, a Uniform Resource Identifier (URI) of a service endpoint in the AMF instance, or a resource identifier registered in the NRF device by the AMF instance.

And the second method comprises the following steps: the session establishment request includes information of the AMF instance 1 and indication information of the AMF group to which the AMF instance 1 belongs.

And the third is that: the session establishment request comprises AMF instance 1 information, stateless indication information and indication information of an AMF group to which the AMF instance 1 belongs.

The indication information of the AMF group may be the AMF group ID or a default route of the AMF group. In the embodiment corresponding to fig. 9, the indication information of the AMF group is exemplified as the AMF group ID.

It should be further noted that, if the third implementation manner is adopted, the AMF instance 1 needs to first determine whether the AMF group to which the AMF instance 1 belongs supports the stateless mode, and if the AMF group supports the stateless mode, the AMF instance 1 will carry the stateless indication information in the session establishment request. With reference to fig. 4, the AMF group supporting the stateless mode means that when the UE is in the idle state, the AMF instance does not store the UE session context information, the session context information of the idle UE served by each AMF instance in the AMF group is stored in the DB of the AMF group, and each AMF instance in the same AMF group may share the UE session context information stored in the DB, so that each AMF instance may process not only the related information of the UE served by itself but also the related information of other UEs.

And the stateless indication information is used for indicating the SMF device to reselect the AMF instance from the AMF group according to the indication information of the AMF group and send the downlink message to the newly selected AMF instance if the SMF device needs to send the downlink message to the AMF instance after determining that the signaling connection corresponding to the UE is released from the binding of the first interface.

The stateless indication information may be a single indication information, for example, a bit is carried in the message to indicate that the AMF group operates in the stateless mode, or may be embodied in other manners, for example, a special AMF pointer is carried in the message to indicate that the AMF group operates in the stateless mode (for example, if the AMF pointer carried in the message is identified as 1111, the AMF group operates in the stateless mode).

The binding release of the signaling connection to the first interface includes, but is not limited to, the following two cases:

In a specific implementation, the signaling in the signaling connection may refer to Next Generation Application Protocol (NGAP) signaling, or may refer to an application protocol of an N2 interface (N2reference application protocol, N2 AP).

It should be noted that, in addition to the above method for acquiring the stateless indication information, the SMF may also acquire the above stateless indication information from the local configuration information according to the indication information of the AMF group.

1003. The SMF device saves the information carried in the session establishment request in the UE session context.

It can be understood that, in each implementation manner of the session establishment request described in step 1002, the session establishment request carries information of the AMF instance 1, and because the AMF instance currently serving the UE is the AMF instance 1, the SMF device needs to store the information of the AMF instance 1 in the UE session context, so that when the UE is in a connected state, the SMF device can directly send a downlink message to the AMF instance 1 serving the UE through the information of the AMF instance 1 stored in the UE session context.

In addition, if the session establishment request further includes indication information of the AMF group, the SMF device further needs to store the indication information of the AMF group in the UE session context. Optionally, if the session establishment request further includes the stateless indication information, the SMF device further needs to store the stateless indication information in the UE session context, or optionally, the SMF device may store the stateless indication information in the AMF group or the context corresponding to the AMF.

The above steps 1001 to 1003 are session establishment procedures, and after the session establishment is completed, when the UE enters the idle state, a processing procedure for the UE to enter the idle state needs to be executed.

1004. The RAN equipment sends a release message to AMF instance 1, and AMF instance 1 receives the release message.

The release message is used to instruct the AMF instance 1 to release the binding between the signaling connection corresponding to the UE and the first interface.

1005. And the AMF example 1 equipment releases the binding of the signaling connection corresponding to the UE and the first interface according to the release message.

It can be understood that, after the AMF instance 1 releases the binding between the signaling connection corresponding to the UE between the AMF instance 1 and the RAN and the first interface, the UE is switched from the connection state to the idle state.

1006. The AMF instance 1 sends a session update request or a release notification to the SMF device, wherein the session update request comprises a release reason, and the SMF device receives the session update request or the release notification.

The release reason is used for indicating the reason of binding release between the signaling connection corresponding to the UE and the first interface. The release notification is used for indicating that the binding of the signaling connection corresponding to the UE and the first interface is released.

It should be noted that, corresponding to step 1002, the session update request message also includes three implementation manners.

The first method comprises the following steps: if the session establishment request is the first implementation manner described in step 1002, the session update request may carry the indication information and the release reason of the AMF group to which the AMF instance 1 belongs. The optional session update request may also carry stateless indication information.

And the second method comprises the following steps: if the session establishment request is the second implementation manner described in step 1002, the session update request may carry a release reason. The optional session update request may also carry stateless indication information.

And the third is that: if the session establishment request is the third implementation manner described in step 1002, the session update request message may carry a release reason.

It should be noted that, if the AMF instance 1 needs to carry the stateless indication information in the session update request message, it needs to first determine whether the AMF group to which the AMF instance 1 belongs supports the stateless mode, and if the AMF group supports the stateless mode, the AMF instance 1 will carry the stateless indication information in the session update request.

Similarly, the release notification also includes the above three implementations.

It should be noted that, in this step, in addition to the AMF instance 1 sending the session update request or the release notification to the SMF device, and in the session update request or carrying the release reason, the AMF instance 1 may also send a notification that the UE enters the idle state to the SMF device. Similarly, entering idle notification also includes the three implementations described above.

1007. And the SMF equipment judges the binding release of the signaling connection corresponding to the UE and the first interface according to the release reason, the release notice or the notice that the UE enters an idle state.

In one implementation, the SMF device deletes the AMF instance 1 information in the UE session context according to the stateless indication information.

If the session update request message carries stateless indication information, the SMF device directly deletes the information of the AMF instance 1 in the UE session context according to the stateless indication information carried in the session update request message. And if the session updating request message does not carry the stateless indication information and the stateless indication information is stored in the UE session context, the SMF equipment deletes the information of the AMF instance 1 according to the stateless indication information stored in the UE session context. In addition, the SMF device may further obtain the stateless indication information from the local configuration information according to the information for configuring the AMF group, and delete the information of the AMF capability 1 according to the stateless indication information in the local configuration information.

The SMF equipment judges that the UE enters an idle state according to the received session updating request or the release notification or according to the received idle state entering notification of the UE, and at the moment, the SMF equipment deletes the information of the AMF instance 1 in the session context of the UE, so that the SMF equipment can be prevented from taking the AMF instance 1 as the AMF instance serving the UE according to the information of the AMF instance 1 in the session context of the UE when the UE enters a connection state again. At this time, because the information of the AMF instance 1 does not exist in the UE session context, the AMF instance serving the UE can be reselected only in the AMF group, so that the condition that the UE is served by the same AMF instance all the time is avoided.

In another implementation manner, the SMF device does not delete the information of the AMF instance 1 in step 1007, and the SMF device determines that the UE has entered an idle state according to the received session update request or release notification or according to the received notification that the UE enters an idle state, and the SMF device sets a Connection Management (CM) state of the UE to an idle state.

The above steps 1004 to 1007 are processing procedures for the UE to enter the idle state, and if the subsequent SMF device receives a downlink message for the UE, the following steps 1008 to 1009 need to be executed to make the UE enter the connected state again.

1008. When the SMF device needs to send a downlink message, the SMF device selects an AMF instance serving the UE from the AMF group, for example, AMF instance 2, according to the AMF group ID.

Optionally, when the SMF device needs to send a downlink message, it may be determined whether the binding between the signaling connection corresponding to the UE and the first interface is released, and if it is determined that the binding between the signaling connection corresponding to the UE and the first interface is released, an AMF instance serving the UE is selected from the AMF group according to the AMF group ID.

In one implementation, the SMF device queries the UE session context, and if the UE session context does not store any AMF instance information, the SMF device selects an AMF instance serving the UE according to the AMF group ID.

In another implementation, the SMF device determines that the CM status of the UE is in an idle state, and the SMF device receives the stateless indication information from the AMF instance 1 (as in step 1001 or 1006) or the SMF device determines that the AMF group operates in the stateless mode according to the configuration, and then, even if the AMF instance information is stored in the UE session context, the SMF device selects the AMF instance serving the UE according to the AMF group ID.

The SMF device may save the information of AMF instance 2 in the UE session context after reselecting AMF instance 2 serving the UE, so that in case the UE is always in a connected state, the SMF device communicates directly with AMF instance 2 without reselecting the AMF instance.

1009. The SMF equipment sends a downlink message to the AMF instance 2, and the AMF instance 2 receives the downlink message.

Compared with the prior art in which the SMF device always selects the AMF instance serving the UE last time to provide the service for the UE, in the embodiment of the present application, when the RAN releases the binding between the interface between the RAN and the AMF instance serving the UE and the signaling corresponding to the UE, it indicates that the UE enters the idle state, and the SMF device deletes the information of the AMF instance in the context of the UE, and when the SMF device needs to send the downlink message for the UE, it is not possible to directly search the information of the AMF instance serving the UE last time from the context of the UE, and it is not possible to continuously select the AMF instance serving the UE last time, but to reselect the AMF instance, so that the phenomenon of load imbalance caused by the SMF device always selecting the AMF instance serving the UE last time is avoided.

In the case of adopting each functional module divided corresponding to each function, an embodiment of the present application provides a message transmission apparatus, which may be implemented as the SMF device in the foregoing embodiment. As shown in fig. 11, fig. 11 shows another possible structural schematic diagram of the SMF device involved in the above embodiment. The SMF device includes: an acquisition module 1101 and a sending module 1102.

An obtaining module 1101, configured to obtain stateless indication information and group indication information of a group to which a first device belongs, where the stateless indication information is used to indicate that a second device serving the UE is selected according to the group indication information when it is determined that a downlink message needs to be sent after a signaling connection corresponding to the user equipment UE is released from being bound to a first interface, the first device is a device serving the UE before the signaling connection is released from being bound to the first interface, and the first interface is an interface between a radio access network RAN and the first device.

A sending module 1102, configured to send, when the obtaining module 1101 receives the release notification from the first device and a downlink message needs to be sent, the downlink message to a second device, where the second device is a device serving the UE determined according to the group indication information. The release notification is used for indicating that the binding between the signaling connection corresponding to the UE and the first interface is released.

In another possible implementation manner of the embodiment of the present application, the apparatus further includes a determining module 1103.

A determining module 1103, configured to determine a binding release between a signaling connection corresponding to the UE and the first interface.

In another possible implementation manner of the embodiment of the present application, the determining module 1103 is further configured to determine, if the sending module needs to send a downlink message, and the determining module 1103 determines that the binding between the signaling connection corresponding to the UE and the first interface is released, the second device for serving the UE according to the group indication information.

In another possible implementation manner of the embodiment of the present application, the obtaining module 1101 is specifically configured to receive a session establishment request from a first device, where the session establishment request includes the group indication information; or receiving a release notification from the first device, wherein the release notification includes the group indication information.

In another possible implementation manner of the embodiment of the present application, the obtaining module 1101 is specifically configured to receive a session establishment request from a first device, where the session establishment request includes stateless indication information; or receiving a release notice from the first device, wherein the release notice comprises the stateless indication information; or acquiring the stateless indication information from the local configuration information.

In another possible implementation manner of the embodiment of the present application, the apparatus further includes a deleting module 1104.

A deleting module 1104, configured to delete the information of the first device in the UE session context according to the stateless indication information after the obtaining module 1101 receives the release notification from the first device.

In another possible implementation manner of the embodiment of the present application, the apparatus further includes: a storage module 1105.

A storing module 1105, configured to save a release state of the binding between the signaling connection and the first interface after the obtaining module 1101 receives the release notification from the first device.

Optionally, the determining module 1103 is further configured to determine, according to a release state of the binding between the signaling connection and the first interface, that the binding between the signaling connection and the first interface is released;

further, the determining module 1103 is further configured to determine, if the sending module 1102 needs to send the downlink message, and the determining module 1103 determines that the binding between the signaling connection and the first interface is released according to the release state of the binding between the signaling connection and the first interface, the second device for serving the UE according to the group indication information.

The group indication information is a group identity ID of a group to which the first equipment belongs;

the determining module 1103 is specifically configured to determine, if the sending module 1102 needs to send the downlink message, and the determining module 1103 determines that the binding between the signaling connection and the first interface is released according to the release state of the binding between the signaling connection and the first interface, the second device serving the UE according to the group ID.

Specifically, corresponding to the above method embodiment, the obtaining module 1101 is configured to support the SMF device to obtain the session establishment request sent in step 1002 in fig. 10, and obtain the first interface release message sent in step 1006. A sending module 1102, configured to support the SMF device to perform step 1009 in fig. 10. A deleting module 1104, configured to support the SMF device to execute step 1007 in fig. 10. A determining module 1103, configured to support the SMF device to perform step 1008 in fig. 10. A storage module 1105, configured to support the SMF device to execute step 1003 in fig. 10.

In the case of an integrated unit, it should be noted that the obtaining module 1101 and the sending module 1102 shown in fig. 11 may be integrated in the communication interface 503 shown in fig. 5, so that the communication interface 503 performs specific functions of the obtaining module 1101 and the sending module 1102. The determining module 1103 and the deleting module 1104 may be integrated in the processor 502 shown in fig. 5, so that the processor 502 performs specific functions of the determining module 1103 and the deleting module 1104. The memory module 1105 may be integrated into the memory 501 shown in fig. 5, such that the memory 501 performs the specific functions of the memory module 1105.

Embodiments of the present application further provide a computer storage medium for storing computer software instructions for the SMF device, which includes a program designed to perform the steps performed by the SMF device in the above embodiments.

Embodiments of the present application also provide a computer program product, such as a computer-readable storage medium, comprising a program designed to perform the steps performed by the SMF device in the above embodiments.

The steps of a method or algorithm described in connection with the disclosure herein may be embodied in hardware or in software instructions executed by a processor. The software instructions may be comprised of corresponding software modules that may be stored in Random Access Memory (RAM), flash Memory, Read Only Memory (ROM), Erasable Programmable ROM (EPROM), Electrically Erasable Programmable ROM (EEPROM), registers, a hard disk, a removable disk, a compact disc Read Only Memory (CD-ROM), or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor such the processor can read information from, and write information to, the storage medium. Of course, the storage medium may also be integral to the processor. The processor and the storage medium may reside in an ASIC. Additionally, the ASIC may reside in a core network interface device. Of course, the processor and the storage medium may reside as discrete components in a core network interface device.

In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other manners. For example, the above-described apparatus embodiments are merely illustrative, and for example, the division of the units is only one logical division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection of some interfaces, devices or units, and may be an electric or other form.

The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may also be distributed on a plurality of network devices. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.

In addition, each functional unit in the embodiments of the present invention may be integrated into one processing unit, or each functional unit may exist independently, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, or in a form of hardware plus a software functional unit.

Through the above description of the embodiments, those skilled in the art will clearly understand that the present application can be implemented by software plus necessary general hardware, and certainly, the present application can also be implemented by hardware, but in many cases, the former is a better implementation. Based on such understanding, the technical solutions of the present application may be substantially implemented or a part of the technical solutions contributing to the prior art may be embodied in the form of a software product, where the computer software product is stored in a readable storage medium, such as a floppy disk, a hard disk, or an optical disk of a computer, and includes several instructions for enabling a computer device (which may be a personal computer, a server, or a network device) to execute the methods described in the embodiments of the present application.

The above description is only an embodiment of the present application, but the scope of the present application is not limited thereto, and all changes and substitutions within the technical scope of the present application should be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. A method of message transmission, comprising:

the method comprises the steps that session management function equipment receives a deletion instruction from first equipment and indication information of a group to which the first equipment belongs, wherein the deletion instruction is used for indicating that the session management function equipment deletes second interface information in a session context of User Equipment (UE) when receiving a first interface release message, the first interface is an interface between a Radio Access Network (RAN) and the first equipment, and the second interface is an interface between the first equipment and the session management function equipment; wherein, the deleting indication and the indication information of the group are carried in a session establishing request; or the indication information of the group is carried in the session establishment request, and the deletion indication is carried in the first interface release message; or, the indication information of the group and the deletion indication are carried in the first interface release message;

under the condition that the session management function device receives a first interface release message from the first device, the session management function device deletes second interface information in the UE session context according to the deletion instruction;

when the session management function device needs to send a downlink message, the session management function device sends the downlink message to a second device, and the second device is a device serving the UE determined according to the indication information of the group.

2. The method according to claim 1, wherein the session management function device receives the deletion indication from the first device and the indication information of the group to which the first device belongs, and includes:

the session management function device receives a session establishment request from the first device, wherein the session establishment request comprises the group indication information, the deletion indication and the second interface information;

after the session management function device receives the session establishment request from the first device, the method further comprises:

and the session management function equipment stores the indication information, the deletion indication and the second interface information of the group in the UE session context.

3. The method according to claim 2, wherein the session management function device deletes the second interface information in the UE session context according to the deletion indication, including:

and the session management function equipment deletes the second interface information in the UE session context according to the deletion indication in the UE session context.

4. The method according to claim 1, wherein the session management function device receives the deletion indication from the first device and the indication information of the group to which the first device belongs, and includes:

the session management function device receives a session establishment request from the first device, wherein the session establishment request comprises the indication information of the group and the second interface information;

the session management function device receives a first interface release message from the first device, wherein the first interface release message comprises the deletion instruction;

the session management function device saves the indication information of the group and the second interface information in the UE session context.

5. The method according to claim 1, wherein the session management function device receives the deletion indication from the first device and the indication information of the group to which the first device belongs, and includes:

the session management function device receives a first interface release message from the first device, where the first interface release message includes the indication information of the group and the deletion indication;

before the session management function device receives the first interface release message from the first device, the method further includes:

the session management function device receives a session establishment request from the first device, wherein the session establishment request comprises the second interface information;

and the session management function equipment stores the second interface information in the UE session context.

6. The method according to claim 4 or 5, wherein the session management function device deletes the second interface information in the UE session context according to the deletion indication, including:

and the session management function device deletes the second interface information in the session context of the UE according to the deletion instruction included in the first interface release message.

7. The method of claim 1, wherein the indication information of the group is a group identity ID of the group; correspondingly, the sending, by the session management function device, the downlink message to the second device includes:

the session management function device determines a second device serving the UE according to the group ID;

and the session management function device sends the downlink message to the second device through an interface between the session management function device and the second device.

8. The method of claim 1, wherein the indication information of the group is a default route of the group; correspondingly, the sending, by the session management function device, the downlink message to the second device includes:

when the session management function device needs to send a downlink message, the session management function device sends the downlink message to a device corresponding to the default route of the group;

the session management function device receives a second device identifier of a device corresponding to a default route from the group, wherein the second device is a second device selected by the UE for the device corresponding to the default route of the group;

and the session management function device sends the downlink message to the second device corresponding to the second device identifier through an interface between the session management function device and the second device.

9. The method of claim 1, wherein the indication information of the group is a default route of the group; correspondingly, the sending, by the session management function device, the downlink message to the second device includes:

when the session management function device needs to send a downlink message, the session management function device sends the downlink message to the second device through a device corresponding to the default route of the group, and the second device is a device corresponding to the default route of the group and is a second device selected by the UE.

10. The method of claim 9, wherein after the session management function device sends the downlink message to the second device through a device corresponding to the default route of the group, the method further comprises:

and after the session management function device receives the message from the second device, the session management function device stores interface information between the session management function device and the second device in the UE session context.

11. An apparatus for message transmission, comprising:

a receiving module, configured to receive a deletion instruction from a first device and indication information of a group to which the first device belongs, where the deletion instruction is used to indicate that a deletion module deletes second interface information in a session context of a user equipment UE when the receiving module receives a first interface release message, where the first interface is an interface between a radio access network RAN and the first device, and the second interface is an interface between the first device and a device for transmitting the message; wherein, the deleting indication and the indication information of the group are carried in a session establishing request; or the indication information of the group is carried in the session establishment request, and the deletion indication is carried in the first interface release message; or, the indication information of the group and the deletion indication are carried in the first interface release message;

the deleting module is configured to delete the second interface information in the UE session context according to the deletion instruction when the receiving module receives the first interface release message from the first device;

and the sending module is used for sending the downlink message to second equipment when the downlink message needs to be sent, wherein the second equipment is equipment which is determined according to the indication information of the group and is used for serving the UE.

12. The apparatus of claim 11, further comprising: a storage module;

the receiving module is specifically configured to receive a session establishment request from the first device, where the session establishment request includes the group indication information, the deletion indication, and the second interface information;

the storage module is configured to store the indication information, the deletion indication, and the second interface information of the group in the UE session context.

13. The apparatus of claim 12,

the deleting module is specifically configured to delete the second interface information in the UE session context according to the deletion instruction in the UE session context when the receiving module receives the first interface release message sent by the first device.

14. The apparatus of claim 11, further comprising: a storage module;

the receiving module is specifically configured to receive a session establishment request from the first device, where the session establishment request includes the group indication information and the second interface information; receiving a first interface release message from the first device, wherein the first interface release message comprises the deletion instruction;

the storage module is configured to store the indication information of the group and the second interface information in the UE session context.

15. The apparatus of claim 11, further comprising: a storage module;

the receiving module is specifically configured to receive a first interface release message from the first device, where the first interface release message includes the indication information of the group and the deletion indication; receiving a session establishment request from the first device, wherein the session establishment request comprises the second interface information;

the storage module is configured to store the second interface information in the UE session context.

16. The apparatus of claim 14 or 15,

the deleting module is specifically configured to delete the second interface information in the session context of the UE according to the deletion instruction included in the first interface release message.

17. The apparatus of claim 11, wherein the indication information of the group is a group identity ID of the group;

the sending module is specifically configured to determine, according to the group ID, a second device serving the UE; and sending the downlink message to the second equipment through an interface between the message transmission device and the second equipment.

18. The apparatus of claim 11, wherein the indication information of the group is a default route of the group;

the sending module is specifically configured to send the downlink message to a device corresponding to the default route of the group; receiving a second device identifier of a device corresponding to the default route from the group, wherein the second device is a second device selected by the UE for the device corresponding to the default route of the group; and sending the downlink message to the second device corresponding to the second device identifier received by the receiving module through an interface between the message transmission device and the second device.

19. The apparatus of claim 11, wherein the indication information of the group is a default route of the group;

the sending module is specifically configured to send the downlink message to the second device through a device corresponding to the default route of the group, where the second device is a second device selected by the UE and corresponding to the default route of the group.

20. The apparatus of any one of claims 17 to 19, further comprising: a storage module;

the storage module is configured to, after the receiving module receives the message from the second device, store interface information between the message transmission apparatus and the second device in the UE session context.

21. A method of message transmission, comprising:

a session management function device acquires stateless indication information and group indication information of a group to which a first device belongs, wherein the stateless indication information is used for indicating that the session management function device selects a second device serving for a User Equipment (UE) according to the group indication information when downlink information needs to be sent after determining that a signaling connection corresponding to the UE is bound and released with a first interface, the first device is a device serving for the UE before the binding between the signaling connection and the first interface is released, and the first interface is an interface between a Radio Access Network (RAN) and the first device;

and under the condition that the session management function device receives the release notification from the first device, when the session management function device needs to send a downlink message, the session management function device sends the downlink message to a second device, wherein the second device is a device which is determined according to the group indication information and is used for serving the UE.

22. The method of claim 21, further comprising:

and the session management function equipment determines the binding release of the signaling connection corresponding to the UE and the first interface.

23. The method according to claim 21 or 22, wherein the obtaining, by the session management function device, group indication information of a group to which the first device belongs comprises:

the session management function device receives a session establishment request from the first device, wherein the session establishment request comprises the group indication information; alternatively, the first and second electrodes may be,

the session management function device receives the release notification from the first device, where the release notification includes the group indication information.

24. The method according to claim 21 or 22, wherein the session management function device obtains the stateless indication information, and comprises:

the session management function device receives a session establishment request from the first device, wherein the session establishment request comprises the stateless indication information; alternatively, the first and second electrodes may be,

the session management function device receives the release notification from the first device, wherein the release notification includes the stateless indication information; alternatively, the first and second electrodes may be,

and the session management function equipment acquires the stateless indication information from local configuration information.

25. The method according to claim 21 or 22, wherein the group indication information is a group identity ID of a group to which the first device belongs; correspondingly, the method further comprises the following steps:

and if the session management function device needs to send downlink messages and determines that the binding between the signaling connection corresponding to the UE and the first interface is released, the session management function device determines a second device serving the UE according to the group ID.

26. An apparatus for message transmission, comprising: the device comprises an acquisition module and a sending module;

the acquiring module is configured to acquire stateless indication information and group indication information of a group to which a first device belongs, where the stateless indication information is used to indicate that a second device serving the UE is selected according to the group indication information when a downlink message needs to be sent after it is determined that a signaling connection corresponding to the user equipment UE is bound and released with a first interface, the first device is a device serving the UE before the binding between the signaling connection and the first interface is released, and the first interface is an interface between a radio access network RAN and the first device;

the sending module is configured to send the downlink message to a second device when the obtaining module receives the release notification from the first device and the downlink message needs to be sent, where the second device is a device serving the UE and determined according to the group indication information.

27. The apparatus of claim 26, further comprising: a determination module;

the determining module is configured to determine a binding release between a signaling connection corresponding to the UE and the first interface.

28. The apparatus of claim 26 or 27,

the obtaining module is specifically configured to receive a session establishment request from the first device, where the session establishment request includes the group indication information; or receiving the release notification from the first device, where the release notification includes the group indication information.

29. The apparatus of claim 26 or 27,

the obtaining module is specifically configured to receive a session establishment request from the first device, where the session establishment request includes the stateless indication information; or, receiving the release notification from the first device, where the release notification includes the stateless indication information; or, obtaining the stateless indication information from local configuration information.

30. The apparatus according to claim 26 or 27, wherein the group indication information is a group identity ID of a group to which the first device belongs;

the determining module is specifically configured to determine, if the sending module needs to send a downlink message and the determining module determines that the binding between the signaling connection corresponding to the UE and the first interface is released, the second device serving the UE according to the group ID.