A method for checking and processing PDU session duplication in AMF

Abstract

The present invention relates to an implementation method for checking and processing the repetitiveness of PDU sessions in AMF. After receiving a PDU session establishment request initiated by a UE, the AMF extracts valid information in the request and compares it with the PDU session information of the UE in a permanent storage device. It first checks whether the session identifier PSI carried in the request already exists in the permanent storage device. If so, it is considered that the PDU session establishment request initiated by the UE is a repetitive request; otherwise, the network slice, data network name and PDU session type PST carried in the request are checked to identify whether there is a matching existing PDU session. On the basis of checking PSI, matching processing of information such as Old PSI is added, so that the AMF can identify repetitive session establishment requests in advance and trigger the release of the PDU session in time, so as to ensure the synchronization and accuracy of PDU session information in complex scenarios within the 5G core network.

Description

Technical Field

[0001] The present invention relates to a method for implementing PDU session repeatability checking and processing in AMF. Background Art

[0002] After the user equipment (UE) initiates user registration with the 5G core network (5GC), in order to realize the data transmission function, the UE needs to initiate a protocol data unit (PDU) session establishment request to the session management function (SMF) via the access and mobility management function (AMF), and connect to the data network (DN) through the user plane function (UPF) anchor point to transmit data with it.

[0003] In the 5G network, in order to meet the data transmission requirements, a UE can request to establish multiple PDU sessions at the same time. Different PDU sessions are distinguished by the PDU session identifier (PSI). When the PSI of two PDU sessions is the same, it is considered that the PDU session has been created repeatedly. The AMF should first trigger the release of the original PDU session and then create a new PDU session to ensure the uniqueness of the PSI in the 5G core network.

[0004] In actual applications, the UE will use different PSIs to request the creation of multiple PDU sessions from the same data network. Some of these are business requirements, such as the UE creating both IPv4 and IPv6 PDU sessions to the IMS data network at the same time; while some are redundant sessions. For redundant sessions, the AMF cannot identify them immediately by checking the PSI alone. Summary of the invention

[0005] In view of the problems existing in the prior art, the purpose of the present invention is to provide a technical solution for implementing a method for checking and processing PDU session duplication in AMF.

[0006] The method for implementing PDU session duplication check and processing in AMF is characterized in that: after receiving the PDU session establishment request initiated by the UE, the AMF extracts the valid information in the request and compares it with the PDU session information of the UE in the permanent storage device, and first checks whether the session identifier PSI carried in the request already exists in the permanent storage device. If so, the PDU session establishment request initiated by the UE is considered to be a repetitive request; otherwise, the network slice S-NSSAI, data network name DNN and PDU session type PST carried in the request are checked to identify whether there is a matching existing PDU session.

[0007] The method for implementing PDU session repetitiveness check and processing in AMF is characterized in that: if it exists, then check whether the PDU session establishment request carries the indication of old PSI. If old PSI exists and is valid, the request is regarded as a scenario in which the UPF anchor point in the session and service continuity mode SSC mode 3 is changed, and this is excluded. In other cases, the PDU session establishment request initiated by the UE is considered to be a repetitive request; For non-repetitive requests, AMF directly forwards the PDU session establishment request to SMF. After the PDU session is successfully established, AMF saves the PDU session information to a permanent storage device for the repetitiveness check of subsequent PDU sessions of the UE. For requests determined to be repetitive, the PDU session information on the permanent storage device in AMF is regarded as redundant information, and the corresponding created PDU session is also regarded as a redundant session; AMF first interacts with SMF to release the redundant session and delete the redundant information, and then forwards the UE's PDU session establishment request to SMF, which is consistent with the processing of non-repetitive requests.

[0008] The method for implementing PDU session repeatability check and processing in AMF is characterized in that the implementation method for repeatability check and processing is divided into two stages: The first stage is the preparation stage: all PDU session-related processing before AMF processes the current PDU session establishment request of UE belongs to the preparation stage; in the preparation stage, AMF shall save the information of all established PDU sessions to a permanent storage device; during the PDU session establishment process, AMF saves the parameters in the PDU session establishment request initiated by UE to a temporary cache, and then uses and maintains these PDU session establishment parameters when interacting with SMF. When the PDU session establishment process ends and the PDU session is successfully established, AMF converts the PDU session establishment parameters into PDU session information and saves it to a permanent storage device, and clears the temporary cache at the same time. AMF will use the PDU session information saved in the preparation stage when processing subsequent PDU session establishment requests from UE; The second stage is the execution stage: After AMF obtains the parameters from the PDU session establishment request initiated by the UE, it matches and analyzes it with the PDU session information in the permanent storage device. If the match is successful, AMF considers that the PDU session establishment request initiated by the UE is a repetitive request, and there is redundant information on the permanent storage device. The corresponding created PDU session is also regarded as a redundant session. AMF needs to release the redundant session and delete the redundant information before executing the new PDU session establishment process; otherwise, it directly enters the PDU session establishment process.

[0009] The method for implementing PDU session repeatability check and processing in AMF is characterized in that the execution phase includes 4 steps: Step 1: Get the parameters in the PDU session establishment request After receiving the PDU session establishment request initiated by the UE, the AMF decodes the request message and saves the key information into the temporary cache for service processing. These key parameters include AMF-UE-NGAP-ID, PSI, Old PSI, PST, SSC mode, S-NSSAI and DNN. Step 2: PDU session duplication check AMF obtains all the established PDU session information of the UE from the permanent storage device according to the AMF-UE-NGAP-ID parameter obtained in step 1, and forms a PDU session information list, where each member in the list includes but is not limited to PSI, PST, S-NSSAI and DNN information; AMF matches and analyzes the parameters obtained in step 1 with the information contained in each member in the PDU session information list in turn; after matching and analysis, AMF divides the PDU session establishment request initiated by the UE into two categories: repetitive PDU session establishment requests and non-repetitive PDU session establishment requests. AMF performs different steps according to the type of PDU session establishment request, and executes step 3 for repetitive PDU session establishment requests and step 4 for non-repetitive PDU session establishment requests; Step 3: Handling repetitive PDU session establishment requests When the AMF identifies that the PDU session establishment request initiated by the UE is a repetitive session establishment request, the PDU session information on the permanent storage device in the AMF is regarded as redundant information, and the corresponding created PDU session is also regarded as a redundant session; Step 4: Processing non-repetitive PDU session establishment requests AMF forwards the UE's PDU session establishment request to SMF. After the PDU session establishment process is completed and the PDU session establishment is confirmed to be successful, AMF converts the PDU session establishment parameters into PDU session information and saves it on a permanent storage device. At the same time, it clears the information in the cache. The information stored on the permanent storage device is used for the repeatability check of the UE's subsequent PDU sessions.

[0010] The method for implementing PDU session duplication check and processing in AMF is characterized in that the AMF-UE-NGAP-ID is a unique identifier assigned by AMF to UE, and is the primary information for matching with the PDU session information on the permanent storage device. If the AMF-UE-NGAP-ID in the session establishment request is consistent with the information stored on the permanent storage device, it is considered that the UE has valid PDU session information; PSI is the unique identifier assigned by UE to PDU session and is the main information for comparison with PDU session information on permanent storage device. If the PSI of two PDU session information is the same, it can be confirmed that the two sessions are duplicate sessions and no other information needs to be compared; Old PSI, PST, SSC mode, S-NSSAI and DNN are secondary information compared with the PDU session information on the permanent storage device. If the primary information fails to match, all secondary information needs to be matched and analyzed.

[0011] The method for implementing PDU session repeatability check and processing in AMF is characterized in that the matching analysis step in step 2 is as follows: Step 2.1: Analyze whether the PSI parameter obtained in step 1 is the same as the PSI of each member in the PDU session information list. If there are identical members, the new PDU session establishment request is considered to be a repeated PDU session establishment request, and the matching analysis from step 2.2 to step 2.5 is no longer performed; Step 2.2: Analyze whether the DNN parameters obtained in step 1 are identical to the DNN of each member in the PDU session information list. If there are no identical members, the new PDU session establishment request is considered to be a non-repetitive PDU session establishment request, and the matching analysis of steps 2.3 to 2.5 is no longer performed. All identical members are formed into a new list to be matched; Step 2.3: Analyze whether the S-NSSAI parameter obtained in step 1 is identical to the S-NSSAI of each member in the new list to be matched. If there is no identical member, the new PDU session establishment request is considered to be a non-repetitive PDU session establishment request, and the matching analysis from step 2.4 to step 2.5 is no longer performed; Step 2.4: Analyze whether the PST obtained in step 1 is the same as the PST of the member matched in step 2.3. If the two are not the same, it is a PDU session type negotiation scenario, that is, a non-repetitive PDU session establishment request, and the matching analysis in step 2.5 is no longer performed; Step 2.5: If valid Old PSI information is obtained in step 1, the PDU session establishment request is regarded as a change in the UPF session anchor point in the session and service continuity mode SSC mode 3, that is, a non-repetitive PDU session establishment request; otherwise, the new PDU session establishment request is considered to be a repetitive PDU session establishment request.

[0012] The method for implementing PDU session repeatability check and processing in AMF is characterized in that the AMF performs the following steps: Step 3.1: Send a request to release the PDU session to SMF according to the redundant session information; Step 3.2: Start the timer and wait for the SMF to reply with a response to release the PDU session; Step 3.3: After receiving the response of releasing the PDU session from SMF, turn off the timer, delete the redundant information in the permanent storage device, and go to step 4; Step 3.4: When the timer times out and no response is received from the SMF to release the PDU session, the redundant information in the permanent storage device is deleted and the process goes to step 4.

[0013] The present invention provides an implementation method for checking and processing PDU session repetitiveness in AMF. After receiving the PDU session establishment request initiated by UE, AMF adds matching processing of Old PSI, PST, SSC mode, S-NSSAI (SST and SD) and DNN information on the basis of checking PSI, so that AMF can identify repetitive session establishment requests as early as possible and trigger PDU session release in time, so as to ensure the synchronization and accuracy of PDU session information in complex scenarios in the 5G core network. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 Create a request information duplication check and processing flow chart for PDU session. DETAILED DESCRIPTION

[0015] The present invention will be further described below in conjunction with the accompanying drawings: The present invention proposes an implementation method for checking and processing the PDU session duplication in AMF. After receiving the PDU session establishment request initiated by the UE, the AMF extracts the valid information in the request and compares it with the PDU session information of the UE in the permanent storage device. First, it checks whether the session identifier (PSI) carried in the request already exists in the permanent storage device. If so, the PDU session establishment request initiated by the UE is considered to be a duplicate request; otherwise, the network slice (S-NSSAI), data network name (DNN) and PDU session type (PST) carried in the request are checked to identify whether there is a matching existing PDU session. If so, it is checked whether the PDU session establishment request carries an indication of the old PSI. If the old PSI exists and is valid, the request is regarded as a scenario in which the UPF anchor point in the session and service continuity mode 3 (SSC mode 3) changes, and this is excluded. In other cases, the PDU session establishment request initiated by the UE is considered to be a duplicate request. For non-repetitive requests, AMF directly forwards the PDU session establishment request to SMF. After the PDU session is successfully established, AMF saves the PDU session information to a permanent storage device for subsequent PDU session repeatability checks of the UE. For requests that are determined to be repetitive, the PDU session information on the permanent storage device in AMF is regarded as redundant information, and the corresponding created PDU session is also regarded as a redundant session; AMF first interacts with SMF to release the redundant session and delete the redundant information, and then forwards the UE's PDU session establishment request to SMF, which is consistent with the processing of non-repetitive requests.

[0016] The implementation method of checking and processing PDU session duplication in AMF described in the present invention is divided into two stages, namely the preparation stage and the execution stage, which are described in stages below.

[0017] The first stage is the preparation stage. The preparation stage is a logical concept, which means that all PDU session-related processing before AMF processes the UE's current PDU session establishment request belongs to the preparation stage. In the preparation stage, AMF will save the information of all established PDU sessions to a permanent storage device. During the PDU session establishment process, AMF saves the parameters in the PDU session establishment request initiated by the UE to a temporary cache, and then uses and maintains these PDU session establishment parameters when interacting with SMF. When the PDU session establishment process ends and the PDU session is successfully established, AMF converts the PDU session establishment parameters into PDU session information and saves it to a permanent storage device, and clears the temporary cache at the same time. AMF will use the PDU session information saved in the preparation stage when processing subsequent PDU session establishment requests from the UE.

[0018] The second stage is the execution stage. The execution stage includes 4 steps. After AMF obtains the parameters from the PDU session establishment request initiated by the UE, it matches and analyzes it with the PDU session information in the permanent storage device. If the match is successful, AMF considers that the PDU session establishment request initiated by the UE is a repetitive request, and there is redundant information on the permanent storage device. The corresponding created PDU session is also regarded as a redundant session. AMF needs to release the redundant session and delete the redundant information before executing the new PDU session establishment process; otherwise, it directly enters the PDU session establishment process. Figure 1 As shown, the following steps are described in detail: Step 1: Get the parameters in the PDU session establishment request After receiving the PDU session establishment request initiated by the UE, the AMF decodes the request message and saves the key information into the temporary buffer for service processing. These key parameters include AMF-UE-NGAP-ID, PSI, Old PSI, PST, SSC mode, S-NSSAI (SST and SD) and DNN; AMF-UE-NGAP-ID is the unique identifier assigned by AMF to UE. It is the primary information to match with the PDU session information on the permanent storage device. If the AMF-UE-NGAP-ID in the session establishment request is consistent with the information stored on the permanent storage device, it is considered that the UE has valid PDU session information. PSI is the unique identifier assigned by UE to PDU session. It is the main information to compare with the PDU session information on the permanent storage device. If the PSI of two PDU session information is the same, it can be confirmed that the two sessions are duplicate sessions, and there is no need to compare other information; Old PSI, PST, SSC mode, S-NSSAI (SST and SD) and DNN are the secondary information to compare with the PDU session information on the permanent storage device. If the primary information fails to match, all secondary information needs to be matched and analyzed.

[0019] Step 2: PDU session duplication check AMF matches and obtains all the established PDU session information of the UE from the permanent storage device according to the AMF-UE-NGAP-ID parameter obtained in step 1, and forms a PDU session information list. Each member in the list includes but is not limited to PSI, PST, S-NSSAI (SST and SD) and DNN information. The parameters obtained in step 1 are matched and analyzed with the information contained in each member in the PDU session information list in turn. The steps are as follows: Step 2.1: Analyze whether the PSI parameter obtained in step 1 is the same as the PSI of each member in the PDU session information list. If there are identical members, the new PDU session establishment request is considered to be a repeated PDU session establishment request, and the matching analysis from step 2.2 to step 2.5 is no longer performed; Step 2.2: Analyze whether the DNN parameters obtained in step 1 are identical to the DNN of each member in the PDU session information list. If there are no identical members, the new PDU session establishment request is considered to be a non-repetitive PDU session establishment request, and the matching analysis of steps 2.3 to 2.5 is no longer performed. All identical members form a new list to be matched; Step 2.3: Analyze whether the S-NSSAI parameter obtained in step 1 is identical to the S-NSSAI of each member in the new list to be matched. If there is no identical member, the new PDU session establishment request is considered to be a non-repetitive PDU session establishment request, and the matching analysis from step 2.4 to step 2.5 is no longer performed; Step 2.4: Analyze whether the PST obtained in step 1 is the same as the PST of the member matched in step 2.3. If the two are not the same, it is a PDU session type negotiation scenario, that is, a non-repetitive PDU session establishment request, and the matching analysis in step 2.5 is no longer performed; Step 2.5: If valid Old PSI information is obtained in step 1, the PDU session establishment request is regarded as a change in the UPF session anchor point in the session and service continuity mode 3 (SSC mode 3), that is, a non-repeated PDU session establishment request; otherwise, the new PDU session establishment request is regarded as a repetitive PDU session establishment request; After the above matching analysis, AMF divides the PDU session establishment request initiated by the UE into two categories: repetitive PDU session establishment request and non-repetitive PDU session establishment request. AMF performs different steps according to the type of PDU session establishment request, performing step 3 for repetitive PDU session establishment request and step 4 for non-repetitive PDU session establishment request.

[0020] Step 3: Handling repetitive PDU session establishment requests When the AMF identifies that the PDU session establishment request initiated by the UE is a repetitive session establishment request, the PDU session information on the permanent storage device in the AMF is regarded as redundant information, and the corresponding created PDU session is also regarded as a redundant session. The AMF performs the following steps: Step 3.1: Send a request to release the PDU session to SMF according to the redundant session information; Step 3.2: Start the timer and wait for the SMF to reply with a response to release the PDU session; Step 3.3: After receiving the response of releasing the PDU session from SMF, turn off the timer, delete the redundant information in the permanent storage device, and go to step 4; Step 3.4: When the timer times out and no response is received from the SMF to release the PDU session, the redundant information in the permanent storage device is deleted and the process goes to step 4.

[0021] Step 4: Process normal (non-repetitive) PDU session establishment requests AMF forwards the UE's PDU session establishment request to SMF. After the PDU session establishment process is completed and the PDU session establishment is confirmed to be successful, AMF converts the PDU session establishment parameters into PDU session information and saves it to the permanent storage device, while clearing the information in the cache. The information stored on the permanent storage device is used for the repeatability check of the UE's subsequent PDU sessions.

[0022] 5GC: 5G Core, the fifth generation mobile communication technology core network AMF: Access and Mobility Management Function, access and mobility management function SMF: Session Management Function UE:User Equipment IP: Internet Protocol IPv4: Internet Protocol Version 4 IPv6: Internet Protocol Version 6 SSC mode: Session and Service Continuity Mode, session and service continuity mode PDU: Protocol Data Unit PSI: PDU Session Id, PDU session identifier PST: PDU Session Type, PDU session type DNN: Data Network Name, data network name S-NSSAI: Single Network Slice Selection Assistance Information, single network slice selection assistance information SST: Slice / Service Type, network slice type or service type SD: Slice Differentiator, network slice segmentation identifier Old PSI: Source PDU session identifier.

Claims

1. A method for implementing PDU session duplication checking and processing in AMF, characterized by: After receiving the PDU session establishment request initiated by the UE, the AMF extracts the valid information in the request and compares it with the PDU session information of the UE in the permanent storage device. It first checks whether the session identifier PSI carried in the request already exists in the permanent storage device. If so, the PDU session establishment request initiated by the UE is considered to be a repetitive request; otherwise, the network slice S-NSSAI, data network name DNN and PDU session type PST carried in the request are checked to identify whether there is a matching existing PDU session.

2. According to claim 1, a method for implementing PDU session repeatability checking and processing in AMF is characterized in that: If it exists, check whether the PDU session establishment request carries the indication of the old PSI. If the old PSI exists and is valid, the request is regarded as a scenario in which the UPF anchor point in the session and service continuity mode SSC mode 3 has changed, and this is excluded. In other cases, the PDU session establishment request initiated by the UE is considered to be a repeated request; For non-repetitive requests, AMF directly forwards the PDU session establishment request to SMF. After the PDU session is successfully established, AMF saves the PDU session information to a permanent storage device for the repetitiveness check of subsequent PDU sessions of the UE. For requests determined to be repetitive, the PDU session information on the permanent storage device in AMF is regarded as redundant information, and the corresponding created PDU session is also regarded as a redundant session; AMF first interacts with SMF to release the redundant session and delete the redundant information, and then forwards the UE's PDU session establishment request to SMF, which is consistent with the processing of non-repetitive requests.

3. According to claim 1, a method for implementing PDU session repeatability checking and processing in AMF is characterized in that The implementation method of duplication checking and processing is divided into two stages: The first stage is the preparation stage: all PDU session-related processing before AMF processes the UE's current PDU session establishment request belongs to the preparation stage; During the preparation phase, AMF shall save the information of all established PDU sessions to a permanent storage device; During the PDU session establishment process, AMF saves the parameters in the PDU session establishment request initiated by the UE into a temporary cache, and then uses and maintains these PDU session establishment parameters when interacting with SMF. When the PDU session establishment process ends and the PDU session is successfully established, AMF converts the PDU session establishment parameters into PDU session information and saves it to a permanent storage device, and clears the temporary cache at the same time. AMF will use the PDU session information saved in the preparation phase when processing subsequent PDU session establishment requests from the UE; The second stage is the execution stage: After AMF obtains the parameters from the PDU session establishment request initiated by the UE, it matches and analyzes it with the PDU session information in the permanent storage device. If the match is successful, AMF considers that the PDU session establishment request initiated by the UE is a repetitive request, and there is redundant information on the permanent storage device. The corresponding created PDU session is also regarded as a redundant session. AMF needs to release the redundant session and delete the redundant information before executing the new PDU session establishment process; otherwise, it directly enters the PDU session establishment process.

4. According to claim 3, a method for implementing PDU session repeatability checking and processing in AMF is characterized in that The execution phase consists of 4 steps: Step 1: Get the parameters in the PDU session establishment request After receiving the PDU session establishment request initiated by the UE, the AMF decodes the request message and saves the key information into the temporary cache for service processing. These key parameters include AMF-UE-NGAP-ID, PSI, Old PSI, PST, SSC mode, S-NSSAI and DNN. Step 2: PDU session duplication check The AMF obtains all established PDU session information of the UE from the permanent storage device according to the AMF-UE-NGAP-ID parameter obtained in step 1, and forms a PDU session information list. Each member in the list includes but is not limited to PSI, PST, S-NSSAI and DNN information; The parameters obtained in step 1 are matched and analyzed with the information contained in each member in the PDU session information list in turn; after matching and analysis, AMF divides the PDU session establishment request initiated by the UE into two categories: repetitive PDU session establishment requests and non-repetitive PDU session establishment requests. AMF performs different steps according to the type of PDU session establishment request. For repetitive PDU session establishment requests, step 3 is performed, and for non-repetitive PDU session establishment requests, step 4 is performed; Step 3: Handling repetitive PDU session establishment requests When the AMF identifies that the PDU session establishment request initiated by the UE is a repetitive session establishment request, the PDU session information on the permanent storage device in the AMF is regarded as redundant information, and the corresponding created PDU session is also regarded as a redundant session; Step 4: Processing non-repetitive PDU session establishment requests AMF forwards the UE's PDU session establishment request to SMF. After the PDU session establishment process is completed and the PDU session establishment is confirmed to be successful, AMF converts the PDU session establishment parameters into PDU session information and saves it on a permanent storage device. At the same time, it clears the information in the cache. The information stored on the permanent storage device is used for the repeatability check of the UE's subsequent PDU sessions.

5. According to claim 4, a method for implementing PDU session repeatability checking and processing in AMF is characterized in that The AMF-UE-NGAP-ID is a unique identifier assigned by the AMF to the UE and is the primary information for matching the PDU session information on the permanent storage device. If the AMF-UE-NGAP-ID in the session establishment request is consistent with the information stored on the permanent storage device, it is considered that the UE has valid PDU session information; PSI is the unique identifier assigned by UE to PDU session and is the main information for comparison with PDU session information on permanent storage device. If the PSI of two PDU session information is the same, it can be confirmed that the two sessions are duplicate sessions and no other information needs to be compared; Old PSI, PST, SSC mode, S-NSSAI and DNN are secondary information compared with the PDU session information on the permanent storage device. If the primary information fails to match, all secondary information needs to be matched and analyzed.

6. A method for implementing PDU session repeatability checking and processing in AMF according to claim 4, characterized in that The matching analysis steps in step 2 are as follows: Step 2.1: Analyze whether the PSI parameter obtained in step 1 is the same as the PSI of each member in the PDU session information list. If there are identical members, the new PDU session establishment request is considered to be a repeated PDU session establishment request, and the matching analysis from step 2.2 to step 2.5 is no longer performed; Step 2.2: Analyze whether the DNN parameters obtained in step 1 are identical to the DNN of each member in the PDU session information list. If there are no identical members, the new PDU session establishment request is considered to be a non-repetitive PDU session establishment request, and the matching analysis of steps 2.3 to 2.5 is no longer performed. All identical members are formed into a new list to be matched; Step 2.3: Analyze whether the S-NSSAI parameter obtained in step 1 is identical to the S-NSSAI of each member in the new list to be matched. If there is no identical member, the new PDU session establishment request is considered to be a non-repetitive PDU session establishment request, and the matching analysis from step 2.4 to step 2.5 is no longer performed; Step 2.4: Analyze whether the PST obtained in step 1 is the same as the PST of the member matched in step 2.

3. If the two are not the same, it is a PDU session type negotiation scenario, that is, a non-repetitive PDU session establishment request, and the matching analysis in step 2.5 is no longer performed; Step 2.5: If valid Old PSI information is obtained in step 1, the PDU session establishment request is regarded as a change in the UPF session anchor point in the session and service continuity mode SSC mode 3, that is, a non-repetitive PDU session establishment request; otherwise, the new PDU session establishment request is considered to be a repetitive PDU session establishment request.

7. A method for implementing PDU session repeatability checking and processing in AMF according to claim 4, characterized in that The AMF performs the following steps: Step 3.1: Send a request to release the PDU session to SMF according to the redundant session information; Step 3.2: Start the timer and wait for the SMF to reply with a response to release the PDU session; Step 3.3: After receiving the response of releasing the PDU session from SMF, turn off the timer, delete the redundant information in the permanent storage device, and go to step 4; Step 3.4: When the timer times out and no response is received from the SMF to release the PDU session, the redundant information in the permanent storage device is deleted and the process goes to step 4.

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