A method for implementing network function discovery of AMF in lightweight 5GC

Abstract

The present invention relates to a method for implementing network function discovery of AMF in a lightweight 5GC. It is characterized in that it includes three stages, namely, a preparation stage, an execution stage and a maintenance stage. The preparation stage of network function discovery in AMF is executed after the AMF is started; after the AMF is started, a user device may request a network service at any time, thereby triggering the execution stage of network function discovery; in the maintenance stage, in order for AMF to manage the local cache space to ensure the accuracy of the data, it can be used as part of the execution stage or triggered by the NF status notification. The present invention adds a local cache mechanism in AMF to cache the results of network function discovery and the results of network function status notification. When processing business, the local cache data is used first, so that the network function discovery service can be provided quickly, accurately and effectively, and the interaction between AMF and NRF can be reduced.

Description

Technical Field

[0001] The present invention relates to a method for realizing network function discovery of AMF in lightweight 5GC. Background Art

[0002] Lightweight 5GC, also known as industry 5GC, is mainly aimed at industry applications. It cuts unnecessary network functions in 5GC, retains only necessary network functions, selectively adds optional network functions according to industry needs, and combines small and closely related network functions to achieve the goal of overall network lightweighting. Lightweight 5GC focuses on flexible orchestration, customized development, and rapid deployment, weakening the impact of network slicing on each NF in lightweight 5GC.

[0003] 5GC adopts a service-oriented architecture, and all network function instances are obtained from NRF through network function discovery. In lightweight 5GC, the structure is relatively simple. If the method of interacting with NRF to obtain network functions is adopted for each business, it will inevitably cause unnecessary waste of resources. Therefore, it is necessary to consider the implementation method of simplified network function discovery. Summary of the invention

[0004] 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 network function discovery of AMF in lightweight 5GC.

[0005] The method for implementing network function discovery of AMF in a lightweight 5GC is characterized by comprising three stages, namely, a preparation stage, an execution stage and a maintenance stage;

[0006] S1: Preparation phase. The preparation phase of network function discovery in AMF is executed after AMF startup is completed. The preparation phase includes local cache initialization, obtaining NRF configuration, service registration with NRF, and NF status subscription with NRF.

[0007] S1.1, local cache initialization, AMF's local cache is used to store network function information discovered from NRF, network function types include AUSF, UDM and SMF; local cache means that AMF is used to store network function information discovered from NRF, using a one-dimensional pointer array, each type of network function corresponds to a linked list, and network function instances are stored in a dynamic space, which has better scalability; local cache initialization is to set all pointer arrays to null pointers;

[0008] S1.1.1, the information that needs to be stored in the local cache includes: the instance identifier of the network function, the instance type, the instance status, the service IP address of the instance, the service port number of the instance, the life span of the instance, the priority of the instance, the weight of the instance, the dynamic load of the instance, and the creation time of the instance;

[0009] S1.2, obtain NRF configuration. AMF reads NRF configuration information from the local configuration file or obtains it from the network management. The NRF configuration information includes the service IP and service port of NRF. AMF saves the obtained NRF configuration information to the memory.

[0010] S1.3, register the service with NRF. AMF initiates service registration with NRF according to the NRF configuration information obtained in S1.2. If the registration fails, AMF needs to start the periodic timer to resend the service registration to NRF regularly until the service registration is successful.

[0011] S1.3.1, AMF sends heartbeats to NRF regularly according to the heartbeat interval indicated in the service registration response to indicate to NRF that the AMF is available;

[0012] S1.4, subscribe to the NF status to NRF, and only distinguish the network function type, that is, the subscription request message only carries the network function type of sending the subscription request, the subscribed network function type in the subscription condition, and the destination service address of the NF status notification;

[0013] S1.4.1, the startup order of each network function in lightweight 5GC is uncertain. AMF may not receive the NF status notification message immediately after successfully completing the subscription process;

[0014] S2: Execution phase. After AMF is started, user devices may request network services at any time, which will trigger the execution phase of network function discovery. The execution phase includes retrieving local cache, discovering network functions to NRF, and updating local cache space.

[0015] S2.1, retrieve local cache; AMF receives the service request from the user device, first searches the local cache to find the network function instance that meets the conditions; the conditions include: 1) the instance type is the same as the network function type requested by AMF; 2) the instance status is registered; 3) the instance life cycle has not timed out;

[0016] S2.1.1: The instance lifecycle in the above condition 3) has not timed out means that the difference between the current time and the time when the instance was created is less than the instance lifecycle;

[0017] S2.1.2, find the network function instance that meets the conditions in S2.1, form a candidate list of all the network function instances that meet the conditions, select the first instance with the highest priority, the largest weight, and the smallest load from the candidate list and request service from it, and do not execute the subsequent steps;

[0018] S2.1.3: If no network function instance that meets the conditions is found in S2.1, continue to execute S2.2;

[0019] S2.2, perform network function discovery to NRF; AMF constructs a network function discovery request, and the discovery condition in the request only sets the network function type to the network function to be discovered; after AMF sends the network function discovery request to NRF, it expects to receive a discovery response message from NRF;

[0020] S2.2.1, if the AMF does not receive a discovery response from the NRF, it directly replies to the user equipment that the service request has been rejected, and no further subsequent steps are performed;

[0021] S2.2.2, AMF receives the discovery response from NRF, then proceeds to S2.3;

[0022] S2.3, update the local cache space; AMF receives the discovery response message from NRF and processes the discovery response message according to the following logic;

[0023] S2.3.1, if it is a failed response or a successful response that does not carry valid network function instance information, the execution process ends abnormally;

[0024] S2.3.2, if it is a successful response carrying valid network function instance information and the same instance identifier is in the local cache, the new information is updated to the local cache unit;

[0025] S2.3.3, if it is a successful response with valid network function instance information but there is no identical instance identifier in the local cache, then the information is inserted into the end of the cache linked list corresponding to the network function type, and the createdtime tick is set to the current time;

[0026] S2.3.4, if the execution process ends abnormally, the AMF replies to the user equipment with a response that the service request is rejected, otherwise the AMF continues to provide access services to the user equipment;

[0027] S3, maintenance phase, in order to allow AMF to manage local cache space to ensure data accuracy, which can be part of the execution phase or triggered by NF status notification;

[0028] S3.1, when retrieving the local cache in the execution phase, that is, when condition 3) in S2.1 is not satisfied and the instance life cycle has not timed out, the cache unit is deleted from the linked list, so that the local cache space can be updated in real time;

[0029] S3.2, in lightweight 5GC, the real-time status of each network function is recorded in NRF and NF status notification is sent to the subscriber when the status change is detected. AMF may receive such notification message at any time after completing the preparation phase;

[0030] S3.3, the maintenance phase triggered by NF status notification includes processing NF status notification requests and updating the locally cached data.

[0031] The method for implementing network function discovery of AMF in lightweight 5GC is characterized in that the specific operation steps of the maintenance phase process triggered by NF status notification in S3.3 are as follows:

[0032] S3.3.1, upon receiving the NF status notification request, the AMF immediately replies a successful response to the NRF, and then extracts the network function instance information in the request message;

[0033] S3.3.2, if the instance identifier in the request is different from all instance identifiers in the local cache space, insert the instance information into the tail of the cache linked list corresponding to the network function type and set the creation time of the instance to the current time;

[0034] S3.3.3, if the instance identifier in the request is the same as an instance identifier in the local cache space, update the cache data, and at the same time update the instance life cycle and instance creation time, and set the instance creation time to the current time.

[0035] The method for implementing network function discovery of AMF in lightweight 5GC is characterized in that: in the AMF of lightweight 5GC, AMF implements access and mobility management functions, and provides identity authentication, service authorization and mobility management services for user equipment to access the 5G network; AMF provides these services on the premise that it can obtain corresponding services from other NFs, including obtaining user authentication information from the authentication server function, obtaining user contract data from unified data management, and obtaining PDU session management services from the session management function.

[0036] The present invention locally caches the results of network function discovery and network function status notification, and first uses the locally cached data when processing services. This can not only reduce the complexity of network function discovery implementation in AMF, but also reduce the number of signaling interactions between AMF and NRF, thereby improving the efficiency of service processing in lightweight 5GC. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 This is a flow chart of the preparation phase of network function discovery of the present invention;

[0038] Figure 2Flowchart of the execution phase of network function discovery;

[0039] Figure 3 This is a flowchart of the processing of NF status notification message. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with the accompanying drawings:

[0041] In lightweight 5GC, the access and mobility management function (AMF) provides identity authentication, service authorization and mobility management services for user equipment (UE) to access the 5G network. The premise for AMF to provide these services is that it can obtain corresponding services from other NFs, such as: obtaining user authentication information from the authentication server function (AUSF), obtaining user subscription data from the unified data management (UDM), and obtaining PDU session management services from the session management function (SMF). It can be seen that the network functions that AMF needs to discover from NRF are AUSF, UDM and SMF.

[0042] In the present invention, the network function discovery in AMF is divided into three stages, namely, the preparation stage, the execution stage and the maintenance stage, which will be described one by one in combination with different stages below.

[0043] The preparation phase of network function discovery in AMF is executed after AMF startup is completed, including local cache initialization, obtaining NRF, service registration with NRF, and NF status subscription with NRF. Figure 1 The process of the network function discovery preparation phase is described. The steps are as follows:

[0044] Step 1: Initialize local cache

[0045] The local cache of AMF is used to store the network function information discovered from NRF. The network function types include AUSF, UDM and SMF. The local cache of AMF uses a one-dimensional pointer array and each unit stores the head pointer of the linked list of network function instances of different types. The benefit of this implementation is that the cache space can be dynamically expanded. The local cache initialization is to set all the pointer arrays to null pointers.

[0046] The local cache information is shown in Table 1, including instance id, nf type, nf status, served ip, served port, expires, priority, capacity, load, and created time tick; instanceid is the instance identifier, string type, length of 1 to 64 bytes, used to distinguish different network function instances; nf type is the instance type, integer, value range is 1 to 255, 2 represents UDM, 3 represents AMF, 3 represents SMF, 4 represents AUSF; nfstatus is the instance status, integer, value range is 0 to 255, 0 represents unavailable, 1 represents registered, 2 represents suspended; served ip represents the service IP address of the instance, string type of dotted IPv4 address; served port is the service port number of the instance, integer, ranging from 1 to 65535; expires is the life span of the instance, integer, ranging from 1 to 4294967295; priority is the priority of the instance, integer, ranging from 0 to 65535, and the smaller the value, the higher the priority; capacity is the weight of this instance compared with other instances of the same type, integer, ranging from 0 to 65535, and the larger the value, the greater the weight; load is the dynamic load of the instance, ranging from 0 to 100, and the larger the value, the higher the load; createdtime tick is the creation time of the instance, integer, ranging from 1 to 4294967295, indicating the timestamp when the instance is inserted into the local cache list.

[0047] Table 1 Network function instance information parameters

[0048]

[0049] Step 2: Get the nRF Configuration

[0050] AMF reads the NRF configuration information from the local configuration file or obtains it from the network management. The NRF configuration information includes the service IP and service port of NRF. If AMF does not obtain the NRF configuration information from the local configuration file or from the network management, steps 3 and 4 will not be executed. Otherwise, AMF saves the obtained NRF configuration information to the memory.

[0051] Step 3: Register the service with NRF

[0052] AMF initiates service registration to NRF according to the NRF configuration information obtained in step 2. If the registration fails, AMF needs to start a periodic timer to resend the service registration to NRF until the service registration is successful; after that, AMF regularly sends heartbeats to NRF according to the heartbeat interval indicated in the service registration response to indicate to NRF that the AMF is available.

[0053] Step 4: Subscribe to NRF for NF status

[0054] In the present invention, the subscription of AMF to NRF only distinguishes the network function type, that is, the subscription request message carries request nf type, subscribe condition, and notification uri, as shown in Table 2. Among them, request nf type is used to indicate the type of network function sending the subscription request, integer, with a value range of 1 to 65535, and 3 represents AMF; subscribe condition is used to indicate the subscription condition, which is a composite type and contains the subparameter nf type, which is used to indicate the subscribed network function type, integer, with a value range of 1 to 65535, 2 represents UDM, 3 represents AMF, 4 represents SMF, and 5 represents AUSF; notification uri indicates the destination service address of the NF status notification message, and the value is a string type in URI format.

[0055] Table 2 Subscription request message parameters

[0056]

[0057] Due to the uncertainty of the startup order of each network function, AMF may not receive the NF status notification message immediately after successfully completing the subscription process.

[0058] After the AMF is started, user equipment may request network services at any time, which in turn triggers the execution phase of network function discovery. Figure 2 The execution phase of network function discovery is described, including retrieving the local cache, making network function discovery to NRF, and updating the local cache space. The specific steps are as follows.

[0059] Step 1: Retrieve the local cache

[0060] When AMF receives a service request from a user device (for example, a registration request or a PDU session establishment request), it first searches the local cache to find a network function instance that meets the following conditions: 1) The instance type is the same as the network function type requested by AMF; 2) The instance status is "registered"; 3) The instance life cycle has not timed out. The instance life cycle has not timed out means that the difference between the current time and the time when the instance was created is less than the instance life cycle. If there is no network function instance that meets all three conditions in the local cache, continue to step 2. Otherwise, all instances that meet the conditions are combined into a candidate list, and the first instance with the highest priority, the largest weight, and the smallest load is selected from the candidate list and service is requested from it, and no subsequent steps are performed.

[0061] Step 2: Discover network functions to NRF

[0062] AMF constructs a network function discovery request. Like the NF status subscription request, the discovery condition of the network function discovery request only sets the network function type, that is, nf type is set to the network function to be discovered. After AMF sends a network function discovery request to NRF, it expects to receive a discovery response message from NRF. When AMF receives the discovery response from NRF, it proceeds to step 3; otherwise, AMF replies to the user device with a response that the service request is rejected, and no subsequent steps are performed.

[0063] Step 3: Update the local cache space

[0064] AMF receives the discovery response message from NRF and processes the discovery response message according to the following logic: if it is a failed response or a successful response without valid network function instance information, the execution process ends abnormally; if it is a successful response with valid network function instance information and the same instance identifier is in the local cache, the new information is updated to the local cache unit; if it is a successful response with valid network function instance information but there is no same instance identifier in the local cache, the information is inserted into the end of the cache linked list corresponding to the network function type, and the created time tick is set to the current time. When the execution process ends abnormally, AMF replies to the user device with a response that the service request is rejected, otherwise AMF continues to provide access services to the user device.

[0065] The purpose of the maintenance phase is for AMF to manage the local cache space to ensure data accuracy, which can be part of the execution phase or triggered by NF status notification. When retrieving the local cache in the execution phase, if condition 3 in step 1, that is, "the instance life cycle has not timed out", is not met, the cache unit is deleted from the linked list, so that the local cache space can be updated in real time.

[0066] In lightweight 5GC, NRF stores the real-time status of each network function and sends NF status notifications to subscribers when it senses a status change. AMF may receive such notifications at any time after completing the preparation phase. The maintenance phase process triggered by NF status notifications is as follows: Figure 3 The specific steps are as follows:

[0067] Step 1: Processing NF status notification request

[0068] After receiving the NF status notification request, the AMF immediately replies a successful response to the NRF, and then extracts the network function instance information in the request message.

[0069] Step 2: Perform different processing based on whether there is a network function instance in the local cache. If the instance identifier in the request is different from all instance identifiers in the local cache space, execute step 2.1; otherwise, execute step 2.2;

[0070] Step 2.1: Insert the instance information into the tail of the cache linked list corresponding to the network function type and set the created time tick to the current time;

[0071] Step 2.2: Update the cells with the same instance ID in the cache, and update the expires and created time ticks at the same time, setting the created time tick to the current time.

[0072] The present invention adds a local cache mechanism in AMF to cache the results of network function discovery and network function status notification. When processing services, the local cache data is used first, so that the network function discovery service can be provided quickly, accurately and effectively, and the interaction between AMF and NRF can be reduced. When optional network functions are added to lightweight 5GC, such as NSSF, PCF, etc., AMF can still use this method to realize network function discovery.

[0073] Explanation of terms

[0074] 5GC: 5G Core, the fifth generation mobile communication technology core network

[0075] AMF: Access and Mobility Management Function, access and mobility management function

[0076] AUSF: Authentication Server Function, authentication server function

[0077] IP: Internet Protocol

[0078] IPv4: Internet Protocol Version 4

[0079] NF:Network Function

[0080] NRF: Network Repository Function, network storage function

[0081] PDU: Protocol Data Unit

[0082] SMF: Session Management Function

[0083] UDM: Unified Data Management

[0084] UE:User Equipment

[0085] URI: Uniform Resource Identifier.

Claims

1. A method for implementing network function discovery of AMF in lightweight 5GC, characterized in that It includes three phases: preparation phase, execution phase and maintenance phase; S1: Preparation phase. The preparation phase of network function discovery in AMF is executed after AMF startup is completed. The preparation phase includes initializing the local cache, obtaining NRF configuration, registering services with NRF, and subscribing to NF status with NRF; S1.1, local cache initialization, AMF's local cache is used to store network function information discovered from NRF, network function types include AUSF, UDM and SMF; local cache means that AMF is used to store network function information discovered from NRF, using a one-dimensional pointer array, each type of network function corresponds to a linked list, and network function instances are stored in a dynamic space, which has better scalability; local cache initialization is to set all pointer arrays to null pointers; S1.1.1, the information that needs to be stored in the local cache includes: the instance identifier of the network function, the instance type, the instance status, the service IP address of the instance, the service port number of the instance, the life span of the instance, the priority of the instance, the weight of the instance, the dynamic load of the instance, and the creation time of the instance; S1.2, obtain NRF configuration. AMF reads NRF configuration information from the local configuration file or obtains it from the network management. The NRF configuration information includes the service IP and service port of NRF. AMF saves the obtained NRF configuration information to the memory. S1.3, register the service with NRF. AMF initiates service registration with NRF according to the NRF configuration information obtained in S1.

2. If the registration fails, AMF needs to start the periodic timer to resend the service registration to NRF regularly until the service registration is successful. S1.3.1, AMF sends heartbeats to NRF regularly according to the heartbeat interval indicated in the service registration response to indicate to NRF that the AMF is available; S1.4, subscribe to the NF status to NRF, and only distinguish the network function type, that is, the subscription request message only carries the network function type of sending the subscription request, the subscribed network function type in the subscription condition, and the destination service address of the NF status notification; S1.4.1, the startup order of each network function in lightweight 5GC is uncertain. AMF may not receive the NF status notification message immediately after successfully completing the subscription process; S2: Execution phase. After AMF is started, user devices may request network services at any time, which will trigger the execution phase of network function discovery. The execution phase includes retrieving local cache, discovering network functions to NRF, and updating local cache space. S2.1, retrieve local cache; AMF receives the service request from the user device, first searches the local cache to find the network function instance that meets the conditions; the conditions include: 1) the instance type is the same as the network function type requested by AMF; 2) the instance status is registered; 3) the instance life cycle has not timed out; S2.1.1: The instance lifecycle in the above condition 3) has not timed out means that the difference between the current time and the time when the instance was created is less than the instance lifecycle; S2.1.2, find the network function instance that meets the conditions in S2.1, form a candidate list of all the network function instances that meet the conditions, select the first instance with the highest priority, the largest weight, and the smallest load from the candidate list and request service from it, and do not execute the subsequent steps; S2.1.3: If no network function instance that meets the conditions is found in S2.1, continue to execute S2.2; S2.2, perform network function discovery to NRF; AMF constructs a network function discovery request, and the discovery condition in the request only sets the network function type to the network function to be discovered; after AMF sends the network function discovery request to NRF, it expects to receive a discovery response message from NRF; S2.2.1, if the AMF does not receive a discovery response from the NRF, it directly replies to the user equipment that the service request has been rejected, and no further subsequent steps are performed; S2.2.2, AMF receives the discovery response from NRF, then proceeds to S2.3; S2.3, update the local cache space; AMF receives the discovery response message from NRF and processes the discovery response message according to the following logic; S2.3.1, if it is a failed response or a successful response that does not carry valid network function instance information, the execution process ends abnormally; S2.3.2, if it is a successful response carrying valid network function instance information and the same instance identifier is in the local cache, the new information is updated to the local cache unit; S2.3.3, if it is a successful response with valid network function instance information but there is no identical instance identifier in the local cache, then the information is inserted into the end of the cache linked list corresponding to the network function type, and the created timetick is set to the current time; S2.3.4, if the execution process ends abnormally, the AMF replies to the user equipment with a response that the service request is rejected, otherwise the AMF continues to provide access services to the user equipment; S3, maintenance phase, in order to allow AMF to manage local cache space to ensure data accuracy, which can be part of the execution phase or triggered by NF status notification; S3.1, when retrieving the local cache in the execution phase, that is, when condition 3) in S2.1 is not satisfied and the instance life cycle has not timed out, the cache unit is deleted from the linked list, so that the local cache space can be updated in real time; S3.2, in lightweight 5GC, the real-time status of each network function is recorded in NRF and NF status notification is sent to the subscriber when the status change is detected. AMF may receive such notification message at any time after completing the preparation phase; S3.3, the maintenance phase triggered by NF status notification includes processing NF status notification requests and updating the locally cached data.

2. According to the method for implementing network function discovery of AMF in lightweight 5GC in claim 1, it is characterized in that The specific operation steps of the maintenance phase process triggered by NF status notification described in S3.3 are as follows: S3.3.1, upon receiving the NF status notification request, the AMF immediately replies a successful response to the NRF, and then extracts the network function instance information in the request message; S3.3.2, if the instance identifier in the request is different from all instance identifiers in the local cache space, insert the instance information into the tail of the cache linked list corresponding to the network function type and set the creation time of the instance to the current time; S3.3.3, if the instance identifier in the request is the same as an instance identifier in the local cache space, update the cache data, and at the same time update the instance life cycle and instance creation time, and set the instance creation time to the current time.

3. According to the method for implementing network function discovery of AMF in lightweight 5GC in claim 1, it is characterized by: In the AMF of lightweight 5GC, AMF implements access and mobility management functions, and provides identity authentication, service authorization and mobility management services for user devices to access the 5G network; AMF provides these services on the premise that it can obtain corresponding services from other NFs, including user authentication information from the authentication server function, user contract data from unified data management, and PDU session management services from the session management function.

Images