Methods, systems, and computer-readable media for providing optimized binding support function (BSF) packet data unit (PDU) session binding discovery responses.

Abstract

A method for providing an optimized BSF PDU session binding discovery response includes: maintaining a PDU session binding database; subscribing to an NRF to receive change notifications for NF profiles of PCF instances or a set of NFs identified in a PDU session binding record; and obtaining a list of NF profiles of PCF instances in the set of NFs identified in the PDU session binding record from the NRF. The method further includes at least one change notification in response to subscribing to receive at least some NF profiles of the set of NFs identified in the PDU session binding record from the NRF. The method also includes receiving a PDU session binding discovery request from a consumer NF, and responding to the PDU session binding discovery request using the PDU session binding record, the list of NF profiles obtained from the NRF, and the change notifications for at least some NF profiles.

Description

[0001] CLAIM OF PRIORITY

[0002] This application claims priority to U.S. Patent Application Serial No. 17 / 093,016, filed November 9, 2020, the disclosure of which is incorporated herein in its entirety by reference. TECHNICAL FIELD

[0003] The subject matter described herein relates to discovering packet data unit (PDU) session bindings. More particularly, the subject matter described herein relates to methods, systems, and computer readable media for providing optimized BSF PDU session binding discovery responses. BACKGROUND

[0004] In a telecommunications network, a service endpoint is an address on a network node that uniquely identifies an entity that provides a service to a service consumer. A service endpoint can include an Internet Protocol (IP) address or a combination of an IP address and a transport layer port number, which is also referred to as an IP endpoint.

[0005] In a 5G telecommunications network, a network node that provides a service is referred to as a producer network function (NF). A network node that consumes a service is referred to as a consumer NF. A network function can be both a producer NF and a consumer NF, depending on whether it is consuming or providing a service.

[0006] A given producer NF can have many service endpoints. A producer NF registers with a network function repository function (NRF). The NRF maintains NF profiles of available NF instances and their supported services. A consumer NF can subscribe to receive information about producer NF instances that have registered with the NRF.

[0007] In addition to a consumer NF, another type of network node that can subscribe to receive information about NF service instances is a service communication proxy (SCP). The SCP subscribes with the NRF and obtains reachability and service profile information about producer NF service instances. A consumer NF connects to the service communication proxy, and the service communication proxy load balances traffic among producer NF service instances that provide a required service, or routes traffic directly to a destination producer NF.

[0008] One issue with the existing 3GPP service architecture is that PDU session binding information maintained in a PDU session binding database at a binding support function (BSF) can not be updated when a state of a policy control function (PCF) associated with the PDU session binding changes. For example, after a user equipment (UE) device registers with a network, the UE creates a PDU session to exchange data with the network. As part of the PDU session creation procedure, a policy control function (PCF) is assigned to the session to generate policy rules for the session to control quality of service and session charging. The PCF assigned to the session registers with a binding support function (BSF), and the BSF creates a binding record for the session in its database. An NF service consumer seeking to discover the PDU session binding for the UE does so by querying the BSF using a discovery API provided by the BSF.

[0009] One issue that can arise when an NF service consumer queries the BSF is that the PDU session binding record maintained by the BSF can not reflect the current operational state of the PCF. For example, after the binding record is created, the operational state of the PCF associated with the binding record can change, e.g., due to the PCF going out of service. A BSF consumer NF can seek to discover the PDU session binding in order to provide a service to the UE. However, if the PDU session binding information does not reflect the current operational state of the PCF, then the NF can receive PDU session binding information for a PCF that is out of service. As a result, the consumer NF can seek to contact the non-operational PCF, fail to receive a response, and then initiate a discovery using a network function (NF) repository function (NRF) to obtain alternative PCF session binding information for the UE. Requiring the consumer NF to contact the BSF, contact the non-operational PCF, contact the NRF, and then contact an alternative PCF assigned to the PDU session can result in a delay in providing the service to the UE.

[0010] In view of these and other challenges, there is a need for improved methods and non-transitory computer readable media for providing optimized BSF PDU session binding discovery responses. SUMMARY

[0011] A method for providing an optimized binding support function (BSF) packet data unit (PDU) session binding discovery response is performed at a BSF comprising at least one processor. The method comprises maintaining a database of PDU session binding records. The method further comprises subscribing to a network function (NF) repository function (NRF) to receive change notifications of NF profiles of a set of NFs or PCF instances identified in a PDU session binding record. The method further comprises obtaining, from the NRF, a list of NF profiles of PCF instances in the set of NFs identified in the PDU session binding record. The method further comprises receiving, from the NRF, at least one change notification of at least some NF profiles of the set of NFs identified in the PDU session binding record in response to the subscribing. The method further comprises receiving a PDU session binding discovery request from a consumer NF. The method further comprises identifying a matching PDU session binding record match in the database of PDU session binding records based on at least one query parameter in the PDU session binding discovery request. The method further comprises generating a PDU session binding discovery response using the matching PDU session binding record, one of the list of NF profiles received from the NRF, and the at least one change notification of the at least some NF profiles. The method further comprises transmitting the PDU session binding response to the consumer NF.

[0012] According to another aspect of the subject matter described herein, obtaining the list of NF profiles comprises transmitting a NRF discovery request to the NRF containing attributes identifying the set of NFs or PCF instances identified in the PDU session binding record.

[0013] According to another aspect of the subject matter described herein, receiving the PDU session binding discovery request comprises receiving a hypertext transfer protocol (HTTP) message from a 5G consumer network function (NF) contacting a PCF bound to a session using a N5 interface.

[0014] According to another aspect of the subject matter described herein, the 5G consumer NF comprises one of an application function (AF), a network exposure function (NEF), a policy control function (PCF), and a network data analytics function (NWDAF).

[0015] According to another aspect of the subject matter described herein, receiving the PDU session binding request comprises receiving a Diameter (Diameter protocol) message from a Diameter node contacting a PCF bound to a session using an Rx interface.

[0016] According to another aspect of the subject matter described herein, the Diameter node using the Rx interface comprises a Diameter relay agent (DRA).

[0017] According to another aspect of the subject matter described herein, generating the PDU session binding response includes selecting an alternative NF profile for the NF profile of the PCF instance identified in the matching PDU session binding record and including the alternative NF profile in the PDU session binding discovery response.

[0018] According to another aspect of the subject matter described herein, selecting the alternative NF profile includes filtering the one list of NF profiles based on attributes included in the matching PDU session binding record and selecting the alternative NF profile from the filtered list.

[0019] According to another aspect of the subject matter described herein, selecting the alternative NF profile includes filtering the one list of NF profiles based on operator-specific parameters and selecting the alternative NF profile from the filtered list.

[0020] According to another aspect of the subject matter described herein, a method for providing an optimized BSF PDU session binding discovery response includes updating the matching PDU session binding record based on attributes of the alternative NF profile.

[0021] According to another aspect of the subject matter described herein, a system for providing an optimized binding support function (BSF) packet data unit (PDU) session binding discovery response is provided. The system includes a BSF including at least one processor and a memory. The system also includes a PDU session binding database located in the memory and containing PDU session binding records. The system further includes a PCF instance tracker implemented by the at least one processor to subscribe to a network function (NF) repository function (NRF) to receive change notifications for a set of NFs or NF profiles of PCF instances identified in the PDU session binding records, obtain a list of NF profiles of PCF instances in the set of NFs identified in the PDU session binding records from the NRF, receive at least one change notification of at least some NF profiles of the set of NFs identified in the PDU session binding records from the NRF in response to the subscription, receive a PDU session binding discovery request from a consumer NF, identify a matching PDU session binding record match in the database of PDU session binding records based on at least one query parameter in the PDU session binding discovery request, generate a PDU session binding discovery response using the matching PDU session binding record, the one list of NF profiles from the NRF, and the at least one change notification of the at least some NF profiles, and transmit the PDU session binding response to the consumer NF.

[0022] According to another aspect of the subject matter described herein, the PCF instance tracker is configured to obtain the list of NF profiles by transmitting a NRF discovery request to the NRF containing attributes identifying the set of NFs identified in the PDU session binding record.

[0023] According to another aspect of the subject described herein, the PCF instance tracker is configured to generate a PDU session binding response by selecting an alternative NF profile for the NF profile of the PCF instance identified in the matching PDU session binding record, and including the alternative NF profile in the PDU session binding discovery response.

[0024] According to another aspect of the subject matter described herein, the PCF instance tracker is configured to select alternative NF profiles by filtering a list of NF profiles based on at least one attribute included in a matching PDU session binding record and carrier-specific parameters, and selecting alternative NF profiles from the filtered list.

[0025] In another aspect of the subject described in this article, the PCF instance tracker is configured to update matching PDU session binding records based on attributes of an alternative NF profile.

[0026] According to another aspect of the subject matter described herein, a non-transitory computer-readable medium having executable instructions stored thereon is provided, which, when executed by a computer's processor, control the computer to perform steps. These steps are performed at a Binding Support Function (BSF) including at least one processor. These steps include maintaining a database of Packet Data Unit (PDU) session binding records. These steps also include subscribing to a Network Function (NF) Repository Function (NRF) to receive change notifications for NF profiles of NF sets or PCF instances identified in the PDU session binding records. These steps also include obtaining a list of NF profiles of PCF instances in the NF sets identified in the PDU session binding records from the NRF. These steps also include receiving at least one change notification of at least some NF profiles of the NF sets identified in the PDU session binding records in response to subscribing to the NRF. These steps also include receiving PDU session binding discovery requests from consumer NFs. These steps also include identifying matching PDU session binding record matches in the database of PDU session binding records based on at least one query parameter in the PDU session binding discovery request. These steps also include generating a PDU session binding discovery response using a matching PDU session binding record, a list of NF profiles from the NRF received list of NF profiles, and at least one change notification for at least some of the NF profiles. These steps also include transmitting the PDU session binding response to the consumer NF.

[0027] The subject matter described herein can be implemented using hardware, software, firmware, or any combination thereof. Thus, as used herein, the terms “function,” “node,” or “module” refer to hardware used to implement the described features, which may also include software and / or firmware components. In one exemplary embodiment, the subject matter described herein can be implemented using a computer-readable medium having computer-executable instructions stored thereon, which, when executed by a computer’s processor, control the computer to perform any one or more of the steps described herein. Exemplary computer-readable media suitable for implementing the subject matter described herein include non-transitory computer-readable media, such as disk storage devices, on-chip memory devices, programmable logic devices, and application-specific integrated circuits (ASICs). Furthermore, computer-readable media implementing the subject matter described herein can reside on a single device or computing platform, or can be distributed across multiple devices or computing platforms. Attached Figure Description

[0028] The subject matter described herein will now be explained with reference to the accompanying drawings, in which:

[0029] Figure 1 This is a network diagram illustrating an exemplary 5G network architecture;

[0030] Figure 2 This is a network diagram illustrating the binding support function and the nodes that transmit the binding support function;

[0031] Figure 3 This is a message flow diagram illustrating exemplary messages exchanged between the BSF and the consumer NF for service registration and discovery;

[0032] Figure 4 This is a message flow diagram illustrating exemplary messages exchanged between BSF and NF service consumers for the PDU session binding discovery service of the N5 interface of the NF service consumer, which supports the policy authorization service.

[0033] Figure 5 This is a message flow diagram illustrating exemplary messages exchanged between the BSF and the Diameter consumer NF for the PDU session binding discovery service, as well as subsequent signaling on the Rx interface between the Diameter consumer and the PCF bound to the PDU session.

[0034] Figure 6 This is a message flow diagram illustrating an exemplary message passing process required to discover the identity of the alternative PCF assigned to the session when the PCF operation state changes after the PDU session binding is established.

[0035] Figure 7This is a block diagram illustrating the BSF that maintains operational status information by tracking PCF instances to present PDU session bindings in the PDU session binding database;

[0036] Figure 8 This is a message flow diagram illustrating exemplary messages exchanged between the PCF instance, BSF, and NRF when the BSF implements PCF instance tracing;

[0037] Figure 9 This is a flowchart illustrating exemplary steps performed by the BSF for PCF instance tracking and providing an optimized PDU session binding discovery response to the consumer NF; and

[0038] Figure 10 This is a flowchart illustrating exemplary steps performed by the BSF when the PCF's operational status changes, for selecting an alternative PCF profile to be provided in the PDU session binding discovery response. Detailed Implementation

[0039] The topics described herein relate to methods, systems, and computer-readable media for providing optimized BSF PDU session binding discovery responses. Figure 1 This is a block diagram illustrating an exemplary 5G system network architecture. Figure 1 The architecture includes the NRF100 and SCP 101, which can reside within the same Household Public Land Mobile Network (HPLMN). As described above, the NRF 100 maintains profiles of available producer NF service instances and their supported services, and allows consumer NFs or SCPs to subscribe to and be notified of new / updated producer NF service instance registrations. The SCP 101 also supports service discovery and producer NF selection. Furthermore, the SCP 101 can perform load balancing for connections between consumer and producer NFs.

[0040] NRF 100 is a repository for NF profiles. To communicate with a producer NF, a consumer NF or SCP must obtain an NF profile from NRF 100. An NF profile is a JSON data structure defined in 3GPP TS29.510 that stores information about an NF service instance. An NF profile definition includes at least one of an FQDN, an IPv4 address, or an IPv6 address. However, it is not required that the NF profile include a separate IP address or IP endpoint associated with the producer NF service endpoint located on the producer NF service instance.

[0041] exist Figure 1In this network, any node (excluding SCP 101 and NRF 100) can be either a consumer NF or a producer NF, depending on whether it is requesting or providing services. In the illustrated example, the nodes include a Policy Control Function (PCF) 102 that performs policy-related operations in the network, a User Data Management (UDM) function 104 that manages user data, and an Application Function (AF) 106 that provides application services. Figure 1 The nodes illustrated also include a Session Management Function (SMF) 108 that manages the session between Access and Mobility Management Function (AMF) 110 and PCF 102. AMF 110 performs mobility management operations similar to those performed by the Mobility Management Entity (MME) in a 4G network. The Authentication Server Function (AUSF) 112 performs authentication services for User Equipment (UE) seeking network access, such as UE 114.

[0042] The Network Slice Selection Function (NSSF) 116 provides network slicing services for devices seeking access to specific network capabilities and features associated with a network slice. The Network Open Function (NEF) 118 provides an application programming interface (API) for application functions seeking information about Internet of Things (IoT) devices and other UEs attached to the network. NEF 118 performs functions similar to the Service Capability Open Function (SCEF) in 4G networks.

[0043] Radio Access Network (RAN) 120 connects UE 114 to the network via a radio link. This can be achieved using a g-Node B (gNB). Figure 1 (Not shown in the image) or other wireless access points to access the radio access network 120. The User Plane Function (UPF) 122 can support various proxy functions for user plane services. An example of such proxy function is the Multipath Transmission Control Protocol (MPTCP) proxy function. The UPF 122 can also support performance measurement functions that can be used by the UE 114 to obtain network performance measurements. Figure 1 The diagram also illustrates data network (DN) 124, through which the UE accesses data network services, such as Internet services.

[0044] Figure 2 This diagram illustrates the network with an additional 5G NF (Binding Support Function (BSF)). The additional 5G NF stores the bindings between PDU sessions and PCFs and allows the discovery of bindings to other nodes. Figure 2 In BSF 200, a service called Nbsf_Management is provided. The Nbsf_Management service is defined in 3GPP TS 29.521.

[0045] Generally, the Nbsf_Management service is used by the BSF to provide PDU session binding functionality. It ensures that AF requests for PDU sessions reach the PCF that holds the PDU session information. The Nbsf_Management service allows consumers to register, update, and remove binding information. The Nbsf_Management service also allows consumers to retrieve binding information.

[0046] exist Figure 2 Among them, consumers of services provided by BSF 200 include PCF 102, NEF 118, AF 106 and Network Data Analysis Function (NWDAF) 200.

[0047] When an IPv4 address and / or IPv6 prefix or MAC address is assigned for a PDU session, the PCF 102 registers binding information for the UE in the BSF. When the UE address information changes for a PDU session, the PCF 102 also updates the binding information with the BSF 200. When an IPv4 address and / or IPv6 prefix or MAC address is released and no longer used for a PDU session, the PCF 102 removes the binding information from the BSF 200.

[0048] NEF 118 provides AF 106 with a means to securely interact with the policy framework used for policy control of 3GPP networks. During this process, any NEF 118 needs to use the Nbsf_Management_Discovery service operation to discover the selected PCF.

[0049] When AF 106 is allowed to interact directly with the policy framework used for policy control, AF 106 uses the Nbsf_Management_Discovery service operation to discover PCFs. NWDAF 202 uses the Nbsf_Management_Discovery service to discover the selected PCF.

[0050] Table 1 below illustrates the operations of the Nbsf_Management service.

[0051]

[0052] Table 1: Operation of Nbsf_management service

[0053] Table 1 shows the Nbsf_management services provided by the BSF, including the Nbsf_Management_Register, Nbsf_Management_Deregister, Nbsf_Management_Discovery, and Nbsf_Management_Update services. The Nbsf_Management_Register and Nbsf_Management_Deregister services are used by the PCF to register and deregister session bindings for the UE. When the UE address of a PDU session changes, the PCF uses the Nbsf_Management_Update service to update the session binding for the UE. The Nbsf_Management_Discovery service allows NF service consumers (such as NEF, AF, and NWDAF) to discover the UE's PDU session binding information. The Nbsf_Management_Discovery service, described in this document, is enhanced by subscribing to receive updated PCF registration status information bound to the PDU session and responding to PDU session binding discovery requests using NF profiles accessible to the PCF instance.

[0054] Figure 3 The diagram illustrates an exemplary message flow when the PCF registers session binding information with the BSF 200 and the consumer NF discovers the session binding information, provided that the PCF registration status has not changed between PDU session binding registration and discovery. (Reference) Figure 3 In step 1, PCF instance 102 N Create a binding for the PDU session at BSF 200. PCF instance 102 acts as an NF service consumer. N You can provide a PCF set ID set to NF_SET within both the "pcfSetId" and "bindLevel" attributes, or a PCF set ID set to NF_INSTANCE within both the "bindLevel" and "pcfId" attributes. The bindLevel attribute defines the binding level of the PDU session and indicates whether a single PCF instance is bound to the session or a set of PCF instances (called the NF set) is assigned to the PDU session. If the bindLevel attribute is set to NF_INSTANCE, a single PCF instance is assigned to the PDU session. If the bindLevel attribute is set to NF_SET, the entire set of PCFs is bound to the PDU session. Figure 3 In the set, PCF collection 300 includes multiple PCF instances 1021-102. NThese can be bound as a set to the same PDU session. In either case, the PCF performing the registration will also specify PCF endpoint identification parameters for the PCF instance providing policy services for the session. This information will be used by the BSF service consumer in the discovery request to obtain PDU session binding information.

[0055] exist Figure 3 In step 2, a consumer NF, which can be any of AF 106, NEF 118, or the alternative PCF 102, sends a BSF discovery request to obtain details of the endpoint that can be used for N5 / Rx messages. BSF 200 provides binding information to consumer NFs 106, 118, or 102. In step 3, consumer NFs 106, 118, or 102 perform N5 / Rx message delivery with the corresponding PCF instance.

[0056] Table 2 below illustrates exemplary PCF binding data that can be registered by PCF to BSF 200.

[0057]

[0058]

[0059] Table 2: PCF Binding Data Registered by PCF to BSF. In Table 2, the attributes pcfFqdn, pcfIpEndPoints, pcfDiamHost, PcfDiamRealm, PcfSmIpEndPoints, pcfId, pcfSetId, and bindLevel in the attribute name column are PCF identification attributes set by the PCF that created or registered the binding record in the BSF. For discovery requests from consumer NFs that contact PCFs bound to a session using the N5 interface, the consumer NF will use the pcfFqdn and pcfIpEndpoints attributes on the N5 interface to contact the PCF. For discovery requests from DRA / AFs that contact PCFs bound to a session using the Rx interface, the DRA / AF will use the PcfDiamHost and PcfDiamRealm attributes to contact the PCF. If another PCF attempts to register a binding for the same subscriber +dnn+snssai, the alternative PCF will use pcfSmFqdn and pcfSmIpEndpoints. As mentioned above, a PCF acting as an NF service consumer can provide a PCF set ID set to NF_SET within the pcfSetId and bindLevel attributes, or a PCF set ID set to pcfSetId and a PCF instance ID set to NF_INSTANCE within the bindLevel and pcfId attributes. The importance of these different attribute settings for providing optimized PDU session binding discovery responses will be discussed below. Figure 9 and 10 Detailed explanation.

[0060] Figure 4 The diagram illustrates an exemplary message flow for the Nbsf_Management_Discovery service, which uses the N5 interface to communicate with a consumer NF bound to a PCF session. (Reference) Figure 4 It can be Figure 2 and Figure 3The NF service consumer 400 of any service consumer shown in the diagram invokes the Nbsf_Management_Discovery service option to obtain the address information of the selected PCF for the PDU session in the BSF (step 1). This service is invoked by sending an HTTP GET message, which includes "query parameters" used by the BSF to locate any corresponding session binding. According to 3GPP TS 29.521, the query parameters include the UE address and may include SUPI or GPSI, DNN and optional S-NSSAI, and the IPv4 address field. Upon receiving the HTTP GET message, the BSF 200 searches for PDU session binding information that matches the query parameters. In step 3, if the HTTP request from the NF service consumer is accepted and a session binding resource matching the query parameters exists, the BSF replies with an HTTP 200 OK response in the response body using the corresponding PcfBinding data structure provided by the PCF during the NbsfManagement_Register service operation. Table 2 above is an example of the PCFBinding data structure provided to the consumer NF in response to the discovery request.

[0061] Figure 5 This is a message flow diagram illustrating the PDU session binding discovery process and subsequent Rx session establishment. Figure 5 In this process, the BSF200 receives discovery requests, which in the Diameter protocol are Rx-AAR-I messages from the AF / DRA 500. The BSF200 includes a Diameter gateway 504 that receives and processes Diameter messages, a Diameter connector 506 that handles Diameter layer connections, and a binding service 508 that implements the Nbsf_Management_Discovery service.

[0062] PCF 102 includes a Diameter gateway 510 that processes received Diameter messages and a Diameter connector 512 that handles Diameter connections. PCF 102 also includes a policy service 514 that makes policy decisions for PDU sessions, a policy authorization service 516 that creates policies, and a session management service 518 that creates session bindings. PCF 102 interacts with session management function 108 to notify session management function 108 of policy decisions.

[0063] exist Figure 5In the message flow shown, in line 1, AF / DRA 500 sends an Rx-AAR-I message to Diameter Gateway 504 of BSF 200. Diameter Gateway 504 receives the message and sends an Rx-AAR-I message to Diameter Connector 506 in line 2. In response to receiving the Rx-AAR-I message, Diameter Connector 506 sends an Nbsf_Management_Discovery message to Binding Service 508. Binding Service 508 performs a lookup in the binding database based on the query parameters in the Nbsf_Management_Discovery message. In line 4, Binding Service 508 sends the binding discovery result to Diameter Connector 506. In line 5, Diameter Connector 506 sends the binding result to Diameter Gateway 504.

[0064] Upon receiving the PDU session binding information, AF / DRA 500 initiates a connection with the PCF assigned to the session on the Rx interface. In line 6 of the message flow diagram, Diameter Gateway 504 sends an Rx-AAR-I proxy message to Diameter Gateway 510 of PCF 102. In line 7, Diameter Gateway 510 sends an Rx-AAR-I proxy message to Diameter Connector 512. In line 8, Diameter Connector 512 sends an Npcf_Policy_Authorization_Create message to PA Service 516. In line 9, PA Service 516 sends a session binding request to Session Management Service 518. In line 10, Session Service 518 sends a session binding reply to PA Service 516. In line 11, PA Service 516 sends a creation reply message to Diameter Connector 512. In line 12, Diameter Connector 512 sends an Rx-AAA-I message to Diameter Gateway 510. In line 13, Diameter gateway 510 sends an Rx-AAA-I message to Diameter gateway 504. In line 14, Diameter gateway 504 sends an Rx-AAA-I message to AF / DRA 500.

[0065] After sending the session binding reply in line 10, SM service 518 sends a policy evaluation message to policy service 514. Policy service 514 makes a decision based on the policy application and sends the policy decision to SM service 518 in line 16. SM service 518 applies the policy decision and sends the policy association notification rule to SMF 108 in line 17.

[0066] Numerous issues and inefficiencies can arise if the PCF's operational status changes after a binding record is created in the BSF. For example, if a PCF service instance goes offline during a network outage or due to service issues, the bindings maintained by the BSF will not be up-to-date, and the NRF discovery process may need to be rerun to find an alternative PCF instance. Other problems can occur when the SM, PA, and Diameter entities used to contact the PCF instance become unreachable. The SM / PA / Diameter entities published in the binding information may also change when a network operator assigns a new IP address, FQDN, or other identifier to the PCF. These changes render the entities listed in the BSF binding table inaccessible, and without the topics described in this article, a manual procedure is required to update the BSF binding record to correct these discrepancies.

[0067] Figure 6 The diagram illustrates the message flow that may occur when a difference arises in the binding database maintained by BSF200. (Reference) Figure 6 In step 1, PCF 102 N The PCF service went down. Therefore, the PCF 102 stored in BSF 200 was also affected. n The PCF information cannot be used to process N5 or Rx messages. In step 2, AF / NEF / PCF 106, 118, or 102 attempts to perform discovery of binding information stored in the BSF. BSF 200 responds with the binding information to identify the faulty PCF 102. N .

[0068] In step 3, upon receiving the discovery response, AF / NEF / PCF 106, 118, or 102 attempts to contact the PCF instance 102 identified in the binding response. N However, PCF 102 N Unavailable. Therefore, if no response is received, AF / NEF / PCF106, 118, or 102 initiates an NF discovery procedure with NRF 100 to identify a new PCF instance. In step 5, consumer NF106, 118, or 102 performs N5 or Rx message signaling with the replacement PCF instance 1021.

[0069] One issue caused by the unavailability of the PCF instance in the BSF binding database is the latency in processing service requests from consumer NFs. As described above, after failing to reach the original PCF, the consumer NF initiates an NRF discovery process and, upon receiving a discovery response from the NRF, reroutes the request to the new PCF. The time required for discovery with the BSF, the failed attempts to contact the PCF, and the discovery with the NRF results in a delay in service delivery to the consumer NF.

[0070] Another issue associated with the outdated binding information maintained by the BSF is the discovery storm at the NRF. When a PCF instance fails, all consumers with binding records for the failed PCF instance will initiate discovery with the NRF as the serving PCF instance to find an identifier for an alternative PCF serving the UE. This can overwhelm the NRF due to a storm of discovery messages at the NRF.

[0071] Other challenges associated with discovery include the fact that non-5G nodes (such as Diameter Relay Agents (DRAs)) may be unable to perform 5G discovery using NRF. Therefore, when the binding information received from the BSF is incorrect or outdated, the DRA has no alternative routes to try. Similarly, the AF may lack the ability to run NRF discovery to select an alternative PCF. This also limits the likelihood of the AF being served by an alternative PCF.

[0072] To avoid these difficulties, BSF can subscribe to NRF to continuously track registered PCF instances for the corresponding PCF set in the PDU session binding database maintained by BSF. When processing a bsf_discovery request, if the binding record exists in the BSF database containing binding level information, BSF can run the additional logic listed in Table 3 below to verify the existence of a reachable endpoint in the binding discovery response.

[0073]

[0074]

[0075] Table 3: PCF Instance Tracking

[0076] The following will describe in detail the operation of BSF in the various scenarios shown in Table 3.

[0077] Figure 7 An overview of the solution is illustrated. Figure 7 In this configuration, BSF 200 includes at least one processor 700 and memory 702. BSF 200 also includes a PCF instance tracker 704, which can be implemented in software executable by the processor 700. The PCF instance tracker 704 subscribes to the NRF 100 to obtain the latest registration status and NF profile information of its bound instances, which are stored in the binding database 706, and generates an optimized BSF PDU session binding discovery response based on the updated registration status and NF profile information.

[0078] Figure 8The diagram illustrates exemplary messaging exchanged between BSF 200, PCF instance 1021, and NRF 100 in association with tracked registered PCF instances. As part of the solution, BSF 200 continuously tracks registered PCF instances for a corresponding "(one or more) pcfset". For example, when any PCF instance from PCF NF set "set 1" creates its first binding, BSF 200 subscribes to NRF 100 to monitor all PCF instances registered with NRF 100 using the pcfset id "set1". BSF 200 also tracks the number of stored binding records for a given PCF NF set id. When the counter for a given NF set id becomes 0, BSF 200 unsubscribes from NRF 100 for that NFset.

[0079] refer to Figure 8 In the message flow diagram, in line 1, PCF instance 1021 of PCF set1 sends a registration message to BSF200 to establish a PDU session binding between PCF instance 1021 and the PDU session. In line 2, BSF 200 creates the session binding, creates the corresponding record in the PDU session binding database, and responds to PCF instance 1021 with an HTTP 201 message indicating that the binding has been created. In line 3, BSF 200 determines whether the registration message received in line 1 is the first message received for PCF set1. In this example, BSF 200 determines that the registration message is the first message received for pcfSetset1. Therefore, in line 4 of the message flow diagram, BSF 200 subscribes to NRF 100 to receive notifications of changes in the state of NF instances in NF set1. In line 5 of the message flow diagram, NRF 100 processes the subscription request for pcfSet set1, creates the subscription, and responds to BSF 200 indicating that the subscription has been created. Once a subscription is created, BSF 200 will receive a notification from NRF 100 whenever the state of any NF instance in set1 changes, until the timer maintained by BSF 200 for the subscription expires and BSF 200 unsubscribes from the state of the PCF set from NRF 100. In line 6 of the message flow graph, BSF 200 calls the nnrf discovery service to discover the PCF profiles in nfSet set1. In line 7, NRF 100 responds with a 200Ok message, which includes a list of NF profiles of the PCFs in set1. After a successful subscription, NRF only notifies the subscription data of changes from the subscription point. Therefore, BSF needs line 6 to obtain a list of all PCF instances in the NFSet and their current state at NRF.

[0080] exist Figure 8Following the message flow, the BSF 200 will have a list of NF profiles for PCFs in set 1 and will subscribe to the NRF to receive updates on PCF status. Whenever the NF profile of any PCF in set 1 changes, the NRF will notify the BSF. Examples of status changes include deregistration, IP address changes, etc. As will be described in detail below, the BSF 200 will use this information to provide an optimized discovery response to consumer NFs seeking to discover PDU session binding information from the BSF 200.

[0081] Figure 9 This is a flowchart illustrating an exemplary process performed by the BSF200 when processing a PDU session binding discovery request message from a consumer NF. (Reference) Figure 9 In step 900, BSF 200 receives a binding discovery request from a consumer NF. The consumer NF can be an AF, NEF, another PCF, or NWDAF. In step 902, BSF 200 determines whether binding data exists in the binding database and whether the solution for maintaining PCF state information is enabled. If the solution is enabled, control proceeds to step 904, where BSF 200 determines whether the binding level attribute is set in a binding record in the PDU session binding database, which contains the binding data requested by the discovery request. As shown in Table 2, the binding level attribute defines the level at which the binding is initially created. If the binding level attribute is set, control proceeds to step 906, where BSF 200 determines whether the binding level is NF_instance.

[0082] If the binding level is set to NF_instance, this indicates that the binding level recorded is a single PCF instance, and control proceeds to step 908, where BSF 200 checks the status of the PCF profile with the same pcfId reported by the NRF, indicating that the corresponding PCF is still registered with the NRF. If the PCF is still registered, control proceeds to step 910, where BSF 200 determines whether the parameters stored for the PCF instance in the binding record match the corresponding details in the NF profile registered with the NRF for the PCF instance. If the parameters match, control proceeds to step 912, where BSF 200 sends a binding discovery response indicating that the PCF instance profile matches the query parameters (such as the UE address) in the binding discovery request.

[0083] Returning to step 910, if the pcfDiamHost, pcfDiamRealm, pcfSmIpEndPoints, or pcfSmFqdn stored for the PCF instance in the binding record do not match the corresponding details in the NF profile registered with the NRF for the PCF instance, then the parameters in the response need to be updated using the parameters registered with the NRF that match the PCF profile. Therefore, control proceeds to step 922, where the mismatched attributes are updated in the binding response and the response is sent to the consumer NF.

[0084] Returning to step 902, if no binding data exists and / or the solution is not enabled, then the default behavior is executed and control proceeds to step 912, where a binding discovery response is sent. If no binding data exists, the binding discovery response will indicate that no binding data in the BSF store matches the query parameters in the binding discovery request.

[0085] Returning to step 904, if the binding level attribute is not set in the binding discovery request, then the BSF cannot use the PCF profile registered with the NRF to verify the PCF instance details from the binding data. Therefore, control proceeds to step 912, where a binding discovery response with PCF information such as that stored in the binding database is sent.

[0086] Returning to step 906, if the binding level in the binding data is not set to NF_Instance, control proceeds to step 914, where it is determined whether the binding level is set to NF_Set. If the binding level is set to NF_Set, control proceeds to step 916, where BSF 200 determines whether the pcfFqdn and pcfIpEndPoints parameters in the binding record match the parameters of any PCF profile registered with the NRF for pcfSetId in the binding record (received by BSF in the discovery response and modified as by any status notification received from BSF). If the parameters match the parameters of any PCF profile registered with the NRF, control proceeds to step 918, where BSF 200 determines whether the PCF pcfDiamHost, pcfDiamRealm, pcfSmFqdn, and pcfSmIpEndpoints parameters match the parameters of the corresponding PCF profile identified as a match in step 916. If the parameters in step 918 match, this indicates that the PCF profile registered with the NRF matches the details in the binding record, and control proceeds to step 912, where a binding discovery response with the PCF profile is sent to the consumer NF.

[0087] Returning to step 908, if the binding level is set to NF_Instance, and the status information of the PCF profile matching pcfId and pcfSetId reported by the NRF is no longer registered with the NRF, then the BSF cannot provide PDU session binding information to the service consumer. In this case, the BSF can respond to the service consumer indicating that no binding information is available and perform actions to clean up or delete the corresponding binding record. Without the solution described herein, the BSF will respond to the discovery request with the PCF profile of the PCF that is no longer registered with the NRF. This will lead to the aforementioned inefficiency, where the service consumer attempts to contact the PCF but fails, and then contacts the NRF to obtain updated binding information for the PDU session.

[0088] Returning to step 914, if bindLevel is not set to NF_Set or NF_Instance, then the binding level is unknown, as these are the only two binding levels allowed by the 3GPP specification. Therefore, control proceeds to step 912, where BSF 200 sends a binding discovery response to the consumer NF, indicating the binding information stored in the binding database.

[0089] Returning to step 916, if the pcfFqdn and pcfIpEndpoints in the binding record matching the query parameters do not match any PCF profile registered with the NRF, then control proceeds to step 920, where BSF 200 selects an alternative PCF profile and sends a discovery response with the alternative PCF profile to the consumer NF. The following is about... Figure 10 This describes the details of the steps performed by BSF 200 to select an alternative PCF profile.

[0090] Returning to step 918, if `pcfFqdn` and `pcfIpEndpoints` in the binding record matching the query parameters match one of the registered PCF profiles, but `pcfDiamHost`, `pcfDiamRealm`, `pcfSmIpEndPoints`, or `pcfSmFqdn` do not match the corresponding PCF profile, then the parameters in the response need to be updated using the parameters of the matching PCF profile registered with the NRF. Therefore, control proceeds to step 922, where the mismatched attributes are updated in the binding response and this response is sent to the consumer NF.

[0091] Figure 10 The diagram illustrates the process of... Figure 9 Step 920 in the example describes the steps for selecting an alternative PCF profile. (See reference...) Figure 10 The selection of an alternative PCF profile begins at step 1000, where BSF 200 receives a list of PCF profiles from the NRF in the discovery response from the NRF to the BSF (see [link to BSF discovery response]).Figure 8 In step 7) or later via notification due to a change in the status of one or more PCF profiles of the subscriber's NfSet, a list of PCF profiles matching the pcfSetId of the binding record is created. In step 1002, BSF 200 determines whether the binding record has the pcfSmFqdn or pcfSmIpEndPoints attribute. If BSF 200 determines that the binding record has the pcfSmFqdn or pcfSmIpEndPoints attribute, then control proceeds to step 1003, where BSF 200 filters profiles to locate profiles supporting at least one instance of the session management service. If BSF 200 determines in step 1002 that the binding record does not have the pcfSmFqdn or pcfSmIpEndPoints attribute, then step 1003 is bypassed.

[0092] After step 1000 or 1003, control then proceeds to step 1004, where BSF 200 determines whether the binding record has the pcfFqdn or pcfIpEndPoints attribute. If the binding record includes these attributes, control proceeds to step 1006, where BSF 200 filters profiles of registered PA services. If the binding record does not include the pcfFqdn or pcfIpEndPoints attribute, step 1006 is bypassed.

[0093] After step 1004 or 1006, control proceeds to step 1008, where BSF 200 determines whether the binding record has the `pcfDiamHost` and `pcfDiamRealm` attributes. If the binding record has the `pcfDiamHost` and `pcfDiamRealm` attributes, control proceeds to step 1009, where BSF 200 filters profiles with Diameter attributes published to NRF in `pcfinfo`. If the binding record does not have the `pcfDiamHost` and `pcfDiamRealm` attributes, step 1009 is bypassed.

[0094] Following the filtering in step 1009, or if the binding record in step 1008 does not have the `pcfDiamHost` and `pcfDiamRealm` attributes, control then proceeds to step 1010, where BSF 200 determines whether the list has more than one profile after filtering. If the filtered list includes more than one profile, control proceeds to step 1011, where BSF 200 selects a profile with a matching SM service version based on the carrier configuration filtering profile. This is an optional step. This step is not required when the carrier network has more than one PCF instance in the same PCF set with the same major version. Control then proceeds to step 1012, where BSF 200 selects a profile with a specific API version, load, capacity, location, etc., that best meets the network carrier's requirements, as a replacement PCF profile for PCFs whose status has changed since the binding record was created. If the BSF determines that the list does not include more than one profile in step 1010, then steps 1011 and 1012 are bypassed.

[0095] Following the filtering in step 1012, or if no more than one profile is found in step 1010, control proceeds to step 1014, where BSF 200 determines whether at least one profile exists in the filtered list. If BSF 200 determines that at least one profile exists in the filtered list, control proceeds to step 1016, where BSF 200 updates the binding discovery response to be sent to the consumer NF to match the parameters of the alternative PCF profile. BSF 200 may optionally update the binding records in the PDU session binding database to include the updated information of the alternative PCF. In step 1018, BSF 200 sends a discovery response with the alternative PCF binding information to the consumer NF.

[0096] If BSF 200 determines in step 1014 that there are no remaining profiles in the list, it means that BSF 200 cannot find an alternative PCF profile to include in the binding discovery response. Therefore, control proceeds to step 1018, where the binding discovery response is sent along with the PCF profile from the PDU session binding record.

[0097] Therefore, the solution described in this paper allows the BSF to proactively monitor PCF status information by subscribing to and receiving updates from the NRF. If a PCF maintaining its binding information at the BSF fails, stops service, or changes attributes in its NF profile, the BSF will update the information to be provided to the consumer NF in the binding discovery response upon receiving a discovery request and provide the updated binding information to the requesting consumer NF. The BSF may optionally update the UE's binding information in the PDU session binding database. This solution reduces additional messaging from consumer NFs (such as AF, NEF, and PCF) to the NRF. It provides efficient network utilization while avoiding network overload. Higher throughput and lower latency can also be achieved at the AF, NEF, and PCF by avoiding unnecessary NRF discoveries.

[0098] The topic described in this article is optional and backward compatible. It requires no parameters or triggers from any other NF, thus allowing control and scope of the feature to be implemented at the BSF. Network operators can selectively enable the feature for specific consumers. Information about the consumers seeking to enforce selective enabling can provide selection details such as the instance ID or PLMN ID in the authorization token. Alternatively, for HTTPS connections, a Transport Layer Security (TLS) certificate can be used to identify the consumer. Similarly, vendor-specific attributes in the discovery request can also be used to identify the consumer.

[0099] The publicly available information of each of the following references is incorporated into this article in its entirety through citation.

[0100] References

[0101] 3. 3GPP TS 29.521; 3 rd Generation Partnership Project; TechnicalSpecification Group Core Network and Terminals; 5G System; Binding SupportManagement Service; Stage 3(Release 16),V16.5.0(2020-09).

[0102] 4. 3GPP TS 29.510; 3 rdGeneration Partnership Project; TechnicalSpecification Group Core Network and Terminals; 5G System; Network FunctionRepository Services; Stage 3(Release 16),V16.5.0(2020-09).

[0103] It will be understood that various details of the currently disclosed subject matter may be changed without departing from the scope of the currently disclosed subject matter. Furthermore, the foregoing description is for illustrative purposes only and not for limiting purposes.

Claims

1. A method for providing an optimized binding support function (BSF) packet data unit (PDU) session binding discovery response, the method comprising: at a BSF comprising at least one processor: maintaining a database of packet data unit (PDU) session binding records; subscribing to a network function (NF) repository function (NRF) to receive change notifications of NF profiles of a set of policy control function (PCF) instances identified in a PDU session binding record, wherein subscribing to the NRF includes subscribing to the NRF to monitor all PCF instances of the set of PCF NFs registered with the NRF in response to a first PDU session binding being created in the BSF for one of the PCF instances of the set of PCF NFs; obtaining from the NRF a list of NF profiles of the PCF instances of the set of NFs identified in the PDU session binding record; in response to the subscribing, receiving from the NRF at least one change notification of at least some of the NF profiles of the set of NFs identified in the PDU session binding record; receiving a PDU session binding discovery request from a consumer NF; identifying a matching PDU session binding record in the database of PDU session binding records based on at least one query parameter in the PDU session binding discovery request; and generating a PDU session binding discovery response using the matching PDU session binding record, one of the list of NF profiles received from the NRF, and the at least one change notification of the at least some of the NF profiles; and transmitting the PDU session binding discovery response to the consumer NF.

2. The method of claim 1, wherein obtaining the list of NF profiles includes transmitting a NRF discovery request to the NRF containing attributes identifying the set of NFs identified in the PDU session binding record.

3. The method of claim 1 or claim 2, wherein receiving the PDU session binding discovery request includes receiving a hypertext transfer protocol (HTTP) message from a 5G consumer network function (NF) that contacts a PCF bound to a session using a N5 interface.

4. The method of claim 3, wherein the 5G consumer NF includes one of an application function (AF), a network exposure function (NEF), a policy control function (PCF), and a network data analytics function (NWDAF).

5. The method of any preceding claim, wherein receiving the PDU session binding discovery request includes receiving a Diameter message from a Diameter node that contacts a PCF bound to a session using an Rx interface.

6. The method of claim 5, wherein the Diameter node using the Rx interface includes a Diameter relay agent (DRA) or a Diameter-based application server.

7. The method of any preceding claim, wherein generating the PDU session binding discovery response includes selecting an alternative NF profile for an NF profile of a PCF instance identified in the matching PDU session binding record and including the alternative NF profile in the PDU session binding discovery response.

8. The method of claim 7, wherein selecting an alternative NF profile comprises filtering the one list of NF profiles based on attributes included in the matching PDU session binding record and selecting an alternative NF profile from the filtered list.

9. The method of claim 7, wherein selecting an alternative NF profile comprises filtering the one list of NF profiles based on operator-specific parameters and selecting an alternative NF profile from the filtered list.

10. The method of any of claims 7 to 9, comprising updating the matching PDU session binding record based on attributes of the alternative NF profile.

11. A system for providing an optimized binding support function (BSF) packet data unit (PDU) session binding discovery response, the system comprising: a BSF comprising at least one processor and a memory; a PDU session binding database located in the memory and comprising PDU session binding records; a policy control function (PCF) instance tracker implemented by the at least one processor to subscribe to a network function (NF) repository function (NRF) to receive change notifications of NF profiles of PCF instances of a set of NFs identified in a PDU session binding record, wherein subscribing to the NRF comprises subscribing to the NRF to monitor all PCF instances of the set of PCF NFs registered with the NRF in response to a first PDU session binding being created in the BSF by one of the PCF instances of the set of PCF NFs; obtaining from the NRF a list of NF profiles of the PCF instances of the set of NFs identified in the PDU session binding record; in response to the subscribing, receiving from the NRF at least one change notification of at least some of the NF profiles of the set of NFs identified in the PDU session binding record; receiving a PDU session binding discovery request from a consumer NF; and identifying a matching PDU session binding record in the database of PDU session binding records based on at least one query parameter in the PDU session binding discovery request; generating a PDU session binding discovery response using the matching PDU session binding record, one of the list of NF profiles received from the NRF, and the at least one change notification of the at least some of the NF profiles; and transmitting the PDU session binding discovery response to the consumer NF.

12. The system of claim 11, wherein the PCF instance tracker is configured to obtain the list of NF profiles by transmitting a NRF discovery request to the NRF containing attributes identifying the set of NFs identified in the PDU session binding record.

13. The system of claim 11 or claim 12, wherein the PDU session binding discovery request comprises a hypertext transfer protocol (HTTP) message from a 5G consumer network function (NF) that contacts a PCF bound to a session using an N5 interface.

14. The system of claim 13, wherein the 5G consumer NF comprises one of an application function (AF), a network exposure function (NEF), a policy control function (PCF), and a network data analytics function (NWDAF).

15. The system of any of claims 11 to 14, wherein the PDU session binding discovery request comprises a Diameter message from a Diameter node that contacts a PCF bound to a session using an Rx interface.

16. The system of claim 15, wherein the Diameter node using the Rx interface comprises a Diameter Relay Agent (DRA).

17. The system of any of claims 11 to 16, wherein the PCF instance tracker is configured to generate the PDU session binding discovery response by selecting an alternative NF profile for the NF profile of the PCF instance identified in the matching PDU session binding record and including the alternative NF profile in the PDU session binding discovery response.

18. The system of claim 17, wherein the PCF instance tracker is configured to select the alternative NF profile by filtering the list of one NF profiles based on at least one attribute included in the matching PDU session binding record and operator-specific parameters and selecting the alternative NF profile from the filtered list.

19. The system of claim 17, wherein the PCF instance tracker is configured to update the matching PDU session binding record based on attributes of the alternative NF profile.

20. A non-transitory computer-readable medium having stored thereon executable instructions that, when executed by a processor of a computer, control the computer to perform steps comprising: at a binding support function (BSF) comprising at least one processor: maintaining a database of packet data unit (PDU) session binding records; subscribing to a network function (NF) repository function (NRF) to receive change notifications of NF profiles of PCF instances of a set of NFs identified in a PDU session binding record, wherein subscribing to the NRF includes subscribing to the NRF to monitor all PCF instances of the set of PCF NFs registered with the NRF in response to a first PDU session binding being created in the BSF for one of the PCF instances of the set of PCF NFs; obtaining from the NRF a list of NF profiles of the PCF instances of the set of NFs identified in the PDU session binding record; in response to the subscribing, receiving from the NRF at least one change notification of at least some of the NF profiles of the set of NFs identified in the PDU session binding record; receiving a PDU session binding discovery request from a consumer NF; identifying a matching PDU session binding record in the database of PDU session binding records based on at least one query parameter in the PDU session binding discovery request; generating a PDU session binding discovery response using the matching PDU session binding record, one of the list of NF profiles received from the NRF, and the at least one change notification of the at least some of the NF profiles; and transmitting the PDU session binding discovery response to the consumer NF. ​

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