Techniques to verify the issuer of an access token

Abstract

Embodiments include network equipment configured to implement a service producer network function (NFp) of a communication network and network equipment configured to implement a network repository function (NRF) of the communication network, a method, a non-transitory, computer-readable medium, and a computer program product corresponding to each of the network equipment. The network equipment configured implement the NFp receives, from a service consumer network function (NFc), a request for a service provided by the NFp. The request includes an access token issued by a first network repository function (NRF). The access token includes a network function (NF) identifier of the first NRF. The network equipment verifies the access token in response to at least one of the following: the first NRF corresponds to a second NRF with which the NFp previously registered; when the NFp stores a first list of NRFs authorized to provide access tokens for the service, the first NRF corresponds to any NRFs in the first list; and when the NFp stores a second list of NRF sets authorized to provide access tokens for the service, the first NRF corresponds to any NRF sets in the second list.

Description

[0001] TECHNIQUES TO VERIFY THE ISSUER OF AN ACCESS TOKEN

[0002] TECHNICAL FIELD

[0003] The present disclosure relates generally to the field of communication networks, and more specifically to techniques for verifying that an access token, purporting to grant by a consumer network function (NFc) access to a service provided by a producer network function (NFp) in another PLMN, was issued by a trusted source.

[0004] INTRODUCTION

[0005] The fifth generation (5G) of cellular systems is being standardized within the Third- Generation Partnership Project (3GPP). 5G is developed for maximum flexibility to support multiple and substantially different use cases. These include enhanced mobile broadband (eMBB), machine type communications (MTC), ultra-reliable low latency communications (URLLC), side-link device-to-device (D2D), and several other use cases. 5G was initially standardized in 3GPP Rel-15 and continues to evolve through subsequent releases.

[0006] At a high level, the 5G System (5GS) consists of an Access Network (AN) and a Core Network (CN). The AN provides UEs connectivity to the CN, e.g., via base stations such as gNBs or ng-eNBs. As described in more detail below, the CN includes a variety of Network Functions (NF) that provide a range of different functionalities such as session management, connection management, charging, authentication, etc.

[0007] Figure 1 illustrates a high-level view of an exemplary 5G network architecture, which includes a Next Generation Radio Access Network (NG-RAN, 199) and a 5G Core (5GC, 198). The NG-RAN can include one or more gNodeB’s (gNBs, e.g., 100, 150) connected to the 5GC via one or more NG interfaces (e.g., 102, 152). More specifically, the gNBs can be connected to one or more Access and Mobility Management Functions (AMFs) in the 5GC via respective NG- C interfaces and to one or more User Plane Functions (UPFs) in the 5GC via respective NG-U interfaces. Various other network functions (NFs) can be included in the 5GC, as described in more detail below.

[0008] In addition, the gNBs can be connected to each other via one or more Xn interfaces (e.g., 140 between gNBs 100, 150). The radio technology for the NG-RAN is often referred to as “New Radio” (NR). With respect to the NR interface to UEs, each of the gNBs can support frequency division duplexing (FDD), time division duplexing (TDD), or a combination thereof. Each of the gNBs can serve a geographic coverage area including one or more cells and, in some cases, can also use various directional beams to provide coverage in the respective cells.

[0009] NG RAN logical nodes shown in Figure 1 include a Centralized Unit (CU or gNB-CU) and one or more Distributed Units (DU or gNB-DU). CUs (e.g., 110) are logical nodes that host higher-layer protocols and perform various gNB functions such controlling the operation of DUs. In contrast, DUs (e.g., 120, 130) are decentralized logical nodes that host lower layer protocols and can include, depending on the functional split option, various subsets of gNB functions. A CU connects to one or more DUs over respective Fl logical interfaces (e.g., 122, 132 in Figure 1).

[0010] Another change in 5G networks (e.g., in 5GC) is that traditional peer-to-peer interfaces and protocols found in earlier-generation networks are modified and / or replaced by a Service Based Architecture (SBA) in which Network Functions (NFs) provide one or more services to one or more service consumers. This can be done, for example, by Hyper Text Transfer Protocol / Representational State Transfer (HTTP / REST) application programming interfaces (APIs). In general, the various services are self-contained functionalities that can be changed and modified in an isolated manner without affecting other services.

[0011] The 5G SBA model is based on principles including modularity, reusability, and selfcontainment of NFs, which can enable network deployments to take advantage of the latest virtualization and software technologies. In the 5G SBA, network repository functions (NRF) allow every network function to discover the services offered by other network functions, and Data Storage Functions (DSF) allow every network function to store its context.

[0012] The NFs in the 5GC SBA can communicate with each other directly or indirectly. Indirect communication between an NF acting as service consumer and NF acting as service producers involves a Service Communication Proxy (SCP). Both types of communication can use authentication for security. For direct communication, authentication between NFs and / or NRF within a single public land mobile network (PLMN) can be based on Transport Layer Security (e.g., TLS) or may be implicit based on lower layer security (NDS / IP / physical) if TLS is unavailable.

[0013] 3GPP TS 33.501 (vl7.11.1) describes an Oauth2.0-based framework (described further in Internet Engineering Task Force (IETF) Request For Comments (RFC) 6749) that allows an NF service producer (NFp) to authorize requests from an NF service consumer (NFc) to access a service produced by the NFp. Within the Oauth2.0 framework, the NRF plays the role of Oauth2.0 server, the NFc plays the role of Oauth2.0 client, and the NFp plays the role of Oauth2.0 resource server. The authorization is based on NRF-issued access tokens, which are JSON Web Tokens as described in IETF RFC 7519. Each access token includes an “issuer” claim that identifies the issuing NRF. Moreover, each access token is secured with a digital signature or Message Authentication Codes (MAC) based on JSON Web Signature (JWS) as described in IETF RFC 7515. SUMMARY

[0014] According to 3 GPP TS 33.501 (vl7.11.1) section 13.4.1.1.2, anNFp verifies the integrity of an NRF-issued access token presented by an NFc requesting service access. In particular, the NFp verifies the NRF’s digital signature using NRF’s public key, or by checking the MAC value using a shared secret. However, 3GPP TS 33.501 (vl7.11.1) does not specify whether, nor how, an NFp verifies the issuer claim in the access token being legitimate. Without verifying the issuer claim, it is possible for an NFp to grant service access to the NFc based on an access token issued by an NRF that the NFp does not trust.

[0015] An object of embodiments of the present disclosure is to address improved verification of access tokens presented by NFc’s, thereby enabling otherwise-advantageous use of NRF-issued access tokens for authorizing service access.

[0016] Some embodiments of the present disclosure include methods (e.g, procedures) performed by a service producer network function (NFp) of a communication network.

[0017] These exemplary methods include receiving, from a service consumer network function (NFc) of the communication network, a request for a service provided by the NFp. The request includes an access token issued by a first network repository function (NRF) of the communication network. The access token includes a network function (NF) identifier of the first NRF. These exemplary methods also include verifying the access token in response to at least one of the following conditions:

[0018] • the first NRF corresponds to a second NRF with which the NFp previously registered;

[0019] • when the NFp stores a first list of NRFs authorized to provide access tokens for the service, the first NRF corresponds to any NRFs in the first list; and

[0020] • when the NFp stores a second list of NRF sets authorized to provide access tokens for the service, the first NRF corresponds to any NRF sets in the second list.

[0021] In some embodiments, these exemplary methods also include the following operations:

[0022] • determining whether the NF identifier of the first NRF matches at least one of the following NF identifiers: an NF identifier of the second NRF, and when the NFp stores the first list, an NF identifier of any NRFs in the first list; and

[0023] • when the NF identifier of the first NRF does not match at least one of the NF identifiers, determining whether an NF set identifier associated with the first NRF is available and matches at least one of the following NF set identifiers: an NF set identifier associated with the second NRF, and when the NFp stores the second list, an NF set identifier of any NRF sets in the second list.

[0024] In such embodiments, verifying the access token is responsive to at least one of the following:

[0025] • the NF identifier of the first NRF matches at least one of the NF identifiers; and • the NF set identifier associated with the first NRF is available and matches at least one of the NF set identifiers.

[0026] Other embodiments include methods (e.g, procedures) performed by a first network repository function (NRF) of a communication network. In general, these exemplary methods are complementary to the exemplary methods for an NFp, summarized above.

[0027] These exemplary methods include receiving, from a service consumer network function (NFc), a request for an access token granting the NFc access to the service produced by the NFp. These exemplary methods also include generating the requested access token based on determining that the NFc is authorized to access the service. A field of the generated access token includes an NF set identifier associated with the first NRF. These exemplary methods also include sending the access token to the NFc in accordance with the request.

[0028] In some embodiments, the first and second NRFs are part of a single NRF set. In some embodiments, the communication network is a 5G core network (5GC).

[0029] These and other embodiments described herein can provide novel, flexible, and efficient techniques that facilitate a set of NRF instances to act as a single NRF, with one NRF instance signing access tokens on behalf of another NRF instance in the set. Moreover, this benefit is enabled without impacting an NFp’s ability to verify the legitimacy of an access token as basis for granting service access to a requesting NFc. At a high level, embodiments improve security of service access in a communication network, such as 5GC.

[0030] These and other objects, features, and advantages of the present disclosure will become apparent upon reading the following Detailed Description in view of the Drawings briefly described below.

[0031] BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figures 1-2 illustrate various aspects of an exemplary 5G network architecture.

[0033] Figure 3 shows a signal flow diagram illustrating conventional token-based authorization for access to 5GNF services.

[0034] Figure 4 shows a signal flow diagram illustrating token-based authorization for access to NF services, according to embodiments of the present disclosure.

[0035] Figure 5 shows an exemplary method (e.g, procedure) performed by an NFp, according to various embodiments of the present disclosure.

[0036] Figure 6 shows an exemplary method (e.g, procedure) performed by a first NRF, according to various embodiments of the present disclosure.

[0037] Figure 7 shows a communication system according to various embodiments of the present disclosure. Figure 8 shows a network node according to various embodiments of the present disclosure.

[0038] Figure 9 is a block diagram of a virtualization environment in which functions implemented by some embodiments of the present disclosure may be virtualized.

[0039] DETAILED DESCRIPTION

[0040] Embodiments briefly summarized above will now be described more fully with reference to the accompanying drawings. These descriptions are provided by way of example to explain the subject matter to those skilled in the art and should not be construed as limiting the scope of the subject matter to only the embodiments described herein. More specifically, examples are provided below that illustrate the operation of various embodiments according to the advantages discussed above.

[0041] In general, all terms used herein are to be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is clearly given and / or is implied from the context in which it is used. All references to a / an / the element, apparatus, component, means, step, etc. are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, step, etc., unless explicitly stated otherwise. The operations of any methods and / or procedures disclosed herein do not have to be performed in the exact order disclosed, unless an operation is explicitly described as following or preceding another operation and / or where it is implicit that an operation must follow or precede another operation. Any feature of any embodiment disclosed herein can apply to any other disclosed embodiment, as appropriate. Likewise, any advantage of any embodiment described herein can apply to any other disclosed embodiment, as appropriate.

[0042] Furthermore, the following terms are used throughout the description given below:

[0043] • Radio Access Node: As used herein, a “radio access node” (or equivalently “radio network node,” “radio access network node,” or “RAN node”) can be any node in a radio access network (RAN) that operates to wirelessly transmit and / or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., gNB in a 3GPP 5G / NR network or an enhanced or eNB in a 3 GPP LTE network), base station distributed components (e.g, CU and DU), a high-power or macro base station, a low-power base station (e.g., micro, pico, femto, or home base station, or the like), an integrated access backhaul (IAB) node, a transmission point (TP), a transmission reception point (TRP), a remote radio unit (RRU or RRH), and a relay node.

[0044] • Core Network Node: As used herein, a “core network node” is any type of node in a core network. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a serving gateway (SGW), a PDN Gateway (P-GW), a Policy and Charging Rules Function (PCRF), an access and mobility management function (AMF), a session management function (SMF), a user plane function (UPF), a Charging Function (CHF), a Policy Control Function (PCF), an Authentication Server Function (AUSF), a location management function (LMF), or the like.

[0045] • Wireless Device: As used herein, a “wireless device” (or “WD” for short) is any type of device that is capable, configured, arranged and / or operable to communicate wirelessly with network nodes and / or other wireless devices. Communicating wirelessly can involve transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information through air. Unless otherwise noted, the term “wireless device” is used interchangeably herein with the term “user equipment” (or “UE” for short), with both of these terms having a different meaning than the term “network node”.

[0046] • Radio Node: As used herein, a “radio node” can be either a “radio access node” (or equivalent term) or a “wireless device.”

[0047] • Network Node: As used herein, a “network node” is any node that is either part of the radio access network (e.g., a radio access node or equivalent term) or of the core network (e.g., a core network node discussed above) of a cellular communications network. Functionally, a network node is network equipment capable, configured, arranged, and / or operable to communicate directly or indirectly with a wireless device and / or with other network nodes or equipment in the cellular communications network, to enable and / or provide wireless access to the wireless device, and / or to perform other functions (e.g, administration) in the cellular communications network.

[0048] • Node: As used herein, the term “node” (without prefix) can be any type of node that can in or with a wireless network (including RAN and / or core network), including a radio access node (or equivalent term), core network node, or wireless device. However, the term “node” may be limited to a particular type (e.g., radio access node) based on its specific characteristics in any given context.

[0049] The above definitions are not meant to be exclusive. In other words, various ones of the above terms may be explained and / or described elsewhere in the present disclosure using the same or similar terminology. Nevertheless, to the extent that such other explanations and / or descriptions conflict with the above definitions, the above definitions should control.

[0050] Note that the description given herein focuses on a 3GPP cellular communications system and, as such, 3GPP terminology or terminology similar to 3GPP terminology is generally used. However, the concepts disclosed herein are not limited to a 3GPP system, and can be applied in any system that can benefit from the concepts, principles, and / or embodiments described herein.

[0051] Figure 2 shows an exemplary non-roaming reference architecture for a 5G network (200). These include the following 3GPP-defined NFs and service-based interfaces:

[0052] • Application Function (AF) with Naf interface, interacts with the 5GC to provision information to the network operator and to subscribe to certain events happening in operator's network. An AF offers applications for which service is delivered in a different layer (i.e., transport layer) than the one in which the service has been requested (i.e., signaling layer), the control of flow resources according to what has been negotiated with the network. An AF communicates dynamic session information to PCF (via N5 interface), including description of media to be delivered by transport layer.

[0053] • Policy Control Function (PCF) with Npcf interface, supports unified policy framework to govern the network behavior, via providing PCC rules (e.g., on the treatment of each service data flow that is under PCC control) to the SMF via the N7 reference point. PCF provides policy control decisions and flow based charging control, including service data flow detection, gating, QoS, and flow-based charging (except credit management) towards the SMF. The PCF receives session and media related information from the AF and informs the AF of traffic (or user) plane events.

[0054] • User Plane Function (UPF) supports handling of user plane traffic based on the rules received from SMF, including packet inspection and different enforcement actions (e.g., event detection and reporting). UPFs communicate with the RAN (e.g., NG-RNA) via the N3 reference point, with SMFs (discussed below) via the N4 reference point, and with an external packet data network (PDN) via the N6 reference point. The N9 reference point is for communication between two UPFs.

[0055] • Session Management Function (SMF) with Nsmf interface, interacts with the decoupled traffic (or user) plane, including creating, updating, and removing Protocol Data Unit (PDU) sessions and managing session context with the User Plane Function (UPF), e.g., for event reporting. For example, SMF performs data flow detection (based on filter definitions included in PCC rules), online and offline charging interactions, and policy enforcement.

[0056] • Charging Function (CHF) with Nchf interface, is responsible for converged online charging and offline charging functionalities. It provides quota management (for online charging), re-authorization triggers, rating conditions, etc. and is notified about usage reports from the SMF. Quota management involves granting a specific number of units (e.g., bytes, seconds) for a service. CHF also interacts with billing systems. Access and Mobility Management Function (AMF) with Namf interface, terminates the RAN CP interface and handles all mobility and connection management of UEs (similar to MME in EPC). AMFs communicate with UEs via the N1 reference point and with the RAN (e.g., NG-RAN) via the N2 reference point.

[0057] • Network Exposure Function (NEF) with Nnef interface, acts as the entry point into operator's network, by securely exposing to AFs the network capabilities and events provided by 3GPP NFs and by providing ways for the AF to securely provide information to 3GPP network. For example, NEF provides a service that allows an AF to provision specific subscription data (e.g., expected UE behavior) for various UEs.

[0058] • Network Repository Function (NRF, 210) with Nnrf interface, provides service registration and discovery, enabling NFs to identify appropriate services available from other NFs.

[0059] • Network Slice Selection Function (NSSF) with Nnssf interface: A “network slice” is a logical partition of a 5G network that provides specific network capabilities and characteristics, e.g., in support of a particular service. A network slice instance is a set of NF instances and the required network resources (e.g., compute, storage, communication) that provide the capabilities and characteristics of the network slice. The NSSF enables other NFs (e.g., AMF) to identify a network slice instance that is appropriate for a UE’s desired service.

[0060] • Authentication Server Function (AUSF) with Nausf interface, performs user authentication and computes security key materials for various purposes, and is based in a user’s home network (HPLMN),

[0061] • Network Data Analytics Function (NWDAF) with Nnwdaf interface, provides network analytics information (e.g., statistical information of past events and / or predictive information) to other NFs on a network slice instance level.

[0062] • Secure Edge Protection Proxy (SEPP) is an entity sitting at PLMN perimeter that facilitates end-to-end confidentiality and integrity protection of individual elements of application-layer control plane messages exchanged with other PLMNs, based on transport layer security (TLS) via N32 interface.

[0063] • The Unified Data Management function (UDM) with Nudm interface, supports generation of 3GPP authentication credentials, user identification handling, access authorization based on subscription data, and other subscriber-related functions. To provide this functionality, the UDM uses subscription data (including authentication data) stored in the 5GC unified data repository (UDR). In addition to the UDM, the UDR supports storage and retrieval of policy data by the PCF, as well as storage and retrieval of application data by NEF. Data Storage Functions (DSF) allow every NF to store its context.

[0064] The services provided by the various NFs are composed of “service operations”, which are more granular divisions of the overall service functionality. The interactions between service consumers and producers can be of the type “request / response” or “subscribe / notify”. In the latter type, a service consumer NF (or equivalently, “consumer NF”) requests a service producer NF (or equivalently, “producer NF”) to establish a subscription for the service consumer NF to receive notifications from the service producer NF under conditions specified in this subscription.

[0065] As described in 3GPP TS 23.501 (vl7.10.0) section 5.21, the 5GC supports “sets” of NFs to improve network reliability, particularly addition or removal of NF instances for redundancy and scalability. In other words, an NF can be replaced by an interchangeable alternative NF in scenarios of failure, load balancing, etc. without impacting handling of services requested by NFc’s. The following terminology is used when describing this functionality:

[0066] • NF Service Set: A group of interchangeable NF service instances of the same service type within an NF instance. The NF service instances in the same NF Service Set have access to the same context data.

[0067] • NF Set: A group of interchangeable NF instances of the same type, supporting the same services and the same Network Slice(s). The NF instances in the same NF Set may be geographically distributed but have access to the same context data.

[0068] To summarize, multiple NF instances can be configured as an NF set to provide distributed, redundant, stateless, and scalable services. The same functionality is also supported on the NF service level, such as by equivalent NFs and NF Services share the same context data or by Network Function / NF Service Context Transfer.

[0069] Token-based authorization for the SBA is defined in 3GPP TS 33.501 (vl7.11.1). This mechanism involves a consumer for a NF service (referred to as “NF Service Consumer” or more simply “Service Consumer”) obtaining an access token for the service from an authorization server before accessing the service. The authorization is based on an Oauth2.0- based framework (described further in IETF RFC 6749) in which the NRF plays the role of Oauth2.0 server, the NFc plays the role of Oauth2.0 client, and the NFp plays the role of Oauth2.0 resource server.

[0070] Access tokens are JSON Web Tokens as described in IETF RFC 7519 and are secured by the NFc with digital signatures or Message Authentication Codes (MAC) based on JSON Web Signature (JWS) as described in IETF RFC 7515. Note that securing the access token as described in RFC 7515 requires a pairwise pre-shared symmetric key between the NRF and the NFp. The provisioning of such pre-shared symmetric key is up to vendor implementation. Figure 3 shows a signal flow diagram illustrating token-based authorization for access to NF services. Operations 1-3 are part of the NF Service registration procedure in which the NFp provides information about the NF Service to the authorization server (NRF), which stores this information in a NF producer profile. The service information may identify resources and actions (or service operations) that are allowed for NF Service Consumers (NFc’s).

[0071] In operation 4, the NFc requests an access token from the NRF using the Nnrf AccessToken Get Request operation. The message includes the NF Instance ID(s) of the NFc, the requested "scope" including the expected NF Service name(s), optionally "additional scope" information (e.g., requested resources and requested service operations on the resources), and NF types of the expected NFp instance and of the NFc.

[0072] In operation 5, the NRF checks whether the NFc is authorized to access the requested service(s). If the NFc is authorized, the NRF generates an access token with appropriate claims included. According to 3GPP TS 23.501 (v!7.9.0), the access token (or CCA) shall include the NF instance ID of the NFc (as subject), a timestamp and expiration time, the NF type of the expected audience (i.e., NRF or NFp). The NRF digitally signs the generated access token based on a shared secret or private key as described in RFC 7515. If the NFc is not authorized, the NRF does not issue the access token. In operation 6, the NRF sends the access token to the NFc in an Nnrf AccessToken Get Response operation.

[0073] According to RFC 7515, it is necessary for the recipient of a JWS to be able to determine the key that was used for the digital signature or MAC operation. This key can be identified using the Header Parameter methods as described in RFC 7515 section 4.1 or other methods outside the scope of RFC 7515. Based on this information, the recipient can obtain the corresponding public key certificate or certificate chain, which can be used to verify the digital signature of the access token.

[0074] In operation 7, the NFc requests service from the NFp and includes the obtained access token. In operation 8, the NFp verifies the access token integrity and certain claims within the access token. If successful, the NFp provides the requested service to the NFc in operation 9.

[0075] According to 3 GPP TS 33.501 (v!7.11.1) section 13.4.1.1.2, the NFp ensures the integrity of the access token by verifying the signature using NRF’s public key or by checking the MAC value using the shared secret. If integrity check is successful, the NF Service Producer shall verify certain claims in the token, as summarized below.

[0076] In the direct communication case, NFp checks that the NF Instance ID in the subject claim in the access token matches the NF Instance ID in the subjectAltName in the NFc’s transport layer security (TLS) client certificate. The NFp also verifies that the audience claim in the access token matches its own identity or the NF type of NFp. If a list of network slice selection assistance information (NSSAI) or list of network slice instance (NSI) IDs is present, the NFp verifies that it serves the corresponding slice(s). If the request is for information related to a specific UE, the NFp may check that the NFc is allowed to access (as indicated by NFp’s NSSAIs in the access token) at least one of the slice(s) that the UE is currently registered to, e.g., by verifying that the UE’s allowed NSSAI(s) intersect with the NFp's NSSAIs in the access token.

[0077] If an NF Set ID present, the NFp checks that the NF Set ID in the claim matches its own NF Set ID. If an NF Service Set ID present, the NFp checks whether the NFc is authorized to access the requested service according to NF Service Set ID in the access token claim.

[0078] If a scope claim is present, the NFp checks that the scope matches the requested service operation. If the access token contains "additional scope" information (e.g., allowed resources and allowed service operations on the resources), the NFp checks that the additional scope matches the requested service operation.

[0079] The NFp also checks that the access token has not expired by verifying the expiration in the access token against the current date / time. If client credentials assertion (CCA) is present in the service request, the NFp may verify the CCA as specified in 3GPP TS 33.501 (vl7.11.1) section 13.3.8.3 and that the subject claim (i.e., NF Instance Id of the NFc) in the access token matches the subject claim in the CCA.

[0080] However, 3 GPP TS 33.501 (v 17. 11.1) does not specify whether, nor how, an NFp verifies the issuer claim in the access token is legitimate. Without verifying the issuer claim, it is possible for an NFp to grant service access to the NFc based on an access token issued by an NRF that the NFp does not trust. For example, a malicious NFc may be able to trick an NFp to accept an access token that has not been signed by a legitimate NRF that the NFp trusts. In this manner, the NFc can obtain unauthorized access to a service of the NFp.

[0081] Also, there can be scenarios in which an access token request is received by a different NRF instance (e.g., NRF-2) than the NRF instance in which the NFp is registered (e.g., NRF-1), but the two NRF instances are part of the same NF set. In this scenario, it is unclear how the NFp should verify the issuer claim in the access token when it identifies a different NRF instance.

[0082] Embodiments of the present disclosure address these and other problems, issues, and / or difficulties by providing novel, flexible, and efficient techniques that enable an NFp to verify that a legitimate NRF issued an access token presented by an NFc. To summarize, the NFp receives an access token from an NFc, where the access token has been issued by an NRF identified by an issuer claim of the access token. The NFp first determines whether the NRF identified by the issuer claim is the same NRF to which the NFp has registered or is one of locally configured NRFs. If the first determination is negative, the NFp obtains NF Set ID of the NRF identified by the issuer claim from the access token claims or by requesting and receiving the NF Set ID from the identified NRF.

[0083] The NRF then determines whether the obtained NF Set ID (i.e., of the NRF identified by the issuer claim) is the same as the NF Set ID of the NRF to which the NFp registered, or the same as the NF Set ID of any of the locally configured NRFs. If this second determination is negative, the NFp considers the access token invalid for accessing the service requested by the NFc, and therefore does not grant the NFc access to the service. On the other hand, if either the first determination or the second determination is positive, the NFp considers the access token valid for accessing the service requested by the NFc, and therefore grants the NFc access to the service.

[0084] Embodiments may provide various benefits and / or advantages. For example, embodiments can facilitate a set of NRF instances to act as a single NRF, with one NRF instance signing access tokens on behalf of another NRF instance in the set. Moreover, this benefit is enabled without impacting an NFp’s ability to verify the legitimacy of an access token as basis for granting service access to a requesting NFc. At a high level, embodiments improve security of service access in a communication network, such as 5GC.

[0085] Figure 4 shows a signal flow diagram illustrating token-based authorization for access to NF services, according to embodiments of the present disclosure. Operations 1-3 are part of the NF Service registration procedure, similar to the registration procedure shown in operations 1-3 in Figure 3, in which the NFp (440) provides information about the NF Service to NRF-2 (430), which is a different NRF instance than an authorization server NRF-1 (420). NRF-2 stores this information in a profile for the NFp. The service information may identify the NFp’s resources and services that can be accessed by properly authorized NFc’s (e.g., NFc 410).

[0086] In some embodiments, the NFp may also be locally configured with a list of NRF instances and / or NRF sets, which are configured as valid and interchangeable OAuth 2.0 authorization servers for this NFp. The NFp obtains and stores the NF set ID of NRF-2, to which the NFp registered, or of any locally configured NRF instances. For example, the NFp may use Nnrf NFDiscovery service to get NF set information for the registering NRF (e.g., NRF-2 in Figure 4) from another NRF (e.g., NRF-1 or a locally configured NRF). Alternately, the NFp obtains NF set information from NRF-2, such as in a registration response (operation 3) or by using an Nnrf Bootstrapping service.

[0087] Operations 4-6 are similar to operations 4-6 in Figure 3. The NFc requests an access token for a service provided by the NFp from NRF-1, which checks whether the NFc is authorized to access the requested service and, when the NFc is authorized, generates an access token with appropriate claims included. According to embodiments of the present disclosure, NRF-1 may include its NF set information (e.g., NF set ID) in the generated access token. The authorization server NRF digitally signs the generated access token and sends it to the NFc.

[0088] In operation 7, the NFc requests service from the NFp and includes the obtained access token. In operation 8, the NFp verifies the access token integrity and certain claims within the access token, according to the following procedure:

[0089] • When the authorization server NRF identified by the issuer claim of the access token is the same NRF to which the NFp registered in operations 1-3, the NFp ensures the issuer NRF is valid and continues with the integrity check of the token based on security material associated with the issuer NRF. In the context of Figure 4, this condition would be met if the NFp registered with NRF-1 instead of NRF-2.

[0090] • When the authorization server NRF identified by the issuer claim of the access token is different than the NRF to which the NFp registered in operations 1-3, the NFp first determines whether the authorization server NRF is part of a locally configured (authorization server) NRF list. If this first determination is positive, the NFp ensures the issuer NRF is valid and continues with the integrity check of the token based on the security material associated with the issuer NRF.

[0091] • When the first determination is negative, the NFp obtains the NF set ID of the authorization server NRF (i.e., NRF-1). This information may be in the access token if NRF-1 included it in operation 5. Alternately, the NFp may use Nnrf NFDiscovery service to obtain NF set information for NRF-1 from another NRF (e.g., NRF-2 or a locally configured NRF), or use an Nnrf Bootstrapping service to obtain NF set information directly from NRF-1.

[0092] • When the NF set information for NRF-1 is available (i.e., can be obtained), the NFp compares it with the NF set information for NRF-2, to which the NFp registered, or the locally configured NRF set information (if available). If the compared NF Set information matches at least one of these, the NFp ensures the issuer NRF is valid and continues with the integrity check of the token based on the security material associated with the issuer NRF.

[0093] • When NF set information for the issuer NRF is not available or does not match either the NF set information for NRF-2, to which the NFp registered, or the locally configured NRF set information (if available), the NF Service Producer rejects the service request and sends the NFc and OAuth2.0 error response, as defined in IETF RFC 6749.

[0094] If the access token verification is successful according to any of the conditions described above, the NFp provides the requested service to the NFc in operation 9.

[0095] In the embodiments described above, the NFp can perform an integrity check according to the procedure specified in 3GPP TS 33.501 (v!7.11.1) section 13.4.1.1.2. The NFp can obtain the security material associated with the issuer NRF in various ways, such as manual configuration, during registration with NRF, or directly from the issuer NRF.

[0096] The embodiments described above can be further illustrated with reference to Figures 5-6, which depict exemplary methods (e.g, procedures) performed by an NFp and an NRF, respectively. Put differently, various features of the operations described below correspond to various embodiments described above. The exemplary methods shown in Figures 5-6 can be used cooperatively (e.g., with each other and with other procedures described herein) to provide benefits, advantages, and / or solutions to problems described herein. Although the exemplary methods are illustrated in Figures 5-6 by specific blocks in particular orders, the operations corresponding to the blocks can be performed in different orders than shown and can be combined and / or divided into blocks or operations having different functionality than shown. Optional blocks and / or operations are indicated by dashed lines.

[0097] In particular, Figure 5 illustrates an exemplary method (e.g, procedure) performed by a service producer network function (NFp) of a communication network (e.g., 5GC), according to various embodiments of the present disclosure. The exemplary method shown in Figure 5 can be performed by any appropriate NFp (or network equipment implementing the same) such as described elsewhere herein. As a specific example, the exemplary method can correspond to the operations performed by the NFp shown in Figure 4.

[0098] The exemplary method includes the operations of block 520, where the NFp receives, from a service consumer network function (NFc) of the communication network, a request for a service provided by the NFp. The request includes an access token issued by a first network repository function (NRF) of the communication network. The access token includes a network function (NF) identifier of the first NRF. The exemplary method also includes the operations of block 560, where the NFp verifies the access token in response to at least one of the following conditions:

[0099] • the first NRF corresponds to a second NRF with which the NFp previously registered;

[0100] • when the NFp stores a first list of NRFs authorized to provide access tokens for the service, the first NRF corresponds to any NRFs in the first list; and

[0101] • when the NFp stores a second list of NRF sets authorized to provide access tokens for the service, the first NRF corresponds to any NRF sets in the second list.

[0102] In some embodiments, the exemplary method also includes the following operations, labelled with corresponding block numbers:

[0103] • (530) determining whether the NF identifier of the first NRF matches at least one of the following NF identifiers: an NF identifier of the second NRF, and when the NFp stores the first list, an NF identifier of any NRFs in the first list; • (550) when the NF identifier of the first NRF does not match at least one of the NF identifiers, determining whether an NF set identifier associated with the first NRF is available and matches at least one of the following NF set identifiers: an NF set identifier associated with the second NRF, and when the NFp stores the second list, an NF set identifier of any NRF sets in the second list.

[0104] In such embodiments, verifying the access token is responsive to at least one of the following:

[0105] • the NF identifier of the first NRF matches at least one of the NF identifiers; and

[0106] • the NF set identifier associated with the first NRF is available and matches at least one of the NF set identifiers.

[0107] In some of these embodiments, the exemplary method also includes the operations of block 510, where the NFp registers the service provided by the NFp with the second NRF. At least one of the following is obtained by the NFp during the registration: the NF identifier of the second NRF, and the NF set identifier associated with the second NRF. In some variants, the NF identifier of the second NRF is obtained during the registration in block 510, and the NF set identifier associated with the second NRF is obtained from one of the following: a third NRF via an NRF discovery service, or the second NRF via an NRF bootstrapping service.

[0108] In some of these embodiments, the exemplary method also includes the operations of block 570, where the NFp refrains from verifying the access token and sending an error response to the NFc in response to the following:

[0109] • the NF identifier of the first NRF does not match at least one of the NF identifiers; and

[0110] • the NF set identifier associated with the first NRF is unavailable or does not match at least one of the NF set identifiers.

[0111] In some embodiments, the exemplary method also includes the operations of block 580, where when verification of the access token is successful in block 560, the NFp executes the requested service and sending a service response to the NFc.

[0112] In some embodiments, the exemplary method also includes the operations of block 540, where the NFp obtains the NF set identifier associated with the first NRF from one of the following: a field in the access token, a third NRF via an NRF discovery service, or the first NRF via an NRF bootstrapping service.

[0113] In some embodiments, the first and second NRFs are part of a single NRF set. In some embodiments, the communication network is a 5GC.

[0114] In addition, Figure 6 illustrates an exemplary method (e.g. , procedure) performed by a first network repository function (NRF) of a communication network (e.g., 5GC), according to various embodiments of the present disclosure. The exemplary method shown in Figure 6 can be performed by an NRF (or network equipment implementing the same) such as described elsewhere herein. As a specific example, the exemplary method can correspond to the operations performed by an authorization server NRF shown in Figure 4.

[0115] The exemplary method includes the operations of block 630, where the first NRF receives, from a service consumer network function (NFc) of the communication network, a request for an access token granting the NFc access to a service produced by an NFp of the communication network. The exemplary method also includes the operations of block 640, where the first NRF generates the requested access token based on determining that the NFc is authorized to access the service. A field of the generated access token includes an NF set identifier associated with the first NRF. The exemplary method also includes the operations of block 650, where the first NRF sends the access token to the NFc in accordance with the request.

[0116] In some embodiments, an NF identifier of the first NRF is different from an NF identifier of a second NRF with which the NFp registered. In some of these embodiments, the exemplary method can also include the operations of block 620, where using an NRF discovery service, the first NRF sends the NFp an NF set identifier associated with the second NRF.

[0117] In some embodiments, the exemplary method also includes the operations of block 610, where the first NRF registers the service provided by the NFp. At least one of the following is provided to the NFp during the registration: an NF identifier of the first NRF, and the NF set identifier associated with the first NRF.

[0118] In some embodiments, the first and second NRFs are part of a single NRF set. In some embodiments, the communication network is a 5G core network (5GC).

[0119] Although various embodiments are described herein above in terms of methods, apparatus, devices, computer-readable medium and receivers, the person of ordinary skill will readily comprehend that such methods can be embodied by various combinations of hardware and software in various systems, communication devices, computing devices, control devices, apparatuses, non-transitory computer-readable media, etc.

[0120] Figure 7 shows an example of a communication system 700 in accordance with some embodiments. In this example, communication system 700 includes a telecommunication network 702 that includes an access network 704 (e.g., RAN) and a core network 706, which includes one or more core network nodes 708. Access network 704 includes one or more access network nodes, such as network nodes 710A-B (one or more of which may be generally referred to as network nodes 710), or any other similar 3GPP access nodes or non-3GPP access points. Moreover, as will be appreciated by those of skill in the art, a network node is not necessarily limited to an implementation in which a radio portion and a baseband portion are supplied and integrated by a single vendor. Thus, it will be understood that network nodes include disaggregated implementations or portions thereof. For example, in some embodiments, telecommunication network 702 includes one or more Open-RAN (ORAN) network nodes. An ORAN network node is a node in telecommunication network 702 that supports an ORAN specification (e.g., a specification published by the O-RAN Alliance, or any similar organization) and may operate alone or together with other nodes to implement one or more functionalities of any node in telecommunication network 702, including one or more network nodes 710 and / or core network nodes 708.

[0121] Examples of an ORAN network node include an open radio unit (O-RU), an open distributed unit (O-DU), an open central unit (O-CU), including an O-CU control plane (O-CU- CP) or an O-CU user plane (O-CU-UP), a RAN intelligent controller (near-real time or non-real time) hosting software or software plug-ins, such as a near-real time control application (e.g., xApp) or a non-real time control application (e.g., rApp), or any combination thereof (the adj ective “open” designating support of an ORAN specification). The network node may support a specification by, for example, supporting an interface defined by the ORAN specification, such as an Al, Fl, Wl, El, E2, X2, Xn interface, an open fronthaul user plane interface, or an open fronthaul management plane interface. Moreover, an ORAN access node may be a logical node in a physical node. Furthermore, an ORAN network node may be implemented in a virtualization environment (described further below) in which one or more network functions are virtualized. For example, the virtualization environment may include an O-Cloud computing platform orchestrated by a Service Management and Orchestration Framework via an O-2 interface defined by the O-RAN Alliance or comparable technologies. Network nodes 710 facilitate direct or indirect connection of UEs, such as by connecting UEs 712A-D (one or more of which may be generally referred to as UEs 712) to core network 706 over one or more wireless connections.

[0122] Example wireless communications over a wireless connection include transmitting and / or receiving wireless signals using electromagnetic waves, radio waves, infrared waves, and / or other types of signals suitable for conveying information without the use of wires, cables, or other material conductors. Moreover, in different embodiments, communication system 700 may include any number of wired or wireless networks, network nodes, UEs, and / or any other components or systems that may facilitate or participate in the communication of data and / or signals whether via wired or wireless connections. Communication system 700 may include and / or interface with any type of communication, telecommunication, data, cellular, radio network, and / or other similar type of system.

[0123] UEs 712 may be any of a wide variety of communication devices, including wireless devices arranged, configured, and / or operable to communicate wirelessly with network nodes 710 and other communication devices. Similarly, network nodes 710 are arranged, capable, configured, and / or operable to communicate directly or indirectly with UEs 712 and / or with other network nodes or equipment in telecommunication network 702 to enable and / or provide network access, such as wireless network access, and / or to perform other functions, such as administration in telecommunication network 702.

[0124] In the depicted example, core network 706 connects network nodes 710 to one or more hosts, such as host 716. These connections may be direct or indirect via one or more intermediary networks or devices. In other examples, network nodes may be directly coupled to hosts. Core network 706 includes one or more core network nodes (e.g., 708) that are structured with hardware and software components. Features of these components may be substantially similar to those described with respect to the UEs, network nodes, and / or hosts, such that the descriptions thereof are generally applicable to the corresponding components of core network node 708. Example core network nodes include functions of one or more of a Mobile Switching Center (MSC), Mobility Management Entity (MME), Home Subscriber Server (HSS), Access and Mobility Management Function (AMF), Session Management Function (SMF), Authentication Server Function (AUSF), Subscription Identifier De-concealing function (SIDF), Unified Data Management (UDM), Security Edge Protection Proxy (SEPP), Network Repository Function (NRF), and / or a User Plane Function (UPF).

[0125] Host 716 may be under the ownership or control of a service provider other than an operator or provider of access network 704 and / or telecommunication network 702 and may be operated by the service provider or on behalf of the service provider. Host 716 may host a variety of applications to provide one or more service. Examples of such applications include live and pre-recorded audio / video content, data collection services such as retrieving and compiling data on various ambient conditions detected by a plurality of UEs, analytics functionality, social media, functions for controlling or otherwise interacting with remote devices, functions for an alarm and surveillance center, or any other such function performed by a server.

[0126] As a whole, communication system 700 of Figure 7 enables connectivity between the UEs, network nodes, and hosts. In that sense, the communication system may be configured to operate according to predefined rules or procedures, such as specific standards that include, but are not limited to: Global System for Mobile Communications (GSM); Universal Mobile Telecommunications System (UMTS); Long Term Evolution (LTE), and / or other suitable 2G, 3G, 4G, 5G standards, or any applicable future generation standard (e.g., 6G); wireless local area network (WLAN) standards, such as the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards (WiFi); and / or any other appropriate wireless communication standard, such as the Worldwide Interoperability for Microwave Access (WiMax), Bluetooth, Z-Wave, Near Field Communication (NFC) ZigBee, LiFi, and / or any low-power wide-area network (LPWAN) standards such as LoRa and Sigfox. In some examples, telecommunication network 702 is a cellular network that implements 3GPP standardized features. Accordingly, telecommunication network 702 may support network slicing to provide different logical networks to different devices that are connected to telecommunication network 702. For example, telecommunication network 702 may provide Ultra Reliable Low Latency Communication (URLLC) services to some UEs, while providing Enhanced Mobile Broadband (eMBB) services to other UEs, and / or Massive Machine Type Communication (mMTC)ZMassive loT services to yet further UEs.

[0127] In some examples, UEs 712 are configured to transmit and / or receive information without direct human interaction. For instance, a UE may be designed to transmit information to access network 704 on a predetermined schedule, when triggered by an internal or external event, or in response to requests from access network 704. Additionally, a UE may be configured for operating in single- or multi-RAT or multi-standard mode. For example, a UE may operate with any one or combination of Wi-Fi, NR (New Radio) and LTE, i.e. being configured for multi -radio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN-DC).

[0128] In the example, hub 714 communicates with access network 704 to facilitate indirect communication between one or more UEs (e.g., UE 712C and / or 712D) and network nodes (e.g., network node 710B). In some examples, hub 714 may be a controller, router, content source and analytics, or any of the other communication devices described herein regarding UEs. For example, hub 714 may be a broadband router enabling access to core network 706 for the UEs. As another example, hub 714 may be a controller that sends commands or instructions to one or more actuators in the UEs. Commands or instructions may be received from the UEs, network nodes 710, or by executable code, script, process, or other instructions in hub 714. As another example, hub 714 may be a data collector that acts as temporary storage for UE data and, in some embodiments, may perform analysis or other processing of the data. As another example, hub 714 may be a content source. For example, for a UE that is a VR headset, display, loudspeaker or other media delivery device, hub 714 may retrieve VR assets, video, audio, or other media or data related to sensory information via a network node, which hub 714 then provides to the UE either directly, after performing local processing, and / or after adding additional local content. In still another example, hub 714 acts as a proxy server or orchestrator for the UEs, in particular if one or more of the UEs are low energy loT devices.

[0129] Hub 714 may have a constant / persistent or intermittent connection to network node 710B. Hub 714 may also allow for a different communication scheme and / or schedule between hub 714 and UEs (e.g., UE 712C and / or 712D), and between hub 714 and core network 706. In other examples, hub 714 is connected to core network 706 and / or one or more UEs via a wired connection. Moreover, hub 714 may be configured to connect to an M2M service provider over access network 704 and / or to another UE over a direct connection. In some scenarios, UEs may establish a wireless connection with network nodes 710 while still connected via hub 714 via a wired or wireless connection. In some embodiments, hub 714 may be a dedicated hub - that is, a hub whose primary function is to route communications to / from the UEs from / to network node 71 OB. In other embodiments, hub 714 may be a non-dedicated hub - that is, a device which is capable of operating to route communications between the UEs and network node 71 OB, but which is additionally capable of operating as a communication start and / or end point for certain data channels.

[0130] Figure 8 shows a network node 800 in accordance with some embodiments. Examples of network nodes include, but are not limited to, access points (APs) (e.g., radio access points), base stations (e.g., radio base stations, Node Bs, eNBs, gNBs), and O-RAN nodes or components of an O-RAN node (e g., O-RU, O-DU, O-CU).

[0131] Base stations may be categorized based on the amount of coverage they provide (or, stated differently, their transmit power level) and so, depending on the provided amount of coverage, may be referred to as femto base stations, pico base stations, micro base stations, or macro base stations. A base station may be a relay node or a relay donor node controlling a relay. A network node may also include one or more (or all) parts of a distributed radio base station such as centralized digital units, distributed units (e.g., in an O-RAN access node) and / or remote radio units (RRUs), sometimes referred to as Remote Radio Heads (RRHs). Such remote radio units may or may not be integrated with an antenna as an antenna integrated radio. Parts of a distributed radio base station may also be referred to as nodes in a distributed antenna system (DAS).

[0132] Other examples of network nodes include multiple transmission point (multi-TRP) 5G access nodes, multi-standard radio (MSR) equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, multi-cell / multicast coordination entities (MCEs), Operation and Maintenance (O&M) nodes, Operations Support System (OSS) nodes, Self-Organizing Network (SON) nodes, positioning nodes (e.g., Evolved Serving Mobile Location Centers (E-SMLCs)), and / or Minimization of Drive Tests (MDTs).

[0133] For example, one or more network nodes 800 can be configured to implement an NFp and / or an NRF of a communication network, including performing operations attributed to these NFs in the descriptions herein of various methods or procedures.

[0134] Network node 800 includes a processing circuitry 802, a memory 804, a communication interface 806, and a power source 808. Network node 800 may be composed of multiple physically separate components (e.g., a NodeB component and a RNC component, or a BTS component and a BSC component, etc.), which may each have their own respective components. In certain scenarios in which network node 800 comprises multiple separate components (e.g., BTS and BSC components), one or more of the separate components may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, network node 800 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memory 804 for different RATs) and some components may be reused (e.g., a same antenna 810 may be shared by different RATs). Network node 800 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 800, for example GSM, WCDMA, LTE, NR, WiFi, Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 800.

[0135] The processing circuitry 802 may comprise a combination of one or more of a microprocessor, controller, microcontroller, central processing unit, digital signal processor, application-specific integrated circuit, field programmable gate array, or any other suitable computing device, resource, or combination of hardware, software and / or encoded logic operable to provide, either alone or in conjunction with other network node 800 components, such as memory 804, to provide network node 800 functionality.

[0136] In some embodiments, the processing circuitry 802 includes a system on a chip (SOC). In some embodiments, the processing circuitry 802 includes one or more of radio frequency (RF) transceiver circuitry 812 and baseband processing circuitry 814. In some embodiments, RF transceiver circuitry 812 and baseband processing circuitry 814 may be on separate chips (or sets of chips), boards, or units, such as radio units and digital units. In alternative embodiments, part or all of RF transceiver circuitry 812 and baseband processing circuitry 814 may be on the same chip or set of chips, boards, or units.

[0137] Memory 804 may comprise any form of volatile or non-volatile computer-readable memory including, without limitation, persistent storage, solid-state memory, remotely mounted memory, magnetic media, optical media, random access memory (RAM), read-only memory (ROM), mass storage media (for example, a hard disk), removable storage media (for example, a flash drive, a Compact Disk (CD) or a Digital Video Disk (DVD)), and / or any other volatile or non-volatile, non-transitory device-readable and / or computer-executable memory devices that store information, data, and / or instructions that may be used by the processing circuitry 802. Memory 804 may store any suitable instructions, data, or information, including a computer program, software, an application including one or more of logic, rules, code, tables, and / or other instructions (collected denoted computer program 804a, which may be in the form of a computer program product) capable of being executed by the processing circuitry 802 and utilized by network node 800. Memory 804 may be used to store any calculations made by the processing circuitry 802 and / or any data received via communication interface 806. In some embodiments, the processing circuitry 802 and memory 804 is integrated.

[0138] Communication interface 806 is used in wired or wireless communication of signaling and / or data between a network node, access network, and / or UE. As illustrated, communication interface 806 comprises port(s) / terminal(s) 816 to send and receive data, for example to and from a network over a wired connection. Communication interface 806 also includes radio front-end circuitry 818 that may be coupled to, or in certain embodiments a part of, antenna 810. Radio front-end circuitry 818 comprises filters 820 and amplifiers 822. Radio front-end circuitry 818 may be connected to an antenna 810 and processing circuitry 802. The radio front-end circuitry may be configured to condition signals communicated between antenna 810 and processing circuitry 802. Radio front-end circuitry 818 may receive digital data that is to be sent out to other network nodes or UEs via a wireless connection. Radio front-end circuitry 818 may convert the digital data into a radio signal having the appropriate channel and bandwidth parameters using a combination of filters 820 and / or amplifiers 822. The radio signal may then be transmitted via antenna 810. Similarly, when receiving data, antenna 810 may collect radio signals which are then converted into digital data by radio front-end circuitry 818. The digital data may be passed to the processing circuitry 802. In other embodiments, the communication interface may comprise different components and / or different combinations of components.

[0139] In certain alternative embodiments, network node 800 does not include separate radio front-end circuitry 818, instead, the processing circuitry 802 includes radio front-end circuitry and is connected to antenna 810. Similarly, in some embodiments, all or some of RF transceiver circuitry 812 is part of communication interface 806. In still other embodiments, communication interface 806 includes one or more ports or terminals 816, radio front-end circuitry 818, and RF transceiver circuitry 812, as part of a radio unit (not shown), and communication interface 806 communicates with baseband processing circuitry 814, which is part of a digital unit (not shown).

[0140] Antenna 810 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. Antenna 810 may be coupled to radio front-end circuitry 818 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, antenna 810 is separate from network node 800 and connectable to network node 800 through an interface or port. Antenna 810, communication interface 806, and / or the processing circuitry 802 may be configured to perform any receiving operations and / or certain obtaining operations described herein as being performed by the network node. Any information, data and / or signals may be received from a UE, another network node and / or any other network equipment. Similarly, antenna 810, communication interface 806, and / or the processing circuitry 802 may be configured to perform any transmitting operations described herein as being performed by the network node. Any information, data and / or signals may be transmitted to a UE, another network node and / or any other network equipment.

[0141] Power source 808 provides power to the various components of network node 800 in a form suitable for the respective components (e.g., at a voltage and current level needed for each respective component). Power source 808 may further comprise, or be coupled to, power management circuitry to supply the components of network node 800 with power for performing the functionality described herein. For example, network node 800 may be connectable to an external power source (e.g., the power grid, an electricity outlet) via an input circuitry or interface such as an electrical cable, whereby the external power source supplies power to power circuitry of power source 808. As a further example, power source 808 may comprise a source of power in the form of a battery or battery pack which is connected to, or integrated in, power circuitry. The battery may provide backup power should the external power source fail.

[0142] Embodiments of network node 800 may include additional components beyond those shown in Figure 8 for providing certain aspects of the network node’s functionality, including any of the functionality described herein and / or any functionality necessary to support the subject matter described herein. For example, network node 800 may include user interface equipment to allow input of information into network node 800 and to allow output of information from network node 800. This may allow a user to perform diagnostic, maintenance, repair, and other administrative functions for network node 800.

[0143] Figure 9 is a block diagram illustrating a virtualization environment 900 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to any device described herein, or components thereof, and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components. Some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines (VMs) implemented in virtual environment 900 hosted by network equipment, such as a hardware computing device that operates as a network node, UE, core network node, or host. Further, in embodiments in which the virtual node does not require radio connectivity (e.g., a core network node or host), then the node may be entirely virtualized. In some embodiments, the virtualization environment 900 includes components defined by the O- RAN Alliance, such as an O-Cloud environment orchestrated by a Service Management and Orchestration Framework via an 0-2 interface.

[0144] Applications 902 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) are run in the virtualization environment 900 to implement some of the features, functions, and / or benefits of some of the embodiments disclosed herein.

[0145] For example, various NFs (or portions thereof) described herein in relation to other figures can be implemented as virtual network functions 902 in virtualization environment 900. As a more specific example, a service producer NF (NFp) and anNRF can be implemented as virtual network functions 902 in virtualization environment 900.

[0146] Hardware 904 includes processing circuitry, memory that stores software and / or instructions (collected denoted computer program 904a, which may be in the form of a computer program product) executable by hardware processing circuitry, and / or other hardware devices as described herein, such as a network interface, input / output interface, and so forth. Software may be executed by the processing circuitry to instantiate one or more virtualization layers 906 (also referred to as hypervisors or virtual machine monitors (VMMs)), provide VMs 908a and 908b (one or more of which may be generally referred to as VMs 908), and / or perform any of the functions, features and / or benefits described in relation with some embodiments described herein. Virtualization layer 906 may present a virtual operating platform that appears like networking hardware to the VMs 908.

[0147] VMs 908 comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 906. Different embodiments of the instance of a virtual appliance 902 may be implemented on one or more of VMs 908, and the implementations may be made in different ways. Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

[0148] In the context of NFV, each VM 908 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each VM 908, and that part of hardware 904 that executes that VM, be it hardware dedicated to that VM and / or hardware shared by that VM with others of the VMs, forms separate virtual network elements. Still in the context of NFV, a virtual network function is responsible for handling specific network functions that run in one or more VMs 908 on top of the hardware 904 and corresponds to the application 902.

[0149] Hardware 904 may be implemented in a standalone network node with generic or specific components. Hardware 904 may implement some functions via virtualization. Alternatively, hardware 904 may be part of a larger cluster of hardware (e.g. such as in a data center or CPE) where many hardware nodes work together and are managed via management and orchestration function 910, which, among others, oversees lifecycle management of applications 902. In some embodiments, hardware 904 is coupled to one or more radio units that each include one or more transmitters and one or more receivers that may be coupled to one or more antennas. Radio units may communicate directly with other hardware nodes via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station. In some embodiments, some signaling can be provided with the use of a control system 912 which may alternatively be used for communication between hardware nodes and radio units.

[0150] The foregoing merely illustrates the principles of the disclosure. Various modifications and alterations to the described embodiments will be apparent to those skilled in the art in view of the teachings herein. It will thus be appreciated that those skilled in the art will be able to devise numerous systems, arrangements, and procedures that, although not explicitly shown or described herein, embody the principles of the disclosure and can be thus within the spirit and scope of the disclosure. Various embodiments can be used together with one another, as well as interchangeably therewith, as should be understood by those having ordinary skill in the art.

[0151] The term unit, as used herein, can have conventional meaning in the field of electronics, electrical devices and / or electronic devices and can include, for example, electrical and / or electronic circuitry, devices, modules, processors, memories, logic solid state and / or discrete devices, computer programs or instructions for carrying out respective tasks, procedures, computations, outputs, and / or displaying functions, and so on, as such as those that are described herein.

[0152] Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and / or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according to one or more embodiments of the present disclosure.

[0153] As described herein, device and / or apparatus can be represented by a semiconductor chip, a chipset, or a (hardware) module comprising such chip or chipset; this, however, does not exclude the possibility that a functionality of a device or apparatus, instead of being hardware implemented, be implemented as a software module such as a computer program or a computer program product comprising executable software code portions for execution or being run on a processor. Furthermore, functionality of a device or apparatus can be implemented by any combination of hardware and software. A device or apparatus can also be regarded as an assembly of multiple devices and / or apparatuses, whether functionally in cooperation with or independently of each other. Moreover, devices and apparatuses can be implemented in a distributed fashion throughout a system, so long as the functionality of the device or apparatus is preserved. Such and similar principles are considered as known to a skilled person.

[0154] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0155] In addition, certain terms used in the present disclosure, including the specification and drawings, can be used synonymously in certain instances (e.g., “data” and “information”). It should be understood, that although these terms (and / or other terms that can be synonymous to one another) can be used synonymously herein, there can be instances when such words can be intended to not be used synonymously.

[0156] Embodiments of the techniques and apparatus described herein also include, but are not limited to, the following enumerated examples:

[0157] Al . A method for a service producer network function (NFp) of a communication network, the method comprising: receiving, from a service consumer network function (NFc) of the communication network, a request for a service provided by the NFp, wherein: the request includes an access token issued by a first network repository function (NRF) of the communication network, and the access token includes a network function (NF) identifier of the first NRF; and verifying the access token in response to at least one of the following conditions: the first NRF corresponds to a second NRF with which the NFp previously registered; when the NFp stores a first list of NRFs authorized to provide access tokens for the service, the first NRF corresponds to any NRFs in the first list; and when the NFp stores a second list of NRF sets authorized to provide access tokens for the service, the first NRF corresponds to any NRF sets in the second list.

[0158] Ala. The method of embodiment Al, further comprising: determining whether the NF identifier of the first NRF matches at least one of the following NF identifiers: an NF identifier of the second NRF, and when the NFp stores the first list, an NF identifier of any NRFs in the first list; when the NF identifier of the first NRF does not match at least one of the NF identifiers, determining whether an NF set identifier associated with the first NRF is available and matches at least one of the following NF set identifiers: an NF set identifier associated with the second NRF, and when the NFp stores the second list, an NF set identifier of any NRF sets in the second list, wherein verifying the access token is responsive to at least one of the following: the NF identifier of the first NRF matches at least one of the NF identifiers; and the NF set identifier associated with the first NRF is available and matches at least one of the NF set identifiers.

[0159] A2. The method of embodiment Ala, further comprising registering the service provided by the NFp with the second NRF, wherein at least one of the following is obtained during the registration: the NF identifier of the second NRF, and the NF set identifier associated with the second NRF.

[0160] A3. The method of embodiment A2, wherein the NF identifier of the second NRF is obtained during the registration, and the NF set identifier associated with the second NRF is obtained from one of the following: a third NRF via an NRF discovery service, or the second NRF via an NRF bootstrapping service.

[0161] A4. The method of any of embodiments Al a- A3, further comprising refraining from verifying the access token and sending an error response to the NFc in response to the following: the NF identifier of the first NRF does not match at least one of the NF identifiers; and the NF set identifier associated with the first NRF is unavailable or does not match at least one of the NF set identifiers.

[0162] A5. The method of any of embodiments A1-A4, further comprising, when verification of the access token is successful, executing the requested service and sending a service response to the NFc.

[0163] A6. The method of any of embodiments A1-A5, further comprising obtaining the NF set identifier associated with the first NRF from one of the following: a field in the access token, a third NRF via an NRF discovery service, or the first NRF via an NRF bootstrapping service.

[0164] A7. The method of any of embodiments A1-A6, wherein the first and second NRFs are part of a single NRF set.

[0165] A8. The method of any of embodiments A1-A7, wherein the communication network is a 5G core network (5GC).

[0166] Bl . A method for a first network repository function (NRF) of a communication network, the method comprising: receiving, from a service consumer network function (NFc) of the communication network, a request for an access token granting the NFc access to a service provided by a service production network function (NFp) of the communication network; generating the requested access token based on determining that the NFc is authorized to access the service, wherein a field of the generated access token includes a network function (NF) set identifier associated with the first NRF; and sending the access token to the NFc in accordance with the request. B2. The method of embodiment Bl, wherein an NF identifier of the first NRF is different from an NF identifier of a second NRF with which the NFp registered.

[0167] B3. The method of embodiment B2, further comprising using an NRF discovery service, sending the NFp an NF set identifier associated with the second NRF.

[0168] B4. The method of embodiment Bl, further comprising registering the service provided by the NFp, wherein at least one of the following is provided to the NFp during the registration: an NF identifier of the first NRF, and the NF set identifier associated with the first NRF.

[0169] B5. The method of any of embodiments B1-B4, wherein the first and second NRFs are part of a single NRF set.

[0170] B6. The method of any of embodiments B1-B5, wherein the communication network is a 5G core network (5GC).

[0171] Cl . Network equipment configured to implement a service producer network function (NFp) of a communication network, the network equipment comprising: communication interface circuitry configured to communicate with other network functions (NFs) of the communication network; and processing circuitry operably coupled to the communication interface circuitry, whereby the processing circuitry and interface circuitry are configured to perform operations corresponding to the method of any of claims A1-A8.

[0172] C2. Network equipment configured to implement a service producer network function (NFp) of a communication network, the network equipment being further configured to perform operations corresponding to any of the methods of embodiments A1-A8.

[0173] C3. A non-transitory, computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of network equipment configured to implement a service producer network function (NFp) of a communication network, configure the network equipment to perform operations corresponding to any of the methods of embodiments A1-A8. C4. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of network equipment configured to implement a service producer network function (NFp) of a communication network, configure the network equipment to perform operations corresponding to any of the methods of embodiments A1-A8.

[0174] DI . Network equipment configured to implement a network repository function (NRF) of a communication network, the network equipment comprising: communication interface circuitry configured to communicate with other network functions (NFs) of the communication network; and processing circuitry operably coupled to the communication interface circuitry, whereby the processing circuitry and interface circuitry are configured to perform operations corresponding to the method of any of claims B1-B6.

[0175] D2. Network equipment configured to implement a network repository function (NRF) of a communication network, the network equipment being further configured to perform operations corresponding to any of the methods of embodiments B1-B6.

[0176] D3. A non-transitory, computer-readable medium storing computer-executable instructions that, when executed by processing circuitry of network equipment configured to implement a network repository function (NRF) of a communication network, configure the network equipment to perform operations corresponding to any of the methods of embodiments B1-B6.

[0177] D4. A computer program product comprising computer-executable instructions that, when executed by processing circuitry of network equipment configured to a network repository function (NRF) of a communication network, configure the network equipment to perform operations corresponding to any of the methods of embodiments B1-B6.

Claims

CLAIMS1. A method for a service producer network function, NFp, of a communication network, the method comprising: receiving (520), from a service consumer network function, NFc, of the communication network, a request for a service provided by the NFp, wherein: the request includes an access token issued by a first network repository function, NRF, of the communication network, and the access token includes a network function, NF, identifier of the first NRF; and verifying (560) the access token in response to at least one of the following conditions: the first NRF corresponds to a second NRF with which the NFp previously registered; when the NFp stores a first list of NRFs authorized to provide access tokens for the service, the first NRF corresponds to any NRFs in the first list; and when the NFp stores a second list of NRF sets authorized to provide access tokens for the service, the first NRF corresponds to any NRF sets in the second list.

2. The method of claim 1, further comprising: determining (530) whether the NF identifier of the first NRF matches at least one of the following NF identifiers: an NF identifier of the second NRF, and when the NFp stores the first list, an NF identifier of any NRFs in the first list; when the NF identifier of the first NRF does not match at least one of the NF identifiers, determining (550) whether an NF set identifier associated with the first NRF is available and matches at least one of the following NF set identifiers: an NF set identifier associated with the second NRF, and when the NFp stores the second list, an NF set identifier of any NRF sets in the second list, wherein verifying the access token is responsive to at least one of the following:31RECTIFIED SHEET (RULE 91) ISA / EPthe NF identifier of the first NRF matches at least one of the NF identifiers; and the NF set identifier associated with the first NRF is available and matches at least one of the NF set identifiers.

3. The method of claim 2, further comprising registering (510) the service provided by the NFp with the second NRF, wherein at least one of the follow ing is obtained during the registration: the NF identifier of the second NRF, and the NF set identifier associated with the second NRF.

4. The method of claim 3, wherein the NF identifier of the second NRF is obtained during the registration, and the NF set identifier associated with the second NRF is obtained from one of the following: a third NRF via an NRF discovery service, or the second NRF via an NRF bootstrapping service.

5. The method of any of claims 2 - 4, further comprising refraining (570) from verifying the access token and sending an error response to the NFc in response to the following: the NF identifier of the first NRF does not match at least one of the NF identifiers; and the NF set identifier associated with the first NRF is unavailable or does not match at least one of the NF set identifiers.

6. The method of any of claims 1-5, further comprising, when verification of the access token is successful, executing (580) the requested service and sending a service response to the NFc.

7. The method of any of claims 1 -6, further comprising obtaining the NF set identifier associated with the first NRF from one of the following: a field in the access token, a third NRF via an NRF discovery service, or the first NRF via an NRF bootstrapping service.

8. The method of any of claims 1-7, wherein the first and second NRFs are part of a single NRF set.32RECTIFIED SHEET (RULE 91) ISA / EP9. The method of any of claims 1-8, wherein the communication network is a 5G core network (5GC).

10. A method for a first network repository function (NRF) of a communication network, the method comprising: receiving (630), from a service consumer network function (NFc) of the communication network, a request for an access token granting the NFc access to a service provided by a service production network function (NFp) of the communication network; generating (640) the requested access token based on determining that the NFc is authorized to access the service, wherein a field of the generated access token includes a network function (NF) set identifier associated with the first NRF; and sending (650) the access token to the NFc in accordance with the request.

11. The method of claim 10, wherein an NF identifier of the first NRF is different from an NF identifier of a second NRF with which the NFp registered.

12. The method of claim 11, further comprising using (620) an NRF discovery service, sending the NFp an NF set identifier associated with the second NRF.

13. The method of claim 10, further comprising registering (610) the service provided by the NFp, wherein at least one of the following is provided to the NFp during the registration: an NF identifier of the first NRF, and the NF set identifier associated with the first NRF.

14. The method of any of claims 10-13, wherein the first and second NRFs are part of a single NRF set.

15. The method of any of claims 10-14, wherein the communication network is a 5G core network (5GC).33RECTIFIED SHEET (RULE 91) ISA / EP16. Network equipment (708, 800, 900) configured to implement a service producer network function (NFp) (440, 902) of a communication network (198, 200, 702), the network equipment comprising: communication interface circuitry (806, 904) configured to communicate with other network functions (NFs) of the communication network; and processing circuitry (802, 904) operably coupled to the communication interface circuitry, whereby the processing circuitry and interface circuitry are configured to perform operations corresponding to: receive (520), from a service consumer network function, NFc (410, 902), of the communication network, a request for a service provided by the NFp, wherein: the request includes an access token issued by a first network repository function, NRF (420, 902), of the communication network, and the access token includes a network function, NF, identifier of the first NRF; and verify (560) the access token in response to at least one of the following conditions: the first NRF corresponds to a second NRF (430, 902) with which the NFp previously registered; when the NFp stores a first list of NRFs authorized to provide access tokens for the service, the first NRF corresponds to any NRFs in the first list; and when the NFp stores a second list of NRF sets authorized to provide access tokens for the service, the first NRF corresponds to any NRF sets in the second list.

17. Network equipment of claim 16, wherein the communication interface circuitry and the processing circuitry are further configured to perform operations corresponding to any of the methods of claims 2-9.

18. Network equipment (708, 800, 900) configured to implement a service producer network function (NFp) (440, 902) of a communication network (198, 200, 702), the network equipment being further configured to:34RECTIFIED SHEET (RULE 91) ISA / EPreceive (520), from a service consumer network function, NFc (410, 902), of the communication network, a request for a service provided by the NF , wherein: the request includes an access token issued by a first network repository function, NRF (420, 902), of the communication network, and the access token includes a network function, NF, identifier of the first NRF; and verify (560) the access token in response to at least one of the following conditions: the first NRF corresponds to a second NRF (430, 902) with which the NFp previously registered; when the NFp stores a first hst of NRFs authorized to provide access tokens for the service, the first NRF corresponds to any NRFs in the first hst; and when the NFp stores a second list of NRF sets authorized to provide access tokens for the service, the first NRF corresponds to any NRF sets in the second list.

19. Network equipment of claim 18, being further configured to perform operations corresponding to any of the methods of claims 2-9.

20. A non-transitory, computer-readable medium (804, 904) storing computer-executable instructions that, when executed by processing circuitry (802, 904) of network equipment configured to implement a service producer network function (NFp) (440, 902) of a communication network (198, 200, 702), configure the network equipment to perform operations corresponding to any of the methods of claims 1-9.21 . A computer program product (804a, 904a) comprising computer-executable instructions that, when executed by processing circuitry (802, 904) of network equipment configured to implement a service producer network function (NFp) (440, 902) of a communication network, configure the network equipment to perform operations corresponding to any of the methods of claims 1-9.35RECTIFIED SHEET (RULE 91) ISA / EP22. Network equipment (708, 800, 900) configured to implement a network repository function (NRF) (420, 902) of a communication network (198, 200, 702), the network equipment comprising: communication interface circuitry' configured to communicate with other network functions (NFs) of the communication network, and processing circuitry operably coupled to the communication interface circuitry, whereby the processing circuitry and interface circuitry are configured to: receive (630), from a service consumer network function (NFc) (410, 902) of the communication network, a request for an access token granting the NFc access to a service provided by a service production network function (NFp) (440, 902) of the communication network; generate (640) the requested access token based on determining that the NFc is authorized to access the service, wherein a field of the generated access token includes a network function (NF) set identifier associated with the first NRF; and send (650) the access token to the NFc in accordance with the request.

23. Network equipment of claim 22, wherein the processing circuitry and the communication interface circuitry are further configured to perform operations corresponding to any of the methods of claims 11-15.

24. Network equipment (708, 800, 900) configured to implement a network repository function (NRF) (420, 902) of a communication network (198, 200, 702), the network equipment being further configured to: receive (630), from a service consumer network function (NFc) (410, 902) of the communication network, a request for an access token granting the NFc access to a service provided by a service production network function (NFp) (440, 902) of the communication network; generate (640) the requested access token based on determining that the NFc is authorized to access the service, wherein a field of the generated access token includes a network function (NF) set identifier associated with the first NRF; and send (650) the access token to the NFc in accordance with the request.36RECTIFIED SHEET (RULE 91) ISA / EP25. Network equipment of claim 24, being further configured to perform operations corresponding to any of the methods of claims 11-15.

26. A non-transitory, computer-readable medium (804, 904) storing computer-executable instructions that, when executed by processing circuitry (802, 904) of network equipment configured to implement a network repository function (NRF) (420, 902) of a communication network (198, 200, 702), configure the network equipment to perform operations corresponding to any of the methods of claims 10-15.

27. A computer program product (804a, 904a) comprising computer-executable instructions that, when executed by processing circuitry (802, 904) of network equipment configured to implement a network repository function (NRF) (420, 902) of a communication network (198, 200, 702), configure the network equipment to perform operations corresponding to any of the methods of claims 10-15.RECTIFIED SHEET (RULE 91) ISA / EP

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