EP4690878A1

EP4690878A1 - Method and apparatus for routing a notification

Info

Publication number: EP4690878A1
Application number: EP24802743.5A
Authority: EP
Inventors: Yunjie Lu; Lin JIN
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2023-05-11
Filing date: 2024-04-19
Publication date: 2026-02-11
Also published as: WO2024230458A1; CN121080008A

Abstract

Various embodiments of the present disclosure provide a method for routing a notification. The method which may be performed by a first network node comprises: transmitting, to a second network node in a first network, a message for registering first routing information for routing an inter-network notification towards the first network node in a default notification subscription of the first network node's profile in the second network node. In accordance with an exemplary embodiment, the method further comprises: receiving a notification from a fourth network node in a second network based on the first routing information.

Description

METHOD AND APPARATUS FOR ROUTING A NOTIFICATION

PRIORITY CLAIM
This application claims the priority of PCT application No. PCT/CN2023/093468, filed on May 11, 2023, the disclosure of which is incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present disclosure generally relates to communication networks, and more specifically, to a method and apparatus for routing a notification.

BACKGROUND

This section introduces aspects that may facilitate a better understanding of the disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
With the rapid development of networking and communication technologies, wireless communication networks such as long-term evolution (LTE) /fourth generation (4G) network and new radio (NR) /fifth generation (5G) network are expected to achieve enhanced transmission efficiency and service performance. In order to meet the diverse requirements of new services across a wide variety of industries, the 3rd generation partnership project (3GPP) is developing various network function (NF) services for the communication system architecture (e.g., 5G system (5GS) architecture, etc. ) . The service-based architecture (SBA) under development for the next generation network can restructure the core network control plane and divide it into multiple independent modules with decoupled functions that can be updated individually. The introduction of the service-based interface protocols and network-function repository function (NRF) may enable the function modules to be used flexibly. In the SBA, service discovery may be provided for individual network functions (NFs) by an NRF, so as to meet different service requirements. By using the service discovery, an NF service producer may obtain subscription information of an NF service consumer from an NRF and send a notification to the NF service consumer according to the subscription information. Considering the diversity of NF capabilities and application scenarios (e.g., whether to support roaming or not, within a network or across different networks, etc. ) , routing a notification from an NF service producer towards an NF service consumer may become more challenging.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
An NF service consumer (e.g., an access and mobility management function (AMF) , etc. ) may register default notification subscriptions in its NF profile or NF services in an NRF for notifications that the NF service consumer is prepared to consume. The default notification subscriptions may indicate for each type of notification a corresponding notification endpoint such as a callback uniform resource identifier (URI) . This callback URI may be used as routing information by an NF service producer (e.g., a network slice-specific authentication and authorization function (NSSAAF) , etc. ) to send a notification to the NF service consumer. Currently, only one callback URI attribute may be provided per notification type by an NF service consumer. In actual application scenarios, there are several notification types, and most are for intra-network notifications while there are still some for inter-network notifications. However, most of the time, the intra-network notification and the inter-network notification cannot share one callback URI due to different hypertext transfer protocol (HTTP) transmission mechanisms, network prefixes and/or authorities, e.g., as defined in chapter 5.2.3.3.7 “3gpp-Sbi-Consumer-Info” of 3GPP technical specification (TS) 29.500 V18.1.0.
intraPlmnCallbackRoot = "intraPlmnCallbackRoot=" OWS scheme ": //" authority [prefix]
interPlmnCallbackRoot = "interPlmnCallbackRoot=" OWS scheme ": //" authority [prefix]
scheme = "http" / "https"
authority = host [ ": " port]
port = *DIGIT
prefix = path-absolute.
Therefore, only one URI cannot be applicable for both intra-network and inter-network notifications.
When the NF service consumer supports both intra-PLMN and inter-PLMN scenarios (e.g., the AMF serving a user equipment (UE) supports the roaming functionality and network slice-specific authentication and authorization (NSSAA) , etc. ) , then for the inter-PLMN scenario where the NF service consumer and an NF service producer are located in different PLMNs, there is no routing information specific for the inter-PLMN scenarios to be provided to receive a notification from the NF service producer. It may lead that the notification from the NF service producer cannot be sent to the NF service consumer. Alternatively, if it is required to make the current callback URI attribute work for both intra-PLMN and inter-PLMN scenarios, very complicated configurations (e.g., configurations for a domain name server (DNS) , policies in security edge protection proxies (SEPPs) , etc. ) have to be made, which will lead to increasing operating expense (OPEX) . Therefore, it may be desirable to perform routing of notifications for an NF service consumer in an easily implemented way.
Various exemplary embodiments of the present disclosure propose a solution for routing a notification, which can enable an NF service consumer to provide routing information (e.g., a URI, etc. ) for an inter-network scenario, so that for a NF service producer located in a different network from the NF service consumer, the NF service producer may be able to send an inter-network notification to the NF service consumer by using the routing information for the inter-network scenario.
It can be appreciated that the term “intra-network notification” used herein may refer to a notification to be communicated within a network, and the term “inter-network notification” used herein may refer to a notification to be communicated across different networks. As an example, for an NF service consumer in a first network, an intra-network notification may refer to a notification transmitted by an NF service producer in the first network, while an inter-network notification may refer to a notification transmitted by an NF service producer in a second network.
Similarly, it can be appreciated that the term “intra-network routing” used herein may refer to routing within a network, and the term “inter-network routing” used herein may refer to routing across different networks. When an NF service consumer and an NF service producer are located in the same network (e.g., a PLMN, etc. ) , intra-network routing information may be used by the NF service producer to send an intra-network notification towards the NF service consumer. When an NF service consumer and an NF service producer are located in different networks (e.g., a home PLMN (HPLMN) and a visited PLMN (VPLMN) , etc. ) , inter-network routing information may be used by the NF service producer to send an inter-network notification towards the NF service consumer.
In addition, it also can be appreciated that although some exemplary embodiments are described with respect to URI or callback URI, the same principle may also be applied to other suitable routing information (e.g., network resource identification information and/or location information, etc. ) that may enable an NF (e.g., an NF service producer, etc. ) to send a notification towards another NF (e.g., an NF service consumer, etc. ) .
It can be realized that the expression like “a node receives a notification transmitted by another node” or “a node receives a notification from another node” used herein means a node receiving a notification from another node directly or via one or more intermediate nodes. Similarly, the expression like “a node transmits a notification towards/to another node” used herein means a node transmitting a notification towards/to another node directly or via one or more intermediate nodes.
According to a first aspect of the present disclosure, there is provided a method performed by a first network node (e.g., an NF service consumer such as an AMF, etc. ) . The method comprises: transmitting, to a second network node in a first network, a message for registering first routing information for routing an inter-network notification towards the first network node in a default notification subscription of the first network node’s profile in the second network node. In accordance with an exemplary embodiment, the method further comprises: receiving a notification from a fourth network node in a second network based on the first routing information.
In accordance with an exemplary embodiment, the message may be further for registering second routing information for routing a notification towards the first network node in the default notification subscription of the first network node’s profile in the second network node. The second routing information may be different from the first routing information. In an embodiment, the second routing information may be for routing an intra-network notification towards the first network node.
In accordance with an exemplary embodiment, the first network node may be configured to act as an NF service consumer supporting a roaming functionality. In accordance with another exemplary embodiment, the second network node may be configured to act as a repository for registering NF information of the first network node.
In accordance with an exemplary embodiment, the first network node may be in the first network. In an embodiment, the first routing information may indicate a first URI for receiving the inter-network notification transmitted by an NF service producer in the second network. In another embodiment, the second routing information may indicate a second URI for receiving the intra-network notification transmitted by an NF service producer in the first network.
In accordance with an exemplary embodiment, the first URI and the second URI may have a same path part, and the first routing information may include a root part of the first URI and a root part of the second URI.
In accordance with an exemplary embodiment, the first routing information may include the first URI.
In accordance with an exemplary embodiment, the first routing information may include a map based on a URI per network. For the second network different from the first network, the map may indicate a URI for receiving the inter-network notification transmitted by an NF service producer in the second network.
In accordance with an exemplary embodiment, for one or more networks different from the first network, the map may indicate one or more URIs associated with the one or more networks according to HTTP schemes and/or authorities and/or prefixes of the one or more URIs.
In accordance with an exemplary embodiment, the first routing information may be included in a type of notification subscription for an NF profile and/or an NF service of the first network node.
In accordance with an exemplary embodiment, the first network node may be configured to implement an AMF. In accordance with another exemplary embodiment, the second network node may be configured to implement an NRF.
According to a second aspect of the present disclosure, there is provided an apparatus which may be implemented as a first network node. The apparatus may comprise one or more processors and one or more memories storing computer program codes. The one or more memories and the computer program codes may be configured to, with the one or more processors, cause the apparatus at least to perform any step of the method according to the first aspect of the present disclosure.
According to a third aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the first aspect of the present disclosure.
According to a fourth aspect of the present disclosure, there is provided an apparatus which may be implemented as a first network node. The apparatus may comprise a transmitting unit and a receiving unit. In accordance with some exemplary embodiments, the transmitting unit may be operable to carry out at least the transmitting step of the method according to the first aspect of the present disclosure. The receiving unit may be operable to carry out at least the receiving step of the method according to the first aspect of the present disclosure.
According to a fifth aspect of the present disclosure, there is provided a method performed by a second network node (e.g., an NRF, etc. ) . The method comprises: receiving a message transmitted by a first network node (e.g., an AMF, etc. ) for registering first routing information for routing an inter-network notification towards the first network node in a default notification subscription of the first network node’s profile in the second network node. In accordance with an exemplary embodiment, the method further comprises: registering the first routing information according to the message.
In accordance with an exemplary embodiment, the message may be further for registering second routing information for routing a notification towards the first network node in the default notification subscription of the first network node’s profile in the second network node. The second routing information may be different from the first routing information. In an embodiment, the second routing information may be for routing an intra-network notification towards the first network node.
In accordance with an exemplary embodiment, the message received by the second network node according to the fifth aspect of the present disclosure may correspond to the message transmitted by the first network node according to the first aspect of the present disclosure. Thus, the first routing information included in the message according to the first and fifth aspects of the present disclosure may have the same or similar contents and/or feature elements. Similarly, the second routing information included in the message according to the first and fifth aspects of the present disclosure may have the same or similar contents and/or feature elements.
In accordance with an exemplary embodiment, the first network node may be configured to act as an NF service consumer supporting a roaming functionality. In accordance with another exemplary embodiment, the second network node may be configured to act as a repository for registering NF information of the first network node.
In accordance with an exemplary embodiment, when the second network node is in a first network, the method according to the fifth aspect of the present disclosure may further comprise: receiving a message for discovering the first network node transmitted by a third network node in a second network. In accordance with another exemplary embodiment, the method according to the fifth aspect of the present disclosure may further comprise: transmitting a response including the first routing information towards the third network node. In an embodiment, the third network node may be configured to implement an NRF.
In accordance with an exemplary embodiment, the first routing information may be included in a type of notification subscription for an NF profile and/or an NF service of the first network node.
According to a sixth aspect of the present disclosure, there is provided an apparatus which may be implemented as a second network node. The apparatus may comprise one or more processors and one or more memories storing computer program codes. The one or more memories and the computer program codes may be configured to, with the one or more processors, cause the apparatus at least to perform any step of the method according to the fifth aspect of the present disclosure.
According to a seventh aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the fifth aspect of the present disclosure.
According to an eighth aspect of the present disclosure, there is provided an apparatus which may be implemented as a second network node. The apparatus may comprise a receiving unit and a registering unit. In accordance with some exemplary embodiments, the receiving unit may be operable to carry out at least the receiving step of the method according to the fifth aspect of the present disclosure. The registering unit may be operable to carry out at least the registering step of the method according to the fifth aspect of the present disclosure.
According to a ninth aspect of the present disclosure, there is provided a method performed by a third network node (e.g., an NRF, etc. ) . The method comprises: receiving a message transmitted by a fourth network node (e.g., an NSSAAF, etc. ) for discovering a first network node (e.g., an AMF, etc. ) . In accordance with an exemplary embodiment, the method further comprises: transmitting a response towards the fourth network node. The response may include a profile of the first network node including a default notification subscription, and the default notification subscription may include first routing information for routing an inter-network notification towards the first network node.
In accordance with an exemplary embodiment, the default notification subscription may further include second routing information for routing a notification towards the first network node. The second routing information may be different from the first routing information. In an embodiment, the second routing information may be for routing an intra-network notification towards the first network node.
In accordance with an exemplary embodiment, the first routing information according to the ninth aspect of the present disclosure may correspond to the first routing information according to the first and fifth aspects of the present disclosure. Thus, the first routing information according to the first, fifth and ninth aspects of the present disclosure may have the same or similar contents and/or feature elements.
In accordance with another exemplary embodiment, the second routing information according to the ninth aspect of the present disclosure may correspond to the second routing information according to the first and fifth aspects of the present disclosure. Thus, the second routing information according to the first, fifth and ninth aspects of the present disclosure may have the same or similar contents and/or feature elements.
In accordance with an exemplary embodiment, the first network node may be configured to act as an NF service consumer supporting a roaming functionality. In accordance with another exemplary embodiment, the third network node may be configured to act as a repository for registering NF information of the first network node. In accordance with yet another exemplary embodiment, the fourth network node may be configured to act as an NF service producer.
In accordance with an exemplary embodiment, when the third network node and the fourth network node are in a second network, the method according to the ninth aspect of the present disclosure may further comprise: transmitting a message for discovering the first network node towards a second network node (e.g., an NRF, etc. ) in a first network. The first network node may be registered in the second network node. In accordance with another exemplary embodiment, the method according to the ninth aspect of the present disclosure may further comprise: receiving a response including the first routing information transmitted by the second network node.
In accordance with an exemplary embodiment, the first routing information may be included in a type of notification subscription for an NF profile and/or an NF service of the first network node.
In accordance with an exemplary embodiment, the third network node may be configured to implement an NRF. In accordance with another exemplary embodiment, the fourth network node may be configured to implement an NSSAAF.
According to a tenth aspect of the present disclosure, there is provided an apparatus which may be implemented as a third network node. The apparatus may comprise one or more processors and one or more memories storing computer program codes. The one or more memories and the computer program codes may be configured to, with the one or more processors, cause the apparatus at least to perform any step of the method according to the ninth aspect of the present disclosure.
According to an eleventh aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the ninth aspect of the present disclosure.
According to a twelfth aspect of the present disclosure, there is provided an apparatus which may be implemented as a third network node. The apparatus may comprise a receiving unit and a transmitting unit. In accordance with some exemplary embodiments, the receiving unit may be operable to carry out at least the receiving step of the method according to the ninth aspect of the present disclosure. The transmitting unit may be operable to carry out at least the transmitting step of the method according to the ninth aspect of the present disclosure.
According to a thirteenth aspect of the present disclosure, there is provided a method performed by a fourth network node (e.g., an NF service producer such as an NSSAAF, etc. ) . The method comprises: transmitting a message for discovering a first network node (e.g., an NF service consumer such as an AMF, etc. ) towards a third network node (e.g., an NRF, etc. ) . In accordance with an exemplary embodiment, the method further comprises: receiving a response transmitted by the third network node. The response may include a profile of the first network node including a default notification subscription, and the default notification subscription may include first routing information for routing an inter-network notification towards the first network node.
In accordance with an exemplary embodiment, the default notification subscription may further include second routing information for routing a notification towards the first network node. The second routing information may be different from the first routing information. In an embodiment, the second routing information may be for routing an intra-network notification towards the first network node.
In accordance with an exemplary embodiment, the response received by the fourth network node according to the thirteenth aspect of the present disclosure may correspond to the response transmitted by the third network node according to the ninth aspect of the present disclosure. Thus, the first routing information included in the response according to the ninth and thirteenth aspects of the present disclosure may have the same or similar contents and/or feature elements. Similarly, the second routing information included in the response according to the ninth and thirteenth aspects of the present disclosure may have the same or similar contents and/or feature elements.
In accordance with an exemplary embodiment, the first network node may be configured to act as an NF service consumer supporting a roaming functionality. In accordance with another exemplary embodiment, the third network node may be configured to act as a repository for registering NF information of the first network node. In accordance with another exemplary embodiment, the fourth network node may be configured to act as an NF service producer.
In accordance with an exemplary embodiment, when the first network node is in a first network and the fourth network node is in a second network, the method according to the thirteenth aspect of the present disclosure may further comprise: determining a URI based at least in part on the first routing information. In an embodiment, the method according to the thirteenth aspect of the present disclosure may further comprise: transmitting a notification towards the first network node according to the determined URI.
In accordance with an exemplary embodiment, the fourth network node may determine the URI based at least in part on the first routing information by determining a root part of the URI according to the first routing information and a path part of the URI according to the first routing information and the second routing information.
In accordance with an exemplary embodiment, the fourth network node may determine the URI based at least in part on the first routing information by reading the URI indicated by the first routing information.
In accordance with an exemplary embodiment, the fourth network node may determine the URI based at least in part on the first routing information by retrieving the URI in the first routing information according to an identifier of the second network.
In accordance with an exemplary embodiment, the first routing information may be included in a type of notification subscription for an NF profile and/or an NF service of the first network node.
According to a fourteenth aspect of the present disclosure, there is provided an apparatus which may be implemented as a fourth network node. The apparatus may comprise one or more processors and one or more memories storing computer program codes. The one or more memories and the computer program codes may be configured to, with the one or more processors, cause the apparatus at least to perform any step of the method according to the thirteenth aspect of the present disclosure.
According to a fifteenth aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the thirteenth aspect of the present disclosure.
According to a sixteenth aspect of the present disclosure, there is provided an apparatus which may be implemented as a fourth network node. The apparatus may comprise a transmitting unit and a receiving unit. In accordance with some exemplary embodiments, the transmitting unit may be operable to carry out at least the transmitting step of the method according to the thirteenth aspect of the present disclosure. The receiving unit may be operable to carry out at least the receiving step of the method according to the thirteenth aspect of the present disclosure.
According to various exemplary embodiments, a first network node (e.g., an NF service consumer such as an AMF, etc. ) may register its notification subscription including inter-network routing information in a second network node (e.g., an NRF in a first network, etc. ) . The inter-network routing information may be provided, via a third network node (e.g., an NRF in a second network, etc. ) , to a fourth network node (e.g., an NF service producer such as an NSSAAF, etc. ) , e.g., when the fourth network node is in the second network. As such, the fourth network node may be able to send an inter-network notification to the first network node in the first network according to the inter-routing information. This can enhance the efficiency of notification routing towards an NF service consumer, e.g., especially for an inter-network routing scenario.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure itself, the preferable mode of use and further objectives are best understood by reference to the following detailed description of the embodiments when read in conjunction with the accompanying drawings, in which:
Fig. 1A is a diagram illustrating an exemplary re-authentication notification procedure according to an embodiment of the present disclosure;
Fig. 1B is a diagram illustrating an exemplary revocation notification procedure according to an embodiment of the present disclosure;
Fig. 1C is a diagram illustrating an exemplary authentication, authorization and accounting (AAA) server triggered slice-specific authorization revocation procedure according to an embodiment of the present disclosure;
Figs. 2-5 are flowcharts illustrating various methods according to some embodiments of the present disclosure;
Fig. 6 is a block diagram illustrating an apparatus according to an embodiment of the present disclosure; and
Figs. 7A-7D are block diagrams illustrating various apparatus according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

The embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the present disclosure, rather than suggesting any limitations on the scope of the present disclosure. Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present disclosure should be or are in any single embodiment of the disclosure. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Furthermore, the described features, advantages, and characteristics of the disclosure may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the disclosure may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the disclosure.
As used herein, the term “communication network” refers to a network following any suitable communication standards, such as new radio (NR) , long term evolution (LTE) , LTE-Advanced, wideband code division multiple access (WCDMA) , high-speed packet access (HSPA) , and so on. Furthermore, the communications between a terminal device and a network node in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , 4G, 4.5G, 5G communication protocols, and/or any other protocols either currently known or to be developed in the future.
As used herein, the terms “first” , “second” and so forth refer to different elements. The singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises” , “comprising” , “has” , “having” , “includes” and/or “including” as used herein, specify the presence of stated features, elements, and/or components and the like, but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof. The term “based on” is to be read as “based at least in part on” . The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment” . The term “another embodiment” is to be read as “at least one other embodiment” . Other definitions, explicit and implicit, may be included below.
There may be end-to-end interactions between two NFs (e.g., an NF service consumer and an NF service producer) within an NF service framework. An NF may include the default notification information when performing an NF registration procedure. As described in chapter 7.1.2 of 3GPP technical specification (TS) 23.501 V18.1.0, an NF service consumer may add a binding indication in a subscribe request, which may be used by an NF service producer to discover a suitable notification endpoint. The subscription for notification may be done with an explicit subscription, an implicit subscription or a default notification endpoint. The default notification endpoint may correspond to a registration of a notification endpoint for each type of notification the NF service consumer is interested to receive, as an NF service parameter with an NRF during an NF and NF service registration procedure as specified in clause 4.17.1 of 3GPP TS 23.502 V18.1.1.
According to the contents in chapter 6.10.5.2 of 3GPP TS 29.500 V18.1.0, an NF may register default notification subscriptions in its NF profile or NF services in an NRF for notifications the NF is prepared to consume, including for each type of notification a corresponding notification endpoint (i.e. callback URI) . This can be used e.g. by an AMF to discover the notification endpoint of other AMFs to forward N1 or N2 messages, or by an AMF to notify location information to a gateway mobile location center (GMLC) , or by a unified data repository (UDR) to notify data change or removal to a unified data management (UDM) . An NF service producer may perform a discovery request towards the NRF to discover default notification subscriptions of an NF service consumer, and send notifications to the corresponding notification endpoints, e.g., by using routing mechanisms specified in clause 6.10.2/6.10.2A of 3GPP TS 29.500 V18.1.0. As an example, Table 1 lists two attributes notificationType and callbackUri in the type of DefaultNotificationSubscription, and the detailed definition of the type of DefaultNotificationSubscription may be found in chapter 6.1.6.2.4 of 3GPP TS 29.510 V18.2.0.
Table 1
Regarding the callback URI, as mentioned in chapter 4.4.3 of 3GPP TS 29.501 V18.1.0, the purpose of the callback URI is to enable an NF service consumer to provide the URI to be used by an NF service producer to send notification or callback requests. The callback URI may need to be in the form of an absolute URI as defined in clause 4.3 of Internet Engineering Task Force (IETF) Requests for Comments (RFC) 3986, including an authority, and excluding any query component, any fragment component and any user information subcomponent. Therefore, the callback URI may consist of the following components, specified with Augmented Backus-Naur Form (ABNF) syntax (see IETF RFC 5234) :
URI = scheme ": " "//" host [ ": " port] /pathwhere 'host'is either a fully qualified domain name (FQDN) or an Internet protocol (IP) address and the 'path'is a path to an NF consumer resource.
In addition, NF services may support some HTTP custom headers such as "3gpp-Sbi-Consumer-Info" . As described in chapter 5.2.3.3.7 of 3GPP TS 29.500 V18.1.0, the header "3gpp-Sbi-Consumer-Info" may contain a comma-delimited list of NF service consumer information from an HTTP client (as NF service consumer) . The encoding of the header may follow the ABNF as defined in IETF RFC 7230. Some optional parameters and examples with respect to "3gpp-Sbi-Consumer-Info" are listed below.
intraPlmnCallbackRoot = "intraPlmnCallbackRoot=" OWS scheme ": //" authority [prefix]
interPlmnCallbackRoot = "interPlmnCallbackRoot=" OWS scheme ": //" authority [prefix]
scheme = "http" / "https"
authority = host [ ": " port]
port = *DIGIT
prefix = path-absolute ; path-absolute production rule from IETF RFC 3986, clause 3.3
Optional parameter. intra plmn callback root and inter plmn callback root supported by the sender as NF service consumer.
callback-uri-prefix= "callback-uri-prefix=" OWS path-absolute; path-absolute production rule from IETF RFC 3986, clause 3.3.
Optional parameter. The NF service consumer may include this parameter when providing a Callback URI when the authority part of the Callback URI is shared by several NF service consumer instances.
……
EXAMPLE 5: The NF consumer supports Namf_EventExposure OpenAPI "v1" and sends intra PLMN callback root "https: //operator. com" and inter PLMN callback root "https: //5gc. mnc012. mcc345.3gppnetwork. org" in the header:
3gpp-Sbi-Consumer-Info: service=namf-evts; apiversion= (1) ;
intraPlmnCallbackRoot= https%3A%2F%2Foperator. com; interPlmnCallbackRoot=https%3A%2F%2F5gc. mnc012. mcc345.3gppnetwork. org
Regarding routing across PLMN, as described in chapter 6.1.4.3.1of 3GPP TS 29.500 V18.1.0, in order to reach the correct target NF service in the right PLMN and for HTTP/2 request messages where the target URI authority component designates an origin server not in the same PLMN as a client, the ": authority" HTTP/2 pseudo-header may need to contain the FQDN including the PLMN identifier (ID) . The ": authority" pseudo-header field in the HTTP/2 request message may be set to: ": authority" = uri-host [ ": " port] as specified in clause 8.1.2.3 of IETF RFC 7540, excluding the [userinfo "@"] information as specified in clause 3.2 of IETF RFC 3986, where the uri-host may need to be the FQDN of the target NF service or the FQDN (authority) part of a callback URI or a specified link relation. The FQDN of the target NF service or the FQDN (authority) part of a callback URI or a specified link relation may need to contain the PLMN ID.
According to 3GPP TS 23.502 V18.1.1, an NSSAA procedure may be triggered for single-network slice selection assistance information (S-NSSAI) requiring NSSAA with a AAA server (AAA-S) . In the NSSAA procedure, an NSSAAF may discover a callback URI of an AMF for slice-specific re-authorization and revocation via an NRF (in a default notification subscription registered by the AMF in its NF profile) . For example, the NSSAAF may discover the callback URI of the AMF to revoke the authorized S-NSSAI with slice-specific authentication and authorization (AA) . In the AAA server triggered network slice-specific re-authentication and re-authorization procedure as specified in chapter 4.2.9.3 of 3GPP TS 23.502 V18.1.1, if the AMF is registered in a UDM, the NSSAAF may notify the AMF to re-authenticate/re-authorize the S-NSSAI for a UE using Nnssaaf_NSSAA_Re-AuthNotification with the generic public subscription identifier (GPSI) and S-NSSAI in the received AAA message. The callback URI of the notification for the AMF may be derived via NRF as specified in 3GPP TS 29.501 V18.1.0. Similarly, in the AAA server triggered slice-specific authorization revocation procedure as specified in chapter 4.2.9.4 of 3GPP TS 23.502 V18.1.1, if the AMF is registered in UDM, the NSSAAF may notify the AMF to revoke the S-NSSAI authorization for the UE using Nnssaaf_NSSAA_RevocationNotification with the GPSI and S-NSSAI in the received AAA message. The callback URI of the notification for the AMF may be derived via NRF as specified in 3GPP TS 29.501 V18.1.0.
In order to allow the NSSAAF to discover the callback URI, the AMF may register the default notification subscription with the corresponding notification type, as listed in Table 2 (which corresponds to part of Table 6.1.6.3.4-1 in chapter 6.1.6.3.4 of 3GPP TS 29.510 V18.2.0) .
Table 2
For NSSAA re-authorization or revocation scenarios, a UE may locate in a H-PLMN or in a V-PLMN, i.e., an NSSAAF may need to invoke a callback URI of an AMF located in the same PLMN (H-PLMN) or in another PLMN (V-PLMN) . However, currently the default notification subscription only allows one callback URI, and thus it may not be secured that the callback URI can be accessible for both intra-PLMN and inter-PLMN scenarios. In addition, as the format of the callback URI is not specified in 3GPP, different prefixes may be used in inter-PLMN and intra-PLMN callback URIs and an NF service producer may not be able to determine a prefix (if any) in a callback URI. It may be recommended that an NF can register a complete inter-PLMN callback URI in the default notification subscription.
In order to address one or more issues mentioned above, various exemplary embodiments of the present disclosure propose solutions to enhance intra/inter-network routing for notifications (e.g., default notifications towards an NF service consumer, etc. ) . In accordance with an exemplary embodiment, an NF service consumer in a PLMN may register inter-PLMN routing information in the default notification subscriptions of its NF profile or NF services. As such, when an NF service producer in another PLMN wants to send a notification to the NF service consumer, the NF service producer can use the inter-PLMN routing information to construct a URI for the notification and route a notification request to the NF service consumer, e.g., in the AAA server triggered network slice-specific re-authentication and re-authorization procedure as described in chapter 4.2.9.3 of 3GPP TS 23.502 V18.1.1, or in the AAA server triggered slice-specific authorization revocation procedure as described in chapter 4.2.9.4 of 3GPP TS 23.502 V18.1.1, or in any other procedures in which the inter-PLMN routing information may be needed by the NF service producer to send a notification to the NF service consumer.
In accordance with an exemplary embodiment, a new information element (IE) may be added in the DefaultNotificationSubscription data type to carry an inter-PLMN callback URI. As such, S-NSSAI subject to NSSAA may be re-authorized or revoked for roaming UEs. Table 3 exemplarily illustrates a definition of the DefaultNotificationSubscription type with a new attribute "interPlmnCallbackUri" (e.g., compared to the current definition of the DefaultNotificationSubscription type as specified in Table 6.1.6.2.4-1 of 3GPP TS 29.510 V18.2.0) .
Table 3
In accordance with an exemplary embodiment, some backward compatible modifications may be introduced to Nnrf_NFManagement and/or Nnrf_NFDiscovery API (s) , so as to update the corresponding OpenAPI accordingly. In an embodiment, the Nnrf_NFManagement API may be updated by adding the interPlmnCallbackUri related contents (see the underlined part) as below:
Application of the exemplary embodiments may enable an NSSAAF (e.g., in a HPLMN) to use an inter-PLMN callback URI available for an AMF (e.g., in a VPLMN) to route an inter-network notification, when the NSSAAF fetches the default notification subscription of the AMF via an NRF.
Fig. 1A is a diagram illustrating an exemplary re-authentication notification procedure according to an embodiment of the present disclosure. The re-authentication notification service operation may be used by an NSSAAF to notify an AMF to re-initiate slice-specific authentication and authorization for a given UE, e.g., as specified in clause 4.2.9.3 of 3GPP TS 23.502 V18.1.1, and clause 16.4 of 3GPP TS 33.501 V18.1.0. If there are two different AMFs serving the UE (e.g., the NSSAAF retrieves two different AMFs from a UDM) , the NSSAAF may determine to send a re-authentication notification to both AMFs. Or, the NSSAAF may first send the re-authentication notification to one of the AMF, and then send the revocation notification to another AMF if extensible authentication protocol (EAP) authentication fails in the AMF. If the EAP authentication succeeds in the AMF, then the NSSAAF may not notify the other AMF.
Upon receiving the network slice-specific re-authentication and re-authorization from an AAA-S, the NSSAAF may need to verify whether the AAA-Sis authorized to request the procedure, by checking its local configuration. If the AAA-Sis authorized to request the re-authentication, the NSSAAF may notify an NF service consumer (e.g., the AMF) by using the HTTP POST method as shown in Fig. 1A with the following steps:
1. The NSSAAF may send a POST request to a callback URI used to receive a re-authentication notification, which may be either provided by the NF service consumer (e.g., the AMF) , or retrieved from the AMF profile stored in an NRF (in default notification subscription for "NSSAA_REAUTH_NOTIFICATION" notification type) . If the NF service consumer is located in a VPLMN, the NSSAAF may use an inter-PLMN callback URI if registered in the default notification subscription. The HTTP payload body of the POST request may contain a SliceAuthReauthNotification data structure, within which:
- the notificationType set to the SliceAuthNotificationType of "SLICE_RE_AUTH" ;
- the gpsi set to the GPSI of the given UE required to be re-authenticated;
- the snssai set to the S-NSSAI required to be re-authenticated;
- the supi set to the SUPI of the given UE required to be re-authenticated.
NOTE: The NSSAAF can obtain the SUPI of the UE in the response of a previous Nudm_UECM_Get used by the NSSAAF to retrieve the AMF ID.
2a. On success, "204 No Content" may be returned and the payload body of the POST response may be empty.
After responding the request, the NF service consumer (e.g., the AMF) may send a non-access stratum (NAS) message to the UE to trigger re-authentication and re-authorization for the given slice.
The AMF then may decide to execute the slice-specific authentication and authorization if needed (e.g., as described in clause 5.2.2.2.1 of 3GPP TS 29.526 V17.6.0) .
If the S-NSSAI is not in the Mapping Of Allowed NSSAI, the AMF may remove any status of the corresponding S-NSSAI subject to slice-specific authentication and authorization in the UE context it may have kept, so that a slice-specific authentication and authorization procedure may be executed next time the UE requests to register with the S-NSSAI.
2b. On failure, one of the HTTP status codes (e.g., "404 Not Found" ) listed in Table 6.1.7.3-1 of 3GPP TS 29.526 V17.6.0 may be returned.
For a 4xx/5xx response, the message body may contain a ProblemDetails structure with the "cause" attribute set to one of the application errors listed in Table 6.1.7.3-1 of 3GPP TS 29.526 V17.6.0.
2c. On redirection, the appropriate HTTP status code (e.g., "307 Temporary Redirect" ) may be returned. A RedirectResponse IE may be included in the payload body of the POST response, e.g., as specified in Table 6.1.5.2.3.1-2 of 3GPP TS 29.526 V17.6.0.
If the NF service consumer (e.g., the AMF) is not able to handle the request, but knows that another NF service consumer (e.g., another AMF) is able to handle it, it may reply with an HTTP 3xx redirect response pointing to the URI of the new NF service consumer (e.g., the another AMF) .
Fig. 1B is a diagram illustrating an exemplary revocation notification procedure according to an embodiment of the present disclosure. The revocation notification service operation may be used by an NSSAAF to notify an AMF to revoke slice-specific authentication and authorization result for a given UE, e.g., as specified in clause 4.2.9.4 of 3GPP TS 23.502 V18.1.1 and clause 16.5 of 3GPP TS 33.501 V18.1.0, and may trigger the AMF to release the corresponding protocol data unit (PDU) sessions associated to the indicated slice. If there are two different AMFs serving the UE (e.g., the NSSAAF retrieves two different AMFs from the UDM) , the NSSAAF may determine to send a revocation notification to both AMFs.
Upon receiving the network slice-specific authorization revocation from an AAA-S, the NSSAAF may need to verify whether the AAA-Sis authorized to request the procedure, by checking its local configuration. If the AAA-Sis authorized to request the revocation, the NSSAAF may notify an NF service consumer (e.g., the AMF) by using the HTTP POST method as shown in Fig. 1B with the following steps:
1. The NSSAAF may send a POST request to a revocation notification callback URI, which may be either provided by the NF service consumer (e.g., the AMF) , or retrieved from the AMF profile stored in an NRF (in default notification subscription for "NSSAA_REVOC_NOTIFICATION" notification type) . If the NF service consumer is located in a VPLMN, the NSSAAF may use an inter-PLMN callback URI if registered in the default notification subscription.
The HTTP payload body of the POST request may contain a SliceAuthRevocNotification data structure, within which:
- the notificationType set to the SliceAuthNotificationType of "SLICE_REVOCATION" ;
- the gpsi set to the GPSI of the given UE for whom the slice-specific authorization revocation is required;
- the snssai set to the S-NSSAI for which the slice-specific authorization revocation is required;
- the supi set to the SUPI of the given UE for whom the slice-specific authorization revocation is required.
NOTE: The NSSAAF can obtain the SUPI of the UE in the response of a previous Nudm_UECM_Get used by the NSSAAF to retrieve the AMF ID.
2a. On success, "204 No Content" may be returned and the payload body of the POST response may be empty.
On receiving the request, the NF service consumer (e.g., the AMF) may revoke the slice-specific authentication and authorization result for the given UE. If there is a PDU session associated to the given slice, the AMF may trigger the PDU session release to the SMF, with an appropriate cause value.
The AMF may remove the "status" for the given slice in "nssaaStatusList" attribute (e.g., as specified in 3GPP TS 29.518 V18.1.0) .
2b. On failure, one of the HTTP status codes (e.g., "404 Not Found" ) listed in Table 6.1.7.3-1 of 3GPP TS 29.526 V17.6.0 may be returned.
For a 4xx/5xx response, the message body may contain a ProblemDetails structure with the "cause" attribute set to one of the application errors listed in Table 6.1.7.3-1 of 3GPP TS 29.526 V17.6.0.
2c. On redirection, the appropriate HTTP status code (e.g., "307 Temporary Redirect" ) may be returned. A RedirectResponse IE may be included in the payload body of the POST response, e.g., as specified in Table 6.1.5.3.3.1-2 of 3GPP TS 29.526 V17.6.0.
If the NF service consumer (e.g., the AMF) is not able to handle the request, but knows that another NF service consumer (e.g., another AMF) is able to handle it, it may reply with an HTTP 3xx redirect response pointing to the URI of the new NF service consumer (e.g., the another AMF) .
In accordance with an exemplary embodiment, an AMF may register callback URIs for both inter-PLMN and inter-PLMN scenarios in the default notification subscription. If an NSSAAF is in the same PLMN as the AMF, the intra-PLMN callback URI may be used, and if the NSSAAF and the AMF are in different PLMNs, the NSSAAF may use the inter-PLMN callback URI (if available) . For example, in the procedures as illustrated in Fig. 1A and Fig. 1B, the NSSAAF may select, from the callback URIs for intra-PLMN and inter-PLMN accesses registered in the default notification subscription by the AMF, a proper callback URI for slice re-authorization or revocation. By using different callback URIs, the NSSAAF may send notifications to AMFs in the same PLMN or in a different PLMN, e.g., depending on whether a UE is in a HPLMN or in a VPLMN when NSSAA happens.
It can be appreciated that in addition to an inter-PLMN callback URI in a full form (e.g., including a root part and a path part, etc. ) , the AMF may register the inter-PLMN callback URI in other alternative variants. For example, the AMF may register an inter-PLMN callback root and an intra-PLMN callback URI/prefix, and in this case the NSSAAF may compose the inter-PLMN callback URI by using the roots information about the inter-PLMN callback URI and the intra-PLMN callback URI.
In accordance with exemplary embodiments, the following approaches may be used to provide inter-network routing information (e.g., an inter-PLMN callback URI, etc. ) on different granularities for different deployment scenarios.
● Alternative I: Providing both intraPlmnCallbackRoot and interPlmnCallbackRoot attributes in the type of DefaultNotificationSubscription.
The formats of the intraPlmnCallbackRoot and interPlmnCallbackRoot attributes may be:
scheme ": //" authority [prefix] .
An NF service producer may use the InterPlmnCallbackRoot to replace the intraPlmnCallbackRoot part of the callbackUri attribute to build the inter-PLMN callback URI, where the remaining path part of the callbackUri attribute may be reused for the inter-PLMN routing.
Table 4 lists exemplary attributes notificationType, callbackUri, intraPlmnCallbackRoot and interPlmnCallbackRoot in the type of DefaultNotificationSubscription.
Table 4
● Alternative II: Providing an interPlmnCallbackUri attribute co-existing with the callbackUri attribute in the type of DefaultNotificationSubscription.
The format of the interPlmnCallbackUri attribute may be:
URI = scheme ": " "//" host [ ": " port] /path
For the inter-PLMN routing, the NF service producer may use this inter-PLMN callback URI directly to send a notification request.
Table 5 lists exemplary attributes notificationType, callbackUri and interPlmnCallbackUri in the type of DefaultNotificationSubscription.
Table 5
● Alternative III: Providing a perPlmnCallbackUri attribute, which may include a callback URI per remote PLMN (e.g., a PLMN in which an NF service producer is located) in the type of DefaultNotificationSubscription. In an embodiment, the callback URI per remote PLMN may be represented by a map which indicates an association between a key (e.g., a PLMN ID such as PlmnId, etc. ) and a value (e.g., a callback URI, etc. ) . As an example, the format of the map may be:
{
"460-01" : { "callbackUri" : https: //operator. mnc001. mcc315.3gpp. xxx/ {prefix1} /notificaitonUri} ,
"380-02" : { "callbackUri" : https: //operator. mnc001. mcc315.3gpp. xxx/ {prefix1} /notificaitonUri}
}
The NF service producer may retrieve a callback URI specified for its PLMN from the perPlmnCallbackUri attribute, and use the retrieved URI to send a notification request, instead of using the callbackUri attribute which does not support the inter-PLMN access.
Table 6 lists exemplary attributes notificationType, callbackUri and perPlmnCallbackUri in the type of DefaultNotificationSubscription.
Table 6
By adding one or more attributes such as intraPlmnCallbackRoot, interPlmnCallbackRoot, interPlmnCallbackUri and perPlmnCallbackUri as described with respect to Tables 4-6, the default notification subscription may work not only for the intra-PLMN scenario where the NF service producer and NF service consumer are located in the same PLMN, but also for the inter-PLMN scenario where the NF service producer and NF service consumer are located in different PLMNs.
Fig. 1C is a diagram illustrating an exemplary AAA server triggered slice-specific authorization revocation procedure according to an embodiment of the present disclosure. Compared to the procedure “AAA server triggered slice-specific authorization revocation” as described in the chapter 4.2.9.4 of 3GPP TS 23.502 V18.1.1, in the procedure as illustrated in Fig. 1C, an AMF may register both intra-PLMN routing information and inter-PLMN routing information in the default notification subscription of its NF profile or NF services. In accordance with exemplary embodiments, the inter-PLMN routing information may include the intraPlmnCallbackRoot and interPlmnCallbackRoot attributes as listed in Table 4, or the interPlmnCallbackUri attribute as listed in Table 5, or the perPlmnCallbackUri attribute as listed in Table 6, etc. It can be appreciated that such attribute (s) may also be applied to other NF service consumers than the AMF.
As shown in Fig. 1C, the AAA server triggered slice-specific authorization revocation procedure may include the following steps:
1. Besides the callbackUri attribute in the type of DefaultNotificationSubscription, an AMF for a UE in a VPLMN may include additional inter-PLMN routing information (e.g., the intraPlmnCallbackRoot, interPlmnCallbackRoot, interPlmnCallbackUri, perPlmnCallbackUri attributes, etc. ) into the DefaultNotificaitonSubscription type of NFProfile (or NFService for other use cases) as well with respect to a scenario where an NF service producer such as an NSSAAF and an NF service consumer such as the AMF are in different PLMNs, e.g., for the NSSAA_REAUTH_NOTIFICATION notification type in an NFRegister request, and send the NFRegister request to an NRF in the VPLMN in which the AMF is located.
2. The NRF may send to the AMF a response for the NFRegister request.
3. The UE may be registered into the 5GS, and the network slice-specific authentication and authorization may be performed. Then S-NSSAI subject to an NSSAA may be accepted by an AAA-S.
4. The AAA-Smay request the revocation of authorization for the network slice specified by the S-NSSAI in a AAA Protocol Revoke Auth Request message, for the UE identified by the GPSI in this message.
5. The NSSAAF in an HPLMN may send to a UDM an Nudm_UECM_Get message with the GPSI in the received AAA message to find the AMF the UE registered.
6. The UDM may return the AMF ID the UE registered.
7. The NSSAAF may provide an acknowledgement to the AAA Protocol Revoke Auth Request message.
8. The NSSAAF may send an Nnrf_NFDiscovery_Request message with the AMF ID retrieved in Step 6 to an NRF in the HPLMN.
9. The NRF in the HPLMN may forward the Nnrf_NFDiscovery_Request message to the NRF in the VPLMN.
10. The NRF in the VPLMN may return, to the NRF in the HPLMN, the NFProfile of the AMF that the UE registered. The NFProfile of the AMF may include callbackUri and inter-PLMN routing information in the DefaultNotificaitonSubscription.
11. The NRF in the HPLMN may forward the result (e.g., including the callbackUri and the inter-PLMN routing information in the DefaultNotificaitonSubscription, etc. ) to the NSSAAF.
12. The NSSAAF may locally determine a callback URI for inter-PLMN routing instead of the callbackUri attribute to send a notification towards the AMF. In accordance with exemplary embodiments, the NSSAAF may determine the callback URI for inter-PLMN routing in different ways according to the additional inter-PLMN routing information provided in the DefaultNotificaitonSubscription of the AMF. For example, there may be following options for determining the callback URI for inter-PLMN routing:
(i) For the InterPlmnCallbackRoot attribute, the NSSAAF may replace the intraPlmnCallbackRoot part of the callbackUri attribute with the value in the InterPlmnCallbackRoot attribute, and then use the newly constructed URI as the callback URI for inter-PLMN routing.
(ii) For the InterPlmnCallbackUri attribute, the NSSAAF may use the URI in this attribute directly as the callback URI for inter-PLMN routing.
(iii) For the perPlmnCallbackUri attribute, the NSSAAF may search a corresponding callback URI for its PLMN, and if found, then the NSSAAF may use the URI searched from the perPlmnCallbackUri attribute directly as the callback URI for inter-PLMN routing.
13. The NSSAAF may notify the AMF by the callback URI determined in the previous step to revoke the S-NSSAI authorization for the UE using an Nnssaaf_NSSAA_RevocationNotification message with the GPSI and S-NSSAI in the received AAA message.
14. Optionally, the AMF may initiate the procedure to synchronize the revocation of S-NSSAI to the UE.
In accordance with an exemplary embodiment, in addition to the revocation notification as described with respect to Fig. 1C, the inter-network routing information such as the inter-PLMN callback URI according to various exemplary embodiments may also be applicable to other suitable types of notifications for which the inter-PLMN access may be required. Table 7 lists some exemplary notifications which may be routed in an inter-PLMN scenario.
Table 7
It can be appreciated that network elements and signaling messages shown in Figs. 1A-1C are just as examples, and more or less alternative network elements and signaling messages may be involved in the exemplary procedures according to various embodiments of the present disclosure. It also can be appreciated that the names, representations and settings of the parameter/attributes/messages used herein are exemplary, and other names, representations and settings may also be used to indicate the same or similar information.
Fig. 2 is a flowchart illustrating a method 200 according to some embodiments of the present disclosure. The method 200 illustrated in Fig. 2 may be performed by a first network node (e.g., an NF service consumer such as an AMF, etc. ) or an apparatus communicatively coupled to the first network node. In accordance with an exemplary embodiment, the first network node may be configured to serve a terminal device (e.g., a UE, etc. ) capable of roaming across different networks. In accordance with another exemplary embodiment, the first network node may be configured to implement an AMF or act as any other suitable network entity which may be configured to perform access and mobility management for the terminal device.
According to the exemplary method 200 illustrated in Fig. 2, the first network node may generate a message for registering the first network node in a second network node (e.g., an NRF, etc. ) . The message may include first routing information (e.g., inter-network routing information represented by the intraPlmnCallbackRoot and interPlmnCallbackRoot attributes as listed in Table 4, the interPlmnCallbackUri attribute as listed in Table 5, the perPlmnCallbackUri attribute as listed in Table 6, etc. ) for routing an inter-network notification (e.g., the notifications as listed in Table 7, etc. ) towards the first network node. In accordance with an exemplary embodiment, the first network node may transmit, to the second network node in a first network, the message for registering the first routing information for routing an inter-network notification towards the first network node in a default notification subscription of the first network node’s profile in the second network node, as shown in block 202. In an embodiment, the first routing information may be included in a type of notification subscription (e.g., the type of DefaultNotificationSubscription as described with respect to Tables 4-6, etc. ) for an NF profile and/or an NF service of the first network node. In accordance with an exemplary embodiment, the first network node may receive a notification from a fourth network node in a second network based on the first routing information, as shown in block 204.
In accordance with an exemplary embodiment, the message may further include second routing information (e.g., routing information represented by the callbackUri attribute as listed in Tables 4-6, etc. ) . In an embodiment, the message may be further for registering the second routing information for routing a notification towards the first network node in the default notification subscription of the first network node’s profile in the second network node. The second routing information may be different from the first routing information. In an embodiment, the second routing information may be for routing an intra-network notification towards the first network node.
In accordance with an exemplary embodiment, the first network node may be configured to act as an NF service consumer supporting a roaming functionality. In accordance with another exemplary embodiment, the second network node may be configured to act as a repository for registering NF information of the first network node.
In accordance with an exemplary embodiment, the first network node may be in the first network (e.g., a VPLMN, etc. ) . In an embodiment, the first routing information may indicate a first URI for receiving the inter-network notification transmitted by an NF service producer (e.g., an NSSAAF, etc. ) in the second network (e.g., a HPLMN, etc. ) . In another embodiment, the second routing information may indicate a second URI for receiving the intra-network notification transmitted by an NF service producer in the first network.
In accordance with an exemplary embodiment, the first URI and the second URI may have a same path part, and the first routing information may include a root part of the first URI and a root part of the second URI (e.g., the intraPlmnCallbackRoot and interPlmnCallbackRoot attributes as listed in Table 4, etc. ) .
In accordance with an exemplary embodiment, the first routing information may include the first URI (e.g., the interPlmnCallbackUri attribute as listed in Table 5, etc. ) . For example, the first URI may include a root part and a path part.
In accordance with an exemplary embodiment, the first routing information may include a map based on a URI per network (e.g., the perPlmnCallbackUri attribute as listed in Table 6, etc. ) . For the second network different from the first network, the map may indicate a URI for receiving the inter-network notification transmitted by an NF service producer in the second network. In an embodiment, for one or more networks different from the first network, the map may indicate one or more URIs associated with the one or more networks according to HTTP schemes and/or authorities and/or prefixes of the one or more URIs. Depending on different network configurations and routing policies, a URI for receiving a notification from an NF service producer may be associated to one or more networks (e.g., PLMNs, etc. ) based on the map.
Fig. 3 is a flowchart illustrating a method 300 according to some embodiments of the present disclosure. The method 300 illustrated in Fig. 3 may be performed by a second network node (e.g., an NRF, etc. ) or an apparatus communicatively coupled to the second network node. In accordance with an exemplary embodiment, the second network node may be configured to store profiles of one or more NFs (e.g., AMFs, etc. ) . In accordance with another exemplary embodiment, the second network node may be configured to implement an NRF, or act as a repository or any other suitable network entity which may be able to implement an NF repository function for registering NF information of a network node (e.g., an AMF, etc. ) and/or assisting in NF register and discovery.
According to the exemplary method 300 illustrated in Fig. 3, the second network node may receive a message transmitted by a first network node (e.g., the first network node as described with respect to Fig. 2) for registering the first network node in the second network node. In an embodiment, the second network node may receive a message transmitted by the first network node for registering first routing information for routing an inter-network notification towards the first network node in a default notification subscription of the first network node’s profile in the second network node, as shown in block 302. In accordance with an exemplary embodiment, the second network node may register the first network node in the second network node according to the message. For example, the second network node may register the first routing information according to the message, as shown in block 304.
In accordance with an exemplary embodiment, the message may be further for registering second routing information for routing a notification towards the first network node in the default notification subscription of the first network node’s profile in the second network node. The second routing information may be different from the first routing information. In an embodiment, the second routing information may be for routing an intra-network notification towards the first network node.
In accordance with an exemplary embodiment, the message received by the second network node according to the method 300 may correspond to the message transmitted by the first network node according to the method 200. Thus, the first routing information included in the message as described with respect to Fig. 2 and Fig. 3 may have the same or similar contents and/or feature elements. Similarly, the second routing information included in the message as described with respect to Fig. 2 and Fig. 3 may have the same or similar contents and/or feature elements.
In accordance with an exemplary embodiment, when the second network node are in a first network, the second network node may receive a message for discovering the first network node transmitted by a third network node (e.g., an NRF, etc. ) in a second network. In accordance with another exemplary embodiment, the second network node may transmit a response including the first routing information towards the third network node.
In accordance with an exemplary embodiment, the first routing information may be included in a type of notification subscription for an NF profile and/or an NF service of the first network node.
Fig. 4 is a flowchart illustrating a method 400 according to some embodiments of the present disclosure. The method 400 illustrated in Fig. 4 may be performed by a third network node (e.g., an NRF, etc. ) or an apparatus communicatively coupled to the third network node. In accordance with an exemplary embodiment, the third network node may be configured to store profiles of one or more NFs (e.g., AMFs, etc. ) . In accordance with another exemplary embodiment, the third network node may be configured to implement an NRF, or act as a repository or any other suitable network entity which may be able to implement an NF repository function for registering NF information of a network node (e.g., an AMF, etc. ) and/or assisting in NF register and discovery.
According to the exemplary method 400 illustrated in Fig. 4, the third network node may receive a message transmitted by a fourth network node (e.g., an NF service producer such as an NSSAAF, etc. ) for discovering a first network node (e.g., the first network node as described with respect to Fig. 2) , as shown in block 402. In accordance with an exemplary embodiment, the third network node may transmit a response towards the fourth network node, as shown in block 404. The response may include a profile of the first network node including a default notification subscription, and the default notification subscription may include first routing information for routing an inter-network notification towards the first network node.
In accordance with an exemplary embodiment, the default notification subscription may further include second routing information for routing a notification towards the first network node. The second routing information may be different from the first routing information. In an embodiment, the second routing information may be for routing an intra-network notification towards the first network node.
In accordance with an exemplary embodiment, the first routing information according to the method 400 may correspond to the first routing information according to the method 200 and the method 300. Thus, the first routing information as described with respect to Fig. 2, Fig. 3 and Fig. 4 may have the same or similar contents and/or feature elements.
In accordance with another exemplary embodiment, the second routing information according to the method 400 may correspond to the second routing information according to the method 200 and the method 300. Thus, the second routing information as described with respect to Fig. 2, Fig. 3 and Fig. 4 may have the same or similar contents and/or feature elements.
In accordance with an exemplary embodiment, the first network node may be registered in a second network node (e.g., the second network node as described with respect to Fig. 3) located in a first network. When the third network node and the fourth network node are in a second network, the third network node may transmit a message for discovering the first network node towards the second network node. In accordance with another exemplary embodiment, the third network node may receive a response including the first routing information transmitted by the second network node.
In accordance with an exemplary embodiment, the first routing information may be included in a type of notification subscription for an NF profile and/or an NF service of the first network node.
It can be appreciated that the third network node as described with respect to Fig. 3 may also be configured to perform the method 200 as described with respect to Fig. 2, according to different application scenarios and service requirements. For example, the third network node may register routing information for a notification towards an NF service consumer. In an NF discovery procedure with respect to the NF service consumer, the third network node may provide the registered routing information to an NF service producer directly (e.g., when the NF service consumer and the NF service producer are in the same network) , or via another NRF (e.g., when the NF service consumer and the NF service producer are in different networks) .
Similarly, it can be appreciated that the second network node as described with respect to Fig. 2 may also be configured to perform the method 300 as described with respect to Fig. 3, according to different application scenarios and service requirements. For example, when an NF service consumer and an NF service producer are in the same network and the second network node has routing information for a notification towards the NF service consumer, the second network node may provide the routing information to the NF service producer directly. When the NF service consumer and the NF service producer are in different networks and the second network node has no routing information for a notification towards the NF service consumer, the second network node may request the routing information from another NRF which has the routing information for the NF service consumer, and then forward the routing information obtained from the another NRF to the NF service producer.
Fig. 5 is a flowchart illustrating a method 500 according to some embodiments of the present disclosure. The method 500 illustrated in Fig. 5 may be performed by a fourth network node (e.g., an NF service producer such as an NSSAAF, etc. ) or an apparatus communicatively coupled to the fourth network node. In accordance with an exemplary embodiment, the fourth network node may be configured to act as an NF service producer to serve one or more NFs. In accordance with another exemplary embodiment, the fourth network node may be configured to implement an NSSAAF or act as any other suitable network entity which may be configured to perform a network slice-specific authentication and authorization function for an NF service consumer.
According to the exemplary method 500 illustrated in Fig. 5, the fourth network node may transmit a message for discovering a first network node (e.g., the first network node as described with respect to Fig. 2) towards a third network node (e.g., the third network node as described with respect to Fig. 4) , as shown in block 502. In accordance with an exemplary embodiment, the fourth network node may receive a response transmitted by the third network node, as shown in block 504. The response may include a profile of the first network node including a default notification subscription, and the default notification subscription may include first routing information for routing an inter-network notification towards the first network node.
In accordance with an exemplary embodiment, the default notification subscription may further include second routing information for routing a notification towards the first network node. The second routing information may be different from the first routing information. In an embodiment, the second routing information may be for routing an intra-network notification towards the first network node.
In accordance with an exemplary embodiment, the response received by the fourth network node according to the method 500 may correspond to the response transmitted by the third network node according to the method 400. Thus, the first routing information included in the response as described with respect to Fig. 4 and Fig. 5 may have the same or similar contents and/or feature elements. Similarly, the second routing information included in the response as described with respect to Fig. 4 and Fig. 5 may have the same or similar contents and/or feature elements.
In accordance with an exemplary embodiment, the first routing information may be included in a type of notification subscription for an NF profile and/or an NF service of the first network node.
In accordance with an exemplary embodiment, when the first network node is in a first network and the fourth network node is in a second network, the fourth network node may determine a URI based at least in part on the first routing information (e.g., according to an option as described with respect to step 12 of Fig. 1C, etc. ) . In an embodiment, the fourth network node may transmit a notification towards the first network node according to the determined URI.
In accordance with an exemplary embodiment, the fourth network node may determine the URI based at least in part on the first routing information by determining a root part of the URI according to the first routing information and a path part of the URI according to the first routing information and the second routing information (e.g., according to option (i) as described with respect to step 12 of Fig. 1C, etc. ) .
In accordance with an exemplary embodiment, the fourth network node may determine the URI based at least in part on the first routing information by reading the URI indicated by the first routing information (e.g., according to option (ii) as described with respect to step 12 of Fig. 1C, etc. ) .
In accordance with an exemplary embodiment, the fourth network node may determine the URI based at least in part on the first routing information by retrieving the URI in the first routing information according to an identifier (e.g., a PLMN ID, etc. ) of the second network (e.g., according to option (iii) as described with respect to step 12 of Fig. 1C, etc. ) .
The various blocks shown in Figs. 2-5 may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function (s) . The schematic flow chart diagrams described above are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of specific embodiments of the presented methods. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated methods. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown.
It can be appreciated that the network node according to various embodiments can be implemented either as a network element and/or a network entity on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g., on a cloud infrastructure.
Fig. 6 is a block diagram illustrating an apparatus 600 according to various embodiments of the present disclosure. As shown in Fig. 6, the apparatus 600 may comprise one or more processors such as processor 601 and one or more memories such as memory 602 storing computer program codes 603. The memory 602 may be non-transitory machine/processor/computer readable storage medium. In accordance with some exemplary embodiments, the apparatus 600 may be implemented as an integrated circuit chip or module that can be plugged or installed into a first network node as described with respect to Fig. 2, or a second network node as described with respect to Fig. 3, or a third network node as described with respect to Fig. 4, or a fourth network node as described with respect to Fig. 5. In such cases, the apparatus 600 may be implemented as a first network node as described with respect to Fig. 2, or a second network node as described with respect to Fig. 3, or a third network node as described with respect to Fig. 4, or a fourth network node as described with respect to Fig. 5.
In some implementations, the one or more memories 602 and the computer program codes 603 may be configured to, with the one or more processors 601, cause the apparatus 600 at least to perform any operation of the method as described in connection with Fig. 2. In other implementations, the one or more memories 602 and the computer program codes 603 may be configured to, with the one or more processors 601, cause the apparatus 600 at least to perform any operation of the method as described in connection with Fig. 3. In other implementations, the one or more memories 602 and the computer program codes 603 may be configured to, with the one or more processors 601, cause the apparatus 600 at least to perform any operation of the method as described in connection with Fig. 4. In other implementations, the one or more memories 602 and the computer program codes 603 may be configured to, with the one or more processors 601, cause the apparatus 600 at least to perform any operation of the method as described in connection with Fig. 5. Alternatively or additionally, the one or more memories 602 and the computer program codes 603 may be configured to, with the one or more processors 601, cause the apparatus 600 at least to perform more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.
Fig. 7A is a block diagram illustrating an apparatus 710 according to some embodiments of the present disclosure. As shown in Fig. 7A, the apparatus 710 may comprise a transmitting unit 711 and a receiving unit 712. In an exemplary embodiment, the apparatus 710 may be implemented in a first network node (e.g., an NF service consumer such as an AMF, etc. ) . The transmitting unit 711 may be operable to carry out the operation in block 202, and the receiving unit 712 may be operable to carry out the operation in block 204. Optionally, the transmitting unit 711 and/or the receiving unit 712 may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.
Fig. 7B is a block diagram illustrating an apparatus 720 according to some embodiments of the present disclosure. As shown in Fig. 7B, the apparatus 720 may comprise a receiving unit 721 and a registering unit 722. In an exemplary embodiment, the apparatus 720 may be implemented in a second network node (e.g., an NRF, etc. ) . The receiving unit 721 may be operable to carry out the operation in block 302, and the registering unit 722 may be operable to carry out the operation in block 304. Optionally, the receiving unit 721 and/or the registering unit 722 may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.
Fig. 7C is a block diagram illustrating an apparatus 730 according to some embodiments of the present disclosure. As shown in Fig. 7C, the apparatus 730 may comprise a receiving unit 731 and a transmitting unit 732. In an exemplary embodiment, the apparatus 730 may be implemented in a third network node (e.g., an NRF, etc. ) . The receiving unit 731 may be operable to carry out the operation in block 402, and the transmitting unit 732 may be operable to carry out the operation in block 404. Optionally, the receiving unit 731 and/or the transmitting unit 732 may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.
Fig. 7D is a block diagram illustrating an apparatus 740 according to some embodiments of the present disclosure. As shown in Fig. 7D, the apparatus 740 may comprise a transmitting unit 741 and a receiving unit 742. In an exemplary embodiment, the apparatus 740 may be implemented in a fourth network node (e.g., an NF service producer such as an NSSAAF, etc. ) . The transmitting unit 741 may be operable to carry out the operation in block 502, and the receiving unit 742 may be operable to carry out the operation in block 504. Optionally, the transmitting unit 741 and/or the receiving unit 742 may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.
In general, the various exemplary embodiments may be implemented in hardware or special purpose chips, circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the disclosure is not limited thereto. While various aspects of the exemplary embodiments of this disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.
As such, it should be appreciated that at least some aspects of the exemplary embodiments of the disclosure may be practiced in various components such as integrated circuit chips and modules. It should thus be appreciated that the exemplary embodiments of this disclosure may be realized in an apparatus that is embodied as an integrated circuit, where the integrated circuit may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor, a digital signal processor, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this disclosure.
It should be appreciated that at least some aspects of the exemplary embodiments of the disclosure may be embodied in computer-executable instructions, such as in one or more program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types when executed by a processor in a computer or other device. The computer executable instructions may be stored on a computer readable medium such as a hard disk, optical disk, removable storage media, solid state memory, random access memory (RAM) , etc. As will be appreciated by one of skill in the art, the function of the program modules may be combined or distributed as desired in various embodiments. In addition, the function may be embodied in whole or partly in firmware or hardware equivalents such as integrated circuits, field programmable gate arrays (FPGA) , and the like.
The present disclosure includes any novel feature or combination of features disclosed herein either explicitly or any generalization thereof. Various modifications and adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this disclosure.

Claims

A method (200) performed by a first network node, comprising:

transmitting (202) , to a second network node in a first network, a message for registering first routing information for routing an inter-network notification towards the first network node in a default notification subscription of the first network node’s profile in the second network node; and

receiving (204) a notification from a fourth network node in a second network based on the first routing information.
The method according to claim 1, wherein the message is further for registering second routing information for routing a notification towards the first network node in the default notification subscription of the first network node’s profile in the second network node, and the second routing information is different from the first routing information.
The method according to claim 2, wherein the second routing information is for routing an intra-network notification towards the first network node.
The method according to claim 3, wherein the first network node is configured to act as a network function, NF, service consumer supporting a roaming functionality; and/or the second network node is configured to act as a repository for registering NF information of the first network node.
The method according to claim 4, wherein the first network node is in the first network, and the first routing information indicates a first uniform resource identifier, URI, for receiving the inter-network notification transmitted by an NF service producer in the second network, and the second routing information indicates a second URI for receiving the intra-network notification transmitted by an NF service producer in the first network.
The method according to claim 5, wherein the first URI and the second URI have a same path part, and the first routing information includes a root part of the first URI and a root part of the second URI.
The method according to claim 5, wherein the first routing information includes the first URI.
The method according to claim 5, wherein the first routing information includes a map based on a URI per network, and for the second network different from the first network, the map indicates a URI for receiving the inter-network notification transmitted by an NF service producer in the second network.
The method according to claim 8, wherein for one or more networks different from the first network, the map indicates one or more URIs associated with the one or more networks according to hypertext transfer protocol, HTTP, schemes and/or authorities and/or prefixes of the one or more URIs.
The method according to any of claims 1-9, wherein the first routing information is included in a type of notification subscription for an NF profile and/or an NF service of the first network node.
The method according to any of claims 1-10, wherein the first network node is configured to implement an access and mobility management function, AMF; and/or the second network node is configured to implement a network-function repository function, NRF.
A first network node (600) , comprising:

one or more processors (601) ; and

one or more memories (602) comprising computer program codes (603) ,

the one or more memories (602) and the computer program codes (603) configured to, with the one or more processors (601) , cause the first network node (600) at least to:

transmit, to a second network node in a first network, a message for registering first routing information for routing an inter-network notification towards the first network node in a default notification subscription of the first network node’s profile in the second network node; and

receive a notification from a fourth network node in a second network based on the first routing information.
The first network node according to claim 12, wherein the one or more memories and the computer program codes are configured to, with the one or more processors, cause the first network node to perform the method according to any one of claims 2-11.
A method (300) performed by a second network node, comprising:

receiving (302) a message transmitted by a first network node for registering first routing information for routing an inter-network notification towards the first network node in a default notification subscription of the first network node’s profile in the second network node; and

registering (304) the first routing information according to the message.
The method according to claim 14, wherein the message is further for registering second routing information for routing a notification towards the first network node in the default notification subscription of the first network node’s profile in the second network node, and the second routing information is different from the first routing information.
The method according to claim 15, wherein the second routing information is for routing an intra-network notification towards the first network node.
The method according to claim 16, wherein the first network node is configured to act as a network function, NF, service consumer supporting a roaming functionality; and/or the second network node is configured to act as a repository for registering NF information of the first network node.
The method according to claim 17, wherein the first network node is in a first network, and the first routing information indicates a first uniform resource identifier, URI, for receiving the inter-network notification transmitted by an NF service producer in a second network, and the second routing information indicates a second URI for receiving the intra-network notification transmitted by an NF service producer in the first network.
The method according to claim 18, wherein the first URI and the second URI have a same path part, and the first routing information includes a root part of the first URI and a root part of the second URI.
The method according to claim 18, wherein the first routing information includes the first URI.
The method according to claim 18, wherein the first routing information includes a map based on a URI per network, and for a second network different from the first network, the map indicates a URI for receiving the inter-network notification transmitted by an NF service producer in the second network.
The method according to claim 21, wherein for one or more networks different from the first network, the map indicates one or more URIs associated with the one or more networks according to hypertext transfer protocol, HTTP, schemes and/or authorities and/or prefixes of the one or more URIs.
The method according to any of claims 14-22, wherein the first routing information is included in a type of notification subscription for an NF profile and/or an NF service of the first network node.
The method according to any of claims 14-23, wherein when the second network node is in a first network, the method further comprises:

receiving a message for discovering the first network node transmitted by a third network node in a second network; and

transmitting a response including the first routing information towards the third network node.
The method according to claim 24, wherein the first network node is configured to implement an access and mobility management function, AMF; and/or the second network node is configured to implement a network-function repository function, NRF; and/or the third network node is configured to implement an NRF.
A second network node (600) , comprising:

one or more processors (601) ; and

one or more memories (602) comprising computer program codes (603) ,

the one or more memories (602) and the computer program codes (603) configured to, with the one or more processors (601) , cause the second network node (600) at least to:

receive a message transmitted by a first network node for registering first routing information for routing an inter-network notification towards the first network node in a default notification subscription of the first network node’s profile in the second network node; and

register the first routing information according to the message.
The second network node according to claim 26, wherein the one or more memories and the computer program codes are configured to, with the one or more processors, cause the second network node to perform the method according to any one of claims 15-25.
A method (400) performed by a third network node, comprising:

receiving (402) a message transmitted by a fourth network node for discovering a first network node; and

transmitting (404) a response towards the fourth network node, wherein the response includes a profile of the first network node including a default notification subscription, and the default notification subscription includes first routing information for routing an inter-network notification towards the first network node.
The method according to claim 28, wherein the default notification subscription further includes second routing information for routing a notification towards the first network node, and the second routing information is different from the first routing information.
The method according to claim 29, wherein the second routing information is for routing an intra-network notification towards the first network node.
The method according to claim 30, wherein the first network node is configured to act as a network function, NF, service consumer supporting a roaming functionality; and/or the third network node is configured to act as a repository for registering NF information of the first network node; and/or the fourth network node is configured to act as an NF service producer.
The method according to claim 31, wherein the first network node is in a first network, and the first routing information indicates a first uniform resource identifier, URI, for receiving the inter-network notification transmitted by an NF service producer in a second network, and the second routing information indicates a second URI for receiving the intra-network notification transmitted by an NF service producer in the first network.
The method according to claim 32, wherein the first URI and the second URI have a same path part, and the first routing information includes a root part of the first URI and a root part of the second URI.
The method according to claim 32, wherein the first routing information includes the first URI.
The method according to claim 32, wherein the first routing information includes a map based on a URI per network, and for a second network different from the first network, the map indicates a URI for receiving the inter-network notification transmitted by an NF service producer in the second network.
The method according to claim 35, wherein for one or more networks different from the first network, the map indicates one or more URIs associated with the one or more networks according to hypertext transfer protocol, HTTP, schemes and/or authorities and/or prefixes of the one or more URIs.
The method according to any of claims 28-36, wherein the first routing information is included in a type of notification subscription for an NF profile and/or an NF service of the first network node.
The method according to any of claims 28-37, wherein when the third network node and the fourth network node are in a second network, the method further comprises:

transmitting a message for discovering the first network node towards a second network node in a first network, wherein the first network node is registered in the second network node; and

receiving a response including the first routing information transmitted by the second network node.
The method according to claim 38, wherein the first network node is configured to implement an access and mobility management function, AMF; and/or the second network node is configured to implement a network-function repository function, NRF; and/or the third network node is configured to implement an NRF; and/or the fourth network node is configured to implement a network slice-specific authentication and authorization function, NSSAAF.
A third network node (600) , comprising:

one or more processors (601) ; and

one or more memories (602) comprising computer program codes (603) ,

the one or more memories (602) and the computer program codes (603) configured to, with the one or more processors (601) , cause the third network node (600) at least to:

receive a message transmitted by a fourth network node for discovering a first network node; and

transmit a response towards the fourth network node, wherein the response includes a profile of the first network node including a default notification subscription, and the default notification subscription includes first routing information for routing an inter-network notification towards the first network node.
The third network node according to claim 40, wherein the one or more memories and the computer program codes are configured to, with the one or more processors, cause the third network node to perform the method according to any one of claims 29-39.
A method (500) performed by a fourth network node, comprising:

transmitting (502) a message for discovering a first network node towards a third network node; and

receiving (504) a response transmitted by the third network node, wherein the response includes a profile of the first network node including a default notification subscription, and the default notification subscription includes first routing information for routing an inter-network notification towards the first network node.
The method according to claim 42, wherein the default notification subscription further includes second routing information for routing a notification towards the first network node, and the second routing information is different from the first routing information.
The method according to claim 43, wherein the second routing information is for routing an intra-network notification towards the first network node.
The method according to claim 44, wherein the first network node is configured to act as a network function, NF, service consumer supporting a roaming functionality; and/or the third network node is configured to act as a repository for registering NF information of the first network node; and/or the fourth network node is configured to act as an NF service producer.
The method according to claim 45, wherein the first network node is in a first network, and the first routing information indicates a first uniform resource identifier, URI, for receiving the inter-network notification transmitted by an NF service producer in a second network, and the second routing information indicates a second URI for receiving the intra-network notification transmitted by an NF service producer in the first network.
The method according to claim 46, wherein the first URI and the second URI have a same path part, and the first routing information includes a root part of the first URI and a root part of the second URI.
The method according to claim 46, wherein the first routing information includes the first URI.
The method according to claim 46, wherein the first routing information includes a map based on a URI per network, and for a second network different from the first network, the map indicates a URI for receiving the inter-network notification transmitted by an NF service producer in the second network.
The method according to claim 49, wherein for one or more networks different from the first network, the map indicates one or more URIs associated with the one or more networks according to hypertext transfer protocol, HTTP, schemes and/or authorities and/or prefixes of the one or more URIs.
The method according to any of claims 46-50, wherein when the first network node is in a first network and the fourth network node is in a second network, the method further comprises:

determining a URI based at least in part on the first routing information; and

transmitting a notification towards the first network node according to the determined URI.
The method according to claim 51, wherein the fourth network node determines the URI based at least in part on the first routing information by:

determining a root part of the URI according to the first routing information and a path part of the URI according to the first routing information and the second routing information; or

reading the URI indicated by the first routing information; or

retrieving the URI in the first routing information according to an identifier of the second network.
The method according to any of claims 42-52, wherein the first routing information is included in a type of notification subscription for an NF profile and/or an NF service of the first network node.
The method according to any of claim 42-53, wherein the first network node is configured to implement an access and mobility management function, AMF; and/or the third network node is configured to implement a network-function repository function, NRF; and/or the fourth network node is configured to implement a network slice-specific authentication and authorization function, NSSAAF.
A fourth network node (600) , comprising:

one or more processors (601) ; and

one or more memories (602) comprising computer program codes (603) ,

the one or more memories (602) and the computer program codes (603) configured to, with the one or more processors (601) , cause the fourth network node (600) at least to:

transmit a message for discovering a first network node towards a third network node; and

receive a response transmitted by the third network node, wherein the response includes a profile of the first network node including a default notification subscription, and the default notification subscription includes first routing information for routing an inter-network notification towards the first network node.
The fourth network node according to claim 55, wherein the one or more memories and the computer program codes are configured to, with the one or more processors, cause the fourth network node to perform the method according to any one of claims 43-54.
A computer-readable medium having computer program codes (603) embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to any one of claims 1-11 or any one of claims 14-25 or any one of claims 28-39 or any one of claims 42-54.