DESCRIPTION

BACKGROUND

Field

Examples of embodiments relate to apparatuses, methods, systems, computer programs, computer program products and (non-transitory) computer-readable media usable for selecting a serving call session control function for use in a communication network based on e.g. 3GPP standards. Specifically, examples of embodiments relate to apparatuses, methods, systems, computer programs, computer program products and (non-transitory) computer-readable media usable for selecting a serving call session control function by a process avoiding the necessity to use local configuration.

Background Art

The following description of background art may include insights, discoveries, understandings or disclosures, or associations, together with disclosures not known to the relevant prior art, to at least some examples of embodiments of the present disclosure but provided by the disclosure. Some of such contributions of the disclosure may be specifically pointed out below, whereas other of such contributions of the disclosure will be apparent from the related context.

The following meanings for the abbreviations used in this specification apply:

3GPP 3 ^rd Generation Partnership Project

4G fourth generation

5G fifth generation

5GS 5G system

AP access point

BS base station

CM configuration management

CPU central processing unit DNS domain name server eNB E-UTRAN Node B

ETSI European Telecommunications Standards Institute

FQDN fully qualified domain name gNB next generation node B

HSS home subscriber server l-CSCF interrogating call session control function

ID identification

IMS IP multimedia subsystem

IP Internet protocol

JSON Java script object notation

LTE Long Term Evolution

LTE- A LTE Advanced

NF network function

NG new generation

NR new radio

NRF network repository function

NW network, network side

P-CSCF proxy call session control function

RAN radio access network

RAT radio access technology

S-CSCF serving call session control function

SBI service based interface

SIP session initiation protocol

TCP transmission control protocol

TLS transport layer security

UDP user datagram protocol

UE user equipment

URI uniform resource identifier

SUMMARY

According to an example of an embodiment, there is provided, for example, an apparatus for use by a communication network control element or function configured to act as a network repository element or function in a communication network, the apparatus comprising at least one processing circuitry, and at least one memory for storing instructions to be executed by the processing circuitry, wherein the at least one memory and the instructions are configured to, with the at least one processing circuitry, cause the apparatus at least: to receive, from a network element or function acting as a call session control function in a multimedia subsystem of a communication network, profile information of the call session control function, the profile information comprises data to be used in a selection procedure to be conducted for a registration in the multimedia subsystem, to store the profile information being received, and to process the stored profile information for transmission thereof in response to a discovery process signaling from a network element or function acting as an interrogating call session control function in the multimedia subsystem.

Furthermore, according to an example of an embodiment, there is provided, for example, a method for use in a communication network control element or function configured to act as a network repository element or function in a communication network, the method comprising receiving, from a network element or function acting as a call session control function in a multimedia subsystem of a communication network, profile information of the call session control function, the profile information comprises data to be used in a selection procedure to be conducted for a registration in the multimedia subsystem, storing the profile information being received, and processing the stored profile information for transmission thereof in response to a discovery process signaling from a network element or function acting as an interrogating call session control function in the multimedia subsystem.

According to further refinements, these examples may include one or more of the following features:

- the profile information may comprise an identification of the call session control function, an indication of communication capability supported by the call session control function, an indication of a priority for the call session control function for a session initiation protocol interface of the multimedia subsystem, an indication of a load for the call session control function for the session initiation protocol interface of the multimedia subsystem, and an indication of a capacity for the call session control function for the session initiation protocol interface of the multimedia subsystem;

- the profile information may further comprise at least one of an indication of communication scheme indicating one of a user datagram protocol, a transmission control protocol and transport layer security, an internet protocol address of the call session control function, and an indication of a port used by the call session control function;

- the profile information may be transmitted to a network element or function acting as an interrogating call session control function in the multimedia subsystem of the communication network;

- registration information of at least one of a home subscriber server of the communication network, an interrogating call session control function in the multimedia subsystem of the communication network, and a serving call session control function in the multimedia subsystem of the communication network may be received;

According to an example of an embodiment, there is provided, for example, an apparatus for use by a communication network control element or function configured to act as a call session control element or function in a multimedia subsystem of a communication network, the apparatus comprising at least one processing circuitry, and at least one memory for storing instructions to be executed by the processing circuitry, wherein the at least one memory and the instructions are configured to, with the at least one processing circuitry, cause the apparatus at least: to conduct a discovery process for searching for network elements or functions capable of acting as a call session control function in a multimedia subsystem of a communication network, the discovery process being conducted with a network repository element or function of a communication network, and to obtain, in the discovery process, a list comprising profile information of at least one network element or function capable of acting as a call session control function.

Furthermore, according to an example of an embodiment, there is provided, for example, a method for use in a communication network control element or function configured to act as a call session control element or function in a multimedia subsystem of a communication network, the method comprising conducting a discovery process for searching for network elements or functions capable of acting as a call session control function in a multimedia subsystem of a communication network, the discovery process being conducted with a network repository element or function of a communication network, and obtaining, in the discovery process, a list comprising profile information of at least one network element or function capable of acting as a call session control function. According to further refinements, these examples may include one or more of the following features:

- the profile information may comprise an identification of the call session control function, an indication of communication capability supported by the call session control function, an indication of a priority for the call session control function for a session initiation protocol interface of the multimedia subsystem, an indication of a load for the call session control function for the session initiation protocol interface of the multimedia subsystem, and an indication of a capacity for the call session control function for the session initiation protocol interface of the multimedia subsystem;

- the profile information may further comprise at least one of an indication of communication scheme indicating one of a user datagram protocol, a transmission control protocol and transport layer security, an internet protocol address of the call session control function, and an indication of a port used by the call session control function;

- a registration process for a communication element or function registering in the multimedia subsystem may be conducted, and a serving call session control function to be assigned to the communication element or function may be selected, wherein selection of the serving call session control function may be based on the list obtained from the repository element or function and comprising the profile information;

- the selection of the serving call session control function may be based on at least one of a priority indicated in the profile information for a call session control function for a session initiation protocol interface of the multimedia subsystem, a load indicated in the profile information for the call session control function for the session initiation protocol interface of the multimedia subsystem, and a capacity indicated in the profile information for the call session control function for the session initiation protocol interface of the multimedia subsystem;

- topological information for the serving call session control function may be obtained from the profile information;

- in the selection of the serving call session control function, information obtained from a home subscriber server of the communication network may be used.

In addition, according to embodiments, there is provided, for example, a computer program product for a computer, including software code portions for performing the steps of the above defined methods, when said product is run on the computer. The computer program product may include a computer-readable medium on which said software code portions are stored. Furthermore, the computer program product may be directly loadable into the internal memory of the computer and/or transmittable via a network by means of at least one of upload, download and push procedures.

BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the present disclosure are described below, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 shows a diagram illustrating an example of a communication network in which examples of embodiments are implementable;

Fig. 2 shows a diagram illustrating an example of IMS part of a communication network in which examples of embodiments are implementable;

Fig. 3 shows a signaling diagram explaining an example of a procedure for selecting a S-CSCF according to examples of embodiments;

Fig. 4 shows a signaling diagram explaining an example of a procedure for selecting a S-CSCF according to examples of embodiments;

Fig. 5 shows a flow chart of a processing conducted in a network repository function according to some examples of embodiments;

Fig. 6 shows a flow chart of a processing conducted in an l-CSCF element or function according to some examples of embodiments;

Fig. 7 shows a diagram of a network element or function acting as a network repository function according to some examples of embodiments; and

Fig. 8 shows a diagram of a network element or function acting as an l-CSCF according to some examples of embodiments.

DESCRIPTION OF EMBODIMENTS In the last years, an increasing extension of communication networks, e.g. of wire based communication networks, such as the Integrated Services Digital Network (ISDN), Digital Subscriber Line (DSL), or wireless communication networks, such as the cdma2000 (code division multiple access) system, cellular 3 ^rd generation (3G) like the Universal Mobile Telecommunications System (UMTS), fourth generation (4G) communication networks or enhanced communication networks based e.g. on Long Term Evolution (LTE) or Long Term Evolution-Advanced (LTE-A), fifth generation (5G) communication networks, cellular 2 ^nd generation (2G) communication networks like the Global System for Mobile communications (GSM), the General Packet Radio System (GPRS), the Enhanced Data Rates for Global Evolution (EDGE), or other wireless communication system, such as the Wireless Local Area Network (WLAN), Bluetooth or Worldwide Interoperability for Microwave Access (WiMAX), took place all over the world. Various organizations, such as the European Telecommunications Standards Institute (ETSI), the 3 ^rd Generation Partnership Project (3GPP), Telecoms & Internet converged Services & Protocols for Advanced Networks (TISPAN), the International Telecommunication Union (ITU), 3 ^rd Generation Partnership Project 2 (3GPP2), Internet Engineering Task Force (IETF), the IEEE (Institute of Electrical and Electronics Engineers), the WMAX Forum and the like are working on standards or specifications for telecommunication network and access environments.

In the following, different exemplifying embodiments will be described using, as an example of a communication network to which examples of embodiments may be applied, a communication network architecture based on 3GPP standards for a communication network, such as a 5G/NR, without restricting the embodiments to such an architecture, however. It is obvious for a person skilled in the art that the embodiments may also be applied to other kinds of communication networks, e.g. W-Fi, worldwide interoperability for microwave access (WMAX), Bluetooth®, personal communications services (PCS), ZigBee®, wideband code division multiple access (WCDMA), systems using ultra-wideband (UWB) technology, mobile ad-hoc networks (MANETs), wired access, etc.. Furthermore, without loss of generality, the description of some examples of embodiments is related to a mobile communication network, but principles of the disclosure can be extended and applied to any other type of communication network, such as a wired communication network. The following examples and embodiments are to be understood only as illustrative examples. Although the specification may refer to “an”, “one”, or “some” example(s) or embodiment(s) in several locations, this does not necessarily mean that each such reference is related to the same example(s) or embodiment(s), or that the feature only applies to a single example or embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, terms like “comprising” and “including” should be understood as not limiting the described embodiments to consist of only those features that have been mentioned; such examples and embodiments may also contain features, structures, units, modules etc. that have not been specifically mentioned.

A basic system architecture of a (tele)communication network including a mobile communication system where some examples of embodiments are applicable may include an architecture of one or more communication networks including wireless access network subsystem(s) and core network(s). Such an architecture may include one or more communication network control elements or functions, access network elements, radio access network elements, access service network gateways or base transceiver stations, such as a base station (BS), an access point (AP), a NodeB (NB), an eNB or a gNB, a distributed or a centralized unit, which controls a respective coverage area or cell(s) and with which one or more communication stations such as communication elements, user devices or terminal devices, like a UE, or another device having a similar function, such as a modem chipset, a chip, a module etc., which can also be part of a station, an element, a function or an application capable of conducting a communication, such as a UE, an element or function usable in a machine-to-machine communication architecture, or attached as a separate element to such an element, function or application capable of conducting a communication, or the like, are capable to communicate via one or more channels via one or more communication beams for transmitting several types of data in a plurality of access domains. Furthermore, core network elements or network functions, such as gateway network elements/functions, mobility management entities, a mobile switching center, servers, databases and the like may be included.

The general functions and interconnections of the described elements and functions, which also depend on the actual network type, are known to those skilled in the art and described in corresponding specifications, so that a detailed description thereof is omitted herein. However, it is to be noted that several additional network elements and signaling links may be employed for a communication to or from an element, function or application, like a communication endpoint, a communication network control element, such as a server, a gateway, a radio network controller, and other elements of the same or other communication networks besides those described in detail herein below.

A communication network architecture as being considered in examples of embodiments may also be able to communicate with other networks, such as a public switched telephone network or the Internet, as well as with individual devices or groups of devices being not considered as a part of a network, such as monitoring devices like cameras, sensors, arrays of sensors, and the like. The communication network may also be able to support the usage of cloud services for virtual network elements or functions thereof, wherein it is to be noted that the virtual network part of the telecommunication network can also be provided by non-cloud resources, e.g. an internal network or the like. It should be appreciated that network elements of an access system, of a core network etc., and/or respective functionalities may be implemented by using any node, host, server, access node or entity etc. being suitable for such a usage. Generally, a network function can be implemented either as a network element 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., a cloud infrastructure.

Furthermore, a network element, such as communication elements, like a UE, a terminal device, control elements or functions, such as access network elements, like a base station (BS), an gNB, a radio network controller, a core network control element or function, such as a gateway element, or other network elements or functions, such as management elements or functions, as described herein, and any other elements, functions or applications may be implemented by software, e.g. by a computer program product for a computer, and/or by hardware. For executing their respective processing, correspondingly used devices, nodes, functions or network elements may include several means, modules, units, components, etc. (not shown) which are required for control, processing and/or communication/signaling functionality. Such means, modules, units and components may include, for example, one or more processors or processor units including one or more processing portions for executing instructions and/or programs and/or for processing data, storage or memory units or means for storing instructions, programs and/or data, for serving as a work area of the processor or processing portion and the like (e.g. ROM, RAM, EEPROM, and the like), input or interface means for inputting data and instructions by software (e.g. floppy disc, CD- ROM, EEPROM, and the like), a user interface for providing monitor and manipulation possibilities to a user (e.g. a screen, a keyboard and the like), other interface or means for establishing links and/or connections under the control of the processor unit or portion (e.g. wired and wireless interface means, radio interface means including e.g. an antenna unit or the like, means for forming a radio communication part etc.) and the like, wherein respective means forming an interface, such as a radio communication part, can be also located on a remote site (e.g. a radio head or a radio station etc.). It is to be noted that in the present specification processing portions should not be only considered to represent physical portions of one or more processors, but may also be considered as a logical division of the referred processing tasks performed by one or more processors.

It should be appreciated that according to some examples, a so-called “liquid” or flexible network concept may be employed where the operations and functionalities of a network element, a network function, or of another entity of the network, may be performed in different entities or functions, such as in a node, host or server, in a flexible manner. In other words, a “division of labor” between involved network elements, functions or entities may vary case by case.

First, for illustrative purposes, a network architecture example based on 5GS principles is described in which examples of embodiments can be implemented.

Specifically, Fig. 1 shows a diagram illustrating an example of a system architecture of a wireless communication network based on 5GS in which examples of embodiments are implementable. It is to be noted that in the illustration of Fig. 1 a so-called service based interface definition is used. Furthermore, it is to be noted that the illustration in Fig. 1 mainly shows parts of a complete network architecture which are useful for understanding principles of embodiments of the disclosure.

Service-Based Architecture (SBA) provides a modular framework from which common applications can be deployed using components of varying sources and suppliers. Control plane functionality and common data repositories of a 5G network are delivered by way of a set of interconnected Network Functions (NFs), each with authorization to access each other’s services.

As shown in Fig. 1, a UE 10 as a communication element or function can be connected to the 5G network via an access network structure which is represented by RAN/AN 20 which is, for example, a base station (BS or NB) using a NR RAT and/or an evolved LTE base station, ora general base station including e.g. non-3GPP access, e.g., Wi-Fi, or a gNB.

A core network architecture shown in Fig. 1 applied for a 5GS network comprises various NFs. As shown in Fig. 1 , the CN NFs comprises, amongst others (not shown), an AMF 50, a session management function (SMF) 40, a policy control function (PCF) 60, a network exposure function (NEF) 70, a network repository function (NRF) 90, and one or more user plane function(s) (UPF) 30.

The AMF 50 provides UE-based authentication, authorization, mobility management, etc. A UE (e.g. UE 10) even when using multiple access technologies is basically connected to a single AMF because the AMF 50 is independent of the access technologies.

The SMF 40 sets up and manages sessions according to network policy. The SMF 40 is responsible, for example, for session management and allocates IP addresses to UEs. Furthermore, it selects and controls the UPF 30 for data transfer.

It is to be noted that it is also possible that in case the UE 10 has e.g. multiple sessions (communication connections), different SMFs may be allocated to each session to manage them individually and possibly provide different functionalities per session.

The UPF 30 can be deployed in various configurations and locations, according to the service type. Functions of the UPF 30 are e.g. QoS handling for user plane, packet routing and forwarding, packet inspection and policy rule enforcement, traffic accounting and reporting. The UPF 30 connects to a data network (DN) 100 on which one or more application servers providing a platform for application functions (AF) 80 are provided. The PCF 60 provides a policy framework incorporating network slicing, roaming and mobility management, similar to a policy and charging rules function in a 4G network. The PCF 60 accesses subscription information, required to make policy decisions, and then provides the appropriate policy rules to control plane functions so that they can enforce them.

The NRF 90 maintains an updated repository of all the 5G elements available in the operator's network along with the services provided by each of the elements in the 5G core that are expected to be instantiated, scaled and terminated without or minimal manual intervention. It allows other NF instances to subscribe and be notified of registrations from NF instances of a given type. The NRF supports service discovery, by receipt of Discovery Requests from NF instances and details which NF instances support specific services.

The NEF 70 is used for exposing network capabilities and events to an AF.

As shown in Fig. 1, the NFs are connected by means of so-called reference points (N1 to N7) and service based interfaces (Nnrf, Npcf, Nams, Nsmf, Nnef, Naf). This representation of reference points is used for illustrating how data flows are developed. It is to be noted that an AF and the DN may have different interface Naf and N6 to connect with the 5GS.

In order to provide multimedia services, an architecture referred to as IP Multimedia subsystem (IMS) is provided, for example. IMS represents a framework for delivering IP multimedia services. The IMS comprises elements for provision of multimedia services, including signalling and media related network elements

Fig. 2 shows a diagram illustrating an example of a system architecture of an IMS for a communication network based on 5GS in which examples of embodiments are implementable. It is to be noted that in the illustration of Fig. 2 mainly shows parts of a complete architecture which are useful for understanding principles of embodiments of the disclosure. In the IMS, a plurality of so-called call session control functions (CSCF) are provided which fulfill several roles as SIP servers or proxies and are used to process SIP signaling packets in the IMS.

A Proxy CSCF (P-CSCF) 84 represents a SIP proxy that is the first point of contact for the IMS terminal (e.g. UE 10). The P-CSCF functions as a user-network interface which not only protects the network, but also the IMS terminal. The P-CSCF assigned to an IMS terminal before registration, and does not change for the duration of the registration. Furthermore, the P-CSCF is able to inspect every signal and provides subscriber authentication. Moreover, it can establish security association with the IMS terminal. Furthermore, the P-CSCF may include a policy decision function functionality which authorizes media plane resources e.g. quality of service over the media plane, and is used for policy control, bandwidth management, etc. For this, a connection with the PCF 60 via N5 interface is established (in other words, the P-CSCF represents for the PCF 60 and AS.

Furthermore, an interrogating CSCF (l-CSCF) 81 is provided as another SIP function located at the edge of an administrative domain. An address (e.g. IP address) of the I- CSCF 81 can be found by remote servers, so that it is used as a forwarding point (e.g., registering) for SIP packets to this domain. Furthermore, the l-CSCF 81 queries a HSS (described later) to retrieve the address of an serving CSCG (S-CSCF) and assigns it to a user performing SIP registration. Moreover, the l-CSCF 81 forwards SIP request or response to the S-CSCF via Mw interface.

Moreover, a serving CSCF (S-CSCF) 82 is provided and represents a central node of the signaling plane. The S-CSCF 82 is a SIP server and performs also session control. The S-CSCF 82 uses e.g. Diameter Cx interfaces to the HSS so as to download user profiles and upload user-to-S-CSCF associations. All necessary subscriber profile information is loaded from the HSS.

The home subscriber server (HSS) 83 is a master user database that supports the IMS network entities that actually handle calls. The HSS 83 contains subscription-related information (subscriber profiles), performs authentication and authorization of the user, and provides information about the subscriber's location and IP information. It is to be noted that the interface between the HSS 83 and S-CSCF or l-CSCF can be, for example, a legacy diameter based Cx interface or 5G SBI based N70 interface.

In IMS, conventionally, when a UE registers, for example, for the first time, then the I- CSCF selects and assigns a S-CSCF to the UE. During UE registration process, the I- CSCF performs a HSS query process for checking whether an S-CSCF had been already assigned and for obtaining the S-CSCF address. If there is no S-CSCF assigned for the UE, then the l-CSCF performs another HSS query for retrieving capabilities of registered S-CSCF for the IMS subscription. Based on the retrieved S-CSCF capabilities, the l-CSCF then selects an appropriate S-CSCF for the UE registration.

Conventionally, for selecting a S-CSCF, the l-CSCF performs a process according to the following processes which are listed, for example, in specification 3GPP TS 23.228.

For assigning an S-CSCF by the l-CSCF, the following information is needed in the selection of the S-CSCF: a) Required capabilities for user services, which information is provided for example by the HSS. b) Operator preference on a per-user basis, which information is provided by the HSS (for example, information is obtained via Cx interface or N70 interface). c) Capabilities of individual S-CSCFs in the home network. This is an internal information within the operator's network and may be used in the S-CSCF selection. This information is obtained by the l-CSCF from local configuration information. d) Topological (i.e. P-CSCF) information of where the user is located. This is internal information within the operator's network and may be used in the S-CSCF selection. The P-CSCF name is received in a registration request. The topological information of the P-CSCF is obtained by the l-CSCF in an appropriate manner. e) Topological information of where the S-CSCF is located This is internal information within the operator's network and may be used in the S-CSCF selection. This information is obtained by the l-CSCF from local configuration information. f) Availability of S-CSCFs. This is internal information within the operator's network and may be used in the S-CSCF selection. This information is obtained by the l-CSCF from local configuration information. In 5G SBI based interface, the NF type ICSCF and SCSCF have been introduced for I- CSCF and S-CSCF (see e.g. 3GPP specification TS 29.510). It is to be noted that in 5G, l-CSCF and S-CSCF acts as consumers but they do not provide any SBI Service. Hence it is not compulsory for them to register a profile in the 5G.

However for open authorization (OAuth) based authentication for N70 services, even the NF Consumers have to register the profile with NRF. So l-CSCF and S-CSCF also conduct a registration process of the profile with the 5G network, e.g. the NRF.

In the guidelines for S-CSCF selection at l-CSCF according to 3GPP specifications as presented above provide it is not described in which way the l-CSCF shall discover the S-CSCF and the corresponding capabilities. For this purpose, conventionally, a list of S- CSCF and the capabilities thereof is locally configured.

However, providing such a list is a tedious activity. For example, any new addition or removal of any S-CSCF or any update to feature capabilities of any S-CSCF requires a configuration change at every l-CSCF.

Therefore, according to examples of embodiments of the present invention, it is proposed to use a procedure in which an SBI capable l-CSCF is configured to retrieve S-CSCF information, such as S-CSCF capabilities and S-CSCF address, from a repository element or function, such as the NRF, so as to able to consider such information for S- CSCF selection for SIP interface.

According to examples of embodiments, in order to implement the above indicated procedure, S-CSCF is configured, as an SBI capable S-CSCF, to provide a network repository, such as the NRF, with profile information, such as capability related information (e.g. in the form of s-cscf capabilities) and address related information (e.g. in the form of s-cscf address in URI format for SIP traffic). For example, this profile information can be included as additional details in the information which is registered at the NRF, for example in the S-CSCF Profile which S-CSCF registers at the NRF using SBI interface. On the other hand, the l-CSCF can use this information for S-CSCF selection. Basically, according to examples of embodiments, the basic selection criteria for S-CSCF may remain unchanged at the l-CSCF, compared to the conventional method. According to examples of embodiments, the l-CSCF conducts a discovery process for obtaining S- CSCF information, such as a list of S-CSCF and the corresponding capabilities, from a central instance, such as the NRF, instead of being dependent of S-CSCF details configured locally at the l-CSCF.

That is, according to examples of embodiments, in the process for assigning an S-CSCF by the l-CSCF, the following information is used: a) Required capabilities for user services, which information is provided for example by the HSS, similar to the conventional example described above. b) Operator preference on a per-user basis, which information is provided by the HSS (for example, information is obtained via Cx interface or N70 interface), similar to the conventional example described above. c) Capabilities of individual S-CSCFs in the home network. This is an internal information within the operator's network and may be used in the S-CSCF selection. This information is obtained by the l-CSCF from the NRF. d) Topological (i.e. P-CSCF) information of where the user is located.

This is internal information within the operator's network and may be used in the S-CSCF selection. The P-CSCF name is received in a registration request. The topological information of the P-CSCF is obtained by the l-CSCF in an appropriate manner, similar to the conventional example described above. e) Topological information of where the S-CSCF is located

This is internal information within the operator's network and may be used in the S-CSCF selection. This information is derived by the l-CSCF from the information obtained from the NRF, i.e. locality information present in the profile information (C-CSCF profile) at the NRF is considered in the S-CSCF selection. f) Availability of S-CSCFs. This is internal information within the operator's network and may be used in the S-CSCF selection. According to examples of embodiments, the l-CSCF considers information present in the profile information (C-CSCF profile) at the NRF in the S-CSCF selection, such as load, priority and capacity information. Fig. 3 shows a signaling diagram explaining an example of a procedure for selecting a S-CSCF according to examples of embodiments.

In Fig. 3. First, a registration process of IMS entities at the NRF is executed. Specifically, HSS, S-CSCF and l-CSCF take the role of service consumer and the NRF takes the role of service producer, exposing the Nnrf NFManagement service with the NFRegister service operation.

In S310, the HSS sends a network function management message including a NF registration request indicating the NF type indication (here HSS) to the NRF 90 via the Nnrf interface.

Once the NRF receives the request, it authenticates and verifies it. The NRF then uses received information to create a new resource. Then, the NRF acknowledges the creation of the resource by returning a response to the HSS in S315.

In S320, the S-CSCF conducts a registration process with the NRF for registering the S- CSCF profile. In this connection, according to examples of embodiments, also details for SIP interface are included in the profile information.

Specifically, for this purpose, in S330, the S-CSCF sends a network function management message including a NF registration request indicating the NF type indication (here S-CSCF) to the NRF 90 via the Nnrf interface. Furthermore, the profile information provided to the NRF 90 includes S-CSCF SIP URO information, and an indication of S-CSCF capabilities. For example, the profile information is encoded as a structured data type in a JSON.

In other words, the S-CSCF profile information provided in S330 is enhanced with information related to S-CSCF capabilities, S-CSCF SIP URI address, S-CSCF priority, load and capacity for SIP interface.

Once the NRF receives the request, it authenticates and verifies it. The NRF then uses information, such as the URI of the S-CSCF, to create a new resource. Then, the NRF acknowledges the creation of the resource by returning a response to the S-CSCF in S335. In S340, the l-CSCF sends a network function management message including a NF registration request indicating the NF type indication (here l-CSCF) to the NRF 90 via the Nnrf interface.

Once the NRF receives the request, it authenticates and verifies it. The NRF then uses received information to create a new resource. Then, the NRF acknowledges the creation of the resource by returning a response to the HSS in S345.

In S350, the l-CSCF conducts a discovery process. During discovery the l-CSCF takes the role of a service consumer and the NRF takes the role of the service producer, exposing the Nnrf NFDiscovery service with the NFDiscover service operation. Specifically, the l-CSCF sends a network function management message including a NF search request indicating the NF type indication (here HSS) to the NRF 90 via the Nnrf interface.

In S355, after querying e.g. for a list of HSS which registered, i.e. the registered and stored profiles of corresponding NFs (i.e. HSS), for matches against a query list received from the l-CSCF. The list of matches is sent from the NRF to the l-CSCF in the body of a response in S355.

In S360, the l-CSCF, for preparing a S-CSCF selection e.g. For registration of a new UE, starts a process for obtaining the S-CSCF profile information from the NRF.

That is, in S370, the l-CSCF conducts a discovery process during which the l-CSCF takes the role of a service consumer and the NRF takes the role of the service producer, Specifically, the l-CSCF sends a network function management message including a NF search request indicating the NF type indication (here S-CSCF) to the NRF 90 via the Nnrf interface.

In S375, after querying e.g. for a list of S-CSCF which registered, i.e. the registered and stored profiles of corresponding NFs (i.e. S-CSCFs), for matches. The list of matches is sent from the NRF to the l-CSCF in the body of a response in S375. That is, the l-CSCF obtains a list of S-CSCF profiles from the NRF. With regard to Fig. 4, a process is described which is related to a registration of a new UE in the IMS and the corresponding S-CSCF selection using the information obtained from the NRF.

In S410, after a UE (e.g UE 10) has obtained IP connectivity, it can perform the IM registration. To do so, the UE sends the Register information flow to the proxy (i.e. the P-CSCF), which includes information such as Public User Identity, Private User Identity, home network domain name, UE IP address, Instance Identifier, and the like.

In S420, upon receipt of the register information flow, the P-CSCF examines the "home domain name" to discover the entry point to the home network (i.e. the l-CSCF). The P- CSCF sends the register information flow to the l-CSCF (P-CSCF address/name, Public User Identity, Private User Identity, P-CSCF network identifier, UE IP address). A name- address resolution mechanism can be utilised in order to determine the address of the home network from the home domain name. lnS430, the l-CSCF conducts a HSS selection based on information obtained from the NRF, i.e. information obtained in S315, for example.

In S440, the l-CSCF sends authorization request for the UE to the HSS for registration in the IMS. The HSS checks whether the user of the UE is registered already.

In S445, the HSS sends a response to the authorization request to the l-CSCF. The response may contain the S-CSCF name, if it is known by the HSS, or the S-CSCF capabilities, if it is necessary to select a new S-CSCF. When capabilities are returned, the l-CSCF can construct a name from the capabilities returned.

In S460, the l-CSCF starts S-CSCF selection. According to examples of embodiments, the l-CSCF uses capability information received from the HSS and S-CSCF profiles received from NRF, instead of using any locally configured S-CSCF list.

In S470, the l-CSCF sends SIP register information fo the SCSCF selected in S460.

It is to be noted that the signalling described in connection with Figs. 3 and 4 is related to a S-CSCF selection during a UE registration. However, the concept described above is applicable for any S-CSCF selection, for example S-CSCF selection during terminating call for unregistered services.

By means of the above described procedure, it is possible that local configuration at I- CSCF can be avoided, so that flexibility of dynamic S-CSCF addition, removal, feature capability update is improved by leveraging, for example, 5G SBI Nnrf_NFManagement API and Nnrf_NFDiscovery API.

With regard to the NF profile, for example, according to examples of embodiments of the invention, a NF type indicating scscflnfoList can be established which comprises specific data for the S-CSCF. As a key of a map related to the SCSF information list, a (unique) valid JSON string may be used, for example.

Furthermore, a servedScscflnfoList as an attribute containing all the scscflnfo attributes locally configured in the NRF or the NRF received during NF registration can be provided. The key of the map may be a NF instance ID (nflnstanceld) to which the map entry belongs to.

Regarding the S-CSCF information provided with the list, the following parameters can be used.

1) URI, which represents URI of S-CSCF having a dedicated FQDN or a generic FQDN;

2) capabilities, which indicates the capabilities supported by the S-CSCF;

3) priority, which indicates the priority for the S-CSCF for the SIP interface;

4) load, which indicates the load for the S-CSCF for the SIP interface;

5) capacity, which indicates the capacity for the S-CSCF for the SIP interface.

Additionally, according to some examples of embodimetns, additional information can be included in the S-CSCF information. For example, a scheme indicating TCP, UDP or TLS may be indicated. Furthermore, an IP address (e.g. IPv4Address/IPv6 address), a port and the like can also be added to the S-CSCF information, which would allow to avoid DNS look.

That is, according to examples of embodiments, the S-CSCF is configured to include its capabilities and SIP address details in the profile it registers in the NRF. Furthermore, the l-CSCF is configured to select the S-CSCF based on the S-CSCF profiles retrieved from the NRF. Moreover, the NRF stores the S-CSCF capabilities in the S-CSCF profile.

Fig. 5 shows a flow chart of a processing executed by a network repository element or function (NRF) 90 which is e.g. part of the communication network of Fig. 1 , as described above. That is, Fig. 5 shows a flowchart related to a processing conducted by a network element or function configured to act as a network repository element or function in a communication network which is used obtain and provide information required for a S- CSCF selection process, as also described in connection with Figs. 3 and 4. As indicated above, the communication network may be based on a 3GPP standard. However, also other communication standards can be used, according to other examples of embodiments.

In S510, the NRF 90 receives, from a network element or function acting as a call session control function in a multimedia subsystem of a communication network, such as from S-CSCF 82 (e.g. via P-CSCF 84 and PFC 80, as indicated in Fig. 2) profile information of the CSCF. According to examples of embodiments, the profile information comprises data to be used in a selection procedure to be conducted for a registration in the multimedia subsystem, such as for the registration of a new UE, as described above.

According to examples of embodiments, the profile information comprises at least one of the following: an identification of the call session control function, such as the URI of the S- CSCF providing the information, e.g. in the form of a dedicated FDQN or a generic FDQN; an indication of communication capability supported by the call session control function (S-CSCF); an indication of a priority for the S-CSCF for SIP interface of the IMS; an indication of a load for the S-CSCF for SIP interface of the IMS; and an indication of a capacity for the S-CSCF for SIP interface of the IMS.

In addition, according to examples of embodiments, the profile information may further comprise at least one of the following: an indication of communication scheme (e.g. scheme indicating TCP, UDP, TLS or the like); an IP address of the S-CSCF (e.g. IPv4 address, IPv6 address); and an indication of a port used by the S-CSCF, allowing to avoid, for example, DNS lookup.

In S520, the profile information being received in S510 is stored.

In S530, the stored profile information are processed, for example for a transmission thereof in response to a discovery process signaling from a network element or function acting e.g. as an l-CSCF.

According to further examples of embodiments, in addition to the profile information, the NFR 90 receives further registration information from different entities in the IMS. For example, the NRF 90 receives registration information from one or more of the following sources (see also Fig. 3, for example): a home subscriber server (e.g. HSS 83), an I- CSCF (e.g. I-CSCF 81), and (other) S-CSCF.

Fig. 6 shows a flow chart of a processing executed by a call session control function , i.e. an l-CSCF 81) which is e.g. part of the IMS of Fig. 2, as described above. That is, Fig. 6 shows a flowchart related to a processing conducted by a network element or function configured to act as an I--CSCF in the IMS which is used obtain and process information required for a S-CSCF selection process, as also described in connection with Figs. 3 and 4. As indicated above, the communication network may be based on a 3GPP standard. However, also other communication standards can be used, according to other examples of embodiments.

In S610, the l-CSCF 81 conducts a discovery process for searching for network elements or functions capable of acting as a call session control function (i.e. S- CSCF) for a UE in the IMS. The discovery process is conducted with the NRF 90.

In S620, in the discovery process, the l-CSCF 81 obtains a list comprising profile information of at least one network element or function capable of acting as a S-CSCF.

According to examples of embodiments, the profile information comprises at least one of the following: an identification of the call session control function, such as the URI of the S- CSCF providing the information, e.g. in the form of a dedicated FDQN or a generic FDQN; an indication of communication capability supported by the call session control function (S-CSCF); an indication of a priority for the S-CSCF for SIP interface of the IMS; an indication of a load for the S-CSCF for SIP interface of the IMS; and an indication of a capacity for the S-CSCF for SIP interface of the IMS.

In addition, according to examples of embodiments, the profile information may further comprise at least one of the following: an indication of communication scheme (e.g. scheme indicating TCP, UDP, TLS or the like); an IP address of the S-CSCF (e.g. IPv4 address, IPv6 address); and an indication of a port used by the S-CSCF, allowing to avoid, for example, DNS lookup.

In S630, the l-CSCF 81 conducts a registration process for a communication element or function (e.g. the UE 10) registering in the IMS (see also Fig. 3).

In S640, the l-CSCF 81 selects a S-CSCF to be assigned to the communication element or function (i.e. UE 10). According to examples of embodiments, the selection of the S- CSCF is based on the list obtained from the NRF 90 and comprising the profile information (it is to be noted that the selection may consider also other information obtained, for example, from the HSS 83)..

According to examples of embodiments, the selection of the S-CSCF is based on at least one of a priority indicated in the profile information for a S-CSCF for a SIP interface of the IMS, a load indicated in the profile information for the S-CSCF for a SIP interface of the IMS, and a capacity indicated in the profile information for the S-CSCF for a SIP interface of the IMS.

According to further examples of embodiments, the l-CSCF 81 obtains topological (i.e. locality related) information for the S-CSCF from the profile information. Furthermore, according to examples of embodiments, in the selection of the S-CSCF, the l-CSCF 81 uses also information obtained from the HSS 81 of the communication network.

Fig. 7 shows a diagram of a communication element or function acting as a network repository function (NRF) 90 according to some examples of embodiments, as described in connection with Figs. 1 to 4, which is configured to conduct a processing according to examples of embodiments of the disclosure. It is to be noted that the network element or function acting as the NRF 90 may include further elements or functions besides those described herein below. Furthermore, even though reference is made to a network element or function, the element or function may be also another device or function having a similar task, such as a chipset, a chip, a module, an application etc., which can also be part of a network element or attached as a separate element to a network element, or the like. It should be understood that each block and any combination thereof may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry.

The NRF 90 shown in Fig. 7 may include a processing circuitry, a processing function, a control unit or a processor 901 , such as a CPU or the like, which is suitable for executing instructions given by programs or the like related to the control procedure. The processor 901 may include one or more processing portions or functions dedicated to specific processing as described below, or the processing may be run in a single processor or processing function. Portions for executing such specific processing may be also provided as discrete elements or within one or more further processors, processing functions or processing portions, such as in one physical processor like a CPU or in one or more physical or virtual entities, for example. Reference signs 902 and 903 denote input/output (I/O) units or functions (interfaces) connected to the processor or processing function 901. The I/O units 902 may be used for communicating with the communication network, such as elements or functions shown in Fig. 1. The I/O units 903 may be used for communicating with IMS elements or functions, such as the P-CSCF shown in Fig. 2. The I/O units 902 and 903 may be combined units including communication equipment towards several entities, or may include a distributed structure with a plurality of different interfaces for different entities. Reference sign 904 denotes a memory usable, for example, for storing data and programs to be executed by the processor or processing function 901 and/or as a working storage of the processor or processing function 901. It is to be noted that the memory 904 may be implemented by using one or more memory portions of the same or different type of memory.

The processor or processing function 901 is configured to execute processing related to the above described control processing. In particular, the processor or processing circuitry or function 901 includes one or more of the following sub-portions. Sub-portion 9011 is a processing portion which is usable as a portion for receiving profile information. The portion 9011 may be configured to perform processing according to S510 of Fig. 5. Furthermore, the processor or processing circuitry or function 901 may include a sub portion 9012 usable as a portion for storing the profile information. The portion 9012 may be configured to perform a processing according to S520 of Fig. 5. In addition, the processor or processing circuitry or function 901 may include a sub-portion 9013 usable as a portion for transmitting profile information. The portion 9013 may be configured to perform a processing according to S530 of Fig. 5.

Fig. 8 shows a diagram of a communication element or function acting as a call session control function, in particular as an l-CSCF 81 according to some examples of embodiments, as described in connection with Figs. 1 to 4, which is configured to conduct a processing according to examples of embodiments of the disclosure. It is to be noted that the network element or function acting as the l-CSCF 81 may include further elements or functions besides those described herein below. Furthermore, even though reference is made to a network element or function, the element or function may be also another device or function having a similar task, such as a chipset, a chip, a module, an application etc., which can also be part of a network element or attached as a separate element to a network element, or the like. It should be understood that each block and any combination thereof may be implemented by various means or their combinations, such as hardware, software, firmware, one or more processors and/or circuitry.

The l-CSCF 81 shown in Fig. 8 may include a processing circuitry, a processing function, a control unit or a processor 811, such as a CPU or the like, which is suitable for executing instructions given by programs or the like related to the control procedure. The processor 811 may include one or more processing portions or functions dedicated to specific processing as described below, or the processing may be run in a single processor or processing function. Portions for executing such specific processing may be also provided as discrete elements or within one or more further processors, processing functions or processing portions, such as in one physical processor like a CPU or in one or more physical or virtual entities, for example. Reference signs 812 and 813 denote input/output (I/O) units or functions (interfaces) connected to the processor or processing function 811. The I/O units 812 may be used for communicating with the IMS network parts, such as the CSCF elements or functions shown in Fig. 2. The I/O units 813 may be used for communicating with the HSS shown in Fig. 2. The I/O units 812 and 813 may be combined units including communication equipment towards several entities, or may include a distributed structure with a plurality of different interfaces for different entities. Reference sign 814 denotes a memory usable, for example, for storing data and programs to be executed by the processor or processing function 811 and/or as a working storage of the processor or processing function 811. It is to be noted that the memory 814 may be implemented by using one or more memory portions of the same or different type of memory.

The processor or processing function 811 is configured to execute processing related to the above described control processing. In particular, the processor or processing circuitry or function 811 includes one or more of the following sub-portions. Sub-portion 8111 is a processing portion which is usable as a portion for conducting a discovery process. The portion 8111 may be configured to perform processing according to S610 of Fig. 6. Furthermore, the processor or processing circuitry or function 811 may include a sub-portion 8112 usable as a portion for obtaining profile information. The portion 8112 may be configured to perform a processing according to S620 of Fig. 6. In addition, the processor or processing circuitry or function 811 may include a sub-portion 8113 usable as a portion for conducting a registration process. The portion 8113 may be configured to perform a processing according to S630 of Fig. 6. Moreover, the processor or processing circuitry or function 811 may include a sub-portion 8114 usable as a portion for conducting a selection. The portion 8114 may be configured to perform a processing according to S640 of Fig. 6.

It is to be noted that examples of embodiments of the disclosure are applicable to various different network configurations. In other words, the examples shown in the above described figures, which are used as a basis for the above discussed examples, are only illustrative and do not limit the present disclosure in any way. That is, additional further existing and proposed new functionalities available in a corresponding operation environment may be used in connection with examples of embodiments of the disclosure based on the principles defined.

According to a further example of embodiments, there is provided, for example, an apparatus for use by a communication network control element or function configured to act as a network repository element or function in a communication network, the apparatus comprising means configured to receive, from a network element or function acting as a call session control function in a multimedia subsystem of a communication network, profile information of the call session control function, the profile information comprises data to be used in a selection procedure to be conducted for a registration in the multimedia subsystem, means configured to store the profile information being received, and means configured to process the stored profile information for transmission thereof in response to a discovery process signaling from a network element or function acting as an interrogating call session control function in the multimedia subsystem.

Furthermore, according to some other examples of embodiments, the above defined apparatus may further comprise means configured to conduct at least one of the processing defined in the above described methods, for example a method according to that described in connection with Fig. 5.

According to a further example of embodiments, there is provided, for example, an apparatus for use by a communication network control element or function configured to act as a call session control element or function in a multimedia subsystem of a communication network, the apparatus comprising means configured to conduct a discovery process for searching for network elements or functions capable of acting as a call session control function in a multimedia subsystem of a communication network, the discovery process being conducted with a network repository element or function of a communication network, and means configured to obtain, in the discovery process, a list comprising profile information of at least one network element or function capable of acting as a call session control function.

Furthermore, according to some other examples of embodiments, the above defined apparatus may further comprise means configured to conduct at least one of the processing defined in the above described methods, for example a method according to that described in connection with Fig. 6. According to a further example of embodiments, there is provided, for example, a non- transitory computer readable medium comprising program instructions for causing an apparatus to perform, when used in a communication network control element or function configured to act as a network repository element or function in a communication network a processing comprising receiving, from a network element or function acting as a call session control function in a multimedia subsystem of a communication network, profile information of the call session control function, the profile information comprises data to be used in a selection procedure to be conducted for a registration in the multimedia subsystem, storing the profile information being received, and processing the stored profile information for transmission thereof in response to a discovery process signaling from a network element or function acting as an interrogating call session control function in the multimedia subsystem.

According to a further example of embodiments, there is provided, for example, a non- transitory computer readable medium comprising program instructions for causing an apparatus to perform, when used in a communication network control element or function configured to act as a call session control element or function in a multimedia subsystem of a communication network, a processing comprising conducting a discovery process for searching for network elements or functions capable of acting as a call session control function in a multimedia subsystem of a communication network, the discovery process being conducted with a network repository element or function of a communication network, and obtaining, in the discovery process, a list comprising profile information of at least one network element or function capable of acting as a call session control function.

By means of embodiments of the present invention, it is possible to provide a mechanism allowing to avoid a local configuration at l-CSCF and to improve the flexibility of dynamic S-CSCF addition, removal, feature capability update by leveraging 5G SBI Nnrf_NFManagement API and Nnrf_NFDiscovery API.

It should be appreciated that

- an access technology via which traffic is transferred to and from an entity in the communication network may be any suitable present or future technology, such as WLAN (Wireless Local Access Network), WiMAX (Worldwide Interoperability for Microwave Access), LTE, LTE-A, 5G, Bluetooth, Infrared, and the like may be used; additionally, embodiments may also apply wired technologies, e.g. IP based access technologies like cable networks or fixed lines.

- embodiments suitable to be implemented as software code or portions of it and being run using a processor or processing function are software code independent and can be specified using any known or future developed programming language, such as a high- level programming language, such as objective-C, C, C++, C#, Java, Python, Javascript, other scripting languages etc., or a low-level programming language, such as a machine language, or an assembler.

- implementation of embodiments is hardware independent and may be implemented using any known or future developed hardware technology or any hybrids of these, such as a microprocessor or CPU (Central Processing Unit), MOS (Metal Oxide Semiconductor), CMOS (Complementary MOS), BiMOS (Bipolar MOS), BiCMOS (Bipolar CMOS), ECL (Emitter Coupled Logic), and/or TTL (Transistor-Transistor Logic).

- embodiments may be implemented as individual devices, apparatuses, units, means or functions, or in a distributed fashion, for example, one or more processors or processing functions may be used or shared in the processing, or one or more processing sections or processing portions may be used and shared in the processing, wherein one physical processor or more than one physical processor may be used for implementing one or more processing portions dedicated to specific processing as described,

- an apparatus may be implemented by a semiconductor chip, a chipset, or a (hardware) module including such chip or chipset;

- embodiments may also be implemented as any combination of hardware and software, such as ASIC (Application Specific 1C (Integrated Circuit)) components, FPGA (Field- programmable Gate Arrays) or CPLD (Complex Programmable Logic Device) components or DSP (Digital Signal Processor) components.

- embodiments may also be implemented as computer program products, including a computer usable medium having a computer readable program code embodied therein, the computer readable program code adapted to execute a process as described in embodiments, wherein the computer usable medium may be a non-transitory medium.

Although the present disclosure has been described herein before with reference to particular embodiments thereof, the present disclosure is not limited thereto and various modifications can be made thereto.