NETWORK

TECHNICAL FIELD

Embodiments herein relate to an IMS node, an application server and methods therein. In some aspects, they relate to selecting one or more application servers in an Internet Protocol (IP) Multimedia Subsystem (IMS) network, in a communications network.

BACKGROUND

In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and/or User Equipments (UE), communicate via a Wide Area Network or a Local Area Network such as a Wi-Fi network or a cellular network comprising a Radio Access Network (RAN) part and a Core Network (CN) part. The RAN covers a geographical area which is divided into service areas or cell areas, which may also be referred to as a beam or a beam group, with each service area or cell area being served by a radio network node such as a radio access node e.g., a Wi-Fi access point or a radio base station (RBS), which in some networks may also be denoted, for example, a NodeB, eNodeB (eNB), or gNB as denoted in Fifth Generation (5G) telecommunications. A service area or cell area is a geographical area where radio coverage is provided by the radio network node. The radio network node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio network node.

3GPP is the standardization body for specify the standards for the cellular system evolution, e.g., including 3G, 4G, 5G and the future evolutions. Specifications for the Evolved Packet System (EPS), also called a Fourth Generation (4G) network, have been completed within the 3rd Generation Partnership Project (3GPP). As a continued network evolution, the new releases of 3GPP specifies a 5G network also referred to as 5G New Radio (NR).

Multi-antenna techniques can significantly increase the data rates and reliability of a wireless communication system. The performance is in particular improved if both the transmitter and the receiver are equipped with multiple antennas, which results in a Multiple-Input Multiple-Output (MIMO) communication channel. Such systems and/or related techniques are commonly referred to as MIMO.

In addition to faster peak Internet connection speeds, 5G planning aims at higher capacity than current 4G, allowing higher number of mobile broadband users per area unit, and allowing consumption of higher or unlimited data quantities in gigabyte per month and user. This would make it feasible for a large portion of the population to stream high-definition media many hours per day with their mobile devices, when out of reach of Wi-Fi hotspots. 5G research and development also aims at improved support of machine to machine communication, also known as the Internet of things, aiming at lower cost, lower battery consumption and lower latency than 4G equipment.

The Internet Protocol (IP) Multimedia Subsystem (IMS) is a well-known 3GPP standard allowing sessions to be set up between two or more parties for a broad variety of services such as voice or video call, interactive messaging sessions or third party specific applications. A protocol chosen by 3GPP is the Session Initiation Protocol (SIP). SIP provides a mechanism for the registration of UEs and for setting up multimedia sessions. The SIP REGISTER method enables the registration of user agent’s current location and the INVITE method enables the setting up of a session. IMS is being implemented by Public Land Mobile Network (PLMN) operators as an architectural framework for delivering IP multimedia services to their subscribers.

Functional elements in the IMS network

An IMS network comprises several network entities, some of which are discussed here.

Proxy Call Session Control Function (P-CSCF)

The P-CSCF is the first point of contact for a UE connected to the IMS network. It may be located in either a home network or a visited network. It behaves a SIP-proxy, i.e. it accepts requests and services them internally or forwards them on and forwards SIP requests or responses to the UE.

Serving Call Session Control Function (S-CSCF)

The S-CSCF is a SIP server and is the central signaling node in the IMS network and performs session control services for the UE. It handles SIP registrations and is responsible for forwarding SIP messages to the correct application server. The S-CSCF may behave as a SIP-proxy, i.e. it accepts requests and services them internally or forwards them on.

Home Subscriber Server (HSS)

The HSS is a subscriber database comprising subscriber profiles, performs authentication and authorization, and provides information on service provisioned for subscribers and information on the location and IP address of a subscriber.

Application server (AS)

An AS, e.g. a SIP AS, Open Service Access (OSA) AS or a Customized Applications for Mobile network Enhanced Logic (CAMEL) IP Multimedia-Service Switching Function (IM-SSF), offers value added IP Multimedia (IM) services and resides e.g. in a UEs home network or in a third party location. The third party may be a network or simply a stand-alone AS.

As described in 3GPP Technical Specification 23.218, the address of the AS to be contacted in IMS is provisioned in a HSS for an IMS subscriber. This allows the S-CSCF to send the request, when triggering conditions are met (SPTs in TS 23.218), to the AS which will be involved in the session. The form of an AS address is a SIP Uniform Resource Identifier (URI) related to a host domain which will be resolved via Domain Name System (DNS).

This mechanism to address ASs in IMS has been widely deployed in the past years. However, configuring the nodes for proper AS selection to be involved in a session has been proven very complex and time consuming.

SUMMARY

As part of developing embodiments herein a problem was identified by the inventor and will first be discussed.

The IMS network may e.g. comprise two ASs, one located in the west region and one in the east region. An S-CSCF may be located in the west region. The optimal choice when selecting an AS is to search for an AS in the west region. The address of the ASs are as-1.ericsson.com (west) and as-2.ericsson.com (east). The S-CSCF will be provided with as.ericsson.com. This address is part of an Initial Filter Criteria (IFC), this since IFCs should be agnostic to a particular deployment to ease the configuration. The address as.ericsson.com will be resolved by DNS into as-1 and as-2, including the IP addresses of AS-1 and AS-2. Now, depending on the location of the S-CSCF, the DNS returns either as-1 (west) as primary and AS-2 (east) as secondary or vice versa. This is done based on the IP address of the S-CSCF querying the DNS. If the IP address is the IP address of the S-CSCF in the west region, the DNS is configured to return a DNS view with a response as-1 , then as-2. Similarly, when DNS receives a DNS query from the IP address of the east S-CSCF, the DNS view configured shall provide as-2 and then as-1.

All these configurations across different ASs, CSCFs and DNS views are manually administered by an operator, who has to provision and/or configure each DNS view based on the transport IP addresses. Hence, if the IP addresses change or scale, e.g. for networking redundancy purposes, the view in the DNS needs to be updated. E.g. if the S- CSCF is using multiple virtual IPs (VIPs) to query DNS, the DNS view needs to be updated again and again.

Moreover, if a new AS is deployed, or a new S-CSCF is deployed, there is no automation at all to allow the network to be automatically configured with the new AS, without manual administrative tasks involved in the DNS views.

In short, the coupling of the selection of IMS ASs to the transport IP addresses used makes the whole procedure very time consuming and involves a lot of Operation & Maintenance (O&M).

Further, different types of ASs may be required by a multimedia session. E.g. a Voice over LTE (VoLTE) call session requires both a Service Centralization and Continuity AS (SCC-AS) and a Multimedia Telephony AS (MMTel-AS). These different ASs may be standalone ASs, or combined in one AS. There is no standard way for the S- CSCF to know which MMTEL-AS/SCC-AS are combined. By selecting a combined e.g. comprising both the SCC-AS and the MMTel-AS AS for the same user and session, resources, e.g. memory, may be optimized in the combined AS. It is not desired at all that a given user is allocated in SCC-AS-1 and MMTEL-AS-2, since the data for the user registration and multimedia sessions needs to be duplicated in two different combined ASs. This is usually solved by different vendors with proprietary features which, in a multivendor environment, require different configuration and network impact. An object of embodiments herein is to improve the performance of a communications network by a more efficient discovery and selection of one or more ASs in an IMS network in the communications network.

According to an aspect of embodiments herein, the object is achieved by a method performed by an Internet Protocol, IP, Multimedia Subsystem, IMS, node for selecting of one or more application servers in a communications network. The IMS node and the one or more application servers are operating in an IMS network.

During a registration procedure of a first User Equipment, UE, to the IMS network, the IMS node 110 obtains, from a subscriber data node, subscriber data related to the first UE. The subscriber data comprises one or more types of sessions. Each type of session indicates one or more types of application servers to triggered.

Upon establishing a session related to the first UE, the IMS node sends, to a network node, a first request to identify one or more application servers for the session based on the obtained subscriber data and the type of session to be established.

The IMS node receives from the network node, a response to the first request. The response comprises respective data associated to each of one or more identified application servers. For each application server the associated data indicates: A type of the application server, and an instance identity, ID, of the application server.

The IMS node selects a first application server from the one or more identified application servers for establishing the session. The selecting is based on the received respective data, the one or more types of session obtained in the subscriber data and the type of session to be established.

The IMS node establishes the session related to the first UE by sending a message to the selected first application server, the message requesting the selected first application server to establish the session.

According to an another aspect of embodiments herein, the object is achieved by a method performed by an application server for assisting an Internet Protocol, IP, Multimedia Subsystem, IMS, node in selecting one or more application servers in a communications network. The IMS node and the one or more application servers are operating in an IMS network.

During a start-up procedure, the application server registers data associated to the application server in a network node. The data indicates: A type of the application server, and an instance identity, ID, of the application server. The registered data assists the first IMS node to identify the application server and perform a selection of an application server to be used for establishing a session related to a first User Equipment, UE.

The application server establishes a session related the first UE by receiving a message from the IMS node. The message requests the application server to establish the session.

According to an another aspect of embodiments herein, the object is achieved by an Internet Protocol, IP, Multimedia Subsystem, IMS, node configured to select one or more application servers in a communications network. The IMS node and the one or more application servers being adapted to operate in an IMS network The IMS node (110) is further configured to:

- During a registration procedure of a first User Equipment, UE, to the IMS network, obtain, from a subscriber data node, subscriber data adapted to be related to the first UE, which subscriber data is adapted to comprise one or more types of application servers to be triggered in a session,

- upon establishing a session related to the first UE, send, to a network node, a first request to identify one or more application servers for the session, based on the obtained subscriber data and the type of session to be established,

- receive from the network node, a response to the first request, which response is adapted to comprise respective data associated to each of one or more identified application servers, wherein for each application server the associated data is adapted to indicate:

- a type of the application server,

- an instance identity, ID, of the application server,

- select a first application server from the one or more identified application servers for establishing the session, which selecting is adapted to be based on the received respective data, the one or more types of session obtained in the subscriber data and the type of session to be established, and establish the session related to the first UE by sending a message to the selected first application server, the message being adapted to request the selected first application server to establish the session.

According to an another aspect of embodiments herein, the object is achieved by an application server configured to assist an Internet Protocol, IP, Multimedia Subsystem, IMS, node in selecting one or more application servers in a communications network. The IMS node and the one or more application servers being adapted to operate in an IMS network. The application server (131 , 132, 133) further being configured to:

- During a start-up procedure, register data associated to the application server in a network node, which data is adapted to indicate:

- a type of the application server,

- an instance identity, ID, of the application server, and wherein the registered data is adapted to assists the first IMS node to identify the application server and perform a selection of an application server adapted to be used for establishing a session related to a first User Equipment, UE.

- establish a session adapted to be related the first UE (121) by receiving a message from the IMS node (110), which message is adapted to request the application server (131 , 132, 133) to establish the session.

Thanks to that the IMS node obtains the subscriber data comprising the one or more types of application servers to be triggered in the session, it is possible for the IMS node to identify and select one or more application server for the session. The IMS node, upon establishing the session, selects the first application servers by requesting the network node to identify the one or more application servers based on the subscriber data. The selection is performed based on the respective data associated to each of the one or more identified application servers which is received from the network node. The IMS node established the session by sending a message to the selected first application server. In this way, an efficient mechanism for selecting one or more application servers is achieved.

Embodiments herein brings the advantage of an efficient mechanism improving the performance in the communications network. This is achieved by a more efficient discovery and selection of one or more ASs in an IMS network in the communications network, where the IMS node, based on obtained subscriber data and the type of session to be established, receives data associated to one or more identified application servers from the network node, and selects the application server based on the received data. The procedure is possible since the application servers registers data associated to the application server in the network node. This leads to a more efficient selection of application servers in the IMS network, and results in an improved performance in the communications network. BRIEF DESCRIPTION OF THE DRAWINGS

Examples of embodiments herein are described in more detail with reference to attached drawings in which:

Figure 1 is a schematic block diagram illustrating embodiments of a communications network.

Figure 2 is a flowchart depicting embodiments of a method in an IMS node.

Figure 3 is a flowchart depicting embodiments of a method in an application server.

Figure 4 is a flowchart depicting embodiments of a method in a network node.

Figure 5 a-c are signaling diagrams depicting examples of embodiments herein.

Figures 6 a and b are schematic block diagrams illustrating embodiments of an IMS node.

Figures 7 a and b are schematic block diagrams illustrating embodiments of an application server.

Figures 8 a and b are schematic block diagrams illustrating embodiments of a network node.

Figure 9 schematically illustrates a telecommunication network connected via an intermediate network to a host computer.

Figure 10 is a generalized block diagram of a host computer communicating via a base station with a user equipment over a partially wireless connection.

Figures 11 to 14 are flowcharts illustrating methods implemented in a communication system including a host computer, a base station and a user equipment.

DETAILED DESCRIPTION

Embodiments herein relate to a communications network and the selection of one or more application servers in an IMS network.

As mentioned above, the object of embodiments herein is to improve the performance of a communications network by a more efficient discovery and selection of one or more ASs in an IMS network in the communications network. Example embodiments herein may e.g. bring the advantage they enables automation of AS selection and discovery in the IMS network. This may be achieved by introducing the use of and Network Repository Function (NRF) in this procedure, and further by enhancement of I FC data. Further, example embodiments herein may e.g. bring the advantage of a harmonized alignment of the IMS network with the 5G Core (5GC) routing selection and discovery. Yet further, embodiments herein may e.g. bring the advantage of an automated handling of a scale out of IMS ASs. This is since the NRF may notify all S-CSCFs which subscribes to IMS AS Network Function (NF) profile changes. Thus, a new IMS AS is immediately taken into account for new multimedia sessions triggering ASs.

Figure 1 is a schematic overview depicting a communications network 100 wherein embodiments herein may be implemented. The communications network 100 comprises one or more RANs and one or more CNs. The communications network 100 may use 5G NR but may further use a number of other different technologies, such as, 6G, Wi-Fi, Long Term Evolution (LTE), LTE-Advanced, Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications/enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations.

The communications network 100 further comprises an IMS network 105, in which IMS network 105 an IMS node, such as e.g. the IMS node 110, and one or more application servers, such as e.g., the application servers 131, 132, 133, operates. According to embodiments herein the IMS node 110 may be a Serving Call Session Control Function (S-CSCF). The IMS network 105 is an architecture for delivering media content over an IP packet switched transport.

One or more UEs operate in the communication network 100, such as e.g. the first UE 121. The UE 121 may e.g. be 5G-RG, a UE, a remote UE, a wireless device, an NR device, a mobile station, a wireless terminal, an NB-loT device, an MTC device, an eMTC device, a CAT-M device, a WiFi device, an LTE device and an a non-access point (non- AP) STA, a STA, that communicates via a base station such as e.g. a base station 105, one or more Access Networks (AN), e.g. a RAN, to one or more core network (CN) nodes, in one or more CNs, one or more IMS nodes, such as e.g. the IMS node 110, or one or more application servers, such as e.g. the application server 131 , 132, 133, in the IMS network 105. The terminal 120 may communicate with one or more CN nodes, or IMS nodes, such as the IMS node 110, by a fixed network connection, such as e.g. cable and/or optical fiber. It should be understood by the skilled in the art that “UE” is a nonlimiting term which means any terminal, client, mobile client, IMS client, wireless communication terminal, user equipment, Device to Device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablets or even a car or any small base station communicating within a cell.

Subscriber data nodes, such as e.g. a subscriber data node 140, may operate in the communications network 100. The subscriber data node 140 may e.g. operate in the IMS network 105, the CN, or be connected to said IMS network 105 or CN. The subscriber data node 140 stores and manages subscriber data related to UEs, such as e.g. the first UE 121. According to embodiments herein the subscriber data node 140 may be a Home Subscriber Server (HSS).

Network nodes, such as e.g. the network node 150, may operate in the communications network 100. The network node 150 may e.g. operate in the CN. The network node may provide service registration and discovery functions to network functions in the communications network 100. According to embodiments herein the network node 150 may be a Network Repository Function (NRF).

Base stations such as the base station 101, operate in the wireless communications network 100. The base station 101 provides one or more cells such as a first cell 11. The base station 101 may be a transmission and reception point e.g. a radio access network node such as a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), an NR Node B (gNB), a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point, a Wireless Local Area Network (WLAN) access point or an Access Point Station (AP STA), an access controller, or any other network unit capable of communicating with UEs, such as the terminal 120, within the first cell 11 , served by the base station 101. The base station 101 may be referred to as a serving radio network node and communicates with the terminal 120 with Downlink (DL) transmissions to the terminal 120 and Uplink (UL) transmissions from the terminal 120. Methods according to embodiments herein are performed by the IMS node 110, and the application server 131, 132, 133. These nodes may be Distributed Nodes (DN)s and functionality, e.g. comprised in a cloud 160 as shown in Figure 1 may be used for performing or partly performing the methods.

Example embodiments herein allows nodes in the IMS network 105, such as the first IMS node 110, to discover and select one or more ASs, such as the one or more application servers 131 , 132, e.g. by using the 5GC capabilities for routing, selection and discovery. Thus, the procedure for AS selection and discovery may be improved by leveraging the 5GC NRF capabilities, replacing legacy mechanisms requiring time consuming manual O&M tasks.

Example of embodiments herein may provide a method for handling discovery and selection of one or more application servers 131 , 132, 133. The method may be performed by an IMS node, such as the first IMS node 110. When an IMS AS, such as the one or more application servers 131, 132, 133, starts, it may register its NF profile in a network node, such as the network node 150. The profile may comprise the IP address, the locality and the type of IMS AS of the one or more application server 131 , 132, 133. The type of IMS AS may e.g. be a SCC-AS and/or a MMTel-AS. The profile may further indicate that the application server is a combined application server, e.g. an application server comprising both a SCC-AS and an MMTel-AS. The indication may e.g. indicate an instance identity (ID) and the IMS AS type of the combined application server. This way, the first IMS node 110 is aware of the IP address and locality of the one or more application servers 131 , 132, 133, as well as which IMS AS types that are combined and the instance ID of those ASs. Thus, the related NF profiles of the combined application servers may be obtained by the first IMS node 110.

Further, examples of embodiments herein may provide enhancement of iFC data, such as the IMS AS type of each application server to be triggered in session, e.g. a multimedia session. This may enable the first IMS node 110 to be aware of which applications servers, such as the one or more application servers 131 , 132, 133, needed to be discovered in the network node 150, such as the NRF . By this follows that the network node 150 may provide the required data for the specific discovery to the first IMS node 110. E.g., the first IMS node 110 may determine that a certain application server needs to be triggered in the session. The first IMS node 110 may then fetch, such as obtain, the IMS AS type, e.g. from the IFC data, and discover application servers of that type, taking the locality of the first IMS node 110 into account. The network node 150 may then, as part of the logic already standardized, return the preferred application servers, such the one or more application servers 131, 132, 133, to the first IMS node 110. The preferred ASs may be returned sorted according to priority. This may enable the first IMS node 110 select the optimal application server for the session, without requiring any manual configuration.

Yet further, examples of embodiments herein may provide methods for discovery and selection of a second application server to be triggered in the session. When a second AS needs to be triggered after the first AS is triggered, the IMS node 110 may determine that the combined AS can be selected, given that the first AS NF profile comprises the information of the combination. Hence, the IMS AS type associated to the second trigger is used to discover and select, if not already cached due to previous discoveries via NRF, to always select the combined node with no local configuration required in IMS node 110.

A method according to embodiments will now be described from the view of the IMS node 110 together with Figure 2.

Example embodiments of a method performed by the IMS node 110 for selecting of one or more application servers 131 , 132, 133 in the communications network 100, will now be described with reference to a flowchart depicted in Figure 3. The IMS node 110 and the one or more application servers 131 , 132, 133 are operating in the IMS network 105. Any one or more out of the following may apply: The network node 150 is a 5GC NRF node 150, the first IMS node 110 is an S-CSCF 110, and the subscriber data node 140 is an HSS 140.

The method comprises the following actions, which actions may be taken in any suitable order. Actions that are optional are presented in dashed boxes in Figure 2.

Action 201

During a registration procedure of the first UE 121 to the IMS network 105, the IMS node 110 obtains subscriber data related to the first UE 121. The subscriber data is obtained from the subscriber data node 140. The subscriber data comprises one or more types of sessions. Each type of session indicates one or more types of application servers to triggered. The subscriber data may e.g. be obtained by receiving the subscriber data from the subscriber data node 140. The subscriber data may be obtained, or received, in response to request sent, or transmitted, by the IMS node 110 to the subscriber data node 140. The subscriber data may e.g. be an iFC.

Different types of sessions may require one or more different types of application servers to be triggered. The subscriber data may comprise data for one or more type of session. For each type of session, the obtained subscriber data may comprises the one or more types of application servers to be triggered. The one or more types of application servers may further be prioritized. In other words, for each type of session, the subscriber data may comprise a prioritized list of one or more application servers to be triggered when establishing that type of session.

Action 202

Upon establishing a session related to the first UE 121, the IMS node 110 sends a first request to the network node 150. The first request requests to identify one or more application servers for the session based on the obtained subscriber data and the type of session to be established. The IMS node 110 may in some embodiments determine the type of session to be established from a request received from the first UE 121. The request may be for establishing the session, and comprises the type of the session.

In some embodiments, the sending of the first request to the network node 140, further comprises that the IMS node 110 determines the one or more types of application servers to identify. The IMS node 110 may determine the one or more types of application servers e.g. by evaluating the obtained subscriber data. The IMS node 110 may further determine the one or more types of application server to be identified by evaluating obtained subscriber data and taking the type of session to be established into account. As mentioned above, the obtained subscriber data may comprise the one or more types of application servers to be triggered for each type of session. The request may comprise the determined one or more types of application servers.

The type of session to established may, as mentioned above, require more than one type of application server to be triggered. In some embodiments, the first request comprises only the first type of application server to triggered, e.g. the type of application server with the highest priority. In other embodiments, determines more than one, e.g. all, types of application servers to be triggered in session. Then the first request may comprise more than one, e.g. all, different types of applications servers to be triggered for the session to be established.

The first request may further comprise a preferred locality of the one or more application servers to be identified. The preferred locality may e.g. be the same as the locality of the IMS node 110, or it may be a different locality. A locality may e.g. mean the region of the IMS network 105 that IMS node and/or application server is located in. E.g. the IMS network 105 may be divided in two regions, such as ‘east’ and ‘west’. When the IMS node 110 is located in the west region, the locality of the IMS node 110 is ‘west’. In such an example, the preferred locality of the one or more application servers to be identified may also be west. This since the latency for communication between the IMS node 110 and the one or more application servers may be reduced if they are located nearer each other.

In some embodiments, the first request does not comprise a type of application server to be identified. This indicates to the network node 150 that all available application servers of any type is to be identified.

Action 203

The IMS node 110 receives a response to the first request from the network node 150. The response comprises respective data associated to each of one or more identified application servers 131, 132, 133. For each application server 131, 132, 133 the associated data indicates: A type of the application server 131 , 132, 133 and an instance ID of the application server 131 , 132, 133.

An instance ID may mean an identity identifying an identifiable instance of an NF e.g. an IMS AS, such as one of the one or more application servers 131, 132, 133, operating in the communications network 100 and/or the IMS network 105.

The one or more identified application server 131 , 132, 133 may be of the same type, or they may be of different types. This may depend on whether the first request comprises one or more different types of application servers to be identified.

In some embodiments, the associated data comprises one or more application servers 131 , 132, 133 combined with the respective application server 131 , 132, 133.

This may mean that for an application server of a certain type, the associated data of the application server indicates that one or more other application servers of different types are combined, such as e.g. co-located, with the application server. This may be used by the IMS node 110 e.g. if selecting a second application server for the session to be established.

In some embodiments, the associated data further indicates any one or more out of: A locality of the application server 131, 132, 133, and a priority of the one or more application servers 131 , 132, 133. The priority of the one or more application servers 131, 132, 133 may e.g. be based on the locality of the one or more application servers 131 , 132, 133. Additionally, or alternatively, the priority may be based on the load of the one or more application servers. The priority may indicate to the IMS node 110 which of the one or more identified application servers 131 , 132, 133 is the most preferred application server, which is the second most preferred application etc. E.g. an application server may be given a higher priority when located in the same region as the IMS node 110, and/or when the load of the application server is low. Low may e.g. mean lower than one or more other application servers of the same type. If the locality is the same for two or more application servers, and the load is the same, the priority of each application server may be determined by a priority in data associated to each application server and registered in the network node 150. The associated data may be a profile, such as e.g. an NF profile.

The response may further comprise the FQDN and/or the IP address of each of the identified application server 131, 132, 133.

Action 204

The IMS node 110 selects a first application server 131 from the one or more identified application servers 131, 132, 133 for establishing the session. The selecting is based on the received respective data. In some examples, the IMS node 110 selects the application server, e.g. the application server 131, that has the highest priority. In other examples, the IMS node 110 selects the application server that has the same locality as the preferred locality, e.g. the same locality as the IMS node 110.

Action 205

The IMS node 110 establishes the session related to the first UE 120 by sending a message to the selected first application server 131. The message requests the selected first application server 131 to establish the session, the one or more types of session obtained in the subscriber data and the type of session to be established. The message may e.g. be a SIP INVITE message, a SIP REGISTRATION message or another message related to a SIP method.

In some embodiments, IMS node 110 establishes the session by further receiving a response from the selected first application server 131. The response is a response to the message requesting the session to be established. The response may e.g. be a SIP 200 OK message. The message may alternatively be any SIP message defined to indicate a response to the request message, examples of such messages may be any one or more out of: A SIP 1XX message, indicating a provisional response, a 2XX message, indicating a successful response, a 3XX message, indicating a redirection, a 4XX message, indicating a client failure, a 5XX message, indicating a server failure, and a 6XX message, indicating a global failure. The XX in the above examples is meant to be understood as any number that, together with the preceding digit corresponds to a predefined SIP message.

Action 206

Some types of sessions require more than one application server to be triggered.

Therefore, in some embodiments, the IMS node 110 sends, a second request to the network node 150. The request requests to identify one or more second application servers for the session, based on the obtained subscriber data and the type of session to be established. The IMS node 110 may determine that one or more second application servers is to be identified by evaluating the obtained subscriber data and taking the type of session to be established into account.

The second request may, as discussed for the first request above, further comprise a preferred locality of the one or more second application servers to be identified. The preferred locality may e.g. be the same as the locality of the IMS node 110, or it may be a different locality.

Action 207

In some embodiments, the IMS node 110 receives a response to the second request from the network node 150. The response comprises second respective data associated to each of one or more identified second application servers 132, 133. For each second application server 132, 133 the associated data indicates: A type of the application server 132, 133 and an instance ID of the application server 132, 133.

The respective data associated to each of the one or more identified second application servers 132, 133 may further indicate any one or more out of: A locality of the application server 132, 133, a priority of the one or more application servers 132, 133 and one or more application servers 132, 133 combined with the respective application server 132, 133.

As mentioned above, this may mean that for a certain application server of a certain type, the associated data of the certain application server indicates that one or more other application servers of different types are combined, such as e.g. co-located, with the certain application server. This may be used by the IMS node 110 e.g. if selecting a second application server for the session to be established. The priority of the one or more application servers 132, 133 may e.g. be based on the locality of the one or more application servers 132, 133. The priority may indicate to the IMS node 110 which of the one or more identified application servers 132, 133 is the most preferred application server, which is the second most preferred application etc. Additionally, or alternatively, the priority may be based on the load of the one or more application servers. The priority may indicate to the IMS node 110 which of the one or more identified application servers

131 , 132, 133 is the most preferred application server, which is the second most preferred application etc. E.g. an application server may be given a higher priority when located in the same region as the IMS node 110, and/or when the load of the application server is low. Low may e.g. mean lower than one or more other application servers of the same type. If the locality is the same for two or more application servers, and the load is the same, the priority of each application server may be determined by a priority in data associated to each application server and registered in the network node 150. The associated data may be a profile, such as e.g. an NF profile.

The response may further comprise the FQDN and/or the IP address of each of the identified application server 131, 132, 133.

Action 208

In some embodiments, the IMS node 110 selects one or more second application servers 132, 133 from the one or more application servers 131 , 132, 133 for establishing the session. The selecting is based on the received respective data. This may be the case when the IMS node 110 has determined that the session to be established requires more than one type of application server to be triggered, and when the first request requests the network node 150 to identify one or more application servers of more than one type. From this follows that the response to the first request, such a case, comprises more than one type of identified application server.

In some other embodiments, the IMS node 110 selects the one or more second application server 132, 133 by selecting the one or more second application servers 132, 133 based on the second respective data. This may be the case when the response to the first request only comprises the type of application server corresponding to the first selected application server 131, e.g. when first request only requested this type of application server to be identified.

As mentioned above, application servers of different types may be combined, such as co-located. The IMS node 110 may select the one or more second application servers

132, 133 by selecting one or more second application servers that is combined with the first application server 131. Selecting a second application server that is combined with the first application server 131, may increase the performance and efficiency in the communications network. This is since the combined application server may share the same memory and thus, data related to session only needs to be handled and stored in one place. Further, communication latency between the IMS node 110 and the selected first application server 131 and one or more selected second application servers 132, 133 may be decreased.

Action 209

When the one or more second application servers 132, 133, has been selected, the establishment of the session may proceed.

In some embodiments, the IMS node 110 continue to establish the session related to the first UE 120 by sending a message to the one or more selected second application servers 132, 133. The message requests the selected one or more second application servers 132, 133 to establish the session.

As mentioned above, the message may e.g. be a SIP INVITE message, a SIP REGISTRATION message or another message related to a SIP method.

In some embodiments, IMS node 110 continues to establish the session by further receiving a response from the one or more selected second application servers 132, 133. The response is a response to the message requesting the session to be established. The response may e.g. be a SIP 200 OK message. The message may alternatively be any SIP message defined to indicate a response to the request message, examples of such messages may be any one or more out of: A SIP 1XX message, indicating a provisional response, a 2XX message, indicating a successful response, a 3XX message, indicating a redirection, a 4XX message, indicating a client failure, a 5XX message, indicating a server failure, and a 6XX message, indicating a global failure. The XX in the above examples is meant to be understood as any number that, together with the preceding digit corresponds to a predefined SIP message.

A method according to some example embodiments will now be described from the view of the application server 131, 132, 133 together with Figure 3.

Example embodiments of a method performed by the application server 131, 132, 133 for assisting the IMS node 110 in selecting one or more application servers 131, 132, 133 in the communications network 100, will now be described with reference to a flowchart depicted in Figure 3. The IMS node 110 and the one or more application servers 131 , 132, 133 are operating in an IMS network 105. Any one or more out may be applied: The network node 150 may be a 5GC NRF node 150, and the first IMS node 110 may be an S-CSCF 110.

The method comprises the following actions, which actions may be taken in any suitable order. Actions that are optional are presented in dashed boxes in Figure 4.

Action 301

During a start-up procedure, the application server 131, 132, 133 registers data associated to the application server 131 , 132, 133 in the network node 150. The data indicates: A type of the application server 131, 132, 133, and an instance ID of the application server 131, 132, 133. The registered data assists the first IMS node 110 to identify the application server 131 , 132, 133 and perform a selection of an application server to be used for establishing a session related to the first UE 120. This since the IMS node 110 may request the network node to identify the application server 131 , 132, 133 based on the type of session to be established, and send the associated to the IMS node 110. The associated data assists the IMS node 110 to select application server 131 , 132, 133 when establishing the session.

The associated data may further indicate any one or more out of: A locality of the application server 131, 132, 133 and one or more application servers 131, 132, 133 combined with the application server 131 , 132, 133. Additionally, the associated data may indicate a load the application server 131, 132, 133.

As mentioned above, this may mean that for an application server of a certain type, the associated data of the application server indicates that one or more other application servers of different types are combined, such as e.g. co-located, with the application server. This may be used by the IMS node 110 e.g. when selecting a second application server for the session to be established.

Further, as mentioned above, a locality may e.g. mean the region of the IMS network 105 that IMS node and/or application server is located in. E.g. the IMS network 105 may be divided in two regions, such as ‘east’ and ‘west’. When the application server 131 , 132, 133 is located in the west region, the locality of the application server 131, 132, 133 is ‘west’. The application server 131, 132, 133 may send updated load indications to the network node 150. The updated load indications may e.g. be sent periodically and/or aperiodically. When sent aperiodically, the updated load indication may e.g. be sent when the load crosses a threshold. There may be one or more thresholds configured to trigger the application server 131, 132, 133 to send the updated load indication. Action 302

The application server 131 , 132, 133 establishes the session related the first UE 121 by receiving a message from the IMS node 110. The message requests the application server 131 , 132, 133 to establish the session. The message may e.g. be a SIP INVITE message, a SIP REGISTRATION message or another message related to a SIP method.

In some embodiments, the application server 131, 132, 133 establishes the session by further sending a response to the IMS node 110. The response is a response to the message requesting the session to be established. The response may e.g. be a SIP 200 OK message. The message may alternatively be any SIP message defined to indicate a response to the request message, examples of such messages may be any one or more out of: A SIP 1XX message, indicating a provisional response, a 2XX message, indicating a successful response, a 3XX message, indicating a redirection, a 4XX message, indicating a client failure, a 5XX message, indicating a server failure, and a 6XX message, indicating a global failure. The XX in the above examples is meant to be understood as any number that, together with the preceding digit corresponds to a predefined SIP message.

A method according to embodiments will now be described from the view of the network node 150 together with Figure 4.

Example embodiments of a method performed by the network node 150 for assisting the IMS node 110 in selecting an application server from one or more application server 131, 132, 133 in the communications network 100, will now be described with reference to a flowchart depicted in Figure 4. The IMS node 110 and the one or more application server 131 , 132, 133 are operating in the IMS network 105. Any one or more out of: The network node 150 may be a 5GC NRF node 150, the IMS node 110 may be an S-CSCF 110.

The method comprises the following actions, which actions may be taken in any suitable order. Actions that are optional are presented in dashed boxes in Figure 4.

Action 401

The network node 150 obtains respective data associated to each of one or more application server 131 , 132, 133. For each application server 131 , 132, 133 the associated data indicates: A type of the application server 131, 132, 133, and an instance ID of the application server 131 , 132, 133. This may e.g. mean that the network node 150 receives the respective data from each of the one or more application server 131, 132, 133. For each of the one or more application server 131 , 132, 133, the network node 150 may register the obtained data. The data may be registered as a profile, such as e.g. an NF profile, in the network node 150.

In some embodiments, the respective data further indicates a load of the associated application server 131 , 132, 133. The network node 150 may receive updated load indications from the one or more application server 131 , 132, 133. The updated load indications may e.g. be received periodically and/or aperiodically. When received aperiodically, the updated load indication may e.g. be received when the load of an application server node crosses a threshold. There may be one or more thresholds configured to trigger an application server to send the updated load indication.

Action 402

The network node 150 receives, from the IMS node 110, a request, e.g. the first request and/or the second request, to identify one or more application servers for establishing a session related to the first UE 121. The identification is based on the type of session to be established. The request may comprise one or more types of application server to be identified.

The type of session to established may, as mentioned above, require more than one type of application server to be triggered. In some embodiments, the first request comprises only the first type of application server to triggered, e.g. the type of application server with the highest priority. In other embodiments, determines more than one, e.g. all, types of application servers to be triggered in session. Then the first request may comprise more than one, e.g. all, different types of applications servers to be triggered for the session to be established.

The request may further comprise a preferred locality of the one or more application servers to be identified. The preferred locality may e.g. be the same as the locality of the IMS node 110, or it may be a different locality. A locality may e.g. mean the region of the IMS network 105 that IMS node and/or application server is located in. E.g. the IMS network 105 may be divided in two regions, such as ‘east’ and ‘west’. When the IMS node 110 is located in the west region, the locality of the IMS node 110 is ‘west’. In such an example, the preferred locality of the one or more application servers to be identified may also be west. This since the latency for communication between the IMS node 110 and the one or more application servers may be reduced if they are located nearer each other. In some embodiments, the request does not comprise a type of application server to be identified. This indicates to the network node 150 that application servers of all types is to be identified.

Action 403

The network node 150 obtains respective data associated to each of one or more identified application servers 131, 132, 133. Each identified application server is 131 , 132, 133 is of a type to triggered in the session. For each application server 131 , 132, 133 the associated data indicates: A type of the application server 131 , 132, 133 and an instance ID of the application server 131 , 132, 133.

In some embodiments, the network node 150 obtains the data by further identifying the one or more application servers 131, 132, 133. The network node 150 may identify the one or more application servers 131 , 132, 133 based on one or more types of application server to be identified. When the first request does not comprise a type of application server, the network node 150 obtains, and e.g. identifies, respective data of all types.

In some embodiments, the associated data further indicates any one or more out of: A locality of the application server 131, 132, 133, and a priority of the one or more application servers 131 , 132, 133. As mentioned above, the priority of the one or more application servers 131 , 132, 133 may e.g. be based on the locality of the one or more application servers 131 , 132, 133. Additionally, or alternatively, the priority may be based on the load of the one or more application servers. The network node 150 may determine the priority. The priority may indicate to the IMS node 110 which of the one or more identified application servers 131 , 132, 133 is the most preferred application server, which is the second most preferred application etc. E.g. an application server may be given a higher priority when located in the same region as the IMS node 110, and/or when the load of the application server is low. Low may e.g. mean lower than one or more other application servers of the same type. If the locality is the same for two or more application servers, and the load is the same, the priority of each application server may be determined by a priority in obtained data, such as e.g. the profile, associated to each of the one or more identified application servers and registered in the network node 150. The profile may e.g. an NF profile.

The response may further comprise the FQDN and/or the IP address of each of the identified application server 131, 132, 133.

Action 404 The network node 150 sends a response to the request, e.g. the first request and/or the second request, to the IMS node 110. The response comprises the respective data associated to each of the one or more identified application servers 131 , 132, 133 for establishing the session. selection data related to a selection of a second IMS node from the one or more identified second IMS nodes 131, 132, 133.

The associated data may, as mention above, indicate any one or more out of: A priority of each of the identified one or more application servers 131, 132, 133, and a locality of the one or more application servers 131, 132, 133.

Embodiments mentioned above will now be further described and exemplified. The embodiments below is applicable to and may be combined with any suitable embodiment described above.

Figures 5a-c shows an example of embodiments herein. In the examples of Figures 4a and b, the IMS node 110 may be referred to as e.g. the S-CSCF 110, the one or more applications servers 131, 132, 133 may be referred to as e.g. the SCC-AS 131, MMTEL- AS 132 and/or VPN-AS 133, the subscriber data node 140 may be referred to as HSS 140 and the network node 150 may be referred to as e.g. the NRF 150.

In actions 501-503, the SCC-AS 131, MMTEL-AS 132 and VPN-AS 133, such as e.g. the application server 131, 132, 133, starts up and registers its NF profile, such as e.g. data associated to the application server 131 , 132, 133, with the NRF 150, such as e.g. the network node 150.

501. The SCC-AS 131 registers its NF profile, such as data associated to the SCC-AS 131 , with the NRF 150 by sending a message, such as a NF_register message, to the NRF 150. The NF profile comprises data associated to the SCC-AS 131 , such as any one or more out of: the instance ID, the locality and contact information, such as IP address and/or FQDN. The NF profile may further comprise any one or more out of: The type of application server of the SCC-AS 131 and/or one or more application servers, such as the MMTEL-AS 132 and/or VPN-AS 133, the SCC-AS 131 is combined with together with the instance ID of the one or more application servers. 502. The MMTEL-AS 132 registers its NF profile, such as data associated to the MMTEL-AS 132, with the NRF 150 by sending a message, such as a NF_register message, to the NRF 150. The NF profile comprises data associated to the MMTEL-AS 132, such as any one or more out of: the instance ID, the locality and contact information, such as IP address and/or FQDN. The NF profile may further comprise any one or more out of: The type of application server of the MMTEL-AS 132 and/or one or more application servers, such as the SCC-AS 131 and/or VPN-AS 133, the MMTEL-AS 132 is combined with together with the instance ID of the one or more application servers.

503. The VPN-AS 133 registers its NF profile, such as data associated to the VPN-AS 133, with the NRF 150 by sending a message, such as a NF_register message, to the NRF 150. The NF profile comprises data associated to the VPN-AS 133, such as any one or more out of: the instance ID, the locality and contact information, such as IP address and/or FQDN. The NF profile may further comprise any one or more out of: The type of application server of the VPN-AS 133 and/or one or more application servers, such as the SCC-AS 131 and/or MMTEL-AS 132, the VPN-AS 133 is combined with together with the instance ID of the one or more application servers.

504. The first UE 121 registers to the IMS network 105 by performing a IMS registration procedure.

505. The S-CSCF 110, such as the IMS node 110, requests the subscriber data related to the first UE 121 by sending a message, such as e.g. a NhssJmsSDM message to the HSS 140, such as the subscriber data node 140.

506. The S-CSCF 110 receives a response, such as obtains the subscriber data related to the first UE 121, such as e.g. a NhssJmsSDM response message, comprising the iFC, such as the subscriber data, from the HSS 140. The iFC comprises one or more types of application servers, such as e.g. one or more of the SCC-AS 131, MMTEL-AS 132 and the VPN-AS 133, to be triggered in a session, such as e.g. a multimedia session, the subscriber data may further comprise the order the one or more application servers is to be triggered in the session. 507. The first UE 121 initiates, such as establishes, a session towards the IMS network 105. The session may be an IMS session, such as e.g. a video call, voice call and/or a multimedia session.

508. The S-CSCF 110 may evaluate the obtained iFC related to the first UE 121 , e.g. in priority order. Based on the iFC, the S-CSCF 110 may determine that an application server, e.g. one or more of the application servers 131 , 132, 133, needs to be triggered for the session that is to be initiated. The S-CSCF 110 may fetch, such as obtain and/or retrieve, the IMS AS type, such as the type of application server, from the obtained iFC in order to discover, such as identify, the application server. E.g. the S-CSCF 110 may have determined, based on the obtained iFC, that the type is SCC-AS.

509. The S-CSCF 110 discovers, such as identifies, available application servers that is of the type SCC-AS by sending a message to the NRF 150, such as the first request to identify one or more application servers. The message may e.g. a NF Discover message. The message may comprise any one or more out of: The NF type, the type of application server and the preferred locality of the application server.

510. The S-CSCF 110 receives a response, such as the response to the first request, from the NRF 150. The message may e.g. be a NF Discover response message, the response comprises the NF profile, such as the respective data, associated to each of the identified one or more application servers, such as e.g. the SCC-AS 131. The NF profile may comprise the data described in Actions 701-703 above. Based on the received one or more NF profiles, the S-CSCF 110 selects the first application server to be triggered, such as e.g. the SCC-AS 131 , for establishing the session.

511. The S-CSCF 110 sends a message for initiating, such as establishing, the session to the SCC-AS 131, such as the selected first application server 131. The message may be a SIP INVITE message.

512. The S-CSCF 110 may receive a response, e.g. as part of establishing the session, from the SCC-AS 131. The message may be a SIP INVITE message. The response may be sent from the SCC-AS 131 after the SCC-AS 131 has performed procedures related to establishing the session. 513. The S-CSCF 110 may continue to evaluate the obtained iFC related to the first UE 121 , e.g. in priority order. Based on the iFC, the S-CSCF 110 may determine that a second application server, e.g. one or more of the application servers 132, 133, needs to be triggered for the session that is to be initiated. The S-CSCF 110 may fetch, such as obtain and/or retrieve, the IMS AS type, such as the type of application server, from the obtained iFC in order to discover, such as identify, the application server. E.g. the S- CSCF 110 may have determined, based on the obtained iFC, that the type is MMTEL-AS. The S-CSCF 110 may, e.g. based on the received NF profile of the previously selected SCC-AS 131 , determine that the SCC-AS 131 is combined with the MMTEL-AS 132. The S-CSCF 110 may then determine to discover, such as identify, only the MMTEL-AS 132.

514. The S-CSCF 110 may discover, such as identifies, the MMTEL-AS 132 by sending a message to the NRF 150, such as a second request to identify one or more application servers. The message may e.g. a NF Discover message. The message may comprise the instance ID of the MMTEL-AS 132.

514b. (not shown in figure 4a-c) As an alternative, when the S-CSCF 110 has not determined that that MMTEL-AS 132 is combined with the SCC-AS 131 , the S-CSCF 110 discovers, such as identifies, available application servers that is of the type MMTEL-AS by sending a message to the NRF 150, such as the second request to identify one or more application servers. The message may e.g. a NF Discover message. The message may comprise any one or more out of: The NF type, the type of application server and the preferred locality of the application server.

515. The S-CSCF 110 receives a response, such as the response to the second request, from the NRF 150. The message may e.g. be a NF Discover response message. The response comprises the NF profile, such as the respective data, associated to the MMTEL-AS 132. The NF profile may comprise the data described in Actions 701-703 above.

515b. (not shown in figure 4a-c) When the S-CSCF 110 has performed Action 514b above, the S-CSCF 110 receives a response, such as the response to the second request, from the NRF 150. The message may e.g. be a NF Discover response message, the response comprises the NF profile, such as the respective data, associated to each of the identified one or more application servers, such as e.g. the MMTEL-AS 132. The NF profile may comprise the data described in Actions 701-703 above. Based on the received one or more NF profiles, the S-CSCF 110 selects the second application server to be triggered, such as e.g. the MMTEL-AS 132, for establishing the session.

516. The S-CSCF 110 may send a message for initiating, such as establishing, the session to the MMTEL-AS 132, such as the selected second application server 132. The message may be a SIP INVITE message.

517. The S-CSCF 110 may receive a response, e.g. as part of establishing the session, from the MMTEL-AS 132. The message may be a SIP INVITE message. The response may be sent from the MMTEL-AS 132 after the MMTEL-AS 132 has performed procedures related to establishing the session.

518. The S-CSCF 110 may continue to evaluate the obtained iFC related to the first UE 121 , e.g. in priority order. Based on the iFC, the S-CSCF 110 may determine that a third application server, e.g. one or more of the application servers 133, needs to be triggered for the session that is to be initiated. The S-CSCF 110 may fetch, such as obtain and/or retrieve, the IMS AS type, such as the type of application server, from the obtained iFC in order to discover, such as identify, the application server. E.g. the S-CSCF 110 may have determined, based on the obtained iFC, that the type is VPN-AS. The S-CSCF 110 may, e.g. based on the received NF profile of the previously selected SCC-AS 131 and/or MMTEL-AS 132, determine that the SCC-AS 131 and/or MMTEL-AS 132 is combined with the VPN-AS 133. The S-CSCF 110 may then determine to discover, such as identify, only the VPN-AS 133.

519. The S-CSCF 110 may discover, such as identifies, the VPN-AS 133 by sending a message to the NRF 150, such as a third request to identify one or more application servers. The message may e.g. a NF Discover message. The message may comprise the instance ID of the VPN-AS 133.

519b. (not shown in figure 4a-c) As an alternative, when the S-CSCF 110 has not determined that that VPN-AS 133 is combined with the SCC-AS 131 and/or the MMTEL- AS 132, the S-CSCF 110 discovers, such as identifies, available application servers that is of the type VPN-AS by sending a message to the NRF 150, such as the third request to identify one or more application servers. The message may e.g. a NF Discover message. The message may comprise any one or more out of: The NF type, the type of application server and the preferred locality of the application server.

520. The S-CSCF 110 receives a response, such as the response to the third request, from the NRF 150. The message may e.g. be a NF Discover response message. The response comprises the NF profile, such as the respective data, associated to the VPN-AS 133. The NF profile may comprise the data described in Actions 701-703 above.

520b. (not shown in figure 4a-c) When the S-CSCF 110 has performed Action 519b above, the S-CSCF 110 receives a response, such as the response to the third request, from the NRF 150. The message may e.g. be a NF Discover response message. The response comprises the NF profile, such as the respective data, associated to each of the identified one or more application servers, such as e.g. the VPN-AS 133. The NF profile may comprise the data described in Actions 701-703 above. Based on the received one or more NF profiles, the S-CSCF 110 selects the third application server to be triggered, such as e.g. the VPN-AS 133, for establishing the session.

521. The S-CSCF 110 may send a message for initiating, such as establishing, the session to the VPN-AS 132, such as the selected third application server 132. The message may be a SIP INVITE message.

522. The S-CSCF 110 may receive a response, e.g. as part of establishing the session, from the VPN-AS 132. The message may be a SIP INVITE message. The response may be sent from the VPN-AS 133 after the VPN-AS 133 has performed procedures related to establishing the session.

523. The S-CSCF 110 may continue to establish the session for the first UE 121.

As discussed above, the S-CSCF 110 may receive the NF profiles of all types of application servers at the same time, e.g. in Actions 509 and 510 above. In such an example, the S-CSCF 110 does not add the application server type in the message sent to the NRF 150. The S-CSCF 110 may then skip Actions 514-515, 514b-515b, 519-520 and 519b-520b. The S-CSCF 110 may then select any further application servers, such as the MMTEL-AS 132 and/or the VPN-AS 133 based on the already received NF profiles. To perform the method actions, the IMS node 110 may comprise an arrangement depicted in Figure 6a and b. The IMS node 110 is configured to select one or more application servers 131 , 132, 133 in the communications network 100. The IMS node 110 and the one or more application servers 131, 132, 133 are adapted to operate in the IMS network 105. Any one or more out of: The first IMS node 110 may be an S-CSCF 110, the network node 150 may be a 5GC NRF node 150 and the subscriber data node 140 may be an HSS 140.

The IMS node 110 may comprise an input and output interface 600 configured to communicate with e.g. the first UE 121 , the subscriber data node 140, the network node 150 and with network nodes in the communications network 100 and the IMS network 105.

The IMS node 110 is further configured to, e.g. by means of an obtaining unit 610 in the IMS node 110, during a registration procedure of the UE 121 to the IMS network 105, obtain, from a subscriber data node 140, subscriber data adapted to be related to the first UE 121. The subscriber data is adapted to comprise one or more types of sessions. Each type of session is adapted to indicate one or more types of application servers to triggered

The IMS node 110 is further configured to, e.g. by means of a sending unit 620 in the IMS node 110, upon establishing a session related to the first UE 121, send, to the network node 150, a first request to identify one or more application servers for the session, based on the obtained subscriber data and the type of session to be established,

The IMS node 110 may further be configured to, e.g. by means of the sending unit 620 in the IMS node 110, send, to the network node 150, a second request to identify one or more second application servers for the session, based on the obtained subscriber data and the type of session to be established.

The IMS node 110 may be configured to send any one or more out of the first request and the second request by further being configured to determine one or more types of application servers to identify by evaluating the obtained subscriber data. The request may be adapted to comprise the determined one or more types of application servers. The IMS node 110 is further configured to, e.g. by means of a receiving unit 630 in the IMS node 110, receive from the network node 150, a response to the first request. The response is adapted to comprise respective data associated to each of one or more identified application servers 131 , 132, 133. For each application server 131, 132, 133 the associated data is adapted to indicate: A type of the application server 131, 132, 133, and the instance ID of the application server 131 , 132, 133.

The IMS node 110 may further be configured to, e.g. by means of the receiving unit 630 in the IMS node 110, receive from the network node 150, a response to the second request. The response is adapted to comprise second respective data associated to each of one or more identified second application servers 132, 133. For each second application server 132, 133 the associated data is adapted to indicate: A type of the application server 132, 133 and the instance ID of the application server 132, 133.

The associated data may be adapted to comprise one or more application servers 131, 132, 133 combined with the respective application server 131 , 132, 133.

The associated data may further be adapted to indicate any one or more out of: A locality of the application server 131, 132, 133, and a priority of the one or more application servers 131 , 132, 133.

The IMS node 110 is further configured to, e.g. by means of a selecting unit 640 in the IMS node 110, select a first application server 131 from the one or more identified application servers 131, 132, 133 for establishing the session. The selecting is adapted to be based on the received respective data.

The IMS node 110 may further be configured to, e.g. by means of the selecting unit 640 in the IMS node 110, select one or more second application servers 132, 133 from the one or more application servers 131, 132, 133 for establishing the session. The selecting is adapted to be based on the received respective data, the one or more types of session obtained in the subscriber data and the type of session to be established.

The IMS node 110 may further be configured to, e.g. by means of the selecting unit 640 in the IMS node 110, select the one or more second application servers 132, 133 by selecting the one or more second application servers 132, 133 based on the second respective data.

The IMS node 110 may be configured to select the one or more second application servers 132, 133 by selecting one or more second application servers that is combined with the first application server 131. The IMS node 110 is further configured to, e.g. by means of an establishing unit 650 in the IMS node 110, establish the session related to the first UE 120 by sending a message to the selected first application server 131. The message is adapted to request the selected first application server 131 to establish the session.

The IMS node 110 may further be configured to, e.g. by means of the establishing unit 660 in the IMS node 110, continue to establish the session related to the first UE 120 by sending a message to the one or more selected second application servers 132, 133. The message is adapted to request the selected one or more second application servers 132, 133 to establish the session.

The embodiments herein may be implemented through a respective processor or one or more processors, such as the processor 660 of a processing circuitry in the IMS node 110 depicted in Figure 6a, together with respective computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the IMS node 110. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the IMS node 110.

The IMS node 110 may further comprise a memory 670 comprising one or more memory units. The memory comprises instructions executable by the processor 660 in the IMS node 110. The memory 670 is arranged to be used to store e.g. information, messages, indications, subscriber data, data , profile data, service requests, connections, identities, communication data and applications to perform the methods herein when being executed in the IMS node 110.

In some embodiments, a computer program 680 comprises instructions, which when executed by the respective at least one processor 660, cause the at least one processor 660 of the IMS node 110 to perform the actions above.

In some embodiments, a respective carrier 690 comprises the respective computer program 680, wherein the carrier 690 is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

Those skilled in the art will appreciate that the units in the IMS node 110 described above may refer to a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the IMS node 110, that when executed by the respective one or more processors such as the processors described above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a-chip (SoC).

To perform the method actions, the application server 131, 132, 133 may comprise an arrangement depicted in Figure 7a and b. The application server 131 , 132, 133 is configured to assist the IMS node 110 in selecting one or more application servers 131, 132, 133 in the communications network 100. The IMS node 110 and the one or more application servers 131 , 132, 133 are adapted to operate in the IMS network 105. Any one or more out of: The network node 150 is a 5GC NRF node 150, and the first IMS node 110 is an S-CSCF 110.

The application server 131 , 132, 133 may comprise an input and output interface 700 configured to communicate with e.g. the IMS node 110, the network node 150 and with network nodes in the communications network 100 and the IMS network 105.

The application server 131 , 132, 133 is further configured to, e.g. by means of a registering unit 710 in the application server 131 , 132, 133, during a start-up procedure, register data associated to the application server 131 , 132, 133 in the network node 150. The data is adapted to indicate: A type of the application server 131 , 132, 133, an instance ID of the application server 131 , 132, 133. The registered data is adapted to assists the first IMS node 110 to identify the application server 131, 132, 133 and perform a selection of an application server adapted to be used for establishing a session related to a first UE 121. The associated data may further be adapted to indicate any one or more out of: A locality of the application server 131, 132, 133 and one or more application servers 131, 132, 133 combined with the application server 131 , 132, 133.

The application server 131 , 132, 133 is further configured to, e.g. by means of an establishing unit 720 in the application server 131 , 132, 133, establish the session adapted to be related the first UE 121 by receiving a message from the IMS node 110. The message is adapted to request the application server 131, 132, 133 to establish the session.

The embodiments herein may be implemented through a respective processor or one or more processors, such as the processor 730 of a processing circuitry in the application server 131 , 132, 133 depicted in Figure 7a, together with respective computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the application server 131, 132, 133. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the application server 131 , 132, 133.

The application server 131 , 132, 133 may further comprise a memory 740 comprising one or more memory units. The memory 740 comprises instructions executable by the processor 730 in application server 131, 132, 133. The memory 640 is arranged to be used to store e.g. information, messages, indications, subscriber data, data , profile data, service requests, connections, identities, communication data and applications and applications to perform the methods herein when being executed in the application server 131, 132, 133.

In some embodiments, a computer program 750 comprises instructions, which when executed by the respective at least one processor 730, cause the at least one processor 730 of the application server 131, 132, 133 to perform the actions above. In some embodiments, a respective carrier 760 comprises the respective computer program 750, wherein the carrier 760 is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

Those skilled in the art will appreciate that the units in the application server 131, 132, 133 described above may refer to a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the application server 131, 132, 133, that when executed by the respective one or more processors such as the processors described above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a-chip (SoC).

To perform the method actions, the network node 150 may comprise an arrangement depicted in Figure 8a and b. The network node 150 is configured to assist the IMS node 110 in selecting one or more application servers 131 , 132, 133 in the communications network 100. The IMS node 110 and the one or more application servers 131 , 132, 133 are adapted to operate in the IMS network 105. Any one or more out of: The network node 150 may be a 5GC NRF node 150, and the first IMS node 110 may be an S-CSCF 110.

The network node 150 may comprise an input and output interface 700 configured to communicate with e.g. the IMS node 110, the application server 131, 132, 133 and with network nodes in the communications network 100 and the IMS network 105.

The network node 150 is further configured to, e.g. by means of an obtaining unit 810 in network node 150, obtain respective data adapted to be associated to each of one or more application servers 131 , 132, 133. For each application server 131, 132, 133 the associated data is adapted to indicate: A type of the application server 131 , 132, 133, and an instance ID of the application server 131 , 132, 133.

The network node 150 is further configured to, e.g. by means of the obtaining unit 810 in network node 150, obtain respective data adapted to be associated to one or more identified application servers 131 , 132, 133. Each identified application server 131, 132, 133 is adapted to be of a type to be triggered in the session. For each application server 131 , 132, 133 the associated data is adapted to indicate: a type of the application server

131 , 132, 133, and an instance ID of the application server 131 , 132, 133.

The network node 150 is further configured to, e.g. by means of a receiving unit 820 in network node 150, receive, from the IMS node 110, a request to identify one or more application servers to be triggered in a session related to the UE 121. The identification is adapted to be based on the type of session to be established.

The network node 150 is further configured to, e.g. by means of a sending unit 830 in network node 150, send a response to the request to the IMS node 110. The response is adapted to comprise the respective data associated to each of one or more identified application servers 131 , 132, 133. The associated data is adapted to be related to a selection of an application server from the one or more identified second IMS nodes 131,

132, 133.

The embodiments herein may be implemented through a respective processor or one or more processors, such as the processor 840 of a processing circuitry in the network node 150 depicted in Figure 8a, together with respective computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the network node 150. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the network node 150.

The network node 150 may further comprise a memory 850 comprising one or more memory units. The memory 850 comprises instructions executable by the processor 840 in network node 150. The memory 850 is arranged to be used to store e.g. information, messages, indications, subscriber data, data , profile data, service requests, connections, identities, communication data and applications and applications to perform the methods herein when being executed in the network node 150. In some embodiments, a computer program 860 comprises instructions, which when executed by the respective at least one processor 840, cause the at least one processor 840 of the network node 150 to perform the actions above.

In some embodiments, a respective carrier 870 comprises the respective computer program 860, wherein the carrier 870 is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

Those skilled in the art will appreciate that the units in the network node 150 described above may refer to a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the network node 150, that when executed by the respective one or more processors such as the processors described above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a- chip (SoC).

Further Extensions and Variations

With reference to Figure 9, in accordance with an embodiment, a communication system includes a telecommunication network 3210, such as a 3GPP-type cellular network, which comprises an access network 3211 , such as a radio access network, and a core network 3214. The core network 3214 may e.g. comprise the proxy node 110. The access network 3211 comprises a plurality of base stations 3212a, 3212b, 3212c, e.g. the base station 105, such as AP STAs NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 3213a, 3213b, 3213c. Each base station 3212a, 3212b, 3212c is connectable to the core network 3214 over a wired or wireless connection 3215. A first user equipment (UE) such as the terminal 120 and/or a Non-AP STA 3291 located in coverage area 3213c is configured to wirelessly connect to, or be paged by, the corresponding base station 3212c. A second UE 3292 such as another terminal 120 and/or a Non-AP STA in coverage area 3213a is wirelessly connectable to the corresponding base station 3212a. While a plurality of UEs 3291 , 3292 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 3212.

The telecommunication network 3210 is itself connected to a host computer 3230, which may be embodied in the hardware and/or software of a standalone server, a cloud- implemented server, a distributed server or as processing resources in a server farm. The host computer 3230 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The connections 3221, 3222 between the telecommunication network 3210 and the host computer 3230 may extend directly from the core network 3214 to the host computer 3230 or may go via an optional intermediate network 3220. The intermediate network 3220 may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network 3220, if any, may be a backbone network or the Internet; in particular, the intermediate network 3220 may comprise two or more sub-networks (not shown).

The communication system of Figure 9 as a whole enables connectivity between one of the connected UEs 3291 , 3292 and the host computer 3230. The connectivity may be described as an over-the-top (OTT) connection 3250. The host computer 3230 and the connected UEs 3291 , 3292 are configured to communicate data and/or signaling via the OTT connection 3250, using the access network 3211, the core network 3214, any intermediate network 3220 and possible further infrastructure (not shown) as intermediaries. The OTT connection 3250 may be transparent in the sense that the participating communication devices through which the OTT connection 3250 passes are unaware of routing of uplink and downlink communications. For example, a base station 3212 may not or need not be informed about the past routing of an incoming downlink communication with data originating from a host computer 3230 to be forwarded (e.g., handed over) to a connected UE 3291. Similarly, the base station 3212 need not be aware of the future routing of an outgoing uplink communication originating from the UE 3291 towards the host computer 3230.

Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to Figure 10. In a communication system 3300, a host computer 3310 comprises hardware 3315 including a communication interface 3316 configured to setup and maintain a wired or wireless connection with an interface of a different communication device of the communication system 3300. The host computer 3310 further comprises processing circuitry 3318, which may have storage and/or processing capabilities. In particular, the processing circuitry 3318 may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computer 3310 further comprises software 3311 , which is stored in or accessible by the host computer 3310 and executable by the processing circuitry 3318. The software 3311 includes a host application 3312. The host application 3312 may be operable to provide a service to a remote user, such as a UE 3330 connecting via an OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the remote user, the host application 3312 may provide user data which is transmitted using the OTT connection 3350.

The communication system 3300 further includes a base station 3320 provided in a telecommunication system and comprising hardware 3325 enabling it to communicate with the host computer 3310 and with the UE 3330. The hardware 3325 may include a communication interface 3326 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 3300, as well as a radio interface 3327 for setting up and maintaining at least a wireless connection 3370 with a UE 3330 located in a coverage area (not shown in Figure 10) served by the base station 3320. The communication interface 3326 may be configured to facilitate a connection 3360 to the host computer 3310. The connection 3360 may be direct or it may pass through a core network (not shown in Figure 10) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware 3325 of the base station 3320 further includes processing circuitry 3328, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base station 3320 further has software 3321 stored internally or accessible via an external connection.

The communication system 3300 further includes the UE 3330 already referred to. Its hardware 3335 may include a radio interface 3337 configured to setup and maintain a wireless connection 3370 with a base station serving a coverage area in which the UE 3330 is currently located. The hardware 3335 of the UE 3330 further includes processing circuitry 3338, which may comprise one or more programmable processors, applicationspecific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE 3330 further comprises software 3331, which is stored in or accessible by the UE 3330 and executable by the processing circuitry 3338. The software 3331 includes a client application 3332. The client application 3332 may be operable to provide a service to a human or non-human user via the UE 3330, with the support of the host computer 3310. In the host computer 3310, an executing host application 3312 may communicate with the executing client application 3332 via the OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the user, the client application 3332 may receive request data from the host application 3312 and provide user data in response to the request data. The OTT connection 3350 may transfer both the request data and the user data. The client application 3332 may interact with the user to generate the user data that it provides. It is noted that the host computer 3310, base station 3320 and UE 3330 illustrated in Figure 10 may be identical to the host computer 3230, one of the base stations 3212a, 3212b, 3212c and one of the UEs 3291 , 3292 of Figure 9, respectively. This is to say, the inner workings of these entities may be as shown in Figure 10 and independently, the surrounding network topology may be that of Figure 9.

In Figure 10, the OTT connection 3350 has been drawn abstractly to illustrate the communication between the host computer 3310 and the use equipment 3330 via the base station 3320, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UE 3330 or from the service provider operating the host computer 3310, or both. While the OTT connection 3350 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

The wireless connection 3370 between the UE 3330 and the base station 3320 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE 3330 using the OTT connection 3350, in which the wireless connection 3370 forms the last segment. More precisely, the teachings of these embodiments may improve the [select the applicable RAN effect: data rate, latency, power consumption] and thereby provide benefits such as [select the applicable corresponding effect on the OTT service: reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime],

A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 3350 between the host computer 3310 and UE 3330, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection 3350 may be implemented in the software 3311 of the host computer 3310 or in the software 3331 of the UE 3330, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection 3350 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software 3311, 3331 may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 3350 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the base station 3320, and it may be unknown or imperceptible to the base station 3320. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating the host computer’s 3310 measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that the software 3311, 3331 causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 3350 while it monitors propagation times, errors etc.

Figure 11 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 9 and Figure 10. For simplicity of the present disclosure, only drawing references to Figure 11 will be included in this section. In a first step 3410 of the method, the host computer provides user data. In an optional substep 3411 of the first step 3410, the host computer provides the user data by executing a host application. In a second step 3420, the host computer initiates a transmission carrying the user data to the UE. In an optional third step 3430, the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional fourth step 3440, the UE executes a client application associated with the host application executed by the host computer.

Figure 12 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 9 and Figure 10. For simplicity of the present disclosure, only drawing references to Figure 12 will be included in this section. In a first step 3510 of the method, the host computer provides user data. In an optional substep (not shown) the host computer provides the user data by executing a host application. In a second step 3520, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional third step 3530, the UE receives the user data carried in the transmission.

Figure 13 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 9 and Figure 10. For simplicity of the present disclosure, only drawing references to Figure 13 will be included in this section. In an optional first step 3610 of the method, the UE receives input data provided by the host computer. Additionally, or alternatively, in an optional second step 3620, the UE provides user data. In an optional substep 3621 of the second step 3620, the UE provides the user data by executing a client application. In a further optional substep 3611 of the first step 3610, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in an optional third substep 3630, transmission of the user data to the host computer. In a fourth step 3640 of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.

Figure 14 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as an AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 9 and Figure 10. For simplicity of the present disclosure, only drawing references to Figure 14 will be included in this section. In an optional first step 3710 of the method, in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In an optional second step 3720, the base station initiates transmission of the received user data to the host computer. In a third step 3730, the host computer receives the user data carried in the transmission initiated by the base station. When using the word "comprise" or “comprising” it shall be interpreted as nonlimiting, i.e. meaning "consist at least of".

The embodiments herein are not limited to the above described preferred embodiments. Various alternatives, modifications and equivalents may be used.