Key for finding a user equipment subscriber identity

Abstract

A method performed by a user equipment (UE) is provided. The method comprises transmitting a first message to a first network node, and after transmitting the first message, receiving from the first network node a second message which includes a UE key information element (IE). The UE key IE comprises i) a key for finding, within a communication service provider (CSP) domain, UE context information associated with the UE and ii) one or more network identifiers (IDs) identifying a network to which the UE is connected.

Description

KEY FOR FINDING A USER EQUIPMENT SUBSCRIBER IDENTITYTECHNICAL FIELD

[0001] This disclosure relates to a key for finding a user equipment (UE) subscriber identity.BACKGROUND

[0002] Communications service providers (CSPs) desire to expose network capabilities and programmability to external providers such as, for example, application service providers (ASPs) and aggregators. The network exposure function (NEF) supports external exposure of capabilities of network functions. The network function capabilities that can be exposed externally can be categorized as: monitoring capability, provisioning capability, policy / charging capability, network status reporting capability, and analytics reporting capability.

[0003] The monitoring capability is for monitoring a specific event for a UE in the Evolved Packet System (EPS) and the fifth generation system (5GS) and making such monitoring events information available for external exposure via the NEF. The provisioning capability is for allowing an external party to provision information which can be used for a UE in 5GS. The policy / charging capability is for handling quality of service (QoS) and charging policy for a UE based on a request from an external party. The analytics capability is for allowing an external party to acquire analytics information generated by 5GS.

[0004] One common problem in using these services is how to identify a targeted user, device, and / or ongoing session with a temporary or usage specific identifier. One example of the identifier that can be used for identifying a targeted user, device, and / or ongoing session is: generic public subscription identifier (GPSI) which is either a mobile subscriber integrated services digital network number (MSISDN (a.k.a., phone number of E.164 number)) or an external identifier) .

[0005] However, due to privacy reasons, GPSI (MSISDN) is commonly prevented from being used externally while the 5G assigned IP Address, could be subject to network address translators (NATs). Many CSPs separate mobile networks from the public internet using NAT for two main reasons.

[0006] First, a NAT "expands” the IPv4 address range of a CSP. The CSP can assign internal and private IPv4 addresses to UEs in its mobile network. Towards outside, the CSP needs to allocate only some few (public) IPv4 addresses. Second, privacy can be enhanced since UEs and users cannot be tracked by external entities based on their IP addresses (both, for IPv4 and potentially for IPv6).

[0007] Technically, an application client can read its own IP address from a local IP stack. However, there are several aspects to consider. First, the cellular system (e.g., 5GS) supports multiple PDU sessions each of which is assigned with its own IP address and normally a UE has at least 2 PDU sessions active - one for data servicesand another one for voice services. Second, security sandboxing like in a browser prevents the application client from reading the local IP address. Third, IP address pools can be overlapped using, for example, the "IP domain” or data network names (DNNs).

[0008] When an application invokes a network application programming interface (API), information identifying the target UEs may be required in the API request. The 3GPP NEF APIs use GPSI (which is either MSISDN or an external ID) or IP address and IP domain to identify the target UEs. However, in some scenarios (e.g., due to permission or privacy setting), an ASP may not be able to obtain GPSI, and thus other information (e.g., IP address) may be used to identify the target UEs.SUMMARY

[0009] To invoke a network API, an external API invoker needs to identify a specific device (e.g., UE) and / or a specific protocol data unit (PDU) session of the device (especially when multiple PDU sessions are established for the device).

[0010] In one example, when requesting establishment of a QoS flow for an application function (AF) session using QoS API exposed by the NEF, the external API invoker needs to provide a UE IP address and a set of service data flow filters as input. The 5GS uses the UE IP address to find the correct policy control function (PCF), session management function (SMF), and / or user plane function (UPF). In another example, when using monitoring event exposure API, the API invoker needs to provide an MSISDN, an external identifier, or an IP address (v4 or v6) as input.

[0011] However, the following challenges presently exist in using the existing identifiers to invoke a network API.

[0012] 1. IP Address

[0013] When a NAT is deployed between the API invoker and the UE of interest, the external API invoker needs to identify a correct UE and / or a correct PDU session of the UE. To identify the correct UE, the IP address of the UE may be obtained and used. However, many applications that are used these days are browser-based applications and the browser sandbox generally prohibits the access to local network resources. Also, the UE IP address may not be unique within the 5GS since it can be reused in different DNNs. Furthermore, CSPs are generally reluctant to expose UE assigned IP addresses since they are considered privacy sensitive and lead to administrative pains.

[0014] 2. MSISDN

[0015] The MSISDN (i.e., GPSI) is considered privacy related since it is often a static and / or long term identifier. The MSISDN allows tracking of users and usages across different services and applications.

[0016] 3. AF Specific External ID

[0017] The usage of an AF specific external ID (e.g., a network access identifier (NAI)) is currently not specified by the 3GPP standard in sufficient detail.

[0018] 4. No Usage Limitation

[0019] There is no usage limitation associated with the existing identifiers defined in the 3GPP standard. Thus, whoever is in the possession of these identifiers can use the identifiers without restriction. Also, since each of these identifiers is a plain-text-string, anyone can create (intentionally or by accident) the identifiers.

[0020] 5. No Means to Validate

[0021] The API provider function (e.g. , either NEF or PCF) has no means to validate as whether the API invoker is authorized to use provided identifiers unless the identifiers are provisioned to be API invoker specific. However, this is often impractical (e.g., with additional API layers like NEF API provider in front of PCF API provider) and not scalable (stateful persistence of many parameters).

[0022] In a summary, there is currently no identifier which can be reliably used to identify a device (e.g., UE) and / or a device connection (e.g., PDU session) without compromising privacy of the device user when invoking a network API.

[0023] Accordingly, in one aspect of some embodiments, there is provided a method performed by a user equipment, UE. The method comprises transmitting a first message to a first network node; and after transmitting the first message, receiving from the first network node a second message which includes a UE key information element, IE. The UE key IE comprises I) a key for finding, within a communication service provider, CSP, domain, UE context information associated with the UE and ii) one or more network identifiers, IDs, identifying a network to which the UE is connected.

[0024] In another aspect, there is provided a method performed by a first network node. The method comprises obtaining a key; after obtaining the key, storing mapping information which maps the key to user equipment, UE, context information associated with a specific UE; generating a UE key information element, IE, which comprises the obtained key and one or more network identifiers, IDs, identifying a network to which the specific UE is connected; and transmitting to the specific UE a first message including the UE key IE.

[0025] In a different aspect, there is provided a method performed by a first network node. The method comprises receiving from a second network node a first message including a key; determining that the second network node transmitted the key; and after obtaining the key and determining that the second network node transmitted the key, storing mapping information which maps the key to the second network node.

[0026] In a different aspect, there is provided a method performed by a system. The method comprises a first network node transmitting to a second network node a find request for finding a third network node which handles a specific network session of a specific user equipment, UE, wherein the find request includes a key for finding, within a communication service provider, CSP, domain, UE context information associated with the specific UE. The methodfurther comprises after receiving the find request, using the key, the second network node finding the third network node handling the specific network session of the specific UE; and after finding the third network node, the second network node transmitting to the first network node a response to the find request, wherein the response to the find request includes a network node identifier identifying the third network node.

[0027] In a different aspect, there is provided a computer program comprising instructions which when executed by processing circuitry cause the processing circuitry to perform the method of any one of the above embodiments.

[0028] In a different aspect, there is provided a carrier containing the computer program of the above embodiment, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer readable storage medium.

[0029] In a different aspect, there is provided a user equipment, UE. The UE is configured to transmit a first message to a first network node; and after transmitting the first message, receive from the first network node a second message which includes a UE key information element, IE. The UE key IE comprises I) a key for finding, within a communication service provider, CSP, domain, UE context information associated with the UE and ii) one or more network identifiers, IDs, identifying a network to which the UE is connected.

[0030] In a different aspect, there is provided a first network node. The first network node is configured to obtain a key; after obtaining the key, store mapping information which maps the key to user equipment, UE, context information associated with a specific UE; generate a UE key information element, IE, which comprises the obtained key and one or more network identifiers, IDs, identifying a network to which the specific UE is connected; and transmit to the specific UE a first message including the UE key IE.

[0031] In a different aspect, there is provided a first network node. The first network node is configured to receive from a second network node a first message including a key; determine that the second network node transmitted the key; and after obtaining the key and determining that the second network node transmitted the key, store mapping information which maps the key to the second network node.

[0032] In a different aspect, there is provided a system comprising a first network node, a second network node, and a third network node. The system is configured to, using the first network node, transmit to the second network node a find request for finding the third network node which handles a specific network session of a specific user equipment, UE, wherein the find request includes a key for finding, within a communication service provider, CSP, domain, UE context information associated with the specific UE. The system is further configured to, after the second network node receiving the find request, using the second network node, find, using the key, the third network node handling the specific network session of the specific UE. The system is further configured to, after finding the third network node, using the second network node, transmit to the first network node a response to the find request, wherein the response to the find request includes a network node identifier identifying the third network node.

[0033] In a different aspect, there is provided an apparatus comprising: a processing circuitry; and a memory, said memory containing instructions executable by said processing circuitry, whereby the apparatus is operative to perform the method of any one of the above embodiments.

[0034] According to some embodiments of this disclosure, an opaque value (a.k.a., "key”) is linked to UE context information which may include mobility data and / or session data, and only the CSP has the means to retrieve the UE / session identity using the key. This means that privacy sensitive data never leaves the CSP domain, and thus, user privacy is secured. Also, the communication used for sending the key to the UE is secured via the control plane ciphering methods. Furthermore, the App backend can receive this key via multiple different secure ways such as using HTTPS, Quic, TLS, and / or VPNs without any specific requirements on the CSP. Lastly, because the key is linked to the UE context information and / or session information via extension of existing procedure, there is no increase in message frequency. If there is a need for an application function (AF) specific external identifier, then the "opaque key” can be used initially, in a similar fashion as the UE IP Address is used in 3GPP Technical Specification (TS) 23.502 chapter 4.15.10, to retrieve the external identifier which then replaces the "opaque key.”

[0035] A network function or network server can be implemented either as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g. on a cloud infrastructure.BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate various embodiments.

[0037] FIG. 1 shows an exemplary scenario where some embodiments of this disclosure can be applied.

[0038] FIG. 2 shows an information element according to some embodiments.

[0039] FIG. 3 shows a process according to some embodiments.

[0040] FIG. 4 shows a process according to some embodiments.

[0041] FIG. 5 shows a process according to some embodiments.

[0042] FIG. 6 shows a process according to some embodiments.

[0043] FIG. 7 shows a process according to some embodiments.

[0044] FIG. 8 shows a process according to some embodiments.

[0045] FIG. 9 shows a process according to some embodiments.

[0046] FIG. 10 shows a process according to some embodiments.

[0047] FIG. 11 shows an apparatus according to some embodiments.

[0048] FIG. 12 shows an apparatus according to some embodiments.DETAILED DESCRIPTION

[0049] FIG. 1 shows an exemplary scenario 100 where some embodiments of this disclosure can be applied. In the scenario 100, an application (“app”) 104 is a video streaming app running on a UE 102 (e.g., a mobile phone, a tablet, a computer, or any other computing device).

[0050] The app 104 is communicatively connected to an app backend / server (hereinafter, just "app server”) 108 via a CSP system 106. In the scenario 100, the app server 108 is a video streaming server. The CSP system 106 is a wireless network system configured to provide a wireless network (e.g., Long-Term Evolution (LTE) network, 5G network, etc.) to the UE 102.

[0051] In the scenario 100, a user of the UE 102 wants to increase the quality of videos streamed to the UE 102. Thus, the UE 102 transmits to the app server 108 a request to increase the video quality (e.g., from 1080p to 4K). In response to receiving such request, the app server 108 requests the CSP system 106 to change its wireless network settings (e.g., increasing the maximum network bandwidth allowed for the UE 102) to accommodate the increased video quality.

[0052] In order to allow the CSP system 106 to change its wireless network settings for the UE 102, the app server 108 needs to inform the CSP system 106 the identity of the UE 102. Otherwise, the CSP system 106 would not know for which UE the CSP system 106 needs to change its wireless network settings. Therefore, the app server 108 needs to know the identity of the UE 102 beforehand.

[0053] One way of providing the identity of the UE 102 to the app server 108 is the CSP system 106 transmitting to the app server 108 subscriber information and / or IP address of the UE 102. However, as explained above, such information may be privacy-sensitive. Furthermore, in some cases, such information may not be even unique for the UE 102 (meaning that multiple UEs may be associated with the same information). Therefore, there is a need for a new identifier for uniquely identifying a specific UE (e.g., the UE 102) and / or a specific network session of the UE 102. Accordingly, in some embodiments of this disclosure, a UE key information element (IE) (a.k.a., "UE unique key IE”) 202 shown in FIG. 2 is provided.

[0054] The 5G system may use the UE key IE 202 (or just the key 204) to support user confidentiality protection when invoking northbound APIs. The UE key IE 202 (or just the key 204) is common to both 3GPP and non-3GPP access upon a successful registration of the UE 102, and may be used for accessing 3GPP access and non-3GPP access security context within the AMF for the UE 102. By using the UE key IE 202 (or just the key 204) in the Camara APIs, an application function (AF) can select the correct UE, device, or a PDU Session without knowing more than the opaque key assigned by the core network.

[0055] The UE key IE 202 may be unique for the UE 102 (meaning that the value(s) of variable(s) included in the UE key IE 202 are uniquely associated the UE 102 but no other UEs) and / or for a specific network session of the UE 102. The UE key IE 202 may be used by the UE 102 (e.g., the app 104 running on the UE 102) and the app server 108 to identify the UE 102 and / or a specific network session of the UE 102.

[0056] As shown in FIG. 2, the UE key IE 202 may comprise i) a key 204 (a.k.a., a UE globally unique temporary identifier (U-GUTI)) for finding, within a CSP domain (i.e., the domain of a CSP system 106 shown in FIGS. 3-6), UE context information associated with the UE 102 and ii) one or more network identifiers (IDs) 206 for identifying a network to which the UE 102 is connected. The key 204 may be any combination of letters and numbers. The key 204 may have the form of an external identifier (i.e., a local identifier (a.k.a., U-GUTI) at a domain identifier (e.g., PLMN ID or obfuscated PLMN ID).

[0057] Examples of the network IDs include a public land mobile network (PLMN) ID and a network ID (NID). The PLMN ID and the NID may collectively identify a standalone non-public network (SNPN). The PLMN ID may comprise a mobile country code (MCC) and a mobile network node (MNC). In some cases, the PLMN ID may be obfuscated (e.g., by creating a HASH of the value). The PLMN ID may be used by ASP or aggregators to find a CSP to be contacted.

[0058] As further shown in FIG. 2, the key 204 is mapped to UE context information 208. The UE context information 208 may be privacy-sensitive and thus may only be used within the CSP domain (meaning that any entity that is outside of the CSP system 106 may not have the access to the UE context information 208) .

[0059] The UE context information may include mobility data of the UE 102. The mobility data of the UE 102 may comprise i) a subscription permanent identifier (SUPI) associated with the UE 102 or an international mobile subscriber identity (I MSI) associated with the UE 102, and / or ii) a generic public subscription identifier (GPSI) associated with the UE 102 or a mobile station international subscriber directory number (MSISDN) associated with the UE 102.

[0060] The UE context information may also include session data of the UE 102. The session data of the UE 102 may comprise any one or more of: an internet protocol (IP) address of the UE 102, a data network name (DNN) identifying a data network associated with the UE 102, and / or a single network slice selection assistance information (S-NSSAI) identifying a network slice associated with the UE 102.

[0061] FIG. 3 shows a process 300 for generating and sharing the UE key IE 202 during a UE registration procedure, according to some embodiments. The process 300 is performed by the UE 102, a radio access network (RAN) 302, UE ID server 304 (optional), an access and mobility management function (AMF) 306, a unified data management (UDM) 308, and a network exposure function (NEF) 312. Note that FIG. 3 does not show all steps and entities involved in the UE registration procedure.

[0062] The process 300 begins with step s302. The step s302 comprises the UE 102 transmitting, to theRAN 302, a registration request for registering the UE 102 with a core network node.

[0063] After receiving the registration request from the UE 102, in step s304, the RAN 302 transmits, to the AMF 306, a registration request for registering the UE 102 with a core network node.

[0064] After receiving the registration request from the RAN 302, in step s306, the AMF 306 may generate a key (e.g., the key 204). As explained above, this key may be used for finding, within the CSP domain, UE context information associated with the UE 102. There are different ways of generating the key 204. In one example, the AMF 306 may use a sequence of randomly generated characters as the key 204.

[0065] The key 204 may also be called as a pointer because it points to the UE context information associated with the UE 102. Thus, in some embodiments, the step s306 may also comprise mapping the key to the UE context information which is to be updated later. The key 204 may also be called as an opaque UE unique key because it identifies the UE 102 without revealing the UE context information. The table provided below illustrates the concept of the mapping between the key and the UE context information stored in the AMF 306.

[0066] Note that the UE context information that is mapped to the key that is generated in step s306 may be initially empty or may initially set to have a predefined value at this stage. The UE context information is to be updated by the AMF 306 later.

[0067] After generating the key 204, in step s308, the AMF 306 may transmit, to the UDM 308, a request for registering the AMF 306 at the UDM 308. The request may include the key 204. One example of this request is the Nudm_UECM_Registration message defined in the 3GPP standard. One exemplary message definition of the request is provided below.

[0068] After receiving the AMF registration request from the AMF 306, in step s310, the UDM 308 may map the key 204 to the AMF 306, and store mapping information identifying the mapping of the key 204 to the AMF 306. This mapping information may be used by the UDM 308 later when it needs to find a particular AMF (and / or MME in 4G) mapped to the key 204. The table provided below illustrates the concept of the mapping information stored in the UDM 308

[0069] In step s312, the UDM 308 may transmit, to the AMF 306, a message including the mobility data of the UE 102 (e.g., SUPI / IMSI and / or GPSI / MSISDN).

[0070] After obtaining the mobility data of the UE 102, in step s314, the AMF 306 may update the UE context information to include the UE 102's mobility data. Also, in the step s318, the AMF 306 may pair the key 204 with one or more network IDs (e.g., PLMN ID and / or NID which in combination may identify a stand-alone non-public network (SNPN)) identifying the network to which the UE 102 is connected. More specifically, in some embodiments, the AMF 306 may generate the UE key IE 202 shown in FIG. 2, which comprises the key 204 and the network ID(s) 206.

[0071] Note that, as explained above, in the step s314, the UE context information is updated to include the UE 102's mobility data. However, as shown in FIG. 2, the UE context information may also include the session data such as the IP address of the UE 102, the DNN associated with the UE 102, and / or the S-NSSAI associated with the UE 102. In order for the AMF 306 to obtain the session data of the UE 102 (e.g., at least the IP address of the UE 102), in step s316, the AMF 306 may subscribe to MONTE Event. Then once the NEF 312 obtains the UE 102's session data, the NEF 312 may transmit, to the AMF 306, the UE 102's session data.

[0072] Then, in step s318, the AMF 306 may transmit to, the RAN 302, a registration accept message for accepting the registration request transmitted in the step s304, and in step s320, the RAN 302 may transmit, to the UE 102, a registration accept message for accepting the registration request transmitted in the step s302. Each of the registration accept messages that the AMF 306 and the RAN 302 transmit may include the UE key IE 202.

[0073] An exemplary message definition of the registration accept message that the AMF 306 transmits to the RAN 302 and that the RAN 302 transmits to the UE 102 is provided below.

[0074] In the above described embodiments, the key 204 is stored in the AMF 306. However, in some embodiments, the key 204 may be stored in a different entity such as the UE ID server 304. In such embodiments, after the AMF 306 performs the step s314, in the step s322, the AMF 306 may transmit, the UE ID server 304, the UE key IE 202 (or just the key 204) and the UE context information associated with the UE 102. In these embodiments, in order for the UE ID server 304to obtain the session data of the UE 102, in step s324, the UE ID server 304 may subscribe to MONTE Event. Then once the NEF 312 obtains the UE 102's session data, the NEF 312 may transmit the UE 102's session data to the UE ID server 304 either directly or via one or more intermediate network entities.

[0075] FIG. 4 shows a process 400 for updating the UE context information associated with the UE 102 during a packet data unit (PDU) session establishment procedure, according to some embodiments. The process 400 may begin with step s402.

[0076] The step s402 comprises the UE 102 transmitting, to the AMF 306, a PDU session establishment request for establishing a PDU session. In some embodiments, the PDU session establishment request may include some session data of the UE 102 such as the DNN associated with the UE 102 and / or the S-NSSAI associated with the UE 102. In these embodiments, the AMF 306 may only need to obtain the IP address of the UE 102 from theNEF 312 in step s408 which is described below.

[0077] After the AMF 306 receives the PDU session establishment request in the step s402, step s404 may be performed. The step s404 may comprise a plurality of sub-processes related to establishing a PDU session. For example, the step s404 may comprise the AMF 306 and a network repository function (NRF) discovering and selecting a session management function (SMF), exchanging Nsmf_PDUSession_CreateSMContext request and response between the AMF 306 and the SMF, exchanging Nudm_SDM_Get messages between the SMF and the UDM 308, the NRF and the SMF discovering and selecting a user plane function (UPF), exchanging session_establishment messages between the SMF and the UPF, and the SMF transmitting to the AMF 306 Namf_Communication_N1 N2MessageTransfer message. After performing the step s404, step s406 may be performed.

[0078] The step s406 comprises SMF 402 transmitting, to NEF 312, a message (e.g., a PDU session event exposure message) including the IP address of the UE 102. Then, in step s408, the NEF 312 transmits, to the AMF 306, a message (e.g., a PDU session status event subscription result message) including the IP address of the UE 102. Note that the transmission of the message from the NEF 312 to the AMF 306 is resulted from the AMF 306 subscribing to MONTE event in the step s316 shown in FIG. 3.

[0079] As discussed above, in some embodiments, the AMF 306 may already have some session data such as the DNN associated with the UE 102, and / or the S-NSSAI associated with the UE 102. In such embodiments, the message transmitted from the NEF 312 to the AMF 306 may only include the IP address of the UE 102 but does not include the DNN and / or the S-NSSAI associated with the UE 102. However, in other embodiments, the AMF 306 may not have any session data of the UE 102. In such embodiments, the message transmitted from the NEF 312 to the AMF 306 may include the IP address of the UE 102 as well as the DNN and / or the S-NSSAI associated with the UE 102.

[0080] After receiving the message in the step s408, in step s409, the AMF 306 may update the UE context information associated with the UE 102 to include the session data of the UE 102. Note that when the key 204 pointing to the UE context information is initially generated in the step s306, the UE context information was empty or was set to include a predefined value. Then, in the step s314, the UE context information was updated to include the UE's mobility data (e.g., SUPI, IMSI, GPIS, and / or MSISDN). In the step s409, the UE context information is further updated to include the UE 102's session data (e.g., the IP address of the UE 102, the DNN associated with the UE 102, and / or the S-NSSAI associated with the UE 102).

[0081] Note that, as discussed above, in some embodiments, instead of the AMF 306, the UE ID server 304 may store the key 204 pointing to the UE context information. In such embodiments, steps s410-414 may be performed.

[0082] The step s410 comprises the AMF 306 updating the UE context information associated with the UE102 to include the UE 102's session data it obtained previously. More specifically, in one example, the AMF 306 may update the UE context information to include the DNN associated with the UE 102 and / or the S-NSSAI associated with the UE 102.

[0083] Then, in step s412, the AMF 306 may transmit, to the UE ID server 304, the UE IE 202 (or just the key 204) with the updated UE context information. Then, in step s414, the NEF 312 transmits, to the UE ID server 304, a message (e.g., a PDU session status event subscription result message) including the IP address of the UE 102. Note that the transmission of the message from the NEF 312 to the UE ID server 304 is resulted from the UE ID server 304 subscribing to MONTE event in the step s324 shown in FIG. 3.

[0084] FIG. 3 shows the process of generating and sharing the key 204 before the UE 102 is registered to the core network and FIG. 4 shows the process of updating the UE context information associated with the UE 102 as the PDU session is established. However, there may be a scenario where the key 204 needs to be generated after the UE 102 is registered to the core network and after at least one PDU session is established for the UE 102. Accordingly, in some embodiments, a process 500 shown in FIG. 5 is used to generate and share the key 204.

[0085] The process 500 may be performed after the UE 102 is registered, authenticated, and authorized and after at least one PDU session is established for the UE 102. The process 500 may begin with step s502.

[0086] The step s502 comprises the user of the UE 102 starting the app 104 on the UE 102. After the app 104 is started, the app 104 may transmit, to the operating system of the UE 102, a request for a key for finding, within the CSP domain, UE context information associated with the UE 102. Then, in step s504, the UE 102 may transmit, to the AMF 306, a request for the key.

[0087] After receiving, from the UE 102, the request for the key, in step s506, the AMF 306 may generate a key (e.g., the key 204) for finding, within the CSP domain, the UE context information associated with the UE 102. The step s506 may also comprise mapping the key 204 to the UE context information (which may be blank or may set to have a predefined value such as 0) associated with the UE 102. In some embodiments, such mapping may be stored in the AMF 306. The UE context information is to be updated later.

[0088] In some embodiments, in the step s506, the AMF 306 may pair the key 204 with one or more network IDs (e.g., PLMN ID and / or NID) identifying the network to which the UE 102 is connected (since a PDU session is already established for the UE 102). More specifically, in some embodiments, the AMF 306 may generate the UE key IE 202 shown in FIG. 2, which comprises the key 204 and the network ID(s) 206. Alternatively, the pairing of the key 204 with one or more network ID(s) may be performed in step s514 described below.

[0089] After generating the key 204, in step s508, the AMF 306 may transmit to, the UDM 308, a request for registering the AMF 306 at the UDM 308. The request may include the key 204. One example of this request is the Nudm_UECM_Registration message defined in the 3GPP standard. One exemplary message definition of the request is provided above.

[0090] After receiving the AMF registration request from the AMF 306, in step s510, the UDM 308 may register the AMF 306, and may store mapping information mapping the AMF 306 to the key 204. This mapping information may be used later by the UDM 308 to find the correct AMF (or the MME in case of LTE) corresponding to the key 204 when an API is invoked by the app server 108 later (which is described below).

[0091] After generating the key 204, in step s512, the AMF 306 may transmit to, SMF 402, a request for the IP address associated with the PDU session for the UE 102, and in response to the request, the SMF 402 may transmit, to the AMF 306, a response including the IP address associated with the UE 102.

[0092] After receiving the IP address associated with the UE 102, in step s514, the AMF 306 may update the UE context information mapped to the key 204 to include the IP address associated with the UE 102. Note that, as explained above, in some embodiments, the AMF 306 may already have the UE 102's other session data such as the DNN associated with the UE 102 and / or the S-NSSAI associated with the UE 102. In such embodiments, in the step s514, the AMF 306 may update the UE context information to include the IP address of the UE 102 as well as the DNN associated with the UE 102 and / or the S-NSSAI associated with the UE 102.

[0093] In some embodiments, in the step s514, the AMF 306 may pair the key 204 with one or more network IDs (e.g., PLMN ID and / or NID) identifying the network to which the UE 102 is connected (since a PDU session is already established for the UE 102). More specifically, in some embodiments, the AMF 306 may generate the UE key IE 202 shown in FIG. 2, which comprises the key 204 and the network ID(s) 206.

[0094] Then, in step s516, the AMF 306 may transmit, to the UE 102, a response to the request for the key. The response includes the key 204 pointing to the UE context information associated with the UE 102.

[0095] Now let's assume that the user of the UE 102 wants to change a configuration of a service provided by the app 104 running on the UE 102. For example, in case the app 104 is a video streaming service, the user of the UE 102 may want to increase the quality of a video streamed to the UE 102 from 1080p to 4K. In such case, the app 104 may transmit a request for a configuration change to the app server 108 via the operating system of the UE 102. Thus, in step s602 shown in FIG. 6, the UE 102 may transmit, to the app server 108, a request for a configuration change. The request includes the UE key IE 202. Note that even though the request for a configuration change is used as an example here, in the step s602, the UE 102 may instead transmit, to the app server 108, any message that may cause the app server 108 to trigger a change with respect to a network session of the UE 102.

[0096] In response to receiving the request from the UE 102, in step s604, the app server 108 may decide to trigger an action (e.g., increasing the quality of service (QoS) or monitor any specific events) for the app 104 running on the UE 102. Then, in step s606, the app server 108 may transmit, to API Gateway (GW) 502, a request to trigger the action (e.g., invoking Camera's Quality on Demand (QOD) API). The request includes the UE key IE 202 (or just the key 204).

[0097] In order for the API GW 502 to trigger the action for the UE 102, the API GW 502 needs to convertthe the key 204 to the UE 102's mobility data and / or the UE 102's session data such that the action can be applied to the UE 102 and / or a specific network session of the UE 102. For example, in order to perform a monitoring event related to a network session of the UE 102, the API GW 502 may need MSISDN associated with the UE 102. In another example, in order to use Camera's QoD API, the API GW 502 may need the IP address of the UE 102.

[0098] Thus, in step s608, the API GW 502 may transmit, to a common function (CF) 504, a conversion request for converting the key 204 to the UE 102's mobility data and / or the UE 102's session data.

[0099] After receiving the conversion request from the API GW502, in step s610, the CF 504 may transmit, to the UDM 308, a find request including the key 204. The find request is for finding the AMF associated with the key 204, and in response to receiving the find request, the UDM 308 may transmit, to the CF 504, a response including an AMF identifier identifying the AMF 306.

[0100] Then, in step s612, the CF 504 may transmit, to the AMF 306, a request for the UE context information associated with the UE 102, and, in response to receiving the request which includes the key 204, the AMF 306 finds the UE context information mapped to the key 204, and transmits, to the CF 504, the UE context information associated with the UE 102.

[0101] In some embodiments, instead of the AMF 306, the UE ID server 304 may store the key 204 pointing to the UE context information associated with the UE 102. In such embodiments, instead of performing the steps s610 and s612, step s618 may be performed. The step s618 comprises, the CF 504, a request for the UE context information associated with the UE 102, and, in response to receiving the request which includes the key 204, the UE ID server 304 finds the UE context information mapped to the key 204, and transmits, to the CF 504, the UE context information associated with the UE 102.

[0102] Then, in step s614, the CF 504 may transmit, to the API GW502, a response to the conversion request, which includes the UE context information associated with the UE 102. Here, the UE context information included in the response may include the UE 102's IP address, the MSISDN, and / or the IMSI. After receiving the response to the conversion request, in step s616, the API GW502 may transmit, to the NEF 312, a message triggering the change with respect to the network session of the UE 102. In one example, the message may be a request that the UE 102 is set up with a specific QoS and priority handling.

[0103] The following text summarizes the UE identity retrieval procedure according to some embodiments.

[0104] FIG. 7 shows a process 700 performed by the UE 102 according to some embodiments. The process 700 may begin with step s702. The step s702 comprises transmitting a first message to a first network node (e.g., 306). The step s704 comprises, after transmitting the first message, receiving from the first network node (e.g., 306) a second message which includes a UE key information element, IE. The UE key IE comprises I)a key for finding, within a communication service provider, CSP, domain, UE context information associated with the UE and ii) one or more network identifiers, IDs, identifying a network to which the UE is connected.

[0105] In some embodiments, the UE context information includes mobility data of the UE, and the mobility data of the UE comprises: i) a subscription permanent identifier, SUPI, associated with the UE or an international mobile subscriber identity, IMSI, associated with the UE, and / or ii) a generic public subscription identifier, GPSI , associated with the UE or a mobile station international subscriber directory number, MSISDN, associated with the UE.

[0106] In some embodiments, said one or more network IDs comprises I) a public land mobile network, PLMN, ID which comprises a mobile country code, MCC, and a mobile network node, MNC and / or ii) a network ID, NID.

[0107] In some embodiments, the first message is a registration request for initiating a process of registering the UE with a core network; and the second message is a registration accept message for accepting the registration request.

[0108] In some embodiments, after the UE receiving the second message, the UE context information is modified to include one or more of: an internet protocol, IP, address of the UE; a data network name, DNN, identifying a data network associated with the UE; and / or a single network slice selection assistance information, S-NSSAI, identifying a network slice associated with the UE.

[0109] In some embodiments, the process 700 further comprises transmitting a session establishment request for establishing a network session; and after transmitting the session establishment request, receiving a session establishment accept message for accepting the session establishment request, wherein the UE context information is modified to include one or more of the IP address of the UE, the DN N, and / or the S-NSSAI after the UE transmitting the session establishment request but before the UE receiving the session establishment accept message.

[0110] In some embodiments, the first network node is an access and mobility management function, AMF.[OHl] In some embodiments, the process 700 further comprises executing an application on the UE; the application sending to an operating system of the UE a request for the UE key IE; as a result of sending the request for the UE key IE, the application receiving the requested UE key IE from the operating system of the UE; and the application triggering the UE to transmit a message including the UE key IE to an application server which is configured to control the application.

[0112] FIG. 8 shows a process 800 performed by a first network node (e.g., 306) according to some embodiments. The process 800 may begin with step s802. The step s802 comprises obtaining a key. The step s804 comprises after obtaining the key, storing mapping information which maps the key to user equipment, UE, context information associated with a specific UE (e.g., 102). The step s806 comprises generating a UE keyinformation element, IE, which comprises the obtained key and one or more network identifiers, IDs, identifying a network to which the specific UE is connected. The step s808 comprises transmitting to the specific UE a first message including the UE key IE.

[0113] In some embodiments, the process 800 further comprises receiving from the specific UE a registration request for initiating a process of registering the specific UE with a core network, wherein the first message including the UE key IE is a registration accept message for accepting the registration request.

[0114] In some embodiments, the process 800 further comprises transmitting to a second network node a second message comprising the key; and after transmitting the second message to the second network node, receiving a third message from the second network node, wherein based at least on transmitting the second message to the second network node, the key is mapped to the first network node.

[0115] In some embodiments, the second network node is a unified data management, UDM, function, the second message is a request for registering the first network node at the UDM function, and the third message is a response to the request for registering the first network node at the UDM function.

[0116] In some embodiments, the first network node is an access and mobility management function, AMF.

[0117] In some embodiments, the UE context information mapped to the key includes mobility data of the specific UE, and the mobility data of the specific UE comprises: I) a subscription permanent identifier, SUPI, associated with the specific UE or an international mobile subscriber identity, IMSI, associated with the specific UE, and / or ii) a generic public subscription identifier, GPSI , associated with the specific UE or a mobile station international subscriber directory number, MSISDN, associated with the specific UE.

[0118] In some embodiments, said one or more network IDs comprises i) a public land mobile network, PLMN, ID which comprises a mobile country code, MCC, and a mobile network node, MNC and / or ii) a network ID, NID.

[0119] In some embodiments, the process 800 further comprises obtaining additional information related to the specific UE, wherein the additional information related to the specific UE includes one or more of: an internet protocol, IP, address of the specific UE; a data network name, DNN, identifying a data network associated with the specific UE; and / or a single network slice selection assistance information, S-NSSAI, identifying a network slice associated with the specific UE; and after obtaining the additional information, modifying the UE context information to include the additional information.

[0120] In some embodiments, the process 800 further comprises receiving from the specific UE a session establishment request for establishing a network session, wherein the additional information is obtained after receiving the session establishment request.

[0121] In some embodiments, the process 800 further comprises receiving from an entity controlled by a communication service provider, CSP, a retrieval request to retrieve the UE context information, wherein the retrievalrequest includes the UE key IE comprising the key and said one or more network IDs, and based at least on receiving the retrieval request, transmitting to the entity in the CSP a response to the retrieval request, wherein the response to the retrieval request includes the UE context information.

[0122] FIG. 9 shows a process 900 performed by a first network node (e.g., 308) according to some embodiments. The process 900 may begin with step s902. The step s902 comprises receiving from a second network node (e.g., 306) a first message including a key. The step s904 comprises determining that the second network node (e.g., 306) transmitted the key. The step s906 comprises, after obtaining the key and determining that the second network node (e.g., 306) transmitted the key, storing mapping information which maps the key to the second network node (e.g., 306).

[0123] In some embodiments, the first network node is a unified data management, UDM, function, the first message is a request for registering the second network node at the UDM function, and the second message is a response to the request for registering the second network node at the UDM function.

[0124] In some embodiments, the second network node is an access and mobility management function, AMF.

[0125] In some embodiments, the process 900 further comprises receiving from an entity controlled by a communication service provider, CSP, a find request including a user equipment, UE, key information element, IE, wherein the UE key IE comprises the key and one or more network identifiers, IDs, identifying a network to which a specific UE is connected, the key is for finding, within a communication service provider, CSP, domain, UE context information associated with the specific UE, and the find request is for finding a network node handling a specific network session of the specific UE; based at least on receiving the find request, finding the network node handling the specific network session of the specific UE; and transmitting to the entity in the CSP a response to the find request, wherein the response to the find request includes a network node identifier identifying the network node handling the specific network session of the specific UE.

[0126] In some embodiments, the UE context information includes mobility data of the specific UE, and the mobility data of the specific UE comprises: i) a subscription permanent identifier, SUPI, associated with the specific UE or an international mobile subscriber identity, IMSI, associated with the specific UE, and / or ii) a generic public subscription identifier, GPSI , associated with the specific UE or a mobile station international subscriber directory number, MSISDN, associated with the specific UE.

[0127] In some embodiments, the UE context information further includes one or more of: an internet protocol, IP, address of the specific UE; a data network name, DNN, identifying a data network associated with the specific UE; and / or a single network slice selection assistance information, S-NSSAI, identifying a network slice associated with the specific UE.

[0128] FIG. 10 shows a process 1000 performed by a system (e.g., 100) according to some embodiments.The process 1000 may begin with step s1002. The step s1002 comprises a first network node (e.g., 504) transmitting to a second network node (e.g., 308) a find request for finding a third network node (e.g., 306) which handles a specific network session of a specific user equipment, U E, wherein the find request includes a key for finding, within a communication service provider, CSP, domain, UE context information associated with the specific UE. The step s1004 comprises, after receiving the find request, using the key, the second network node (e.g., 308) finding the third network node (e.g., 306) handling the specific network session of the specific UE. The step s1006 comprises, after finding the third network node (e.g., 306), the second network node (e.g., 308) transmitting to the first network node (e.g., 504) a response to the find request, wherein the response to the find request includes a network node identifier identifying the third network node (e.g., 306).

[0129] The process 1000 further comprises after receiving the response to the find request, the first network node transmitting to the third network node a retrieval request for retrieving the UE context information associated with the specific UE, wherein the retrieval request includes the key; after receiving the retrieval request, using the key, the third network node retrieving the UE context information associated with the specific UE; and the third network node transmitting to the first network node a response to the retrieval request, wherein the response to the retrieval request includes the UE context information associated with the specific UE.

[0130] In some embodiments, the UE context information includes mobility data of the specific UE, and the mobility data of the specific UE comprises: i) a subscription permanent identifier, SUPI, associated with the specific UE or an international mobile subscriber identity, IMSI, associated with the specific UE, and / or ii) a generic public subscription identifier, GPSI , associated with the specific UE or a mobile station international subscriber directory number, MSISDN, associated with the specific UE.

[0131] In some embodiments, the UE context information further includes one or more of: an internet protocol, IP, address of the specific UE; a data network name, DNN, identifying a data network associated with the specific UE; and / or a single network slice selection assistance information, S-NSSAI, identifying a network slice associated with the specific UE.

[0132] In some embodiments, the process 1000 further comprises an application running on the specific UE triggering transmission of an application related message to an application server controlling the application, wherein the application related message includes the key; based at least on receiving the application related message, the application server transmitting to a fourth network node a first request for the UE context information, wherein the first request for the UE context information comprises the key; and based at least on receiving the first request for the UE context information, the fourth network node transmitting to the first network node a second request for the UE context information, wherein the second request for the UE context information comprises the key, wherein the first network node transmitted the find request to the second network node based at least on receiving from the fourth network node the second request for the UE context information.

[0133] In some embodiments, the process 1000 further comprises the fist network node transmitting to the fourth network node a message including the UE context information; the fourth network node transmitting to a fifth network node an application programming interface, API, call message for an API call, wherein the API call message includes the UE context information; using the UE context information, the fifth network node identifying the specific UE and / or the specific network session of the specific UE; and the fifth network node performing an API function for the application, which is targeted for the specific UE and / or the specific network session of the specific UE.

[0134] FIG. 11 is a block diagram of the UE 102, according to some embodiments. As shown in FIG. 11 , the UE 102 may comprise: processing circuitry (PC) 1102, which comprises one or more processors (P) 1155 (e.g., one or more general purpose microprocessors and / or one or more other processors, such as an application specific integrated circuit (ASIC), field-programmable gate arrays (FPGAs), and the like); communication circuitry 1148, which is coupled to an antenna arrangement 1149 comprising one or more antennas and which comprises a transmitter (Tx) 1145 and a receiver (Rx) 1147 for enabling UE 102 to transmit data and receive data (e.g., wirelessly transmit / receive data); and a storage unit (a.k.a., "data storage system”) 1108, which may include one or more nonvolatile storage devices and / or one or more volatile storage devices. In embodiments where PC 1102 includes a programmable processor, a computer readable storage medium (CRSM) 1142 may be provided. CRSM 1142 may store a computer program (CP) 1143 comprising computer readable instructions (CRI) 1144. CRSM 1142 may be a non-transitory computer readable medium, such as, magnetic media (e.g., a hard disk), optical media, memory devices (e.g., random access memory, flash memory), and the like. In some embodiments, the CRI 1144 of computer program 1143 is configured such that when executed by PC 1102, the CRI causes UE 102 to perform steps described herein (e.g., steps described herein with reference to the flow charts). In other embodiments, UE 102 may be configured to perform steps described herein without the need for code. That is, for example, PC 1102 may consist merely of one or more ASICs. Hence, the features of the embodiments described herein may be implemented in hardware and / or software.

[0135] FIG. 12 is a block diagram of network node 1200 for implementing any one or more of entities (e.g., 304, 306, 308, 312, 402, 502, 504, etc.) shown in FIGS. 3-6, according to some embodiments. As shown in FIG. 12, the network node 1200 may comprise: processing circuitry (PC) 1202, which comprises one or more processors (P) 1255 (e.g., one or more general purpose microprocessors and / or one or more other processors, such as an application specific integrated circuit (ASIC), field-programmable gate arrays (FPGAs), and the like), which processors may be co-located in a single housing or in a single data center or may be geographically distributed (e.g., network node 1200 may be a distributed computing apparatus comprising two or more computers or a monolithic computing apparatus consisting of a single computer); at least one network interface 1248 (e.g., a physical interface or air interface) comprising a transmitter (Tx) 1245 and a receiver (Rx) 1247 for enabling network node 1200 to transmit data to and receive data from other nodes connected to network 110 (e.g., an Internet Protocol (IP) network) to which network interface 1248 is connected (physically or wirelessly) (e.g., network interface 1248may be coupled to an antenna arrangement comprising one or more antennas for enabling network node 1200 to wirelessly transmit / receive data); and a storage unit (a.k.a., "data storage system”) 1208, which may include one or more non-volatile storage devices and / or one or more volatile storage devices. In embodiments where PC 1202 includes a programmable processor, a computer readable storage medium (CRSM) 1242 may be provided. CRSM 1242 may store a computer program (CP) 1243 comprising computer readable instructions (CRI) 1244. CRSM 1242 may be a non-transitory computer readable medium, such as, magnetic media (e.g., a hard disk), optical media, memory devices (e.g., random access memory, flash memory), and the like. In some embodiments, the CRI 1244 of computer program 1243 is configured such that when executed by PC 1202, the CRI causes network node 1200 to perform steps described herein (e.g., steps described herein with reference to the flow charts). In other embodiments, network node 1200 may be configured to perform steps described herein without the need for code. That is, for example, PC 1202 may consist merely of one or more ASICs. Hence, the features of the embodiments described herein may be implemented in hardware and / or software.

[0136] While various embodiments are described herein, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of this disclosure should not be limited by any of the above-described exemplary embodiments. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the disclosure unless otherwise indicated herein or otherwise clearly contradicted by context.

[0137] As used herein transmitting a message "to” or "toward” an intended recipient encompasses transmitting the message directly to the intended recipient or transmitting the message indirectly to the intended recipient (i.e., one or more other nodes are used to relay the message from the source node to the intended recipient). Likewise, as used herein receiving a message "from” a sender encompasses receiving the message directly from the sender or indirectly from the sender (i.e., one or more nodes are used to relay the message from the sender to the receiving node). Further, as used herein "a” means "at least one” or "one or more.”

[0138] Additionally, while the processes described above and illustrated in the drawings are shown as a sequence of steps, this was done solely for the sake of illustration. Accordingly, it is contemplated that some steps may be added, some steps may be omitted, the order of the steps may be re-arranged, and some steps may be performed in parallel.

Claims

CLAIMS1. A method (700) performed by a user equipment, UE (102), the method comprising: transmitting (s702) a first message to a first network node (306); and after transmitting the first message, receiving (s704) from the first network node (306) a second message which includes a UE key information element, IE, wherein the UE key IE comprises i) a key for finding, within a communication service provider, CSP, domain, UE context information associated with the UE and ii) one or more network identifiers, IDs, identifying a network to which the UE is connected.

2. The method of claim 1, wherein the UE context information includes mobility data of the UE, and the mobility data of the UE comprises: i) a subscription permanent identifier, SUPI, associated with the UE or an international mobile subscriber identity, I MSI, associated with the UE, and / or ii) a generic public subscription identifier, GPSI , associated with the UE or a mobile station international subscriber directory number, MSISDN, associated with the UE.

3. The method of any one of claims 1-2, wherein said one or more network IDs comprises i) a public land mobile network, PLMN, ID which comprises a mobile country code, MCC, and a mobile network node, MNC and / or ii) a network ID, NID.

4. The method of any one of claims 1-3, wherein the first message is a registration request for initiating a process of registering the UE with a core network; and the second message is a registration accept message for accepting the registration request.

5. The method of any one of claims 1-4, wherein after the UE receiving the second message, the UE context information is modified to include one or more of: an internet protocol, IP, address of the UE; a data network name, DNN, identifying a data network associated with the UE; and / or a single network slice selection assistance information, S-NSSAI, identifying a network slice associated with the UE.

6. The method of claim 5, the method further comprising: transmitting a session establishment request for establishing a network session; and after transmitting the session establishment request, receiving a session establishment accept message for accepting the session establishment request, wherein the UE context information is modified to include one or more of the IP address of the UE, the DNN, and / or the S-NSSAI after the UE transmitting the session establishment request but before the UE receiving the session establishment accept message.

7. The method of any one of claims 1-6, wherein the first network node is an access and mobility management function, AMF.

8. The method of any one of claims 1-7, the method further comprising: executing an application on the UE; the application sending to an operating system of the UE a request for the UE key IE; as a result of sending the request for the UE key IE, the application receiving the requested UE key IE from the operating system of the UE; and the application triggering the UE to transmit a message including the UE key IE to an application server which is configured to control the application.

9. A method (800) performed by a first network node (306), the method comprising: obtaining (s802) a key; after obtaining the key, storing (s804) mapping information which maps the key to user equipment, UE, context information associated with a specific UE (102); generating (s806) a UE key information element, IE, which comprises the obtained key and one or more network identifiers, IDs, identifying a network to which the specific UE is connected; and transmitting (s808) to the specific UE (102) a first message including the UE key IE.

10. The method of claim 9, the method further comprising: receiving from the specific UE a registration request for initiating a process of registering the specific UE with a core network, wherein the first message including the UE key IE is a registration accept message for accepting the registration request.

11. The method of claim 9 or 10, the method further comprising:transmitting to a second network node a second message comprising the key; and after transmitting the second message to the second network node, receiving a third message from the second network node, wherein based at least on transmitting the second message to the second network node, the key is mapped to the first network node.

12. The method of claim 11 , wherein the second network node is a unified data management, UDM, function, the second message is a request for registering the first network node at the UDM function, and the third message is a response to the request for registering the first network node at the UDM function.

13. The method of any one of claims 9-12, wherein the first network node is an access and mobility management function, AMF.

14. The method of any one of claims 9-13, wherein the UE context information mapped to the key includes mobility data of the specific UE, and the mobility data of the specific UE comprises: i) a subscription permanent identifier, SUPI, associated with the specific UE or an international mobile subscriber identity, IMSI, associated with the specific UE, and / or ii) a generic public subscription identifier, GPSI , associated with the specific UE or a mobile station international subscriber directory number, MSISDN, associated with the specific UE.

15. The method of any one of claims 9-14, wherein said one or more network IDs comprises i) a public land mobile network, PLMN, ID which comprises a mobile country code, MCC, and a mobile network node, MNC and / or ii) a network ID, NID.

16. The method of any one of claims 9-15, the method comprising: obtaining additional information related to the specific UE, wherein the additional information related to the specific UE includes one or more of: an internet protocol, IP, address of the specific UE; a data network name, DNN, identifying a data network associated with the specific UE; and / or a single network slice selection assistance information, S-NSSAI, identifying a network slice associated with the specific UE; andafter obtaining the additional information, modifying the UE context information to include the additional information.

17. The method of claim 16, the method comprising: receiving from the specific UE a session establishment request for establishing a network session, wherein the additional information is obtained after receiving the session establishment request.

18. The method of any one of claims 9-17, the method further comprising: receiving from an entity controlled by a communication service provider, CSP, a retrieval request to retrieve the UE context information, wherein the retrieval request includes the UE key IE comprising the key and said one or more network IDs, and based at least on receiving the retrieval request, transmitting to the entity in the CSP a response to the retrieval request, wherein the response to the retrieval request includes the UE context information.

19. A method (900) performed by a first network node (308), the method comprising: receiving (s902) from a second network node (306) a first message including a key; determining (s904) that the second network node (306) transmitted the key; and after obtaining the key and determining that the second network node (306) transmitted the key, storing (s906) mapping information which maps the key to the second network node (306).

20. The method of claim 19, wherein the first network node is a unified data management, UDM, function, the first message is a request for registering the second network node at the UDM function, and the second message is a response to the request for registering the second network node at the UDM function.21 . The method of claim 19 or 20, wherein the second network node is an access and mobility management function, AMF.

22. The method of any one of claims 19-21, the method further comprising: receiving from an entity controlled by a communication service provider, CSP, a find request including a user equipment, UE, key information element, IE, wherein the UE key IE comprises the key and one or more network identifiers, IDs, identifying a network to which a specific UE is connected,the key is for finding, within a communication service provider, CSP, domain, UE context information associated with the specific UE, and the find request is for finding a network node handling a specific network session of the specific UE; based at least on receiving the find request, finding the network node handling the specific network session of the specific UE; and transmitting to the entity in the CSP a response to the find request, wherein the response to the find request includes a network node identifier identifying the network node handling the specific network session of the specific UE.

23. The method of claim 22, wherein the UE context information includes mobility data of the specific UE, and the mobility data of the specific UE comprises: i) a subscription permanent identifier, SUPI, associated with the specific UE or an international mobile subscriber identity, IMSI, associated with the specific UE, and / or ii) a generic public subscription identifier, GPSI , associated with the specific UE or a mobile station international subscriber directory number, MSISDN, associated with the specific UE.

24. The method of claim 22 or 23, wherein the UE context information further includes one or more of: an internet protocol, IP, address of the specific UE; a data network name, DNN, identifying a data network associated with the specific UE; and / or a single network slice selection assistance information, S-NSSAI, identifying a network slice associated with the specific UE.

25. A method (1000) performed by a system (100), the method comprising: a first network node (504) transmitting (s1002) to a second network node (308) a find request for finding a third network node (306) which handles a specific network session of a specific user equipment, UE, wherein the find request includes a key for finding, within a communication service provider, CSP, domain, UE context information associated with the specific UE; after receiving the find request, using the key, the second network node (308) finding (s1004) the third network node (306) handling the specific network session of the specific UE; and after finding the third network node (306), the second network node (308) transmitting (s1006) to the first network node (504) a response to the find request, wherein the response to the find request includes a network node identifier identifying the third network node (306).

26. The method of claim 25, the method further comprising: after receiving the response to the find request, the first network node transmitting to the third network node a retrieval request for retrieving the UE context information associated with the specific U E, wherein the retrieval request includes the key; after receiving the retrieval request, using the key, the third network node retrieving the UE context information associated with the specific UE; and the third network node transmitting to the first network node a response to the retrieval request, wherein the response to the retrieval request includes the UE context information associated with the specific UE.

27. The method of claim 25 or 26, wherein the UE context information includes mobility data of the specific UE, and the mobility data of the specific UE comprises:I) a subscription permanent identifier, SUPI, associated with the specific UE or an international mobile subscriber identity, IMSI, associated with the specific UE, and / or ii) a generic public subscription identifier, GPSI , associated with the specific UE or a mobile station international subscriber directory number, MSISDN, associated with the specific UE.

28. The method of claim 27, wherein the UE context information further includes one or more of: an internet protocol, IP, address of the specific UE; a data network name, DNN, identifying a data network associated with the specific UE; and / or a single network slice selection assistance information, S-NSSAI, identifying a network slice associated with the specific UE.

29. The method of any one of claims 25-28, further comprising: an application running on the specific UE triggering transmission of an application related message to an application server controlling the application, wherein the application related message includes the key; based at least on receiving the application related message, the application server transmitting to a fourth network node a first request for the UE context information, wherein the first request for the UE context information comprises the key; and based at least on receiving the first request for the UE context information, the fourth network node transmitting to the first network node a second request for the UE context information, wherein the second request for the UE context information comprises the key, wherein the first network node transmitted the find request to the second network node based at least on receiving from the fourth network node the second request for the UE context information.

30. The method of claim 29 when claim 29 depends on claim 26, the method further comprising: the fist network node transmitting to the fourth network node a message including the UE context information; the fourth network node transmitting to a fifth network node an application programming interface, API, call message for an API call, wherein the API call message includes the UE context information; using the UE context information, the fifth network node identifying the specific UE and / or the specific network session of the specific UE; and the fifth network node performing an API function for the application, which is targeted for the specific UE and / or the specific network session of the specific UE.31 . A computer program (1100 or 1200) comprising instructions (1144 or 1244) which when executed by processing circuitry (1102 or 1202) cause the processing circuitry to perform the method of any one of claims 1-30.

32. A carrier containing the computer program of claim 31, wherein the carrier is one of an electronic signal, an optical signal, a radio signal, and a computer readable storage medium.

33. A user equipment, UE (102), being configured to: transmit (s702) a first message to a first network node (306); and after transmitting the first message, receive (s704) from the first network node (306) a second message which includes a UE key information element, IE, wherein the UE key IE comprises I) a key for finding, within a communication service provider, CSP, domain, UE context information associated with the UE and ii) one or more network identifiers, IDs, identifying a network to which the UE is connected.

34. The UE of claim 33, wherein the UE is further configured to perform the method of any one of claims 2- 8.

35. A first network node (306) being configured to: obtain (s802) a key; after obtaining the key, store (s804) mapping information which maps the key to user equipment, UE, context information associated with a specific UE (102); generate (s806) a UE key information element, IE, which comprises the obtained key and one or more network identifiers, IDs, identifying a network to which the specific UE is connected; andtransmit (s808) to the specific UE (102) a first message including the UE key IE.

36. The first network node of claim 35, wherein the first network node is further configured to perform the method of any one of claims 10-18.

37. A first network node (308) being configured to: receive (s902) from a second network node (306) a first message including a key; determine (s904) that the second network node (306) transmitted the key; and after obtaining the key and determining that the second network node (306) transmitted the key, store (s906) mapping information which maps the key to the second network node (306).

38. The first network node of claim 37, wherein the first network node is further configured to perform the method of any one of claims 20-24.

39. A system (100) comprising a first network node (504), a second network node (308), and a third network node (306), the system being configured to: using the first network node (504), transmit (s1002) to the second network node (308) a find request for finding the third network node (306) which handles a specific network session of a specific user equipment, UE, wherein the find request includes a key for finding, within a communication service provider, CSP, domain, UE context information associated with the specific UE; after the second network node (308) receiving the find request, using the second network node (308), find (s1004), using the key, the third network node (306) handling the specific network session of the specific UE; and after finding the third network node (306), using the second network node (308), transmit (s1006) to the first network node (504) a response to the find request, wherein the response to the find request includes a network node identifier identifying the third network node.

40. The system of claim 39, wherein the system is further configured to perform the method of any one of claims 26-30.

41. An apparatus (1100 or 1200) comprising: a processing circuitry (1102 or 1202); and a memory (1141 or 1241), said memory containing instructions executable by said processing circuitry, whereby the apparatus is operative to perform the method of any one of claims 1-30.

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