5G Interview Questions Answers 32-36

Q32. What is UDM? What is the essential function of UDM in 5G NR?

Ans. The Unified Data Management (UDM) includes support for the following functionality:

1. Generation of 3GPP AKA Authentication Credentials.
2. User Identification Handling (e.g. storage and management of SUPI for each subscriber in the 5G system).
3. Support of de-concealment of privacy-protected subscription identifier (SUCI).
4. Access authorization based on subscription data (e.g. roaming restrictions).
5. UE's Serving NF Registration Management (e.g. storing serving AMF for UE, storing serving SMF for UE's PDU Session).
6. Support to service/session continuity e.g. by keeping SMF/DNN assignment of ongoing sessions.
7. MT-SMS delivery support.
8. Lawful Intercept Functionality (especially in outbound roaming case where UDM is the only point of contact for LI).
9. Subscription management.
10. SMS management.
11. 5GLAN group management handling.
12. Support of external parameter provisioning (Expected UE Behaviour parameters or Network Configuration parameters).

To provide this functionality, the UDM uses subscription data (including authentication data) that may be stored in UDR, in which case a UDM implements the application logic and does not require an internal user data storage and then several different UDMs may serve the same user in different transactions.
NOTE 1: The interaction between UDM and HSS, when they are deployed as separate network functions, is defined in 3GPP TS 23.632 and TS 29.563 or it is implementation specific.
NOTE 2: The UDM is located in the HPLMN of the subscribers it serves, and access the information of the UDR located in the same PLMN.

Q33. What is AUSF? What is the essential function of AUSF in 5G NR?

Ans. AUSF Functionality:

1. The authentication server function (AUSF) is in a home network and performs authentication with the UE.
2. It decides on UE authentication, but it depends on the some back-end services for computing authentication data and keying content when 5G-AKA or EAP-AKA 'is used.
3. also provide Supports for authentication for 3GPP access and untrusted non-3GPP access

Q34. What is NEF? What is the essential function of NEF in 5G NR?

Ans. The Network Exposure Function (NEF) supports the following independent functionality:

1. Exposure of capabilities and events:
2. NF capabilities and events may be securely exposed by NEF for e.g. 3rd party, Application Functions and Edge Computing.
3. NEF stores/retrieves information as structured data using a standardized interface (Nudr) to the Unified Data Repository (UDR).
4. Secure provision of information from external application to 3GPP network:
5. It provides a means for the Application Functions to securely provide information to 3GPP network, e.g. Expected UE Behaviour, 5GLAN group information and service specific information. In that case the NEF may authenticate and authorize and assist in throttling the Application Functions.
6. Translation of internal-external information:
7. It translates between information exchanged with the AF and information exchanged with the internal network function. For example, it translates between an AF-Service-Identifier and internal 5G Core information such as DNN, S-NSSAI, as described in clause 5.6.7.
8. In particular, NEF handles masking of network and user sensitive information to external AF's according to the network policy.
9. The Network Exposure Function receives information from other network functions (based on exposed capabilities of other network functions). NEF stores the received information as structured data using a standardized interface to a Unified Data Repository (UDR). The stored information can be accessed and "re-exposed" by the NEF to other network functions and Application Functions, and used for other purposes such as analytics.
10. A NEF may also support a PFD Function: The PFD Function in the NEF may store and retrieve PFD(s) in the UDR and shall provide PFD(s) to the SMF on the request of SMF (pull mode) or on the request of PFD management from NEF (push mode), as described in 3GPP TS 23.503.
11. A NEF may also support a 5GLAN Group Management Function: The 5GLAN Group Management Function in the NEF may store the 5GLAN group information in the UDR via UDM as described in 3GPP TS 23.502.
12. Exposure of analytics:
13. NWDAF analytics may be securely exposed by NEF for external party, as specified in 3GPP TS 23.288.
14. Retrieval of data from external party by NWDAF:
15. Data provided by the external party may be collected by NWDAF via NEF for analytics generation purpose. NEF handles and forwards requests and notifications between NWDAF and AF, as specified in 3GPP TS 23.288.
16. Support of Non-IP Data Delivery:

NEF provides a means for management of NIDD configuration and delivery of MO/MT unstructured data by exposing the NIDD APIs as described in 3GPP TS 23.502 on the N33/Nnef reference point.
A specific NEF instance may support one or more of the functionalities described above and consequently an individual NEF may support a subset of the APIs specified for capability exposure.
NOTE: The NEF can access the UDR located in the same PLMN as the NEF.
The services provided by the NEF.

• The IP address(es)/port(s) of the NEF may be locally configured in the AF, or the AF may discover the FQDN or IP address(es)/port(s) of the NEF by performing a DNS query using the External Identifier of an individual UE or using the External Group Identifier of a group of UEs, or, if the AF is trusted by the operator, the AF may utilize the NRF to discover the FQDN or IP address(es)/port(s) of the NEF.

For external exposure of services related to specific UE(s), the NEF resides in the HPLMN. Depending on operator agreements, the NEF in the HPLMN may have interface(s) with NF(s) in the VPLMN.
When a UE is capable of switching between EPC and 5GC, an SCEF+NEF is used for service exposure.

Q35. What is NRF? What is the essential function of NRF in 5G NR?

Ans. The Network Repository Function (NRF) supports the following functionality:

1. Supports service discovery function. Receive NF Discovery Request from NF instance or SCP, and provides the information of the discovered NF instances (be discovered) to the NF instance or SCP.
2. Supports P-CSCF discovery (specialized case of AF discovery by SMF).
3. Maintains the NF profile of available NF instances and their supported services.
4. Maintains SCP profile of available SCP instances.
5. Supports SCP discovery by SCP instances.
6. Notifies about newly registered/updated/ deregistered NF and SCP instances along with its potential NF services to the subscribed NF service consumer or SCP.
7. Maintains the health status of NFs and SCP.
8. In the context of Network Slicing, based on network implementation, multiple NRFs can be deployed at different levels.
9. PLMN level (the NRF is configured with information for the whole PLMN),
10. shared-slice level (the NRF is configured with information belonging to a set of Network Slices),
11. slice-specific level (the NRF is configured with information belonging to an S-NSSAI).
12. In the context of roaming, multiple NRFs may be deployed in the different networks.
13. the NRF(s) in the Visited PLMN (known as the vNRF) configured with information for the visited PLMN.
14. the NRF(s) in the Home PLMN (known as the hNRF) configured with information for the home PLMN, referenced by the vNRF via the N27 interface.

Q36. What is Network Slicing? What is the essential function of NSSF in 5G NR?

Ans. The Network Slice Selection Function (NSSF) supports the following functionality:

1. Selecting the set of Network Slice instances serving the UE;
2. Determining the Allowed NSSAI and, if needed, the mapping to the Subscribed S-NSSAIs;
3. Determining the Configured NSSAI and, if needed, the mapping to the Subscribed S-NSSAIs;
4. Determining the AMF Set to be used to serve the UE, or, based on configuration, a list of candidate AMF(s), possibly by querying the NRF.