What is UDM?
The UDM is the 5G Core network function that serves as the master repository for subscriber data — including authentication credentials, subscription profiles, and service authorisation. It replaces the 4G HSS (Home Subscriber Server) in the 5GC, extending its role in a cloud-native SBA design.
How Does UDM Work?
The UDM exposes the Nudm service interface. It supports: Authentication Credential Repository and Processing Function (ARPF — generating 5G-AKA/EAP-AKA’ vectors for the AUSF), Subscription Identifier De-concealing Function (SIDF — revealing the SUPI from the SUCI), and subscriber data provision to the AMF (mobility subscription), SMF (session subscription), and SMSF (SMS subscription). Persistent data is stored in the UDR (Unified Data Repository).
Use Cases
All 5G subscriber authentication, subscription profile delivery, UE context management during roaming, SMS over NAS subscription data.
3GPP / Standards Reference
3GPP TS 29.503 (Nudm Service Definition), TS 23.502
Related Terms
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