BSF (Binding Support Function)

In telecom networks, the BSF is a 5G Network Function that maintains bindings between a UE's PDU Session and the PCF instance serving it, enabling consistent policy decisions across the SBA. The BSF is queried by NFs that need to discover the correct PCF for a given subscriber session.

Categories: Core NetworkIdentity and SubscriberOperations and Business

BSF in context

The mobile core carries subscriber sessions, mobility and policy. In 4G it is the EPC (MME, HSS, S/PGW); in 5G it is the Service-Based Architecture with AMF, SMF, UPF, AUSF, UDM and the NRF.

Subscriber identifiers (IMSI, SUPI, MSISDN, IMEI) anchor authentication, charging and lawful interception. Any protocol that leaks a permanent identifier is treated as a privacy defect, which is why 5G introduced SUCI concealment on the air interface.

To place BSF in the wider telecom-security picture, review PDN, ARPU, Confidentiality, Cryptography, CSPM and DRP — each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

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Browse the full TelcoSec Glossary, the Ultimate Guide to Mobile Network Security, or the P1 Arsenal of telecom-security tools.