AF (Application Function)

AF in context

The mobile core is where subscriber sessions, mobility and policy live. 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. Core exposure is the difference between a single-subscriber leak and a fleet-wide breach.

Telecom security is written into standards from 3GPP, GSMA, ETSI, IETF and ITU-T. Understanding which body owns which specification, and how the specs interlock (for example 3GPP TS 33.501 with GSMA FS.34 for 5G SBA security), is essential for both design and audit work.

To place AF in the wider telecom-security picture, review URSP, SCP, N3IWF, Authorization, Network Exposure Function (NEF) and PRD.

Related terms

• URSP
• SCP
• N3IWF
• Authorization
• Network Exposure Function (NEF)
• PRD
• Zeroconf
• TSC

Related topic hubs

• 5G NEF Security Network Exposure Function security in the 5G core.
• 5G Security 5G SBA, SEPP, SUCI, 5G-AKA, N32 and service-based interface security.
• 5G Penetration Testing Pentesting the 5G core, SBA, SEPP, and gNB interfaces.
• 5G Security Training Training on 5G core, SBA, N32, SUCI and radio security.

More from the TelcoSec Glossary

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