Diameter

The IETF AAA protocol that replaces RADIUS in modern mobile cores, standardised in RFC 6733 and extended by 3GPP for use across LTE, IMS, and parts of 5G. Diameter handles authentication, authorisation, charging, and policy interactions between elements such as MME, HSS, PCRF, and OCS. While it adds peer-to-peer transport (TCP/SCTP) and TLS/IPsec capability, in practice operators often deploy it without strong inter-PLMN authentication, leaving it exposed to many of the same location-tracking, interception, and denial-of-service attacks that affect SS7. GSMA FS.19 defines the equivalent Category 1/2/3 filtering controls.

Categories: Radio Access NetworkCore NetworkSignaling

Diameter in context

The radio access network is where mobile devices attach to the operator's infrastructure. Attacks in this layer include IMSI catching, rogue base stations and downgrade attacks; defenses rest on mutual authentication, integrity-protected signaling and Open RAN supply-chain hygiene.

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.

To place Diameter in the wider telecom-security picture, review 5G SA, AMF, Base Station (BS), Capacity Planning, CAPEX and CSCF — each entry cross-references back to this page so you can walk the topic in either direction.

Related terms

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.