Plain-language definition
The AAA and signaling protocol of 4G/5G cores.
Technical definition
Diameter (RFC 6733) defines a base protocol with applications for S6a/S6d, Cx/Dx, Sh, Rx, Gx, Gy, Gz, Ro, Rf and S9; it runs over SCTP or TCP with optional TLS/DTLS.
Why it matters
Diameter connects HSS, PCRF, OCS and IMS; a DRA routes it at scale.
Last reviewed 2026-09-12 by the Guardivia QoS Engineering Team. Product facts on this page describe current capabilities; items marked “where supported”, “optional”, “integration” or “consultancy” are confirmed per deployment.