Diameter
Diameter is the AAA backbone of LTE and IMS networks. If you build carrier infrastructure or work on 4G/5G billing and policy enforcement, you'll encounter Diameter on the S6a, Rx, Gx, and Gy interfaces.
What It Defines
Diameter is the successor to RADIUS for carrier-grade AAA. Provides reliable TCP/SCTP transport, application extensibility via AVPs (Attribute-Value Pairs), peer discovery, capability negotiation, and structured error handling. Core to LTE/4G EPC (S6a interface to HSS, Rx/Gx for policy, Gy for online charging) and IMS signaling.
Canonical (Normative)
Related References
The canonical publication point for finalized RFCs. If a protocol is standardized as an RFC, the RFC Editor text is the normative final reference. Published by the IETF, IRTF, IAB, and independent stream.
Related Specs
RADIUS is the AAA protocol behind every enterprise Wi-Fi login, VPN authentication, and 802.1X deployment. FreeRADIUS, Cisco ISE, and Aruba ClearPass all implement it. Essential for understanding corporate network access and SSO integration.
LTE is the dominant global mobile network. VoLTE, QoS bearers, and EPC architecture are directly relevant when building mobile-connected applications, IoT modules, or carrier infrastructure.