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Security Fundamentals & Crypto · Intermediate

Diameter

AAA protocol designed as a successor to RADIUS, using TCP or SCTP on port 3868.

Definition

Diameter (RFC 6733) adds reliable transport, larger attribute space, failover, and peer-to-peer capability. It is widely used in 4G LTE and IMS mobile networks for subscriber authentication and policy. Enterprise network access still mostly uses RADIUS.

Example

An LTE network's MME queries the HSS via Diameter to authenticate a subscriber.

Exam tip

Diameter is the 'twice a RADIUS' successor; know it mainly from mobile carrier networks.

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