Remote Access Dial-In User Service (RADIUS)

RADIUS is a #User Datagram Protocol (UDP) developed by Livingston Enterprises in mid-1990s which provides centralised #Triple A (AAA) services to their network access server (NAS) devices. It supports Link Encryption# and maximum attribute data size of 255 octets (8 bit). It has implicit support of agent support, meaning the agent behaviours might be implemented in a RADIUS server. RADIUS protocol is standardised by RFC 2138, RFC 2139, RFC 2865, RFC 2866 and RFC 2869.

The client from the user side will initiate a request to remote access server (which could be NAS or other Network Device, that has RADIUS client installed) to gain network access. The server will ask the user for credentials, which the user will provide. It forwards the request alongside with the authentication information to an AAA server, where it checks the information against the database that stores user information (e.g., Active Directory, Novell NetWare eDirectory, or UNIX NIS). The AAA server will return the success or failure of the authentication to the RADIUS client (that is the NAS in this case), and if it is a success, the remote access server will grant the network access to the user client.

The peer discovery is done by static configuration which come out of short when comparing to Diameter which support dynamic lookup.

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User Datagram Protocol (UDP)

Remote Access Dial-In User Service (RADIUS)#
Triple A (AAA)

Remote Access Dial-In User Service (RADIUS)#
Diameter

Comparing to Remote Access Dial-In User Service (RADIUS), it supports transport layer security such as IP Security (IPsec) and Transport Layer Security (TLS). Furthermore, it has larger address space for Attribute Value Pairs (AVP) and identifiers (32-bit instead of 8-bit). Moreover, it supports application layer acknowledgements and has error notification, basic support for user-sessions and accounting, and better roaming support than RADIUS. It is also more easily extended. It also supports both stateful and stateless models.

Diameter is a new #Triple A (AAA) protocol standardised by RFC3588 and RFC4005. It is derived from and aim to replace Remote Access Dial-In User Service (RADIUS) (also provides the transition support) with enhancements such as error handling and message delivery reliability. Instead of relying on a central AAA server, it employs a peer-to-peer architecture, which means that every host or node that implements Diameter could act as either a server or client, with additional support of peer discovery via static configuration or dynamic lookup. The protocols in used by Diameter are connection-oriented protocols such as #Transmission Control Protocol (TCP) and Stream Control Transmission Protocol (SCTP) with a maximum attribute data size of 16,777,215 octets (8 bit). It supports both Link Encryption# and End-to-end Encryption (e2e)#.

#security