Diameter

For the geometric term, see diameter.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Diameter is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. The basic concept is to provide a base protocol that can be extended in order to provide AAA services to new access technologies. Diameter is intended to work in both local and roaming AAA situations.

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

The name is a pun on the RADIUS protocol, which is the predecessor (a diameter is twice the radius). Diameter is not directly backwards compatible, but provides an upgrade path for RADIUS. The main differences are :

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

• it uses reliable transport protocols (TCP or SCTP, not UDP)
• it uses transport level security (IPSEC or TLS)
• it has transition support for RADIUS
• it has larger address space for AVPs (Attribute Value Pairs) and identifiers (32-bit instead of 8-bit)
• it's a peer-to-peer protocol, not client-server : supports server-initiated messages
• both stateful and stateless models can be used
• it has dynamic discovery of peers (using DNS)
• it has capability negotiation
• it supports application layer acknowledgements, defines failover methods and statemachines (RFC 3539)
• it has error notification
• it has better roaming support
• it is easier extended, new commands and attributes can be defined
• basic support for user-sessions and accounting is built in

The Diameter Base Protocol is defined by RFC 3588, and defines the minimum requirements for an AAA protocol. Diameter Applications can extend the base protocol, by adding new commands and/or attributes. Examples of Diameter applications currently in preparation are:

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

• Mobile IPv4 Application (MobileIP, RFC 4004)
• Network Access Server Application (NASREQ, RFC 4005)
• Extensible Authentication Protocol Application (EAP, RFC 4072)
• Credit-Control Application (DCCA, RFC 4006)
• Session Initiation Protocol Application (SIP)
• various applications in the 3GPP IP Multimedia Subsystem (IMS)
Diameter: External links ►



 

RADIUS: :For other senses of this word, see radius (disambiguation)....

Backwards compatible: REDIRECT backward compatibility...