DIAMETER is a computer networking protocol for AAA (Authentication, Authorization and Accounting). It is a successor to RADIUS. In computer security, AAA stands for “authentication, authorization and accounting”. Authentication  Authentication refers to the confirmation that a user who is requesting services is a valid user of the network services requested. ... Remote Authentication Dial In User Service (RADIUS) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ...

Upgrade from RADIUS

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 : Remote Authentication Dial In User Service (RADIUS) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ... This article or section does not cite its references or sources. ...

• it uses reliable transport protocols (TCP or SCTP, not UDP)
• it can use network or 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 is a client-server protocol, with exception of supporting some server-initiated messages as well
• both stateful and stateless models can be used
• it has dynamic discovery of peers (using DNS SRV and NAPTR)
• it has capability negotiation
• it supports application layer acknowledgements, defines failover methods and state machines (RFC 3539)
• it has error notification
• it has better roaming support
• it is more easily extended; new commands and attributes can be defined
• it is aligned on 32 bit boundaries
• it has basic support for user-sessions and accounting

The Transmission Control Protocol (TCP) is one of the core protocols of the Internet protocol suite. ... In the field of computer networking, the IETF Signaling Transport (SIGTRAN) working group defined the Stream Control Transmission Protocol (SCTP) as a transport layer protocol in 2000. ... User Datagram Protocol (UDP) is one of the core protocols of the Internet protocol suite. ... IPsec (IP security) is a suite of protocols for securing Internet Protocol (IP) communications by authenticating and/or encrypting each IP packet in a data stream. ... Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL), are cryptographic protocols that provide secure communications on the Internet for such things as web browsing, e-mail, Internet faxing, instant messaging and other data transfers. ... Remote Authentication Dial In User Service (RADIUS) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ... Client/Server is a network application architecture which separates the client (usually the graphical user interface) from the server. ... It has been suggested that this article be split into multiple articles. ... An SRV record or Service record is a category of data in the Internet Domain Name System specifying information on available services. ... NAPTR stands for Naming Authority Pointer and is a newer type of DNS record that supports regular expression based rewriting. ... Roaming is a general term in wireless telecommunications that refers to the extending of connectivity service in a location that is different from the home location where the service was registered. ...

Protocol description

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. An application is not a program, but a protocol based on Diameter. Diameter security is provided by IPSEC or TLS, both well-regarded protocols. IPsec (IP security) is a suite of protocols for securing Internet Protocol (IP) communications by authenticating and/or encrypting each IP packet in a data stream. ... Transport Layer Security (TLS) and its predecessor, Secure Sockets Layer (SSL), are cryptographic protocols that provide secure communications on the Internet for such things as web browsing, e-mail, Internet faxing, instant messaging and other data transfers. ...

Packet format

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Commands

Each command is assigned a command code, which is used for both requests and answers.

Attribute-Value Pairs (AVP)

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State machines

Message flows

Applications

A Diameter Application is not a software application, but a protocol based on the DIAMETER Base protocol (defined in RFC 3588). Each application is defined by an application identifier and can add new command codes and/or new mandatory AVPs. Adding a new optional AVP does not require a new application. This article does not cite any references or sources. ...

Examples of Diameter applications :

• Diameter Mobile IPv4 Application (MobileIP, RFC 4004)
• Diameter Network Access Server Application (NASREQ, RFC 4005)
• Diameter Extensible Authentication Protocol Application (RFC 4072)
• Diameter Credit-Control Application (DCCA, RFC 4006)
• Diameter Session Initiation Protocol Application (RFC 4740)
• various applications in the 3GPP IP Multimedia Subsystem
• 3GPP GBA (Generic Bootstrapping Architecture): Bootstrapping Server Function

Diameter Credit-Control Application, DCCA in short, is a DIAMETER application used for credit control. ... The IP Multimedia Subsystem (IMS) is an architectural framework for delivering internet protocol (IP) multimedia to mobile users. ... BSF Positioning A Bootstrapping Server Function (BSF) is an element in the Cellular network which delivers functions to authenticate user equipment for additional services as Mobile TV and others. ...

External links

• http://www.cisco.com/en/US/products/ps6638/products_data_sheet09186a00804fe332.html Cisco page outlining differences between RADIUS and DIAMETER
• http://sourceforge.net/projects/openblox/ Open Source Java IMS optimised Full Diameter solution