Diameter is an "AAA" (Authorization, Authentication and Accounting) protocol. It is a client/server protocol, used for handling service requests such as
What is IMS?
An overview of the IP Multimedia Subsystem and its architecture
- subscriber validation
- network resource control
- wireless mobility/roaming
- charging and billing applications.
Diameter is already widely deployed, and this is set to continue. The 3GPP, 3GPP2 and TISPAN groups have made Diameter their protocol of choice for subscription, policy and charging function in IMS and other next-generation network architectures.
The Diameter protocol is an IETF standard, RFC 3588. This standard is known as the Diameter base protocol. It defines transport and session level management and support for basic accounting applications. Many application extensions are defined by standards bodies (including the IETF and 3GPP), and other extensions are created by vendors to support their proprietary AAA requirements.
Diameter is upwardly compatible with RADIUS and, as its name suggests, was developed to address many of the limitations of RADIUS and fulfill the needs of modern AAA applications in next-generation networks.
DC-Diameter
The DC-Diameter product is a flexible, portable protocol implementation which allows OEMs to quickly and easily build devices and software that require the Diameter protocol.
DC-Diameter comprises the following portable base components.
- A Protocol Manager component, implementing connection, peer and routing functionality from the base Diameter protocol.
- A User Application Library, providing support in the User Application for session management and application FSM support, including the base authentication, authorization and accounting functionality in the base Diameter protocol.
- An AVP Library, providing assistance for the User Application to build and parse Diameter messages and AVPs, both for standard Diameter applications and for vendor-defined proprietary applications.
DC-Diameter runs within Data Connection's portable, non-blocking, message passing execution environment - the N-BASE. The N-BASE
- minimizes the amount of engineering effort that is required to incorporate DC-Diameter into an OEM device
- facilitates flexible distribution of product components across a wide range of hardware configurations from DSPs to line cards to specialized signaling processors
- incorporates sophisticated debug and diagnostics facilities that substantially ease the integration and subsequent maintenance of the products in an OEM environment.
DC-Diameter Differentiators
The following highlights the feature and architectural differentiators of DCL's DC-Diameter.
Serviceability
DC-Diameter provides a broad range of debug and serviceability options, using the mechanisms provided by the N-BASE infrastructure. These include
- event logging, covering major events down to individual message tracing
- signal and flow tracing
- detailed tracing showing the precise flow of control through the source code, including the contents of key variables
- flexible log filtering and grouping
- rate limiting of logs.
Customizability and Configurability
DC-Diameter includes a number of configuration and customization options to allow system vendors to tailor the function to particular devices, without needing to edit the core DCL code.
Primarily, it is possible to use DC-Diameter to implement a vendor-specific Diameter application. To assist with this, DC-Diameter provides
- a Generic AVP Library to assist in building and parsing AVPs and Diameter messages
- the Diameter Data Interface, which allows direct access to the Diameter Protocol Manager from vendor-specific Application FSMs.
Portability
DC-Diameter runs within Data Connection's portable, non-blocking, message-passing execution environment (the N-BASE). This facilitates flexible distribution of product components across a wide range of hardware configurations, from simple single-CPU platforms to large, distributed, multi-processor routers. Combined with Data Connection's expertise and experience in building both highly available protocol stacks as well as complete turnkey customer solutions, this provides the performance, scalability, and reliability required for the most demanding applications.
Scalability, Distribution and Redundancy
DC-Diameter is designed to scale to the demands of the AAA servers in use today and in the future. This is achieved with a combination of efficient design of the DC-Diameter stack, and the ability to distribute workload between multiple DC-Diameter clients which can be running on separate CPUs or linecards, enabling the ability to support backed-up, redundant components. This is achieved through interaction with Data Connection's High Availability Framework (HAF). The HAF provides built-in support for
- dynamic replication of state between components in different hardware locations
- hot stand-by of backup software components
- detection of failure and automatic promotion of backup components to primary on failure
- hot software upgrade (HSU) and downgrade (HSD)
Finally, DC-Diameter is designed to support concurrent connections to multiple peers, achieving protection from peer or network downtime.
DC-Diameter Product Features
The following lists the features supported by the DC-Diameter software.
Applications and Roles
DC-Diameter supports the following applications and roles.
- IMS Sh, Ph, Dh Subscriber Services Diameter client and server
- IMS Gq', Rq, e2 Policy Services Diameter client and server
- IMS Rf Offline Charging Diameter client and server
- IMS Ro Online Charging Diameter client and server
DC-Diameter's architecture is extensible, so vendors can add their own support for any other standard or proprietary Diameter Application using the base authorization and authentication FSMs.
Base Protocol Support
DC-Diameter supports the following base protocol features.
- Incoming and outgoing connections to multiple peers
- All mandatory requirements defined in the AAA Transport Profile (RFC 3539), including watchdog messages and primary/secondary peer failover
- Error handling, as defined in section 7 of RFC 3588
- The "Client, Stateless" and "Server, Stateless" authorization and authentication FSMs defined in section 8.1 of RFC 3588
- The "Client, Stateless" and "Server, Stateless" accounting FSMs defined in section 8.2 of RFC 3588
- Allocation of hop-by-hop identifiers
- Routing of outgoing messages based on realm and application, as defined in section 6 of RFC 3588
- Tracking of session state
- Allocation of Accounting Record Numbers
- Dynamic DNS lookup of peer hostname
DC-Diameter also supports the following proprietary features.
- IPv6 and VPN-encoded network addresses
- Dynamic specification by the application of the server(s) to which a particular message is sent
- Flexible configuration based on a standard IETF MIB, draft-zorn-dime-base-protocol-mib
- Local configuration, peer configuration and configuration of known peers per realm
- Fault-tolerant replication of configuration to a backup, enabling carrier-class (99.999%) redundancy and hot software upgrade between versions of DC-Diameter
IP Transport, Security and Compression
Note that DC-Diameter requires the existence of an IP stack that supports all required transport protocols, security protocols and compression function. DC-Diameter communicates with the IP stack through the IP Sockets Interface.
DC-Diameter offers the following level of support for IP transports.
- Support in DC-Diameter and the IP Sockets Interface for TCP and STCP peer connections (both IPv4 and IPv6)
- Out-of-the-box support for TCP peer connections on certain standard OSs
- Out-of-the-box support for SCTP peer connections via integration of the sample IP Sockets stub
DC-Diameter supports IP security protocols as follows.
- Compatible with IPsec solutions implemented either within the IP stack or below
- Compatible with TLS
DC-Diameter supports IP compression protocols as follows.
- Compatible with IKE or TLS compression, when these are implemented below DC-Diameter
For more information about Data Connection's Diameter products, expertise and availability contact dcdiameter@dataconnection.com.