Take a look at Mobicents Diameter.
http://www.mobicents.org/diameter/index.html
LGPL License.
Thorough standards coverage:
- Diameter Base (IETF RFC 3588)
- Diameter Credit-Control Application (IETF RFC 4006)
- IMS Sh Interface (3GPP TS 29.328 and 3GPP TS 29.329)
- IMS Rf Interface (3GPP TS 32.225 and 3GPP TS 32.299)
- IMS Ro Interface (3GPP TS 32.225 and 3GPP TS 32.299)
- IMS Cx Interface (3GPP TS 29.228 and 3GPP TS 29.229)
- IMS Dx Interface (3GPP TS 29.228 and 3GPP TS 29.229)
Rich feature set:
- High-Availability/Fault-Tolerance support both at stack level and at Mobicents JAIN SLEE Resource Adaptors. Learn more about the architecture on the High-Availability/Fault-Tolerance Overview section.
- Statistics generation, to enable monitoring of the Diameter stack, know it's average load, number of received requests, processing time per request, etc.;
- Overload Monitor, configurable per Diameter application, allowing the stack to reject new requests when overloaded;
- Simple XML Configuration through one XML file, the whole stack (own peer, realms, peers, timeout parameters, etc.) can be configured;
- Management facilities, allowing to remotely manage and monitor the stack by the standard JMX (Java Management Extensions) API and also though an GUI provided by a plugin to be used in the RHQ/JON management interface;
- Message Validation both for incoming and outgoing messages, with configurable depth;
- Extension Points allowing quickly to test custom implementations for several core functions, such as load-balancing, replicated datasources, etc;
- Easily extendable and customizable Diameter Applications by adding new AVP definitions and state machine behaviors
Vibrant international community of users and contributors:
http://groups.google.com/group/mobicents-public/topics