The Open Settlement Protocol is a client/server protocol used by Internet service providers to exchange authorization, accounting, and usage information to support IP telephony. Open Settlement Protocol is implemented in voice telephony gateways such as softswitches, H.323 multimedia conferencing gateways, and Session Initiation Protocol proxies. OSP is defined by the European Telecommunications Standards Institute Project TIPHON. A press release of September 2, 1998, announced that the industry leaders 3Com Corporation, Cisco, GRIC Communications, iPass Inc., and TransNexus had "teamed up to promote inter-domain authentication, authorization and accounting standards for IP telephony through the Open Settlement Protocol ". The Open Settlement Protocol is being developed under the authority of the European Telecommunications Standards Institute's ETSI project TIPHON. The TIPHON project objective is One of the benefits of the new Open Settlement Protocol is: "flexible and feature-richinformation exchange via the Extensible Markup Language". The message system defined in the protocol architecture uses HTTP to communicate the principal message content; this includes a MIME header together with the XML document in a <Message>. Open Settlement Protocol standard specification may be found in the document ETSI Technical Specification 101 321: Telecommunications and Internet Protocol Harmonization Over Networks Release 4: Open Settlement Protocol for Inter-domain pricing, authorisation, and usage exchange. Version 4.1.1 of this document was ratified in November 2003. The document's statement of scope reads: Section 6 XML element and attribute declarations in this section define the provisional DTD for the Open Settlement Protocol. The OSP Toolkit is a complete development kit for software developers who want to implement the client side of the European Telecommunication Standards Institute's OSP standard for secure VoIP peering. The OSP Toolkit includes source code written in ANSI C, test tools and extensive documentation on how to implement the OSP standard. A hosted OSP test server is freely available on the Internet for all developers to test their OSP implementation.
