Open Settlement Protocol (OSP) is the European Telecommunications Standards Institute (ESTI) Technical Specification 101 321 for Inter-Domain pricing, authorization and usage exchange. Is a client/server protocol that Internet Service Providers use to exchange authorization, accounting, and usage information to support IP telephony. The OSP protocol is often used with Public Key Infrastructure (PKI) services to implement secure, multi-lateral VoIP peering on non-secure networks, such as the Internet.
