Whilst SAML-based federations are most often used by
academic and semi-commercial institutions that focus only
on attribute-based authentication, we foresee a growing
interest for service providers providing charged services.
Since more and more academic and semi-commercial federation
participants offer Voice-over-IP (VoIP) services, this
type of service provides an entry point into identity federation based payment. Therefore, this paper describes an
approach on how to harmonize the SAML-based federation
technology with the needs of a payment infrastructure
for enabling charging of VoIP services within a federation.
However, since the different aspects of our approach (SAML
Payment, SIP Discovery and Tariff Function) are not bound
to VoIP applications, each one of them could be used separately or combined for several service types.