Systems and methods of establishing IP telephony sessions between enterprises are disclosed. A first enterprise requests an association with a second enterprise. Both enterprises and the second enterprise belong to the same federation. The association request is accepted, to establish an association between the first and second enterprises. In response to the acceptance, a direct routed path is established between the first enterprise and the second enterprise. One of the associated enterprises requests activation of an IP telephony service. If the request to activate references the association, an IP telephony session is established using the direct routed path.