Current proposals dealing with authorization of media streams for multimedia services like IP telephony and video assume a pre- established relationship between elements of the network (e.g. session managers, edge routers, policy servers and end hosts). In some environments, however, such pre-established relationships may not exist either due to the complexity of creating these associations a priori (e.g. in a network with many elements), or due to the different business entities involved (e.g. service provider and access provider), or due to the dynamic nature of these associations (e.g. in a mobile environment). In this document, we describe scenarios where there is no pre- established relationship between entities and describe mechanisms for exchanging information between network elements in order to authorize the use of resources for a service and to co-ordinate actions between the session and bearer control planes.