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This document describes the representation of a session authorization policy element for supporting policy-based per-session authorization and admission control. The goal of session authorization is to allow the exchange of information between network elements in order to authorize the use of resources for a service and to co-ordinate actions between the signaling and transport planes. This document describes how a process on a system authorizes the reservation of resources by a host and then provides that host with a session authorization policy element which can be inserted into a resource reservation protocol (e.g., the Resource ReSerVation Protocol (RSVP) PATH message) to facilitate proper and secure reservation of those resources within the network. We describe the encoding of session authorization information as a policy element conforming to the format of a Policy Data object (RFC 2750) and provide details relating to operations, processing rules and error scenarios.

Abstract:Policies may be required in various scenarios during a multimedia flow set up, for example, during session setup, policy decisions must be provided to ensure that the session being requested lie within the bounds of the service profile established for the requesting host. Similarly, when a host requests resources to provide a certain QoS for a packet flow, policies may be provided to ensure that the required resources lie within the bounds of the resource profile established for the requesting host. The policy framework at the IETF [1] is focused on the resource reservation issues and thus provided a centralized approach for the policy decision function. This paper attempts to highlight the various scenarios in a multimedia flow establishment that lead to a distributed approach for policy decision-making. The paper also discusses the required characteristics of an interface between the policy decision functions residing in different administrative domains.