implement a policy decision element in- ternal to the IP BS manager in the GGSN. The IP policy architecture does not mandate the policy decision point to be external to the GGSN. Whenever resources not owned or controlled by the UMTS network need to provide QoS, inter-work with an external re- source manager that controls those resources takes place. 9.9.2.1 IP BS Manager The IP BS manager utilizes standard IP mechanisms to manage the IP bearer service. These mechanisms may be different from mechanisms used within the UMTS, and may have different parameters controlling the service. The translation/mapping function supports the inter-working between the mechanisms and parameters used within the UMTS and the external IP bearer service, and interacts with the IP BS manager. When an IP BS manager exists both in the UE and the gateway node, these IP BS managers may communicate directly with each other by using relevant signalling protocols. Table 9.2 illustrates the minimum functionality that may be supported by equipment, in order to allow multiple network operators to provide inter-working between their networks for end-to-end QoS. The IP BS managers in the UE and GGSN provide the set of capa- bilities for the IP bearer level. As noted, provision of the IP BS manager is optional in the UE, and required in the GGSN. The UMTS Network and Radio Access Technology Table 9.2 IP BS manager capability in the UE and GGSN [7]. Capability DiffServ edge function Optional Required RSVP/IntServ Optional Optional IP policy enforcement point Optional Required* *Although the capability of IP policy enforcement is required within the GGSN, the control of IP policy through the GGSN is a network operator choice. 9.9.2.2 IP Policy Control The IP policy control stands as a logical policy decision element, which applies stan- dard IP mechanisms to implement policy in the IP bearer layer. These mechanisms may conform, e.g. to the framework defined in IETF [RFC2573] A Framework for Policy- based Admission Control, where the IP policy contro