Scope and Applicability The Framework document for policy-based admission control [RAP] describes the various components that participate in policy decision making (i.e.@ PDP@ PEP and LDP). The emphasis of PREEMPTION_PRI elements is to be simple@ stateless@ and light-weight such that they could be implemented internally within a node's LDP (Local Decision Point). Certain base assumptions are made in the usage model for PREEMPTION_PRI elements: - They are created by PDPs In a model where PDPs control PEPs at the periphery of the policy domain (e.g.@ in border routers)@ PDPs reduce sets of relevant policy rules into a single priority criterion. This priority as expressed in the PREEMPTION_PRI element can then be communicated to downstream PEPs of the same policy domain@ which have LDPs but no controlling PDP. - They can be processed by LDPs PREEMPTION_PRI elements are processed by LDPs of nodes that do not have a controlling PDP. LDPs may interpret these objects@ forward them as is@ or perform local merging to forward an equivalent merged PREEMPTION_PRI policy element. LDPs must follow the merging strategy that was encoded by PDPs in the PREEMPTION_PRI objects. (Clearly@ a PDP@ being a superset of LDP@ may act as an LDP as well). - They are enforced by PEPs PREEMPTION_PRI elements interact with a node's traffic control module (and capacity admission control) to enforce priorities@ and preempt previously admitted flows when the need arises.