One of the more popular policy criteria is the rank of importance of a flow relative to the others competing for admission into a network node. Preemption Priority takes effect only when a set of flows attempting admission through a node represents overbooking of resources such that based on CAC some would have to be rejected. The overall length of the policy element, in bytes. This value is registered with IANA, see Section 7. The priority of the new flow compared with the defending priority of previously admitted flows.
Higher values represent higher Priority.
Once a flow was admitted, the preemption priority becomes irrelevant. Instead, its defending priority is used to compare with the preemption priority of new flows. For any specific flow, its preemption priority must always be less than or equal to the defending priority. This provides a mechanism for balancing between order dependency and priority. Denial of service is virtually the inverse of the free-rider problem.