We study the problem of constructing multicast trees to meet the quality of service requirements of real-time, interactive applications operating in high-speed packet-switched environments. In particular, we assume that multicast communication depends on (a) bounded delay along the paths from the source to each destination, and (b) bounded variation among the delays along these paths. We rst establish that the problem of determining such a constrained tree is NP-complete. We then derive heuristics that demonstrate good average case behavior in terms of the maximum inter-destination delay variation of the nal tree. In addition, our heuristics achieve their best performance under conditions typical of multicast scenarios in high-speed networks. We also show that it is possible to dynamically reorganize the initial tree in response to changes in the destination set, in a way that is minimally disruptive to the multicast session.

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Abstract. IPSec (Internet Security Protocol Suite) functions will be executed correctly only if its policies are correctly specified and configured. Manual IPSec policy configuration is inefficient and error-prone. An erroneous policy could lead to communication blockade or serious security breach. In addition, even if policies are specified correctly in each domain, the diversified regional security policy enforcement can create significant problems for end-to-end communication because of interaction among policies in different domains. A policy management system is, therefore, demanded to systematically manage and verify various IPSec policies in order to ensure an end-to-end security service. This paper contributes to the development of an IPSec policy management system in two aspects. First, we defined a high-level security requirement, which not only is an essential component to automate the policy specification process of transforming from security requirements to specific IPSec policies but also can be used as criteria to detect conflicts among IPSec policies, i.e. policies are correct only if they satisfy all requirements. Second, we developed mechanisms to detect and resolve conflicts among IPSec policies in both intradomain and inter-domain environment.