A Methodological Approach to Policy Refinement in Policy-based Management Systems

Current research efforts are being directed to commit with the long-term view of self-management properties for telecommunications networks. One of the key approaches that have been recognised as an enabler of such a view is policy-based management. Policy-based management has been mostly acknowledged as a methodology that provides flexibility, adaptability and support to automatically assign network resources, control Quality of Service and security, by considering administratively specified rules. The hype of policy-based management was to commit with these features in run-time as a result of changeable network conditions resulting from the interactions of users, applications and existing resources. Despite enormous efforts with policy languages, management architectures using policy in different application domains, standardisation and industrial efforts, policy-based management is still not a reality. One reason behind the reticence for its use is the difficulty to analyse policies that guarantee configuration stability. In addition to policy conflict analysis, a key issue for this reticence is the need to derive enforceable policies from high-level administrative goals or from higher level policies, namely the policy refinement process. This Thesis deals with the critical nature of addressing the policy refinement problem. We provide a holistic view of this process, from formal analysis to its practical realisation, identifying the key elements involved in each step of such critical process. We initially propose a policy refinement framework relying on Linear Temporal Logic (LTL), a standard logic that allows analysis of reactive systems. Based on the former logic, we lay down the process of representing policies at different levels of abstraction. Following on with this, we develop the mechanisms that enable the abstraction of enforceable policies from hierarchical requirements in a fully automatic manner, making use of Linear Temporal Logic-based state exploration techniques. In addition, we clarify and identify the activities and management tasks that the administrative parties should carry out during the life cycle of the policy-based management system, from the perspective of the policy refinement process. This Thesis provides the guidelines to address policy refinement in network management contexts. Concretely, we take one step ahead in the materialisation of the policy refinement process by exploiting inherent containment properties of network management systems. For this purpose we provide the methodology to apply the concepts introduced in the policy refinement framework developed in this Thesis in the above context. In this Thesis we also execute a complete and rather detailed policy refinement process for a successful policy-based management solution. Taking the intra-domain Quality of Service Management application domain as background, we clarify and present the implications of the policy refinement problem in such a concrete application domain.