Model and Architecture of a Timing Service for Adaptive Policy-Based Management Systems

Policy-based management (PBM) is a promising approach to realize adaptivity in networks that would be hard - if not impossible - for administrators to configure manually. In PBM systems, the network configuration is not directly expressed in terms of low-level properties, such as IP or MAC addresses; rather, complex business entities, such as users or departments, can be defined and allow the administrators to specify high-level network policies. Even though PBM can reduce the effort for managing complex networks significantly, today's solutions lack a generic way for expressing adaptive policies. A PBM system can be called adaptive if the decision of when and in which order policies are activated is not only based on fixed predefined dates but the system also takes environmental and internal events into account. In this paper we describe a model of adaptive timing constraints and introduce an architecture for executing timing specifications (sets of constraints). Within a timing specification, the administrator usually creates single constraints only implicitly by defining the lifetime of managed resources, sequences of events, and high- level temporal relationships between them. Because each timing constraint defines a < relation between two single events, a timing specification can be described as a partial ordering of events over the event space. During execution, a timing service triggers PBM systems to activate, inactivate, or adapt management policies according to the timing specification.