Handling Policy Conflicts in Call Control

Policies are becoming increasingly important in modern computer systems as a mechanism for end users and organisations to exhibit a level of control over software. Policies have long been established as an effective mechanism for enabling appropriate access control over resources, and for enforcing security considerations. However they are now becoming valued as a more general management mechanism for large-scale heterogeneous systems, including those exhibiting adaptive or autonomic behaviour. In the telecommunications domain, features have been widely used to provide users with (limited) control over calls. However, features have the disadvantage that they are low-level and implementation-oriented in nature. Furthermore, apart from limited parameterisation of some features, they tend to be very inflexible. Policies, in contrast, have the potential to be much higher-level, goaloriented, and very flexible. This paper presents an architecture and its realisation for distributed and hierarchical policies within the telecommunications domain. The work deals with the important issue of policy conflict – the analogy of feature interaction

The ACCENT Policy Server

The designs expressed in this report are copyright of the University of Stirling. Certain aspects may also be protected by patents held by Mitel Networks Corporation. Publication of this report does not confer the right to use or adapt these designs in whole or in part. The ACCENT project was concerned with developing a practical and comprehensive policy language for call control. The project therefore studied a number of distinct tasks: the definition of the language, and also a threelayer architecture for deploying and enforcing policies defined in the language. This document focuses on the policy system layer of the three-layer architecture. The policy system layer is concerned with storing, deploying and enforcing policies. It represents the core functionality of the three-layer architecture. This report discusses the prototype implementation at a technical level. It is intended as supporting documentation for developers continuing to enhance the prototype, as well as those wishing to gain an insight into the technical details of the policy server layer