Policy-based Call Control in Heterogeneous Video Conference Networks

Abstract

Personal video conferencing is a new and important part of the video conferencing market. Manufacturers of video conferencing equipment face new requirements when entering this market, including the need for increased personalization and flexibility of the services provided to the user. Using policies for call control is a promising approach to meet these requirements. Both SIP and H.323 are important protocols for video conferencing, and this thesis therefore gives proposals for how to design a policy-based call control solution for video conference networks using both of these protocols. This thesis starts with a description of the study performed on existing standards and proposals that may be used in the design of the call control solution. The Common Open Policy Service (COPS), XACML, SAML, Ponder and Appel were studied. COPS, XACML, SAML and Ponder are all designed to be used in management solutions such as policy-based management of QoS networks. Appel is designed to be used for call control. This difference was shown to be significant, and was the main reason for selecting Appel as the proposal to use in a call control solution. An important part of a system design process is identifying the requirements for the system. Use cases for the call control solution were written to find the requirements for this solution. Since these use cases also showed how the call control solution must be integrated with the conference network, main principles of the design of the call control solution were selected during the process of writing these use cases. These principles are described along with the requirements found. A set of main goals is expressed for the call control solution. The solution must provide the same functionality independent of the underlying protocol used (H.323 or SIP). The solution must provide authorization of calls and conferences, control of properties of a call (e.g. the bandwidth used) and call forwarding, busy handling and similar. The thesis includes an evaluation of how Appel can be used to cover the above goals. The evaluation showed that a number of extensions of Appel are needed. Finally a description of two possible architectures for the call control solution is described. These show which units take part of the call control solution, and describes the roles these units play.