QoS Evaluation of IP Telephony Services: A Specification Language Based Simulation Software Tool

This article reports on our experience in using the EMPAgr/TwoTowers technology, we have developed in the past six years, in order to provide support to the design of new protocols for audio communications over IP, to the verification of correctness related properties, and to the assessment of the Quality of Service (QoS) of different design alternatives as well as the performance comparison with other existing protocols. The novelty of our approach amounts to the use of an executable specification language extended with performance modeling capabilities (called EMPAgr) to precisely describe protocols at a suitable level of abstraction. Our approach based on formal techniques may be advantageous with respect to conventional simulators routinely used by network engineers because, besides allowing the quality and the efficiency of the specified protocols to be assessed, it provides a compositional support to system modeling at a high level of abstraction and is capable of verifying functional properties of systems.