Evolutionary computation: comments on the history and current state

Evolutionary computation has started to receive significant attention during the last decade, although the origins can be traced back to the late 1950's. This article surveys the history as well as the current state of this rapidly growing field. We describe the purpose, the general structure, and the working principles of different approaches, including genetic algorithms (GA) (with links to genetic programming (GP) and classifier systems (CS)), evolution strategies (ES), and evolutionary programming (EP) by analysis and comparison of their most important constituents (i.e. representations, variation operators, reproduction, and selection mechanism). Finally, we give a brief overview on the manifold of application domains, although this necessarily must remain incomplete     

Maximum Availability Server Selection Policy for Efficient and Reliable Session Control Systems

There has been a rapid growth of services based on session control. Session-based services comprise multimedia conferences, Internet telephone calls, instant messaging, and similar applications consisting of one or more media types such as audio and video. Deployment examples include session control services as part of the IP multimedia subsystem (IMS), in the third-generation mobile networks. High service dependability in session control systems is achieved by introducing redundancy, e.g., through reliable server pooling (RSerPool) or clustering. Namely, session control servers are multiplied in server sets. Performance of such replicated session control servers is quantified by transaction control time. Thus, reducing transaction control time enhances performance. Server selection policies (SSP) are crucial in achieving this goal. The maximum availability (MA) SSP is proposed to improve session control performance in scenarios with server and communication failures. Based on a status vector, MA aims at maximizing the probability of successful transaction with the current transmission, thereby minimizing the average number of attempted servers until success. MA is applicable in a broad range of IP-based systems and services, and it is independent of the fault-tolerant platform. A simple protocol extension is proposed in order to integrate MA into the RSerPool fault-tolerant architecture. In addition, an analytic model is derived based on certain system model assumptions. Analytic and simulation results show that transaction control time is considerably reduced with MA as opposed to when using traditional round robin