Simulation of trader and mediator instances in large mobile distributed systems

The present paper deals with the integration of mobile clients in the client-server connections of large heterogeneous distributed systems. Main emphasis lies on a simulative performance evaluation of such architectures. In the underlying scenario mobile clients request a service of a suitable server which is chosen by a trader. Then the mobile clients send input data to and receive result data back from the server where the input and result data is assumed to be of large volume. Because of the much lower QoS-parameters in the mobile region compared with die fixed network, mediators are introduced as additional instances of the fixed network offering mediation, error removal and security services for the data transmissions of the mobile clients. A detailed discrete simulation model (sequential-parallel queueing network) is introduced which imitates the transaction flow in the architecture inclusive the functionality of the mediators, the trader and the other instances. A simulative performance evaluation shows that the mediators fulfil all tasks in an effective way and with a low overhead. Furthermore, a new trader service for the optimal selection of mediator and server interfaces is briefly discussed and evaluated by simulation.