The performance of the Message Passing Interface collective communication algorithms is a critical issue widely discussed in both academia and industry. In order to achieve and maintain high performance in the MPI implementations even in regard to random system behavior, the collective operations must be adapted to both the cluster platform and the workload of the user program. In this paper we propose the DYN Alltoall, a dynamic version of the traditional MPI Alltoall implementation, which is based on performance predictions derived from P-LogP model. The experiments which were performed on clusters equipped with different interconnect networks, Infiniband and Gigabit Ethernet, produced encouraging results with negligible overhead to find the most appropriate algorithm. In most cases, the dynamic Alltoall largely outperforms the traditional MPI implementations on different platforms.